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Repair companies must be:
Experience
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What documents do Relief Device Repair Organizations have to maintain?
A QC manual and a documented training program.
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What is the primary factor for setting the relief device interval?
Performance
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Who can set the relief device interval?
Inspector, engineer, or qualified other.
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What is the maximum relief device interval for typical service? Clean, non-corrosive, non-fouling service?
5 years for typical and 10 years for clean
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Directions for setting the interval is found where?
The owners QA manual
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Every vessel should have at least one relief device set at?
MAWP
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Safety valves are normally used in what two services?
Steam or air
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Relief valves are normally used what services? These services are also called what fluids?
Liquid services (Incompressible fluids)
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Safety-relief valves can be used in what two services?
Liquid or vapor service
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When is a balanced bellows safety relief valve generally used?
When there is variable back pressure.
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Pilot operated valves are useful when there is? (Two answers)
When a large relief device is needed and if there is a small difference between the operating and set pressure.
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How smooth are relief device's seating surfaces?
3 light beads/bands
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Relief devices should be shipped in what position?
Upright
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What some of the different pressure-relief valves?
Safety valve, relief valve, conventional safety-relief valve, balanced safety-relief valve, and pilot-operated pressure-relief valve.
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Safety Valves
How does the over pressure system work?
What services are they used in?
What are the limitations?
- -When over pressured the safety valve opens completely.
- -Used in air and steam services (Compressible fluids)
- -Should not be used in corrosive services, installations that impose back pressure,
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Relief Valves
How does the over pressure system work?
What services are they used in?
What are the limitations?
- -When over pressured the safety valve opens in proportion to the pressure increase. They typically reach full lift at 10% or 25% over pressure.
- -Typically used for incompressible fluids (liquids)
- -Should not be used in steam, air, gas, or other vapor services and installations that impose back pressure.
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Safety-Relief Valve
What service can these be used in?
How does the over pressure system work?
- -These valves can be either used as a safety or relief valve depending on the application.
- -When used in vapor/gas service, full lift normally happens at 10% over pressure. When in liquid service, full lift occurs at approx. 10% or 25%.
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Conventional Safety-Relief Valve
How does the over pressure system work?
What services are they used in?
What are the limitations?
- -The opening pressure, closing pressure, etc are affected by changes in the back pressure.
- -Used in services that handle flammable, hot, or toxic material.
- -Should not be used where the total built-up back pressure is variable and exceeds the allowable over pressure.
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Balanced Safety-relief Valve
How does the over pressure system work?
What services are they used in?
What are the limitations?
- -Balanced safety valves incorporate a bellows or other means to minimize the effect of back pressure.
- -They are used in services such as flammable, hot, or toxic material (Gas, vapor, steam, air, or liquid services) where high back pressures are present at the valve discharge.
- -Should not be used on BPVC Section 1 Steam boiler drums or superheaters.
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Pilot-operated Pressure-Relief Device
How does the overperssure system work?
What services are they used in?
What are the limitations?
- -The major relieving device or main valve is combined with and controlled by a self-actuated pressure-relief valve(pilot).
- -Used where a large relief area and/or high set pressures are required, where low differential exists between the normal vessel operating pressure and the set pressure, where back pressure is very high and balanced design is required.
- -Limitations are services that are dirty or have a potential for fouling or solidification, viscous service, vapors that polymerize, etc. Anything that can clog the valve.
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