9.1.5.Tarapur Units — India

Significant savings in time were also achieved by using open top installation at Tarapur Units 3 and 4. The VHL crane was used to set approximately 50 items of equipment in position, including the steam generators (shown in Fig. 123) moderator heat exchangers, pressurizer, calandria (shown in Fig. 124) primary circuit headers, fuelling machine, and several heat exchangers. The steam generator was lowered and positioned in less than a day, thus saving considerable construction time compared to that used for earlier heavy water reactors (HWRs) in India.

9.1.6.Tomari Unit 3 — Japan

In Japan, Mitsubishi used a VHL crane to install equipment at Tomari Unit 3 (shown in Fig. 125).

9.2. LIFT TOWERS

An alternative to VHL cranes is the lift tower, also known as a hoist support structure. These structures (shown in Figs 126–128) can be ideal for locations where hoists are made in a rectangular pattern (such as a bridge crane) and where the overall height requirement of the lift is limited. Lift towers are therefore more applicable to drawer or slide-in construction applications than to open top construction of tall structures.

FIG. 123. Steam generator installation at Tarapur, India.

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FIG. 124. Lifting of calandria at Tarapur, India.

FIG. 125. Use of very heavy lift crane to lift 40 m diameter containment vessel upper head (credit: Mitsubishi Heavy Industries, Ltd).

Lift towers have the following advantages over high capacity cranes:

—Less mobilization and demobilization cost compared to the high cost of counterweight shipping and assembly for a high capacity cranes;

—Less susceptibility to wind, with no requirement for a boom lay-down area in high winds.

The key objective of the most cost effective equipment handling strategy is to minimize the lifting radius in order to minimize the crane size and counterweight requirement. The lift tower has the advantage of requiring no counterweight.

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FIG. 126. Lift tower used for heat recovery steam generator erection.

FIG. 127. Lift tower used in pressurized water reactor steam generator replacement.

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FIG. 128. Lift tower used in drive-through arrangement.

FIG. 129. Stand jacks used on top of lift tower arrangement.

A disadvantage of lift tower cranes is that an assist crane is required to build the lift tower structure. However, the capacity of the assist crane is normally much less than the capacity required to lift the load intended to be lifted with the lift tower.

Instead of a bridge hoist on top of the lift tower columns, strand jacks can be used as shown in Fig. 129. The use of a gantry crane that travels on top of the lift tower rails may save additional time. Figure 130 shows

a conceptual drawing of this equipment. This arrangement may be expensive, however, and the cost-benefit of construction and labour time savings must be reviewed to determine cost—benefit.

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FIG. 130. Gantry crane placed on lift tower arrangement.

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