Positive-Displacement Meters

The installation of SCADA systems with automatic well testing generated a need for gas measurement over a wide flow range with direct readout capability. The “rotary” positive-displacement gas meter is similar to the liquid “lobed-impeller” or gear-type meter. Technical Data used in the field explained in diploma in petroleum technology. The rotary gas meter has the capability to measure gas accurately over a range of about 15 to 1 compared with about 4 to 1 for an orifice meter with a fixed orifice plate size. The rotary meter can be equipped with mechanical compensation on indicated volume for static pressure and flowing temperature corrections. The rotary meter needs to be protected from over-range and liquid accumulation within the measuring elements. These meters are usually applied to low-pressure gas measurement service.

Gas-flow computers were developed to use existing orifice-meter runs and to provide a direct readout of gas volume that was compatible with SCADA. These devices use static and differential pressure electrical transducers on a standard orifice meter as a basis for gas measurement. The computer integrates the signals from the transducers and combines with fixed data on meter run size, plate size, etc. to develop a gas volume. The volume readout will be in the form of a switch closure that will register on an internal counter and provide input to electronic counter in an RTU. Some more details of diploma in petroleum technology are as under.

Some gas-flow computers can accept a temperature transducer input to measure temperature of flowing gas stream for improved accuracy of volume measurement. Computers also may have capability to use two differential pressure transducers (e.g., 0 to 20 and 0 to 200 in.) and to select input from the unit providing most accurate instantaneous reading for integration. Early gas-flow computers were analog devices. Many current designs are digital units based on a microcomputer. The flow computer integration function also is being done by the microcomputer-based RTU. All designs have integration accuracy compatible with the basic measurement capability of the orifice meter. TSK Training for Skills and Knowledge is the best institute in Rawalpindi Islamabad for Pakistani Students who wants to join diploma in petroleum engineering.

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