Chainsaw duckbill valve

billr

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#1
Well, this is a desperate shot-in-the-dark! I'm looking for duckbill valves to use as a "foot valve" for chemical metering pumps. I have done a lot of searching online and duckbills seem to be common in only four variants:
1) large, like 1-1/2" and up into many feet in diameter
2) very small, 1/8" and smaller
3) breastpumps, no idea of size but material is not likely to be OK for the sulfuric-acid and sodium-hydroxide these pumps will handle (no, not the same pump!)
4) chainsaw, used for venting the fuel tank? I'm thinking these might be about the right size (3/8-1/2" diameter) and available in Viton.

So, is anybody familiar with the duckbills used in chainsaws or other small motors? I need to get an idea of sizes and what specific application (saw/engine model) I might look for.

Again, looking for about 3/8-1/2" diameter, Viton or better, and just the bare "duckbill" would be OK. I could fab any necessary housings, but sure can't justify the cost of a custom-molded duckbill.
 

nickb2

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#4
BTW, I have no idea what a "foot valve" is and I googled that, nothing came back that made sense to me. Plz instruct, I will check with my local guy, Lots of chain saws being chucked out since last storm.

So maybe informing me on what is a foot valve for this application will help to more understand your request. ;)
 

billr

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#7
Thanks for taking an interest in my weird problem!

No, a metal ball (even 316SS) might not hold up to the chemicals well. Ball-type for this use often have ceramic balls, and can even be had with plastic springs. However, I haven't found any of quite the right size/cost/availability in the ball style. the duckbill seems ideal, since it is tolerant to crud, seals quite tight, has low cracking pressure, and should be a low-cost simple molded part.

Yes, a duckbill operates on much the same principle as a reed-valve.

The ISM parts are a bit too small, and I don't think silicone would hold up. Likewise, you may find hits on duckbills made of Santoprene, but I think that is a uerethane and also not suitable for these chemicals.

The Poulan parts look to be right, but I need to know sizes. I'll assume they are fuel-proof, so probably Viton or nearly as good. Obviously, there are many small-engine manufacturers (Homelite, Mac, Ryobi, etc.) that have similar parts; I just need to get a feel on dimensions.

I should add; I am in a genteel urban area, I only know of one local small-engine shop and they are kind of a-holes. I need to go in with an exact P/N or equipment model to get much help. JackC, I'm talking about Joseph's in PH; do you know of any other local places? The one over by Concord Costco is "nicer", but less involved with parts.
 

billr

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#8
Oh, I forgot to explain what a "foot valve" is. It is simply a check-valve placed at the lowest point of the suction line, down in the fluid to be pumped. It helps keep the suction hose filled to retain the pump prime, and keeps the hose from peeing all over when it is removed from the fluid to change out empty fluid containers.
 

billr

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#9
I have a handle on some ball-type ones in the 1/4-3/8 size ($30 each...) and have ordered them for one app. But, I think these will be too small for the bigger pumps, so I am still searching. I would sure like to find a $5 duckbill and make the housings as a one-time cost. Only the duckbill will wear/deteriorate.
 

nickb2

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#10
Would this work? You wrote,
The Poulan parts look to be right, but I need to know sizes.
I'll assume they are fuel-proof,

This fits the "cough, pun" bill.

It says to not use 10% ethanol gas though. I don't know if that would be a problem down in calif, I don't think you guys use pure gas like us.(if pure means anything anymore)

I see them going for 3-5$ around up here. So here is another link, may open up your search options. https://www.stenscanada.ca/610-345-duck-bill-valve
 

nickb2

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#12
The 3$ one comes from MD? Maryland I think. So shipping will be an issue. But with the part# maybe a holes on genteel street could hook you up. o_O

You could buy a bunch of those and use them for testing to see if the membrane holds to the chemical. BTW, I don't think you mentioned which sorts of chemicals the reed/duckbill valve will need to hold to.

I think I am understanding the concept of what you are trying to achieve. So trying both a ball type and a duckbill similar type will probably yeild expected but as you say, it depends on how the check ball will withstand.

The 30$ ones you mentioned, are they ceramic? Cuz if they are, that is a steal. ;) Cuz I saw a few links to those @ 315$ for a 2 pack, but maybe we are not talking about the same type. https://www.waters.com/1/1/17560-700002333-check-valve-ceramic-1-75-2-pkg.html
 
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billr

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#14
The Stens/Homelite ones are probably too small for the bigger pumps, but I will probably get some to try on the small pumps in place of the $30 ball-checks. Those are plastic bodies with ceramic balls and 316 SS springs. I think they (the ball springs) will hold up OK to the chemicals used there, but may gum up as the chemicals are rather viscous. I may even try those duckbills with several in parallel, they are cheap enough. One of those links you posted states dimensions for the Stens, first time I have seen dimensions and that is what I am needing. Thanks.

The bigger pumps (six of them) run some fairly tame chemicals but a couple are for 50% sulfuric acid and %50 sodium hydroxide. I am trying to find a material that will hold up to both, so that there is no need to have different parts or fret about if they are used in the correct application. For the rigid parts, plain PVC is fine. For elastomers, Kalrez seems best, but very expensive and not commonly available. Viton is next best, good for one (can't remember if it is base or acid) and OK for the other.

Here in Calif, I think we have had E10 from when it first came out, many years now and I have had no troubles with it.

I peeked again at the Stens. It is only .100" ID, still maybe good enough for the small pumps; but I really need to find one with an ID of about 1/2".