HVOF DJ2600 DJ8W powder feeder issue
06-12-2015, 10:46 AM,
#1
HVOF DJ2600 DJ8W powder feeder issue
Dear HVOF experts,
Need your valuable input to resolve my problem. We have got HVOF DJ2600 DJ8W water cooled gun in which powder could not flow in to the flame. Below are actions taken still the problems persists
1. Carrier gas bottle pressure increased up to 12 bar.
2. Defective powder injector (end eroded) replace with a new one
3. Powder feeder line completely checked for any blockage
When the flame is on the back pressure in the feeder rises spontaneously to around 6 bar and the system trips. Once the flame is off, powder flows out of gun with the the back pressure in the feeder.

Regards
Vetri
Reply
06-12-2015, 07:38 PM,
#2
RE: HVOF DJ2600 DJ8W powder feeder issue
Hi Vetri
The problem is in the hopper, you must change all the O'rings and valves, you are going to have ever problems with this powder feeder, fluidized bed is not good at all for HVOF, if you want to have a good coating, please change the powder feeder ASAP, i was ever doing service for this wrong powder feeder, and you must spend a lot of money to repair it at every time.
Best regards
Luigi
Reply
06-14-2015, 01:51 AM, (This post was last modified: 06-14-2015, 10:40 PM by Johnny_Blaze.)
#3
RE: HVOF DJ2600 DJ8W powder feeder issue
(06-12-2015, 10:46 AM)vetrinit Wrote: Dear HVOF experts,
Need your valuable input to resolve my problem. We have got HVOF DJ2600 DJ8W water cooled gun in which powder could not flow in to the flame. Below are actions taken still the problems persists
1. Carrier gas bottle pressure increased up to 12 bar.
2. Defective powder injector (end eroded) replace with a new one
3. Powder feeder line completely checked for any blockage
When the flame is on the back pressure in the feeder rises spontaneously to around 6 bar and the system trips. Once the flame is off, powder flows out of gun with the the back pressure in the feeder.

Regards
Vetri


Hi Vetri,
It definitely sounds like some sort of leak in your powder feeder. Once the gun is in operation, based on your description, the hopper pressure is unable to overcome the back pressure of the DJ2600 preventing the powder from flowing, but when it flames out it is capable of carrying the powder through the feed line.

This indicates that the powder hopper is not capable of building up enough pressure to over-come the back pressure of the DJ2600 when it is operating.

One problem I also experienced with the DJ2600, just after ignition, the back flow of the uncombusted Hydrogen would combine with the oxygen from the heat and form water droplets at the connection point of the powder injector line causing the powder blockage or obstruction. After shutting down the gun, the hopper back pressure would push the clumped powder out of the gun and would leave no evidence of what was causing the problem. The solution I came up with once I established that there were no leaks in the powder feeder and accidentally discovered the condensation forming in the powder line right at the feed line connection point, was to let the carrier gas flow for a minute or two after ignition to allow the feed line to dry out before starting the powder flow.

Hope this helps.
Regards,
John
Reply
06-15-2015, 01:05 PM,
#4
RE: HVOF DJ2600 DJ8W powder feeder issue
Thanks Mr. Luigi and Mr John,
As said I too strongly suspect the powder feeder. I know there is a leak at the feeder O-ring but it actually works with plasma gun SG100 may be there is no back pressure during plasma spray. I wil try replacing with a new o-ring vacuum grease and arrest the leak and check once again. Mr. Luigi can you suggest the right powder feeder model for this HVOF gun.

Regards
Vetri
Reply
06-17-2015, 12:12 AM,
#5
RE: HVOF DJ2600 DJ8W powder feeder issue
(06-15-2015, 01:05 PM)vetrinit Wrote: Thanks Mr. Luigi and Mr John,
As said I too strongly suspect the powder feeder. I know there is a leak at the feeder O-ring but it actually works with plasma gun SG100 may be there is no back pressure during plasma spray. I wil try replacing with a new o-ring vacuum grease and arrest the leak and check once again. Mr. Luigi can you suggest the right powder feeder model for this HVOF gun.

Regards
Vetri

Hi vetrinit,
Be certain that the o-ring that you need to change is not from a line that carries powder. Wherever powder is flowing you'll want to use a graphite based powder lubricant....basic rule...use powder where there is powder.

I have used a Metco DJP (HVOF) powder feeder for over 20 years and have yet to encounter a problem with one unless proper maintenance has not been maintained.

Regards,
John

Reply
06-17-2015, 04:39 PM, (This post was last modified: 06-17-2015, 04:57 PM by loriolo.)
#6
RE: HVOF DJ2600 DJ8W powder feeder issue
Hi Vetri
I do not believe what John said, because I must repair more than 20 DJP unit for many years, fortunately there were only 20, the problems do not happen with all kind of powder, but if you are using a kind of powder with fines, and you have to clean the barrel every time, it causes that powder come back to the powder feeder and usually damage the following parts: DJP 600 pinch valve ass.bly, DJP 83 Duck bill Valve, and as in a HVOF system there are too high pressure, every time you have problem you must change this pieces, and some time if powder reach the regulator, you must change it (part. DJP 39 Regulator ass.bly), and change too all seal (seal package DJP 68).

Hi Vetri
I forgot to answer your second question, All equipment OEM, has now the equivalent powder feeder of the twin type for HVOF which work very well, (because do not has fluidized bed like the batty DJP or 9MP or 5MP in which you have carrier gas related with the carrier gas pressure), all of them has the update to your DJP, you can get it from FST, GTV, MEC, .......and so on, you can have the cheaper with high quality.
Best regards
Luigi
Reply




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