air compressor safety valve keeps opening supplier

If the tank is over pressurized, the pressure switch isn"t shutting off the motor when the air tank fills to the cut-out pressure. Move the pressure switch lever to the off position. If the compressor continues to run, replace the pressure switch, because the switch isn"t shutting off the compressor motor.

If the compressor shuts off when you move the pressure switch lever to the off position, pull the safety valve ring and release all air from the tank. Switch the pressure switch lever to the on position and allow the tank to fill. If the compressor doesn"t shut off when the air tank fills to the cut-out pressure, replace the pressure switch, because the switch isn"t shutting off the compressor motor when tank pressure reaches the cut-out pressure.

Today I am going to explain why this happens and how you can fix it. But first, I would like to give a short introduction about a safety valve and how it works, if you are not familiar with it.

It is also called a pressure relief valve as it reliefs pressure whenever the compressor pressure reaches a critical point. Usually, the pressure level of a safety valve is kept below to the maximum pressure that a compressor can take.

Whenever the pressure of your compressor is about to reach this maximum level, the safety valve will relief air from the compressor so that the pressure drops.

A safety valve follows a very simple mechanism to work. Here is how it actually works –There is a Nozzle inside the valve. From the inlet part of the valve, this nozzle first gets an amount of pressure on it. In other words, the nozzle is there to inlet the air at a certain pressure.

You have to set a pressure level initially for a safety valve. As I have already said, this pressure needs to be lower than the compressor’s maximum pressure level. When the nozzle reaches this pressure, the Disc inside the valve starts to lift and relief the air from the tank.

There is a Spring inside the valve, which is attached to the disc. The spring is made in such a way that it will only bend when the pressure reaches the level you have set. So, the disc is lifted up and drawn down by the spring.

There are a number of components inside a safety valve but it is typically three main components, the nozzle, the disc, and the spring. You have already known how these three components work.

However, if any of these three components get damaged, then the problem begins. For example –If the nozzle is not functioning properly, there will be a problem with the air inlet. In this case, it will accidentally push a lot of air inside the valve and the valve will open.

Finally, if the spring is old or damaged, then it will lift up the disc way before it reaches the set pressure. In this case, air will also discharge from the valve.

Another reason for a safety valve to pop open is when the pressure switch is damaged. A pressure switch has a very serious function in an air compressor. It is set with two pressure level, a cut-out, and a cut-in pressure.

When the pressure switch reads the cut in pressure from the pump, it starts to run the compressor. And, when the pressure reaches the cut-out level, it shuts the compressor down.

In this case, the compressor will go to critical pressure level. When it happens, the safety valve will automatically pop open. This is how the pressure switch is responsible for the safety valve to open suddenly.

There are a number of ways that you can follow to stop a safety valve from opening suddenly. Here are the best ways to keep your compressors safety valve from opening unnecessarily.At first, check if the internal part of the safety valve is damaged or not. If you find a damaged part (i.e. the nozzle or the disc) replace this part and it should be fine.

If you cannot replace the damaged part of the safety valve, you can simply change this safety valve and place a new one. A newer safety valve is always better than a repaired one.

The pressure switch is also responsible for this. So if you don’t find any problems with the safety valve, then check the pressure switch. If the pressure switch is broken, change it.

Sometimes, there are troubles with adjusting the pressure switch. If you are also having trouble, check out this article on air compressor pressure switch adjustment to adjust your pressure switch.

First of all, you need to find out how much pressure your air compressor can take. You will see there is an option to set a pressure level on the safety valve.

When you find out your compressors limit, you can set the pressure level on the safety valve according to that limit. Always use a lower pressure level than the maximum level of pressure that a compressor can take.

The purpose of a safety valve is to discharge air from the compressor when the pressure level reaches too high. High pressure can explode the tank and cause critical accidents. To stop this from happening, a safety valve is used on a compressor.

Most of the safety valves are built to last for years. An average safety valve can easily last for 18 to 24 months. However, you should frequently test your safety valve and change it if there is the slightest chance of malfunctioning. Never take the risk of keeping a faulty safety valve attached to your compressor.

In most cases, you should check your safety valve at least once a month to see if it is in good condition or not. But I recommend you to check at least once every time it discharges.

You already know how to fix it if the air compressor safety valve keeps opening, but it is also important to test the safety valve when it discharges.

Because after discharge it will leave debris around the nozzle and the disc. You have to clean this to keep the safety valve away from malfunctioning.

However, it is not a big issue to fix the safety valve. Depending on the model and the manufacturer of the compressor, the type of valve may vary. So, you will have to act accordingly.

Here we are going to discuss the causes of issues in the air compressor safety valve. Also, we are sharing the steps that you could take to solve the matter.

Suppose you are working with an air compressor for your home garage. Now based on your project, you will set the air pressure. But it is not a surprising fact that the pressure may reach a higher psi. In that case, the safety valve or pressure releasing valve will open and release the access air. Thus, it helps to keep the air compressor safe.

The primary reason for the air compressor safety valve staying open is a damaged pressure valve. It also could be the compressor pressure switch that controls the air circulation in the compressor. A faulty pressure switch won"t be able to shut the motor to control the air, and as a result, the safety valve remains open.

The safety valve attached to the compressor usually comes with a nozzle in it. This nozzle helps to inlet air from the compressor when needed. If the nozzle has any leakage or it is damaged internally, there is a good chance that the safety valve will stay open.

On the other hand, the valve itself could get damaged because of usages. For both of these issues, the relief valve may blow air from the compressor, and you won"t get enough air pressure for your projects. It usually happens when you buy a cheap air compressor without checking the quality.

The Air compressor is built with several parts, and the pressure switch is one of the most crucial parts. The pressure switch is designed to monitor pressurized air from the tank. It reacts depending on the applied pressure on it, and it is used to maintain through a diaphragm.

The pressure switch creates a backward pressure or cut-out pressure when there is high pressure inside the compressor. In that case, the diaphragm will be deformed to break the contact inside the switch and the power will shut down. At this point, you will see the air compressor safety valve keeps blowing.

Now for any reason, if the pressure switch is damaged or not working in the right way, even if the air pressure is not high, it will try to release air through the safety valve. As a result, the relief valve keeps opening even though it is not necessary.

Step-1: Set the pressure limit for the safety valve according to the manufacturer"s instructions. If the pressure limit is lower than the instructed point, reset it by changing the pressure limit

Step-2: Check for the damages to the valve and the nozzle attached to it. If there is an issue with the nozzle and it inlets air without reaching the optimum level, you need to replace it.

Step-4: Inside the compressor, the safety valve used to have a small spring that bends when the pressure reached the level you have set. It lifts the disc in the air compressor to release excess air. If the spring is not bending properly, replace it from the inside.

Step-5: Check the pressure switch of the compressor. Try to identify if it can monitor the cut-in and cut-out pressure. If it fails to monitor the pressure level, probably it is damaged, and you need to replace it.

For air compressor pressure relief valve adjustment, turn off the compressor. Now remove the cover from the valve with a screwdriver. There you will see a big set screw to adjust the pressure. Use a Flathead screwdriver to adjust the screw. If you want to increase the limit, turn the screw clockwise and check the shut-off point. To reduce the pressure level, just turn the screw anticlockwise. Once you find the desired level, attach the cover, and you are ready to go.

If your air compressor PRV valve is faulty and doesn"t work accurately, you need to replace it. To replace the safety valve, you need to remove the previous one. For this, you may have to remove the meter from the top.

Now you should get access to the safety valve. Use a wrench and hold the pressure valve tightly. Turn it anticlockwise until it comes off from the air compressor. Add the new safety valve and secure it at the right point. Apply the wrench to secure the valve and turn it clockwise until it gets set on the compressor.

If you have read the article thoroughly, you won"t be disappointed again if the compressor relief valve keeps opening. Find out the exact issue as described in this article. Solve the problem by following the guideline described here, and you will be ready for the next project.

Listen, if your PRV is going off and the pressure in the tank is higher than the normal cut off pressure for that compressor, that means that the pressure in your tank is above the safety release pressure of your compressor system.

That your pressure continues to rise after your compressor has achieved high pressure cut-out in the tank, and the compressor continues to compress air without shutting off, you’ve got a pressure switch problem.

My ebook, The Home Compressor, covers many aspects of troubleshooting the home compressor, including changing out the pressure switch. Check it out on this site soon if you get the chance.

That your PRV is “popping” at all tells me that your compressor pressure switch cut out pressure level is too high for, or your PRV isn’t suited to, the compressor.

I can’t tell you if the 130 PSI “pop off” is right for your compressor, though that cracking pressure sure seems a bit low, since PRV’s are a safety device and are the last line of defense if the pressure switch fails and prevents a tank over pressure.

If it were me, I’d take the PRV out of the line, and run the compressor, keeping a careful watch on the tank pressure level. Be ready to turn the motor off. Watch the pressure. Maybe the pressure switch is set to shut off at, say, 150 PSI (which is not a too high range normally) and the compressor will shut off then.

That being the case, visit your local compressor repair shop and ask to buy a PRV that opens at about 10 PSI higher than the cut off, and one that needs a manual reset.

Is the aftercooler between cylinders? If so, that would suggest a failing intake valve in the second cylinder. If the aftercooler is between the cylinder and the tank, that may mean a stuck or slow tank check valve.

You may not worry often, if at all, about whether or not your air compressor is running safely. And you really don’t have to, because compressor manufacturers do. From the pressure rating on the air storage tank to emergency stop buttons, air compressors are designed with safety in mind.

But that doesn’t mean you should never think about your compressor’s safety features. In most cases, they need to be inspected regularly to make sure they’re working properly. One key safety feature that should be inspected regularly is the air pressure relief valve (PRV), sometimes called a safety relief valve.

The pressure relief valve is a safety valve that protects the compressor component that it’s attached to from being exposed to a pressure above its rated maximum operating pressure. This rating, called the maximum working pressure (MWP), is the pressure that the vessel has been certified to continuously operate at safely.

So when a compressor is running at or below its maximum working pressure—in other words, when it’s running “normally”—the relief valve doesn’t do anything.

However, when the air pressure inside a compressor exceeds its MWP, the pressure relief valve will activate to “blow off” the excessive pressure within the compressor. Without a relief valve, the storage tank could rupture from the excessive pressure, damaging the compressor itself, possibly other property near it, and even causing injuries (or worse) to anyone standing nearby.

Before we can talk about how the air pressure relief valve works, we first need to look at how air pressure inside a compressor is managed when everything is running normally.

Under normal circumstances, the air pressure in a compressor is controlled by a pressure switch in an electro/mechanical control system or, in the case of an electronic controller, a pressure transducer and controller settings. When the cut-out set pressure for the pressure switch is reached, the compressor will stop compressing air (unload) until the cut-in set pressure is reached, at which time it will start compressing air again (load). If the pressure switch fails, the compressor would not be able to start compressing air again, or potentially worse, not be able to stop. Most compressors also have a high-pressure safety switch that should stop the compressor if the pressure exceeds the unload set point.

A pressure relief valve is a straightforward safety backup to the pressure switch and high-pressure switch, or the controller set points, should any of these components fail with the compressor running. The safety relief valve is set above the high-pressure safety switch and generally at or below the vessel’s maximum operating pressure. Inside the valve is a spring, and the pressure created by the spring’s tension keeps the valve closed under normal operating conditions. However, as the air pressure increases in pressure vessels (like the storage tank), it eventually exceeds the rated pressure of the relief valve, causing the relief valve to open and the excess pressure to be “blown off” to the atmosphere.

If the pressure relief valve fails open, air will continually vent to the atmosphere, preventing the air stream from becoming fully pressurized. The compressor should be shut down and the relief valve replaced before the compressor is restarted. The open relief valve will likely cause a loss of production and possible danger to personnel as a result of the flow of high-pressure air with flying debris and an unsafe sound level.

A pressure relief valve failing closed presents a potentially more dangerous situation. As noted earlier, the relief valve exists to allow excessive pressure to be “blown off” so that the air pressure inside the compressor’s pressure vessels don’t exceed their rated specifications. If the valve fails closed, this pressure venting can’t happen. Unless compressed air demand matches the compressed air supply, the pressure inside the compressor will continue to build. Eventually, the pressure increase would cause the storage tank to rupture, damaging the compressor and possibly causing additional damage and injury to property and people nearby.

If the relief valve is opening because the air pressure in the compressor has exceeded the valve’s pressure set point, that means the valve is working and doing what it was designed to do. But because this indicates the MWP of the compressor has been exceeded, the condition that’s causing excessive pressure should be diagnosed and corrected.

If the relief valve opening wasn’t caused by excessive pressure inside the compressor, then the valve is most likely “failing open”. Most likely, this is because the valve has become “soft” over time, i.e. the valve spring is providing less counterpressure, so it’s opening at a lower pressure than it should.

Whether the valve opened because of excessive pressure in the compressor or because the valve is failing, you should have your local air compressor distributor inspect your compressor before running it again for two reasons:

First, your distributor can determine whether the valve opened due to a failing relief valve or excessive compressors pressure and perform any needed maintenance or service to get your compressor running efficiently and safely again.

Second, regardless of why the pressure relief valve opened, replacing it may be recommended to ensure safe compressor operation, depending on the valve manufacturer. (Replacement is recommended for Sullair compressors.)

Important: Running the compressor after the relief valve has opened, regardless of the reason why it opened, can put both your property at risk of damage and people at risk of injury (or worse). While this may be obvious if the compressor is building up excess pressure, it also applies if the valve failed open. As noted above, even a valve that fails open poses some risk, and next time it could fail closed.

Given how critical a working air pressure relief valve is to the safe and efficient operation of your air compressor, you may wonder whether you need to do any regular inspecting or testing of the valve to make sure it is working. Because this can vary by manufacturer, you should consult your owner’s manual or contact your local air compressor distributor for frequency and type of inspection needed. For most Sullair compressors, inspection for damage or leakage is recommended, but testing is not recommended, as doing so may compromise the valve’s performance.

However, one thing you should do is schedule regular maintenance with your local air compressor distributor. As part of regular maintenance, a service technician can inspect the PRV and let you know it’s at an age or in a condition at which the manufacturer recommends replacement. Also, problems with the compressor’s performance, e.g. not reaching normal operating pressure, may help the service technician identify a failing relief valve after ruling out other possible causes.

When a pressure vessel like a receiver, sump tank or other storage vessel is purchased separately from the compressor, it may not be supplied with a pressure relief valve. To ensure its safe operation, you should add a PRV.

When selecting a PRV to add to the pressure vessel, you must choose a valve with a pressure set point set at or below the maximum working pressure of the vessel. You will find the MWP (and other useful information) on a tag welded to the pressure vessel. Also, flow capacity of the PRV must meet or exceed the total compressed air supplied to the vessel.

For example, if you have two compressors with capacities of 500 and 750 cfm (14.2 and 21.2 m³/min), and a pressure vessel with a maximum working pressure of 200 psi (13.8 bar), the minimum settings for a pressure relief valve would be 1250 cfm (35.4 m³/min) and a set point 200 psi (13.8 bar) or less.

Finally, when attaching the valve to the vessel, the porting must not be reduced to a size less than the size of the inlet port of the pressure relief valve.

Because the pressure relief valve is critical to the safe operation of your compressed air system, if you’re not sure how to select the correct PRV and properly and safely add it to the pressure vessel, contact your local air compressor distributor. They have the experience and expertise to ensure that the PRV is sized and installed correctly.

Conventionally when we talk about oil lubricated screw air compressor maintenance, it is mostly about replacing consumables such as filters and lubricant on time. While these consumables have a defined usable life and have a direct effect on the efficiency and the life of the air compressor itself when not replaced on time, there are a few critical valves in the air compressor that require maintenance as well. Compressor valves directly affect the efficiency, safety, and the functionality of the screw air compressor. Let us understand some of the commonly available valves in a screw air compressor, why they need maintenance, and discuss some of the frequently asked questions about screw air compressor valves.

A screw air compressor is very similar to a human heart. While a human heart has tricuspid, pulmonary, mitral, and aortic valves, a screw air compressor has four critical valves namely air inlet, minimum pressure, blow down, and safety valves.

Air inlet valve is also commonly known as the ‘Intake valve’ which is typically assembled on the airend’s intake. The air inlet valve of a conventional fixed speed screw air compressor controls the air intake into the compressor. It remains closed when the compressor starts to lower the starting load on the main motor and when the desired working pressure is attained in the compressed air circuit and thus enabling the compressor’s motor to run without any load. In some compressors that are capable of providing a variable output by modulating the amount of air it sucks in, the inlet valve holds various opening positions to regulate the volume of air entering the compressor. The effective performance of the inlet valve directly affects the compressor’s capacity and its power consumption during load and no-load conditions.

The minimum pressure valve is typically assembled on the exit of the air-oil separation tank of a compressor. The minimum pressure valve acts as a check valve preventing back flow of compressed air into the airend, retains a minimum pressure in the compressor system for lubrication, offers a restriction to avoid a collapse of the air-oil separation filter, and ensures a suitable velocity of flow across the air-oil separator that ensures efficient air-oil separation. The effective performance of the minimum pressure valve directly affects the compressor’s lubrication, air-oil separation efficiency, and power consumption during load and no-load conditions.

The blow down valve is typically found on a dedicated exhaust line from the air-oil separation tank. The blow down valve evacuates the compressed air in the air-oil separation tank each time the compressor runs on a no-load and when the compressor shuts down to ensure there is no back pressure when the compressor starts to load next time. The blow down valve of a conventional screw compressor is typically actuated by a solenoid valve. The effective performance of the blow down valve affects the compressor’s power consumption during un-load, capacity of the compressor when running on load, and the life of the motor.

The safety valve is typically mounted directly on the air-oil separator tank. The only function of the safety valve is to blow off the compressed air in the air-oil separation tank when the pressure in the air-oil separation tank exceeds the set pressure of the safety valve and there by prevents the tank from cracking under high pressure. A malfunctioning safety valve affects the safe operation of the air compressor or results in leakage of compressed air continuously.

Though each compressor manufacturer has their own unique valve design, compressor valves in general contain moving parts such as springs, valve plates, and plungers that affect the opening and closing of the valves and rubber seals / seats that offer perfect sealing when the valves remain closed. These moving parts wear or lose their mechanical properties over a period of time and the sealing components typically ‘age’ over time and lose their effectiveness and will need to be replaced.

Compressor manufacturers typically design these components to operate efficiently for several thousand or millions of operation cycles. However, several factors such as variability in the demand pattern, sizing of the air compressor against a certain air demand, the environment in which the air compressor operates, promptness of preventive maintenance, etc. determine how long these valves efficiently operate.

Many times, it is difficult to identify a malfunctioning valve or a valve operating with worn-out parts as the compressor continues to generate air. The typical symptoms of a malfunctioning valve are loss in compressor"s capacity, increase in power consumption during load or/and unload, drop in discharge pressure, increase in oil carry-over and more load on motor. These symptoms are either difficult to notice or have other frequently common assignable causes such as air leak before suspecting the compressor valves.

Case studies show that operating a screw air compressor with a worn-out / malfunctioning valve could increase its overall power consumption by 10 - 15%. Power cost contributes to more than 75% of the compressor’s total life cycle cost over ten years and hence this is a significant impact. Unserviced valves also lower the life span of downstream accessories by half. In some cases, a malfunctioning safety valve may result in a catastrophe.

Air compressor manufacturers typically offer convenient valve maintenance kits for customers that contain the internal parts of the valve that wear or age out. Changing the valve kits is a much more sensible and economical option than changing the complete valve.

It is difficult or almost impossible to identify a malfunctioning valve unless it is opened for inspection. Hence it is absolutely mandatory that these valves are inspected for effectiveness every year and the internal moving parts replaced as a part of preventive maintenance once every year or two depending on the operating conditions of the air compressor. It is typical for compressor manufacturers to mandate a valve kit replacement once every two years as a proactive measure.

In particular, the safety valve must be inspected and certified every year per the local safety laws to ensure they are functional and efficient. Sometimes, replacing the safety valve entirely with a valid certificate for one year is more economical as the certification procedures could be equally expensive on an existing valve.

As stated before, it is challenging to identify a valve that is worn out unless it is opened and inspected, but there are a few indicators that a qualified compressor technician can use to deduct a malfunctioning valve.

Low duty cycle operation: A sophisticated screw air compressor in today’s day and age carries a convenient microprocessor-based human-machine interface that keeps track of operating hours of the compressor under load and un-load conditions and the number of load/unload counts the compressor is subjected to over a period of time. A higher un-load hours and load/unload count indicates that the air compressor is oversized against the actual air demand. This in turn indicates the air compressor ‘cycles’ frequently between load and un-load mode as opposed to running continuously on load. Every time a compressor ‘cycles’, the inlet valve, blow down valve, and minimum pressure valve is brought into play where their internals ‘actuate’. Frequent actuation of these valves results in a faster wear of the internals and hence results in shorter life.

High operating temperature: A compressor that runs on a high operating temperature affects the life of the valve’s sealing components, which causes them to ‘age’ fast.

Compressor not building pressure: If the air demand has not changed over time and the facility is relatively free of any air leakage, the air compressor is probably not delivering the rated output. There is a high probability that there is a malfunctioning valve.

Increase in compressor’s power consumption: An increase in the air compressor’s power consumption profile over a period of time where there has been no abnormal change in the air demand and usage pattern indicates an increase in either the load or un-load power. There is a high probability that this is because of a malfunctioning valve.

Based on the design philosophy adopted by the air compressor manufacturer, the oil lubricated screw air compressors could have a few more valves that are critical to functional performance that must be maintained as well. Some of the other valves frequently used in an air compressor are as follows:

Temperature control valve (also known as thermal valve) is used to regulate the flow of oil through the oil cooler based on the operating temperature.

Drain valves are used to drain lubricant at the time of lubricant change over or cleaning. Air compressors equipped with a moisture trap at the outlet of the after cooler also has a drain valve (automatic or timer based) to discharge water collected.

The presence or absence of one of these valves and the type of actuation of these valves (electronic / mechanical) depends on air compressor’s design architecture. The Operation and Maintenance Manual (OMM) and the Piping and Instrumentation Diagram (P&ID) supplied by the air compressor manufacturer are excellent resources that explain the purpose, functioning, and maintenance requirements of these valves.

Many of the air compressor valves are highly specialized and exclusive. Their designs are usually complex and some even need special tools to service them. The internal components" build quality and material selection are extremely important and proprietary. Hence it is highly critical that only genuine valve kits issued by the air compressor manufacturer are used to maintain the valves. An inferior after-market replacement will most certainly compromise the performance of the entire compressor, void the original manufacturer"s warranty of the compressor, cause consequential damage to other parts of the compressor, and above all, be a safety hazard.

In conclusion, while it is important to change the screw air compressor"s filters and lubricants on time, it is equally important to perform preventive maintenance on these critical valves in a screw air compressor as recommended by the air compressor manufacturer. While the intake valve, minimum pressure valve, safety valve, and blowdown valve are critical to the performance and safety of the compressor, there could be other valves in the compressor that are critical and need maintenance. The air compressors sizing and the environment in which it operates are crucial factors that affect the life of the air compressor. Finally, it is critical to proactively service these valves using genuine kits issued by the compressor manufacturer to enable the air compressor performs efficiently and safely.

Gershom Joel has over 15 years of experience in the compressed air field and specializes in helping industries such as Pharmaceuticals, Textile, Electronics, and Food and Beverage find compressed air solutions to meet their unique requirements.  Gershom holds a Mechanical Engineering Degree from Anna University and a Masters in Business Administration from University of North Carolina.

ELGi North America, headquartered in Charlotte, NC, is a subsidiary of ELGi Equipments Limited, a leader in compressed air solutions for over 60 years. Established in 2012, ELGi North America, in conjunction with its subsidiaries, Pattons, Pattons Medical, and Michigan Air Solutions, offers a comprehensive range of compressed air products and services. Our product offering includes oil-lubricated and oil-free rotary screw and reciprocating compressors, dryers, filters, and ancillary accessories. ELGi and its subsidiaries serve multiple industry verticals spanning medical applications, pharmaceuticals, food & beverage, construction, manufacturing, and infrastructure. For more information, visit https://www.elgi.com/us/.

Curtiss-Wright"s selection of Pressure Relief Valves comes from its outstanding product brands Farris and Target Rock. We endeavor to support the whole life cycle of a facility and continuously provide custom products and technologies. Boasting a reputation for producing high quality, durable products, our collection of Pressure Relief Valves is guaranteed to provide effective and reliable pressure relief.

While some basic components and activations in relieving pressure may differ between the specific types of relief valves, each aims to be 100% effective in keeping your equipment running safely. Our current range includes numerous valve types, from flanged to spring-loaded, threaded to wireless, pilot operated, and much more.

A pressure relief valve is a type of safety valve designed to control the pressure in a vessel. It protects the system and keeps the people operating the device safely in an overpressure event or equipment failure.

A pressure relief valve is designed to withstand a maximum allowable working pressure (MAWP). Once an overpressure event occurs in the system, the pressure relief valve detects pressure beyond its design"s specified capability. The pressure relief valve would then discharge the pressurized fluid or gas to flow from an auxiliary passage out of the system.

Below is an example of one of our pilot operated pressure relief valves in action; the cutaway demonstrates when high pressure is released from the system.

Air pressure relief valves can be applied to a variety of environments and equipment. Pressure relief valves are a safety valve used to keep equipment and the operators safe too. They"re instrumental in applications where proper pressure levels are vital for correct and safe operation. Such as oil and gas, power generation like central heating systems, and multi-phase applications in refining and chemical processing.

At Curtiss-Wright, we provide a range of different pressure relief valves based on two primary operations – spring-loaded and pilot operated. Spring-loaded valves can either be conventional spring-loaded or balanced spring-loaded.

Spring-loaded valves are programmed to open and close via a spring mechanism. They open when the pressure reaches an unacceptable level to release the material inside the vessel. It closes automatically when the pressure is released, and it returns to an average operating level. Spring-loaded safety valves rely on the closing force applied by a spring onto the main seating area. They can also be controlled in numerous ways, such as a remote, control panel, and computer program.

Pilot-operated relief valves operate by combining the primary relieving device (main valve) with self-actuated auxiliary pressure relief valves, also known as the pilot control. This pilot control dictates the opening and closing of the main valve and responds to system pressure. System pressure is fed from the inlet into and through the pilot control and ultimately into the main valve"s dome. In normal operating conditions, system pressure will prevent the main valve from opening.

The valves allow media to flow from an auxiliary passage and out of the system once absolute pressure is reached, whether it is a maximum or minimum level.

When the pressure is below the maximum amount, the pressure differential is slightly positive on the piston"s dome size, which keeps the main valve in the closed position. When system pressure rises and reaches the set point, the pilot will cut off flow to the dome, causing depressurization in the piston"s dome side. The pressure differential has reversed, and the piston will rise, opening the main valve, relieving pressure.

When the process pressure decreases to a specific pressure, the pilot closes, the dome is repressurized, and the main valve closes. The main difference between spring-loaded PRVs and pilot-operated is that a pilot-operated safety valve uses pressure to keep the valve closed.

Pilot-operated relief valves are controlled by hand and are typically opened often through a wheel or similar component. The user opens the valve when the gauge signifies that the system pressure is at an unsafe level; once the valve has opened and the pressure has been released, the operator can shut it by hand again.

Increasing pressure helps to maintain the pilot"s seal. Once the setpoint has been reached, the valve opens. This reduces leakage and fugitive emissions.

At set pressure the valve snaps to full lift. This can be quite violent on large pipes with significant pressure. The pressure has to drop below the set pressure in order for the piston to reseat.

At Curtiss-Wright we also provide solutions for pressure relief valve monitoring. Historically, pressure relief valves have been difficult or impossible to monitor. Our SmartPRV features a 2600 Series pressure relief valve accessorized with a wireless position monitor that alerts plant operators during an overpressure event, including the time and duration.

There are many causes of overpressure, but the most common ones are typically blocked discharge in the system, gas blowby, and fire. Even proper inspection and maintenance will not eliminate the occurrence of leakages. An air pressure relief valve is the only way to ensure a safe environment for the device, its surroundings, and operators.

A PRV and PSV are interchangeable, but there is a difference between the two valves. A pressure release valve gradually opens when experiencing pressure, whereas a pressure safety valve opens suddenly when the pressure hits a certain level of over pressurization. Safety valves can be used manually and are typically used for a permanent shutdown. Air pressure relief valves are used for operational requirements, and they gently release the pressure before it hits the maximum high-pressure point and circulates it back into the system.

Pressure relief valves should be subject to an annual test, one per year. The operator is responsible for carrying out the test, which should be done using an air compressor. It’s imperative to ensure pressure relief valves maintain their effectiveness over time and are checked for signs of corrosion and loss of functionality. Air pressure relief valves should also be checked before their installation, after each fire event, and regularly as decided by the operators.

Direct-acting solenoid valves have a direct connection with the opening and closing armature, whereas pilot-operated valves use of the process fluid to assist in piloting the operation of the valve.

A control valve works by varying the rate of fluid passing through the valve itself. As the valve stem moves, it alters the size of the passage and increases, decreases or holds steady the flow. The opening and closing of the valve is altered whenever the controlled process parameter does not reach the set point.

Control valves are usually at floor level or easily accessible via platforms. They are also located on the same equipment or pipeline as the measurement and downstream or flow measurements.

An industrial relief valve is designed to control or limit surges of pressure in a system, most often in fluid or compressed air system valves. It does so as a form of protection for the system and defending against instrument or equipment failure. They are usually present in clean water industries.

A PRV is often referred to as a pressure relief valve, which is also known as a PSV or pressure safety valve. They are used interchangeably throughout the industry depending on company standards.