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Old 18 January 2018, 05:44   #1
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Pressure Relief Valves, what do you think?

I am considering putting some pressure relief valves (PRV) to my RIB, why? Well it is stored outside so I am a bit twitchy about the tubes, which hold air remarkably well for a boat of it's vintage, over-expanding following being topped up after extended periods in the cold north sea.

Good idea or just something else to go wrong?

What are your experiences, I would like to have some thoughts before the Stanley knife comes out!

Thanks

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Old 18 January 2018, 05:57   #2
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they are a good thing if you have them, i dont currently have them on my sib i just keep my pressure down a bit to allow for expansion. in hot weather i nip down and let a bit out and leave the dust caps off which is the secondary seal never had a problem.
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Old 18 January 2018, 06:04   #3
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Leaving the dust caps off, now there's a thought!
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Old 18 January 2018, 06:14   #4
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Not sure why leaving the caps off would help, anyway when you leave your rib, just let a little air out to allow for temperature fluctuations - unless you turn up on a hot day you will be getting your pump out anyway. Save your money gets my vote.
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Old 18 January 2018, 09:20   #5
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Leaving the dust caps off, now there's a thought!
In my expeariance especially as the valves get older and bits of dirt can get on the valve seal they weep a bit the dust caps can be cleaned easily so the o ring seal is very air tight and the secondary seal hand books state to keep the dust caps on for air tightness. I keep my boat covered so no debris get in to an open valve
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Old 18 January 2018, 10:41   #6
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Funny that ,quite often when i have seen ribs for sale ,i have seen written ..."Tubes hold air perfectly ,never had to put any in since i have owned it "
made me always think ,manufacturers apply a mid pressure at a mid temperature so damage could be avoided either way ,.........i have a hypalon rib in my garden bought from a very profesional uk rib tender manufacturer summer last year ,i noticed tube pressures were firm when i got it and seem acceptable even in current winter weather so assumed this was "way to go"
anyway those valves let it out but they hav,nt worked a way of putting it back in yet , whats the point i reckon the worst case scenario is towing a deflated rib down the road ,seems to allow exageration of weight on seam and fixing bonds
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Old 18 January 2018, 10:43   #7
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I am considering putting some pressure relief valves (PRV) to my RIB, why? Well it is stored outside so I am a bit twitchy about the tubes, which hold air remarkably well for a boat of it's vintage, over-expanding following being topped up after extended periods in the cold north sea.
Thanks

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Your Up Norf!, The air and the sea are just as cold
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Old 18 January 2018, 11:02   #8
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If you can afford it and the Boat is worth it...Why wouldn't you have them?..might be a better question
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Old 18 January 2018, 11:53   #9
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If you can afford it and the Boat is worth it...Why wouldn't you have them?..might be a better question
^^^^this

Had rib with and without them, I think I've put the pump on my ribcraft maybe 5x since I bought it as the auto valves let out in hot weather and when winter ones round it needs topped off again. Without them I just let air out a little before leaving it and never had a problem.
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Old 18 January 2018, 12:16   #10
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OPVs will save your tube in the event of a collision.

Collision can lead to a pressure spike in excess of 13 psi which can lead to a severe blowout.

Not to mention, they're a reliable way to inflate your boat with no gauge. Simply fill until the OPVs pop off.
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Old 18 January 2018, 12:54   #11
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OPVs will save your tube in the event of a collision.



Collision can lead to a pressure spike in excess of 13 psi which can lead to a severe blowout.



Not to mention, they're a reliable way to inflate your boat with no gauge. Simply fill until the OPVs pop off.


To raise the pressure in the tube from the normal 2.5psi to 13psi would require the tube being compressed to around a 1/4 of its original size. In that sort of collision, tube damage would be the least of my worries
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Old 18 January 2018, 12:58   #12
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To raise the pressure in the tube from the normal 2.5psi to 13psi would require the tube being compressed to around a 1/4 of its original size. In that sort of collision, tube damage would be the least of my worries
I've fixed it many times.

Last one I did, sailing dinghy turned in to the coach boat with both vessels at speed. Collision ruptured the perpendicular seam under where the tube connections is adhered to the GRP of the hull (Searider 5.4). Repair required to make an incision below a towing eye in order to repair the seam internally.

It's not as much dynamic stress as one would think to achieve that.

I'd only worry about it with CSM/NEO though, welded PVC can sustain a ridiculous overpressure.

I destroyed an early 90s Zodiac Futura Junior in December by inflating it to a crazy pressure...something like 700 or 800 mbar (~11 psi). We threw it around trying to get it to blow. We had to knife it to kill it. Not bad for 25 year old welded PVC.
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Old 18 January 2018, 13:25   #13
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Quote:
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^^^^this

Had rib with and without them, I think I've put the pump on my ribcraft maybe 5x since I bought it as the auto valves let out in hot weather and when winter ones round it needs topped off again. Without them I just let air out a little before leaving it and never had a problem.
So I take it you removed them from your own Ribcraft then
Some people don't mind pumping the Bilge by hand...or re-charging the Batteries with long leads from inside the Consul...
I have two Auto Bilges....and Remote charging Dock on the Dash..All makes life just a little easier
...I remember you had yours on a mooring for sometime?...
Don't tell me..you rushed down by car ...jumped in the Tender just to let the air out in Hot weather
They CAN also on occasion help considerably!... and may save a costly repair! if some Arse Numpty on a Jet Ski (or anything else) bashes into at 10knots while your stood still too
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Old 18 January 2018, 13:34   #14
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if some Arse Numpty on a Jet Ski (or anything else) bashes into at 10knots while your stood still too
Erm... How fast do you think they let the air out?! (and yes, I have them too)
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Old 18 January 2018, 14:03   #15
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Erm... How fast do you think they let the air out?! (and yes, I have them too)
What would you like Nos a scientific formula??
All the same let's see if I can help....Back to the real world of experience!!
..On a very HOT day in Lyme Bay fishing in my (Black) Rib I saw two Jet ski's approaching ...one of whom had the audacity to to hit the Boat in the Bow..Portside Join...
I heard one of the front Port Vaulves Expel Air!
When I'd cooled down and checked for damage, thankfully I found there was none.. now,who's to say if the Pressure relief vaulves saved the seam..But I AM sure they DID NOT add to the problem..and May well have helped by releasing the pressure of impact!

It was soon apparent the Jet Skiers were Both Pissed as the proverbial Farts!....It also became Very apparent VERY quickly (to them)that I was not giving or selling them ANY of my spare fuel!!
I hope this helps.
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Old 18 January 2018, 15:09   #16
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Erm... How fast do you think they let the air out?! (and yes, I have them too)
It'd take a high speed camera to capture it. It's a fairly weak spring, so as soon as the pressure wave hit the valve, the valve would pop open.

Flow rate:
http://www.leafieldmarine.co.uk/Port...-flow-rate.pdf
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Old 18 January 2018, 17:01   #17
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It'd take a high speed camera to capture it. It's a fairly weak spring, so as soon as the pressure wave hit the valve, the valve would pop open.

Flow rate:
http://www.leafieldmarine.co.uk/Port...-flow-rate.pdf
In other words, bugger all

Can't argue that they're not a good idea, because they are. But to think they'll make a difference during the split second when there's an impact you'd probably have to be a bit overconfident in your own logic.
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Old 18 January 2018, 17:34   #18
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In other words, bugger all



Can't argue that they're not a good idea, because they are. But to think they'll make a difference during the split second when there's an impact you'd probably have to be a bit overconfident in your own logic.


Hey Nos! Donít let practicality get in the way of a good theory
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Old 18 January 2018, 18:19   #19
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Hey Nos! Don’t let practicality get in the way of a good theory
Im wondering which "Pikey Rule" may applie here....???
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Old 18 January 2018, 18:33   #20
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Im wondering which "Pikey Rule" may applie here....???
Quote:
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Back to the real world of experience!!
Let it not be said you talk a load of #2....
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