Hey guys, a couple of weeks ago I posted questions regarding using regulated HPA with a QB. I have built the gun and have an issue that I would like to explore.
I am using a 13ci 3000psi tank with a 1400psi output JDS regulator. Attached to the regulator is a Rap4 on/off valve to use between the tank and gun. The Rap4 has a gauge and a burst disk. The burst disk in the Rap4 is of unknown value as it is unmarked. Seeing that the regulator output is 1400psi I removed the factory burst disk from the Rap4 on/off and installed a 1800psi burst disk as an extra safety margin. I filled the tank to 3000psi, checked for any leaks, and set the tank assembly aside as I was working on another project. About a half hour or so later the 1800psi burst disk let go. Scared the hell out of me! I am glad that the tank was not installed on the QB.
Now, am I nuts in assuming that the 1800psi burst disk should not have blown as it is only exposed to the regulator output of 1400psi? I am wondering if I had a bad burst disk or did the output of the regulator spike way above 1400psi? I replaced the blown burst disk with a 3000psi disk and did some testing. I capped the tank assembly so no air could escape and opened the on/off valve. The gauge on the on/off reads 1400 and quickly climbs to slightly over 1500psi and then stops. I don't know if the pressure stops climbing or if the gauge won't read any higher. Wish I had a gauge that would read higher to test with.
What do you guys think of this?

Tom



"What, me worry?"

that regulator needs some attention as it is "creeping". The basic way regulators work is that spring tension is applied to a piston with a seal on the end of it, the air adds to that tension. The difference between the spring tension and the air tension is the regulated output.

What is happening with your 13ci bottle is that the little sea that is suppose to shut off the air is leaking. Slow leak, so the pressure creeps up over time. given enough time, and the out put would equal whatever the pressure inside the bottle (3K if it's filled to that level).

Basically, you need to either send that reg. in for a rebuild, or if it is one that can be self-serviced, will need to replace that little piston.

(it's also why i'll store the HPA guns with the RAP4 on/off on "off".)


From an old post:

Here it is set up on one of the HPA conversions:
[IMG][/IMG]

Pressure is a safety concern.

Inside your reg . is a piston. That piston turns the air on and off by way of a little seal in its back end. Regulation can be controlled by washers or a coil spring, but if that little seal doesnt seal, the pressure will creep up.

(In simple terms, a regulator works by spring pressure that is not enough to seal that little piston. Needs a bit more pressure to seal. The amount (pressure) of air needed to make that little piston seal is the output pressure.)

Have had one regulator do this, slowly creeping up from its 1100psi setting. Inside of 10 min., it was at 1300psi. In another 15 min, had crept up to 1500psi. If I didn't have the on/off gauge to show me, or if I had put the gun away in storage, would sooner or later creep up to whatever the pressure was in the tank (3,000psi).

The burst disk should have blown before anything really nasty happened. Key word here is "should".

You could figure out a case of creep with a chronograph. If the gun shoots faster the longer you wait between shots, its creeping and the bottle needs to be taken out of service for repair.

I appreciate someone confirming what I suspected. This is a brand new regulator so I had best send it back to John for recalibration or repair. Guess my "being paranoid" paid off.
I am glad the disk blew before I installed the tank assembly on my gun! I haven't even shot it yet due to this issue.
And yes, I store my guns with the on/off in the off position also.
Robert, do you know if the Rap4 gauge will read above 1500psi?

Tom



"What, me worry?"

..but have been slowly replacing the fill nipples on the HPA tank with Bob Long filtered fill nipples. Just one more filter in the system, which can't hurt.

Hi Tom,

What is the pressure rating on the regulator's burst disk?
There should be one on the bottle side and on the reg side. I've played with so many of these
and have never had it happen. I've had some that creep a bit.... would gain 50-100 psi then stop.
Most of mine have been Expert HPA but I have also picked up a few off of Ebay.

Did it go with a pop or a hiss ?

Jay

http://qbmags.com

Answering your question, the regulator is as I received it from John with a 5K on the tank side and a 3K on the regulated side. They are physically located on the regulator. The 1.8K that blew (no hiss, just "bang") is on the downstream side of the 1.4K regulated output and is installed in the on/off valve, NOT in the regulator. The picture Robert posted above is the same setup I have. You can see the on/off added to the tank/reg assembly but you can't see the burst disk that is located in the on/off valve on the side opposite the gauge. My opinion is that the 1.8K should not have blown if only exposed to a 1.4K regulated output. Correct?
I emailed John at JDS and he will swap out the regulator, no problem. I told him I want to buy another 1.8K burst disk and he told me it will just blow again and that I should buy a 3K disk! If this is the case, why in the hell did I buy a regulator to achieve a 1.4K output to my gun? As you can probably tell, I am getting very frustrated with this situation. Again, am I nuts or what? Maybe I'm not clearly explaining the setup I have?

Edit:  I added a picture of my tank setup.  You can see the burst disk in the on/off valve.  This is where I have the 1.8K installed.

Tom



"What, me worry?"

Hi Tom,

Just looking at some of the regs I have laying around.

2000 PSI output (Expert HPA) 3k burst downstream
1200 PSI Output (Expert HPA) 1.8k Burst downstream
850 PSI output ( Ebay ) 1k burst downstream

FYI on some of the 850 psi ebay regs I have increased the output to around 1000-1100 psi on several but have never blown the 1k burst disks.
Some of these have sat under reg pressure for years.

Send Matt at expert HPA an email and ask him what burst disk is on his 1400 psi regs for a second opinion. He may also be able to shed some light
on how they are sized.

Jay

http://qbmags.com

Jay, where can I get 1K burst disks from?

Cheers
Simon

Hi Simon,

Not sure where to get them. Mine came with the 850 PSI regs.
Mat at Expert HPA may know.

Jay

http://qbmags.com

many thanks Jay, I'll try that.

Cheers
Simon