Improving refrigerant leak design in a Core Removal Tool

[staruda6]

Hi,

I am new to the Core Remover Tool used in the refrigeration industry. I am working on the design related problem where I am seeing a leak in the shaft assembly and not in the ball valve with side port assembly. I want to know if this is a common problem or not. If yes, then can anyone please suggest better ideas to stop the leak?

Thanks,

 

[gxmplx]

Can't say it is a common problem. It happens in poorly assembled or very old/used ball valves.

The ball valve should have a cup to cover the stem and prevent leaks to the atmosphere.

The core remover tool can't fix this problem. It is only designed to change schraeder's valve core.

You should change the valve in the next possible system shut down.

 

[staruda6]

Hi gxmplx,

Thank you for your response. The ball valve certainly has a cup that cover the stem to prevent leak. But before you do that you need to pull out the shaft assembly from the ball valve when you are removing the schraeder valve and then close the ball valve. During this time, the refrigerant will leak if the seal on the shaft assembly is not good. This is where I am lacking information, to see if someone else has experienced the same problem and how did they fix it.

Thanks a lot.

 

[gxmplx]

Hmmmm…

I suspect we are not talking about the same type of valve or you want to give the core remover tool a use it is not designed for.

Bigger or smaller, the ones I work with have the schraeder valve independent from the stem assembly like here:

http://www.ra.danfoss.com/TechnicalInfo/Literature/Manuals/01/DKRCC.PI.FB0.E1.02.pdf

With this I mean you don’t front/back seat the valve stem in order to disconnect the schraeder.

The core removal tool looks like this:

http://www.grainger.com/Grainger/Valve-Core-Tool-4PDJ5?Pid=search

You are supposed to replace the cap of the schraeder with the tool, then unscrew the core, then pull the tool (with the core) back, close the valve, disassemble the back of the tool, remove the bad core, change it, reassemble the tool, open the valve and push and screw the new core in position.

I hope this is clear.

 

[staruda6]

Exactly, you are very right about the core removal tool mechanism which you have described in the grainger tool. Now, the leak I am seeing is in the back of the tool. When you are closing the valve, I am still seeing the leak in the back of the tool and not at the joint that connects back of the tool to the ball valve. The problem lies in the back of the tool which you will remove along with the schraeder valve to replace. This is where I need some information to better design to stop the leak. I am guessing the problem might be in the O rings that are present inside the tool or shaft assembly.

Any other suggestions please.

Thanks gxmplx

 

[gxmplx]

OK so the leak is the one on the tool. I couldn't get this from your first post.

Not much of a design improvement, but my first solution would be: throw the tool, buy a new one and forget the problem!

I suppose you know the ball valve must be turned exactly 90° to shut completely. If you cannot this would cause a large leak. First see if the knob is assembled correctly and note there should be a cam that stops it from turning 360°.

If the cam does not allow 90° movement you may be able to fix this polishing or even filing the cam that stops the knob from turning.

About redesigning the tool:

There is no physical way you can stop a leak that occurs between moving pieces of metal, so I wouldn't spend my time on this.

What you can do is prevent large leaks by the use of o’rings (or seals). If they are worn oil is a very good TEMPORARY seal between moving pieces of metal and a metal and the o'ring.

For purists you should use a drop of the same oil in the system.

If you really want to decrease the leak, some o’ring materials swell in contact with certain oils. So I would try with different types of oils.

If you need to change the o’rings and you read this far you may want to reconsider my second paragraph!