Circle Valve Technologies Inc.
1533 Gehman Road
Harleysville, PA 19438
Toll Free: 800-645-6733 | Phone: 267-933-6300 | Fax: 267-933-6305|
email: [email protected] 
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Item # D520N-2M, D500 Series ASME Safety Relief Valves 15 to 150 psig
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List Price QUOTE
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Features- D500 Series features cap design
- MD500 Series features cup design with manual override ring
- Zero leakage from 0 psi up to 70% of the marked set pressure
Please specify ‘ASME’ when placing your order.
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Safety Relief Valves
An automatic pressure relieving device actuated by the static pressure upstream of the valve, which opens in proportion to the increase over the opening pressure.
Start-to-Leak Pressure
The pressure at the valve inlet where the relieved fluid is first detected (on the downstream side of the seat) before normal relieving action takes place
Opening Pressure (Set Pressure)
The valve inlet pop point pressure at which there is a measurable lift or discharge becomes continuous as determined by seeing, hearing or feeling. In the pop type of safety valve, it is the inlet pressure at which the valve opens, allowing a larger amount of fluid as compared with corresponding valve movements at higher or lower pressures
Note: A safety relief valve is not considered to open when it is simmering at a pressure just below the popping point even though the simmering may be audible. This set pressure distinguishes our ASME relief valves from our standard relief valves whose cracking pressure indicates initial flow.
Relieving Pressure
(Opening pressure plus overpressure) The pressure measured at the valve inlet at which the relieving capacity is determined.
Closing Pressure
(Reseat pressure) The pressure measured at the valve inlet, at which the valve closes, flow is substantially shut off , and there is no measurable lift.
Seal-off Pressure
The pressure (measured at the valve inlet) after closing at which no further gas is detected at the downstream side of the seat.
Operating Pressure
The actual pressure at which a vessel is maintained in normal operation.
Accumulation
Pressure buildup or overpressure beyond the set pressure of a safety relief valve, at which capacity flow is rated. Capacities are usually based on 10% accumulation.
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- Before installing a new safety relief valve, we recommend that a pipe tap be used to assure clean-cut and uniform threads in the vessel opening and to allow for normal hand engagement followed by a half to one turn by wrench.
- Avoid over-tightening as this can distort the valve seat.
- Avoid excess “popping” of the valve. Safety relief valves should only be operated often enough to assure they are in good working order.
- Apply only a moderate amount of pipe compound or tape to the threads, leaving the first thread clean parts.
- Don’t oversize the valve, as this may cause chatter resulting in rapid wear of the moving parts.
- Avoid wire, cable, or chain pulls for attachments to levers that do not allow a vertical pull. The weight of these devices should not be applied to the safety relief valve.
- Avoid having the operation pressure too near the valve set pressure. A minimum differential of 10% is recommended.
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For Your Safety
It is solely the responsibility of the system designer and user to select products suitable for their specific application requirements and to ensure proper installation, operation, and maintenance of these products. Material compatibility, product ratings and application details should be considered in the selection. Improper selection or use of products described herein can cause personal injury or property damage.
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