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Hose Clamps


A very important but often overlooked piece of equipment on your boat.


Jack and Alex Wilken The ubiquitous hose clamp (HC),


always present in your boat, perhaps hidden away under a sink or bunk. Just how much attention does it get or deserve? We depend on it to keep water out of our boats and at the same time make sure hoses stay connected so water can travel through them. We’ll cover four aspects of the hose clamp in this article: 1. Material, 2. Design, 3. How to use or install the clamp in different boat applications, and 4. Being prepared when suddenly a clamp or hose needs immediate attention.


MATERIAL: When it comes to material, there is only one acceptable choice: stainless steel (SS). However, as stainless comes in many different types, which one is best for boats? A great many manufactures simply state ‘300 series’ and quote SAE standards. It is important to remember that SAE stands for ‘Society of Automotive Engineers’. If that does not sound very marine or boat oriented, it isn’t! These standards are important, for example, for thread sizes, but as far as materials, the two environments- automotive & marine are very different and require different materials. ‘300 series’ could be 316, but it usually is not. If it is 316, the one most appropriate for boats, the manufacturer


will be quick to print it clearly. When we asked one manufacturer, who supplies large quantities of HCs to marine distributors, what ‘300 series’ meant, they said, “somewhere between 304 and 305”, adding that their biggest customer was the plumbing industry for house and commercial building. In general, stainless steel should be avoided for underwater uses, but hose clamps, even though they are mostly out of the water, are often submitted to wet and dry conditions so the grade of SS becomes quite important. What this means in the real world is that you could expect the 316 to last much longer and therefore require less maintenance. (Another thing to watch for in a HC is that all the parts are SS. Sometimes, the screw will be ferrous and that is a no, no for sure.) The difference between 300 series and 316 is $1.04 to $3.21 in HC size #10. So, you have just mounted your new bilge pump costing $84, and you must now decide if you are willing to pay about $4 more for peace-of- mind.


Cross section showing correct hose and clamp placement


Hose Barb hose clamp #1 hose clamp #2 Hose


DESIGN: There are three basic types: 1. Most common is where the screw


is used as a worm gear (only this kind is shown in photos), having a band width of 3/8” to 1/2”, 2. Then, comes the T-Bolt clamp, and 3. The Bolt and Trunnion (B & T) which looks similar to the T-Bolt. These are 5/8” to 1” plus in width.


Not all worm gear types are alike,


the three main differences being 1. The mounting for the screw, 2. Whether the threads (Figure 1)


are cut through the band (perforated) or embossed on the band, and 3. The pitch or angle of the screw. The mounting of the screw is either


mechanical, meaning the metal is bent so it captures the band, or welded. Welding is cheaper but can increase vulnerability to corrosion in that local area, so the mechanical connection is usually better. Perforated bands can damage the hose and weaken it. Embossing costs more. The flatter the pitch of the screw, the more pressure you can generate on the clamp with the same force and the less likely it is that the clamp will loosen with time and vibration. The T- Bolt and the B & T type are usually specified for hoses


hose clamp #1


Hose Barb hose clamp #2


Hose


Figure 1 48° NORTH, MARCH 2011 PAGE 44


Figure 2 Figure 2


Figure 3


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