the poor vaccum in condenser

A couple days ago we had problem related to poor vaccum in steam turbine condenser.
The vaccum was on the level of 81-82 kPa. The normal level is around 90 kPa. Low vaccum creates the unit load limit that is so important keeps it as designed.
Before the vaccum drop there had been a turbine trip. The machine was taken in service again but trough the some moment the LP bypass got pressurized and the LP bypass pipeline shook.  The turbine was operated under stable condition but the vaccum did not come to previous, required level.
All vaccum pumps were taken into service but it did not help, in paralel we started to search for the reason.
The fitters found the manhole withe air ingress. The manhole is located on the LP bypass pipe just before the connection of it with condenser shell. It was sealed, the screws tightened (some of them were loose). The vaccum is improved now almost 90 kPa.

The BFP mechanical seals coolers

The unit we operate and maintain is equipped with 3 boiler feed pumps.
Two of them are turbine driven and the third one is motor driven.
To prevent feed water going out of the pump the mechanical seal is in place.
The temperature of the feed water is 160 C deg (at full load - 600 MW it can be even 180 C deg)
The temp of the BFP casing is 136/132 C deg (lower part/upper part respectively).
The original desing of the BFP include the cooling circulation of the mechanical seals:

The reason of this cooling is simple the mechanical seals OEM put the remark in seals manual that seals working temp should not be higher than 80 C deg (at 90 the manual pump trip should be applied).
The eraction team has done some modification in the cooling system and what we have on site is:

  There is no cooling provided and the working temp. of mechanical seals is 50 C deg than it was designed. Definitely, it is going to affect seals lift time. Our proposal is to put the coolers back in place according to OEM design.
We will see what will  happen

Came back

It has been long time when I put here last post.
There is a reason for this. It can be said that I am on the opposite side just now. Why?
Yeah, previously I was a part of company offering the unique and specialized services for power plants. It was great job ... . Anyway I felt that time that my knowledge is not complete. Yes, I dealt with steam turbines and a number of technical issues related to them but I was still out of the place where the steam turbines are used daily - the power plant.
Just now I work for company which run power plant, quite large ... 4 x 600 MW.
So, I am still within power industry but in the other corner. It is not the same what I did before but can almost touch the turbine while it is working.
The blog is going to change accordingly. Still it is dedicated to the steam turbines but more to their daily maintenance than overhauls but sooner or later the overhauls will come.