at what psi is the safety valve set to open for sale

As well, the compressor in the system is capable of pumping air pressure to 500 psi (3450kPa), which poses danger to both the driver and others around the vehicle.

The driver of a commercial vehicle must know that the safety valve makes the sound of a machine gun when it releases excess air pressure from the system.

In an air brake system, the first tank that receives compressed air has a safety valve that releases air if the pressure gets too high. It is usually set to open at 150 psi. If the valve must open, there is a fault in the system that should be repaired by a mechanic.

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A question we commonly receive is why a valve appears to open, or actuate, earlier than expected. Often, we find that the valve is not, in fact, opening early. Rather, the perception that it is actuating early is due to a misunderstanding of set pressure.

The set pressure, also called the opening pressure, of a safety or relief valve is the inlet pressure at which the valve begins to open as required by code.

A valve should be set to open at the maximum allowable working pressure (MAWP) of the vessel the valve is intended to protect. There is some tolerance to actual set pressure, which means that a valve set at 100 psig may open slightly above or slightly below this level.

The first step is to determine if your valve really is opening early. Sometimes safety and safety relief valves appear to open before they reach the set pressure — there may be an audible or visible release of fluid between the seat and the disc. This is known as “simmer” or “warn,” and it is not the same as a full open.

Simmer, or warn, occurs when a valve opens slightly, discharging only a small percentage of its rated capacity. For example, direct spring-operated safety valves may simmer or warn at 90% of the nameplate set pressure. A valve that is simmering is not considered open.

The next step is to check your gauge to ensure that it is reporting the set pressure correctly. The gauge should be calibrated properly and located upstream of the valve, close to the valve inlet. Rapid increases in system pressure can make it appear that a valve is opening early because the gauge can’t accurately report the pressure.

If you still believe your valve is opening early, assess the operating factors that might be contributing to the situation. Valves are factory set using standard conditions, and factors like high temperature, vibration, and back pressure can cause them to open early. These conditions can be compensated for using cold set pressure, aka cold differential test pressure (CDTP). Learn more about CDTP from the National Board.

When you’re in the market for a pressure relief valve, a sales rep has probably asked you “what set pressure do you need?” This piece of information isrequiredto purchase a new pressure relief valve. You might have been able to retrieve this info from an old valve nameplate or look it up in your computer system, but what does the value mean?

Set pressure is the point at which a pressure relief valve is set to open under service conditions.It’s measured in pounds per square inch gauge (PSIG).

Set pressure sounds simple, right? Not always — there are rules and recommendations you should keep in mind when you’re determining the set pressure for pressure relief valves.

Identifying the process media, or service, of a valve is important to set pressure. If a valve has the correct set pressure but is used on the wrong application, there’s a chance the valve wouldn’t open when needed. This could cause the system or vessel to overpressure.

When the pressure in a system or vessel increases to a dangerous level, the pressure relief valve is there as the last line of defense. The valve opens when the inlet pressure exceeds the set pressure. When vessel pressure slightly exceeds the set pressure, fluid moves past the seating surface into the huddling chamber. The controlled pressure built up inside the huddling chamber will then overcome the spring force, causing the disc to lift and the valve to pop open.

After the valve opens, it will only close once the pressure has dropped a certain percentage below the set pressure. This percentage is referred to as blowdown, and will typically range anywhere from 4% to 10% depending on the applicable code.

Determining set pressure is just one thing you need to determine when you’re specifying a pressure relief or safety valve. If you need assistance finding the right-fit valve, contact us at (314) 665-1741.

A little product education can make you look super smart to customers, which usually means more orders for everything you sell. Here’s a few things to keep in mind about safety valves, so your customers will think you’re a genius.

A safety valve is required on anything that has pressure on it. It can be a boiler (high- or low-pressure), a compressor, heat exchanger, economizer, any pressure vessel, deaerator tank, sterilizer, after a reducing valve, etc.

There are four main types of safety valves: conventional, bellows, pilot-operated, and temperature and pressure. For this column, we will deal with conventional valves.

A safety valve is a simple but delicate device. It’s just two pieces of metal squeezed together by a spring. It is passive because it just sits there waiting for system pressure to rise. If everything else in the system works correctly, then the safety valve will never go off.

A safety valve is NOT 100% tight up to the set pressure. This is VERY important. A safety valve functions a little like a tea kettle. As the temperature rises in the kettle, it starts to hiss and spit when the water is almost at a boil. A safety valve functions the same way but with pressure not temperature. The set pressure must be at least 10% above the operating pressure or 5 psig, whichever is greater. So, if a system is operating at 25 psig, then the minimum set pressure of the safety valve would be 30 psig.

Most valve manufacturers prefer a 10 psig differential just so the customer has fewer problems. If a valve is positioned after a reducing valve, find out the max pressure that the equipment downstream can handle. If it can handle 40 psig, then set the valve at 40. If the customer is operating at 100 psig, then 110 would be the minimum. If the max pressure in this case is 150, then set it at 150. The equipment is still protected and they won’t have as many problems with the safety valve.

Here’s another reason the safety valve is set higher than the operating pressure: When it relieves, it needs room to shut off. This is called BLOWDOWN. In a steam and air valve there is at least one if not two adjusting rings to help control blowdown. They are adjusted to shut the valve off when the pressure subsides to 6% below the set pressure. There are variations to 6% but for our purposes it is good enough. So, if you operate a boiler at 100 psig and you set the safety valve at 105, it will probably leak. But if it didn’t, the blowdown would be set at 99, and the valve would never shut off because the operating pressure would be greater than the blowdown.

All safety valves that are on steam or air are required by code to have a test lever. It can be a plain open lever or a completely enclosed packed lever.

Safety valves are sized by flow rate not by pipe size. If a customer wants a 12″ safety valve, ask them the flow rate and the pressure setting. It will probably turn out that they need an 8×10 instead of a 12×16. Safety valves are not like gate valves. If you have a 12″ line, you put in a 12″ gate valve. If safety valves are sized too large, they will not function correctly. They will chatter and beat themselves to death.

Safety valves need to be selected for the worst possible scenario. If you are sizing a pressure reducing station that has 150 psig steam being reduced to 10 psig, you need a safety valve that is rated for 150 psig even though it is set at 15. You can’t put a 15 psig low-pressure boiler valve after the reducing valve because the body of the valve must to be able to handle the 150 psig of steam in case the reducing valve fails.

The seating surface in a safety valve is surprisingly small. In a 3×4 valve, the seating surface is 1/8″ wide and 5″ around. All it takes is one pop with a piece of debris going through and it can leak. Here’s an example: Folgers had a plant in downtown Kansas City that had a 6×8 DISCONTINUED Consolidated 1411Q set at 15 psig. The valve was probably 70 years old. We repaired it, but it leaked when plant maintenance put it back on. It was after a reducing valve, and I asked him if he played with the reducing valve and brought the pressure up to pop the safety valve. He said no, but I didn’t believe him. I told him the valve didn’t leak when it left our shop and to send it back.

When it came back, I laid it down on the outlet flange and looked up the inlet. There was a 12″ welding rod with the tip stuck between the seat and the disc. That rod was from the original construction and didn’t get blown out properly and just now it got set free. The maintenance guy didn’t believe me and came over and saw it for himself (this was before cell phones when you could take a picture).

If there is a problem with a safety valve, 99% of the time it is not the safety valve or the company that set it. There may be other reasons that the pressure is rising in the system before the safety valve. Some ethanol plants have a problem on starting up their boilers. The valves are set at 150 and they operate at 120 but at startup the pressure gets away from them and there is a spike, which creates enough pressure to cause a leak until things get under control.

If your customer is complaining that the valve is leaking, ask questions before a replacement is sent out. What is the operating pressure below the safety valve? If it is too close to the set pressure then they have to lower their operating pressure or raise the set pressure on the safety valve.

Is the valve installed in a vertical position? If it is on a 45-degree angle, horizontal, or upside down then it needs to be corrected. I have heard of two valves that were upside down in my 47 years. One was on a steam tractor and the other one was on a high-pressure compressor station in the New Mexico desert. He bought a 1/4″ valve set at 5,000 psig. On the outlet side, he left the end cap in the outlet and put a pin hole in it so he could hear if it was leaking or not. He hit the switch and when it got up to 3,500 psig the end cap came flying out like a missile past his nose. I told him to turn that sucker in the right direction and he shouldn’t have any problems. I never heard from him so I guess it worked.

If the set pressure is correct, and the valve is vertical, ask if the outlet piping is supported by something other than the safety valve. If they don’t have pipe hangers or a wall or something to keep the stress off the safety valve, it will leak.

There was a plant in Springfield, Mo. that couldn’t start up because a 2″ valve was leaking on a tank. It was set at 750 psig, and the factory replaced it 5 times. We are not going to replace any valves until certain questions are answered. I was called to solve the problem. The operating pressure was 450 so that wasn’t the problem. It was in a vertical position so we moved on to the piping. You could tell the guy was on his cell phone when I asked if there was any piping on the outlet. He said while looking at the installation that he had a 2″ line coming out into a 2×3 connection going up a story into a 3×4 connection and going up another story. I asked him if there was any support for this mess, and he hung up the phone. He didn’t say thank you, goodbye, or send me a Christmas present.

Pipe dope is another problem child. Make sure your contractors ease off on the pipe dope. That is enough for today, class. Thank you for your patience. And thank you for your business.

(a) Qualifications of individual who adjusts. Safety relief valves shall be set and adjusted by a competent person who is thoroughly familiar with the construction and operation of the valve being set.

(b) Opening pressures. At least one safety relief valve shall be set to open at a pressure not exceeding the MAWP. Safety relief valves shall be set to open at pressures not exceeding 6 psi above the MAWP.

(c) Setting procedures. When setting safety relief valves, two steam gauges shall be used, one of which must be so located that it will be in full view of the persons engaged in setting such valves; and if the pressure indicated by the gauges varies more than 3 psi they shall be removed from the boiler, tested, and corrected before the safety relief valves are set. Gauges shall in all cases be tested immediately before the safety relief valves are set or any change made in the setting. When setting safety relief valves, the water level shall not be higher than

(d) Labeling of lowest set pressure. The set pressure of the lowest safety relief valve shall be indicated on a tag or label attached to the steam gauge so that it may be clearly read while observing the steam gauge.

www.controlglobal.com is using a security service for protection against online attacks. An action has triggered the service and blocked your request.

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The importance of installing the correct temperature and pressure relief valve on a water heater or hot-water storage tank cannot be overemphasized. This applies to new vessels as well as relief valve replacements. The importance of installing a valve with the correct pressure rating is common knowledge to many, but it also is crucial to install a valve with the appropriate relieving capacity rating. Many times the capacity factor is overlooked.

The code of construction of the vessel itself can play a key role in choosing the correct valve capacity. Unfortunately, the code of construction criteria is unknown to many and overlooked by others.

As the name indicates, T&P relief valves are designed to protect water heaters and hot-water storage vessels against excess temperature and excess pressure. Most valves are rated at 150 psi and 210° F, but their capacity ratings vary greatly. Sometimes, an additional T&P relief valve with a lower temperature and pressure rating (typically 180° and 100 psi) is installed in a plastic hot-water distribution system to protect the piping system itself. A T&P relief valve is, in essence, a dual device because it meets the code requirements of an individual temperature relief valve and an individual pressure relief valve.

The temperature function of the valve is controlled by an internal thermostatic element. At 210°, the internal expansion within the probe causes a piston to push against the valve’s disk. The spring is overpowered and compressed, and the water escapes between the disc and seat. The extremely hot water within the tank is forced out under pressure as cold water replenishes the discharge. The cold water rushing into the vessel lowers the water temperature, and when the temperature drops back below 210°, the valve is reseated.

The pressure function of the valve also is controlled by the spring, disc and seat. When the pressure exceeds the valve’s pressure rating, the water pressure overcomes the spring. The spring is compressed (just like a typical pressure-only relief valve) and the water escapes between the disc and seat.

It is important to note that when the valve is weeping or dripping, the cause is usually excessive pressure. Many times this is caused by thermal expansion. A T&P relief valve is not designed to nor should it be used to continuously control thermal expansion within a closed system. Thermal expansion of hot water within a closed system should be controlled with the installation of an approved expansion tank or by other means permitted by local code.

Dripping may continue because of debris within the valve, such as a build-up of calcium in the seat, and over time, large mineral deposits can make the valve ineffective. When a valve is discharging a large quantity of water, the cause is almost always excessive temperature.

The only way to determine the maximum allowable working pressure of a vessel is to read the nameplate that is attached to it. The pressure on the valve’s tag must be compared to the pressure on the vessel’s nameplate. The pressure rating of the relief valve must be equal to or less than the MAWP of the vessel. Most water heaters have an MAWP of 150 psi; however, some are rated higher, typically 160 psi. Some storage vessels have a lower pressure rating; they are commonly rated 125 psi.

Another factor in determining the pressure rating of the T&P relief valve is the code itself. Model codes require the T&P relief valve be set no higher than 150 psi. Therefore, a water heater with a MAWP of 160 psi still requires a T&P relief valve set at 150 psi, even though the vessel is designed and built to withstand a higher pressure.

The relieving capacity of the valve must be equal to or greater than the Btu/hr. of the vessel. The thermal capacity of the water heater can be found on its nameplate along with the MAWP. The confusion in choosing the correct T&P relief valve resides on the relief valve’s nametag itself. T&P relief valves display two relieving capacity ratings. One is the American Society of Mechanical Engineers/National Board of Boiler and Pressure Vessel Inspectors rating, and the other is the Canadian Standards Association/American National Standards Institute Z21.22 rating.

The relieving capacity of the valve’s ASME/NB rating is established by Section IV, Part HG of the “ASME Boiler and Pressure Vessel Code.” The code reads, “Capacity certification tests of safety relief valves for water heating and hot-water supply boilers shall be conducted at 110% of the pressure for which the valve is set to operate.” So the capacity of a T&P relief valve set at 150 psi is based on its vessel pressurized to 165 psi.

The ASME/NB relieving capacity rating is more lenient than the CSA rating. The CSA rating is based on 15 psi of steam pressure, so the CSA rating will always be lower and, therefore, more stringent than the ASME/NB rating. ASME HLW water heaters are built to a more stringent code of construction than ANSI Z21 water heaters. The use of a valve’s ASME/NB capacity rating to protect an ANSI-built vessel could present a potentially dangerous condition.

Chapter 5, Section 504.4 of the 2012 International Plumbing Code specifically requires relief valves to conform to the Z21.22 standard; the code is very concise. Some of the other model codes are not as clear as the IPC. Section 504 of the Uniform Plumbing Code only references an approved, listed device installed in accordance with the listing and the manufacturer’s installation instructions; however, the Z21.22 standard is included in Table 1401.1.

While the 2012 National Standard Plumbing Code makes no distinction between the use of the ASME/NB and CSA capacity ratings, the 2015 NSPC will limit the use of the ASME/NB relieving capacity ratings to ASME vessels only.

If permitted by the local adopted code, AMSE/NB relieving capacities should only be considered for ASME vessels. The more restrictive CSA relieving capacities are always the safer choice.

As soon as mankind was able to boil water to create steam, the necessity of the safety device became evident. As long as 2000 years ago, the Chinese were using cauldrons with hinged lids to allow (relatively) safer production of steam. At the beginning of the 14th century, chemists used conical plugs and later, compressed springs to act as safety devices on pressurised vessels.

Early in the 19th century, boiler explosions on ships and locomotives frequently resulted from faulty safety devices, which led to the development of the first safety relief valves.

In 1848, Charles Retchie invented the accumulation chamber, which increases the compression surface within the safety valve allowing it to open rapidly within a narrow overpressure margin.

Today, most steam users are compelled by local health and safety regulations to ensure that their plant and processes incorporate safety devices and precautions, which ensure that dangerous conditions are prevented.

The principle type of device used to prevent overpressure in plant is the safety or safety relief valve. The safety valve operates by releasing a volume of fluid from within the plant when a predetermined maximum pressure is reached, thereby reducing the excess pressure in a safe manner. As the safety valve may be the only remaining device to prevent catastrophic failure under overpressure conditions, it is important that any such device is capable of operating at all times and under all possible conditions.

Safety valves should be installed wherever the maximum allowable working pressure (MAWP) of a system or pressure-containing vessel is likely to be exceeded. In steam systems, safety valves are typically used for boiler overpressure protection and other applications such as downstream of pressure reducing controls. Although their primary role is for safety, safety valves are also used in process operations to prevent product damage due to excess pressure. Pressure excess can be generated in a number of different situations, including:

The terms ‘safety valve’ and ‘safety relief valve’ are generic terms to describe many varieties of pressure relief devices that are designed to prevent excessive internal fluid pressure build-up. A wide range of different valves is available for many different applications and performance criteria.

In most national standards, specific definitions are given for the terms associated with safety and safety relief valves. There are several notable differences between the terminology used in the USA and Europe. One of the most important differences is that a valve referred to as a ‘safety valve’ in Europe is referred to as a ‘safety relief valve’ or ‘pressure relief valve’ in the USA. In addition, the term ‘safety valve’ in the USA generally refers specifically to the full-lift type of safety valve used in Europe.

Pressure relief valve- A spring-loaded pressure relief valve which is designed to open to relieve excess pressure and to reclose and prevent the further flow of fluid after normal conditions have been restored. It is characterised by a rapid-opening ‘pop’ action or by opening in a manner generally proportional to the increase in pressure over the opening pressure. It may be used for either compressible or incompressible fluids, depending on design, adjustment, or application.

Safety valves are primarily used with compressible gases and in particular for steam and air services. However, they can also be used for process type applications where they may be needed to protect the plant or to prevent spoilage of the product being processed.

Relief valve - A pressure relief device actuated by inlet static pressure having a gradual lift generally proportional to the increase in pressure over opening pressure.

Relief valves are commonly used in liquid systems, especially for lower capacities and thermal expansion duty. They can also be used on pumped systems as pressure overspill devices.

Safety relief valve - A pressure relief valve characterised by rapid opening or pop action, or by opening in proportion to the increase in pressure over the opening pressure, depending on the application, and which may be used either for liquid or compressible fluid.

In general, the safety relief valve will perform as a safety valve when used in a compressible gas system, but it will open in proportion to the overpressure when used in liquid systems, as would a relief valve.

Safety valve- A valve which automatically, without the assistance of any energy other than that of the fluid concerned, discharges a quantity of the fluid so as to prevent a predetermined safe pressure being exceeded, and which is designed to re-close and prevent further flow of fluid after normal pressure conditions of service have been restored.

A Pressure Relief Valve (also known as a Safety Valve, Overpressure Relief Valve, or simply a Relief Valve) limits the amount of pressure in a compressed gas system. Without such a valve in place, pressure could build up beyond what the system is designed for and cause equipment failure. The Pressure Relief Valve opens at a designed “set pressure” to protect the system against failure from being overpressurized. This valve has a designed set pressure of 3625 psi (250 bar).

We explain where a pressure relief valve is usually installed on well water pressure tanks, how the valve works, and why pressure relief valves are an important safety feature on well tanks.

The water tank pressure relief valve shown in our photo (above) is marked indicating that it will open at water pressure equal to or greater than 75 psi. That pressure is pretty standard and you"ll see the 75 psi figure on valves used on water tanks and on some tankless water heaters too.

High pressure in a building water supply system can result if the water pressure switch that controls the well pump is damaged, or if the pump stays on too long.

Most submersible well water pumps can develop pressure exceeding the rated working limits of the water pressure tank or building water distribution system piping, fittings, and fixtures.

Excess water pressure can damage water system component as well as the pressure tank if not corrected immediately, and can also cause leaks within the piping system or at faucets and fixtures. Therefore on all building water supply systems using a private well and pump, a pressure-relief valve is recommended.

Water pressure relief valves are spring-controlled and open only in response to system pressure. That is, water temperature is not a controlling factor for these valves. For water service, these important safety devices are generally adjusted to relieve pressure higher than 75 psi. [1]

Watch out: water pressure tank fatality: we [Ed] are aware of a fatality that occurred in the Hudson Valley of New York State when a plumber, working alone on a water pressure tank and pump system was killed as the water pressure tank burst. - personal communication, Steve Vermilye to Editor ca 2001.

There was no pressure relief valve on the water system; a submersible well pump was installed; the well pump pressure control switch stuck in the "on" position.

We suspect that because the submersible pump was located inside the well and thus there was little or no operating noise when the pump was on, the plumber had no idea that the pump was running.

When the pressure inside the water tank exceeded the tank"s design specifications the tank burst open. The plumber, leaning over the water tank to perform some task, was cut and killed by the "shrapnel" formed when the water tank burst. - ED.

Chester New York Police Dept. Water Treatment Plant Explosion - King Tract Development [PDF] Town of Chester, NY Police Department, - retrieved 2021/04/19 original source: https://local.nixle.com/alert/4894709/

At 6:30PM on Tuesday, the Town of Chester Police responded to a report of an explosion in the King Tract development off of Laroe Road. Residents in the area were reporting that they had no water. It was determined that the water treatment plant for the development had exploded. Chester Fire Department responded to the scene and were assisted by Orange County Fire Investigators. No evidence of criminal activity was detected.

The water holding tank is pressurized by a compressor to send water to the residences. Preliminary investigation reveals that the tank failed and the internal pressure blew the end of the tank off and through the attached treatment building, completely demolishing the building. The water system that serves the area is privately owned by 473 West End Realty Corp. The water system owner has indicated that drinking water will be available to the residents from a water tanker later today.

Fox News "Two Killed From 300,000 Gallon Water Tank Explosion" Fox News, Tel: (888) 369-4762, April 07, 2011 - retrieved 2021/04/19 original source: https://www.foxnews.com/us/two-killed-from-300000-gallon-water-tank-explosion

The victims were in the midst of repairing a pump that filled the tank inside an adjacent concrete block building. The force of the water from the explosion caused the building to collapse, MyFoxTampaBay.com reported.

HeatingHelp.com, "Fatal Airing up of Water Tank", reported by Jughne, September 2016 - possibly anecdotal, no corroboration found, retrieved 2021/04/19 original source: https://forum.heatinghelp.com/discussion/158963/fatal-airing-up-of-water-tank

Karpen, R.J., "Investigation of a Water Pressure Tank Explosion", Minnesota Department of Health, Mankato MN, October 1940, retrieved 2021/04/19 original source: https://awwa.onlinelibrary.wiley.com/doi/abs/10.1002/j.1551-8833.1940.tb19589.x

On December 14, 1938, the water pressure tank of the municipal water supply of Bricelyn Minnesota exploded, wrecking the pump house and tank. The explosion occurred at 1 AM just as the pressure gauge indicated pressure nearest 60 pounds and the pump was about to shut off. The possibility that the zinc lining in the pressure tank was a contributing factor to the explosion was indicated in an investigation report conducted by the Minnesota Department of Health.

The Bricelyn water supply, prior to this explosion, was obtained from a drilled well from which the water was lifted by means of air and discharged into a small receiving tank. A centrifugal pump was used to force water from the receiving take into the pressure tank and distribution system. This pump had a rated capacity of 250 gpm, and was designed to operate up to a maximum head of 60 psi.

It was the practice of the operator to maintain the water level in the tank at about 4 in. above the center. This he accomplished by pumping at approximately two-hour intervals from 7:00 AM to 3:00 PM, at 6:00 PM, 8:30 PM, and at midnight. The daily consumption of water was about 18,000 gal. The pressure tank, 8 ft. in diameter and 36 ft. long, had been in service for 36 years. It was provided with a pressure relief valve which when tested opened at a pressure of 66 lb. psi.

Eight or ten onths prior to the explosion, a leak developed in an end seam at the bottom of the tank. After the tank was drained and inspected it was found that the portion of the tank which had been in contact with the water was petted and corroded. It was then reconditioned by welding the defective same and it"s interior surface was coded by spraying it with molten zinc.

TOMBALL, Texas A worker was killed Tuesday after a water storage tank exploded near Tomball. It happened at the Salem Lutheran Church, at Lutheran Church Road and FM 2920.A spokesperson for the church said the injured man was working on the 20-foot-tall tank when the blast happened. The force of the explosion caused the worker to fall and ripped the lid off the tank. - original source https://www.khou.com/amp/article/news/worker-killed-in-church-water-tank-explosion/285-341096970

Yannaccone, John R., P.E. "PRESSURIZED WATER TANK EXPLOSION" DJS Associates, John R. Yannaccone, P.E., Senior Mechanical Engineer with DJS Associates, Inc., Email: experts@forensicDJS.com Tel: 215-659-2010.- retrieved 2021/04/19 original source: https://www.forensicdjs.com/blog/pressurized-water-tank-explosion/

A worker was operating a system used to supply water from a tank mounted on a utility vehicle. Instead of using a pump, this system used a 120-gallon water tank, which was pressurized from a compressed air cylinder. The air pressure pushes water out of the tank, referred to as an “air over water” system. While operating the system, a worker near the vehicle was blown 20 feet from where he was standing. He sustained severe blunt force trauma and died as a result of his injuries. Photographs from the incident showed that the end of the water tank dislodged from the main portion of the tank.

Expert Analysis: An inspection of the system revealed that the tank was in good condition, with no signs of corrosion or other damage. The 120-gallon water tank had a label indicating the maximum working pressure for the tank was 75 psi and must be equipped with an adequate size pressure relief valve; however, there was no pressure relief valve in this system.

... it was determined that the pressure regulator failed during operations, allowing air to continuously flow into the tank. The lack of a pressure relief valve allowed the tank pressure to increase until the tank failed.

Watts 53 pressure relief valves in 1/2-in NPT and 3/4-in NPT. Model 53L includes a test or relief lever. Quoting from Watts® product literature for this product:

Series LF530C Lead Free* Calibrated Pressure Relief Valves are used in commercial, residential and industrial applications to protect against excessive pressure in systems containing water, oil, or air.

It consists of a Lead Free* brass body construction with NPT threaded male inlet and NPT threaded female (drain) outlet connections, stainless steel spring, brass bonnet, Buna-N disc, and Buna-N O-ring.

Series LF530C has a calibrated adjustment feature for setting the valve to the required relief pressure, and is ideal for by-pass thermal expansion pressure relief (not ASME approved).

Maximum Pressure: 300psi (20.67 bar). Adjustable Pressure Ranges: Sizes 1/2, 3/4 in. - 50 to 175psi (3.45 to 12.06 bar), Size 3/4 in. - 100 to 300psi (6.89 to 20.67 bar). - Watts®

Watts 30L Pressure Relief Valves for Well Systems, with test lever. These valves, intended for protection against excessive pressure in well water systems, are designed for pressure relief only [compared with pressure and temperature relief valves that should be used on water heating equipment -

Series 30L Pressure Relief Valves for Wells are used to protect against excessive pressures in well systems. It is not diaphragm actuated and is used for pressure-relief service only.Series 30L consists of a bronze body construction with NPT threaded male inlet and NPT threaded female (drain) outlet connections, stainless steel spring, and test lever. Standard Pressure Setting: 75psi (5.17 bar), Optional Settings: 100, 125, and 150psi (6.9, 8.6, and 10.3 bar). - Watts®

These valves are installed as an auxiliary bleeder pressure relief valve to provide relief of increased water pressure due to thermal expansion, and they are typically installed on a hot water supply pipe downstream from the water heater and over a laundry sink or drain. Watts points out in their product literature that these valves are also installed on cold water piping.

Standard water tank pressure relief valves are sold at plumbing suppliers and are pre-set with a "safe" pressure for most home water tanks, provided that the water tank, piping, and controls are properly installed and adjusted.

A professional plumber would select and install a water tank pressure relief valve that opens to spill water and relieve pressure at a point well below the rated burst pressure of the tank.

The burst-pressure of a water tank, provided it"s undamaged and properly installed, should be well above the opening pressure on the tank relief valve. But to choose a specific valve matched to your water tank, you should consult the manual for your water tank and pump and their manufacturer to be sure you"ve got the right part.

Dan I"m not entirely clear on what is your situation, but if you have a 1" diameter pressure relief valve it is unsafe to downsize its discharge to 1/2" -

I have a well water 1 inch relief valve with a 0.5 inch output. It is leaking and would like to buy another, but cannot find one. Also my water tank holds 50 gal and the tank pressure should be 40psi.

Allen we dont" want the valve to spit water; I suspect that the water level is too high in the tank OR the float is sticking and not closing the valve OR there is dirt on the valve seat.

My bladder type tank has an air release valve similar to a schrader valve. Lately in addition to expelling the air when the tank is filling, I"m getting a "spit" of water or condensation with it. Is this something to be concerned with? I"m in the humid Houston area, so I guess it could be condensation, but I also don"t want that dripping down my tank and eventually corroding it.

I had a home inspection and two things came up that the seller is not willing to fix. Can you tell me anything about the items and costs associated with fixing the issues? The inspection reads:

I had a home inspection and two things came up that the seller is not willing to fix. Can you tell me anything about the items and costs associated with fixing the issues? The inspection reads:

Jon, Definitely, I"ve heard various valves in plumbing systems make a horrible screeching sound if the pressure and flow rate happen to be just right (or wrong).

But you should not be having a discharge from a pressure relief valve on a water supply system - the valve should only open if the system is at abnormally high (and unsafe) water pressure. So if there is no water discharge from the valve, I"d look elsewhere.

Can a bad pressure relief valve give off a high pitched squeal? I have such a noise coming from the area of my well equip, but not on a regular or constant basis.

WATER TANK PRESSURE RELIEF VALVE at InspectApedia.com - online encyclopedia of building & environmental inspection, testing, diagnosis, repair, & problem prevention advice.

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Watts Corporation, Series 53 Pressure Relief Valves, for commercial and residential applications, publication ES-53 1010, Watts Corporation, 815 Chestnut St., No. Andover, MA 01845-6098; www.watts.com and Watts Corporation in Canada: 5435 North Service Rd., Burlington, ONT. L7L 5H7; www.wattscanada.ca.

Access Water Energy, PO Box 2061, Moorabbin, VIC 3189, Australia, Tel: 1300 797 758, email: sales@accesswater.com.au Website: http://www.accesswater.com.au/

Australian supplier of: Greywater systems, Solar power to grid packages, Edwards solar systems, Vulcan compact solar systems, water & solar system pumps & controls, and a wide rage of above ground & under ground water storage tanks: concrete, steel, plastic, modular, and bladder storage tanks.

Grove Electric, Typical Shallow Well One Line Jet Pump Installation [PDF], Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf

Grove Electric, Typical Deep Well Two Line Jet Pump Installation [PDF], Grove Electric, G&G Electric & Plumbing, 1900 NE 78th St., Suite 101, Vancouver WA 98665 www.grovelectric.com - web search -7/15/2010 original source: http://www.groverelectric.com/howto/38_Typical%20Jet%20Pump%20Installation.pdf

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Boiler explosions have been responsible for widespread damage to companies throughout the years, and that’s why today’s boilers are equipped with safety valves and/or relief valves. Boiler safety valves are designed to prevent excess pressure, which is usually responsible for those devastating explosions. That said, to ensure that boiler safety valves are working properly and providing adequate protection, they must meet regulatory specifications and require ongoing maintenance and periodic testing. Without these precautions, malfunctioning safety valves may fail, resulting in potentially disastrous consequences.

Boiler safety valves are activated by upstream pressure. If the pressure exceeds a defined threshold, the valve activates and automatically releases pressure. Typically used for gas or vapor service, boiler safety valves pop fully open once a pressure threshold is reached and remain open until the boiler pressure reaches a pre-defined, safe lower pressure.

Boiler relief valves serve the same purpose – automatically lowering boiler pressure – but they function a bit differently than safety valves. A relief valve doesn’t open fully when pressure exceeds a defined threshold; instead, it opens gradually when the pressure threshold is exceeded and closes gradually until the lower, safe threshold is reached. Boiler relief valves are typically used for liquid service.

There are also devices known as “safety relief valves” which have the characteristics of both types discussed above. Safety relief valves can be used for either liquid or gas or vapor service.

Nameplates must be fastened securely and permanently to the safety valve and remain readable throughout the lifespan of the valve, so durability is key.

The National Board of Boiler and Pressure Vessel Inspectors offers guidance and recommendations on boiler and pressure vessel safety rules and regulations. However, most individual states set forth their own rules and regulations, and while they may be similar across states, it’s important to ensure that your boiler safety valves meet all state and local regulatory requirements.

The National Board published NB-131, Recommended Boiler and Pressure Vessel Safety Legislation, and NB-132, Recommended Administrative Boiler and Pressure Vessel Safety Rules and Regulationsin order to provide guidance and encourage the development of crucial safety laws in jurisdictions that currently have no laws in place for the “proper construction, installation, inspection, operation, maintenance, alterations, and repairs” necessary to protect workers and the public from dangerous boiler and pressure vessel explosions that may occur without these safeguards in place.

The documents are meant to be used as a guide for developing local laws and regulations and also may be used to update a jurisdiction’s existing requirements. As such, they’re intended to be modifiable to meet any jurisdiction’s local conditions.

The American Society of Mechanical Engineers (ASME) governs the code that establishes guidelines and requirements for safety valves. Note that it’s up to plant personnel to familiarize themselves with the requirements and understand which parts of the code apply to specific parts of the plant’s steam systems.

High steam capacity requirements, physical or economic constraints may make the use of a single safety valve impossible. In these cases, using multiple safety valves on the same system is considered an acceptable practice, provided that proper sizing and installation requirements are met – including an appropriately sized vent pipe that accounts for the total steam venting capacity of all valves when open at the same time.

The lowest rating (MAWP or maximum allowable working pressure) should always be used among all safety devices within a system, including boilers, pressure vessels, and equipment piping systems, to determine the safety valve set pressure.

General guidance on proper installation may seem like common sense to experienced installers and inspectors. A few of the most important guidelines and best practices include:

Avoid isolating safety valves from the system, such as by installing intervening shut-off valves located between the steam component or system and the inlet.

Contact the valve supplier immediately for any safety valve with a broken wire seal, as this indicates that the valve is unsafe for use. Safety valves are sealed and certified in order to prevent tampering that can prevent proper function.

Avoid attaching vent discharge piping directly to a safety valve, which may place unnecessary weight and additional stress on the valve, altering the set pressure.