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is the proper way to install a safety or safety-relief valve?
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Safety and safety-relief valves should be installed vertically with the drain holes open or piped to a convenient location. All piping must be fully supported.
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How often should I test/inspect my valve?
Maintenance should be performed on a regular basis. An initial inspection interval of no longer than 12 months is recommended. The user must establish an appropriate inspection interval depending on the service conditions, the condition of the valve and the level of performance desired.
The ASME Boiler and Pressure Vessel Code does not require nor address testing installed valves. The only thing the codes states are design and installation requirements, such as some valves must have a lifting lever. For instance for section VIII:
“Each pressure relief valve on air, water over 1400F, 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. ”
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What mounting orientation should be used to install a safety valve?
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Installing a safety valve in any position other than with the spindle vertical and upright may adversely affect performance and lifetime.
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Why is there a hole in the valve body?
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This drain hole is required on some models by the ASME Boiler and Pressure Vessel Code. It is intended to prevent any condensate from accumulating in the body that may freeze or corrode internal valve parts and prevent the valve from opening. The drain hole should be piped away to safely dispose of any discharge or condensate.
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Which end should be connected for vacuum valves?
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This is often a confusing topic. The correct installation often looks backwards from what appears to be correct. A paper instruction tag illustrating the proper connection is attached to each valve. Vacuum valves should have the NPT threads that are cast integral to the body attached to the vacuum source. See the assembly drawing for additional clarification.
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What set pressure should the valve be set to open?
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Typically, the valve should be nameplate set to open at the MAWP (Maximum Allowable Working Pressure) of the vessel the valve is intended to protect. There is a tolerance to actual set pressure, which means a valve set at 100 psig nameplate may open slightly above or below 100 psig. Consult the current ASME Boiler and Pressure Vessel Code for tolerance classes and special situations when the set pressure may be different than the MAWP.
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Why is my valve leaking?
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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 per manufacturers’ published literature.
Kingston defines seat tightness standards as follows:
Factory Standard Seat Tightness Performance:
o Hard Seat Valves – no audible leakage at 20% below nameplate set.
o 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.
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.
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How high can my system pressure be before my valve opens?
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Maintain a minimum operating gap of 10% between the system operating pressure and the safety valve’s nameplate set pressure. Since direct spring operated safety valves may “Simmer” or “Warn” at 90% of the nameplate set pressure, and since the factory standard leak test performed at 80% of nameplate set pressure, better seat tightness performance can be expected with an operating gap of 20%.
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Why does my valve actuate/open early?
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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.
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Can I use a Section I steam valve in a Section VIII steam application?
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Yes, Section I valves have more stringent setting blowdown requirements and may be used in Section VIII steam applications since they meet all the requirements as specified in Section VIII UG-125(a) “Pressure Relief Devices,” which states pressure relief devices must be “In accordance with the requirements of UG-125 through UG-137.” In addition, UG-125(b) actually specifies that even unfired steam boilers MUST use a Section I Pressure relief device.
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Does altitude affect set pressure?
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No. Gage pressure (psig) is used to set valves so the effects of weather and altitude on set pressure can be ignored.
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Under what conditions may the lift lever or lifting device be omitted on Section VIII valves?
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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.
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How does back pressure affect valve set pressure and capacity?
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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.
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What is the blowdown of a Section VIII or non-code safety valve?
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The ASME Boiler and Pressure Vessel Code does not have blow down requirements for Section VIII (or non-code) valves. Blowdown may vary from less than 2% to more than 50%, depending on many factors including; valve design, dimensional tolerance variation, where the set pressure falls in the set pressure range of a spring, spring rate/force ratio, warn ring/guide settings, etc. Typical blow down for most valves is 15% to 30%, but cannot be guaranteed.
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Are Kingston Valves NACE Certified?
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At this time Kingston Valves have not been certified with the "The National Association of Corrosion Engineers" (NACE International).
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Are Kingston Valves ARRA Compliant?
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Many Kingston Valves meet the definitions called out in the Section 1605, "Buy American" of the American Recovery and Reinvestment Act (ARRA). For a full listing of these valves customers may download on our downloads page http://www.kingstonvalves.com/support/downloads.aspx
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Is there a difference in the definition of "Set Pressure" between Air & Liquid applications?
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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.
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The Model 205 cites its design for lubricated compressed air applications. Will it also function in oil-free compressed air?
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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.
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What is the difference between orifice and inlet size?
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The orifice diameter is the internal opening of the valve and is used to calculate the flow capacity of the valve. Metric or English makes no difference. It's the inside hole. The inlet size is the interface or the size/type of the threads where you attach the valve. As of publication Kingston Valves do not come in metric sizes, only NPT (National Pipe Thread)
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Chrome Ball Discontinued, Stainless Steel 'SS' added?
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Several years ago Kingston discontinued the chrome ball versions on all hard seated valves. Valves impacted by this change are listed below. The chrome-plated ball in each of these valves has been replaced by a stainless steel ball. To be clear the stainless steel ball is an equivalent in form, fit and function and has replaced completely the chrome plated ball in all sizes. Part numbers now show an additional "SS" to indicate this change and supersedes all previous part numbers. 100 103 112C 110C 118C 119C 125
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