kunkle safety valve free sample

Kunkle Valves is a leading manufacturer of quality safety and relief valve products for industrial and commercial applications. Kunkle products are available for ASME Section I, Section IV and Section VIII services with relief capacities certified by the National Board.

The plate mounted on the side of your Kunkle valves is small yet mighty — it’s full of concise information that can help inform your next purchase decision or develop plans for new processes. But like most data snapshots (think the jargon on your “About this Mac” or “About my PC” window), it’s not always clear what everything means.

The ASME stamp is typically in the top corner of your nameplate. This stamp means that the valve has been assembled and set to meet the standards of a specific ASME code section. In this example, the valve has a “V” stamp. That indicates the valve is certified for an ASME Section I application.

Some Kunkle valves are non-coded by design, often for liquid applications that don’t require an ASME certified valve (e.g. Models 19, 20) or for vacuum service (Model 215V).

On the top of your nameplate, you’ll notice an NB stamp, which is associated with theNational Board of Boiler and Pressure Vessel Inspectors. If your pressure relief valve bears the NB stamp, it means it has a relief capacity certified by the NBBPVI in accordance withNB-501. Most Kunkle valves have certified capacities.

Often located near the top of the plate, and in this example, directly to the right of the NB stamp, you’ll notice the manufacturer and assembler name. This particular valve has been set by the factory, which makes Emerson (“EMRN”) the assembler.

Note: The value directly below the product and manufacturer names beginning with “CRN” is the Canadian Registration Number and will not be present on all Kunkle Valves.

Your valve’s nameplate also contains the model number, which is extremely useful for when you need to reorder the same valve. In this case, the model number is6010HGM01. The first two to four digits are generally the series or model the valve belongs to — here,6010.

In most cases, the letter indicating service will be somewhere further along in the model number. However, this letter could be in various positions depending on the valve series, making it tricky to recognize. For the most accurate information, check the product catalog of your valve series.

The size on the nameplate will tell you the nominal pipe diameter of the inlet (the connection on the bottom of the valve), which is 1 ½” in the case of this valve.

To the right of the size on this nameplate is the set pressure, which is 150 psig (pounds per square inch gauge). So in this pressure relief valve’s case, it will open as soon as it detects 150 psig at the inlet of the valve.

On Kunkle nameplates, the rated capacity is abbreviated as CAP. This value needs to meet or exceed your required capacity. In other words, the valve you purchase must be able to relieve pressure at least as quickly as your system’s worst-case overpressure scenario can generate it.

Knowing what all of these values and stamps mean is incredibly helpful when you’re reordering the same part. In most cases, you can just provide your distributor with the model number and be on your way! But if you need assistance specifying a valve for another application, or even to improve your current process,check out this articleor give our experts a call at (314) 665-1741.

Getting the right pressure relief valve is essential to protect your process, your personnel, and your facility. Here we identify the piece of information you need to specify a safety valve, safety relief valve, or relief valve — plus some “bonus” details that will make the selection process a breeze.

Each valve comes with a nameplate from which you can pull much of the information you need, like the manufacturer name, model number, set pressure, size, code stamp, service, and capacity. If you have this information — especially the model number — you may be all set.

If you’re building out a new process or don’t have access to an existing valve’s data, you’ll need to determine these critical pieces of information to specify your correct pressure relief valve.

Your valve needs to correspond to the size of your inlet and outlet piping. According toThe National Board of Boiler and Pressure Valve Inspectors, your inlet and discharge pipingcan’t be smallerin diameter than the valve inlet and outlet openings. Incorrect sizing can interfere with normal device operation. The inlet size and connection of your valve will range depending on your application.

When you define your service, you may have to be more specific than “steam,” “air,” or “gas.” There are thousands of services used in industrial processes, encompassing everything from molasses to water to hydrogen to ethylene glycol, and each one has a unique set of valve requirements.

Measured in pounds per square inch gauge (PSIG), set pressure is the point at which the pressure relief valve opens. The set pressure of your valve should never exceed the MAWP (maximum allowable working pressure) of the equipment the valve will be placed on. Further, it’s recommended that your maximum operating pressure be 10% below your valve’s set pressure.

Defining the set pressure for liquid service can be tricky, as liquid relief valves are susceptible tochatter— the rapid opening and closing of the valve.

Repeated opening and closing can result in things like misalignment, valves seat damage, and even mechanical failure, making chatter a significant safety risk. To avoid these issues, place your liquid set pressure at the pressure when the first heavy flow — or first steady vertical flow — occurs.

Pressure relief valves will operate differently based on the environment. So if you’re going to install your valve somewhere with extremely high or low temperatures, define that too. Here are a couple examples of how the environment can affect valve operation:

The information above is required to know prior to purchasing a valve. Having these further snippets of information is optional, but will help guarantee you get the best valve for your application.

Relief valves have to be able to relieve pressure at a certain capacity. If a valve can’t meet or exceed your required capacity, you can end up with major issues.

Identifying the pressure at which the valve will be subjected to regularly — or the operating pressure — will ensure you select a valve that can withstand your standard operating conditions.

Operating temperature can affect the volume and viscosity of a gas or liquid flowing through the pipes. Further, the operating and relieving temperatures can help determine the best material for your application. For example, if you need a pressure relief valve for a steam process and you know the steam is hotter than usual when the pressure relief valve is triggered, you’ll need to select a valve that can handle those higher temperatures. In this case, you might choose a steel valve instead of bronze or iron.

Each Kunkle valve comes with its own leakage acceptance criteria, so knowing this piece of information will help make proper seating selection. For example, if you can’t allow any leakage at all, you must select a valve with soft seating.

Valves are compatible with different kinds of accessories — too many to mention here — designed to make your operations run safely and efficiently. Keep in mind that certain codes may dictate which options you can choose.

Coming armed with more details about what you need will expedite the valve selection and purchasing process. However, you don’t need to wait to gather all the details provided here before starting. If you provide these three basic pieces of information, we can help guide you in the right direction:

Given these pieces of information, we can give you a starting point for selecting the perfect valve for your application.Contact us today to get started!

Kunkle Valve is a premier manufacturer of pressure relief valves. In fact, Erastus B. Kunkle invented the safety valve, which he patented in 1875, to prevent overpressure in locomotive engines. For almost 150 years, Kunkle Valve has been known for their high-quality products — many pieces of equipment that require valves, like boilers and air compressors, are shipped from the factory with a Kunkle Valve already installed.

The basic design of Kunkle valves is similar to that of Consolidated valves, with a disc on top of a seating surface and a spring set to relieve at a certain pressure. The major differences between the two types of valves is their size and where they are used: whereas Consolidated makes large, heavy-duty valves for industrial applications like pipelines and refineries, Kunkle makes smaller, less expensive pressure relief valves for lower-pressure commercial applications, like hospital boilers and building sprinkler systems.

Kunkle makes many different types of valves that can be used for many purposes. The entire line includes 30 or so models that are available in sizes ranging from ¼” to 6” x 8”. Within that line, they cover a lot of niche areas. For example, they have valves made of bronze, cast iron, steel, and even 316 stainless steel. Due to the material variety, the valves can be used in many applications, from sanitary applications (hospitals, food machinery) to boilers on ships, to corrosive applications like acids.

Model 6010, which is a side outlet, full nozzle valve that has bronze/brass trim (also available with a Teflon® disc insert [Model 6021] and with stainless steel trim [Model 6030]). The 6010 comes in sizes ½” to 2” and is used primarily on smaller boilers and heating systems.

Model 6252, which is a cast iron valve with an enclosed spring and stainless steel trim. The 6252 ranges from 1 ½” to 6” and is used for larger steam boilers and also sometimes for air service.

Universities are a good example of where Kunkle steam valves might be used. Many universities have a steam plant and need to transfer the generated steam to 30 or 40 buildings through underground piping. Along that piping, they may have different pressure requirements, such as 30 pounds of steam pressure to heat a dorm, but only 2 or 3 pounds to heat steam tables in the cafeteria. In this case, each pressure reducing station would be followed by a Kunkle relief valve.

Many Kunkle valves are designed for air service, such as on air compressors in auto shops and small factories where either low- or high-pressure air is required. For example, at a tire shop that uses mechanical or pneumatic tools, a Kunkle air valve would sit atop the air compressor.

Kunkle also makes valves for liquid service, which are installed on water lines after pumps. For example, in an apartment building that has a sprinkler system, relief valves are there to keep the pressure from getting too high.

View our full line of Kunkle Valve products. If you have any questions about Kunkle Valves or need help sizing and selecting the right valve for your application, give us a call or shoot us an email — we’re here to help.

Kunkle Relief Valve OverviewWhen it comes to industrial and commercial safety and relief valve products, Kunkle’s valve’s catalog is second to none in steam, air, gas, and liquid applications.

Kunkle relief valves range in size from ¼” NPT to 6” flange and are suitable in cryogenic and high temperatures up to 800°F environments at vacuum to 7,500 psig pressure. Kunkle Valve’s code certifications meet several global and national board standards, including ASME Section I, Section IV, and Section VIII, PED, CRN, TU and Chinese, as well as non-code requirements.

Relief Valves for Steam ServiceSteam supplies heat for industrial and chemical processes and also is used to heat buildings, supply mechanical energy, and drive mechanical equipment. Steam moves from the boiler to the end point, then heats by direct heating or indirect heating through a heat exchanger. Kunkle steam relief valves are critical to protecting equipment such as boilers, steam lines, and pressure valves, from being over-pressurized.

Relief Valves for Air ServiceKunkle designs valves for air service, for example for air compressors in mechanical shops and small factories where either low-pressure or high-pressure air is required. NASVI stocks Kunkle relief valves for air service in iron, steel and bronze for a variety of uses.

Relief Valves for Liquid ServiceKunkle also makes valves for liquid service, which provide bypass relief in a variety of applications and liquid types.

More About KunkleKunkle Valve is a renowned pressure relief valve manufacturer. Erastus B. Kunkle invented the safety valve to prevent overpressure in locomotive engines. Kunkle patented it in 1875. Since that time, Kunkle has earned its reputation for high-quality valves, and other equipment manufacturers ship their products with Kunkle’s valves pre-installed.

NASVI has stocked Kunkle safety relief valves since we opened in 1975, so we are confident when we call ourselves Kunkle safety valve experts. Every day we fulfill orders for our customers looking for Kunkle relief valves for steam, air, gas, and liquid applications.

Safety is of the utmost importance when dealing with pressure relief valves. The valve is designed to limit system pressure, and it is critical that they remain in working order to prevent an explosion. Explosions have caused far too much damage in companies over the years, and though pressurized tanks and vessels are equipped with pressure relief vales to enhance safety, they can fail and result in disaster.

That’s also why knowing the correct way to test the valves is important. Ongoing maintenance and periodic testing of pressurized tanks and vessels and their pressure relief valves keeps them in working order and keep employees and their work environments safe. Pressure relief valves must be in good condition in order to automatically lower tank and vessel pressure; working valves open slowly when the pressure gets high enough to exceed the pressure threshold and then closes slowly until the unit reaches the low, safe threshold. To ensure the pressure relief valve is in good working condition, employees must follow best practices for testing them including:

If you consider testing pressure relief valves a maintenance task, you’ll be more likely to carry out regular testing and ensure the safety of your organization and the longevity of your

It’s important to note, however, that the American Society of Mechanical Engineers (ASME) and National Board Inspection Code (NBIC), as well as state and local jurisdictions, may set requirements for testing frequency. Companies are responsible for checking with these organizations to become familiar with the testing requirements. Consider the following NBIC recommendations on the frequency for testing relief valves:

High-temperature hot water boilers (greater than 160 psi and/or 250 degrees Fahrenheit) – pressure test annually to verify nameplate set pressure. For safety reasons, removal and testing on a test bench is recommended

When testing the pressure relief valve, raise and lower the test lever several times. The lever will come away from the brass stem and allow hot water to come out of the end of the drainpipe. The water should flow through the pipe, and then you should turn down the pressure to stop the leak, replace the lever, and then increase the pressure.

One of the most common problems you can address with regular testing is the buildup of mineral salt, rust, and corrosion. When buildup occurs, the valve will become non-operational; the result can be an explosion. Regular testing helps you discover these issues sooner so you can combat them and keep your boiler and valve functioning properly. If no water flows through the pipe, or if there is a trickle instead of a rush of water, look for debris that is preventing the valve from seating properly. You may be able to operate the test lever a few times to correct the issue. You will need to replace the valve if this test fails.

When testing relief valves, keep in mind that they have two basic functions. First, they will pop off when the pressure exceeds its safety threshold. The valve will pop off and open to exhaust the excess pressure until the tank’s pressure decreases to reach the set minimum pressure. After this blowdown process occurs, the valve should reset and automatically close. One important testing safety measure is to use a pressure indicator with a full-scale range higher than the pop-off pressure.

Thus, you need to be aware of the pop-off pressure point of whatever tank or vessel you test. You always should remain within the pressure limits of the test stand and ensure the test stand is assembled properly and proof pressure tested. Then, take steps to ensure the escaping pressure from the valve is directed away from the operator and that everyone involved in the test uses safety shields and wears safety eye protection.

After discharge – Because pressure relief valves are designed to open automatically to relieve pressure in your system and then close, they may be able to open and close multiple times during normal operation and testing. However, when a valve opens, debris may get into the valve seat and prevent the valve from closing properly. After discharge, check the valve for leakage. If the leakage exceeds the original settings, you need to repair the valve.

According to local jurisdictional requirements – Regulations are in place for various locations and industries that stipulate how long valves may operate before needing to be repair or replaced. State inspectors may require valves to be disassembled, inspected, repaired, and tested every five years, for instance. If you have smaller valves and applications, you can test the valve by lifting the test lever. However, you should do this approximately once a year. It’s important to note that ASME UG136A Section 3 requires valves to have a minimum of 75% operating pressure versus the set pressure of the valve for hand lifting to be performed for these types of tests.

Depending on their service and application– The service and application of a valve affect its lifespan. Valves used for clean service like steam typically last at least 20 years if they are not operated too close to the set point and are part of a preventive maintenance program. Conversely, valves used for services such as acid service, those that are operated too close to the set point, and those exposed to dirt or debris need to be replaced more often.

Pressure relief valves serve a critical role in protecting organizations and employees from explosions. Knowing how and when to test and repair or replace them is essential.

Safety valve for over pressure protection of steam boilers operating up to 250 psi. It is rated up to 250 psi and 406�F saturated steam. Model 6182 safety valves meet ASME code, Section I.

Safety relief valve for steam service on unfired pressure vessels. It is also used on accumulators, cleaners, and distillers. Model 6182 safety relief valves are rated up to 250 psi and 406�F of saturated steam and meet ASME code, Section VIII Steam.

Safety relief valve for air, gas and vapors. It is used on compressors, receivers, burners, dryers and other piping systems. Model 6182 safety relief valves are rated up to 300 psi and 406�F and meet ASME code, Section VIII Air.

A safety valve is a valve that acts as a fail-safe. An example of safety valve is a pressure relief valve (PRV), which automatically releases a substance from a boiler, pressure vessel, or other system, when the pressure or temperature exceeds preset limits. Pilot-operated relief valves are a specialized type of pressure safety valve. A leak tight, lower cost, single emergency use option would be a rupture disk.

Safety valves were first developed for use on steam boilers during the Industrial Revolution. Early boilers operating without them were prone to explosion unless carefully operated.

Vacuum safety valves (or combined pressure/vacuum safety valves) are used to prevent a tank from collapsing while it is being emptied, or when cold rinse water is used after hot CIP (clean-in-place) or SIP (sterilization-in-place) procedures. When sizing a vacuum safety valve, the calculation method is not defined in any norm, particularly in the hot CIP / cold water scenario, but some manufacturers

The earliest and simplest safety valve was used on a 1679 steam digester and utilized a weight to retain the steam pressure (this design is still commonly used on pressure cookers); however, these were easily tampered with or accidentally released. On the Stockton and Darlington Railway, the safety valve tended to go off when the engine hit a bump in the track. A valve less sensitive to sudden accelerations used a spring to contain the steam pressure, but these (based on a Salter spring balance) could still be screwed down to increase the pressure beyond design limits. This dangerous practice was sometimes used to marginally increase the performance of a steam engine. In 1856, John Ramsbottom invented a tamper-proof spring safety valve that became universal on railways. The Ramsbottom valve consisted of two plug-type valves connected to each other by a spring-laden pivoting arm, with one valve element on either side of the pivot. Any adjustment made to one of valves in an attempt to increase its operating pressure would cause the other valve to be lifted off its seat, regardless of how the adjustment was attempted. The pivot point on the arm was not symmetrically between the valves, so any tightening of the spring would cause one of the valves to lift. Only by removing and disassembling the entire valve assembly could its operating pressure be adjusted, making impromptu "tying down" of the valve by locomotive crews in search of more power impossible. The pivoting arm was commonly extended into a handle shape and fed back into the locomotive cab, allowing crews to "rock" both valves off their seats to confirm they were set and operating correctly.

Safety valves also evolved to protect equipment such as pressure vessels (fired or not) and heat exchangers. The term safety valve should be limited to compressible fluid applications (gas, vapour, or steam).

For liquid-packed vessels, thermal relief valves are generally characterized by the relatively small size of the valve necessary to provide protection from excess pressure caused by thermal expansion. In this case a small valve is adequate because most liquids are nearly incompressible, and so a relatively small amount of fluid discharged through the relief valve will produce a substantial reduction in pressure.

Flow protection is characterized by safety valves that are considerably larger than those mounted for thermal protection. They are generally sized for use in situations where significant quantities of gas or high volumes of liquid must be quickly discharged in order to protect the integrity of the vessel or pipeline. This protection can alternatively be achieved by installing a high integrity pressure protection system (HIPPS).

In the petroleum refining, petrochemical, chemical manufacturing, natural gas processing, power generation, food, drinks, cosmetics and pharmaceuticals industries, the term safety valve is associated with the terms pressure relief valve (PRV), pressure safety valve (PSV) and relief valve.

The generic term is Pressure relief valve (PRV) or pressure safety valve (PSV). PRVs and PSVs are not the same thing, despite what many people think; the difference is that PSVs have a manual lever to open the valve in case of emergency.

Relief valve (RV): an automatic system that is actuated by the static pressure in a liquid-filled vessel. It specifically opens proportionally with increasing pressure

Pilot-operated safety relief valve (POSRV): an automatic system that relieves on remote command from a pilot, to which the static pressure (from equipment to protect) is connected

Low pressure safety valve (LPSV): an automatic system that relieves static pressure on a gas. Used when the difference between the vessel pressure and the ambient atmospheric pressure is small.

Vacuum pressure safety valve (VPSV): an automatic system that relieves static pressure on a gas. Used when the pressure difference between the vessel pressure and the ambient pressure is small, negative and near to atmospheric pressure.

Low and vacuum pressure safety valve (LVPSV): an automatic system that relieves static pressure on a gas. Used when the pressure difference is small, negative or positive and near to atmospheric pressure.

In most countries, industries are legally required to protect pressure vessels and other equipment by using relief valves. Also, in most countries, equipment design codes such as those provided by the ASME, API and other organizations like ISO (ISO 4126) must be complied with. These codes include design standards for relief valves and schedules for periodic inspection and testing after valves have been removed by the company engineer.

Today, the food, drinks, cosmetics, pharmaceuticals and fine chemicals industries call for hygienic safety valves, fully drainable and Cleanable-In-Place. Most are made of stainless steel; the hygienic norms are mainly 3A in the USA and EHEDG in Europe.

The first safety valve was invented by Denis Papin for his steam digester, an early pressure cooker rather than an engine.steelyard" lever a smaller weight was required, also the pressure could easily be regulated by sliding the same weight back and forth along the lever arm. Papin retained the same design for his 1707 steam pump.Greenwich in 1803, one of Trevithick"s high-pressure stationary engines exploded when the boy trained to operate the engine left it to catch eels in the river, without first releasing the safety valve from its working load.

Although the lever safety valve was convenient, it was too sensitive to the motion of a steam locomotive. Early steam locomotives therefore used a simpler arrangement of weights stacked directly upon the valve. This required a smaller valve area, so as to keep the weight manageable, which sometimes proved inadequate to vent the pressure of an unattended boiler, leading to explosions. An even greater hazard was the ease with which such a valve could be tied down, so as to increase the pressure and thus power of the engine, at further risk of explosion.

Although deadweight safety valves had a short lifetime on steam locomotives, they remained in use on stationary boilers for as long as steam power remained.

Weighted valves were sensitive to bouncing from the rough riding of early locomotives. One solution was to use a lightweight spring rather than a weight. This was the invention of Timothy Hackworth on his leaf springs.

These direct-acting spring valves could be adjusted by tightening the nuts retaining the spring. To avoid tampering, they were often shrouded in tall brass casings which also vented the steam away from the locomotive crew.

The Salter coil spring spring balance for weighing, was first made in Britain by around 1770.spring steels to make a powerful but compact spring in one piece. Once again by using the lever mechanism, such a spring balance could be applied to the considerable force of a boiler safety valve.

The spring balance valve also acted as a pressure gauge. This was useful as previous pressure gauges were unwieldy mercury manometers and the Bourdon gauge had yet to be invented.

Paired valves were often adjusted to slightly different pressures too, a small valve as a control measure and the lockable valve made larger and permanently set to a higher pressure, as a safeguard.Sinclair for the Eastern Counties Railway in 1859, had the valve spring with pressure scale behind the dome, facing the cab, and the locked valve ahead of the dome, out of reach of interference.

In 1855, John Ramsbottom, later locomotive superintendent of the LNWR, described a new form of safety valve intended to improve reliability and especially to be tamper-resistant. A pair of plug valves were used, held down by a common spring-loaded lever between them with a single central spring. This lever was characteristically extended rearwards, often reaching into the cab on early locomotives. Rather than discouraging the use of the spring lever by the fireman, Ramsbottom"s valve encouraged this. Rocking the lever freed up the valves alternately and checked that neither was sticking in its seat.

A drawback to the Ramsbottom type was its complexity. Poor maintenance or mis-assembly of the linkage between the spring and the valves could lead to a valve that no longer opened correctly under pressure. The valves could be held against their seats and fail to open or, even worse, to allow the valve to open but insufficiently to vent steam at an adequate rate and so not being an obvious and noticeable fault.Rhymney Railway, even though the boiler was almost new, at only eight months old.

Naylor valves were introduced around 1866. A bellcrank arrangement reduced the strain (percentage extension) of the spring, thus maintaining a more constant force.L&Y & NER.

All of the preceding safety valve designs opened gradually and had a tendency to leak a "feather" of steam as they approached "blowing-off", even though this was below the pressure. When they opened they also did so partially at first and didn"t vent steam quickly until the boiler was well over pressure.

The quick-opening "pop" valve was a solution to this. Their construction was simple: the existing circular plug valve was changed to an inverted "top hat" shape, with an enlarged upper diameter. They fitted into a stepped seat of two matching diameters. When closed, the steam pressure acted only on the crown of the top hat, and was balanced by the spring force. Once the valve opened a little, steam could pass the lower seat and began to act on the larger brim. This greater area overwhelmed the spring force and the valve flew completely open with a "pop". Escaping steam on this larger diameter also held the valve open until pressure had dropped below that at which it originally opened, providing hysteresis.

These valves coincided with a change in firing behaviour. Rather than demonstrating their virility by always showing a feather at the valve, firemen now tried to avoid noisy blowing off, especially around stations or under the large roof of a major station. This was mostly at the behest of stationmasters, but firemen also realised that any blowing off through a pop valve wasted several pounds of boiler pressure; estimated at 20 psi lost and 16 lbs or more of shovelled coal.

Pop valves derived from Adams"s patent design of 1873, with an extended lip. R. L. Ross"s valves were patented in 1902 and 1904. They were more popular in America at first, but widespread from the 1920s on.

Although showy polished brass covers over safety valves had been a feature of steam locomotives since Stephenson"s day, the only railway to maintain this tradition into the era of pop valves was the GWR, with their distinctive tapered brass safety valve bonnets and copper-capped chimneys.

Developments in high-pressure water-tube boilers for marine use placed more demands on safety valves. Valves of greater capacity were required, to vent safely the high steam-generating capacity of these large boilers.Naylor valve) became more critical.distilled feedwater and also a scouring of the valve seats, leading to wear.

High-lift safety valves are direct-loaded spring types, although the spring does not bear directly on the valve, but on a guide-rod valve stem. The valve is beneath the base of the stem, the spring rests on a flange some height above this. The increased space between the valve itself and the spring seat allows the valve to lift higher, further clear of the seat. This gives a steam flow through the valve equivalent to a valve one and a half or twice as large (depending on detail design).

The Cockburn Improved High Lift design has similar features to the Ross pop type. The exhaust steam is partially trapped on its way out and acts on the base of the spring seat, increasing the lift force on the valve and holding the valve further open.

To optimise the flow through a given diameter of valve, the full-bore design is used. This has a servo action, where steam through a narrow control passage is allowed through if it passes a small control valve. This steam is then not exhausted, but is passed to a piston that is used to open the main valve.

There are safety valves known as PSV"s and can be connected to pressure gauges (usually with a 1/2" BSP fitting). These allow a resistance of pressure to be applied to limit the pressure forced on the gauge tube, resulting in prevention of over pressurisation. the matter that has been injected into the gauge, if over pressurised, will be diverted through a pipe in the safety valve, and shall be driven away from the gauge.

There is a wide range of safety valves having many different applications and performance criteria in different areas. In addition, national standards are set for many kinds of safety valves.

Safety valves are required on water heaters, where they prevent disaster in certain configurations in the event that a thermostat should fail. Such a valve is sometimes referred to as a "T&P valve" (Temperature and Pressure valve). There are still occasional, spectacular failures of older water heaters that lack this equipment. Houses can be leveled by the force of the blast.

Pressure cookers usually have two safety valves to prevent explosions. On older designs, one is a nozzle upon which a weight sits. The other is a sealed rubber grommet which is ejected in a controlled explosion if the first valve gets blocked. On newer generation pressure cookers, if the steam vent gets blocked, a safety spring will eject excess pressure and if that fails, the gasket will expand and release excess pressure downwards between the lid and the pan. Also, newer generation pressure cookers have a safety interlock which locks the lid when internal pressure exceeds atmospheric pressure, to prevent accidents from a sudden release of very hot steam, food and liquid, which would happen if the lid were to be removed when the pan is still slightly pressurised inside (however, the lid will be very hard or impossible to open when the pot is still pressurised).