this is my 2nd question posted here at control.com on the confusions i have in my plant.
this time it's about the seal steam.
As per the design, the turbine has 2 seal steam lines which is the supply steam and self steam.

The supply steam will be used during startup and once the machine is capable of self sealing, the supply steam valve should fully closed. However now although the machine is self sealing, the supply steam valve is still opened at 15.7% and it is dumped to the hotwell as the seal steam dump valve is opened at 84.9%.

This has certainly reduced the efficiency of the steam turbine as useful steam is wasted to the hotwell.

my question here is:
is the markv logic is correct on this matter?
if it is correct, then i assume that its a form of safety feature where in case the self steam level has dropped suddenly then the supply steam could help 2 maintain the pressure by closing the dump valve.
If it is not, then what shall i do to resolve this issue?

any1 having the same problem?

thx in adv

 

What is the gland steam pressure set point. Is the seal steam pressure at this set point. Is the seal steam supply valve operating in its normal range when a visual check of the valve stem position is done. If not check seal steam regulating valve field control device for operation/calibration, check seal steam pressure transmitter for correct calibration. Check also operation of dump valve in the same manner as above.

 

Sorry for the late reply... was on leave for the past few days. The gland steam pressure and seal steam pressure setpoint is at 0.2 bar. From the visual inspection, all the valves observed were in good working order. The transmitters were also ok.
Are there any other factors affecting this situation or is the design made in such a manner?
I was informed that as for MarkV, the logic signal for the control valve and dump valve is the same where as for Mark6, the logic are 2 different signals. Is this true?

Thx.