pressure tests

tiggerbiker · 31st October 2007, 09:42

i have searched the forums and i can see lots of posts referring to positive/negative pressure tests, but.

how long would you expect your unit to hold the pressure/vacuum? - are we talking minutes or hours??

(i would ask my instructor but he's in the red sea until next week)

mik · 31st October 2007, 09:58

40 mins, p20 in the manual.

Dive safe

tiggerbiker · 31st October 2007, 10:05

Quote: (Originally Posted by mik)

40 mins, p20 in the manual.

Dive safe

- oops, thats embarrassing. i have read the manual 2-3 times but dont remember reading that bit.

i'm reading that manual again - then again

**PhilSiswick** · 31st October 2007, 10:43

Quote: (Originally Posted by tiggerbiker)

- oops, thats embarrassing. i have read the manual 2-3 times but dont remember reading that bit.

i'm reading that manual again - then again

You wouldn't be alone in missing key elements - it's not the best written manual from that point of view. Not knocking the content - it's mainly there, but the format.

Good luck,

Simon A · 31st October 2007, 12:06

The manual states 40 min but in my opinion that's excessive.
I started out with a homebuild and I now dive a Classic. From that experience I have developed the following procedure:-
Suck the unit down to negative pressure, then go and have a cup of tea. If after the cup of tea it's still holding negative pressure then it's passed.
Set OPV to "predive" and inflate until the OPV vents, go and have another cup of tea. If after you've finished the cup of tea, gas vents when you turn the OPV to "dive" consider the positive pressure check passed.

HTH
Simon A

**PhilSiswick** · 31st October 2007, 13:12

Quote: (Originally Posted by Simon A)

The manual states 40 min but in my opinion that's excessive.
I started out with a homebuild and I now dive a Classic. From that experience I have developed the following procedure:-
Suck the unit down to negative pressure, then go and have a cup of tea. If after the cup of tea it's still holding negative pressure then it's passed.
Set OPV to "predive" and inflate until the OPV vents, go and have another cup of tea. If after you've finished the cup of tea, gas vents when you turn the OPV to "dive" consider the positive pressure check passed.

HTH
Simon A

That's in line with what I've read on here and been taught. The only problem with the procedure is the impact of the two cups of tea on the bladder during the subsequent dive ;-)

Cheers,

tiggerbiker · 31st October 2007, 13:24

thanks for the advice,
i rang APD and they stated that the units are tested to hold +pressure for 8hrs and hold -ve for at least 2hrs but wouldnt say what would be acceptable for a used unit?

my unit holds for over 30mins in +ve pressure and holds for just over 15mins in -ve pressure.

it would appear that i dont have much to worry about!

tiggerbiker · 31st October 2007, 20:17

just got home and read through my manuals and sure enough, all the info is there

TDI inspo. manual page 40,
+ve = 1/2 hour is a pass but several hours should be expected.

-ve, hoses should remain collapsed for 5 to 10 mins.

APD manual, page 13 (in mine). lungs should remain firm for 40mins.

it doesnt specify a time for the negative test.

ajmtucke · 1st November 2007, 11:48

Quote: (Originally Posted by tiggerbiker)

my unit holds for over 30mins in +ve pressure and holds for just over 15mins in -ve pressure.

thank goodness for that, you had me worried for a minute then !!

when you getting wet ??

ash

tiggerbiker · 1st November 2007, 12:40

Quote: (Originally Posted by ajmtucke)

thank goodness for that, you had me worried for a minute then !!

when you getting wet ??

ash

hi Ash,
my mod 1 starts 12th november
12 days or 288hrs or 17280 mins. i'm not obsessed - honest

31st October 2007, 09:42	#1 (permalink)
tiggerbiker New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2007 Location: herts, uk Posts: 55	pressure tests i have searched the forums and i can see lots of posts referring to positive/negative pressure tests, but. how long would you expect your unit to hold the pressure/vacuum? - are we talking minutes or hours?? (i would ask my instructor but he's in the red sea until next week)
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31st October 2007, 09:58	#2 (permalink)
mik New Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Join Date: Sep 2006 Location: Sydney North Posts: 75	Re: pressure tests 40 mins, p20 in the manual. Dive safe __________________ It just fell apart in my hands, Chief!
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31st October 2007, 10:05	#3 (permalink)
tiggerbiker New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2007 Location: herts, uk Posts: 55	Re: pressure tests Quote: (Originally Posted by mik) 40 mins, p20 in the manual. Dive safe - oops, thats embarrassing. i have read the manual 2-3 times but dont remember reading that bit. i'm reading that manual again - then again
(Offline)

31st October 2007, 10:43	#4 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,099	Re: pressure tests Quote: (Originally Posted by tiggerbiker) - oops, thats embarrassing. i have read the manual 2-3 times but dont remember reading that bit. i'm reading that manual again - then again You wouldn't be alone in missing key elements - it's not the best written manual from that point of view. Not knocking the content - it's mainly there, but the format. Good luck, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
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31st October 2007, 12:06	#5 (permalink)
Simon A Escapee from DIY Rebreather's Current Rebreather/s: Inspiration Classic Other Rebreather/s: Not Bought Yet Join Date: Feb 2005 Location: Reading, UK Posts: 346	Re: pressure tests The manual states 40 min but in my opinion that's excessive. I started out with a homebuild and I now dive a Classic. From that experience I have developed the following procedure:- Suck the unit down to negative pressure, then go and have a cup of tea. If after the cup of tea it's still holding negative pressure then it's passed. Set OPV to "predive" and inflate until the OPV vents, go and have another cup of tea. If after you've finished the cup of tea, gas vents when you turn the OPV to "dive" consider the positive pressure check passed. HTH Simon A
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31st October 2007, 13:12	#6 (permalink)
PhilSiswick Phil Siswick, Tango Current Rebreather/s: Evolution Other Rebreather/s: Inspiration Vision Join Date: Apr 2006 Location: Oxford, UK Posts: 1,099	Re: pressure tests Quote: (Originally Posted by Simon A) The manual states 40 min but in my opinion that's excessive. I started out with a homebuild and I now dive a Classic. From that experience I have developed the following procedure:- Suck the unit down to negative pressure, then go and have a cup of tea. If after the cup of tea it's still holding negative pressure then it's passed. Set OPV to "predive" and inflate until the OPV vents, go and have another cup of tea. If after you've finished the cup of tea, gas vents when you turn the OPV to "dive" consider the positive pressure check passed. HTH Simon A That's in line with what I've read on here and been taught. The only problem with the procedure is the impact of the two cups of tea on the bladder during the subsequent dive ;-) Cheers, __________________ Phil (WSKD 0001) I have always felt that the dive I am on is not nearly important as the dives I plan to be on the rest of my life. Tom Rose, 2007 The person who gets the farthest is generally the one who is willing to do and dare. The sure thing boat never gets far from shore. Charles A. Lindbergh www.hugsac.org.uk
(Offline)

31st October 2007, 13:24	#7 (permalink)
tiggerbiker New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2007 Location: herts, uk Posts: 55	Re: pressure tests thanks for the advice, i rang APD and they stated that the units are tested to hold +pressure for 8hrs and hold -ve for at least 2hrs but wouldnt say what would be acceptable for a used unit? my unit holds for over 30mins in +ve pressure and holds for just over 15mins in -ve pressure. it would appear that i dont have much to worry about!
(Offline)

31st October 2007, 20:17	#8 (permalink)
tiggerbiker New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2007 Location: herts, uk Posts: 55	Re: pressure tests just got home and read through my manuals and sure enough, all the info is there TDI inspo. manual page 40, +ve = 1/2 hour is a pass but several hours should be expected. -ve, hoses should remain collapsed for 5 to 10 mins. APD manual, page 13 (in mine). lungs should remain firm for 40mins. it doesnt specify a time for the negative test.
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1st November 2007, 11:48	#9 (permalink)
ajmtucke RBW Member Current Rebreather/s: Inspiration Vision Other Rebreather/s: Inspiration Classic Join Date: Nov 2005 Location: Hereford, UK Posts: 86	Re: pressure tests Quote: (Originally Posted by tiggerbiker) my unit holds for over 30mins in +ve pressure and holds for just over 15mins in -ve pressure. thank goodness for that, you had me worried for a minute then !! when you getting wet ?? ash
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1st November 2007, 12:40	#10 (permalink)
tiggerbiker New Member Current Rebreather/s: Inspiration Classic Other Rebreather/s: Join Date: Apr 2007 Location: herts, uk Posts: 55	Re: pressure tests Quote: (Originally Posted by ajmtucke) thank goodness for that, you had me worried for a minute then !! when you getting wet ?? ash hi Ash, my mod 1 starts 12th november 12 days or 288hrs or 17280 mins. i'm not obsessed - honest
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