HOW TO SELECT THE RIGHT VALVES



INTRODUCTION:

Valves are one of the important mechanical (sometimes electro-mechanical) device that helps in controlling the fluid flow through pipes or tubes.Selecting the right kind of economic valve for a specified fluid service requires many considerations.

As explained by a leading valve manufacturers, the Valve Selection is a very extensive and complex subject since the valve selected to work under the same conditions will differ from one client to another. It is necessary to compare the cost and come to an agreement with the client.

CRITERIA FOR VALVE SELECTION :

The selection of valve type requires an understanding of the following.
• Valve Function
• Service Characteristics
• Cost of Valve
• Valve Selection Based on Valve Function
• There are two basic principles on which valves are constructed.

To summarize, there are four basic valve types, each type having its own individual characteristics and offering its own particular advantages or disadvantages. For this reason, many modifications and variations of the basic type are made by valve manufacturers.

An appraisal of the chief characteristics of the above four basic valve types is given in the following:

Globe valve Selection : The globe valve is used for flow regulation or as a block valve where resistance to flow is not critical and positive closing action is required. They have a tortuous configuration which is typical of the closing method and results in higher resistance to flow compared with other valves.High-performance globe valves overcome the problems of the conventional globe valves which is a boon for the manufacturers and global valves supplier.

Gate valve Selection : Gate valves are used for on/off operation on hydrocarbon, general process, and utility services for all temperature ranges. They have straight through configurations which are typical of the sliding method, therefore, minimum resistance to flow. Select the market leading gate valve supplier for buying valves which met all industrial standards.

Disadvantages are that they have the slowest action of all valves because the gate has to be moved a distance greater than the bore of the valve, which also means that the valve is of necessity bulky in height.

Plug valve Selection : Plug valves have a quarter-turn operation, plugs are tapered or parallel plugs, and are suitable for most on-off clean process and utility services, including non-abrasive slurries. They have straight through configurations typical of the sliding method.

The disadvantages of the basic plug valves are:
• Firstly, its quick action can lead to a water hammer on hydraulic installation when it is closed too rapidly,
• Secondly, it is difficult to combine tight shut-off with ease of operation.

Ball valve Selection :  A low torque quarter-turn valve, with a low resistance to flow, suitable for many on-off utility and process services. It has a straight-through configuration typical of the sliding method of closure.

Butterfly valve Selection :A low torque, quarter-turn, rotary action valve with a straight-through flow configuration in which the disc is turned through 90 degrees, close to open position, in axial turning bearings and is used as a control or block valve. It is of compact design and may be obtained with or without flanges and linings. Seating arrangement may be soft (use of body lining, trapped ‘O’ ring, etc.) or metal to metal. As opined by leading Butterfly valve suppliers and Ball valves suppliers the quarter-turn valves are dominated by butterfly and ball valves.

Further a leading valve suppliers opines that the valve selection is dependent on the characteristics of the services as follows:

• Fluid type
• Fluid characteristics
• Pressure and temperature limitations
• Operation and maintenance requirements

1. Fluid Type: The fluid being handled should be classified as follows:

• Liquid (including Two-Phase)
• Gas
• Steam
• Slurry
• Solids

2. Fluid Characteristics: The characteristics and condition of fluids and slurries require careful identification since these are often the most significant factors in selecting the correct type of valve.

3. Pressure and Temperature Limitation: Valves are normally allocated a rating according to the maximum operating pressure and temperature or the ratings of the piping system and flanges. The temperature also limits the materials used in the valve construction, particularly the internals, trims, seals, rings or lubricants. These are normally defined in the “Piping Material Specification”.

4. Operation and Maintenance Requirements: Operation and maintenance requirements can influence selection and design.

• Operability
• Leak tightness (internal and external)
• Maintainability
• Storage and commissioning
• Pipeline requirements

CONCLUSION:

Generally the costs of valve types cannot be simply compared because they vary depending on the countries where they are produced, vendors and the balance of demand and supply. In most cases, clients call for stress relieving, annealing, radiographic inspection, etc. of the valves, which affects the cost of the valves.

Fevisa, known as European Valve Manufacturers and Spanish Valve Manufacturers and we are the  leading valve stockist in Dubai, advises help our clients conduct necessary inquiry and procurement of suitable valves that are WRAS Approved Valves, based on the service conditions and the clients’ requirements, after they have defined their industrial working conditions.

In Fevisa valves are popularly called as Europe Origin Valves we are well known for supplying stock valves  and ex-stock valves for various industries around the world. Contact us for a hassle free valve selection!