Machine underwent Major Overhaul. Control System is Mark VIe. Electronic simulation tests for HP overspeed were successfully done. As per OEM recommendations, HP Overspeed Bolt Test is not mandatory to avoid Machine Overstress.

Actual Electronic Overspeed Test also was NOT Successful as machine tripped 100 rpm before the test level during test and OEM recommends to put the machine in operation without doing it again.

What are the Overspeed tests mandatory after Major Overhaul?

 

Which Electronic Overspeed Test was not successful? The Mark VIe has the capability for two electronic overspeeds: One is performed in the control processors (<R>, <S>, and <T>) and is considered to be the primary electrical overspeed, and the other is performed in the <P> (SPROs or PPROs depending on the configuration) and is called the emergency electrical overspeed.

Presuming the existence of two electrical overspeeds (primary and emergency), which overspeed tripped the turbine? It's common for GE to set the two to the same setpoint, but because the <P> operates at a faster scan rate than the control processors it usually trips first--but at the proper speed setpoint.

How was the data gathered--using the CIMPLICITY display or one of the Mark VIe data capture methods? The most reliable is the Mark VIe, NOT the CIMPLICITY. (Many people mistakenly consider the HMI to be the Mark VIe--it's NOT. It can be used for a variety of turbine control systems, not just the Mark VIe--and is only a means to view turbine operation, send commands, and manage alarms on a Mark VIe turbine control panel. The HMI doesn't actually do any turbine control--it's all done in the Speedtronic turbine control panel (whatever Mark it is). When configured with ToolboxST it can also be used to configure the Mark VIe turbine control panel and to trend data and view alarm and data capture buffers.

So, please be more specific when you say the "electronic overspeed test" was unsuccessful.

Is the turbine under warranty from the OEM? If so, they have responsibility for any actions they undertake. I have a very difficult time believing the OEM would casually say to overlook a test that was "unsuccessful."

The insurance company that insures the machine is the ultimate arbiter of what's required or "mandatory" and what's not. After that, the owner, or the owner's operating and maintenance crew can say what's required or mandatory. If the machine is under some kind of long-term service agreement then that company may also have some say in what is to be done or not. But, short of looking up tests in the API standards--which may or may not apply in your location in the world--there's really no "mandatory".

Except for that company that insures the equipment.

 

Reply: HP Electronic Overspeed Test was unsuccessful; machine tripped 60 rpm earlier than set value on other signal and not on HP Overspeed.
All readings / values were monitored on Tool Box ST, though Cimplicity is available as well.

Machine underwent Major Overhaul, not under warranty and in the process of start up tests. LP Overspeed Electronic Test was SUCCESSFUL.

Another question that props up is " Is HP / LP Overspeed Mechnical Bolt Test" not required to be done after Major Overhaul? We have been told that it is NOT REQUIRED to be done to avoid unnecessary machine Stress. Is it true?