- State the function of Valve 2.Describe the three types of Valve 3.List the four uses of pressure control valve 4.Describe two types of relief valve 5.State the difference in cracking pressure and full flow pressure 6.Describe the two main types of pressure reducing valve 7.State the function of a pressure sequencing valve 8.State the function of unload valve 9.List and describe five types of directional control valve
1- The function of Valve is to control ( regulate ) / start and stop flow of a fluid in a pipeline.
2- Three Types of Valves: Globe Valve / Gate Valve / Butterfly Valve
3- Uses of pressure control valve: Protects the pipeline from over pressure by maintaining a desired value of pressure under the high set point, Also pressure control valve regulates (throttle) the flow of a fluid in the pipeline depending on the pressure of the fluid passing and there is the safety relief valve that opens when a high set point reached to vent the over pressure only and then closes again, this type is mounted parallel with the pipeline. There is also the pressure safety valve that is normally closed and opens only when the over pressure reached to vent the whole pressure into the atmosphere to protect the equipment. The last type might need calibration every time it is used.
4- Two types of relief valve: Conventional spring loaded and Pilot operated.
5- The Cracking Pressure is the pressure at which a relief valve first opens to allow fluid to flow through. / The Full Flow Pressure is the pressure when the valve is bypassing its full rated flow.
6- Types of Pressure reducing valve are *A)*Direct-acting . The simplest of PRVs, the direct-acting type, operates with either a flat diaphragm or convoluted bellows. Since it is self-contained, it does not need an external sensing line downstream to operate. It is the smallest and most economical of the three types and is designed for low to moderate flows. Accuracy of direct-acting PRVs is typically +/- 10% of the downstream set point. *B)*Internally piloted piston-operated . This type of PRV incorporates two valves-a pilot and main valve-in one unit. The pilot valve has a design similar to that of the direct-acting valve. The discharge from the pilot valve acts on top of a piston, which opens the main valve. This design makes use of inlet pressure in opening a large main valve than could otherwise be opened directly. As a result, there is greater capacity per line size and greater accuracy (+/- 5%) than with the direct-acting valve. As with direct-acting valves, the pressure is sensed internally, eliminating the need for an external sensing line. C) Externally piloted . In this type, double diaphragms replace the piston operator of the internally piloted design. This increased diaphragm area can open a large main valve, allowing a greater capacity per line size than the internally piloted valve. In addition, the diaphragms are more sensitive to pressure changes, and that means accuracy of +/- 1%. This greater accuracy is due to the location, external to the valve, of the sensing line, where there is less turbulence. This valve also offers the flexibility to use different types of pilot valves (i.e., pressure, temperature, air- loaded, solenoid or combinations).
7- A sequence valve is somewhat similar to a relief valve except that, after the set pressure has been reached, the sequence valve diverts the fluid to a second actuator or motor to do work in another part of the system.
8- The air compressor unloader valve provides a critical function in preparing your air compressor to restart.
9- There are different types of DCVs that are classified based on the fluid path: Check valves / Shuttle Valves / Two-way valves / Threeway valves / Fourway valves
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