Pump or compressor discharge

Blocked-outlet pressure protection may be required because of overpressure by pumps or compressors. The following general guidelines should be used to establish the protection requirement and contingency  

Estimate the pump or compressor discharge pressure as the sum of PRV relieving pressure and the pressure drop between the pump or compressor discharge point to the location of PRV. 

Estimate the differential head, which will be higher than the normal. 

From the pump or compressor performance curve, establish the flow rate, which will be the required contingency. 

Process engineering and design using Visual Basic 

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For ease of illustration we will consider the characteristics and behaviour of a centrifugal pump which is similar in behaviour to radial/axial flow fans and centrifugal/screw compressors. Figure 63 shows the mechanical connection of a flow valve to control the output of the pump or the discharge of the fluid through the throttle of the valve. Figure 6.39 illustrates the characteristics of the pump ... 

An ejector is a simplified type of vacuum pump or compressor which has no pistons, valves, rotors, or other moving parts. Figure 10-98 illustrates a steam-jet ejector. It consists essentially of a nozzle which discharges a high-velocity jet across a suction chamber that is con-... 

The most difficult task for the safety-valve sizing is the achievement of the maximum flow-rate to be discharged. In case the safety valve is used to save the operation of a pump or compressor, their maximum mass-flow-rate is the basis for the sizing. Much more effort is necessary in systems where vessels, complex piping systems, pumps, and thermal expansion can activate the safety valve. In most cases, some discussions with the relevant authorities are necessary to clarify all assumptions for risks relevant to safety. 

For centrifugal pumps or compressors, blocked-discharge overpressure protection is not required if tiie sum of no-flow differential head and relieving pressure of the suction PRV is less than flie design pressure of the equipment on the discharge side. 

If maximum possible discharge pressure from the centrifugal pump or compressor exceeds the design pressure of the downstream equipment, pressure protection will be required for a blocked-discharge scenario. The contingency should be estimated by the following procedure ... 

For positive displacement pumps or compressors, PRV for a blocked-discharge situation will always be required. For pumps, the contingency will be the normal flow rate. For compressors, the contingency will depend on the change in the suction condition in a... 

Volume 1 explains that pumps ean be classified as either positive-displacement or kinetie. The same is true for compressors. In a positive displacement compressor the gas is transported from low pressure to high pressure in a device that reduces its volume and thus inereases its pressure. The most common type of positive displacement eompressors are reeiprocating and rotary (serew or vane) just as was the ease for pumps. Kinetic compressors impart a veloeity head to the gas, which is then converted to a pressure head in accordance with Bernoulli s Law as the gas is slowed down to the velocity in the discharge line. Just as was the case with pumps, centrifugal compressors are the only form of kinetic compressor commonly used. 

Installation requirements for rotary positive-displacement compressors are similar to any rotating machine. Review the installation requirements for centrifugal pumps and compressors for foundation, pressure-relief, and other requirements. As with centrifugal compressors, rotary positive-displacement compressors must be fitted with pressure-relief devices to limit the discharge or inter-stage pressures to a safe maximum for the equipment served. 

This occurs due to leakage or accidental discharge from an enclosed vessel, pump, compressor, value, flange or the like. 

Underground station An enlargement of an entry, drift, or level at a shaft at which cages stop to receive and discharge cars, personnel, and material. An underground station is any location where stationary electrical equipment is installed. This includes pump rooms, compressor rooms, hoist rooms, battery-charging rooms. 

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