air compressor safety valve keeps opening for sale

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.

air compressor safety valve keeps opening for sale

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.

air compressor safety valve keeps opening for sale

So about a year ago the original safety valve failed. It kept popping before full pressure. Tank pressure reads 145-150psi when it blows. Tanks rated and used to fill 170ish before it would cut off.

air compressor safety valve keeps opening for sale

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.

air compressor safety valve keeps opening for sale

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air compressor safety valve keeps opening for sale

A few years ago I posted about Conrader air safety valves, and how they can safely vent air tank pressure should the pressure exceed the valve’s manufactured threshold.

That is, if a compressed air tank rises above say 100 PSI, a 100 PSI safety valve will open and release a sufficient amount of air so as to lower the tank pressure to ~100 PSI.

What happens when you pressurize an air tank beyond its rated pressure? It fails catastrophically and ruptures in a spectacular way that you wouldn’t want to witness firsthand.

But what does it do when installed to a portable air compressor? What could happen in a portable air compressor that doesn’t have one of these valves?

I hope you don’t mind, but I need to think aloud for a bit, meaning none of this is at 100% confidence and should be considered as my opinion and not safety advice or complete understanding of any kind.

Yes, a safety valve prevents tank pressure from building up past its recommended and tested pressures. If a portable air compressor is rated to say 125 PSI max, you don’t want that tank to build to 250 PSI holding pressure.

I don’t think it’s so much the risk of the air tank failing, as there should be a sufficient safety factor built into its specs, but perhaps other components could be more susceptible to damage?

Let’s say that a portable compressor’s pressure sensor fails somehow, and it misses its cut-off pressure. So instead of turning off an air pump once the tank pressure reaches its max operating pressure, the pump continues to run.

Let’s say you have a inflatable device and a hand pump. The higher the pressure in the inflatable device, be it a ball, tire, or other object, the greater resistance you will feel when operating the manual air pump. The parallel would be an electric pump seeing an increased load during air compression.

If the air tank pressure isn’t accurately measured or reported by the pressure sensor responsible for turning the compressor pump on and off, then in a hypothetical situation the compressor might continue to pump and pump and pump until something else stops it. What could this lead to?

Every component of every tool has a purpose. The implementation of safety valves in air compressor tanks make sense – it reduces the tank pressure should the pressure exceed an established maximum. Navigating the WHY has been difficult. What if a portable air compressor does not have one?

How often do air compressor pressure sensors fail? It perhaps seems more likely that safety valves are mostly intended simply to help regulate the maximum holding pressure. Let’s say you operate an air compressor outdoors in winter, and it continues to fill up until it reaches temperature equilibrium. Then you take it inside. If the temperature increases several dozen degrees as the tank reaches a new equilibrium with indoor temperatures, the pressure will increase. Having a safety air valve ensures that the tank pressure, which will rise with the temperature, won’t exceed the system’s maximum rating.

There are fewer questions when it comes to standalone air tanks, where the safety valve is there to protect the tank from exceeding its maximum holding pressure rating. So am I overthinking things when it comes to portable air compressors that have an integrated air tank?

This seemed like an interesting and worthwhile topic to think about aloud. I also know some of you are experienced with industrial air compression systems, and others might have experienced product failures or even taken part in testing portable compressors to failure. I would even bet that maybe one or two readers will have surely designed or engineered one or more portable air compressors, or taken part in the development of such products.

Beyond the obvious, to protect tank integrity, what other causes or reasons might there be to have a safety pressure valve installed into a compressed air tank?

Or, what could happen to the components of a portable air compressor if the tank pressure exceeds its rated holding pressure? What are all of the possible modes of failure? Might tank overpressure cause other components to fail or break much earlier and with greater likelihood than the tank bursting?

One thing that’s for certain is that I wouldn’t use a portable air compressor with built-in air tank or standalone air tank that didn’t have a safety valve.