Valve Sizing
Selection and Sizing of Pressure Relief Valves
What is the purpose of a regulator
- Help to main or control desired pressure and flow in response to system changes
- Control upstream or downstream pressure in response to changes in the system
- Changes include fluctuation in flow, pressure, temperature etc
What are the problems of not choosing the correct size of your regulator
- Inefficiency
- Poor Performance
- Frequent troubleshooting
- Potential Safety Hazards
How do pressure regulators differ from valves
- Valves: Control system flow rates and do not self-adjust
- Regulators: Control pressure, not flow, and are self-adjusting
Two Types of Regulators
-
Pressure Reducing
- Sense outlet pressure
- Control their own downstream pressure
-
Back - Pressure
- Sense inlet pressure and control pressure from upstream
Important Characteristics to Consider: System Flow, System Pressure, System Temperature, Process Sensitivity and System Media
System Flow
- Determine rate of flow in your system
- Determine sizing of regulator components
- (For ex.) Larger diaphragm or piston if better to control lower-pressure applications
System Pressure
- Selection must be appropriately rates for (i) Maximum (ii) Minimum and (iii) Operating System Pressures
System Temperature
- Joule - Thomson Effect can cause rapid cooling due to pressure drops
- One must be confident that the choice in regulator can stand up to the typical expected operating conditions and environmental factors
Process Sensitivity
- Sensitivity of your process plays a role in determining the best mode of control to choose in your regulators
- Most regulators are either spring-loaded or dome-loaded
- Spring Loaded
- Controlled by operator turning an external knob
- This controls the spring's force on the sensing element
- Dome Loaded
- Use fluid pressure from within the system to provide the set pressure on the sensing element
System Media
- Understand material compatibility between all elements of your regulator and your system media
[Note!]: Your regulator supplier should be able to provide you with sizing information, pressure and flow requirements, temperature ranges, and the correct mode of control for your system needs.