How To Choose A Corrosion Resistant Valve
Selection of a corrosion resistant valve requires detailed understanding of the fluid, conditions of operation, piping system and the desired control function.
1. Define the Fluid.
Start with defining the exact fluid. Determine whether the system deals with acids, alkalis, solvents, salts, waste water, chemicals, gases, or mixed fluids. Chemical concentration and composition are important, as same material can act differently in different environments.
2. Check Chemical Compatibility
Check wetted parts, such as valve body, seat, diaphragm, stem, seals, and other for chemical compatibility. A material described as corrosion resistant does not mean that it will work in every chemical environment.
3. Calculate the Pressure
Note the normal operating pressure, maximum pressure, differential pressure and all possible pressure surges. Select the valve with appropriate pressure rating.
4. Search for the Temperature
Check min/max temperatures of the fluid and ambient temperature. Temperature plays an important role with regard to plastics, elastomers, coatings and other materials.
5. Calculate Flow Requirements
Determine the flow rate and pressure drop required. Size the valve according to the real process requirements, not just the pipe diameter.
6. Select the Valve Type
Different valve designs, such as ball, butterfly, diaphragm, globe, etc. have different operating characteristics. Select the design according to the fluid, flow requirements, installation space and control function.
7. Select the Connection
Verify threaded, flanged, wafer, union, socket or other connection requirements Verify compatibility with existing piping system
8. Define actuation
For automated systems, define whether actuation is required, manual, electric, pneumatic or other. Check actuator torque, speed of operation, duty cycle, voltage and control signals.
9. Consider the Environment
Humidity, dust and outdoor exposure, chemical vapors, vibration and installation temperature.
10. Check Maintenance Requirements.
Define the valve inspection, replacement of seals, cleaning and servicing requirements.
Prior to the order, provide the manufacturer with detailed fluid and operating data to allow verifying the valve configuration against the application.
Tips to Avoid Common Mistakes in Designing Corrosion Resistant Valves
1. Do Not Select Materials for General Corrosion Resistance Only
Verify compatibility with specific chemical, concentration, temperature and exposure time.
2. Don’t Forget about Seal Material
Even corrosion resistant valve body can fail if the seat or seal is chemically incompatible.
3. Don’t Select the Valve According to Pipe Size Only
Flow rate, pressure drop, valve coefficient and process requirements should be considered.
4. Don’t Forget about Temperature
Temperature can affect chemical compatibility and mechanical properties of plastics and elastomers.
5. Don’t Forget about Pressure Surges
Water hammer and other process transients can be much higher than normal operating pressure.
6. Don’t Oversize the Valve
Too large valve will complicate flow control and increase system cost.
7. Don’t Forget about Actuator Requirements
For automated valves, actuator torque, voltage, control signal, operating frequency and duty cycle should be compatible with the valve.
8. Don’t Forget about Environmental Requirements
Moisture, dust, vibration, chemical vapors and outdoor exposure can affect valve performance.
9. Don’t Combine Chemically Incompatible Materials
Consider entire wetted-material combination, not just valve body.
10 Application Verification Don’t Skip
Prior to purchase, verify final specification with valve manufacturer, especially for concentrated or unusual chemicals.
