7.Analog rotary speed sensor

The unit consists of a small low-power D.C. generator. This generator is driven via a belt and pulley from the rotary table drive shaft.

The unit produces 7 VDC per 1000 Revolution Per Minute (RPM).

The Final RPM will depend upon the gearing. The DC signal is isolated through a signal conditioner electronic board .

8.Pit volume sensors

The pit monitoring system uses a Delaval sensor to monitor individual pits. The computer system allows a total flexibility in defining the active and reserve pit systems. The configuration can be changed quickly through the keyboard. Alarms are computer controlled and can be set up for low and high levels on the active system, the reserve system, or on individual pits. The system can monitor up to 16 pits.

On trips the gain tank and trip tanks are also assigned through the trip monitoring programme for complete coverage of the pit system.

On connections the expected flow back gain encountered at various pump rates is entered. The system can correct for alarm if unexpected changes are seen during the connection.

Delaval sensor use a non contacting magnetic float activate discrete reed switches in reed switch resistance string inside a stainless steel pole. The position of the float determines the resistance and hence the voltage fed to the computer.

The system is very robust and has been field proven for years as the simplest and most reliable of pit measurement in standard situations.

If access is severely restricted or the pits are deep, we use ultrasonic sensor. The Endures and Hawser DU 523 Z is normally specified. These have microprocessor based filtering in the sensor to condition the signal and reject spurious echoes, temperature compensation self monitoring for faults and a simple calibration procedure.

Ultrasonic

9.Flow out sensors

Flow Padle Type

Th e flow out sensor normally specified is of the paddle type. Flow in the flowline causes a rotation of the paddle and a corresponding rotation of a 1 turn potentiometer. Various paddle sizes are available to suit the different flowlines. Non-linear and logarithmic calibrations in the computer allow accurate calibrations to be made for most installations over a wide range of flows.

Th e sensor is supplied with a 10 VDC excitation supply which is fed through the 10 KOhm, one turn high accuracy potentiometer. This gives a signal output of 1-10 VDC. This analogue signal is input directly to the computer. If a pressure rated flow sensor is required for installation on offshore diverted systems, a Martin-Decker MFTX05A non-contacting mud flow sensor can be supplied on request. The paddle flow sensor is a well proven and rugged instrument. However the accuracy of its measurement depends on the installation in the flowline. As the flow in the flowline is such an important measurement for the well and rig safety we recommend the installation of a magnetic flowmeters for long term contracts and where the rig’s construction allows. The magnetic flowmeter has to be mounted in a section of the flowline which is full to provide an accurate measurement. The most recent designs of meter will work in fluids with a conductivity above 1 micro mho/cm. In practice this will allow use in most field oil base muds.

Electromagnetic Wave Type (EWS System)

The sensor is installed in a closed V-shaped piping and measure the flow through generating induction voltage in a magnetic field.

The v- shaped piping is designed to keep the inside of the sensor always filled with fluid.