TECH TIP: Blow off fitting. Why it’s important.
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TECH TIP: Blow off fitting. Why it’s important. You hear several people talking about blow off fittings, or pop off fitting, or even pipe away fitting. All are the same thing, and very important to a safe nitrous system. It is the small hex fitting opposite to the outlet of your NX nitrous valve. (pn 11707 for standard blow-off, 11709 NRHA blow-off, and 11712 for replacement discs.)
The Blow off fitting is a pressure release device. It is designed to rupture if the bottle is over pressurized. Over pressurization can be cause by several things. Mostly caused by over heating a bottle. This is cause by installation error with a bottle heater, sitting in direct sunlight, in the back on the car on very hot day. OR overfilling a bottle, putting 11lbs in a 10lb bottle.
The reason for the blow off is to protect any persons in the area. Once a bottle reaches 3000psi a disc will rupture, releasing all the nitrous and pressure that was in the bottle to the atmosphere. This will also be a very loud noise and definitely get your attention if you are anywhere in the area. Also freezer burn can happen if nitrous comes into contact with your skin, so do not try to stop the bottle from emptying.
Once the bottle has emptied itself, you must replace either the entire fitting, or the burst disc. (Depending on your application) NX recommends 15ft of torque when tightening the standard blow off or the NHRA Blow off fitting. Over tightening this fitting will damage the disc and may rupture at a lower PSI. Also no thread sealer is needed with this type of fitting.
Ricky
The Blow off fitting is a pressure release device. It is designed to rupture if the bottle is over pressurized. Over pressurization can be cause by several things. Mostly caused by over heating a bottle. This is cause by installation error with a bottle heater, sitting in direct sunlight, in the back on the car on very hot day. OR overfilling a bottle, putting 11lbs in a 10lb bottle.
The reason for the blow off is to protect any persons in the area. Once a bottle reaches 3000psi a disc will rupture, releasing all the nitrous and pressure that was in the bottle to the atmosphere. This will also be a very loud noise and definitely get your attention if you are anywhere in the area. Also freezer burn can happen if nitrous comes into contact with your skin, so do not try to stop the bottle from emptying.
Once the bottle has emptied itself, you must replace either the entire fitting, or the burst disc. (Depending on your application) NX recommends 15ft of torque when tightening the standard blow off or the NHRA Blow off fitting. Over tightening this fitting will damage the disc and may rupture at a lower PSI. Also no thread sealer is needed with this type of fitting.
Ricky
i look forward to the tech tip every week......thanks 
so what is the difference between the standard and the NHRA blow off disc,i would guess it just blows at a different pressure?
so what is the difference between the standard and the NHRA blow off disc,i would guess it just blows at a different pressure?
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Your welcome.
The Standard part comes with all NX bottles. It will not direct the nitrous flow outside the car. The NHRA one allows you to connect a hose or blow down tube to the blow off. This is required at all NHRA tracks. They Booth will blow at the same pressure.
Ricky
The Standard part comes with all NX bottles. It will not direct the nitrous flow outside the car. The NHRA one allows you to connect a hose or blow down tube to the blow off. This is required at all NHRA tracks. They Booth will blow at the same pressure.
Ricky
Last edited by NXRICKY; Jan 24, 2005 at 04:54 PM.
