Ozziecat
Member
- Location
- Royal Oaks, CA USA
Will a pump motor, say 3 phase 10 hp prematurely need a carbon/ mechanical seal if the motor is not mechanically fixed to the platform it sits on?
Pump motor
- Thread starter Ozziecat
- Start date
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kwired
Electron manager
- Location
- NE Nebraska
If motor and pump are not securely connected to each other, yes.
If pump and motor are basically one assembly and that assembly is not securely fastened to something, you may have problems with piping or other external items eventually but the shaft and seal are in a secure position in relation to one another and should not have much effect at all on them.
I think this is what you are asking about.
If pump and motor are basically one assembly and that assembly is not securely fastened to something, you may have problems with piping or other external items eventually but the shaft and seal are in a secure position in relation to one another and should not have much effect at all on them.
I think this is what you are asking about.
weressl
Esteemed Member
Not necessarily so, it depends on how the motor is coupled to the pump. A self-aligning, flexible coupling would be forgiving of alignment problems that would be the source of premature seal wear. A completely free floating motor on a flexible coupling would be pretty darn unheard of.....I mean what holds the motor in place? The conduit?
BTW the MOTOR would not have a mechanical seal, but the pump may, so I think you're asking about the replacement of the seal on the pump.
ptonsparky
Tom
- Occupation
- EC - retired
The few pumps I have been around, running them dry was a killer on those seals.
kwired
Electron manager
- Location
- NE Nebraska
Some actually have piped small stream of water to exterior side of seal to keep the seal wet and probably even helps keep it cooled.
Real common on pumps in a dairy processing plant - and probably many other similar applications.
Good mechanical seal does not have any visible water leakage: water evaporates as soon as it comes out of the seal. Any water leakage in a mechanical seal is a sign of failing seal.
kwired
Electron manager
- Location
- NE Nebraska
I was not talking about leakage, I was talking about pumps that have running water on the seal, there is water all over the place and it is hard to tell if the seal is in fact leaking if water is the pumped media. In the dairy plant though if the water has a milky color to it then the seal must be leaking, and at a pretty good rate if it turns the water color.
weressl
Esteemed Member
Do not disturb the man in his favored past-time......
You are funny. :thumbsup:
- Location
- San Francisco Bay Area, CA, USA
- Occupation
- Electrical Engineer
Maybe your experinece is limited.
There are indeed seal systems that are designed to use clean water for the seal and when they are working AS DESIGNED, water flows out of them.
Example: http://www.aurorapump.com/EngineeredProduct_Sewage_WaterSeal_681.aspx
weressl
Esteemed Member
You seem to be forgetting that you're addressing the all-knowing Haji here..........:dunce:
Pumps with packing ring type seal do leak water through the seal thereby waste energy. Mechanical seals are designed to minimize this waste. As for your link, more details are required. May be the clean water requirement is also to contain the odor coming through the mechanical seal of the sewage pump.
Yes. You are. My point is lubrication and thereby cooling also is provided in the Mechanical seal by the pumped fluid itself and if extra cooling of seal is required, it is to be taken care by the pump designer by providing, for example, a heat exchanger. Adhoc cooling of mechanical seal of a pump in the field is not mentioned in the pumps maintenance manuals.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Fire pumps are an example of packed type seals that leak on purpose.
kwired
Electron manager
- Location
- NE Nebraska
How is it you know more about what I am thinking than I do?
Here is some data from a type of pump I am somewhat familiar with that I have seen used with water on the seal - this is not pumped media water, it is externally supplied water to the seal. After reading this I understand even more what this water is piped to the seal for. I just assumed in the past it either helped maintain the seal, maybe keep it cooled, but there is more to it than just that.
http://www.fristam.com/DesktopModul...ore_Download&EntryId=252&PortalId=0&TabId=301
See page 11 of the document, here is the most relavent text from that page:
Check for vibration of the pump set. If vibration is considerable due to improper sitting of the pump set, it affects the life of the mechanical seal of the pump. This relationship between vibration and mechanical seal life of a pump is mentioned in
http://asmedl.org/getabs/servlet/Ge...2274000005000001&idtype=cvips&gifs=yes&ref=no
[h=1][/h]
wallypiper
Member
- Location
- Atlanta, GA, USA
Centrifugal pumps are generally divided into two categories with regard to the OP's original question: base mounted (not my term, industry jargon) which refers to a separate pump and motor with a flexible coupling of some kind between the shafts, or close coupled, in which the impeller is mounted directly onto the motor shaft. The motors are specific to the application and have special shafts and special tapped holes in the end face for mounting an adapter between the motor and the back plate of the pump.
For a base mounted pump, the pump and motor MUST be rigidly mounted relative to each other and pretty well aligned or seal damage will occur quickly in the pump and/or bearing damage will occur in both the pump and the motor.
Close coupled pumps can be mounted to the pipe via the inlet and outlet connection with no other support required in some cases. It generally depends on the relative size of the pump and motor. A large pump with a small motor may be as described whereas a small pump on a large motor may be supported only by the motor feet. Most common is the pump supported by the piping and the motor bolted or pinned to a rigid support base of some kind.
Close coupled pumps are uncommon above 50 HP, almost unheard of above 60 HP. C-face motors for 75 HP and above can be had but are special special. I would never use one unless space limitations made it the only choice. Too hard for the end user to get a new motor if required.
So the answer to the original question is, of course, it all depends. You can install an inline pump (inlet and outlet connections facing opposite directions with a common centerline) with the motor mounted above it supported entirely but the pump itself IF THE PUMP IS DESIGNED FOR THAT. Not all are. If it's designed for it, though, you will not have any seal issues related to that arrangement.
Any arrangement that results in stress on the pipe connections will probably result in premature seal failure. Any arrangement that results in stress on the motor/pump connection that exceeds the design limits of that connection will also result in premature seal failure. Seal life depends on lubrication and parallel alignment of the stationary and rotating elements. Motor mounting has no effect on lubrication but could affect the seal face alignment. One side of the seal is mounted to the pump housing. One side is mounted to the motor shaft. Any mounting arrangement that causes some deflection of the pump or motor from it's designed/machined alignment will cause a problem.
For a base mounted pump, the pump and motor MUST be rigidly mounted relative to each other and pretty well aligned or seal damage will occur quickly in the pump and/or bearing damage will occur in both the pump and the motor.
Close coupled pumps can be mounted to the pipe via the inlet and outlet connection with no other support required in some cases. It generally depends on the relative size of the pump and motor. A large pump with a small motor may be as described whereas a small pump on a large motor may be supported only by the motor feet. Most common is the pump supported by the piping and the motor bolted or pinned to a rigid support base of some kind.
Close coupled pumps are uncommon above 50 HP, almost unheard of above 60 HP. C-face motors for 75 HP and above can be had but are special special. I would never use one unless space limitations made it the only choice. Too hard for the end user to get a new motor if required.
So the answer to the original question is, of course, it all depends. You can install an inline pump (inlet and outlet connections facing opposite directions with a common centerline) with the motor mounted above it supported entirely but the pump itself IF THE PUMP IS DESIGNED FOR THAT. Not all are. If it's designed for it, though, you will not have any seal issues related to that arrangement.
Any arrangement that results in stress on the pipe connections will probably result in premature seal failure. Any arrangement that results in stress on the motor/pump connection that exceeds the design limits of that connection will also result in premature seal failure. Seal life depends on lubrication and parallel alignment of the stationary and rotating elements. Motor mounting has no effect on lubrication but could affect the seal face alignment. One side of the seal is mounted to the pump housing. One side is mounted to the motor shaft. Any mounting arrangement that causes some deflection of the pump or motor from it's designed/machined alignment will cause a problem.
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wallypiper
Member
- Location
- Atlanta, GA, USA
Fire pumps are an example of packed type seals that leak on purpose.
I may be out of date as I have not dealt with a packed seal in many years, but when I did deal with them, a very slow leak was how you knew you had the packing properly compressed. No leak meant too tight.
wallypiper
Member
- Location
- Atlanta, GA, USA
In some pump applications, the water pressure at the seal face may be less than atmospheric pressure outside the seal. Pumps used in that situation may have an external line piped from a high pressure point in the pump (near the discharge) to the seal face area to increase the pressure there and provide lubricating flow. Without that, the seal will leak backwards, with air passing through the seal into the pump.
Some pumps, especially those pumping dirty fluids with abrasive dirt or the like in them, have seal flush arrangements that pump clean water to the seal face since dirt in the fluid will wear out the seal. I haven't seen an externally supplied cooling setup but don't doubt that it exists. High temps are also hard on seals.
hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Yeah, the sprinkler people said if its not leaking, it's not a good sign! They even have a catch basin and drain under it.
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