T amp P and ASME Safety Relief Valves

T Amp P And Asme Safety Relief Valves-Free PDF

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Table of Contents,Temperature Pressure Relief Valves. General Information, The Role of Temperature and Pressure Relief Valves in Water Heater Safety 4. How T P Valves Work 4,Selecting T P Valves 4,ASME Pressure Steam Rating 5. CSA Temperature Steam Rating 4,Temperature Water Rating 5. Pressure Relief Settings 5,Installation 5,Drain Lines 6.
Boiling Points of Water 6,Thermal Expansion 6,T P Relief Valve Reinspection 7. Commercial T P Relief Valves, Series 40 140 240 and 340 Automatic Re seating T P Relief Valves 8. Series LL40XL and LLL40XL Extended Shank Automatic Re seating T P Relief Valves 9. Residential T P Relief Valves, Series 1L 1XL 10L and 100XL ASME Rated Self Closing T P Relief Valves for Water Heaters 10. Series SL100XL L100XL LL100XL and LLL100XL Extended Shank T P Relief Valves 11. Relief Shutoff Valves,Series 210 5 Gas Shutoff Valves 12. Model 3L Pressure Relief Valve 13,Model 53L Pressure Relief Valve 13.
Accessories,Series 100DT T P Relief Valve Drain Tubes 14. ASME Rated Pressure Relief Valves,General Information. The Role of ASME Rated Pressure Relief Valves in Water Heating Systems 15. How ASME Rated Valves Work 15,ASME Boiler and Pressure Vessel Code 15. Installation 15,ASME Water Pressure Relief Valves,Series 174A 374A 740 16. General Information, The Role of Temperature and Pressure Relief Valves in Water Heater Safety.
An exploding 30 gallon water heater has,the force of about one pound of dynamite. and has the power to destroy a house,and injure or kill those inside Thankfully. explosions have been significantly,reduced because temperature and. pressure T P relief valves are now being,used nationally to protect water heaters. from explosion T P relief valves when,installed properly prevent high water tem.
peratures which can cause flashing of,hot steam at faucets or any water outlets. in the system or cause an explosion,And they prevent high pressures which. can damage the water heater system,piping or components. How T P Valves Work, T P relief valves are two in one devices Second they respond to excessive tem. responding to both excessive pressures perature When the temperature of the. and to excessive temperatures in a water water in the water heater reaches 210 F Hottest. heater These are abnormal and potentially the T P relief valve s internal thermostatic water. temperature, dangerous conditions element expands lifting the valve s disc here.
First they respond to excessive pressure off its seat to discharge the overheated. by opening at the pressure set point of the water This allows cooler water to enter. valve typically 150psi to prevent further the tank and moderate temperatures. pressure increase When a relief valve is When the temperature returns to a safe. dripping it is typically due to thermal level under 210 F the thermostat con. expansion When water is heated it tracts allowing the loading spring to. expands This causes excess pressure in reseat the valve At this point the automat. the system When the T P relief valve ic temperature relieving element is ready Cold water. enters here, senses this excess pressure it opens to protect the system again If a T P relief. relieving the thermal expansion and valve is relieving a high volume of water it. returning the pressure back to normal is due to excessive water temperature. conditions an unsafe water heater condition,Refer to page 6 for important safety information. Selecting T P Valves CSA Temperature Steam,To select a T P valve some basic applica Rating. tion factors must be considered sizing The CSA temperature steam rating the. location in the water heater and draining ww, w w a tt s c o m Code method used under ANSI standard. Sizing the valve is based on ensuring that Model SER Z21 22 used nationally for sizing relief. the valve discharge rating is in excess of Number NO 0104. M7 STD Z21 22 valves The rating is obtained initially on a. the BTU input as indicated on the manu WATTS EXT test tank where 15psi of steam pressure. facturer s label on the heater The valve Pressure 3 in is accumulated Under these conditions. Setting 4 100XL 4, must be capable of discharging more the thermostat has opened the valve and.
BTU s than the heater is capable of putting,SET 75 PSI210 F. MAX HTR INPUT TEMP,STM THERM EXP WTR,the steam flows through the orifice into an. into the water CSA B T U HR RATING accumulating tank where it is measured. 105 000 C US,and translated into a valve rating This is. tts co CSA PRESS STEAM B T U HR the safest form of rating relief valves. Hr Mfg Cert Bym W, BT ed AN 21 22 Rating ASME because it takes into consideration the. AT elief V harl Ceasn,ax erm Exp Wtr 0,fact that no water pressure is available.
CANADIAN REGISTRATION NO,OG7543 5C to the heater Therefore it covers all. potential elements that could affect the,OG7543 relieving capacity. 7 S emp Steam M,150psi 210 F Sample T P Valve Tags. Pressure The Date code may be located on the,Setting underside of the test lever. ASME Pressure Steam Rating, The ASME pressure steam rating should be considered with.
caution because it represents the ability of the device to dis. charge steam pressure at the set pressure of the valve For. example let s consider a 150psi set relief valve with an ASME. pressure steam rating of 1 437 600 BTU per hour Before this. valve can deliver that rating there must be generated within. the tank over 150psi of steam pressure in order to actuate the. Thermal Expansion, valve This is certainly an unsafe condition for a non ASME Control Device. rated water heater tank The tank could rupture and explode. prior to reaching this ASME pressure rating An ASME rated T P Relief Valve. tank is constructed to higher standards than a non rated tank. It is important to understand which type of tank will be used in. an application For all non ASME rated tanks the CSA tem. perature steam rating should always be used,Pressure Relief Settings. T P Relief Valve, Questions regarding relief valve settings frequently come up Drain Tube. For some years 125psi was the standard setting Today. 150psi is considered the standard The history of the 125psi. setting stems from a water heater standard which formerly. stated that the working pressure of the water heater tank. would be designated at 42 of the test pressure As most. heaters were tested at 300psi the working pressure figured. out to 127psi Thus the 125psi valve became the standard. setting However the water heater standard was changed to. allow the working pressure to be 50 of the test pressure. resulting in the change to a pressure relief setting of 150psi. Under no circumstances should the relief valve setting of the. valve exceed the working pressure of the tank as this would. violate all heater warranties and codes Typical Heater Installation. Location in Water Heater,Installation,The installation of temperature and pressure. relief valves is critical They must be,installed so that the temperature sensing.
element is immersed in the hottest water,in the tank The hottest water is located in. the top six inches of the tank Most water,heaters are equipped with a special tap. ping for the T P valve at the proper loca,tion in the tank If however the valve. were to be installed a distance away from,the tank a thermal lag condition would be. created which simply means that the,valve thermostat cannot respond to the.
hottest water in the top of the heater For,example a 3 4 valve which is installed. four inches from the tank would actually,be sensing cooler water and by the time. the temperature of the water at the point,of the valve reached 210 F the tempera. ture at the top of the tank would be,244 F Another example If the valve was. installed ten inches away when it finally,sensed 210 F water the temperature at.
the top of the tank would be 272 F So the,basic rule is to install the valve so that the. temperature sensing element is immersed Typical T P Valve Installations. in the water in the top six inches of the,tank This may require the installation of an. extended temperature sensing element,Drain Lines, A drain line must be connected to the dis line must never be trapped Also the. charge outlet of a T P relief valve to avoid drain line should not contain any shut off. water damage and scalding injury A drain valves reducing couplings or restrictions. line the same size as the relief valve out One must never plug or crimp or reduce. let must be used in order to channel the the size of a drain line The T P valve. discharge of hot water to a safe place of rating can only be achieved with a full. disposal The drain line must pitch down sized discharge line The drain line. ward to allow for the complete drainage should terminate above a floor drain or. of both the valve and the line The drain where any discharge will be clearly visible. Watts Model 100DT drain lines are available for both T P mount and side mount T P valves. Boiling Points of Water, Water is practically an incompressible the energy which is the power behind an For example where water supply pres. solid and unless it is superheated it has explosion In an open vessel at atmos sure to the water heater is 90psi the boil. no latent heat energy within itself to pheric pressure water will boil at 212 F ing point is not reached until 331 2 F At. expand when released However water No matter how much heat is applied only 50psi water flashes into steam and. above 212 F is considered superheated there is no latent heat energy stored by boils at 297 F This energy if released by. water and does possess latent heat ener the water However water in a closed a water heater rupture equals more than. gy which when exposed to atmospheric system and under pressure has a much one pound of dynamite Thus it is essen. pressure flashes into steam and creates higher boiling point which increases with tial to keep water temperature below. pressure 212 F,Thermal Expansion, One of the more common question Another solution is to use an expansion.
regarding T P relief valves is why they tank With this method the expanded vol. drip In most cases dripping is caused by ume of water remains contained within. thermal expansion When water is heated the system which is important where. in a closed plumbing system it expands water conservation is a concern. causing an increase in pressure This Expansion tanks consist of an air cham. increase in system pressure over that reg ber separated by a flexible diaphragm. ulated by the pressure reducing valve is H32 When thermal expansion occurs the. called thermal expansion pressure The Governor 80 excess water created is absorbed by the. T P valve is a safety device and is tank When the tap is opened the water. not intended for continuous operation is then forced by the tank back into the. to relieve thermal expansion system Watts offers several potable. Continuous dripping can cause the water expansion tanks including the mod. build up of mineral deposits on the els DET PLT and DETA. valve and may render it useless,A simple way to detect whether or not. thermal expansion is the cause of a drip,ping relief valve is to open a fixture during. the expansion period Opening a fixture BRV 530C,opens the system and immediately the. pressure will drop back to normal A second Thermal expansion problems can be. method that is used to determine the solved by using a thermal expansion relief. maximum pressure of the system is to device on the system Devices include. install a pressure test gauge with a telltale auxiliary type relief valves which can be. on a hose bibb connection As the pres placed anywhere on the system and set DET. sure increases the gauge moves the tell approximately to 10psi below the water. tale By leaving the gauge on heater relief valve setting They allow the. the system for 24 hours the auxiliary relief valve to take the brunt of. telltale will remain at the thermal expansion relieving and prevent. highest pressure registered unnecessary relieving cycles by the T P. on the system relief valve, Watts model 276H300 or Watts offers the model 530C H32 and. IWTG water pressure BRV Watts also offers the Governor 80. test gauges can do just combination toilet ballcock and thermal DETA. that They connect to any expansion relief valve The Governor 80. standard hose bibb for easy discharges thermally expanded water into. thermal expansion detection 276H300 the toilet tank. T P Relief Valve Reinspection, Temperature and pressure relief valves valve inoperative Such conditions are not Contact a plumbing contractor.
should be reinspected at least once every detectable unless the valve and its com for a reinspection to assure. three years by a licensed plumbing con ponents are physically removed and continuing safety Failure. tractor or authorized inspection agency to inspected An unauthorized person must to reinspect as directed. ensure that the product has not been not attempt to conduct this inspection could result in unsafe. affected by corrosive water condition and temperature or pres. to ensure that the valve and discharge sure build up that can. line have not been altered or tampered result in serious injury. with illegally Certain naturally occurring or death and or. pressure increase When a relief valve is dripping it is typically due to thermal expansion When water is heated it expands This causes excess pressure in the system When the T amp P relief valve senses this excess pressure it opens relieving the thermal expansion and returning the pres sure back to normal conditions Second they respond to

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