Gun Clogging with Two-Part Polyurethane

2K poly can clog guns or hoses even if it doesn't dry out. Here, pros troubleshoot a case. December 15, 2005

Question
My gun isn’t taking in fluid. I’ve cleaned out the line and filters. My pump is a Graco falcon series 699a and the gun that I am having problems with is only 3 months old. It’s a Binks aa1500 air-assisted airless spray gun with tip size 01310. I am spraying 2k poly but as of recently sprayed only Bernyl reliant with this gun.

Forum Responses
(Finishing Forum)
From contributor J:
Can you get thinner through the system? If thinner won't go through, take your gun off the hose and check to see if thinner comes out. If it does then your gun is clogged. If it doesn't, take the hose off and replace it and try again. If thinner comes out then your hose was clogged. If it doesn't your pump is clogged. Take the foot valve off and see if the lower ball check is stuck.

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From contributor S:
The problem with 2K poly is that, unlike other mixed systems (AC and the like) it cures hard even when in solution. This means that simple flushing of the line with solvent in the normal way doesn't always clean the system out and the 2K will gum up the pump. You will then have to strip the system down and soak the various parts in gun-cleaner. This process is even messier when the product is a 2K poly glue with a viscosity like set honey.