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Old 08-01-2015, 05:36 AM   #1
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Double clamping of hoses

Just going through all the inlet/discharge hoses on our new to us boat and wondering what is the normal practice for double clamping ie two hose clamps rather than the normal one. - just those below the waterline? all inlets - is there a rule of thumb.

BTW, I intend using 316 Norma clamps - good enough - or is there a better option?

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George
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Old 08-01-2015, 05:58 AM   #2
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Just my preference I love theses and have conferdence with using just one



And despise theses the only time I have had a clamp let go was with one of these .

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Old 08-01-2015, 06:43 AM   #3
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General practice is double for fittings below the waterline and single above. Buy the non perforated kind and make sure that the screw is stainless steel like these AWABs: Defender.com Search Results: awab hose clamp


Don't put a double hose clamp on unless the barb is long enough. If too short double clamping can make it worse and pull the hose off.


FWIW ABYC does not specify double clamping, but every surveyor will write you up with singles.


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Old 08-01-2015, 07:03 AM   #4
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The double clamping of hose fittings came about when a proper barbed hose fitting was not as common and a short smooth pipe nipple would be used..

Still useful on smooth connections.

For a better tightening than with a screw slot , this works well with the screw driver part removed.

http://www.homedepot.com/p/Commercia...1122/204404819

$5, -$10 almost every where.
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Old 08-01-2015, 07:17 AM   #5
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I think FF hits it....except my Awab clamps have heads that are smaller than my 6 in 1 screwdriver. Other clamps though seem to fit nicely.

Double clamping is a legend that seems to be less intelligent the longer I am around boats and in the boating industry.

I would love to read an intensive study on it like so many other topics we read about.

I can't think of a radiator hose that is double clamped yet we double hose clamps virtually under no pressure?

OK, vibration then..we'll if the hose is stout and properly supported....why then do I pull a muscle when trying to wrench the hose off even AFTER I have loosed ed the clamps.

While cheap insurance to double clamp many of the below the waterline hoses...I am only half convinced it is remotely necessary for safety, not convinced at all because some surveyor thinks it is.
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Old 08-01-2015, 07:27 AM   #6
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Mainsail to the rescue... again:
Proper Installation of Double Hose Clamps Photo Gallery by Compass Marine How To at pbase.com
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Old 08-01-2015, 07:34 AM   #7
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Not sure it will show up when pulled up by anyone else...but in the link...

Leo (the first comment) and I agree...failures are becoming more rare, if proper install are done 2 clamps are overkill, etc...

Good explanation of proper double clamping...wonder if he has made a short study like other topics if doubles are always needed?
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Old 08-01-2015, 08:24 AM   #8
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Bare in mind that not all nipples are long enough to accept two hoes clamps. And in fact double clamping a short nibble can lead to premature failure of the hose.
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Old 08-01-2015, 08:41 AM   #9
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Quote:
Originally Posted by Capt.Bill11 View Post
Bare in mind that not all nipples are long enough to accept two hoes clamps. And in fact double clamping a short nibble can lead to premature failure of the hose.
Guess the million dollar question is....go back and replace all those short nipple and double clamp? Or live with the short nipple, single clamp with quality and argue with the double clamp following?
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Old 08-01-2015, 08:43 AM   #10
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I have had clamps fail so doubling is insurance. The spring type constant tension clamps seem good for larger applications.
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Old 08-01-2015, 08:53 AM   #11
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I have had plenty of clamps fail..heck have even forgotten to tighten my fair share...the funny thing is that I don't think I ever had more than a drip.

Regular barbs in pretty good shape with decent hose or hose that has set on a barb is a pretty solid setup except under really high pressure.

But that is only my experience and I guess if I had a bad or several failures I would be more convinced of double clamping.

I do it...but more to satisfy others than me....

I still would love to read the explanations from those responsible for me double clamping whether going back and replacing short barbs is necessary or whether they agree better to only use one clamp and live with it.

I wonder if they also are so anal about fresh and salt water pressure systems above the waterline.

Had an expensive T-bolt clamp on a CAT 3196 fail on the maiden voyage off Savannah. It was on the cooling system...engine damaged bad enough we had to return it to the factory for a new engine. You never know.
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Old 08-01-2015, 08:57 AM   #12
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I prefer using a T hex nut driver instead of a screwdriver. The AWABs are metric, 7mm IIRC. Something like this, very handy:



AWAB makes a flexible one, but I've never seen one first hand.

And if for some reason you can't reach it with that due to space, a GearWrench stubby is another wonderful tool.
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Old 08-01-2015, 09:01 AM   #13
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So, some clarification. ABYC DOES specify double clamping, but only on exhaust and fuel fill lines. ISO does specify double clamping below waterline. Just for the record
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Old 08-01-2015, 09:13 AM   #14
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I am finishing the replacement of all below-the-waterline through hulls and seacocks and also will be replacing the B-T-WL hoses and clamps. I like Awabs, but not the cost, and believe that one per fitting is probably sufficient.

So I'm thinking of ordering one Awab per fitting and reinstalling one of the old perforated clamps as a "dummy" second . . . assuming the fitting is big enough for two. The second one will add some level of redundancy--better than I have now---and should satisfy any insurance surveyor, all for half the cost of what I thought I was going to spend.

Anybody know a good source for Awabs in bulk? Or good deals on trident hose?

[URL=http://s167.photobucket.com/user/angus99_bucket/media/image.jpg1_zpsv09ote6f.jpg.html][/URL
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Old 08-01-2015, 09:18 AM   #15
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Quote:
Originally Posted by gaston View Post
Just my preference I love theses and have conferdence with using just one

You have to be careful with those as it is very easy to overtighten them. Best (and should be) used on engine-related fittings with a torque wrench.
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Old 08-01-2015, 09:26 AM   #16
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Quote:
Originally Posted by Sealife View Post
So, some clarification. ABYC DOES specify double clamping, but only on exhaust and fuel fill lines. ISO does specify double clamping below waterline. Just for the record
Thanks. It looks like we may have an insurance survey coming up and the question always comes up.
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Old 08-01-2015, 10:47 AM   #17
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Especially w smaller hoses overtightening is probably common. Not so much to a straight pipe. Small multiple barb fittings may not need any clamp at all depending on how tight a fit it is. If you can barely get the hose on it probably isn't coming off unless internal pressure is considerable.

In the first pic below the fitting in the lower left is w single clamp as the fitting was short. I love these clamps. Get them (not cheap) from a local shop and other than that don't know the source. The size is rather critical unlike the automotive type. I've only purchased small ones for my fuel fittings.

With the automotive type clamps I suspect a better seal can be attained by staggering the screws 180 degrees when two clamps are used. I suspect the hose gets somewhat "puckered" opening the door to possible leakage through the "pucker". Does anybody also suspect this or know anything about it?
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Old 08-01-2015, 11:12 AM   #18
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Eric, those clamps look galvanized.. what are they made of? Do they completely encircle the hose or just a "U"... hard to tell. As for the 180 degree thing on common hose clamps, it matters most (but not very much) when using the crappy perforated clamps so you have a smooth surface in contact with the hose it's entire circumference. With something like the AWABs which are smooth all around the inside, it really doesn't.
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Old 08-01-2015, 11:31 AM   #19
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Quote:
Originally Posted by angus99 View Post
I am finishing the replacement of all below-the-waterline through hulls and seacocks and also will be replacing the B-T-WL hoses and clamps. I like Awabs, but not the cost, and believe that one per fitting is probably sufficient.

So I'm thinking of ordering one Awab per fitting and reinstalling one of the old perforated clamps as a "dummy" second . . . assuming the fitting is big enough for two. The second one will add some level of redundancy--better than I have now---and should satisfy any insurance surveyor, all for half the cost of what I thought I was going to spend.

Anybody know a good source for Awabs in bulk? Or good deals on trident hose?
Defender sells awab clamps for 3 or 4 dollars each for for a 2 inch clamp. Are you really saving enough money to justify using inferior clamps in a critical application?

I have seen pretty good deals at my local West Marine with hose remnants. If you are lucky, they will have the length you need left over.
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Old 08-01-2015, 11:36 AM   #20
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But that may be arguable....is it a critical application on all hoses? And even the....what is the incident rate for single versus double clamped hoses?

For some...even a few dollars spent elswhere can mean a lot....especially if it doesn't significantly chsnge things.
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