Cracking pressure?

[Hemlon]

I just got my regs back from annual servicing. The tech included a paper with the servicing specs.

One of the details listed is cracking pressure. What is this?

What are the parameters for normal?

 

[Charlie99]

Cracking pressure is simply the pressure it takes to get the regulator to start delivering air to you. In the USA it is usually specified in inches of H2O.

It is more or less how far down you have to submerge the faceplate/diaphram of the reg (with mouthpiece up and no water in reg) in order to get it to freeflow. The tech will have adjusted it to whatever the spec is for your reg ..... others can jump in with the typical range, but IIRC it will be around 1/2" for a very low setting, or up around 1" as a more normal setting for your primary. If your reg has a cracking pressure adjustment, you might even have two numbers on the sheet, such as 0.75" when set to easiest, and 1.25" when set to highers. An octo will be set to a bit higher to make freeflow less likely.

If you specify what type of 2nd stage you have, others on Scubaboard could tell you the recommended manufacturer setting.

 

[Hemlon]

Thank you so much, Charlie!

 

[Jim Lapenta]

It's the pressure required to depress the demand lever and allow air to flow into the second stage, basically. It is measured with a magnahelic in inches of water. The lighter the cracking pressure the easier the second stage is to get to start to allow air to flow. What is normal depends on the reg.

 

[Hemlon]

Got it. Thanks, Jim.

 

[Couv]

Hi Hemlon,

Just a matter of curiosity. The cracking pressure, intermediate, etc are some of the parameters a repair facility would mention on the spec sheet. If you don't mind, I would be interested to know: What make/model regulator (first and second stage) you have, the IP and cracking pressure and any other parameters listed before and after service.....thank you.

Couv