Dears,

in our plant the Turning gear is electrical and in black out it can work by EDG. my quetion is if we can provide a pneumatic turning gear, and what is exactly the instrument air pressure required for this operation

 

Dear,

If you r in blackout condition,I don't think that you will also have too much air to operate that system. anyway applicable pressure for pneumatic systems may be anywhere 5 to 10 BAR

Most of power units have electrical system for turning gear operation,few also have hydraulic but that also rely on electric supply
In any emergency manual turning operation is a good option,difficult but can save machine

 

I have never seen a pneumatic turning gear operation.

Typically barring is either electrical in which the case of supply failure is supplied by the EDG and sometimes they have emergency barring motor witch is fed off station battery supply. Or hydromotor - typically fed from rotor lift oil. -with the emergency rotor lift oil pump fed from station battery supply in case of failure.

 

Your plant must be having a battery bank for times like blackout. That should feed a DC emergency turning gear as mentioned by Brian.

 

Dear Gents,

We are operating GE frame 7Fa machine & we have provided the instrument air supply line near turning gear, we have pneumatic tools , turning gear mechanism having a slot there we can insert this tool & operating though instrument air, instrument air pressure would be 8 Bar.

Hope this helps

Regards
Parag

 

Parag,

So, what keeps the Instrument Air system up to pressure during a plant black-out, and for how long can the Instrument Air remain at sufficient pressure to operate the emergency turning gear mechanism?

When was the last time the emergency turning gear mechanism at your site was used to physically rotate the shaft (black-out condition or not)? Is it properly stored and maintained to ensure it will operate properly when needed in an emergency?

(GE is famous for providing rotor turning devices with new gas turbines in years past (they were commonly purchased Options), and they were never installed and tested during commissioning, and the parts just disappeared and couldn't be found nor the drawings to assemble them when an emergency condition arose!)

Do the people who will be using the device at your site have the experience to use the device if necessary? Can they troubleshoot it if it doesn't work as advertised when being used?

A lot of plants have a lot of emergency equipment, which has never been used and which wouldn't work if needed because of the non-use and lack of experience of the people who would be charged with using it.

The air pressure required for this type of device would be dependent on the flow requirement for the pneumatic "motor" as well as the amount of power that would be required of this pneumatic motor. It's more likely that a potential supplier would ask what air supply was available (pressure and flow-rate) and then try to assemble a piece of equipment to meet the need. Because, these aren't likely off-the-shelf items.

And it would be incumbent on the purchaser to ensure (by whatever means) that an adequate supply of air for a reasonable amount of time would be available to operate the device to protect the turbine shaft.

 

Dear CSA,

Accept my apology for late reply, The pneumatic turning device we are using only when some problem with Turning gear motor or M/C did not come to turning gear after stop/trip/shutdown command. & we are not using on continuously, time to time we are turning the shaft to prevent bowing.

Of course, on blackout the instrument air tank capacity is only for 10 minutes only, so we can not use for long time

Regards
Parag