How do you choose a control valve?

How do you choose a control valve?

Control Valve SelectionGive careful consideration to selecting the correct materials of construction. Consider the operating temperature and pressure the control valve will be exposed to. Consider the degree of control you require and ensure the selected valve is mechanically capable of achieving the desired operating conditions.

How do you control the flow rate of a positive displacement pump?

Controls for PD pump flow rates must take one of three approaches. First, modify the pump so that each stroke (reciprocating or diaphragm) moves a different amount of flow. Second, alter the speed of the pump. Third, use a recycle stream and change the amount of recycle.

Why must Positive displacement pumps are protected by relief valves?

Positive displacement pumps will discharge at the pressure required by the system they are supplying. The relief valve prevents system and pump damage if the pump discharge valve is shut during pump operation or if any other occurrence such as a clogged strainer blocks system flow.

Which of the following is a positive displacement pump?

Explanation: Rotary-type positive displacement: internal gear, screw, shuttle block, flexible vane or sliding vane, circumferential piston, and flexible impeller, helical twisted or liquid-ring pumps.

What are the positive displacement pumps?

What is a positive displacement pump? A positive displacement (PD) pump moves a fluid by repeatedly enclosing a fixed volume and moving it mechanically through the system. The pumping action is cyclic and can be driven by pistons, screws, gears, rollers, diaphragms or vanes.

What are the two types of pumps?

There are three basic types of pumps: positive-displacement, centrifugal and axial-flow pumps. In centrifugal pumps the direction of flow of the fluid changes by ninety degrees as it flows over impeller, while in axial flow pumps the direction of flow is unchanged.

What is positive and negative displacement pump?

Pressure – Positive displacement pumps work for high pressure applications, pressure might be upto 800 bar. Non-positive displacement pumps are basically used for low pressure applications and are designed to work for a maximum pressure of 18 to 20 bar.

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