Rebreather World - View Single Post - Fundamentals Of Constant Mass Flow (CMF) Systems

jorgey · 7th October 2007, 00:14

Quote: (Originally Posted by DanDunfee)

=======================

Jorge

The KISS 1st stages (Apeks DS4) are typically set for a surface IP of ~ 135 psig=9.2 bar (atm)=10.2 ata.
The IP preload springs on these regulators reportedly 'bottoms out' at a maximum of about 13.5 bar=14.5 ata. 14.5 ata / 2 (for critical sonic pressure ratio) = 6.75 atm or ~68 msw. Deeper than this, the orifice begins to go sub-sonic and the flow rate begins to drop off. This, apparently, is the main basis for Jetsams recommended MOD of 75 msw. Remember that altho they are excellent rigs, the KISSes are sold primarily for recreational and shallower technical diving..... not for deep-throat technical, caving, or wrecking.

In an Rebreather World Homebuilt Rebreather Forum, I started a Thread entitled 'Max IP for DS4 ??'. You may find it interesting. It was reported in the thread that a special spring is available (NOT from Jetsam or Apeks) to provide DS4 IPs up to ~ 20 bar. I personally have no more details on the spring or sources for it, but one of the posters claims to .

Freef (Rebreather World) has posted a lot of good modelling work on this subject, altho mostly for SCRs. Below is a URL to a good, comprehensive-but-concise, Article, courtesy of Rebreathers Worldwide- Jan Jahns & JW Beck. It contains some graphics on sub-sonic CMF rolloff rates.

Gas flow through an orifice

I hope this provides the info you were seeking.

Hi Dan,
yeap, very interesting.- but of course i was not saying, that the kiss was a bad rig.- i took it only as example and because i wanted to know about the design premises of such a system.- you put it very clear, thank you.-

the graphics i told about before were the one of "gas flow through an orifice".- i will be reading the other sources, too.-

ciao
j o r g e

7th October 2007, 00:14	#9 (permalink)
jorgey New Member Current Rebreather/s: Azimuth Home Build Other Rebreather/s: Azimuth Home Build Join Date: May 2007 Location: Austria / Argentina Posts: 57	Re: Fundamentals Of Constant Mass Flow (CMF) Systems Quote: (Originally Posted by DanDunfee) ======================= Jorge The KISS 1st stages (Apeks DS4) are typically set for a surface IP of ~ 135 psig=9.2 bar (atm)=10.2 ata. The IP preload springs on these regulators reportedly 'bottoms out' at a maximum of about 13.5 bar=14.5 ata. 14.5 ata / 2 (for critical sonic pressure ratio) = 6.75 atm or ~68 msw. Deeper than this, the orifice begins to go sub-sonic and the flow rate begins to drop off. This, apparently, is the main basis for Jetsams recommended MOD of 75 msw. Remember that altho they are excellent rigs, the KISSes are sold primarily for recreational and shallower technical diving..... not for deep-throat technical, caving, or wrecking. In an Rebreather World Homebuilt Rebreather Forum, I started a Thread entitled 'Max IP for DS4 ??'. You may find it interesting. It was reported in the thread that a special spring is available (NOT from Jetsam or Apeks) to provide DS4 IPs up to ~ 20 bar. I personally have no more details on the spring or sources for it, but one of the posters claims to . Freef (Rebreather World) has posted a lot of good modelling work on this subject, altho mostly for SCRs. Below is a URL to a good, comprehensive-but-concise, Article, courtesy of Rebreathers Worldwide- Jan Jahns & JW Beck. It contains some graphics on sub-sonic CMF rolloff rates. Gas flow through an orifice I hope this provides the info you were seeking. Hi Dan, yeap, very interesting.- but of course i was not saying, that the kiss was a bad rig.- i took it only as example and because i wanted to know about the design premises of such a system.- you put it very clear, thank you.- the graphics i told about before were the one of "gas flow through an orifice".- i will be reading the other sources, too.- ciao j o r g e
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