Question About New Regulator Reading (on gauge) After Installation

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Ezana4CE

Ezana4CE

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Jan 15, 2021
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I’d like to know if I turned my reg down too low and possibly messed something up before dropping it in and gassing up my rifle. I lowered the reg setting prior to installation hoping that I could increase the reg pressure incrementally after gassing it up. I read that it’s not good to bottom out the reg before installing or after degassing and I did not continue turning the adjustment screw clockwise until it could turn not more. However, the reg reads around 25-35 bar right now. This is an externally adjustable Huma reg. 


I’m wondering if the gun needs to be fired or dry fired once to get an accurate regulator reading after installation or what. I’m not touching it until I get some feedback here. 

I asked this question in the “Tuning and Repair” forum late last night, but have yet to receive a viable response. The link below contains a photo of the manometer readings. https://www.airgunnation.com/topic/brocock-bantam-sniper-hr-regulator-repair/?referrer=1
 
Did you cock the rifle when refilling it, if not, do it now, see if the reg gauge moves. If there is air in the plenum, I think you will not do any damage to dry fire it.
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@elh0102 Sure did and filled the reservoir without issue. The reg manometer was around zero before filling. I’m just wondering why the reg pressure is so low. I thought the lowest pressure setting was supposed to be 75 bar. So I didn’t think it would register anything below 75 bar as long as the reservoir pressure is above 75 bar. 
01A5A6FA-CACD-4681-9520-7A668346ADEE.1647277959.jpeg

I also installed this screw-in device to the top of the piston. 
 
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A newly installed regulator does not need to be cycled to see its real output pressure. To a small degree, yes, but not to the extent being discussed here (seeing 25 bar, expecting at least 75 bar). So dry firing will not help even if it is safe to try.

Assuming the gauge is good, meaning the pressure is indeed 25 bar, the cause is likely one of the following:

  1. The adjuster is moved in too far. In other words, the gap in the valve seat is too close so it is taking only a small amount of pressure rise to bring it together and halt the flow of air.
  2. The Belleville spring stack is too soft. Does this regulator call for the typical nested pairs like (( )) (( ))? If so, a plain series arrangement () () () () would be too soft.
  3. A little of both. For example if the adjuster is in too far and there is a lone single washer ) (( )) (( )), it will be subject to squeezing flat well before the rest of the stack. 
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    From your description, I think #1 is the most likely culprit.

 
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@nervoustrig Thank you for the response. Considering that I want to increase the setting 100+ bar how do I do this in increments? Should I turn it a by quarter turns or half turns, then shoot? And repeat this process until the desired pressure setting is reached? Or can I adjust it simply by backing out the adjustment screw until I reach the desired pressure?
 
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I haven't used Huma's externally adjustable reg but most if not all externally adjustable regulators can be adjusted upward while under pressure. Referencing the diagram from time stamp 13:00 of the video you posted:

regulator gap.1647286209.jpg


...you'll be going from the bottom depiction to the top depiction. That is, backing the seat away from the piston, increasing the gap between them. As you go, you will immediately see the result on the gauge.

The reverse is not advisable...attempting to decrease the pressure. The piston would already be touching the seat, so moving the seat inward grinds the two of them together and risks damaging the seat material (plastic). Depressurize first if you end up needing to reduce the pressure at some point. Or just make it a policy to always evacuate the air first to be on the safe side.
 
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I haven't used Huma's externally adjustable reg but most if not all externally adjustable regulators can be adjusted upward while under pressure. Referencing the diagram from time stamp 13:00 of the video you posted:

regulator gap.1647286209.jpg


...you'll be going from the bottom depiction to the top depiction. That is, backing the seat away from the piston, increasing the gap between them. As you go, you will immediately see the result on the gauge.

The reverse it not advisable...attempting to decrease the pressure. The piston would already be touching the seat, so moving the seat inward grinds the two of them together and risks damaging the seat material (plastic).
Click to expand...



@nervoustrig Looking at illustration helps after watching videos earlier. Thanks for adding that to the thread. I think that I now have a better understanding of the interaction between the delrin seat and the reg pressure adjustment screw. I am aware that it is ok to increase this regulator’s pressure while the reservoir is pressurized. I read and was reminded against doing so in attempt to reduce reg pressure. Gun needs to be degassed for that the way I understand it. I’m just not so clear on exactly how to increase pressure besides turning the adjustment screw counter clockwise. I don’t know if this needs to be done slowly or in increments. Does the gun need to be fired or dry fired between adjustment settings when increasing pressure? Should I be taking breaks between adjustments until the desired level is reached?
 
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Does the gun need to be fired or dry fired between adjustment settings when increasing pressure?
Click to expand...

No.

You may have come across references to making small adjustments and firing when dialing the pressure down. FX is a notable example. The basic concept being limiting the extent to which the seat gets ground against the piston. By making a small adjustment and then firing, the piston is given an opportunity to back away and rediscover its happy place, so to speak. But for increasing pressure as you are doing, it is not needed.

Should I be taking breaks between adjustments until the desired level is reached?
Click to expand...

Not really. You may want to wait a short time after an adjustment to see if the pressure wants to creep up slowly before it fully stabilizes. From my perspective that is a separate concern that would need to be dealt with. And besides if this is a new regulator, the seat very likely isn't fully formed yet so it would be premature to focus in on creep.
 
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