GE/NP's Std Practice

Frame V Turbines - MARK VDec 3, 2005 7:26 pm, by Rahul P SharmaSubject : Applications from the Instrumentation & Control dept.

Hello, We have three set of Frame V turbines... Two are MARK II Speedtronic controls and the third one is MARK V control... We are planning to upgrade the MARK IIs to MARK V now... The question is that in older turbines we did not have any proximity vibration sensors.... Only Casing vibrations were measured and recorded, using velometers.... In the newer machine we do have Bently Nevada's Proximity sensors installed BUT without Key Phasor probe and required PC interface, thereby making the system of little use.... The local supplier says that GE doesnt recommend proximity sensors for Vibration Monitoring... Only casing vibration is used for tripping the Machine... Is it right...?? Secondly, given this status and lack of clarity, should we ask for a new Bently Nevada's complete vibration monitoring system installed with the upgrade that we are planning...?? If yes, then how will the modifications for the Proximity sensor installations take place...?? If I am right, to install proximity probes the bearings should be drilled so that the tip of the proximity probe can be as close to the rotor as possible...!!!! And two such mounting arrangement will have to be made 90 degrees apart... Thanks and regards Rahul

Re: Frame V Turbines - MARK VDec 4, 2005 3:36 pm, by markvguy
It's true--GE still relies on the "seismic" vibration transducers for protecting even new turbines, including Frame 7Fxs (which also use B-N vibration monitors, but not generally for protection/tripping). You are correct; modifications will most likely have to be made to the bearings/bearing shells for installation of the proximity probes. It's a trade-off--if you've had vibration problems in the past, or need the additional vibration monitoring ability (for balancing), then the cost and scope of the modifications must be taken into account. Newer Mk V turbine control panels have the ability to accomodate proximity probes and possibly even key phasor inputs and the operator interfaces can perform vibration analysis with the information.

Re: Frame V Turbines - MARK VDec 6, 2005 9:55 pm, by Rahul
Thanks for the info... But I have a question... Is there a document somewhere, published by GE, that could be relied upon to convince the authorities here that even if Proximity Probes are not used it will not be detrimental to the functioning of the Machine and that only Seismic transducers are all what's needed for ensuring the safety of the machine... Thanks again, au revoir Rahul

Re: Frame V Turbines - MARK VDec 7, 2005 11:51 pm, by Joe Clappis
By virtue of the fact that GE has relied for decades on seismic vibration probes for unit protection for new units under warranty--and continues to rely on seismic vibration probes for unit protection for new units under warranty--should speak volumes for the safety of their application and use. B-N proximity probes have been known to have their own "ghost" problems, falsely indicating high vibration because of problems with melted/damaged prox cables and interconnecting wiring (i.e., usually because improper shield grounding practices and signal isolation not strictly adhered to). The big advantage to B-N probes is the ability to analyze pinpoint the problem quickly and apply a balance shot when necessary.

Re: Frame V Turbines - MARK VDec 7, 2005 12:54 am, by Joe ClappisBy the way, are you still able to obtain Mk V controls from GE? If not, can you provide the information about where to obtain Mk V panels and engineering/commissioning support for retrofit applications?