Expanding Foam Gun Repair

[Onoff]

This based on @Radian's comments what a pita these are to repair. Just done another one and thought it might help someone:

 

First thing to take off is the brass nozzle. Some are a hex and others have two flats. Then clean all the gunk off with a blade. Use a small drill bit, held in your hand, to clean up inside. It's fitted with some type of liquid threadlock but I just replace later with ptfe tape:

 

 

 

Then unscrew the knob at the back, take that and the spring out and with a pair of moles clamp around the barrel and unscrew that. Again it'll have threadlock, again use ptfe tape upon reassembly:

 

 

Barrel off, you can see the pink foam adhered to the long rod that goes up the middle. Gun cleaner for that if still wet, sharp blade if it's dry. Then move to the small nut just in front of the handle:

 

 

You should be able to knock the rod out with a soft faced mallet. Blast through the handle with gun cleaner as you go:

 

 

Clean the barrel. I used a suitable drill bit (in the cordless if necessary) then a cloth soaked in gun cleaner and drag it back and forth. Blast any remaining loose stuff through:

 

 

Imo then wear inside this nylon bush (just below the threaded section) is what kills a lot of these guns. Foam ends up coming out the back, dries and the gun seizes. And/or air gets in through the same point when the gun is closed off and hardens what's in the barrel. You will likely need to pick out the dried foam inside the nylon carefully:

 

 

My trick is to slip on a suitable rubber O ring:

 

 

PTFE tape the barrel where it goes into the gun:

 

 

Tape the brass nozzle too:

 

 

Reassemble with a smear of silicone grease on the moving parts:

 

 

Hopefully you're then good to go. Not shown where the can screws onto the gun. You'll likely need to cut/dig foam off around there and have a twiddle up where the ball valve is.

 

I've seen other guns where the central rod is (black), Teflon covered like on a frying pan, that wears leading to the same issues. An O ring might well fix that.

Edited April 13, 2022 by Onoff

[MikeGrahamT21]

The bit where the can attaches, use a socket to remove the top bit, this holds the ball valve. Once that bit is off, you can then use an allen key to remove the brass part from this section, and the ball and the spring will come out. This is often so clogged up it ends up looking like solid plastic!

[Radian]

1 minute ago, MikeGrahamT21 said:

The bit where the can attaches, use a socket to remove the top bit, this holds the ball valve. Once that bit is off, you can then use an allen key to remove the brass part from this section, and the ball and the spring will come out. This is often so clogged up it ends up looking like solid plastic!

 

Yes, the valve is often another part that needs cleaning. Is it just there to seal the foam inside the gun when you change cans?

 

Good write-up @Onoff

[Onoff]

14 minutes ago, MikeGrahamT21 said:

The bit where the can attaches, use a socket to remove the top bit, this holds the ball valve. Once that bit is off, you can then use an allen key to remove the brass part from this section, and the ball and the spring will come out. This is often so clogged up it ends up looking like solid plastic!

 

I didn't go "there" as mine didn't need it but will do so with another dead gun I've been given.

[SteamyTea]

Or just stick it in a buck of CH₂CL₂ for ten minutes.  How we cleaned the PU moulding machines.

 

Edited April 13, 2022 by SteamyTea

[Miek]

29 minutes ago, SteamyTea said:

Or just stick it in a buck of CH₂CL₂ for ten minutes.  How we cleaned the PU moulding machines.

 

Will this dissolve hardened foam? 

[SteamyTea]

Just now, Miek said:

Will this dissolve hardened foam? 

Yes.  And your nail varnish.

It can also decaffeinate your coffee.

No sure how easy it is to buy small quantities, we used to get 200 litres at a time.

[Miek]

Usefull to know. I have 5l of acetone which I use on the wet foam for cleaning but it won't touch hardened foam.

[markc]

Hmmm, wonder if  trichloroethylene will work? Might have to try it.

[ToughButterCup]

Could have done with this thread years and years ago; about the time I managed burst,  slip on and sit in a can's worth of expanding foam - while it was still expanding.

In public, I have never taken my trousers off faster. Nor more visibly. Nor while on top of a scaffolding. Right on the road side.

 

"Mummy, why has that man thrown his trousers off the scaffolding?"

"Why is he hopping around, and shaking his head ?"

 

 

 

[SteamyTea]

1 hour ago, Miek said:

5l of acetone

I really don't know why acetone is sold as gun cleaner. It is really pretty poor at it. Works well with polyester resins, and some epoxies, when uncured, but little else.

 

 

[Onoff]

14 minutes ago, SteamyTea said:

I really don't know why acetone is sold as gun cleaner. It is really pretty poor at it. Works well with polyester resins, and some epoxies, when uncured, but little else.

 

 

 

I was glad it was only acetone one time I squirted it in my eye.

[SteamyTea]

1 minute ago, Onoff said:

 

I was glad it was only acetone one time I squirted it in my eye.

If you could see how much damage acetone can do to a body, you may have wished it was something else.

But like all chlorine and oxygen based chemicals, they are fine in moderation.

[MikeGrahamT21]

3 hours ago, Radian said:

 

Yes, the valve is often another part that needs cleaning. Is it just there to seal the foam inside the gun when you change cans?

 

Good write-up @Onoff

 

Yeah thats all its for, basically a check valve.

[trialuser]

On 13/04/2022 at 09:51, SteamyTea said:

Yes.  And your nail varnish.

It can also decaffeinate your coffee.

No sure how easy it is to buy small quantities, we used to get 200 litres at a time.

I think this is what was in the proper old nitromors, if you have a can of that knocking about.

[SteamyTea]

1 hour ago, trialuser said:

I think this is what was in the proper old nitromors, if you have a can of that knocking about.

Think that was NaOH, or caustic soda.