alternative to clamping for flow restriction
alternative to clamping for flow restriction
(OP)
I have an application where a sping loaded clamp is used to shut off flow through 1/4" PVC tubing. The problem is that this clamp is in the clamped position for prolonged time and the tubing eventually deforms and retains the crimped shape affecting the flow characteristics when unclamped.
Can anyone offer alternatives to clamping? I've considered a small manually actuated valve but have had no luck in finding reasonably costing alternatives.
Any help is greatly appreciated.
Can anyone offer alternatives to clamping? I've considered a small manually actuated valve but have had no luck in finding reasonably costing alternatives.
Any help is greatly appreciated.





RE: alternative to clamping for flow restriction
What is the process fluid that is flowing through the tubing?
How good of a control do you need?
What industry is this in?
"Do not worry about your problems with mathematics, I assure you mine are far greater."
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RE: alternative to clamping for flow restriction
RE: alternative to clamping for flow restriction
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RE: alternative to clamping for flow restriction
RE: alternative to clamping for flow restriction
1) Bigger hose. This way, even when distorted by the clamping, it will still give sufficient flow - assuming the distortion does not progressively get worse.
2) IV tubeing with lock, the type that hospitals use. Not sure if those things come in 1/4".
3) A valve - you can try to attach it to something solid so that when you turn it, it doesn't move.
"Do not worry about your problems with mathematics, I assure you mine are far greater."
Albert Einstein
Have you read FAQ731-376 to make the best use of Eng-Tips Forums?
RE: alternative to clamping for flow restriction
The clamping mechanism now is a pivoting, spring loaded finger-pull type clamp. I want to stay away from turning type valves. I thought there may be a supplier of small in-line pinch valves that somehow contributed to reshaping the tube into circular form when released. Hard to explain, but easy (for me) to envision what I'm looking for.
Again, this is 10-100 thousands quantity. I'm looking for a solution that only costs in the 10s of cents. You know every penny counts.
Thanks again for the suggestions.
RE: alternative to clamping for flow restriction
Cheers
Greg Locock
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RE: alternative to clamping for flow restriction
Griffy
RE: alternative to clamping for flow restriction
You need to switch to a rubber (elastomer) material, more like EPDM, Santoprene, or even plain old surgical tubing. Any of these materials will give you many thousands, probably 100's of thousands of cycles, before fatigue cracks start showing up and the hose starts leaking. Medical types have switched to the PVC tube, because it is easier to get the material past regulators (fewer additives used in their manufacture) and also the tubes hold up better to sterilization. But the majority of med devices are used for at most a few dozen cycles, then disposed of.
If you really must have the PVC tube (perhaps for the transparency of the tube?), then do as Greg suggests (create a mechanical means to reshape the tube with each cycle), or wrap the o.d. of the PVC tube with a section of rubber tubing, and use a clamp that fits the new larger o.d. The rubber tubing will "bounce back" better after pinching, and hopefully keep squeezing the PVC back into shape for enough cycles to suit you. The PVC will only be obscured over a short area within the pinch clamp.
RE: alternative to clamping for flow restriction
The method of use for this particular product is such that the hose remains pinched for all but maybe 10 minutes per month. Not quite the ideal situation for any thermoplastics.
The issue is not exactly cycles. More an issue of deformation set.
Thanks for all the suggestions.
RE: alternative to clamping for flow restriction
RE: alternative to clamping for flow restriction
Or,
The "bite valve" common on runner/biker/hiker hydration packs.
Or,
Push-pull valve typical of water bottles and dish soap.
Or,
Twist valve as on a bottle of Elmer's Glue or mustard.
Or,
The flip the little spout 90 degrees valve that used to be common on shampoo bottles.
When you need cheap, look too mass-market consumer goods. Go visit the supermarket for further inspiration.