Few days back one of our Frame-9E machine tripped on loss of flame. Before trip, flame # 3 & 4 were reading 0 count. We have noticed flame detector # 4 cable damaged, it was replaced along with new flame detector. TCEA card replaced as 330 V from Mark V was missing.

Now unit is running normal with stable flame intensity. BUT still we are not clear why the cable damaged and 330 V was missing? If any one having experience please share with us.

Take care
G.Rajesh

 

G.Rajesh,

You didn't say specifically how the #4 flame detector wire (cable) was damaged, or where along it's length it was damaged. As long as they are protected from the heat of the turbine compartment, usually, they last for the life of the turbine--it's usually melted insulation or cracked insulation (from excessive heat) that causes the failures of these twisted, shielded pair cables.

I believe if you look in the Signal Flow Diagrams in Appendix D of the Mark V Application Manual, GEH-5980, you will find that the three TCEA cards all feed the TCEB card, and the flame detector power supply voltages are diode-selected so the loss of a single TCEA won't result in the loss of any flame detector signals. So, it's odd that replacing on TCEA restored the 335 VDC....

 

Thank you CSA,

We too not sure how it damaged, it damaged on the molded part. We have noticed black sign of smoke. We have replaced three TCEA cards to restore 355 V DC. For us too it surprise how 3 will damage same time. This maching is having some ground issues and frequent cable damage at gas compartment where servo valve, LVDT's, pressure transmitters are connected. Earlier bleed valve open while running due to ground issue.

take care
G.rajesh

 

Hi Rajesh,

Is there any mark or sign of abrasion on the cable? If there is, then it is very logical that the exposed conductor grounded the 335V from all TCEAs, causing surge of current and thus damaging the flyback circuit on them.

I sometimes come across such problem at sites, as the instrument is poorly handled by unskilled. technicians. Or you might need to check the conduit where the cable is installed.

You might also be interested to check out the metal protective conduit offered in this website
that will prevent any such recurrence. I've heard their product quality is very good.

http://www.flamescanner.net/products/flame-scanner-accessory-parts

Hope it helps.
Kevin

 

Hi Kevin,

Yes there is a black burned sign on the molded part. Thank you very much for the link which is having more details about the flame detector products.

take care
g.rajesh