Pressure relief Valve.

[mike os]

That looks very much more engineered than the ones I have.
I like that

It’s norgren… it’s what they do

 

[Aston66]

That looks very much more engineered than the ones I have.
I like that

I bet that's costs more than my compressor cost me though.

 

[mike os]

I bet that's costs more than my compressor cost me though.

I’d be surprised …

 

[addjunkie]

Its a 90 ltr , 3 HP, 9 FAD, compressor. I find that at 125 PSI , the differential in pressure is to wide and lose pressure quickly. I found I could get a more constant 100- 90 psi having a higher cut in point.
I like to pump it up to 145psi, and let it cool for a bit, it seems to leave most of the water in the tank that way. I do this when I'm using a spray gun or home made grit blaster.
I know it uses more energy and , places strain on pump and motor etc, but I only use it occasionally.
I hear differing points of view on this subject, What is you thinking.

My thinking is simple. The 9cfm of Free air delivery isnt enough for what your trying to achieve. Use less air, or buy a bigger compressor.
Relying on condensate dropout due time in the tank will end badly. You need alternate means to remove moisture.

 

[Aston66]

Thanks for your advice. It makes sense.
I can't run a bigger compressor at home, and can't afford one anyway.
I do have a half inch bsp filter/ regulator which also removes quite a bit of moisture after the tank.
I also use a small water trap behind spray gun.
I know I sound arrogant, but I think I can run this one at 145 PSI when I need too for blasting motorcycle brake calipers and occasionally using my Lidle impact gun.
I just don't want to blow my shed up.

 

[Aston66]

I know? Not just 1 but two. Here's a photo of one of them.
I can't see all three of my pressure gages being wrong?
But as you say I don't like taking to many risks with compressed air cylinders.
I'll have ago at tweaking it in very small incruments and see how it goes.
Thanks for your advice
View attachment 345823

I stripped a few of these valves down today, to have a look. I can tighten the cap that retains the springs, I found a pair of circlip pliers that fit well. Now I'm wondering whether , they are set by different rated springs, or wether it's just a matter of the spring being loaded by screwing the cap in.
I've got four different valves including the original rated at 10 bar. I have just nipped them all up with hardly any pressure on the springs. I thing I will fit them all , and try to tighten them till the stop bowing off at around 10.5 bar.

 

[addjunkie]

10 bar is max working pressure for a small compressor….on a good day with the wind behind you when everything is new and valves unworn.

good luck!

 

[Aston66]

Thanks , I see what you mean.

 

[Moose McAlpine]

I know I sound arrogant, but I think I can run this one at 145 PSI when I need too for blasting motorcycle brake calipers and occasionally using my Lidle impact gun.

Most air tools are only meant to run at 90psi, and airflow volume is more important than pressure. Too high a pressure can damage the air motors.

 

[Aston66]

I only have a supermarket impact wrench. I Have only needed to use it once for a clutch center nut on my bike. I just run it unregulated straight from the tank at 145, psi, cause I use it rarely, (I prefer a breaker bar where I can use one) I don't mind if the ' cheap impact gun only lasts a few years.
I use two regs with the spray gun though. One at the tank and one before the Gun, I use 1/2" bsp fittings, and a 13mm hose 10 ft long.
I'm happy with what it does, but really need to sort out these PRVs and the Pressure switch. I can't find another the same specs and quality as the one Wolf fitted originally.
Without spending more than the compressor is worth.

 

[Moose McAlpine]

A couple on eBay:

Pressure Relief Valves 1/4" & 3/8" BSPP | eBay

Find many great new & used options and get the best deals for Pressure Relief Valves 1/4" & 3/8" BSPP at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

Pardon our interruption...

 

[Aston66]

A couple on eBay:

Pressure Relief Valves 1/4" & 3/8" BSPP | eBay

Find many great new & used options and get the best deals for Pressure Relief Valves 1/4" & 3/8" BSPP at the best online prices at eBay! Free delivery for many products.

www.ebay.co.uk

Pardon our interruption...

Those are the ones I need for peace of mind. Thanks . I'm thinking I only paid £90.00 for my compressor though ! I've already had to fit new mains and a con rod to the pump and spending any more on it at this point is not economical . I may just have to concede, and get my bank card out.

 

[Aston66]

10 bar is max working pressure for a small compressor….on a good day with the wind behind you when everything is new and valves unworn.

good luck!

Just been thinking about this! Correct me if I'm wrong but if the receiver is Pressure tested to 15 Bar? Then it shouldn't split or fragment till at least 35 Bar?

 

[Aston66]

My thinking is simple. The 9cfm of Free air delivery isnt enough for what your trying to achieve. Use less air, or buy a bigger compressor.
Relying on condensate dropout due time in the tank will end badly. You need alternate means to remove moisture.

plus who would run their Hobby compressor over what the safe working pressure on the tank indicates? Any way in the event of failure, it would likely be a ' Pin Hole' in the receiver due to internal corrosion.
They don't just ' blow up as in all these YouTube videos.
I ll take my chances

 

[Aston66]

I just want a PRV that releases at 10.5 to 11 bar and a decent switch that can be adjusted to 10 bar and still be reliable.
Most of the ebay ones aren't' I would advise people to stay away .
My recent experience with 11 Bar PRVs has left me ' flummoxed!
Three gages cannot be that out of sync?
Yet, I will go out and buy a glycerine filled quality gage , cause I don't won't to have an unexpected pressure release .

 

[Aston66]

So' to recap. I have this week purchased two 11 bar PRVs , they cost twice the price of other generic PRVs but not the most expensive.
They both blow off before 9 .Bar
Is there something I'm over looking?.
I'm no expert , not an engineer etc' I trust the supplier, just can't understand what's going on? Can pressure gages go that wrong? It's a big differential between 8.5 - to 11 Bar?
Please Help.

 

[DanZac]

Just been thinking about this! Correct me if I'm wrong but if the receiver is Pressure tested to 15 Bar? Then it shouldn't split or fragment till at least 35 Bar?

When new, with no internal corrosion, no fatigue from a million pressurisation cycles and no dents etc, it will have been safe at 15 bar if that's what the plate says. 30 years later having been sat half full of water and gunk it's anyone's guess. It may only have a fraction of the material thickness left at the bottom.

Any way in the event of failure, it would likely be a ' Pin Hole' in the receiver due to internal corrosion.

If your lucky, if not its goodnight Vienna!

So' to recap. I have this week purchased two 11 bar PRVs , they cost twice the price of other generic PRVs but not the most expensive.
They both blow off before 9 .Bar
Is there something I'm over looking?.
I'm no expert , not an engineer etc' I trust the supplier, just can't understand what's going on? Can pressure gages go that wrong? It's a big differential between 8.5 - to 11 Bar?

I tested hundreds of PRVs of various types in a previous job and whilst they were often a bit off, especially when old, they were generally fairly accurate. Where are you measuring your pressure from, and where is your PRV situated? On the tank or on a feed/ take off line?

Are you sure it's the PRV letting go that's stopping you reaching the pressure you want and not the compressor failing to reach it or something else letting go. I've seen compressors with multiple PRVs.

As @addjunkie said earlier if your compressors old and knackered it may not ever get to its original design pressure, let alone more.

If your finding numerous PRVs are all low then I'd suspect your gauges, or where your actually measuring your pressures from to be the issue. Get yourself a bucket pump and test them against a known good gauge.

 

[carbon]

I know it uses more energy and , places strain on pump and motor etc, but I only use it occasionally.

I have seen electric motors that were overloaded fail in under six hours due to the increased operating temperature/current. Without checking the motor current when the compressor is close to max pressure. I always check current load on motors rather than rely on pressure gauges for operating pressures

 

[Ross365]

Without wishing to be all H&S I'd suggest that before you start adjusting them, it's worth getting a certificated pressure relief valve (there's a big difference between "yes we've tested it" and an actual certificate), or test your gauge against a known good (calibrated) one to ensure it is correct.

The last thing you want is an air receiver failing.

Some years ago I bought a good quality pressure gauge from the Budenburg company and kept that aside from general use so that it became my test standard for anything else I bought with a pressure rating. It did costs few quid, but I like having it to hand. Periodically, I used to send it off for calibration, but haven't kept that up.

 

[addjunkie]

Just been thinking about this! Correct me if I'm wrong but if the receiver is Pressure tested to 15 Bar? Then it shouldn't split or fragment till at least 35 Bar?

Well…..depending how scientific you want to get. If the max allowable working pressure is 10 bar, this is set by the PRV. At the manufacture stage a hydro test would be done to 150% of MAWP.
Not sure about your over pressure figure of 35 bar or where your getting this figure from. Im quite wary of over pressure having spent over 40 years working in high risk environments with high pressure gas often in excess of 400 bar.
Hydrotesting is used because it is much safer in the event of failure, as water doesnt expand rapidly when the vessel fails. On the other hand air is a gas if it fails because you over pressure it, for example screwing down safety valves, then yes bits might fly about, as the air when released will expand very rapidly. In effect you may have a metal ballon going pop.
But as your compressor is a cheapo oriental jobbie I suspect something else will fail before the reciever!