How to Select Butterfly Valve from ZZJG Valve

As the world's leading butterfly valve equipment manufacturer, ZZJG Valve will introduce the following on the issue of how to select butterfly valves. We hope it can help you who are currently selecting butterfly valves.

1. Determined by the application conditions

Medium characteristics:

Type of fluid (gas, liquid, medium containing particles/corrosive, etc.).

The temperature, viscosity, and corrosiveness of the medium (such as acid, alkali, oil, steam, etc.).

Working pressure and temperature:

Check the maximum operating pressure (PN/Class) and temperature (hot, normal or cryogenic).

Metal-sealed butterfly valves should be selected for high-temperature media, and attention should be paid to the low-temperature brittleness of the material for low-temperature media.

Flow control requirements:

Whether the flow needs to be regulated, or is it only used for opening and closing (on/off type).

2. Select the structure type

Classification by valve plate structure:

Centerline butterfly valve: The valve plate and the valve stem are concentric, with a simple structure. It is suitable for low pressure, normal temperature, and occasions without strict sealing requirements (such as water supply systems).

Double eccentric butterfly valve (single eccentric): The sealing performance is better than the midline type, suitable for medium pressure and medium temperature conditions.

Triple eccentric butterfly valve: The sealing surface is metal to metal, resistant to high temperature and high pressure, suitable for harsh working conditions (such as steam, oil and gas pipelines).

Classification by connection method:

Wafer type: compact structure, suitable for pipelines with limited space. 

Flange type: easy to install and disassemble, good sealing, suitable for high-pressure and large-diameter pipelines.

Welding type: used for high pressure or special media (such as chemical pipelines).

3. Material selection

Body Material:

Cast iron (low pressure normal temperature, such as grey cast iron, ductile iron).

Carbon steel (medium and high pressure, such as WCB).

Stainless steel (corrosive media, such as 304/316).

Special alloy (high temperature, strong corrosive conditions).

Sealing material:

Rubber (EPDM, NBR, etc.): for water, air and other non-corrosive media.

Polytetrafluoroethylene (PTFE): corrosion-resistant, high temperature resistant, suitable for chemical media.

Metal seal (stainless steel, alloy): high temperature and high pressure resistance, and it’s used for three eccentric butterfly valve.

4. Nominal diameter (DN) and pressure rating

Nominal diameter (DN): Match with the inner diameter of the pipeline，in order to avoid high flow rate ，as high flow rate  should lead to abrasion or noise.

Pressure rating: Selected according to the maximum working pressure of the system (e.g. PN10, PN16, Class150, etc.).

5. Operation

Manual operation: suitable for small diameter (DN≤300) or occasions where frequent operation is not required.

Electric actuator: used for automated control or remote operation (need to match the torque)

Pneumatic actuator: suitable for explosion-proof environment or rapid opening and closing (such as compressed air systems).

Hydraulic actuator: used for high torque, large diameter valves (such as hydropower stations).

6. Sealing level requirements

Leakage level (as per ISO 5208):

Centerline butterfly valves are usually Class VI (allowing slight leakage). 

The triple eccentric butterfly valve can reach Class V or zero leakage (metal hard seal).

Special sealing requirements: such as food grade, vacuum sealing, fireproof design, etc.

7. Installation and Maintenance

Installation space: For wafer-type butterfly valves, flange space must be reserved, and for flange-type válvulas mariposa, bolt operation space must be considered.

Maintenance convenience: The centerline butterfly valve has a simple structure and is easy to maintain, while the triple eccentric butterfly valve has a long service life but complex maintenance.

Flow direction requirements: Some butterfly valves have flow direction restrictions (such as double eccentric and triple eccentric types).

8. Industry standards and certification

Standard Specifications:

National standard (GB), American standard (API 609, ANSI), European standard (EN), Japanese standard (JIS).

Industry Certifications:

Fire protection (FM/UL), drinking water (NSF), explosion-proof (ATEX), petrochemical (API), etc.

9. Economic evaluation

On the premise of meeting performance requirements, we need to compare the initial purchase cost、maintenance cost and life cycle cost comprehensively.

For example: The triple eccentric butterfly valve has a high initial cost, but has a long life and is suitable for long-term operation in harsh working conditions.

10. Typical selection examples

Water treatment system (normal temperature and pressure): center line butterfly valve (EPDM seal) + cast iron valve body.

Chemical pipeline (corrosive media): flanged three-eccentric butterfly valve (316 stainless steel body + PTFE seal).

Steam system (high temperature and high pressure): triple eccentric metal sealed butterfly valve + electric actuator.

11. Items need attention

Avoid using butterfly valves for high-viscosity media (such as asphalt) or media containing a large amount of solid particles (which are prone to jamming ).

Large diameter butterfly valves need to check the valve stem strength and actuator torque.

In throttling conditions, the risk of cavitation and vibration must be considered. 

Through the systematic analysis of the above steps, it can be ensured that the butterfly valve selection meets the actual needs, and also consider performance, reliability and economy.

ZZJG Valve provides the above information on how to select butterfly valves. If you want to know more about butterfly valve selection, please contact us via WhatsApp(+86 18135671959) or Email([email protected]).