Valves

 

This article gives a general introduction to the types of valves that are in common use in petroleum industry. 

Introduction:

In the petroleum industry we may meet with different isolating or control valves of different types, ranges, size and so one. Indeed, they have to perform acceptably during a long life, but also consideration of many factors is required in the selection process. General technical factors that are to be taken in account include:

  • Weight
  • Size
  • Ease of Maintenance
  • The specific function (isolation, flow control...)
  • Operability
  • Commercial factors, such as cost and delivery

 

 *Example of a Globe Valve. Source [3]

 

Basic Valve Types:

Basic valve types that are used in the oil and gas industry are shown in figure below. The path taken by the fluid when flowing through a fully open valve varies in complexity, depending on the valve type. The energy dissipated in friction or noise will be greater the more tortuous the path, and this may be a consideration in valve selection.

 

                                                                              *Different Valve Types. Source [1]

 

The configuration of the flow path through a valve and the method used to restrict or arrest flow determine the characteristics of a valve (Figure below) and influence the selection of a particular type of valve for a particular function.

 

                                                                                                       *Valves Operating Characteristics. Source [1]

 

Valves may be grouped according to the method by which the closure member (gate, ball, disk, plug, etc.) moves relative to the seat. The movement relative to valve seat may be sliding, closing, or flexing and the path of travel may be linear or rotary. Valves are often described as having linear action (or multiple turn if screw-operated) or rotary action (more commonly, quarter turn). The different methods of restricting flow are:

Sliding Method: The closure member slides across the valve seat face to open or close the valve. Linear action valves using the sliding method are parallel gate valves. Rotary action valves that use this method are ball valves and plug valves.

Closing Method: The closure member moves away from or towards the valve seat to open or close the valve. Closure is achieved either by abutment against the seat face or by projection into a seat orifice. Linear action valves using the closing method are globe valves and check valves. Rotary action valves using the closing method are butterfly valves and swing check valves.

Flexing Method: Opening or closing is achieved by flexure of a resilient membrane within the valve body. Linear action valves using this method include diaphragm and pinch valves. The mechanical closure member is external to the fluid flow and the external fluid pressure may also be used to flex the membrane. And  I didn't find a rotary action valves using this method.

 

Basic Valve Functions:

 

 

 References:

[1] ''Valves'' Robert Gordon University Documentation.

[2] Petrowiki ''Relief valves and relief systems'' , Link

[3] Quora ''What is the difference between a gate and a globe valve?'', Link

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