General: Garden hose washer: hard or soft? 3

[heathenx]

I have an application that is similar to a garden hose seal (meaning that I have a round male piece and female piece that gets a seal from a rubber washer, typically found at any hardware store) except I have a bigger rubber (1.50" O.D.).

My question is a general one. In order to get the best seal should I look at a harder or softer durometer for the rubber sealing washer. I have to go with EPDM due to some chlorine use in our water systems.

I would love to upload some jpegs of my product so everyone could understand.

 

[JimCasey]

garden hose washers are pretty soft. I would guess 40 durometer or so. THe GHT connection is subject to both mechanical damage and dirt. Drop the hose-end on the driveway and it is no longer a pristine sealing surface. Since assembly of the hose and nozzle/sprinkler/sprayer/whatever is generally only "hand-tight" , a soft washer allows the user to cause the seal to conform to the sealing surface on a dented dirty hose thread, and to seal 45 psi water.

If your 1 1/2" connector will be cleaner, assembled by tools, or carrying a higher pressure, you can probably look at o-ring sealing, or using a harder gasket or one that is reinforced(die-cut from a fabric/elastomer laminate)

 

[heathenx]

thanks for the reply Jim.

 

[unclesyd]

Agree with JimCasey's about the rubber washers but I think the trend is to vinyl.

I just bought a preminum hose and it had a vinyl washer. At the same time I bought a package of these. This is the only type washer on display.

http://www.lowes.com/lowes/lkn?action=productDetail&productId=36908-306-01CWBAGF&lpage=none

 

[FACS]

It depends on the application and the seal face.

Soft rubber conforms well, but it can be undermined by high pressure.

I usually stay 60-70 Durometer for something like that.

Charlie

http://www.facsco.com

 

[heathenx]

under normal operation our pressure is below 1 psi. when we flush water thru our system then it may go up to 30-40 psi.

take a look at

http://mysite.verizon.net/mabystry/index.htm,

items 1, 6, 7.

 

[JimCasey]

Basically the purpose of a gasket is to conform to the irregularities of the two surfaces between which it seals. THe best gasket is the thinnest gasket that will conform to the irregularities.

Garden hoses use soft gaskets because the sealing surfaces are not very accurate to begin with and they take a beating. There's not much mechanical force available to crush the gaskets either, because Garden Hose fittings are hand-tightened. So with a wavy, scratched, lightly compressed surface, you use a thick, soft gasket.

If your surfaces are machined accurately and clean, a much thinner gasket will seal and it will, as pointed out in an earlier post, withstand greater pressures.

A single 0-ring set up in a groove slightly less deep than the thickness of the o-ring will seal well, and the o-ring will resist being displaced by very high pressures. Then you get into backing rings and other techniques to fight extrusion.

On your part The gasket(6) between (1) and (7) needs to be really thick and soft to provide the compression and still have enough surface loading to seal after the bayonet connections are snapped past their detent. I'm imagining something like a die-cut gasket of the neoprene foam like used in a mouse-pad. Instead, I would think about an external o-ring groove on (1) to seal on the inside of (7). Internal pressure or careful dimensioning will keep the bayoned connection from disengaging.

 

[heathenx]

thanks Jim. i was hoping the picture might help. on item (1), hard to see from the pic, i have an energy director on the outer ring that helps bite into the rubber washer. the washer that i'm currently using is .130" thick and is 50 duro epdm. i originally had these die-cut but the tolerance on the thickness was to big. i had to switch to lathe-cut parts so that i could keep a plu/minus of .005" on the thickness.

btw, we attach a standard garden hose onto the threads of item (7).

i had originally designed this with an o-ring instead of the washer but after a few concepts my ideas had changed.

i updated the picture that i put on my personal website so that you could see the thing assembled and sectioned. i colored the parts differently for clarity. if you look close you can the energy director protruding into the yellow washer. i call it an energy director because we do sonic welding on other products and i used the same geometry.

 

[JimCasey]

Nice Cad work. I see the "energy director" if that's the single raised serration. That's a good detail. If you wanted to put one in (7) it would be equally a good idea, but should probably be a different diameter than the one in (1) so they don't both squash the gasket in the same place.

 

[TomHaskins]

Forgive this humble EE's ignorance, but I have a question concerning garden hoses, washers and O-rings.

Today I purchased a package of washers for my garden hoses, and it had both rubber washers and O-rings. I've never heard of using O-rings on a common garden hose before.

For a plain garden hose with common brass couplings, does one use the O-ring in place of the washer, underneath the washer, on top of the washer or not at all? There were no directions on the package.

Forgive me if this is not the right place to ask, but I was searching the web for this info, and landed here.

 

[unclesyd]

Probably the O-rings are for a quick connect coupling. I have some from two different manufacturers and it looks like both take the same size O-ring.

For the standard screw on garden hose connection all I've ever seen is the flat washer either in rubber or vinyl sometimes with are to help trap the washer.

Normally you need to start a new thread for a different question.

 

[rorschach]

I bought a High Dollar water hose (Gilmour brand I think) a while back and in the female coupling end, it had what looked like a 200 or 300 series o-ring instead of a square section washer for the sealing seat. It works fine and the radiused surface allows for a good bit of crush without a lot of torque on the coupling nut. so yes, some manufacturers use o-rings instead of conventional washers.