Adjustments for Pump with Centrifugal Seals

Who is the pump manufacturer and what is the model number?

I don't know yet.

I've replaced seals on these pumps many times.

There is a spring behind one side of the seal.

It cannot cause binding. The faces of the seals are ceramic. They don't bind.

Centrifugal pumps have shaft seals made like this.

These seals should not inhibit rotation unless they are improperly installed. They are inside the wetted side of the pump.

Does the motor, and pump, spin if not connected to each other?

Hi Lyn and thanks for the reply,

The motor shaft turns freely disconnected.

The pump shaft would mostly turn freely, but in part of the rotation, it would "catch". The tech was making adjustments using bolts on the "motor end" of the pump (in the photo) trying to eliminate this.

As it stands right now, the techs feel like they have gotten it the best that they can and will try to start it up shortly. This pump is used for transfer and recirculation of a 225ºF ammonium nitrate (AN) solution. There is only a small amount of water so I would more accurately describe it as molten NH4NO3. All of the lines are steam-traced to make sure the AN doesn't freeze in the lines.

When this gets started up, I will let you all know, as well as my findings over the next couple of days, how this specific type of pump works.

Adjusting the motor shaft cannot cure a problem in the pump.

I think that what I haven't made clear, is that this pump has dynamic seals. These seals engage when the pump is "at speed". Every time the pump is turned off an amount of the pumped liquid leaks from the pump - this is normal operation for this pump.

Hi spades,

Thank you so much for your reply and spot-on instructions. The tech did get it running - I don't know if he followed your exact procedure, but it was running, sounding normal, and getting a very stable current draw.

I have forwarded your post to him for his enlightenment.

Again thank you and everyone else who has posted here.

Mike

I believe spades is spot on. I used to deal with pumps with dynamic seals. At that time we used a John Crane type 10TC as the static seal. This was basically a type 10, but with counterweights to pull the seal faces apart once it gets up to speed. When the pump is stopped there will certainly be resistance from the seal when you turn the shaft.

You need to be careful with the jacking screws on the rear bearing cover. These do indeed adjust the position of the impeller, but they are quite often used on pumps with open impellers rather than closed impellers to adjust the clearance between the front of the vanes and the housing. If you pull the impeller too far back you will lose performance/efficiency. Check what type of impeller you have.