Table 1.27-1 Allowable Bond Stresses of Anchor Bolt

Type of steel bar

28 Days design standard strength of concrete (kgf/cm2)

Unit weight of concrete before it hardens should be 2.3tf/m³.

Allowable stresses of concrete taking account of effects by earthquakes, wind and temporary loads are given below:

1. In case that temperature change and dried shrinkage are considered, the above allowable stress may be increased up to 1.15 times.

2. In case that an earthquake or wind effect is considered, the above al­lowable stress may be increased up to 1.5 times.

3. In case that effects by temperature change, dried shrinkage, and earth­quake are considered, the above allowable stress may be increased up to 1.65 times.

4. In case that a temporary load or a rare load is considered, the allow­able stress should not exceed twice the above allowable stress.

Article 28. Movable Part of Support

A movable part of a support shall be of structure enabling a steel pen­stock to move safely and smoothly while it is expanded.

Description:

Example of rocker bearing

Example of roller bearing

Ring girder

Pinch plate Sole plate - Shoe

Example of slide bearing

Fig. 1.28-1 Bearing Type of Various Bearings

A type of support of penstocks is divided into a saddle support type and a ring support type. A saddle support type is liable to be used for a relatively small diameter penstock and a ring support type for a rela-' tively large diameter penstock. Types of support and bearing for the pen-’ stock should be decided taking account of importance, safety, and economy of the steel penstock.

For a saddle support type, there are a concrete saddle and a steel sad­dle. A steel saddle is used as a special support in tunnels or dams. There are somelypes of bearing of concrete saddles, such as the one to be sup­ported in direct contact with concrete, to be applied with a supplemental lubricant such as graphite and asbestos on the upper surface of the con­crete, to fix a plate to a bearing concrete with more than a 3mm thick steel plate and to be applied with some lubricant on the upper surface of the plate.

A saddle support type, compared with a ring support type, has a larger circumferential pipe displacement at a support, and thus vibration of a pipe is likely to be generated because of the pressure fluctuation produced at a turbine. Consequently, care must be taken to a saddle bearing having a relatively thin plate in comparison with a pipe’s diameter. A rocker bear­ing, a roller bearing or a slide bearing, etc., are employed for a ring sup­port type. (See Fig. 1.28-1)

A supporting method for penstocks should be of a structure to minimize the pipe’s deformation at a support, and to enable the pipe to move freely against its axial expansion due to the temperature change and an internal pressure. As shown in Table 1.19-1, Article 19., this Chapter, as-for fric­tion, a ring support type bearing is superior in an axial move.

As for bearings of a concrete saddle support, the use of a steel plate or a slide supplement material is recommended.

A pipe’s deformation at a support gets maximized during water filling and discharging. Extreme care should be exercised to a saddle support. A 120° supporting method is common to a saddle support. '

A penstock at a saddle support is subject to a circumferential bending moment in addition to an internal pressure. A circumferential bending moment gets maximized when the water is just filled, and its values can be determined from Fig. 1.28-2. Max. bending moment generates at a point “A”, and it reaches M = 0.0528QjR in case of 0 = 120°.

Support

According to Arriaga’s analysis, the .stress due to a bending moment at a saddle support decreases to some extent as the internal pressure in­creases, and so a stress due to a bending moment is not required to be added to a stress due to the internal pressure in case of a penstock sub­jected to an internal pressure. But, the internal pressure in a penstock with thin wall close to the head tank is low, and thus it is desirable to pay such attention as taking a small j3.

It is permissible to increase the allowable stress up to 1.5 times as far as the stress due to a bending moment caused by water filling is concerned. It is said that, with no stiffener around a saddle, a pipe shell plate, either equal to the pipe’s diameter or 1/2 the support interval, whichever is the smaller, works effectively to this bending moment on each side from the center of the saddle. Stiffeners should be installed around the saddle when just the pipe shell cannot resist the bending moment. In this case, the cross section working effectively to this bending moment should be the area of the afore-mentioned pipe shell plate plus the stiffener’s cross section.

Article 29. Ring Girder

1. A ring girder shall be so designed as to be safe against the internal pres­sure, self weight of pipe, water weight in pipe, temperature change,

. earthquake, and wind pressure.

2. Earthquake considered in design shall be assumed to work horizon­tally and its horizontal seismic coefficient shall not be less than 0.1.

3 . The wind pressure considered in design shall be assumed to work horizontally to a right angle projected face of the penstock, and its pres­sure shall not be less than 0.15tf/m^{5 6}.

4. The allowable stress used in design for a ring girder shall be the one listed in Table 1.12-1, Article 12., this Chapter in case that temperature change, earthquake, or wind pressure are not considered. The allow­able stress may be increased up to 1.5 times in case the above is con­sidered. _

Description:

1. Contrary to a saddle support type penstock of which circumferential stress is only considered, an axial stress is also considered for the pen- . stock of a ring girder support type. Thus it is possible to design a pen­stock as a girder to support its weight, and to take a relatively long supporting span.

Stresses in the above become as follows:

FOR 1

Chapter 1 STEEL PENSTOCKS 7

Section 1 General 7

Section 2 Design 4

Description, 19

2. Material and Allowable Stress 31

Description: 31

3. Pressure Lining Part 46

P‘=²-^59£-7&^: . 48

(cwlT+U^V.- 51

Description: 56

4. Attachment Installations 91

Description: 97

Section 3 Manufacture 101

Section 4 Installation 107

Section 5 Maintenance 119

Section 6 Anchor Block and Support 127

Chapter 2 HYDRAULIC GATE 137

Section 2 Outline of Design 153

2. Gate Leaf, Gate. Guide and Anchorage 162

Description: 196

Description: 201

3. Gate Hoist 201

Description: 202

Description: 205

Description: 206

Description: 206

Description: 210

Section 3 Design Particulars 213

1. Fixed Wheel Gate 213

Description: 223

—~^p 223

F=p._r(q + Pb)Ll 224

2. Radial Gate 225

Description: 225

Description: 226

Description: • ¹ 228

3. Long Span Gate 229

Description: 221

4. Bottom Hinge Flap Gate 222

Description: 222

Description: 224

5. High Pressure Gates and Valves 226

Description: 226

Description: 229

6. Selective Water Withdrawal Equipment and Surface Water Withdrawal Equipment 235

Description: 235

Description: 236

Description: 236

7. Trash Rack 240

Description: 241

Section 4 Manufacture 245

Description: * 245

Description: 245

Section 5 Installation 246

Description: ' ' ^: ''f. .1.... ' .a? a ' 247

Description: 247

Description: 248

Description: 254

Description: 256

Section 6 Inspection 257

Description: 258

Section 7 Maintenance 259

Description: 259

Description: 259

Description: 259

Description: 260

Description:. - 260

Description: 261

Description: 261

Description: 262

Description: 262

. Chapter 3 STEEL STRUCTURE 269

Description: 269

Description: 269

Section 2 Design 269

Description: 270

Description: 270

Description: 270

Description: - ■ ' 271

Description: 273

Chapter 4 WELDING 274

Section 1 General 274

Description: 274

Description: - 277

Description: 292

Section 2 Welded Joint 296

Description: 296

Description: 289

Description: 293

Description: ".'A • 295

Description: 297

Description: 298

Description: ^; ■ 300

Section 3 Welding Procedure 302

Description: 302

Description: 305

Description: 307

Description: 308

Description: 309

Description: 309

Description: 311

Description: 313

Description: 313

f 313

Description: 315

Description: 323

Section 4 Heat Treatment 327

Section 5 Test and Inspections 334

» Description: 335

Description: 336

Chapters 340

RIVETED, HIGH STRENGTH BOLTED AND BOLTED CONNECTIONS 340

Section 1 General 340

19. Description: 358

79. Description: Omitted 352

81. Description: Omitted 352

84. Description: Omitted 352

111. Description: 354

193. Description: 359

198. . Section 4 Bolted Connections 361

217. Chapter 6 SAFETY AND SANITATION 365

whereas,

EV qr_m) R' ^q jr_mt

£\ (2+p)L'

2Q ) ^{+ 4}<7^rm²

where p: Poisson’s ratio = 0.3

Fig.1.29-1 Ring’s Cross Section with Water Fully Filled

X

2K

qr_m

C=

where A : Sectional area of combined rings (m²)

I: Moment of inertia about Y-Y axis (m⁴)

L : Length of one span (m)

M: Bending moment of ring (tf-m)

Nt Tensile force of ring section due to internal pressure (tf) Pt Water pressure (tf/m²)

Q_s t Reaction force by self weight of pipe acting on a ring gir­der (tf)

Q t Reaction force by both self weight of pipe and water weight (tf)

St Shearing force of ring girder in a radius direction (tf) T: Tensile force of ring except N (tf)

K_x to K₆1 Coefficients (See Table 1.29-1)

Table 1.29-1 Coefficients with Water Fully Filled in the Pipe

e ■	T = Q(X, + BKJ		M = Q{RKZ + XK.)		S = Q{K} + ckj-
					K,	*6
0°	- .238732	+ .318310	+ .011267	-.068310	0	0
15°	-.241384	+ .307464	+ .008618	- .057464	+ .019651	+.082385
30°	-.248415	+.275664	+ .001585	- .025665	+ .032380	+ .159155
45°	- .257198	+ .225079	-.007198	+ .024921	+ .032117	+ .225079
60°	- .263704	+ .159155	-.013704	+ .090845	+ .014417	+ .275664*
75° .	- .263023	+.082385	-.013023	+ .167616	- .022945	+ .307463
90° -	-.250000	0	0	+ .250000	- .079577	+ .318310
90° +	+ .250000	0	0	-.250000	- .079577	+ .318310
105°	+ .263023	- .082385	+ .013023	- .167616	- .022945	+ .307463
120°	+ .263704	-.159155	+ .013704	- .090845	+ .014417	+.275664
135°	+ .257198	-.225079	+ .007198	- .024921	+ .032117	+ .225079
150°	+ .248415	- .275664	-.001585	+.025665	+ .032380	+ .159155
165°	+ .241384	- .307464	-.008618	+.057464	+ .019651	+.082385
180°	+ .238732	-.318310	-.011267	+ .068310	0	0

+: Tension - : Compression

2) Earthquake occurrs with water fully filled iri the pipe

Circumferential sectional forces of a ring girder by seismic loads with water fully filled in the pipe can be determined from the following formulae: ^; < D

M = kQ (RJ^ + WK^

T = kQ + B1Q

S = kQ(K_s + CK<)

Stresses in the above become as

External edge stress of ring:'

Internal edge stress of ring:

follows:

(Tf = — +M— A I

2K\ rjy

- 1 +■

qr_m ) 4R

(2+QL'

4gr_m² .

where

1.285

^q~7W

v : Poisson’s ratio = 0.3

A : Sectional area of combined rings = t{b + \ .56'/r~t) + 2lt_r (m²)

L : Length of one span (m)

Fig. 1.29-2 Ring Cross Section when Earthquake Occurs

Whereas

Table 1.29-2 Factors when Earthquake Occurs

9	M = ArQCRX, +		T = kQHK, +		S = kQ[K} + CA'J
0°	0	0	0	0	+ .079577	+ .318310
15°	-.019651	- .064705	- .019651	- .082385	+.066082	+ .307464
• 30°	- .032380	-.125000	- .032380	-.159155	+.027249	+ .275664
45°	-.032119	-.176776	-.032119	- .225079	-.032119	+ .225079
60°	-.014417	-.216506	-.014417	-.275664	- .104549	+ .159155
• 75°	+.022946	-.241482	+.022946	- .307464	-.180639	+ .082385
90° -	+.079577	-.250000	+.079577	-.318310	- .250000	0
90° +	+.079577	+ .250000	+ .079577	-.318310	— .750000	0
105°	+.022946	+ .241482	+.022946	- .307464	-.663601	+ .082385
120°	-.014417	+ .216506	- .014417	- .275664	- .537561	+ .159155
135°	-.032119	+ .176776	-.032119	- .225079	-.385671	+ .225079
150°	- .032380	+ .125000	- .032380	-.159155-	-.222751	+.275664
160°	-.019651	+.064705	-.019651	- .082385	- .063328	+ .307464
180°	0	0	0	0	+ .079577	+ .318310
195°	+ .019651	- .064705	+ .019651	+.082385	+.066082	+ .307464
210°	+.032380	-.125000	+ .032380	+ .159155	+ .027249	+ .275664
225°	+ .032119	-.176776	+ .032119	+ .225079	-.032119	+ .225079
240°	+ .014417	-.216506	+.014417	+ .275664	-.104549	+ .159155
255®	- .022946	- .241482	- .022946	+.307464	-.180639	+ .082385
270°-	- .079577	-.250000	- .079577	+ .318310	-.250000	0
270° +	- .079577	+ .250000	- .079577	+ .318310	+ .250000	0
285°	- .022946	+ .241482	- .022946	+ .307464	+.302324	+ .082385
300°	+ .014417	+ .216506	+ .014417	+ .275664	+ .328463	+ .159155
315°	+ .032119	+ .176776	+ .032119	+ .225079	+ .321433	+ .225079
330°	+.032380	+ .125000	+.032380	+ .159153	+ .277249	+ .275664
345°	+.019651	+ .064705	+ .019651	+ .082385	+ .194491	+ .307464
360°	0	0	0	0 ,	+ .079577	+ .318310

M: Bending moment of ring when earthquake occurs (tf-m) Q_t: Reaction.force by self weight of pipe acting on a ring girder (tf)

Q ’ Reaction force by both self weight of pipe and water weight acting on a ring girder (tf)

k: Horizontal seismic coefficient

S: Shearing force of a ring girder in its radius direction (tf) T. Tensile force of a ring girder when earthquake occurs (tf) to K₆: Coefficient (see Table 1.29-2)

ASIA . . ■ ..... , ■

From these two group calculation formulae, it is possible to make cal-, culation for self weight of pipe, water weight in pipe, internal pres­sure, earthquake and wind pressure.

In case of a supporting angle of 120°, it is possible to calculate based on the above. -

.It should be noted that a careful design.be made taking the tempera­ture change due to the sunshine in particular into consideration as well as ambient temperature change when the pipe is empty. Uneven tem­perature distribution of the pipe generates a big thrust and moment at a bearing, and thus a thorough examination is required for this, together with overturning and sliding stability against earthquake and wind pressures.

2. . As for earthquake, a force P acting on a structure with weight W (self

weight of pipe and water weight) and horizontal seismic coefficient k, is expressed by P = kW.

Values of k should be those suitable for the site to be constructed, dependent upon regions and grounds.

In the designing of structures, generally, if correction of a horizon­tal seismic coefficient is made to regions and grounds, k becomes 0.24 (a soft ground in a region where a big earthquake has ever happened) to 0.1 (a good ground in a region where no earthquake has ever hap­pened). Since steel penstocks are installed in a good ground, the value 0.10 to 0.15 is commonly employed as a horizontal seismic coefficient.

2. . The wind pressure acting on a pipe line horizontally and perpendicu­

larly to a pipe line should be considered. Wind pressure Q_w to the pen­stock’s perpendicularly projected face is given from the following formula:

f

Qw =

where Q_w: Wind pressure per axial unit length (tf/m)

A : Perpendicularly projected area per axial unit length (m²/m)

C_D: Drag coefficient in relation to shapes of objects (0.8 for a cylinder)

q : Air density = 0.000125 (ts²/m⁴) u : Wind velocity (m/s)

Accordingly, approximately 0.15 tf/m² for max. wind velocity 55m/s.

2. . An increase in allowable stress is recognized in each case when taking account of the temperature change (v/Hh empty penstocks), earthquake and wind pressure.

The above seldom happens or only temporarily if it happens, and so 50% increase in allowable stress i'^! -‘ipecified, -and this means that more than 1.5 safety factor against frncture is secured. For these con­ditions, a thorough design should be conducted not only from a struc­tural viewpoint but to concrete and aimhor bolts and so forth to secure the safety against sliding and overturning of the structure.

Section 3 Manufacture

Article 30. Processing of Shell Plate

1. . A shell plate shall be bent uniformly and carefully by a bending roller

or other machines.

2. . A hammer shall not be used for edge bending.

Description:

1 . A bending roller or a bending press should be used to bend a steel plate to manufacture a shell plate. A steel plate is usually cold processed, but a hot process by heating a steel plate is also permissible in case that a plate is so thick that a bending roller or press is incapable of dealing with the plate. But a hot processing system should not be employed for the steel plate of which material is changed by heating like a heat treated steel plate.

Fig. 1.30-1 Bend Processing of Shell Plate by Bending Roller

2 . When using a tri-pyramid roller, both edges of a plate cannot be bent by the machine, and thus a bend processing should be made to approx­imately 30cm range of both edges in order to get the required arc shape. This processing is generally called “Edge Bending”, and this must not be done by hammering.

When using a pinch roller type machine as illustrated in Fig. 1.30-IB, it is possible to make an edge bending, and so it is not necessary to make it by bending press.

Edge bending greatly influences the roundness of a penstock after welded in any case, thus requiring a careful and precise execution.

Article 31. Fabrication

1. . A steel penstock shall be fabricated in a work shop or a field shop,

and shall be completed as a pipe section. Dimensions and shapes of a completed penstock shall be exactly in accordance with the design.

2. . As for branches and other deformed penstocks, when inconvenient to

complete as a pipe section in a work shop due to a transportation limit or some other reasons, a trial assembly in a shop shall be made so that dimensions and shapes are in accordance with the design.

Description:

A steel penstock should be processed and fabricated in a work shop or a field shop as a pipe section, and the completed penstock should be transported to the installing site. The length of a pipe section is generally 6m in case of a straight pipe.

In case that a pipe’s size and its weight exceed the transportation limits, manufacturing limits should be decided after investigating conditions of' transporting routes, and a penstock should be completed as large-sized as possible at a work shop.

In other words, the branches and other important deformed penstocks exceeding these dimensions and weights should be trial-assembled in a shop as a whole, and then the dimensions and shapes should be inspected. There­after, they should be divided into large-sized sections as much as possible as stated above, and then each section completed should be transported.

In a trial assembly, the following should be inspected: a. diameter of penstock b. length of penstock c. bending angle for deformed penstock d. angle of penstock end plane to its axis e. weld groove shape, etc.

For a straight penstock, circumferential length, plate width, radius of curvature, groove dimensions, etc., should be checked, and a trial assembly may be omitted.

The main purpose of a trial assembly is to fabricate and complete the penstock exactly as designed without reworking at site or in a field shop, and thus it is necessary^;.to place match marks for fabrication and marks for'installation on the pipes after their inspection completed during a trial assembly. At site or in a field shop, assembly and welding should be ex­ecuted according to these marks.

Article 32. Tolerance for Circumferential Length

The manufacturing tolerance for the circumferential length of a pres­sure lining part shall not'be more than ± 0.25% of the design length.

Description:

There are two ways to determine the tolerance for a penstock’s section­al dimension: to determine the allowable value for out. of roundness by measuring an internal diameter of a penstock, and to determine the toler­ance for a circumferential length by measuring it.

As for a steel penstock, its out of roundness varies with its supporting method because the penstock is a thin walled tube, and a deflection gener­ates in an actual measurement as the penstock is measured while being placed horizontally. Thus, it is difficult to strictly stipulate. Accordingly, in order to secure the roundness to such an extent as not to have any trouble for field welding, the roundness should only be corrected by-fixing jigs* inside pipe and the tolerance for the circumferential length should be re­gulated instead.

The tolerance for a steel plate thickness influences the circumferential length. Since the thickness tolerance is the value shown in Article 9., this Chapter, it is necessary to take this value into account for the tolerance of the circumferential length.

Approximately 2mm of contraction by weld is unavoidable as shown in Fig. 1.32-1. Cutting errors of a steel plate, and circumferential errors due to a cold bending process by a roller or press are generated. The cir­cumferential error/frequency curve is shown in Fig. 1.32-2. This circum­ferential error is the result of these cumulative errors. As shown in this figure, it is not practically harmful even if a circumferential error of ap­proximately ± 4 to 6mm is permitted. Thus, it is specified to set the manufacturing tolerance for a circumferential length at ± 0.25% of the design length taking allowance into consideration.

Furthermore, offset for the joint of adjacent pipes should satisfy the regulation of Article 28., Chapter 4.

Fig. 1.32-2 Example of Circumferential

Length Error/Frequency Curve for Welded Penstocks

Fig. 1.32-1 Differences in ■w ’Circumferential Length

Between Tack-Welded and

Completely Welded

Article 33. Hydraulic Test

A hydraulic test, or a nondestructive test such as a radiographic test shall be executed for a pressure lining part in a shop or at site so as to ensure that there exists no unsoundness.

Description: o_r .. I.r <« <■ ■

A hydraulic test or a nondestructive test such as a radiographic test in place of the hydraulic test should be executed for a steel penstock before installation in a shop, or at site after installation so as to ensure that there exists no unsoundness.

(v) <_ vwxlce, AJAC-

A hydraulic test is executed to verify the design and to prove effective­ness and safety of the steel plates and welded joints, as well as to relieve mechanical stresses to some extent.

In recent years, with the quality improvements of steel materials, weld­ing and nondestructive inspection tests have made remarkable progress and their reliability has been increased, and thus as for a straight pen­stock and a deformed penstock which ensures a thorough analytic confir­mation', the safety is confirmed by executing a nondestructive test with a hydraulic test omitted in many cases. .

A hydraulic test is executed either in a shop as a pipe section or at site after installation as a completed pipe.

Since a hydraulic test for a pipe section requires much (time and cost|. it is sometimes convenient to substitute a hydraulic test as a completed pipe at site after installation in view of progress of work and economy. For a hydraulic test of a completed pipe after installation, an end plate is prepared for both ends of a pipe, and then water is filled inside the pipe and it is pressurized by a pump.

The hydraulic test pressure should be more than 130% of the design internal pressure in a shop, and more than 110% of the design internal pressure at sitejlter-iostallation, and it is standardized that its duration should last more than 10 minutes. This value is derived from actual results in Japan as well as examples in Europe and USA. The reason lor setting the test hydraulic pressure at site after installation at.jjjore than 110% • is that keeping 130% of the design internal pressure in the whole pipeline is difficult because of changes in waterhead and hydrostatic pressure water hammering pressure in relation to the design waterhead and hydrostatic pressure. Thus it is set at more than 110%, considering that a test is ex­ecuted by dividing the pipeline into several sections depending on the site condition.

Fine, special study and examinations should be made because an internal pressure acts to an anchor block in addition to the design pressure, and the continuity of pipeline is disrupted with an end plate fixed, and so the thrust other than design conditions acts. It should especially be noted that some cracks were generated in an anchor block concrete when a field hydraulic test was conducted without making the above review.

An end plate is generally of elliptical, standard dished, or semi-spheric shapes, and a flat plate is used in case of a small diameter pipe. An end plate should be in accordance with JIS B8243 (1977) Construction of Pres­sure Vessels.

For branches in particular, the following various stresses are com­pounded and cannot be grasped in detail:

1. Stress concentration and local stress generated from discontinuity in shape due to connection with reinforcement girders, etc.

2. Additional stress generated by an irregular radius of curvature due to angular distortion by assembly and weld.

3. Stress generated from a supporting method during a hydraulic test. Moreover, there exists the portion of which distortion is restrained, and

so a brittle fracture may take place in the steel material having a high yield­ing ratio. Consequently, when planning a hydraulic test for branches of a high tensile steel having a high yielding ratio, the test should be care­fully executed by making a detailed plan on test pressures, early notice of danger by a stress measurement during the test.

There are some examples which regulate the test pressure at 110°7o of the design internal pressure irrespective of in shop or at site, for branches having a very high water pressure, which arc located just upstream of a" power staupn, considering that high tensile steels having a high yielding ratio are often used as well as safety during the test.

A nondestructive test without a hydraulic test should basically be’in ac­cordance with Article 32., Chapter 4. However, it is desirable that an in- spection is conducted by expanding the scope of the nondestructive test for the branches having complicated structure or made of a high tensile steel which requires special attention to the brittle fracture.

M? *

Section 4 Installation

Article 34. Handling

Special attention shall be exercised in handling steel penstocks so as not to produce any deformation or damage in the process of transportation in manufacture and installation.

Description:

A power station is normally located at a remote place difficult of ac­cess, and transportation conditions are poor in many cases. In addition, on the site, exposed penstocks are installed on a sharp mountain slope or embedded penstocks are carried in passing a narrow construction road. It is common that the transportation conditions from a penstock yard on » the site to an installation point are poor. Therefore, special care should be taken in handling penstocks so as not to give any deformation or damage to the penstocks in the process of transportation in manufacture and installation, by using proper jigs for a large diameter penstock.

Fig. 1.34-1 Example of Jig for Prevention of Penstock Deformation

It is desirable that the penstocks are transported as large-sized as possi­ble so as to reduce field welding. A straight penstock is normally carried in as a pipe section with 6m in length, and for a larger diameter penstock as a unit section with 3m in length or a half segment pipe.

For field transportation, a trailer, cable crane or inclined track, etc., are used.

Before installation, a thorough inspection should be made lor installa­tion equipment so that pipes may not fall onto the ground due to the wire cut off while carrying them with a cable in the process of installation at site, or so that a pipe may not slip down along the route while installing with an inclined track.

Article 35. Installation in General

A steel penstock shall be installed exactly so that its position and shape are in compliance with the design.

Description-.

In installing the penstocks, the penstock center line and its height should be marked precisely on the neighboring structures as reference points, and then centering should be conducted based on these references. First, a bend „ pipe is installed and fixed, and then for an exposed pipeline, pipes are installed upstream in case that an expansion joint is just downstream of an anchor block or both upstream and downstream in case that an ex­pansion joint is in the middle of two anchor blocks. For an embedded pipes are installed in the direction from downstream to upstream in view of the concrete placing. The roundness should be kept by inserting jigs or beams into a pipe when installing a thin walled tube because of its siza­ble deformation by'its self weight.

A pipe section after centering should be tack-welded keeping an accurate groove dimension from the preceded pipe, and then a permanent welding should be made. It is desirable that permanent welding is made at sym­metrical places about the pipe center on both sides of the pipe at the same time. It should be noted that centering may be incorrect due to the weld­ing contraction if this sequence is improper.

In installing, the final adjustment for the length between.anchor blocks should be made with an expansion joint. When a distance between an­chor blocks is excessive, a pipe having an allowance to the designed length is prepared <and is cut into a required length at site in some cases. This pipe is called an adjusting pipe. With no expansion joints between fixed blocks, adjustment is made by cutting a pipe, of which joint is preferred to be welded at a designed standard temperature by using a lap joint having a small axial contraction as is shown in Fig. 1.35-1.

I... _J

All round field joint -p-®

- . Fig. 1.35-1 Example of Lap Welded Joint

A connecting work of the penstock’s end to a turbine or a turbine’s main valve is often a working scope on the side of a steel penstock. In this case, it is common that a turbine or its main valve has already been installed, and upstream penstocks have already been fixed by anchor blocks, etc. Accordingly, in order to connect these two fixed objects, some measures shall be adopted which are capable of absorbing the discrepan­cy in axial line between these objects as well as the difference in length from the designed dimension. The former can be absorbed by deflecting the last two or three pipes, and the latter by cutting the pipe.

A loose flange is commonly used to connect the last portion of the pipe to a turbine or its main valve. The final circumferential joint is usually made by welding which is less contracted and strained, and thus the displacement of an end of pipes after installation is absorbed within an allowable amount of a loose flange.

For a big capacity turbine, its main valve is in many cases fixed to the end pipe of a steel penstock and a loose flange is installed downstream of the valve. In this case, the axial thrust generated when the valve is closed is supported by a steel penstock. The axial stress generated in a pipe shell is 1/2 the circumferential stress, and the above stated connecting method works with no problem. It is necessary that this axial force is properly transmitted to an anchor block and that an anchor block is also reinforced, thus being capable of resisting the axial force.

For the final joint of an end pipe, a riveted joint has long been used so far, but has not been employed of late because of the extensive use of high tensile steels for the pipe shell plate, increasing plate thickness, difficulty in securing riveted joint strength, and inappropriateness of caulk­ing to high tensile steels.

Extreme care should be exercised in installing embedded pipes in a tun­nel, paying much attention to ventilation and scaffold in particular in view of the narrow working space condition. Water-proof and drop-proof meas­ures arc also required.

A penstock is installed by filling concrete with an interval of approxi­mately 12m, depending on a tunnel’s slope.

While filling concrete, a buoyancy and a transverse force act on the pipe, and thus the pipe should be sufficiently fixed so as not to move.

Article 36. Consideration of Temperature during Installation

1. An expansion joint shall be installed so as not to cause trouble with expansion taking account of temperatures of a steel penstock during installation.

2. As for a steel penstock of a ring girder supporting type, a bearing such as rockers shall be installed at the required position taking the penstock’s temperature during installation into consideration, and moving the pen­stock’s end during installation shall be considered when the direct sun­shine influences much.

Description: ,

1. As stated about the temperature of exposed steel penstocks in Descrip­tion of Article 24., this Chapter, the maximum temperature of an empty penstock in direct sunshine goes as high as 60°C and the range of tem­perature change goes as far as 70 to 80°C, and thus it should be noted in installing the exposed penstocks that an expansion allowance during installation should have a correct length designed for temperature dur­ing installation, thus resulting in no trouble in expansion after installa­tion. Accordingly, when a penstock is in direct sunshine at the last stage of installing the expansion joint, it is necessary to determine the ex­pansion length in accordance with the temperature of the penstock by using a surface temperature measuring device.

2. As for a steel penstock of a ring girder supporting type, a bearing such

as rockers should be adjusted in the correct position taking, the pen­stock temperature during installation into consideration, so that the bearing can make an appropriate and smooth bearing within the designed range of temperature change. When the influence by direct sunshine is excessive e.g. strong sunshine on one side and shade on the other side, itjs difficult to maintain the pipe’s straight alignment dur­ing installation.” • ' ._;

The temperature difference generates a large moment at a support, which gets excessive in a ring girder supporting type with a long span. When installed with a cantilever beam method, a large displacement

is generated at the free end of the cantilever beam between day and _;. * night, and thus stability against the moment at the rocker bearing is_t required. An example of a computation formula for a moment at a ? fixed end when expansion and displacement of a pipe in direct sun- ^{; w} shine are restrained is shown in Fig. 1.36-1 for reference: ,

. With the assumption that the temperature difference between the direct sunshine side and the opposite side is FC, the temperature gra­dient is straight, and the pipe is not restrained by bearings etc., the elon-^:v gation 3 for the micro length dx becomes:

6 = AT* a *dx

where a: Coefficient of linear expansion of steel 1.2 x 10^-5 (°C)

8 AT*a , dv~D^ D

dy = (L-x)d<p

_fT . AT*a , AT* a L¹ (L - x)—-— dx=—-— • —

J ' D	D 2
If this deflection is	restrained, the temperature stress
8E E ± —± —AT* 2dx 2	a

is generated, and the bending moment at a fixed end becomes as follows; _ El

M=——~AT*a

Article 37. Longitudinal Joint

A longitudinal joint shall not be in line with an adjacent longitudinal joint.

Description’.

It is necessary to decide the arrangement of longitudinal joints and weld­ing sequences so as to minimize deformation and residual stress, when each pipe shell and pipe section are welded in shop and at site. If longitu­dinal joints were in line, a cross-shaped joint would take place on each pipe shell and the deformation and residual stress caused by welding would concentrate on a longitudinal joint line, and thus longitudinal joints in alignment should be avoided. In Fig. 1.37-1 is illustrated an arrangement of longitudinal joints on pipe shell sections. (See Article 7., Chapter 4)

Circumferential joint (shop weld) Circumferential joint (field weld)

Longitudinal joint (shop weld)

Fig. 1.37-1 Example of Arrangement of Longitudinal Joints

Article 38. Coating

1. . A steel penstock shall be coated in accordance with the specification

suitable for the installation environment and shall ensure enough dur­ability.

2. . Prior to coating, rust, oil, grease and dust on the surface of a steel pen­

stock shall be carefully removed and cleaned, and then the surface shall be thoroughly dried.

It is desirable that alkaline fume deposited on a weld line or its ad­jacent place by a low hydrogen type electrode be removed.

3. . Coating shall be avoided in an excessive hot or cold temperature or

when humidity is high, or when a rainfall or snowfall may be forecast before the paint gets dried, or other cases, e_;g. when coating can not be made properly.

Description'.

1. . Generally, paints arc applied to a steel penstock to prevent it from cor­rosion. There are a variety of paints, of which selection is important.

Effect of coating is. greatly influenced not only by the properties of paints themselves but also by surface preparation and coating work con­ditions. ■ ^b

Internal surface of a steel penstock is always under hydraulic pres­sure and very severe conditions in view of corrosion caused by water quality, velocity of flow, and sands and soils flowing in. Once water is- filled in the penstock, an opportunity for recoating arid repair is sel­dom and, if any, its work is very dangerous and difficult. In addition, it is also hard to get a dry enough condition. Exhaustion and removal of generating gases are difficult if synthetic resin type paints are ap­plied. Accordingly, coating should be made so as to ensure perfect dur­ability as much as possible from the outset.

An external surface is often wet by dew condensation due to the tem­perature difference between the water temperature inside the pipe and the ambient temperature, and damage to the coats is often seen at the underside of the pipe and at the portions in the poor sunshine in par­ticular. Thus, it is also required for an external surface to make a coat­ing with an excellent durability suitable for the environment, likewise the coating for an internal surface.

A large-scaled work increases its construction period, resulting in a longer period from the under coating in shop to the finish coating af­ter completion of installation. Careful consideration should be given to a prolonged interval between coats.

A rust preventing oil paint of water proof type was often applied • twice to the internal surface in the past, and its effect was not satisfac- tory because its life was considered only several years even if enough drying time was prqvided. In place of this, next came a heating type coal tar enamel, then a tar-epoxy synthetic resin coated at normal tem­perature has been widely used in recent years. Bituminous material from which these paints are made, has a low water absorbing capacity and water permeability, and has a high insulation resistance.

A heating type coal tar enamel might decrease its adhesiveness un­less amount of primer applied, dried time, and heating temperature of enamel were strictly controlled, and a centrifugal coating device was commonly used. This coal tar enamel, however, has been seldom used since 1960 when tar-epoxy paint was practically used.

Tar-epoxy synthetic paint is of amine type material combined with coal-tar and epoxy-resin and is a two fluid type of a curing reaction.

This resin paint, capable of making a very strong film, is superior in corrosion resistance. But it is absolutely necessary to pay attention to strict observance of a perfect blend and the volume ratio as well as the time control after blending.

Since hardening takes place by chemical reaction, this paint is sub­ject to the influence of temperature, and hardening is slowed below 7 to 10°C. But the paint has been put into practical use up to 5°C by. adding a hardening agent, and the resin paint recently developed ex­clusively for low temperatures can be used at -5 to 5°C. After a thorough study of paint properties, a suitable coating method should be selected.

When applied to multilayer coatings, tar epoxy-resin paint has such a defect as to easily cause a separation of the layer, and thus a careful coating is preferred after the influences by coating intervals and tem­peratures are fully confirmed beforehand. .•

Recently, a high build type paint has been developed, and a thick film can be obtained by coating just once with an airless spray, and thus the layer-separation probability has been decreased. The portion which was coated in shop and completely hardened should be of rough surface so as to increase adhesiveness in case that this portion should be coated at site.

Coating on an external surface should be studied by dividing into exposed pipes in open air, exposed pipes in tunnel, and embedded pipes in concrete.

For exposed pipes in atmospheric air, a finish color matching.their environment, and having a good atmospheric corrosion resisting property as well as a water resisting property is required.

If a long interval is predicted between shop coating and final coat­ing at site coating is performed in following manner, for instance, Example A: in shop, First coat, Lead type rust resisting paint in shop, Second coat, Phenolic type MIO paint

< at site, Third coat, Chlorinated rubber type paint Example B: in shop, First coat,_;. Non-bleed type tar-epoxy-resin type paint

in shop, Second coat, - Epoxy-resin Type MIO paint . at site, Third coat, . Chlorinated rubber type paint

As an example of manufacturing at a field shop, for the pipe coated with a high build type zinc-rich paint is transported to the site and the

chlorinated rubber type paint is applied to the pipe after installed.

For exposed pipes in tunnel, tar epoxy resin coating is commonly used as the-internal surface coating. Generally, coating is not applied to embedded pipes in concrete, but in case of a long period required from the completion of manufacture to installation, primer or cement milk is applied in some cases.

2. . Mill scale and rust on the surface of steel material should be completely removed before coating. If coated as they are, rust would be expanded, thus resulting in swell and separation, and paint films would come off together with mill scale. Sand blast or shot blast is usually employed to remove rust and mill scale.

It is necessary to apply paint after complete removal of grease and dust, and moisture as stated hereunder.

Coating materials of a low hydrogen type electrode used for welding a high tensile steel contain sodium oxide (Na₂O), potassium oxide (K₂O) and so on, and, after welding, they are reduced to be sodium hydroxide (NaOH), potassium hydroxide (KOH), which are of a strong alkali component (pH9-l 1), and then they are adhered around the weld­ed portion. These products, having a high solubility, get wet with high humidity. Then, if the dew condensation starts running, the painted part might be deteriorated. If coated on a wet steel surface the paint

■ adherence gets lowered.

In order to prevent such defect, it is desirable to remove the adhered alkali component by using phosphoric acid agent. But this may not be necessary if the steel surface is exposed long and washed with rain etc. Such a phenomenon takes place in case of lime-titania type, high cellu- lose type, and high titanium oxide type in addition to low hydrogen type, then showing an alkaline nature.

As its thickness increases, tar epoxy resin paint film increases its co­hesion during hardening, and the adherence between the steel surface and- the paint film tends to be lowered. As corrosion allowance-of the plate for various tanks in a ship has been considered, its film thickness is set at 0.35 to 0.4mm. Generally, it is considered enough that a film thickness is approximately three times the surface roughness. Thus, 0.4mm is considered to be a standard film thickness taking account of some additional safety to the above and coating unevenness.

Anyhow, it is essential to avoid such defects as pinholes, and for pin­hole test, an inspection with an electric discharge type detector shall be executed, of which voltage is standardized to be 400V per 0.1mm film thickness.

3. . When coating in hot weather, blisters or pinholes tend to be generated in the paint film, and when coating in cold weather the paint spreads poorly and the film thickness gets uneven, and a longer drying time is required. JIS specifies film drying at 20°C, and it is desirable to per­form coating at temperature between 10 and 25°C or up to 30°C at most.

An oil paint used for an overlap coating can only exert its effect provided each under coat, intermediate coat, and top coat is complete­ly dried. An overlap coating should not be made if an under layer paint film is dried insufficiently.

Surface treatment for steel to be coated is so important as stated be-“ fore, and the moisture not only prevents adhesion of the paint but also gathers rust within a short time. When the humidity in the atmospher- ■' ic air is high and temperature is low, thin layers or small drops of con­densed water are attached to the penstock surface, despite unseen, and so a coating should be performed only on dry day, and be avoided a rainy or cloudy day with a-high humidity and at night.

Weather, atmospheric temperatures, humidities, as well as tempera­tures and humidities inside the pipe at the time of coating will not only be the data to judge the effect of coating but also reference data to research the cause of troubje with the paint film later, and so it is desira­ble to record the data and preserve them.

Article 39. Protection of External Surface of Pipe Embedded Underground

When a steel penstock is embedded underground, a sufficient corro­sion resisting treatment shall be performed.

Description:

If a steel penstock is embedded underground without any protective measure on its surface, i.e. exposing its steel surface to the soil, or under a normal coated condition, the corrosion of the steel material is prompted by the seepage water and the organic components contained in the earth. Due to the difficulty in maintenance, a special method different from the one on the ground should be considered.

Corrosion resisting methods include:

£14; Coating by coal tar enamel or blown asphalt

Jute cloth, glass cloth, glass mat, vinylon cloth, etc., are used as protecting materials.

Paints are applied to the pipe after surface treatment and primer coat­ing while the pipe is rotating on a roller support, and a protecting ma­terial dipped with paint is spirally wrapped under uniform tension around the pipe.

In order to increase the film thickness, a protecting material folded up is wrapped double-folded or wrapped more than twice.

In executing an anti-corrosion work, it is important to give consider­ations to surface preparation of the steel, coating temperatures, dry­ing of protecting materials, ambient temperatures, humidity and so on.

JIS G3491 (1968) Asphalt Coating Method for Water Service Stegl Pipes and JIS G3492 (1968) Coal Tar Enamel Coating Method for Water Service Steel Pipes specify coating of water service steel pipes.

2. Coating by cement mortar or concrete

Coating with cement mortar as thick as about 2cm is available. The mortar is sprayed with a cement gun to an external surface of the pipe surrounded with a steel wire mesh. While rotating the pipe on a roller > support, the mortar is sprayed with a brash machine in some cases or the concrete is filled around the pipe in backfilling at site.

Article 40. Name Plate

A name plate shall be attached to a steel penstock, marking name of manufacturer, date of manufacture, maximum design waterhead, effec­tive waterhead (maximum discharge), length of pipeline (separately for branches), internal diameter (upper and lower parts), thickness (upper and lower parts), type of materials used and total weight.

Description:

A name plate is attached to refer to matters pertaining to a steel pen­stock in the future e.g. for repair, modification, accident etc., of a steel penstock.

A name plate is helpful in part to notify the persons working in a power station in view of maintenance, and thus it is desirable that the plate be attached around the lowest anchor block for exposed pipes, and at a con­spicuous place close to a conduit such as a penstock inspection gallery for embedded pipes.

It is preferred to use a corrosion resisting material for the name plate.

Article 41. Water Filling and Operation Test

After completion of installation, a watertight inspection for expansion joints, manholes, and field riveted joints shall be executed by means of a water filling test under a hydrostatic pressure, and an operation test shall be conducted to check the whole steel penstock including the water ham­mering pressure, and safety shall be confirmed.

Description-.

After the penstock is completely installed, its inside should be cleaned and checked, and then water is filled inside the penstock by using a water regulating gate or a bypass valve. Check the pipe for its function during and after water filling. Leakage is likely to take place through an expan­sion joint, manhole, flange joint and field riveted joint in particular, apd so if any leakage is found by making a careful watertight inspection, it is necessary to repair the packings for the expansion joint and the man­hole, to retighten the bolts, and to make caulking for a field riveted joint. (Refer to Chapter 5.)

After the pipe inspection under a hydrostatic pressure is over, it is neces­sary to check the air pipe or the air valve for their operations by discharg­ing the water with drain valve, etc.

After a water filling test under a hydrostatic pressure, the whole pipe* should be checked for normality including a hydraulic pressure rise and vibrations and safety should be confirmed under operation test of the pow­er station.

In a governor test, the rising pressure at a penstock end and in a tur­bine casing is measured. If this value exceeds the designed rising water­head of the penstock, the governor should be adjusted so that the rising hydraulic pressure of the pipe shall be. within the design condition. In ad­dition, in the governor test, it is desirable that the rising hydraulic pres­sure of the main part shall be measured as the case may be.

Section 5 Maintenance

Article 42. Prevention of Leakage

A leak from a riveted joint, bolt, packing or any other portions of the penstock shall immediately be repaired.

Description'.

Omitted.

Article 43. Maintenance of Expansion Joint

An expansion joint shall always be well-maintained so that a steel pen­stock can smoothly be expanded and contracted.

Description:

It is desirable to make an inspection at least once a year to grasp the actual situation of each joint concerning leakage, tightening conditions, etc., so that a steel penstock can smoothly be expanded and contracted.

The Packings are generally replaced at intervals of 5 to 10 years de­pending on the materials, shapes etc. of the packings. They are sometimes ’ replaced at longer intervals of 20 to 25 years for example on record.

Article 44. Maintenance of Air Pipe and Air Valve

Prior to drainage of water inside the steel penstock, functions of the air pipe and air valve shall be checked and the water should not be drained

- unless the functions are perfect.

f '

Description:

Malfunction of air pipe and air valve during draining may lead to back- ling of the steel penstock, and in fact many accidents happen due to this reason. In an attempt to drain the water of the steel penstock, the water discharge should not be done without ensuring the perfect functions of these items. In checking these items and discharging the,water, the fol­lowing should be noted:

1. . Special attention shall be paid on inspection and cleaning of the in­

sides of air pipes. A thorough comprehension of its functioning is re­quired to check that the air valve works properly.

2. . In winter special attention should be paid on checking the freezing of

an air valve, when draining from a steel penstock which has not been

in operation for a considerable period with water filled in it.

3. . In draining, the drain valve should be gradually opened, only after the normal functioning of the air pipe or air valve is confirmed through a trial draining using the drain valve installed at the bottom of the low­er portion of the steel penstock.

4. Even if soundness of an air pipe or air valve is ensured, the water should never be discharged by a pressure regulator.

Article 45. Maintenance of Movable Part of Support

A movable part of support shall always be well-maintained so that a steel penstock can smoothly move.

Description :

Omitted.

Article 46. Prevention of Vibration

When a steel penstock vibrates excessively in operation of power sta­tion and this may affect the operation, some measures to decrease the vibration shall be taken.

a

Description:

■s. Vibration of a steel penstock consists of a bending vibration of a pipe wall and a transverse vibration as a beam. When a momentary pressure variation takes place at a turbine and a draft tube, and its frequency coin­cides with the characteristic frequency of a steel penstock, there occurs resonance thus resulting in a noticeable vibration.

When the flatness of a pipe section with water fully filled is excessive, a noticeable section vibration takes place corresponding to the pressure oscillation. With an excessive vibration of a steel penstock, fatigue and stress corrosion etc. are likely to take place, and thus the reduction of the vibration is required.

In order to take measures to prevent vibration, first of all, it is neces­sary to examine what sort of vibration the steel penstock is producing, and to study the relation between the cause of the pressure change as a source of vibration and the steel penstock. Causes of generating the pres­sure change are as follows:

1. Revolution of the turbine

'2) Number of vanes of the runner

(3) Water vortex in the draft tube

In order to prevent the vibration, the best way is to eliminate the pres­sure fluctuation as a source of vibration by supplying air into the draft tube. When this is difficult and if resonance is a main cause, it is better to change the characteristic frequency of the steel penstock by increasing the stiffeners, and by increasing the anchor blocks and other means. If a section variation of a oval pipe is a cause, a section rigidity should be increased by providing or increasing the number of.stiffinessi

_ J •

Fig. 1.46-1 Example of Vibration Preventing Stiffeners

For fixing stiffeners to an existing pipe, it is enough- only to tighten '■ stiffeners having a proper cross section with bolts as illustrated in Fig. 1.46-1.

In order to calculate the predominant frequency of a steel penstock, the following formula is used, taking account of elasticity of the pipe shell, mass of water, and influence by internal pressure:

(n²-l)

where f: Characteristic frequency of steel penstock (s~‘)

E: Modulus of elasticity of steel = 2.1 x 10⁶ (kgf/cm²) g: Acceleration of gravity = 980 (cm/s²)

v: Poisson’s ratio of steel = 0.3

7: Specific gravity of steel = 7.85 x 10"⁵ (kgf/cm³)

r_m : Radius of plate thickness center (cm)

/: Fixing span of pipes (cm)

h : Pipe shell thickness (cm)

n : Number of mode in circumferential sections (2, 3, ....) k: Number of mode in axial modes (1, 2, 3 ....) a : kirr_m/l

0 : h²/]2r_m²

e = (water density/steekdensity) • v*-^-

h n

P: Internal pressure (kgf/cm²)

11 - 2 n -- 3

Bending mode

Circumferential mode

k - 1 k « 2 k 3

Axial mode

Fig. 1.46-2 Vibration Mode of Cylindrical Shell with No Reinforcement

4. A formula to calculate the bending stress of a pipe wall generated when fa fluctuating internal pressure Ap works on a oval pipe, is shown below:

• , 3Zi7 a-b [. f, t

2r² 2 50(a-b)J

200 / r V

where a: 1/2 major diameter of a oval pipe (cm)

b : 1/2 minor diameter of a oval pipe (cm) t: Pipe wall thickness (cm)

r : (a + b)/2 (cm)

E: Modulus of elasticity of steel = 2.1 x 10⁶ (kgf/cm²)

Ap : Fluctuating internal pressure (kgf/cm²)

The above formula is for a circular ring, but span effect should be con­sidered when the fixing interval is short compared with the pipe diameter.

The following formula is generally used for the amplitude and the bend­ing stress: •

M-tY-H*²-i)l h/

2(1 - i^)r- I \ I } J

where r: Radius Of pipe (cm)

r: Pipe wall thickness (cm)

/: Fixing interval (cm)

n : Mode of vibration

W: Half of the amplitude (cm)

E: Modulus of elasticity of steel = 2.1 x 10⁶ (kgf/cm²)

In case of I > r and n = 2, the above formula becomes as follows: -a”,;.'”-

Article 47. Consideration to Water Quality after Completion of the Penstock

When the pH value of the water inside the pipe has decreased to less than four because of change of a river basin, change in water quality at a source and other reasons after completion of a steel penstock, some ar­rangements to decrease the corrosion shall be provided.

Description:

Some corrosion preventive arrangements should be provided if pH of the water inside the pipe becomes below four because of change in water quality by intaking the water from a river having a low pH, a volcanic activity around a water source areaaer other reasons. For corrosion preven­tion arrangements, refer to the Description, Article 7., this Chapter.

Article 48. Check of Pipe Inside

Water inside the pipe of a steel penstock shall be drained as the case may be, and a check necessary for maintenance of a steel penstock shall be made.

Description:

Omitted

Article 49. Measurement of Shell Thickness

Shell thickness of a steel penstock decreases as years advance and thus shall be measured as the case may be.

Description:

Shell thickness of a steel penstock gradually decreases due to corrosion and wear and if the decrease exceeds the corrosion allowance, the thick­ness can- not meet the designed condition and thus the penstock will be subjected to critical situation. So the safety of the penstock should be se­cured by making an investigation of the shell thickness and by .making repair or modification of critical portions.

There are various methods to measure the shell thickness of a steel pen­stock and those commonly used today are:

1. by an ultrasonic shell thickness measurement device

2. by modelling

3. by drill boring

4. by cutting off a test piece

For the method (1), two ways i.e. by reflection and resonance are avail­able, but the former one seems to be used more frequently in recent years. In either way, no suspenion of water flow in the whole pipeline is required and the operation of the device is easy, but sampling measurements cause some troubles by overlooking local corrosion and the measurement of the portion where a wavy corrosion is generated may become uncertain.

In using a measurement device, it is necessary to make a calibration by using the same thickness plate as the object to be measured. As for' ;.-K method (2), a plaster, resin-molding material, etc., are used to make the, gj model concerned. Methods (3) and (4) are the most accurate ones, but a thorough study is required for the material of parent metal and residual.z^a^- ...stress, etc., to repair the portions where a boring was made or.a test piece_;

was taken out/n.v-/ - h: b-

As for method (4), the piece cut off from the pipe itself is measured, . .■ and so it is seldom to cut the pipe only for the thickness measurement. . In many cases, the piece cut off for a material test is used for this purpose. ~ ,

Usually, the shell thickness is measured as a primary check with an ultra- - - sonic plate thickness measurement device, which requires no suspension~ of water flow and is executed easily and then the necessary portion is exa- .• mined by boring or sampling as a detailed check. . i;

•*

Article 50. Repair or Replacement

Immediate repair or replacement shall be made if decrease in a shell thickness, deterioration of material, decrease in a joint efficiency, etc., of a steel penstock are recognized as excessive.

.Description:

Fig. 1.50-1 - Concentration Stress Generated at a Concave of Steel Plate

'--•Ml

It is reported that an amount of annual corrosion is approximately 0.02mm/year. This report is based on the result of measurement of shell thickness of steel penstocks at 47 places by gravimetric method. The meas­ured penstocks were constructed between 1910 and 1953, and have been used without fluctuation and were not constructed in places having a high acid water and much flowing sands.

As for the above penstocks investigated, there exist some differences *' and uncertainties in circumstances, materials, coatings and repair histo­ries, and this figure cannot be directly applied to the present penstocks from a point of view of the recent improvement of materials, qualities and methods of coating, but can be of possible reference to the amount of corrosion.

In order to establish the perfect maintenance, defective portions of a steel penstock as stated below should immediately be repaired or replaced:

1. As a result of measurement of the shell thickness, an excessive decrease in thickness due to corrosion or wear is recognized.

2. As a result of a material test of a cut-off-test-piece, an elongation is below a specification of steel material and an impact value is espe­cially low.

3. As a result of a tension test of a cut-off-test-piece, it is recognized that a joint (by forging, rivet and weld) efficiency is very low because of the decrease of the shell thickness, deterioration of materials and other reasons.

It is recommended that repair or replacement in case of an exces­sive decrease of a shell thickness is conducted based on the following:

1. When maximum stress at a local area of a pipe shell or an average stress of a pipe shell (circumferential tensile stress by internal pressure) ex­ceeds 90% or 65% respectively of yield strength of the material used and thus a probable fracture is recognized.

2. The above maximum stress is calculated from the following formula which determines the maximum tensile stress concentrated around the edge of a concave when tension acts on a steel plate having a cylindri­cal concave, or from a formula having the same or more precision with the following one:

3 ,_r

l+2d ^d~ I

where <r_max: Max. stress at the edge of a concave (kgf/cm²)

a: Mean stress with no concave (kgf/cm²) t': Min. shell thickness of a concave portion (cm) _; .

< t: Mean shell thickness of a steel plate (cm)

Article 51. Recoating ? ?

When the coat on a steel penstock peels, immediate recoating shall be ,~ required in accordance with Article 38., this Chapter.

Description:

Omitted

Section 6 Anchor Block and Support

Article 52. Locations of Anchor Block

An anchor block shall be installed at behdsi)f the penstock. An anchor block shall also be installed at straighr^c^ruon, as the case may be. Description :

A penstock supported on the ^rouncFor in a^tunn^yshall be’furnished y/ith anchor blocks at bends to resist the forces whicn tend to^de^d the resisting force due to weight_of pipe and weight of .water in pipe and tend to the cause displacement of the pipe. These forces are resulting from in­ternal pressure, weight of pipe, weight of water in pipe, temperature, change etc. -r-t

Anchor blocks shall also be installed at ^ntermgUeu^Qipis⁷ in long/ straight portion betwen bends, to limit the pipe length between expulsion Joints and^the apchor blocks, and consequently to limit the displacement due to longitudinal forces and temperature change. The maximum spac­ing of anchor blocks is generally taken as 120 to 150 m in Japan, while 150 m is sp^qifLed by some authorities in other-countnesj especially by tV ‘ - _

U.S. Bureau of Reclamatigruand P G,S ^₍co., for example.

As anchor blocks may sometimes be hugetones, when they are installed at st££p slopes, the pipes can be anchored directly to bedrock instead of anchor blocks if appropriate in its quality¹, and furthermore post-tensioning may be made.

Article 53. Foundation of Anchor Blocks

An anchor block shall be installed on the foundation with sufficient bearing capacity. If this is difficult the foundation works shall be made so as to have sufficient bearing capacity.

Description:

An anchor block should be installed on the foundation with sufficient bearing capacity in order to prevent displacement. If it should be difficult to obtain such ground, because of topographical reason, foundation works shall be made so as to have sufficient bearing capacity.

Table 1. 53-1 are generally adopted for the allowable bearing capacity of the ground, although these values shall be determined through the field

tests.

' .h / A o•

V-.n, ‘

Table 1.53-1 Allowable Bearing Capacity of Various Foundations

Type of ground	Allowable bearing capacity (tf/m2)
Sand or clay Cc(lr -	10 A /
Clay mixed with sand or loamCfhAo)	15 .
Mixture of sand and gravel	< ’20 - - .. .
Gravel^ Soft rock: Sl^ale^mc^B Stone.	30 ‘ 100
(XqueoSs^roc^such as slate, schist	250
Hard rock: Igneous rock such as granite, diorite,
gneiss, andesite, etc. and hard con­glomerate, etc. ,	400
Piling foundation and grouting are employed for foundation work of

the anchor block.

Article 54. Stability Conditions for Anchor Block

An anchor block shall be safe against overturning, sliding, and crushing. Uv • FI w-

Description:

A resultant force working on an anchor block tends to overturn and slide an anchor block.

In order to be safe against an overturn, all forces acting on an anchor block including a reaction .force and self-weighushould be combined on the assj&nption of the worst conditions, and its resultant line of action should be positioned in the middle third of the base of the block.

...To be safe against the sliding, a component of a resultant force acting on an anchor block perpendicular to the bottom, should be larger than the value obtained by dividing a component of a resultant force parallel to a bottom by a sliding factor at the bottom of an anchor block.

A detailed study of a geologic evaluation and stress analysis is required, when the bottom of an anchor block is so constructed as to be in the clear shape of teeth in order to improve the stability of an anchor block against the sliding or it is assumed that an unstable sliding layer exists in a foun­dation ground although the stability is ensured between a block and the ground.

The following standard values have been taken as the sliding coeffi­cient between an anchor block and the ground:

0.75

For good bedrock

For soft and weak bedrock and gravel layer 0.50

For clay 0.30

To be safe against crushing, the compressive stress generated in an an­chor block should not exceed the bearing capacity, of the foundation and the allowable stress of the concrete.

An anchor block itself may be considered as a structure to be strong, and capable of resisting a tensile force to some extent. Thus a study of stability shall not be made on all horizontal planes, but only on the bound­ary plane between the block and the foundation. When the bottom of an anchor block is inclined almost parallel to the slope, the stability against overturning and sliding can be studied only on this slope.

Article 55. External Force to be Considered

External forces to be considered in calculating the stability of an an­chor block shall be those listed below:

4. Self-weight of the anchor block

x2. Weight of pipes and water borne by the anchor block

G. Axial thrust

A. Centrifugal force acting on a bend pipe portion

4. Unbalance force acting on a bend portion

5. Seismic force

When pipe axes upstream.and downstream of an anchor block are not on the same vertical plane, stability in a transverse direction shall be con­sidered.

Description :

1. Axial thrusts should be calculated from the following formulae. As for the signs, the direction to a power station from a head tank should be positive, the pipes upstream of an anchor block should be with no dash, and the pipes downstream should have a dash.

a : Intersecting angle between penstock center line and its horizon­tal line

/: Distance from anchor block to its adjacent support(m) L: Distance from anchor block to expansion joint (m) S: Weight of steel penstock per meter = it (D + O fy_s (tf}<^

7T

w: Weight of water inside penstock per meter = —D² (tf)/^

* D: Internal diameter of pipe (m)

/: Shell thickness of pipe (m)

' y}f

7_$: Unit weight of steel material = 7.85Jtf/m^J) c: Friction coefficient of support g: Acceleration of gravity = 9.8 (m/s²)

Head tank

Fig. 1.55-1 Typical Profile of Penstock

tU®' Power station

Expansion joint

(2)

Force due to weight of pipe

for the pipe on upstream

for the pipe on downstream

due to friction of water in the pipe the pipe on upstream

Force

for

for

the pipe on downstream

Pi = SL sina Pi' = S'L'sina^/

² g-rD³ _y 2/^

girD'³

where, Q : Discharge (m³/s)

f_w: Coefficient of friction resistance of a flowing water inside the pipe £=0.02

4. Force due to internal pressure acting on expansion joint

for the pipe on upstream P_A = H_Eir (D_E+t_E)t_E for the pipe on downstream P₄' = -H_e't (D_e +t_E')t_E where, H_E, H_E : Intenal pressure at the center of the expan­sion joint (tf/m⁷), design pressure for nor­mal condition and the static pressure for seismic condition

D_E,D_e' : Inside diameter of the expansion joint (m) t_E : Wall thickness of the inner sleeve (m)

5. Frictional force of support

for the pipe on upstream F, = c(w+ S)(L — -y)cosa for the pipe on downstream '= c(w^z + S')(L'-—)cosoi'

2

where, c : Friction coefficient of support (See Article 19., this Chapter.)

6. Frictional force of expansion joint

for the pipe on upstream F₂ =/_ett(D_e + 2t_E) for the pipe on downstream ' =/_£tt(D_£ ' + 2f_c') where, f_E: Frictional coefficient of expansion joint = 0.7 (tf/m) The frictional forces reverse their direction according to drop or rise in temperature. For the calculation purpose, the value whichever gives the worst condition in the following formulae should be adopted as the resul­tant force acting on the anchor block.

for the pipe on upstream P= P,+ P₂ + P₃ + P_A±F

for the pipe on downstream P' = P', + P'₂ + P'₃ + P'₄ + F'

where, F= F_x + F₂, and F' = F_t' + F₂'

The following should also be taken account in the longitudinal forces. If the penstock is equipped with the control valve, the thrust due to inter­nal pressure when the valve closed should be taken into consideration. If the pressure test should be executed in such manner that a certain length of the pipe section is pressurized with bulkheads attached at the both ends, thorough investigations will be required, because the anchor blocks at the upstream and the downstream ends will be subjected to the forces which = are very different from those in normal condition, as stated in the Descrip­tion for Article 33., this Chapter.

FOR 1

Chapter 1 STEEL PENSTOCKS 7

Section 1 General 7

Section 2 Design 4

Description, 19

2. Material and Allowable Stress 31

Description: 31

3. Pressure Lining Part 46

P‘=²-^59£-7&^: . 48

(cwlT+U^V.- 51

Description: 56

4. Attachment Installations 91

Description: 97

Section 3 Manufacture 101

Section 4 Installation 107

Section 5 Maintenance 119

Section 6 Anchor Block and Support 127

Chapter 2 HYDRAULIC GATE 137

Section 2 Outline of Design 153

2. Gate Leaf, Gate. Guide and Anchorage 162

Description: 196

Description: 201

3. Gate Hoist 201

Description: 202

Description: 205

Description: 206

Description: 206

Description: 210

Section 3 Design Particulars 213

1. Fixed Wheel Gate 213

Description: 223

—~^p 223

F=p._r(q + Pb)Ll 224

2. Radial Gate 225

Description: 225

Description: 226

Description: • ¹ 228

3. Long Span Gate 229

Description: 221

4. Bottom Hinge Flap Gate 222

Description: 222

Description: 224

5. High Pressure Gates and Valves 226

Description: 226

Description: 229

6. Selective Water Withdrawal Equipment and Surface Water Withdrawal Equipment 235

Description: 235

Description: 236

Description: 236

7. Trash Rack 240

Description: 241

Section 4 Manufacture 245

Description: * 245

Description: 245

Section 5 Installation 246

Description: ' ' ^: ''f. .1.... ' .a? a ' 247

Description: 247

Description: 248

Description: 254

Description: 256

Section 6 Inspection 257

Description: 258

Section 7 Maintenance 259

Description: 259

Description: 259

Description: 259

Description: 260

Description:. - 260

Description: 261

Description: 261

Description: 262

Description: 262

. Chapter 3 STEEL STRUCTURE 269

Description: 269

Description: 269

Section 2 Design 269

Description: 270

Description: 270

Description: 270

Description: - ■ ' 271

Description: 273

Chapter 4 WELDING 274

Section 1 General 274

Description: 274

Description: - 277

Description: 292

Section 2 Welded Joint 296

Description: 296

Description: 289

Description: 293

Description: ".'A • 295

Description: 297

Description: 298

Description: ^; ■ 300

Section 3 Welding Procedure 302

Description: 302

Description: 305

Description: 307

Description: 308

Description: 309

Description: 309

Description: 311

Description: 313

Description: 313

f 313

Description: 315

Description: 323

Section 4 Heat Treatment 327

Section 5 Test and Inspections 334

» Description: 335

Description: 336

Chapters 340

RIVETED, HIGH STRENGTH BOLTED AND BOLTED CONNECTIONS 340

Section 1 General 340

19. Description: 358

79. Description: Omitted 352

81. Description: Omitted 352

84. Description: Omitted 352

111. Description: 354

193. Description: 359

198. . Section 4 Bolted Connections 361

217. Chapter 6 SAFETY AND SANITATION 365

H: Hydraulic pressure in the_t center of a bend portion (t_r/m²), design internal pressure for normal condition

■r and the static pressure for seismic condition

3. Seismic force P_e can be determined from the following formula:

P_e = k'G

where, k: Seismic intensity in the horizontal direction

Values between 0.10 and 0.15 are generally adopted ex­cept for poor foundations

G: Weight of anchor block itself plus weight of pipe and water taken as cooperating with the block. The latter is generally given as the weight of the ones between the. middle point to theadjuscent supports on upstream and^: downstream of the block.

Article 56. Location of Support

For a steel penstock, supports shall be installed at such an interval as not to produce an excessive stress in a pressure lining part.

Vwyu . fctH ztrX; A.'*"* kK

_r..v kvO

Description :

Saddle supports^ are generally spaced 6m. This supporting type, com­pared with a ring support type, has less pi rcu.m.fej^fl^l .rigidity and so when the interval is large, vibration is li^bletotake place and the reac- tion force increases and thus the circumferential bending moment gener­ated on a pipe wall increases. From the point of view of installatiomwork, it is convenient to install a support for every pipe section and thus the interval is set at 6m in many cases. However, because of conditions of installation work and .so forth, support intervals of about 8m and 12m are also employed corresponding to the length of the pipe section.

A steel penstock as a cylindrical shell is a high-order statically indeter­minate structure and the pipe itself works like a beam and supports its self-weight. Therefore, in case of a ring support type in which a theoreti- - cal analysis as a shell is available, a long supporting interval for the pipe can .be taken by an effective use of property of the pipe as a beam. In•' this case, about 18m is commonly taken as a support interval. But in some cases, an interval longer than the above has been employed.

Since the axial stress generated in a pressure lining part increases with a long support interval, the length of the interval should be selected within a range not detrimental to the strength of a pressure lining part.

Article 57. Foundation of Support

Foundation of a support shall be in accordance with Article 53., this Chapter.

Description :

Omitted

Article 58. Design of Support

A support shall be so constructed as to safely support a steel penstock against an external force acting on the support.

Description: . .

A support should be sq^designed as to support weight of a penstock (self-weight of penstock plus water weight inside the pipe) through a mov­able part and to resist an axial friction force caused by expansion and con­traction of a pipe with its temperature change. Friction coefficients between a pipe and a support can be derived from the values in Article 19., this Chapter, dependent upon supporting conditions. With a large diameter

■ - ■ • , _____ - ■ — ~ '• ! _t _

pipe and a high support, care should be taken because the wind-pressure > when a pipe is empty may be one of the design elements. — A⁵ a -

As for a resultant force, on the assumption of the w&$st conditions : j including an earthquake, a perpendicular reaction force generated by " supporting a pipe, a horizontal force from a frictional resistance due to-j,/ temperature change and a si4W3X19{ce-by a wind pressure, safety against _g the overturning, sliding and crushing should be studied in the same way . as the case of an anchor block in accordance with Description, Article 55., this Chapter.

Generally, 120° is employed as a supporting angle for a concrete sad- - die. This angle is best suited from viewpoint of a bearing area for a pipe, volume of concrete, and a circumferential bending moment stated in Description, Article 28., this Chapter.

Article 59. Repair of Anchor Block and Support

An anchor block and a support shall immediately be repaired if its main­tenance seems difficult due to cracks or shifting.

Description:

If any damages are found on an anchor block and a support, these

• should be well-confirmed, and the cracks, deterioration of the concrete, or its shifting should be recorded so as to be data for foreseeing of the danger. Crack should be checked by an application of a lean mortar (gener­ally called “test mortar”, the progress of cracks on the concrete can be checked by cracks generating on the mortar), and by measuring the gaps .of cracks, and the shifting by observation of a reference point.

<• If any problems in terms of maintenance and control are recognized according to the above checks, these structures should be repaired and some measures to prevent the shifting should be taken.

Article 60. Observation of Shifting Anchor Block

For an anchor block, taking the quality of its foundation into consider­ation, a measurement point shall be provided in order to measure shift­ing of an anchor block, and the position of an anchor block shall be kept clear.

Description :

A measurement point for observing a shifting of an anchor block should be set so as to keep its position and height clear when the foundation of .

an anchor block is of a poor and soft ground, when the sinking or shift­ing is expected in future, or when shifting is expected geologically- and topographically from a point of view of a foundation ground of anchor block.

Article 61. Protection Work for Bed and Cutting Slopes

Bed and cutting slopes shall be protected so as not to be detrimental to the maintenance of a steel penstock, and shall always be well- maintained.

Description:

Omitted