It’s like a bomb.
Yeah, a compressor is like a bomb when you can’t control the pressure input.
Because of zero pressure control, you won’t even notice high-pressure buildup inside your compressor.
Give it a little more time, and soon this unnoticed problem will bring in huge damage. Moreover, this damage can even get fatal.
Here’s the thing-
Your pressure relief valve is the last resort in compressor pressure control.
To detect an air compressor pressure relief valve problem, you have to look out for certain symptoms like air bleeding, pressure deficit, etc. Moreover, you have to keep a close eye towards your pressure gauge.
Most of the times the solution is to change the pressure relief valve and to clean it.
Here, we’ve discussed the work of pressure relief valve, reasons behind the problems of pressure relief valves and solutions to those problems. Besides these, we’ll discuss the adjusting method of air compressor pressure relief valve adjustment and safety measures.
So, let’s jump right into the details without any further delay-
Table of Contents
Pressure Relief Valve Working Principle
A pressure relief valve comes into play if the compressor pressure switch stops working.
So, what’s its purpose?
Just like the name suggests, its purpose is to relief pressure.
The pressure switch turns the compressor on and off based on the pressure build up. If the pressure reaches the higher limit, then the pressure switch turns off the compressor.
When pressure switch fails, your compressor plunges in more and more air. At that point, your second safety measure, the pressure relief valve kicks in.
Before the pressure reaches a dangerous level, your pressure relief valve will blow open and will start venting air into the atmosphere.
Normally, two things might happen due to a pressure relief valve problem. Your PRV might blow before reaching the pressure cut out or it might not blow at all.
And things will get really messy if your pressure relief valve doesn’t blow. There’s no way of understanding this kind malfunction other than looking at the pressure gauge. But with a compressor PRV test, you’ll know about your valve condition.
Now we’ll go through the test method and see what to do if the PRV doesn’t bleed air. Later we’ll go through some scenarios where PRV bleeds air abnormally. And of course, we’ll give solutions to those.
Compressor Pressure Relief Valve Test
This test will tell you whether or not your pressure relief valve is in working condition.
So, let’s start with the steps-
- Fill your compressor with some air.
- Locate the pressure relief valve and its ring.
- Pull the ring carefully.
- See if you can detect air venting.
- Push the end of the pin to shut off the air flow.
If air vents out of the valve, then it's good. If not, then you should take measures.
You can also do this test with an empty tank. But this method is a bit ineffective. Here you’ll pull/push the ring too. But in this method, you have to observe whether the internal components move or not.
If not, then you know the drill.
Conduct this test a few times a month and you’ll know when to change the pressure relief valve.
The solution to Pressure Relief Valve No Blow
If your pressure relief valve fails in the test, then don’t rush into changing it.
Normally a pressure relief valve jams due to clogging and cruds.
In this case, you have to clean up the valve and see if it works.
Now, let’s go through the cleaning process-
- Make a solution with soap and water
- Rinse your PRV in this solution
- Rinse this valve with clean water
- Dry the PRV
- Lubricate it a bit
If the valve doesn’t work after the cleaning, then you’ll have to change it.
Pressure Relief Valve Blows Air
Here we’ll go through some scenarios where PRV starts blowing air. Reasons behind these scenarios are different and so are the solutions. So, let’s get going-
PRV Bleeds Air After Reaching Normal Cut
Here the pressure relief valve starts blowing air as soon as it reaches the normal cut out pressure.
This will happen if your pressure switch is damaged or is unable to work.
At this point, it’s good that your pressure relief valve is working.
But you have to keep an eye on the pressure gauge in this case. See at which pressure level the valve opens up. Our next scenarios will be based upon that.
Solution: In this case, you have to either fix the pressure switch or replace it.
PRV Bleeds Air Before Reaching Normal Cut
Sometimes, the pressure relief valve bleeds out the air before reaching the normal cut out pressure.
Check if this is the case for you. When the air starts blowing out, look at the pressure gauge. See if it’s over the cut-out pressure or not.
If yes, then this means there’s a problem with the pressure relief valve.
Now the reason behind this depends on 1 factor. Is your pressure relief valve in between two cylinders?
Depending on your answer we have different reasons.
PRV isn’t between two cylinders
So, your PRV bleeds out the air before reaching the normal cut out pressure. And it isn’t between two cylinders.
Congratulations! You probably have a loose valve. This can happen because of too much valve lubrication or because of a loose spring.
To identify spring problems, pull the PRV piston and release it. See if it retracts back to the original position. If it doesn’t then you have a PRV spring problem.
Solution: For reducing oil in the valve, you have to wash it perfectly. Follow the cleaning method described earlier here. After the cleaning, check again the pressure relief timing.
For the loose spring, clean the whole valve at first. If this doesn’t resolve this spring issue, then you have to change it.
PRV is between two cylinders
Your PRV starts bleeding air before reaching the normal cut out pressure level. And your pressure relief valve is between two cylinders.
If this is the case, then the problem’s probably in the line between two cylinders.
There’s a high chance that something’s blocking air flow between two cylinders. But still, let’s assume that it’s a PRV issue for the sake of the solution.
Solution: No worries, you have the cleaning stuff in this scenario too. Remove, clean and reinstall as stated previously.
If the problem doesn’t go away after this, then you’ve got to do some extra work.
Take a look into the pressure or intake valve on the other cylinder. Find the blockage and remove it. If you find some other kind of problem, then fix it.
Air Compressor Pressure Relief Valve Adjustment
Some air compressor PRV doesn’t activate when it’s supposed to.
For example, a 125-psi air compressor doesn’t bleed out the air even if it’s 129 psi. The PRV activates at 130 psi.
Although it’s a small blunder, still you have to keep cautious. If your luck goes south, then even this pressure will result in grave dangers.
To fix these little problems you can always adjust the PRV.
For the ease of explaining this adjustment method, let’s assume that we will work on a 125-psi air compressor. So, let’s get going-
- Disconnect the pressure switch to let air plunge in constantly
- Loosen the locking nut of the PRV
- Start rotating the hexagonal cap once the pressure reaches 125 psi
- See when the pressure releases.
- Tighten the locking nut at the pressure level you want the PRV to activate
- Check once more
That last step is super important. Most of the times valves respond at another pressure level when repeated.
Safety Measures
During the testing and fixing of pressure relief valves, you must take some safety measures.
Before the PRV test alert everyone nearby
When pulling the valve be ready for ear piercing sounds
Wear safety gloves while treating the spring; a broken spring might hurt your hands
Look out for torn wires
Keep an eye on the pressure gauge and don’t let a high pressure to build up.
While cleaning don’t use harsh acidic solutions
Follow these measures and you’ll be safe enough for the air compressor use.
Bottom Line
A small part like the pressure relief valve plays an important role in air compressor safety. It’s natural for people to be unconcerned about the pressure buildup.
Although this is the second safety measure, still this is super important. Moreover, as there’s no third safety measure, it’s important to keep the second one in perfect shape.
So. go and solve your pressure relief valve problem and start working again. Good luck.