General Questions

A soft seat safety relief valve typically uses an elastomer material, such as Silicone, FKM (Viton™), EPDM (Teflon™), Nitrile (Buna-N) or PTFE as the sealing material in the internals of the valve depending on the compatibility of media flowing through the valve.

Use soft seat valves 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, Factory Standard does not ensure bubble-tight seats, regardless of seat material.

A hard seat safety relief valve is a metal-to-metal seated valve, which usually uses a metal disc or ball as the internal sealing surface against the orifice or internal passageway in a safety relief valve.

A hard seat safety relief valve is excellent in corrosive or extremely high temperature applications.

A safety relief valve is designed to open and relieve excess pressure from pressure vessels, boilers, or other industrial equipment and to reclose and prevent the further release of media (air, gas, steam or liquids) after normal conditions have been restored. 

ASME B16.34 Valves Flanged, Threaded and Welding End applies to new construction. It covers pressure-temperature ratings, dimensions, tolerances, materials, nondestructive examination requirements, testing, and marking for cast, forged, and fabricated flanged, threaded, and welding end and wafer or flangeless valves of steel, nickel-base alloys, and other alloys Wafer or flangeless valves, bolted or through-bolt types, that are installed between flanges or against a flange are treated as flanged-end valves. Alternative rules for NPS 2½ and smaller valves are provided.

Intended for manufacturers, owners, employers, users and others concerned with the specification, buying, maintenance, training and safe use of valves with pressure equipment, plus all potential governing entities.
Careful application of these B16 standards will help users to comply with applicable regulations within their jurisdictions, while achieving the operational, cost and safety benefits to be gained from the many industry best-practices detailed within these volumes.

This standard is to be used in conjunction with equipment described in other volumes of the ASME B16 Series of Standards as well as with other ASME standards, such as the Boiler and Pressure Vessel Code and the B31 Piping Codes.

The lowest operating temperature varies between valves due to seat material. The lowest temperature that can be applied is -250°F.

The National Board of Boiler and Pressure Vessel Inspectors is the third party that certifies our manufacturing/quality program. They also test and certify flow on each code valve periodically.

The NB Certificate and Samples of the CoC are available in the Quality section of the Downloads area. Downloads Page The National Board “Redbook” or the Published List of Certified Valve Manufacturers also contains this information. We are listed as the F.C. Kingston Company (KNG).

All the valves are listed there in Section B, Page 40 of 88.

Kingston Check Valves designed for lubricated compressor applications will not perform in non-lubricated systems. Internal parts on these valves require lubrication provided to the compressor. If installed on an oil-free compressor these valves will wear prematurely and possibly cause damage to the compressor.

The Model 205, for example, has an internal piston to dampen the hammering effects of some compressors. The piston and sleeve are precision engineered to fit snugly and require oil to keep from overheating and wearing quickly or seizing.

Yes. Liquid Applications: Liquids tend to be incompressible, meaning they cannot be compressed like air. Liquids can be under pressure but as soon as the volume changes they immediately lose all pressure (pressure goes to zero). There are three accepted definition in the industry for liquid applications. They are: start to leak, first steady stream and full flow. For Liquid applications – Kingston defines “Set Pressure” as the first steady stream of flow out of the valve.

Back pressure reduces set pressure on a one-to-one basis, i.e., a valve set at 100 psig subjected to a backpressure at the outlet of 10 psig will not actuate until system pressure reaches 110 psig. Back pressure drastically reduces capacity; typically, backpressure of 10% of set pressure will decrease capacity by 50%.

Specific capacity reduction should be determined by the user on a case-by-case basis by flow testing. Back pressure in excess of 10% of set pressure is not recommended.

Section VIII UG-136(a)(3) states, “Each pressure relief valve on air, water over 140 degree, or steam Service shall have a substantial lifting device which when activated will release the seating force on the disk when the pressure relief valve is subjected to a pressure of at least 75% of the set pressure of the valve.

Code Case 2203 states the lifting device may be omitted provided: The user has a documented procedure and an associated implementation program for the periodic removal of the pressure relief valves for inspection and testing, and repair as necessary.

The omission is specified by the user. The user shall obtain permission to omit the lifting device from the authority having jurisdiction over the installation of pressure vessels.

No. Gage pressure (psig) is used to set valves so the effects of weather and altitude on set pressure can be ignored.

It may not be. Warn/simmer or seat leakage is sometimes mistaken for set pressure. Visible or audible leakage or system pressure drop is not set pressure. The correct definition of set pressure is: For liquid service, first vertical steady stream. For liquid service, first vertical steady stream.

For some valves in air/gas service (Models 230, 330, 330S, 333S, C776), First audible. Variance of set pressure is allowed, i.e., a Section VIII air valve with a nameplate of 100 psig set pressure may open from 97 psig to 103 psig but will be factory set around 102 psig.