Option to run AC lube oil in manual YES OR NO

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Thread Starter

Craig

I have arrived on site and the local operator is complaining they can't run the AC lube oil pump for the turbine in manual. They want this for flushing and to check why the system is not making pressure.
Previous sites usually have the option to put the switch gear into local and start/stop pump, but this is not the case here. So should they have the option via the HMI or switchgear to start/stop the pump?
 
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Dave Amundson

I can't comment on your switchgear options to run the AC lube oil pump, but bearing lube oil feed lines often have flow restricting orifices in them to control the oil flow rate, and to prevent a major loss of oil to the other bearings should a internal pipe break or bearing wipe open up the clearances. These orifices are often removed during an oil flush to increase the flow rates, and this will result in a reduction of system pressure. You can check the amp draw of the pump and compare it to past data. If pressures are down because of excess flow, the amps will be higher than normal. If the pressures are down because of a restriction of flow (such as a restricted pump discharge check valve), the amps will be less than normal.

With emergency DC pumps, you need to check the pump speed and field current. The pump speed will vary with the field current and will change as the field winding heats up.
 
Craig,

Every site is not the same. It all depends on what was bought, what was sold, and what was delivered relative to the other two. Anything other than that should be accompanied by a purchase order.

It would certainly seem unusual that the "switchgear" (the Motor Control Center motor starter) for the AC L.O. pump motor doesn't have the ability to start and run the pump motor in HAND or MANUAL. But, if that's what was provided for them, that's what they have to work with.

As for whether they "...should..." have the ability to run the pump motor from the HMI or the "switchgear", it depends on what they paid for, what was sold, and what was provided. If what was provided was what they paid for, then they have to work with what was provided. If what was provided was not what was paid for or it wasn't what was sold, then that's another issue altogether.

If you work for the OEM or the packager of the equipment, what does your company usually provide? If this is an unusual contract, where someone else provided the "switchgear" then it would seem that either that ability wasn't specified or wasn't provided--and it was either missed on delivery/commissioning or it wasn't purchased.

If you're asking if you should program the HMI and turbine control system to give them the ability to start/run the pump motor from the HMI, that's up to you and/or the Company you work for. If it wasn't a purchased option, then either someone forgot to purchase it or they consciously didn't purchase it to save money. So, perhaps they should pay for adding the ability to start/run the pump motor into the control system AND the HMI--because it's probably not just as simple as re-configuring the HMI display.

So the answer depends on a couple of factors: What did they buy? and What was supplied? It's really that simple. (A lot of sites don't know what they bought, but they can sure make a lot of assumptions.)

On most of the turbine control systems I've worked on, people are foaming at the mouth (meaning they are greatly anticipating) any opportunity to force logic--hell, they just want to force anything! That seems to really give a lot of people a very great thrill for some very strange reason. They should be able to force the discrete output that starts the AC L.O. pump motor to run the pump if they don't have a means to do so from the pump's motor starter ("switchgear").

They could also use a jumper at the motor's motor starter to start and run the motor (but that's never as thrilling or satisfying as forcing a signal to do the same thing!).

Be wary of modifying the logic to add a signal which can be driven by a target on an HMI display--I've seen people do this with disastrous consequences.

Dave Amundson is right--when flushing is being performed, pressure isn't what's required--it's flow, and lots of it. The more flow, the better the flush. It's not pressure that moves dirt and contaminants as much as it's flow that does it. Usually, especially when flushing the hydraulic system, it's not possible to have rated pressure because the flow-rate is so high with the flushing blocks in place. Same with lube oil flushing; removing orifices increases flow-rates, and increased flow-rates will show up as higher than usual AC motor currents and also as lower pressures if the pump curve is exceeded.
 
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