Flexible or Rigid Coupling
Flexible or Rigid Coupling
(OP)
I am going to select a pump which is of following characteristics;
TYPE - Vertical
Fluid - Steam condensate
Capacity - 50 m3/hr
Temp - 98 deg C (max)
Seal - Mechanical type
Now my question is "Which type of coupling whould be better for this vertical condensate pump".
My experience is that, there are certain manufacturers which offer rigid coupling in case the pump thrust is faced by motor. But for that arrangement we have to align the pump using dowels on motor foots and its checking is tricky and quite labourous. Ofcourse there is no problem during operation.
Can a flexible coupling be a better choice for this arrangement or it can effect the performance of mechanical seal during long run.
Thanks in advance.
TYPE - Vertical
Fluid - Steam condensate
Capacity - 50 m3/hr
Temp - 98 deg C (max)
Seal - Mechanical type
Now my question is "Which type of coupling whould be better for this vertical condensate pump".
My experience is that, there are certain manufacturers which offer rigid coupling in case the pump thrust is faced by motor. But for that arrangement we have to align the pump using dowels on motor foots and its checking is tricky and quite labourous. Ofcourse there is no problem during operation.
Can a flexible coupling be a better choice for this arrangement or it can effect the performance of mechanical seal during long run.
Thanks in advance.





RE: Flexible or Rigid Coupling
RE: Flexible or Rigid Coupling
At the time pump type and motor configurations are not final. The Situation is in requisition stage. If the configuration is known then it will be quite straight to finalize the coupling, for e.g if the vendor is giving the thrust bearing in motor then the whole of the pump load will be bear by the motor and in this case he will use rigid coupling. On the other hand, if the vendor is giving thrust bearing in pump and will not allow the motor to take up the load then he will use flexible coupling.
For now it is up to me to select the type of the configuration to be used.
Please guide me which configuration will be more effective and efficient from the maintenance and performance point of view.
Thanks.
RE: Flexible or Rigid Coupling
RE: Flexible or Rigid Coupling
I second this statement. An engineer before me did a gear pump that was driven by a very powerful kollmorgen brushless DC motor with a splined rigid couple. I was his replacement and got to fix the design.......we tried a crown splined rigid couple that allowed for some misalignment but the ultimate solution was a flexible couple.
Heckler
Sr. Mechanical Engineer
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RE: Flexible or Rigid Coupling
Johnny Pellin
RE: Flexible or Rigid Coupling
I have also considered the same but a senior machinery engineer told me that you also have to see the fluid which you are pumping. Mechanical seals have very fine clearances between the seal faces and donot encourage the axial movement to be acted on them in vertical position. In my case i am going to pump steam condensate collected from a condenser and the temperature is almost 95 deg C. The axial play which the flexible coupling allows to encounter slight misalignment can cause the seal faces to open with time and can allow leakage.
Is the theory correct and flexible coupling can act in this way....
Although the designs with flexible coupling in vertical pumps are there and are proving successful, i mostly worked with rigid couplings at the fertilizer plant in condensate service and they are trouble free.
Please guide me as i have to select a trouble free design for the new installation.
RE: Flexible or Rigid Coupling
RE: Flexible or Rigid Coupling
Johnny Pellin
RE: Flexible or Rigid Coupling
The information provided is very helpful and surely help me out in my decision.
I would go for flexible coupling design. I have also come across with a design in which there is an intermediate bearing housing between pump and the motor. This design involves two set of coupling, one between motor and bearing housing which is flexible and the other between housing and pump which is rigid. In this arrangement we have a dual advantages of using flexible coupling for better support and rigid coupling for ease of maintenance i-e removing and installing mechanical seal.
RE: Flexible or Rigid Coupling
RE: Flexible or Rigid Coupling
RE: Flexible or Rigid Coupling
RE: Flexible or Rigid Coupling
Design For Maintainability.
When talking with folks who have had to fix things it takes about one comment in a design review.
On the other hand, I witnessed a several day "discussion" with a stubborn apartment dwelling Russian engineer about providing a decent sized access hole for assembly and maintenance.