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FAQ
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What information is required to properly size and select a valve?
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To ensure proper selection, the following information will be needed:
1. Connection sizes (in and out), and types (male, female, flanged; 125#, 150#, 250#, 300#, etc.)
2. Material of construction
- Bronze
- Iron
- Steel
- Stainless Steel or Other
3. Set Pressure (PSIG)
*Set pressure, generally as pounds per square inch (psig), is the gauge pressure at which a safety valve visibly and audibly opens or a setting at which a relief valve discharges a continuous stream of liquid.
4. Temperature (Operating and/or Relieving)
5. Backpressure (If any, please indicate constant or variable)
6. Service (steam, air, gas, etc., including any applicable codes or standards)
7. Capacity required, if available (GPM, SCFM, LBS/HR, etc...)
*Required capacity is the percentage of measured flow at an authorized percent overpressure permitted by the applicable code. Rated capacity is generally expressed in LBS/HR, SCFM, and GPM.
- LBS/HR - Pounds per hour (steam flow)
- SCFM - Standard cubic feet per minute (air or gas flow)
- GPM - Gallons per minute (liquid flow)
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What is Allied Valve, Inc.'s standard warranty policy?
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Allied offers a one year warranty on all valves, new or reconditioned, and extends the factory warranty to all customers on new products. All reconditioned valves are subject to the same stringent quality control and serializing standards used to handle new ASME code safety valves. Upon completion of service, Allied locks the external adjustments of all safety valves with lead seals bearing the Allied logo. As a further assurance to our customers, Allied carries product liability insurance.
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What 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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What is Allied Valve Inc.'s standard return policy?
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- All returns must be issued a Return Authorization (RA) number, which can be obtained by contacting our inside sales department.
- A restocking fee may apply. Please contact our inside sales department for our standard return fees and/or return instructions.
- All valves being returned for credit are subject to a final inspection, where it will be determined if credit can be issued.
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Is there any type of program available to help me with the selection of a valve?
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Dresser/Consolidated offers a Pressure Relief Valve Sizing and Selection program in which fields are entered with the process data provided by the customer. This process data includes operating and set pressure, operating and relieving temperatures, required capacity, molecular weight, ratio of specific heats and compressibility factor (for steam, vapor or gas valves) and specific gravity and density (for liquid valves). Once this information is entered, the program selects the appropriate valve for your application.
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How do I know which valve to select for my application?
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Choosing the correct valve for your application can be difficult. There are numerous factors involved in the selection process, However, our customer service department, which has over 30 years of experience, is available to assist you in choosing the right valve. Please contact us for support in selecting the proper valve for your application.
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What kind of certified documents can Allied Valve, Inc. provide to their customers?
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We can provide numerous documents to our customers that include the following:
- Certification Test Report
- Certificate of Conformance
- Seat Leakage Test Report
- Hydrostatic Test Report
- Certified Mill Test Reports
- Certified Drawings
**All documentation must be requested at the time of order. Depending on the document type or test performed, charges may apply.
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ValvKeep is a database that stores historical data that can be used to anticipate future service needs. This allows for a manageable maintenance schedule which will reduce downtime for our customers. ValvKeep can be accessed via the internet from anywhere in the world.
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Why is ValvKeep not working?
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If you are experiencing problems with ValvKeep, please try viewing the page using Internet Explorer as your web browser.
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How often should I test / inspect my valve?
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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. A monthly "try lever test" is recommended for valves equipped with a lift lever to ensure the disc is free. The valve should be subjected to at least 75% of set pressure when performing this test. Allow the valve to snap shut for best leak-tight performance. Use appropriate personal protection equipment (for example hearing, eye and temperature protection) as steam and/or high temperature high pressure media may be discharged from the outlet and any other openings in the valve such as vent and drain holes. A "try lever test" for High Temperature Hot Water boilers can be performed only when water temperature is below 200 oF.
The ASME Boiler and Pressure Vessel Code does not require nor address testing installed valves. The only thing the code 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 140 degrees F, 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.
Section I - PG-71.2 - Every safety valve or safety relief valve shall be connected so as to stand in an upright position, with spindle vertical. EXCEPTION: PEB-15.3 (Electric Boilers) – Safety and safety relief valves shall be mounted in accordance with PG-71.2 with the spindle vertical. Electric boilers that do not exceed the diameter, volume, or pressure limits of PMB-2, may have a spring-loaded safety or safety relief valve(s) installed in other than the vertical position, provided that:
- The valve design is satisfactory for such position
- The valve is not larger than NPS ¾ (DN20)
- The maximum angle of deviation from vertical does not exceed 30 deg
- The nozzle location is such that no material that could interfere with the operation of the valve can accumulate at the valve inlet
- The discharge opening of the valve body and discharge piping is oriented so that drainage is adequate
Section IV - Article 7 HG-701.1 - Safety valves and safety relief valves shall be installed with their spindles vertical. Article 8 HLW-810.2 - Safety relief valves shall be installed with their spindles upright and vertical with no horizontal connecting pipe, except that, when the safety relief valve is mounted directly on the water heater vessel with no more than 4 in. (102 mm) maximum interconnecting piping, the valve may be installed in the horizontal position with the outlet pointed down.
Section VIII - APPENDIX M-12 - Spring loaded safety and safety relief valves normally should be installed in the upright position with the spindle vertical. Where space or piping configuration preclude such an installation, the valve may be installed in other than the vertical position provided that:
- The valve design is satisfactory for such position
- The media is such that material will not accumulate at the inlet of the valve
- Drainage of the discharge piping is adequate
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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 system 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 the Kunkle Valve Factory and API-527 Seat Tightness Performance Standards, both of which can be found in the Technical Reference Catalog and in the Data Supplement, summarized as follows:
Factory Standard Seat Tightness Performance:
- No visible (no audible for air service) leakage for 15 seconds (30 seconds for liquid or Section IV steam service) at 20% below nameplate set, or 5 psig below nameplate set, whichever is greater. EXCEPTION: Section IV steam service is checked at 12 psig.
API-527 Standard Seat Tightness Performance:
A Functional Test Report (FTR) is automatically provided for valves ordered to API-527.
- Air/Gas and Liquid Service criteria are dependent upon seat material:
- Soft seat
- Air/Gas Service - Bubble-tight for 1 minute at 10% below nameplate set pressure or 5 psig below nameplate set, whichever is greater.
- Liquid Service - No visible leakage for 1 minute at 10% below nameplate set pressure or 5 psig below nameplate set, whichever is greater.
- Metal seat
- Air/Gas Service - 40 bubbles/minute for D and E orifice, 20 bubbles/minute for orifice larger than E, at 10% below nameplate set pressure or 5psig below nameplate set, whichever is greater.
- Liquid Service - 10 cc/hr per inch of inlet size (10 cc/hr for below 1" inlet size) at 10% below nameplate set pressure or 5 psig below nameplate set, whichever is greater.
- Steam Service criteria is independent of seat material:
- No visible leakage for 1 minute at 10% below nameplate set pressure or 5 psig below nameplate set, whichever is greater.
Please note API-527 is not available on Air Service for:
- Plain Lever J Orifice Model 900 Series
- Model 6000 J Orifice
- Plain Lever Model 900 Series above 444 psig nameplate set pressure.
- Model 230/330/333/333S
In addition, at very low set pressures, 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 these levels of seat tightness, i.e. a ½” valve set at 6 psig would be tested at 1 psig, resulting in a sealing force of just 1/10th of a pound holding the seat together against the disc. Also, valves set at 5 psig or below cannot adhere to these leakage requirements by definition, i.e. a valve set at 5 psig cannot be tested for leakage at 0 psig.
Use soft seats for superior seat tightness, assuming the application falls within the soft seat temperature limitations. Although soft seats 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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Operating Gap
A minimum operating gap of 10% between the system operating pressure and the safety valve’s nameplate set pressure should be maintained. Since direct spring operated safety valves may “simmer” or “warn” at 90% of the nameplate set pressure, and since the factory standard leak test is 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 Steam or most valves in Air/Gas service, "pop" (an audible loud pop)
- 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 (see catalog or the appropriate section of the ASME Boiler and Pressure Code), although we try to set on the high side of the tolerance (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.)
Gage issues may lead to incorrect reporting of set pressure. Ensure the gage is within calibration and is accurate for the pressure being measured. The gage should be upstream of the valve, close to the valve inlet, with a large connection, with no bends and as short a run of pipe as possible, for better accuracy. Rapid increases in system pressure (more than 2 psig/second, water hammer, reciprocating pumps) can make the valve appear to be opening early because the gage cannot accurately report the pressure that the valve is exposed to.
Valves are factory set using standard conditions (i.e., ambient temperature, saturated steam, etc.) Many operating factors can cause a valve to open early before the system pressure reaches the valve nameplate set pressure, including high temperature and vibration, as is present in blowers, compressors, and reciprocating pumps. These conditions can be compensated for by using a "Cold Differential Set" (CDT), where the valve is factory set at a pressure higher than nameplate, and an auxiliary nameplate showing actual set pressure is attached. Superimposed back pressure may also be compensated for by using a CDT, in which case the valve is factory set at a pressure lower than nameplate, and an auxiliary nameplate showing actual set pressure is attached. It is up to the end user to determine the value of the CDT by experimentation or calculation, and must be specified on the order.
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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 140o F (60o C), 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 blowdown 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 blowdown for most valves is 15% to 30%, but cannot be guaranteed.
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