Valve Sizing
Torito Chemical Dec 26 - Jan 16
Selection and Sizing of Pressure Relief Valves
Ultimate Pressure Relief Handbook
Full Emerson Control Valve Handbook
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.
You can:
- View the performance of one regulator in up to four different applications
- Compare the performance of up to four different regulators in the same application
- View any combination of regulators and applications, adding up to four total, on the same graph
- This calculator can be used to help select a valve with enough flow capacity for a given application.
- The valve flow coefficient (Cv) is a convenient way to represent flow capacity of a valve across a range of fluids and process parameters.
- The Cv calculator will calculate either Cv or flow using the supplied additional parameters of fluid, inlet and outlet pressure, and fluid temperature. - The calculations can be performed for either liquid or gas flow.
- Choosing a valve with a Cv value sufficiently larger than the calculated Cv will help provide expected flow performance.
Received from: https://www.emerson.com/documents/automation/pressure-relief-valve-engineering-handbook-en-gb-4244934.pdf
