We have frame V GT. Currently 20DV is not hardwired in (MarkVi to MarkVIe upgraded) new system. 20DV is wired in the field. 20DV is configured in Mark Vie but its terminals are open. It is like this for long time .
As mentioned above, 20DV was never in line since GT commissioning. I have recently joined the plant, and I have been assigned to take 20DV in Mark Vie.
Can somebody give me an insight on importance of 20DV? And as I said it was never in line in Mark Vie, then how was GT running without it?
Please guide me in what to look for as I am totally new to Mark VI?
After, "WOW!!!" I would say if the unit has been "operating" without 20DV being connected to and energized/de-energized by the turbine control system, then either it's not required for proper operation of the unit, OR something has been tweaked (field-modified) to allow operation of the unit without the solenoid.
If you're a fresher (complete newbie) to the Mark VI/VIe turbine control system, there's not much we can do on this forum to help you try to decide which of the above is the true scenario. You would need to ask the operators/technicians at site who have been "living with" the situation what was done to get by without the solenoid, and it's most likely the most common answer you're going to receive is, "We've always done it that way!" and, "We don't know any different." Neither of which is going to be of any help to you or us.
Does the solenoid (20DV) appear on the Starting Means P&ID?
Does the solenoid actually exist on the diesel starting motor?
Does someone have to physically go out to the Accessory Compartment after the unit has reached self-sustaining speed and the diesel starting motor goes on its cooldown and do something to stop the diesel starting motor? Because 20DV is usually the solenoid which, on some diesel starting means, when energized by the Mark* physically moves the fuel control rack to shut off the flow of diesel fuel to the injectors, stopping the diesel starting motor after its cooldown (or when tripped while starting).
Normally, 20DV is connected to a solenoid output of one of the discrete output terminal boards of the Mark* (one that provides 125 VDC to its NO or NC and SOL terminals). And, usually, it's connected to the NO and SOL terminals. I believe most Mark VI and Mark VIe discrete output terminal boards require hardware jumpers to be installed to provide the power to the NO/NC terminals and the SOL terminals. You can use the Mark VIe System Guide, GEH-6721, Vol. II, to find the particular terminal board that 20DV is assigned to in ToolboxST to determine what jumpers have to be installed.
BUT, I caution you: If the unit has been running for years (since commissioning!!!) without a functioning 20DV AND it requires 20DV for proper operation, then either something has been modified to permit operation without it, OR someone has been manually shutting down the diesel after every start. It's highly unlikely you, being the new person, will be able to determine which since the site has been "living with" the current situation for years.