Tuesday, August 7, 2007

Pump Plumbing as of 8/6/07

In earlier posts both Jim and I have written that there were issues with the green vinyl suction plumbing that had been used to plumb the pump's valves. The plumbing worked just fine. The problem was that it was near impossible to install, and impossible to remove in order to maintain the check valves. The green hose was just too tight and inflexible for the fittings we have been using. We tried black poly pipe too, which was easier to install, but required additional fittings and hoses, because it was so rigid. This increased parts counts and costs. It was no easier to remove than the green vinyl.

Finally, we hit on ordinary automotive type rubber heater hose. It's flexible enough to install and remove easily, readily available, and cheap enough. The only problem is that it collapses under vacuum. This little conundrum was solved by making a coil out of galvanized 14 ga steel wire. Almost any wire of sufficient stiffness will do, even if it wants to rust. A wire coat hanger would work. The coil was made by winding the wire around a 3/4 inch steel rod. Again, what one uses for a mandrel is not critical. As long as the result fits inside the heater hose fairly closely, and prevents it from collapsing under the vacuum produced by operating the pump, it's all good. Only the hoses on the vacuum side of the pump need to have a coil installed.

We tested our cheap and dirty vacuum hose arrangement on 08/06/07. It works. We'll be posting the results of the testing later, probably with more videos. We're still looking for a cheaper substitute for the pretty stainless steel hose clamps we've been using to secure the hoses. They're kind of expensive. There are a number of possibilities, and as soon as we know what we're going to do, we'll post it here.

2 comments:

Daniel said...

Thanks for posting your progress on this blog. I've found it to be very interesting. I'll ask a few of my friends about a stainless hose clamp alternative.

Are there any other technical/design issues you are having with the pump? I know a few people who may be able to give good advice.

Smitty said...

as I type this reply, I'm waiting to hear that the pump has arrived in Haiti. As soon as I hear, I'll post that it's there. When some testing is done, I'm pretty sure there will be problems to solve, and design changes to be made. Your offer of help is appreciated. As we run into problems, I'll publish what they are, and solicit help. If you find a solution to the hose clamp problem, you can rech me here.