IDA-72 CL questions

divingtoors

HI There

I have begun with the modification of my IDA-72 to a MCCR (thats the main idea at this point in time)I am currently examining all the parts and routing of all the components, trying to make some sense of it all, and with Dave Sutton's great web page and Bob Bollards mod. have an idea of how I should go to work...

Looking at the Counterlung I noticed some interresting points.
Maybe I don't completely understand the working, and would appreciate any help in clarifying the workings for me.

The exhaust sits in the middel of the CL right at the divers back.
It is a simple one way rubber flapper valve construction, the same as a flapper valve on a breathing hose.
I presume this was to easily vent the great volume of gas that would be injected via the umbilical to the diver (in normal operation).

This brings a few questions to my mind.
1) How do you do a positive pressure check on the unit? With the exhaust valve construction, it is impossible because on the surface, the slightest pressure causes the valve to dump.

2) Should a diver turn on his back (facing up) during the dive, all the gas in the CL will escape at a rate of knots via the exhaust, as there is no "back pressure" or mechanical means of stopping the exhaust flow. The exhaust valve will be in the highest position, and position of greatest pressure differential. This would mean that if a diver turned on his back during a dive, the diver is risking of a major flood, once the CL is completely emptied..For a diver doing a backward rol of the boat, this could be a major concern as there will be an immediate loss of CL gas and volume, and could lead to a dangerous situation.

Is there any remedy to this situation or am I not fully understanding the workings of the machine, and the Russians had already figured out the problem.

Regards

Johan

__________________
"The closer you are to danger, the further you are from harm" - Pippin Took (Hobbit)

"Trust the advise of a man that does not fully trust his own, as the man that fully trusts his own, only knows one side of the problem…" - CJ Langenhoven (Translated)

kiwi_diver

I suspect that the original users of the 72 maintained an upright position for the most part as the rig is for deep water salvage or construction etc. When we were going through my freinds 72 and 64 tool kits, we found a cap that looked like it screwed over a counterlung OPV but it did not seem to fit any of the OPV's on the 72, 64 or my AKA-60. Perhaps there is a cap that fits and can be used for +ve checks.

You might be better off discarding the original OPV and fitting an after-market one off an SMB etc. Most of the 72 conversions seem to involve scrapping the majority of the original soviet parts!

Cheers.

__________________
Ray.
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Latitude 36 South, where the deeper you dive, the warmer it gets!
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divingtoors

HI


Yes, I think the divers that dived the unit never did backward roll entries, as the IDA-72 is umbilical fed from a diving bell, so it would be almost immpossible, looking at the size of the umbilical.
They were probably also trained never to turn on their backs while diving, which could be a difficult thing doing commercial work.

There must also be a part to close off the OPV to do +ve tests, that somehow got left behind in the "Motherland". Unfortunately I do not even know where to try and obtain an operators manual for the IDA-72

I think a retrofit with a old BCD OPV will solve the problem, and if I really want to "go to town" I thought of maybe using a old drysuit OPV. Then I will have an adjustable OPV...

I will have to dive the unit as soon as my modification has been completed, and actually test the OPV, as I have not seen the unit working.

Regards

__________________
"The closer you are to danger, the further you are from harm" - Pippin Took (Hobbit)

"Trust the advise of a man that does not fully trust his own, as the man that fully trusts his own, only knows one side of the problem…" - CJ Langenhoven (Translated)

osiris

Is your OPV complete? If it's like mine and just a mushroom valve then it's not complete, so I will need to replace mine. The complete IDA72 OPV should operate in any orientation without releasing gas unless the internpressure exceeds outside (just like any other OPV). Maybe post a picture of yours.... ?

divingtoors

HI There

I have attached some pics of my IDA-72's OPV.

It is still installed, as I want to get as much info on it as I can, before I really start digging and removing things.

It seems that the last silver ring, is glued to the CL fabric, and the locating rings screw onto this last ring.

It consists of two parts, an outside "cowling" and the body with the mushroom valve, seen in beige.

I do not understand why there would be such an elaborate and effective OPV in the IDA-71 and then something as simple as this in the IDA-72. This just confirms my suspicion that the unit was mostly used in OC mode, enabling low WOB and easy flushing of the exhaled gas.
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Attached Images

	OPV.JPG (135.1 KB, 45 views)
	OPV Close-up.JPG (126.1 KB, 45 views)
	OPV Close-up II.JPG (105.3 KB, 45 views)

__________________
"The closer you are to danger, the further you are from harm" - Pippin Took (Hobbit)

"Trust the advise of a man that does not fully trust his own, as the man that fully trusts his own, only knows one side of the problem…" - CJ Langenhoven (Translated)

kiwi_diver

I doubt that the ring is really glued, most likely it is just stuck due to having been pressed against the fabric by the backnut for so long. Since the 72 is an SCR, the OPV will be more inclined to operate than one on a 71 or other CCR. You will have to replace it, or modify it for CCR mode or it will simply vent your loop at an "other than optimum" rate.

Interested to see where you end up going with this as Dave (osiris) has a 72 project on the boil also.

__________________
Ray.
==
Latitude 36 South, where the deeper you dive, the warmer it gets!
==