Welding a wood pellet bin - fire risk?

[Bill Edwards]

I'm looking at a job which is welding a wood pellet hopper where it has been stitch welded and every time more is blown in dust blows out from all the gaps making a big mess, hence looking to weld it all up into a continuous bead.

My only concern is regarding whether the pellets or dust could catch fire? It could be done with it full or empty, but when I say empty there would still be some in the bottom, i.e not completely empty, and obviously dust would remain.

Thoughts?

 

[Maker]

I would think you definitely don't want any air born dust, fine dust has a tendency to explode. Completely empty would be my first choice, but if there must be some left in the bottom, could you cover them up with a welding blanket?

 

[Paul.]

Dust can be very dangerous, a flash fire caused by paper dust in a packaging factory nearly killed a fitter I knew some years ago, safest way is to completely empty it out and damp it down

 

[brightspark]

I'm looking at a job which is welding a wood pellet hopper where it has been stitch welded and every time more is blown in dust blows out from all the gaps making a big mess, hence looking to weld it all up into a continuous bead.

My only concern is regarding whether the pellets or dust could catch fire? It could be done with it full or empty, but when I say empty there would still be some in the bottom, i.e not completely empty, and obviously dust would remain.

Thoughts?

wet it-if nearly empty and -clean it out -

 

[HMB]

Anything in dust form can create a bad hair day. Grain terminal near me are super anal with any hot works

 

[Bill Edwards]

At the time of welding the dust should all be settled so it won't really be airborne. But it will be stuck where the welds are to be done.
This could be a bigger job than I was hoping for.

 

[HMB]

No no no no. Dust airbourne or not. No hot works. Only takes a fart and your back to an explosive atmosphere.

 

[brightspark]

At the time of welding the dust should all be settled so it won't really be airborne. But it will be stuck where the welds are to be done.
This could be a bigger job than I was hoping for.

are u insured for hot work -and risk

 

[Spark plug]

If it is structurally sound and your only trying to archive a sealed environment, could you not seal the joints with a sealant of some sort?

 

[adam1181]

up until recently i spent 2 years installing, commissioning and servicing wood pellet boilers. the dust can be very flammable and even ignite by static hence why the delivery trucks use an anti static strap when they blow them in.
The dust is also hazardous to breath in so use a dust mask anytime your in the tank.
Wetting it down will cause problems as wet pellets swell up, block the feed pipes and set like concrete. Ive spent hours drilling and chiseling pipes out from wet pellets.

The only safe way is to completely empty it and preferably disconnect it from the boiler. Also I'm sure you'd have noticed but most tanks are galvanized so watch out for fumes.
Could you not rivet a plate on instead i would be quicker and easier.

 

[Bill Edwards]

Oh dear...

It's not galvanised, it has been custom built to fit inside the boiler room and just painted, it's sort of two hoppers connected together at the top and space between them to walk through to the rest of the room. Of course, this means there are a lot of areas it can leak from due to the shape. I was expecting to scrape the areas to weld to remove the worst of the paint, mig the gaps and brush some paint on.
It wouldn't be practical really to rivet plates on, I did wonder about sealant but have doubts about whether it would adhere well enough.

 

[adam1181]

Ive built a few from made by this company http://www.woodpelletstorage.co.uk/ these are just bolted with 6mm bolts and sealed with a bead of sealant around all the joints. It would be worth checking there is enough ventilation in the tank so pressure isn't building up and blowing it slowly apart.
All solid tanks should have 2 filling ports 1 for blowing in and 1 for dust extraction/pressure relief.

 

[Bill Edwards]

I've seen that kind, but is the sealant between the parts bolted together, rather than added on to sit on top after welding as would be the case with the one I'm looking into doing.

 

[adam1181]

in there construction manual they say to seal between all joints then run a bead of sealant on the inside on all joints and seams. there sealant isn't silicone tho it's a metal bonding sealant with a foreign name that i can't remember but i have successfully used ct-1 before.

 

[pedrobedro]

Stick some gaffer tape over the join.

 

[GKQ]

Use car body sealer, sticks anything to anything. Even used it under water to seal a swimming pool drain. Nitrile seal impervious to most chemicals to. Clean area with acetone ( no smoking ) and bond, touch dry in 30 mins and sets in 24 hours. Can use glass fibre tape in it to cover large voids. Graham.

 

[MoreWellie]

tiger seal is good for seam sealing but don't expect to keep any opened tubes for very long

 

[500e]

Lord structural adhesives
http://www.lord.com/products-and-solutions/adhesives/lord-7555-urethane-sealantadhesive
Not used above one

http://www.lord.com/emea/products-and-solutions/adhesives/lord-406e-acrylic-adhesive
The 406 sticks like to a blanket have used it ti bond SS to alloy you would not believe how difficult it was to remove 2 years later
Not cheap though

 

[blenkie1]

Big factory not far from me making chipboard seemed to be on fire every week. Very fine dust causing the problems. Have there own fire brigade. Seemed to have cured the problems now.

 

[mike os]

as above, try a sealant/adhesive... pu based stuff sticks well