**Important notes regarding ASME valves**

Example part: CV4-70 (1/2″ NPT RELIEF VALVE SET TO 70 PSI POP-OFF)

Set: 70 psi ‘POP’ setting is +/-3% of 70 psi, +/-2 PSIG below 70 PSIG

Working pressure: 10% Less than Set Pressure (or with valves less than 50 psig set pressure, within 5 psig of given set pressure.)

In regards to what may be perceived as ‘leaking’ or defective valves:

It is normal for spring-operated safety valves to exhibit leakage or simmer/warn, as the operating pressure approaches the nameplate set pressure, typically in the 80%-90% range of nameplate set pressure.

The ASME Boiler and Pressure Vessel Code does not require a specific seat tightness requirement. A certain level of leakage is allowed.

Seat tightness standards are as follows:

Factory Standard Seat Tightness Performance:  Hard Seat Valves – no audible leakage at 20% below nameplate set. Soft Seat Valves – no audible leakage at 10% below nameplate set.

At very low set pressures (20 psi and below), the ratio of the downward spring force as compared to the upward pressure force is very small. In these cases, it may be impossible to achieve seat tightness.

Soft Seat Valves: Use for superior seat tightness in applications which fall within the soft seat material temperature limitations. Although soft seat valves will typically provide a higher degree of seat tightness than metal seats,

*please note*: factory standard does not ensure bubble-tight seats, regardless of seat material.

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