Pulsing powder flow

[TurbineRepair]

Hi all,

I'm having a bit of trouble with powder flow I'm spray Metco 450 and I notice yesterday that the powder flow seems to be pulsing. I've changed the hopper and moved to the second insert on our twin 10-2 powder feeder but the problem persists. I dropped the gun end of the powder feed tube in some water to watch the flow and it seems to be pulsing bubbles through the water where I would expect to see a steady stream. Can anyone suggest something I could try? - was going so well last week

Jim

[LEN WOOD]

Hi Jim,
Assuming that both hoppers are leak free, sound and unobstructed with powder and that both positions are sound on the Twin 10 unit. The issue must lie with carrier gas supply in or carrier gas/powder feed line out.
Have you checked the powder feed rate?
Are you having this issue only with SM 450?
Has anything changed since you were spraying this material successfully?
Look through the prespex at the disc of the hopper - is this 'disc trench to suction-device' full of powder and is the 'after-suction device disc trench' clean?

Glen

[TurbineRepair]

hi Glen,

I spent most of yesterday playing with this. The powder inserts are a bit worn and I've orders some replacement parts but they aren't too bad. I've checked the feed rate and its bob on at 68g/m with a 16/1.2 wheel speed of 25 rpm. I swapped back to SM 54NS and that was running fine through the same hopper, in fact it was a very good coating if I say so myself
After giving the hopper a good clean and tightening all the bolts I sprayed some more 450, just waiting for it to be polished then I'll have another look. The flame still wasn't as consistent as I would have expected though, we will see.......


Jim

[LEN WOOD]

Hi Jim,

Are you running a Plasma Technik A2000 console? If so then I can tell you how to quickly leak check your Twin 10 hoppers.

A leak would be less likely to cause pulsing in materials with lower carrier gas values.

Are the disc spreaders OK,
Is the stirrer riding the disc?
Is the disc rotation smooth and constant?
Are your powder hose connections good?
How long are your powder lines?

I remember a guy who used to rebuild the hoppers and his 450 always resembled 'ball bearings' in the micrograph!

Cheers

Glen

[Gordon]

Hi Jim

Nothing like a powder feed problem to start your day

Pleased to see Glen helping out.

It's surprising the number of times I've seen operators using a plasma spray where the powder is "machine gunning" and seem to be quite happy in the knowledge that their powder feed rate check gives say exactly 5 lb/hr, but not realising that in real time one moment they might be getting a slug of powder at 30 lb/hr and the next nothing.

Good luck.

[TurbineRepair]

Hi guys,

I've not had chance to try the 450 out again as we ran out spraying production parts in our other booth. How inconsiderate!!
However I've sprayed other materials since and the equipment seems to be ok. I notice a pulsing with inco 718 powder but adjusted the feed rate and carrier gas flow that seemed to solve the issue. I'll starting from scratch again when we get some more 450 and see if it was just my incompetence
Glen,
The system is A3000. There is a feed check button on the powder feed page but I've never pressed it......

Jim

[*Plasma Junkie*]

Hi guys,

I had trouble a few years ago with a CoCraly pulsing flow thru an A3000 / F4 / Twin 10 system. Even performing a feed rate it was really visible even tho a few feed rates back to back were consistent. I put a butchered heater blanket onto one of the powder feeders & it did genuinely help with the flow. Pulsing reduced dramatically during spraying & feed rates. I would never suggest that twin 10s need heater blankets as i dont use one for any other powder. But i guess if ur struggling with one particular powder then it couldnt hurt to try!