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HOW TO: Bulkhead Seals Without O-Rings

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HOW TO: Bulkhead Seals Without O-Rings

Unread postAuthor: mark.f » Wed Mar 11, 2009 4:33 pm

I had no clue as to what the title should be, so I used Velocity's term of "Bulkhead seals".

Basically, the seal is a way to make a piston valve more compact, and still accessible to service the piston. This can be seen on both the Supah and Mauler valves.

<div align="center">Image</div>

<div align="center">Image</div>

In both these designs, the builders use O-ring grooves to seal the "bulkhead" on the back of the valve in the tee, and then screws to secure it there.

I just (think) I came up with a way to do it without O-rings. Here's the steps:

1.) To do this, there has to be a "lip" in your tee. In mine, I had a piece of 2" pipe that sat halfway in the socket and was ground down to fit inside the rest of the tee.

2.) Cut a relatively thick gasket the same I.D. as the inside of the tee, and in a "washer" shape. Air has to travel through the center of the gasket.

3.) Set your tee on the ground with the port the bulkhead will be in facing up. Place the gasket on top of the "lip" in the tee, and then insert the bulkhead on top of the tee.

4.) Apply a heavy weight to the bulkhead to compress the gasket. Use a small piece of 1-1/2" pipe to direct the weight onto the bulkhead and not the tee.

5.) Drill your holes to be tapped for machine screws. I used eight holes evenly spaced around my tee. These holes should obviously go through the tee and the plug.

6.) Tap these holes to the machine thread size you are using.

7.) Wrap your machine screws right under the head with a few wraps of teflon tape. Thread them into the holes in the valve. Tighten in a "lug nut" fashion to ensure even distribution of force.

8.) Remove the weight, and there you have it.



I haven't tested this as of yet (as far as leaking goes), but this is going to be part of my piston valve I'm building, and I did get it done. Take a look at the pictures below. I'm probably still gonna rebuild this valve, though, because I want to use O-rings on the back plug anyways.
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Attachments
100_0115.JPG
Bulkhead seal.
100_0117.JPG
Gasket.
100_0118.JPG
&quot;Lip&quot;.
100_0116.JPG
View inside tee.
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Unread postAuthor: King_TaTer » Wed Mar 11, 2009 5:33 pm

Very cool man, nice of someone to do this.

I've just recently seen the pictures of the supah valve insides. This looks very similar minus the o-rings and lathe work.

Again nice How to, it's very easy to follow.
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Unread postAuthor: Gippeto » Wed Mar 11, 2009 6:28 pm

Adding my .02

Nice idea Mark. :)

1/4 x 20tpi machine screws are plenty strong if you're using 6 or more. Each will handle (in shear) 200 pounds of force or more.(depending on grade)

The holes for the screws should be at least 1.5 times the screw diameter from the edges to help avoid tear out type failure.
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Unread postAuthor: mark.f » Wed Mar 11, 2009 8:41 pm

Thanks, TaTer.

Gipetto, I just checked the screws and they are just shy of 3/8" from the edge of the tee. Good thing I'm building another one...

<teacher>I hope the rest of you were paying attention to Gipetto!</teacher>

We'll see when I pressurize it whether it will leak, or worse, whether the gasket will extrude itself from between the two surfaces (but that's unlikely).

EDIT: edited for clarity.
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Unread postAuthor: Hubb » Thu Mar 12, 2009 7:31 am

I, too, think this is a swell idea. I wish I'd have thought of this when I built my piston. It would have made it a whole lot easier.
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Unread postAuthor: mark.f » Thu Mar 12, 2009 11:32 am

I recall a few people asking how to do something similar a while back, but as I hadn't tried it at least marginally, I didn't pipe up.

I think I did include this mechanism in my imitation supah design.
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Unread postAuthor: SEAKING9006 » Thu Mar 12, 2009 11:38 am

Is there even a spot to attach a pilot on that valve or is it simply a demo?
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Unread postAuthor: mark.f » Thu Mar 12, 2009 11:58 am

Well to attach a pilot you'd drill a 7/16" hole in the center of the cap and tap it to 1/4" NPT threads. I just didn't do it yet because this piston valve isn't nearly completed. It might not even be completed, because I know a few things I want to do different.
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