Pumping Problem

Samsam,

You need to tell us suction and discharge pressures, type of pump and barrier fluid pressure and medium etc. Are you leaking barrier fluid to atmosphere or into the pump, or are you leaking pumped medium into the barrier fluid?

If I understand your description, one pump running by itself is OK. Pumps in series are the problem. If this is correct I suspect that you are getting a seal chamber pressure higher than the barrier fluid pressure.

Hello

Are you using plan API 53 A, API 53 B or API 53 C? Have you any strainer placed to suction line? What is the mesh of the strainer, if the strainer is? Are new pumps? What is the handled fluid? Please detail about pump spec?

You are definitely exceeding the pressure limit of the seals. If I understand what you are calling "back-to-back" seal arrangement, I interpret this to mean a "double" mechanical seal. This is a seal arrangement with two seal faces with an opposing spring between them. This arrangement has definite pressure limitations.

A more appropriate seal arrangement would be "tandem" mechanical seals. That is, two separate seals with their own springs. However, I doubt if you can change the seal to a tandem configuration because the pump is not designed to accommodate it. It may be that you can replace the seals you have with a "stuffing box" that would use packing to accomplish the sealing of the shaft. This, however, would be dependent upon the manufacturer's design.

"Back-to-back" seals or "double" mechanical seals are nearly never a good alternate. There are too many limitations to this type seal. The only advantage that this seal has is that it is cheap. If you are intent upon operating your pumps in series, you may be faced with the necessity of replacing your pumps with tandem sealed pumps. It may prove to be a costly option but quite possibly is the only one.

Hello,

Thank you for attention.

From friday evening everything quiet. After sealings changed - the part from medium up to today , so about 24 h , everything smooth.

Problem leakege to the pump no visible outside.

Pumps designed according to EN 733 , no possibility to do anything else with the sealings without changing the construction.

Pumps in series: 1 pump - open tank , c.a 1,5 m above pump - suction about 1,15 bar. 1 Pump with frequency inverter on the discharge 1,7 bar. On the sunction no problems with strainers , valves elbows - nice smooth straight pipe.

2 pump in series 1,7 on the sunction (discharge of 1) on the discharge 2,1 bar.

API 53 with pressure - termometer , level indicator , pressure transmitter - so i do not checked the version.According to spec 7 bar in the all vessels . In my opinion a little to high but some one has made the spec.

One sealings salesman sayes 0,2 MPa maximum differental pressure sealing chamber / vessel , other one that this is ok. The first man is afraid of leakege from the pump to sealing chamber.

i have send the sealings to analysis but this will take time and some one will do doctorate.

As always i have a idea of some people playing with the system when iam not around:).

Looks quiet - i will wait for the analysis. Thank you for support!