Welding Near Gas Turbine

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Thread Starter

dax2172

We have GE make frame6 Gas Turbine of 30 MW capacity. Initially we had MarkIV speedtronic control system which is now upgraded to Mark VIe. Why is it not advisable or permitted to do welding near Gas Turbine?
 
dax2172,

Is this written somewhere in some official GE or control system packager document?

How "near" to the gas turbine is "near?" On a pipe or some structural steel beam of the gas turbine or one of its auxiliaries? On a pipe or some structural steel not part of the gas turbine or one of its auxiliaries? On a bearing or bearing pedestal of the gas turbine, reduction gear or generator? Where, exactly, will the welding be taking place?

This is a common question, but the answer is very simple. When welding on some piece of structural steel or pipe associated directly associated with the gas turbine or one of its auxiliaries its very important to have the ground/earth of the welder connected very close to the point where the welding is to be done. In other words, don't connect the welder ground/earth lead to some piece of structural steel or pipe 10 meters away from where the welding will actually be done, or to some piece of structural steel or pipe not associated with the gas turbine or its auxiliaries. Find--or scrape the paint away from--an area within a meter or less of where the welding is to be done to attach the welder ground/earth. This way, the current will not have far to travel between the welder and the return, and will not travel through conduit or piping associated with some field device/instrument connected to the turbine control system (or any control system).

Also, don't attach the welder ground/earth or perform welding directly on some field device or instrument directly connected to the turbine control system (or any control system!). If it's absolutely necessary to weld on a manifold or valve or flange where a pressure transmitter is also connected, or a piece of pipe or conduit connected to a pressure transmitter or thermocouple is mounted, temporarily disconnect the field device or instrument from the control system while the welding is being performed--but also, connect the welder ground/earth lead as close to the area where the welding will be done.

Any turbine control system (any control system!) should be properly grounded with suitably sized conductors. But, they are not sufficient for welding purposes under any circumstances, so to minimize the possibility of any current traveling through the control system it's always recommended to place the welder ground/earth lead as close to the area to be welded as possible, and to temporarily disconnect any field devices or instruments which are extremely close to the welding area especially if the welder ground/earth lead can't be connected close to the welding area.

Normal precautions when welding on or near bearings of any kind should also be observed when welding "near" gas turbines.

Hope this helps!
 
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vinayak_paranjape

We carry out welding only after switching OFF MARK V during shutdown that too with precautions as mentioned in the previous post.
 
Laser weld beads are narrow and well defined. This makes laser welding particularly suitable for near-net-shape build-up welding: very large, complexly shaped sections can be rebuilt without the need of shaping tools.
 
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