Airgun Theory Regulator adjustment questions

[SILENT SQUIRREL]

Hello members.
I understand that practical air gun knowledge indicates that adjusting a regulator up can be done at any time, but adjusting one down requires degassing the gun.
Why, please?
What is the reasoning (scientific and otherwise) behind this?
Also
What happens if you lower a regulator without degassing?

Thanks
Edward

 

[Grunt64]

Hello members.
I understand that practical air gun knowledge indicates that adjusting a regulator up can be done at any time, but adjusting one down requires degassing the gun.
Why, please?
What is the reasoning (scientific and otherwise) behind this?
Also
What happens if you lower a regulator without degassing?

Thanks
Edward

When you increase the regulator pressure, you’re simply allowing more air pressure to pass through, which is straightforward and doesn’t require any special steps.

However, when you decrease the regulator pressure, the regulator needs to release the excess air pressure that is already in the system. This is why you need to degas the air gun first. Degassing ensures that the pressure inside the air cylinder is lower than the new, reduced regulator setting. If you don’t degas, the higher pressure already in the system can cause inconsistent performance or even damage the regulator. I hope this helps.

 

[SILENT SQUIRREL]

@Grunt64's reply was very helpful, most certainly.
I am wondering, however, if anyone can describe (or illustrate) how the difference in pressure damages the regulator?
And what parts get damaged?
I keep visualizing the higher pressure in the plenum being dissipated when the first shot is fired.
Yes!
I am being dense.
And need help understanding

Thanks
Edward

 

[Danman]

The mechanics of it would look something like this (think of the regulator as a mechanical one way pressure switch)... High pressure air sits in your tank, say 3000psi. Your reg is set to 1800 psi. Upping the reg to say 2000 psi just allows more HP air from tank into plenum. Now lower reg to 1600psi with plenum still pressurized @ 2000psi. The poor regulator o-ring/sealing disc (located after tank but before plenum) probably just got murdered as the plenum still has 2000 psi in it and you just asked it to only accept 1600. The 2000 psi is technically trying to get back into a 3000psi bottle, not gonna happen! If you were very fast, it is conceivable that you could fire a shot and super quickly dial reg down before plenum refills. But no one is that fast and it only works on paper...don't try this!

 

[Grunt64]

@Grunt64's reply was very helpful, most certainly.
I am wondering, however, if anyone can describe (or illustrate) how the difference in pressure damages the regulator?
And what parts get damaged?
I keep visualizing the higher pressure in the plenum being dissipated when the first shot is fired.
Yes!
I am being dense.
And need help understanding

Thanks
Edward

Not being dense, just unfamiliar and wanting to learn.

 

[Arzrover]

Not all regulators are designed to operate the same way.
In the most common design, the valve between the reservoir and plenum is held open by a strong spring... typically curved washers called Belleville washers. As pressure rises in the plenum, a piston that is coupled to the valve starts to exert pressure against the spring and when the pressure is high enough, closes the valve so no more air will flow. When you fire a shot, the pressure in the plenum drops, the piston is pushed away from the valve seal, air flows in till the pressure is high enough to close the valve again.
When you make an adjustment, you're changing the distance that the piston travels and by this, the amount of spring compression before the valve closes.
Now the valve is usually just a small hole that goes through the piston so that as the piston moves, the through hole will come into contact with a PLASTIC valve seat on increasing pressure, or away from it on decreasing pressure.
So if you want MORE pressure, you're adjusting the distance the piston travels AWAY from the seat, so it will compress the spring MORE to achieve shutoff. LESS pressure requires adjusting TOWARD the seat so the spring compresses less.
So if the system is under pressure already and you try to adjust it lower, you're actually screwing the tip of the piston into the seat... which is plastic. NOT GOOD !!
Adjusting for higher pressure means screwing it AWAY from the seat so minimal damage occurs. In practice on ones like the HUMA, adjusting it higher while under pressure frequently will eventually damage the seat enough to require flipping the seat disc over or replacing it.
Hope this helps...
Bob

 

[SILENT SQUIRREL]

Not all regulators are designed to operate the same way.
In the most common design, the valve between the reservoir and plenum is held open by a strong spring... typically curved washers called Belleville washers. As pressure rises in the plenum, a piston that is coupled to the valve starts to exert pressure against the spring and when the pressure is high enough, closes the valve so no more air will flow. When you fire a shot, the pressure in the plenum drops, the piston is pushed away from the valve seal, air flows in till the pressure is high enough to close the valve again.
When you make an adjustment, you're changing the distance that the piston travels and by this, the amount of spring compression before the valve closes.
Now the valve is usually just a small hole that goes through the piston so that as the piston moves, the through hole will come into contact with a PLASTIC valve seat on increasing pressure, or away from it on decreasing pressure.
So if you want MORE pressure, you're adjusting the distance the piston travels AWAY from the seat, so it will compress the spring MORE to achieve shutoff. LESS pressure requires adjusting TOWARD the seat so the spring compresses less.
So if the system is under pressure already and you try to adjust it lower, you're actually screwing the tip of the piston into the seat... which is plastic. NOT GOOD !!
Adjusting for higher pressure means screwing it AWAY from the seat so minimal damage occurs. In practice on ones like the HUMA, adjusting it higher while under pressure frequently will eventually damage the seat enough to require flipping the seat disc over or replacing it.
Hope this helps...
Bob

An explanation I can visualize!
Thankyou @Arzover

And thank you also to @Grunt64, and @Danman for your valiant attempts at getting this brain
of mine off auto-pilot.

Best to each of you

Edward

 

[pan60]

Not all regulators are designed to operate the same way.
In the most common design, the valve between the reservoir and plenum is held open by a strong spring... typically curved washers called Belleville washers. As pressure rises in the plenum, a piston that is coupled to the valve starts to exert pressure against the spring and when the pressure is high enough, closes the valve so no more air will flow. When you fire a shot, the pressure in the plenum drops, the piston is pushed away from the valve seal, air flows in till the pressure is high enough to close the valve again.
When you make an adjustment, you're changing the distance that the piston travels and by this, the amount of spring compression before the valve closes.
Now the valve is usually just a small hole that goes through the piston so that as the piston moves, the through hole will come into contact with a PLASTIC valve seat on increasing pressure, or away from it on decreasing pressure.
So if you want MORE pressure, you're adjusting the distance the piston travels AWAY from the seat, so it will compress the spring MORE to achieve shutoff. LESS pressure requires adjusting TOWARD the seat so the spring compresses less.
So if the system is under pressure already and you try to adjust it lower, you're actually screwing the tip of the piston into the seat... which is plastic. NOT GOOD !!
Adjusting for higher pressure means screwing it AWAY from the seat so minimal damage occurs. In practice on ones like the HUMA, adjusting it higher while under pressure frequently will eventually damage the seat enough to require flipping the seat disc over or replacing it.
Hope this helps...
Bob

so I have nothing to say.
other then yep velve seat is under pressure when decreasing and not opening and not so much when increasing.
problem solved, degass

 

[MountainSportAirguns]

Some regulators "survive" better than others. The seat is constantly under pressure and when you turn the regulator down its ball can get crushed. This is a phenomenon well known by those who tinker... especially with guns that have so many external adjustments. People buy them and in some cases immediately start twisting and turning every knob they can find until.....oh my....why is my regulator matching the bottle pressure? Lol They file a warranty claim and don't disclose the fact they turned the regulator up and down continuously without lowering the reservoir pressure or emptying it completely. Like I said, some guns survive better than others.

 

[Danman]

Some regulators "survive" better than others. The seat is constantly under pressure and when you turn the regulator down its ball can get crushed. This is a phenomenon well known by those who tinker... especially with guns that have so many external adjustments. People buy them and in some cases immediately start twisting and turning every knob they can find until.....oh my....why is my regulator matching the bottle pressure? Lol They file a warranty claim and don't disclose the fact they turned the regulator up and down continuously without lowering the reservoir pressure or emptying it completely. Like I said, some guns survive better than others.

Lol the complete opposite of me. My .22 Ghost that has been running great and came at 165bar on the reg. It shoots a little hot so I wanted to dial it down to 150...There's all kinds of great advice & how to videos on it but I so far have refused to touch that knob I always just dial H.S. wheel if needed. I've looked up the rebuild kits for the regulator but those little white disc's are often all what's needed but yeah once you tore into it might as well replace the o-rings too, they are kinda sacrificial instead of scratching up the housing they get trashed and can be replaced fairly easily. There are also some guns out there that can be dialed up/down without degassing...

 

[Grunt64]

Lol the complete opposite of me. My .22 Ghost that has been running great and came at 165bar on the reg. It shoots a little hot so I wanted to dial it down to 150...There's all kinds of great advice & how to videos on it but I so far have refused to touch that knob I always just dial H.S. wheel if needed. I've looked up the rebuild kits for the regulator but those little white disc's are often all what's needed but yeah once you tore into it might as well replace the o-rings too, they are kinda sacrificial instead of scratching up the housing they get trashed and can be replaced fairly easily. There are also some guns out there that can be dialed up/down without degassing...

Just to name 2 of them is FX impact and daystate red wolf.

 

[JungleShooter]

Just to name 2 of them is FX impact and daystate red wolf.

...And the offerings from RTI:
⁍ Priest,
⁍ Prophet, and
⁍ Mora.

Matthias

 

[Ezana4CE]

At some point in the near future it would be nice to standardize airgun regulators that can be adjusted without degassing the gun and removing them from the reservoir as well as regs that can be adjusted on the fly while under pressure.

 

[SteelFly]

Not all regulators are designed to operate the same way.
In the most common design, the valve between the reservoir and plenum is held open by a strong spring... typically curved washers called Belleville washers. As pressure rises in the plenum, a piston that is coupled to the valve starts to exert pressure against the spring and when the pressure is high enough, closes the valve so no more air will flow. When you fire a shot, the pressure in the plenum drops, the piston is pushed away from the valve seal, air flows in till the pressure is high enough to close the valve again.
When you make an adjustment, you're changing the distance that the piston travels and by this, the amount of spring compression before the valve closes.
Now the valve is usually just a small hole that goes through the piston so that as the piston moves, the through hole will come into contact with a PLASTIC valve seat on increasing pressure, or away from it on decreasing pressure.
So if you want MORE pressure, you're adjusting the distance the piston travels AWAY from the seat, so it will compress the spring MORE to achieve shutoff. LESS pressure requires adjusting TOWARD the seat so the spring compresses less.
So if the system is under pressure already and you try to adjust it lower, you're actually screwing the tip of the piston into the seat... which is plastic. NOT GOOD !!
Adjusting for higher pressure means screwing it AWAY from the seat so minimal damage occurs. In practice on ones like the HUMA, adjusting it higher while under pressure frequently will eventually damage the seat enough to require flipping the seat disc over or replacing it.
Hope this helps...
Bob

So do you ADD or SUBTRACT Belleville washers to increase PSI?

Let's say hypothetically I thought the rifle could take an additional say, 150 PSI.
How many washers would I need to add or subtract?

I do have an on/off HPA Check gauge, so I will of course ensure that I haven't surpassed the max pressure advised by the manufacturer before reinstalling the tank on the rifle.

Just not trying to take a guess, seeing as how I'm basically tinkering with a live Grenade...

Thanks.

 

[Ezana4CE]

So do you ADD or SUBTRACT Belleville washers to increase PSI?

Let's say hypothetically I thought the rifle could take an additional say, 150 PSI.
How many washers would I need to add or subtract?

I do have an on/off HPA Check gauge, so I will of course ensure that I haven't surpassed the max pressure advised by the manufacturer before reinstalling the tank on the rifle.

Just not trying to take a guess, seeing as how I'm basically tinkering with a live Grenade...

Thanks.

@SteelFly Knowing as opposed to guessing is a great approach. However, you are not tinkering with a "live grenade" by adjusting a regulator to a higher set pressure. As for your question regarding adding or subtracting bellville washers. I personally would not add or subtract the washers. I recommend sticking with the number of bellvilles that the manufactuerer recommneds.

The orientation of the washers can affect set pressure ranges as well. When I say orientation, I am speaking of how the concave /convex surfaces of the washers interact with one another in series (how they are stacked in pairs). I am not the most knowledgeable person on the topic so I will stop my explanation here and defer to more knowledgeable members who are proficient in this area.

 

[pan60]

So do you ADD or SUBTRACT Belleville washers to increase PSI?

Let's say hypothetically I thought the rifle could take an additional say, 150 PSI.
How many washers would I need to add or subtract?

I do have an on/off HPA Check gauge, so I will of course ensure that I haven't surpassed the max pressure advised by the manufacturer before reinstalling the tank on the rifle.

Just not trying to take a guess, seeing as how I'm basically tinkering with a live Grenade...

Thanks.

generally you would adjust the regulator up or down not you you need to add washers for a 150 PSI?

 

[MountainSportAirguns]

At some point in the near future it would be nice to standardize airgun regulators that can be adjusted without degassing the gun and removing them from the reservoir as well as regs that can be adjusted on the fly while under pressure.

The New Kalibergun Snipe 2 is adjusted by the regulator. It has a wide range of adjustment up and down without the need of degassing the system.

 

[SILENT SQUIRREL]

Not intending to be snarky
Just practical
Generally speaking, reading the gun or regulator manufacturer's instructions on how to adjust the regulator is the best way to start.
just my .02 scents
Edward

 

[Danman]

So do you ADD or SUBTRACT Belleville washers to increase PSI?

Let's say hypothetically I thought the rifle could take an additional say, 150 PSI.
How many washers would I need to add or subtract?

I do have an on/off HPA Check gauge, so I will of course ensure that I haven't surpassed the max pressure advised by the manufacturer before reinstalling the tank on the rifle.

Just not trying to take a guess, seeing as how I'm basically tinkering with a live Grenade...

Thanks.

As mentioned, not really a live grenade. Check this video on YT from the airgunning wizard aka @Sub 12 airgunners servicing a Huma reg and explaining things. It's using same Belville washers to demonstrate different stacking methods giving different power results.

BRK Ghost regulator service/repair​

 

[SteelFly]

In my case the stock regulator isn't intended for modding although it is possible..

It's good, I got a regulator check gauge so I'll just have to mess around with it I guess..

At least until my new regulator that is pre-set at 1,200 PSI arrives