10 Steps to Select A Right Ball Valve

A ball valve is a shut-off valve that uses a rotary ball with a bore to control a liquid or gas flow. The rotary ball is rotated a quarter-turn (90°) around its axis to allow or block the flow through the valve. These valves are mostly preferred for their longer service life and reliable sealing property. There are many options available in the market when it comes to the selection of ball valves. However, the wide range of operation, connection type, circuit function, housing material, and many other criteria make the valve selection process complex. This article will walk you through the ball valve selection process.

 Before you embark on buying a ball valve for your shut off applications, this simple selection guide will help you choose the model that will effectively serve your purpose. This guide contains important factors to consider that will help you select the model that will be around for years to come without worrying of frequent replacements.

Step 1: Operation Type

The ball valve can be operated manually, electrically, or pneumatically. Different actuation methods all have their advantages and disadvantages.

Manual: You should select a manual ball valve if you have a low budget, no electricity/compressed air at installation, or if no automation is needed. If the ball valve needs to be turned on/off frequently or the system needs to be automated, a manual ball valve should not be used.

Automatic: Deciding between an electric ball valve and a pneumatic ball valve can be difficult. It typically comes down to what is available at the installation site (electricity or compressed air) and the torque needed (pneumatic ball valves have a higher torque, pneumatics are therefore used for larger sized valves). Electric ball valves have a higher initial cost but lower operating cost compared to pneumatic ball valves. For a more in-depth breakdown, read our electric vs pneumatic ball valve article.

Step 2: Circuit Function

Ball valves may have 2-way, 3-way, 4-way, or 5-way circuit functions based on the number of ports.

• 2-way ball valves: are the most common ball valves. These valves provide a straight flow path from input to output.
• 3-way ball valves: 3-way ball valves have three ports and are available with either an L or T bore. The L and T designations refer to the design of the internal bore, which will determine the direction of flow. A 3-way ball valve with a T or L port allows mixing, distribution, or redirection of flow direction for different applications. This makes this valve suitable for heating or cooling applications for water, chemicals and oils.
• 4-way ball valves: 4-way ball valves are not as common as 2- and 3-way ball valves, but it is important to know the variations. A 4-way ball valve is usually available in four different variations: L-port, T-port, X-port (LL-port), and straight.
• 5-way ball valves: are available as valves with perpendicular double L-bore; these 5-way valves are rare.

Step 3: Chooseing Material

The Chooseing Material should be compatible with the fluid media being used for the application. Common materials and their features are:

Brass

• Suitable for neutral and non-corrosive media.
• Brass is versatile, durable and resistant to high temperatures.
• Not suitable for salt water (sea water), distilled water, acids and chlorides.

PVC

• Suitable for corrosive media such as sea water, most acids and bases, salt solutions and organic solvents.
• Not resistant to aromatic and chlorinated hydrocarbons.
• The temperature and pressure range is lower than that of brass and stainless steel.

Stainless Steel

• Very good general chemical resistance to almost any medium.
• Very abrasion resistant and resistant to high temperatures and pressures.
• Not suitable for hydrochloric acid, chlorides, bromine and bleach. On the other hand, swimming pool water has a low chloride concentration so the use of stainless steel here is possible.

 

Step 4: Seal

Ball valves have two seals. Seat rings, which are around the ball on the inlet and outlet, and an o-ring to seal the stem. Typically, the seat rings are made of PTFE. For both seals, the seal material should be compatible with the fluid media being used for the application. Common materials and their features are:

EPDM

• EPDM is very suitable for water, steam, ketones, alcohols, brake fluids, acids/alkalis in low concentrations.
• Excellent resistance to weather influences and ozone.
• Typical operating temperature range between -10° and 130°C.

FKM (Viton)

• FKM has an excellent overall chemical resistance to oils and solvents such as aliphatic, aromatic halocarbons, acids, animal and vegetable oils.
• Typical operating temperature range between -10°C and 120°C.
• It has good mechanical properties, resistance to compression, and suitable for high temperatures (not for hot water/steam).

NBR

• NBR has good resistance to compression, tearing, and wear.
• Compatible with oil products, solvents, and alcohol.
• Typical operating temperature up to 80°C.

PTFE (Teflon)

• PTFE is resistant to almost all fluids.
• PTFE is relatively hard; this makes it suitable for higher operating pressures and temperatures.
• Typical operating temperature range between -30°C and 180°C.

Polyoxymethylene

• POM is suitable for high-pressure and low-temperature applications.

CSM (Hypalon)

• Hypalon is noted for its resistance to chemicals, temperature extremes, and ultraviolet light.

Step 5: Connection type and size

There are different sizes and types of ball valve connections to connect them to a system. The common ones are:

• Standard/Threaded ball valve: Threaded connections are the most common form of connection type and used in a wide range of temperature and pressure applications.
• Flanged ball valve: These ball valves have a flanged connection to join the port to the piping system. These valves are often used on larger sized pipes. Choosing a flanged ball valve requires consideration for pressure ratings and flange compression class, which indicates the highest pressure it can withstand.
• Welded ball valve: In the welded connection, the ball valve is welded directly to the pipe. This type of connection is suitable for applications where zero leakage is required.
• True union ball valve: These valves have a solvent socket connection at each port. The center part of the valve can be easily dismantled and taken off while the valve is installed. This is suitable for quick repair and maintenance in the flow system.

• Step 6: Flow Coefficient (Kv)

• The flow coefficient, or Kv value, is expressed as the flow rate in m3/h of water at 20°C at a pressure drop of 1 bar. The flow coefficient can be calculated as follows:

  $$Kv=Q\times \sqrt{\frac{dp}{SG}}$$

  • Where:
  • Kv= flow coefficient
  • Q= flow rate (m3/hr)
  • dP= Pressure differential (bar)
  • SG= Specific gravity (water=1)

  • Step 7: Pressure

    Make sure the ball valve can withstand the minimum and maximum pressures in the system. The material of the housing helps determine the pressure range of a ball valve. For maximum pressure, stainless steel usually has the highest rating, followed by brass and then PVC housings. It is important to review your ball valve's data sheet to confirm the appropriate pressure range.

  Step 8: Temperature

  Ensure that the valve material can withstand the maximum and minimum temperature requirement of your operation. The housing and seal material typically determine the temperature range of a ball valve. Common ranges are below, but review your ball valve’s datasheet to confirm.

  • Brass ball valve: -20°C to 60°C (-4°F to 140°F)
  • PVC ball valve: -10°C to 60°C (14°F to 140°F)
  • Stainless steel ball valve: -40°C to 220°C (-40°F to 428°F)

  Step 9: Approvals & Standards

  Depending on the application, ball valves may need to be made to certain standards or receive approvals from regulatory bodies to be used with certain applications, like drinking water or gas applications

  • Drinking water: WRAS, KIWA, or DVGW approvals
  • Gas: DVGW or EN-331 approvals.
  • ATEX: The ATEX regulations are two EU directives detailing minimum safety requirements for workplaces and equipment used in explosive atmospheres.
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  • Step 10: Valve Cost

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  • Upon consideration of the four factors – working pressure, temperature, fluid type, and fluid volume, you should now consider the cost of the valve. The cost of the valve is also associated with the valve size and its material composition. The brand of the valve is also an associated factor with the valve cost. There are many valve manufacturers and some of them have online sites where you can view their online catalogues.
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