Wednesday, 10 August 2016

Stainless Hose Clamp Failures

Hose clamps seem to be such simple things - yet choosing the wrong types can sure mess up an otherwise perfect sailing day.

As we departed from Suriname three weeks ago we found that our salt water pump was sucking some air - water was still flowing, but each time the pump started it took a few seconds to prime.  That pump feeds the deck wash system and the toilet, so it wasn't a major inconvenience.  However we then found that the water maker was also sucking air - more of a problem, because it then produced fresh water with a lot of air, and the tanks were not filling as fast (it's also not good for the RO water maker system).

We eventually found the culprits - two failed hose clamps on the salt water manifold - they had cracked right through but still looked just fine. 

Back in 2001 we had replaced all of the perforated hose clamps on board with stronger and more reliable non-perforated types. It was a real chore at the time but it proved worth while as the systems became more reliable. I remember running all over Surfers Paradise, Sydney, Darwin and even Singapore chasing up my favourite Norma brand "Torro" type hose clamps. However after more than a decade in service some of our clamps are now starting to fail, where they have been exposed to saltwater drips or spray.

Of course they are all made from 316 stainless steel, with 316 stainless screws, so what is going wrong ?

It seems that our failures are not the Norma clamps - they are other brands including ABA, that have a fairly large perforation hidden inside the clamping screw mechanism.

The Norma "Torro" clamps have a more robust screw attachment and a smaller perforation in the band. To see non-perforated hose clamps failing is unusual, specially when they made of 316 grade stainless steel, however when you look at the failure  it's predictable - they failed at the perforation hidden inside the clamp mechanism.

So, we'll keep using the Norma Torro clamps whenever possible, in the "W5" 316 stainless steel grade. They are now available with Philips "cross" drive, as an option - how many gouged and bleeding fingers would that avoid ? If you want to see basic hose clamps done properly, check this link, specially the options on the last pages. I'm quite sure that other good quality brands exist - I just haven't found them yet.


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