How to choose the matching valve for chemical pumps
The selection of matching valves for chemical pumps requires a comprehensive analysis of process parameters, medium characteristics, valve type, material adaptability and operating conditions. The following are specific suggestions:
I. Clarify process parameters and medium characteristics
1. Flow and pressure
Select the valve nominal diameter (DN) and nominal pressure (PN) according to the rated flow and pressure range of the chemical pump. For example, when conveying high-viscosity media (such as resin), you need to choose a full-bore ball valve or a large-diameter gate valve to reduce flow resistance; when conveying high-pressure gas, you need to choose a high-pressure stop valve or a special high-pressure ball valve. For example, if the pump outlet pressure is 10MPa, a PN16 or PN25 valve should be selected.
2. Chemical properties of the medium
Corrosive media: Corrosion-resistant valves are preferred, such as fluorine-lined valves (lined with PTFE, PFA, etc.), Hastelloy valves or titanium alloy valves.
High-temperature media: Choose high-temperature resistant valves, such as ceramic valves (temperature resistance ≤1200℃) or high-temperature alloy valves (such as Inconel 625).
Medium containing particles: Use wear-resistant valves, such as ceramic ball valves, metal hard-sealed ball valves or plug valves to prevent the valve core from being worn by particles.
Flammable and explosive media: Use explosion-proof electric actuators or pneumatic actuators that comply with ATEX or IECEx standards.
Ⅱ. Valve type selection
1. Ball valve
Applicable scenarios: occasions with rapid opening and closing or full-diameter requirements, such as pipeline switching and emergency cut-off.
Advantages: small flow resistance, rapid opening and closing, and reliable sealing.
Type selection:
Soft-sealed ball valve (PTFE/PFA lining): Applicable to non-corrosive media.
Hard-sealed ball valve (metal to metal): Applicable to high temperature, high pressure or abrasive media.
2. Gate valve
Applicable scenarios: fully open or fully closed occasions, such as the main valve at the pump outlet.
Advantages: small flow resistance, and the sealing surface is not easy to wear.
Disadvantages: poor adjustment performance and long opening and closing time.
3. Butterfly valve
Applicable scenarios: large-diameter, low pressure difference occasions, such as circulating water pipelines.
Advantages: compact structure, light weight, low cost.
Disadvantages: general sealing performance, not suitable for high temperature and high pressure.
4. Check valve
Applicable scenarios: prevent medium backflow, such as pump outlet.
Type selection:
Lift check valve: suitable for vertical pipelines.
Swing check valve: suitable for horizontal pipelines.
Wafer check valve: suitable for large-diameter pipelines.
III. Material selection
1. Valve body material
Carbon steel (WCB): suitable for non-corrosive media such as water and steam.
Stainless steel (304/316L): suitable for weakly corrosive media such as food and pharmaceuticals.
Hastelloy (C276/C22): suitable for strongly corrosive media such as concentrated sulfuric acid and hydrochloric acid.
Titanium alloy (TA2): suitable for seawater and chloride ion media.
2. Sealing material
Soft seal: PTFE, PFA, EPDM (suitable for non-corrosive media).
Hard seal: metal to metal (STL/STL, STL/WC) (suitable for high temperature, high pressure, and abrasive media).
IV. Operating conditions and actuators
1. Manual operation: suitable for small-caliber, low-frequency opening and closing occasions.
2. Electric actuator: suitable for remote control and high automation occasions, explosion-proof level (such as ExdⅡBT4) should be considered.
3. Pneumatic actuator: suitable for fast opening and closing, explosion-proof occasions, and air filter pressure reducing valve and positioner should be equipped.
V. Other considerations
1. Anti-static design: When conveying flammable and explosive media, the valve must have anti-static function (such as anti-static spring device of ball valve).
2. Fireproof design: key parts must comply with API 607 or API 6FA fireproof standards.
3. Bidirectional sealing: For occasions requiring bidirectional sealing (such as vacuum systems), bidirectional sealing valves should be selected.