Consistent Mechanical Seal Failure on Armstrong 4300 pump
Consistent Mechanical Seal Failure on Armstrong 4300 pump
(OP)
Hello,
I am a tech for a pump motor and controls company in ny and have been having issues with one set of pumps. The pumps (2) in question is an vertical Armstrong 6x6x11.5 4300 series being driven by a 25hp 1800 RPM electric motor on VFD. There is an aluminum coupling with keys between the motor and pump with 3 Allen head bolts. The pump is used for cooling the engine of a generator in a rooftop CoGen plant. The water/propylene glycol mix leaves the engine coolant circuit at 200*F and is about 177*F when it hits the pumps. There are two pumps on the condenser side of the loop, same pump, same motor, same seal that have 0 issues.
I have been back to replace these seals 2 times already this year. The only evidence that the seal is leaking is the residue left behind after the water evaporates away. Its a very flaky white residue. The seals begin to leak and the leaks gets worse and the amount of residue increases (obviously). When i remove the seal there is no evidence of cracks, excessive wear on the faces, or damage to the shaft. With a rag and some brake clean seal faces can be cleaned and appear to be slightly used but not damaged. The flushing liquid does get filtered before flushing the seal. The seals in question are 1.625" Crane Type 8B2 Armstrong #975002-334
I can provide pictures of the seal on the pump, and after cleaning the faces, (residue is still on the seal cartridge) if necessary.
Thanks for taking the time to read this, and any help would be greatly appreciated.
I am a tech for a pump motor and controls company in ny and have been having issues with one set of pumps. The pumps (2) in question is an vertical Armstrong 6x6x11.5 4300 series being driven by a 25hp 1800 RPM electric motor on VFD. There is an aluminum coupling with keys between the motor and pump with 3 Allen head bolts. The pump is used for cooling the engine of a generator in a rooftop CoGen plant. The water/propylene glycol mix leaves the engine coolant circuit at 200*F and is about 177*F when it hits the pumps. There are two pumps on the condenser side of the loop, same pump, same motor, same seal that have 0 issues.
I have been back to replace these seals 2 times already this year. The only evidence that the seal is leaking is the residue left behind after the water evaporates away. Its a very flaky white residue. The seals begin to leak and the leaks gets worse and the amount of residue increases (obviously). When i remove the seal there is no evidence of cracks, excessive wear on the faces, or damage to the shaft. With a rag and some brake clean seal faces can be cleaned and appear to be slightly used but not damaged. The flushing liquid does get filtered before flushing the seal. The seals in question are 1.625" Crane Type 8B2 Armstrong #975002-334
I can provide pictures of the seal on the pump, and after cleaning the faces, (residue is still on the seal cartridge) if necessary.
Thanks for taking the time to read this, and any help would be greatly appreciated.
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
Keith Cress
kcress - http://www.flaminsystems.com
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
The company I work for is actually dealing with a similar issue. We've had a customer smoke the seal on one of our pumps a few times. Our working theory was low flow was failing to remove heat and allowing the surfaces to overheat.
We sent the failed seals to our mechanical seal manufacturer, they performed an analysis and determined rust and particulate in the water was plating the face. We're looking at moving our seals over to a more robust version that has better heat dissipation and handles contamination a bit better.
Multiple failures can point to a service condition issue, but it can also point to an installation issue. ANY contamination on the seal face, even oil from your hands, can be enough to allow a leak, which then propagates into a real issue over time. If the techs installing the seal are pressing it in by hand without anything between their hand and the seal it's likely going to fail out of the gate, or very soon.
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
I may have to send out the next one and see what is going on. They run monday-friday for about 10 hours when the Co-Gen plant is running, only one pump at a time. I think they are on a daily alternation schedule. I agree that any contaminants on the seal face would result in premature failure and I am very careful to install clean seals, make sure no contact with faces happen, and i make sure there is nothing in between them. And like i mentioned, these are the only 2 pumps i have giving me this issue. I was thinking it could be a flow issue with seal flushing, as running pressure differential is only about 18 psi. There is shelco cartridge filter on the flushing line that is clean. I know a cyclonic separator needs a 20 psi differential to work properly. Im wondering if there can be a similar issue with this filter.
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
Is it an open (header tank) or closed (pressurised) system.
We solved a lot of similar problems by going to pre mixed coolant (uses de min water)
AND TOPPING UP WITH PRE MIXED COOLANT. NOT TAP WATER!mg
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump
@quadtracker- yes, these armstrong couplings will not touch, they are tightened to spec evenly and measured with a feeler gauge for the an equal gap. And i just had a situation with one that was not closing properly and it lead to a vibration and a noise. neither are present with this pump. Next time i go to the site i will have to try your suggestions. The vibration analysis I did on the motors does not indicate any bearing wear though. Thanks for your help! Ill have to bring my dial in next time. there is play in the pump shaft, when the pump is un coupled but it is nice and solid when everything is bolted together.
@georgeverghese this was my initial though
@Hoxton ive never had the seal analysed, how ever the coolant was analysed. its a small concentration of propolyne glycol according to my seal vendor it is nothing the seal shouldn't be able to handle. It is a closed loop pressurized system the coolant ran thru the generator engine.
Thanks!
RE: Consistent Mechanical Seal Failure on Armstrong 4300 pump