Has anyone installed MD&A's Guardian Packing?

[Turbineboy]

We have installed MD&A's Guardian packing on one of our Units with poor results after the outage. We have found one other guy on a Yahoo group that had similar results. Has any one else out there from a steam power plant installed this packing? What were your results?

 

[byrdj]

Any more on what "poor results" were.

I was on one unit that had problems where the laser alignment went poor and vibrations were bad till unit was opened and realigned.

 

[Turbineboy]

What I mean by poor results is a loss in HP efficiency. A pre-outage Heat Rate summary shows us having an HP efficiency of 78%. Post outage HP efficiency is 74%. We also had a rise in HP outlet temperature by 30 degrees F. Currently having Maintenance check the accuracy of our outlet measurements to confirm.

 

[rmw]

The guardian packing has the "rub rails" for lack of a better term that hold the packing away from the shaft. That is good if you don't want the packing to rub all the teeth away. That is bad if you want he teeth to have a close fit to the high/low lands on the shaft so that the tortuous path is created. No benefit comes without a tradeoff.

rmw

 

[byrdj]

I was under the impression the radials WERE set tighter since you did not need to allow for transiants that lay down (wipe) the teeth.

 

[rmw]

The Guardian packing has a pair of 'rub rails' which are longer than the teeth themselves that contact the shaft and push the packing away from the shaft. The rub rails are a hardened material (unlike the teeth which are soft) which will withstand prolonged contact with the shaft. That is OK if the goal is to never let the teeth contact the shaft and erode the teeth, but since the 'rub rails' have to be longer than the teeth by definition in order to protect the teeth from contacting the shaft, they never let the teeth get any closer than the rub rail's dimension to the shaft.

Teeth that are 'rubbed in' will have some tooth loss, but the resulting dimension will be closer than Guardian packing allows.

In a sense, the 'rub rails' are the only two teeth that have any chance of sealing at all. The other "multi teeth" of multi tooth packng are too far from the shaft to do any good.

That is what I think turbineboy's problem is.

rmw

 

[byrdj]

Have you had a chance to check your instrumentaion yet?

 

[Turbineboy]

No not yet. We have had a generator go to ground so that has kept us busy. Had to remove three stator bars. Unit is still down and probably will be for some time.

 

[byrdj]

sorry to hear that...especially with this summer's demand