Quick Connect Flow Oscillations

[Bambie]

Our plant uses small diameter hoses (1"nps) with quick connect fittings to slurry water and resin mixtures. These quick connects have spring loaded, internal reverse flow stops in both the plugs and sockets to reduce spills when connecting and disconnecting. Severe flow oscillations and flow stoppage has occured when moving viscous mixtures, which is thought to be due to the 'floating' stop valves in each fitting moving back and forth causing intermittent flow restriction.

I am looking for anyone with similar experience and a solution to this problem.

 

[hydtools]

I've used quick connect fittings on hydraulic systems. Each fitting half should have a fixed feature to hold the opposing check valve open when the fittings are connected. There should be no float to close either check valve when the fittings are connected. There may be a physical problem with one or the other fitting half that causes the check valve(s) to not be held open.

Ted

 

[Bambie]

Ted,

Here is a sketch provided by our Maintenance staff. Apparently this floating stop valve is not a problem with our 'older' style of quick connects. Perhaps the spring compression was higher or there was a back stop which prevented excessive movement.

Bambie

 

[Latexman]

Water and resin mixtures slurried together, huh. How viscous is the resin? What is the resin % solids? The s.g.? Is it non-Newtonian? Is the resin soluble in water, and vice versa? Are both water and resin flowing through the same line? What exactly is happening? Do you have a PFD of what is going on?

Good luck,
Latexman

 

[Latexman]

Is this a new problem in an old operation, or undesireable behavior in a new operation?

Good luck,
Latexman

 

[hydtools]

Bambie, I do not have the latest software to open the .docx file. I can open a .doc file. Sorry.

Ted

 

[cloa]

Converted Word 2003 file to doc- I think.

 

[Bambie]

Gentlemen,

According to our old hands in Maintenance, this is definitely a "new problem in an old operation", caused by a recent switch from one quick connect Manufacturer to another.

I don't have any information on the nature of the slurries but I have attached a .doc file for viewing. The two sketches show that the stop valves are free to shunt back and forth regardless of the flow direction.

If this is a common occurrence in industry, I won’t be so quick to blame the new design.

 

[tr1ntx]

Were both sides of the quick-connect changed, or is one new and the other side old?

Where were they made? If China, or India, it could very likely be a design or manufacturing error. I've seen numerous examples of a product being sourced to China or India with engineering documentation that was not complete or 100% accurate or maybe not understood and followed exactly.

 

[hydtools]

I suspect that the slurry has a high flow loss through the couplings with enough pressure differential across the valve poppets to cause them to move and oscillate, even forced close by the flow.

A different coupling construction which has a fixed pintle to push the check valve poppets open would work. A larger coupling with less flow loss in the slurry would reduce the forces acting on the check valves.

Ted

 

[Bambie]

Trintx, Our hoses are fitted with plugs and the sockets are fitted to vessels/tanks/piping. Flow oscillations were first noticed after hose replacements with new plugs so thinking that was the cause of the problem, all sockets were replaced with no improvement.

Ted, By a "fixed pintle" do you mean a back stop for each poppet that would limit how far open they can move when engaged? This is also Maintenance's suggestion.

I have attached a .pdf of the sketches.

Bambie

 

[hydtools]

Bambie, no, I mean a feature in one coupler half that forces the opposing valve open and holds it open.

Ted

 

[Latexman]

Why not change back to the 'older' style of quick connects?

Good luck,
Latexman

 

[hydtools]

Example:

http://www.snap-titequickdisconnects.com/products/drybreak_non-spill_couplings/71_series/index.html

Check valve poppets held open mechanically.

Ted

 

[Bambie]

Ted,

Thanks for this link, I will inquire further.

Latexman,

Suffice it to say their product quality assurance program didn't meet our company's 'new' standards.