Close-Coupled Reliability
Close-Coupled Reliability
(OP)
In actual practice, what is the reliability of close-coupled horizontal pumps vs. properly aligned long mounted pumps?
I will be buying pumps for an application that will require very high reliability. They will be mag drive, where the alignment does not matter as much. Does anyone have experience with mag drive close coupled pumps? Will there be a real difference between close coupled and long mounted?
Fluid: deionized water (radioactive)
Pump HP: 10 to 50
I will be buying pumps for an application that will require very high reliability. They will be mag drive, where the alignment does not matter as much. Does anyone have experience with mag drive close coupled pumps? Will there be a real difference between close coupled and long mounted?
Fluid: deionized water (radioactive)
Pump HP: 10 to 50





RE: Close-Coupled Reliability
I tend to like close coupled pumps because you don't have the potential alignment problems that come with couplings.
There are so many many variables when doing a proper alignment such as hot vs. cold, soft foot on motor, etc., unless you have someone knowledgeable and experienced it's not likely you will get a good installation.
The downside is if you have a pump seal failure with a very aggressive fluid and it gets into the motor, then it's possible to have a motor bearing or winding failure.
I'm not familiar with a mag connected pump-motor set. But if you can physically separate the motor from the pump and drive it with reasonable efficiency, then I guess you would have the best of all possible worlds.
fredb
RE: Close-Coupled Reliability
The downside is that maintenance can be more difficult. Not an option to pull out the pump or motor individually... they gotta come together. If you should have a motor winding failure you'll have to tear into your radioactive system to repair when you wouldn't have had to a coupled machine.
wouldn't have had to?
RE: Close-Coupled Reliability
In magnetic coupled pumps, actually pump and motor are not hydraulically connected. They are connected by two parts of magnetic material. There is magnetic coupling half inside surrounded by casing and on top again second half of coupling. As the drive depends purely upon magnetic force, the efficiency is lower.
Regards,
Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.
RE: Close-Coupled Reliability
You should bear in mind that close coupled pumps come in two basic designs. One is the extended motor shaft (ie special one piece shaft through the motor to the pump impeller) and the other is the standard motor with a coupling which clamps and joins the pump and motor shafts. Sometimes the extended shaft is of two materials (MS in the motor and SS in the pump) and they are joined by friction welding. If you have any shaft failures these are not so easy to replace.
Another issue to consider is hydraulic thrust. End suction pumps have quite a high axial thrust caused by hydraulic imbalance around the impeller. This has to be taken up by a bearing. Close coupled pumps usually have a special bearing fitted at the drive end of the motor to handle this thrust so the motor is not a standard.
I hope this helps.
RE: Close-Coupled Reliability
RE: Close-Coupled Reliability
close-coupled
long-coupled
direct-coupled
And what do you call a motor and pump on the same shaft with no coupling?
RE: Close-Coupled Reliability
I have used mag couplings before but not at this shaft power so I am unable to comment on their reliability. In the smaller sizes they are very reliable.
As the two shafts will be seperated by using a mag coupling there will should be no thrust transmitted from the pump to the motor.
RE: Close-Coupled Reliability
Hope this helps :)