I know LOTO has to be a site specific thing, many places have their own ways of doing things. But as procedures change, I've been asked to look at the components with which we isolate for turbine maintenance. Looking at them, I'm a little confused why they chose some of the ones that they did. In the past we have isolated the following components:

Natural gas inlet and vent
Fuel oil Inlet
CO2 isolation and vent valves
Fire protection panel breaker in 1DG
Fans and blowers: 88BT-1, 88VG-1, 88TK-1, 88TK-2, 88QV-1, 88BQ-1
Pumps: 88QA, 88HQ, 88QE-1
Motors: 88HR-1, 88DS-1
Heaters: 23QT
Breaker: 52-G
These all seem okay.

Then there are the ones that look like they could use a little help:

<PDM> Fuse FU-7 (De-energize 45FT sensors)
<PDM> Fuse FU-23 (De-energize Ignitors)

and JC plug at FD1 and FD2 from AIO.1

I don't like using the plugs, so I looked upstream and it seems I could pull FU4 and FU5 at the PDM to do the same job. Is there a downside?

Finally this leads me to ask why wouldn't one want to de-energize relay modules, AIO, CIMs, etc.?

It's just been this way so long. Do most people just open the breaker to the Mark IV and be done with it?

Or is the risk of powering down and later up these old electronics high enough to warrant leaving the computers up?

 

cactus_chris,

Why do you not like unplugging cables with pluggable connectors?

 

All the outage we made, and are already a few, have always extracted the connector, we have not had any problems. As a visible isolation, when do Walkdown with TE GE warranties as to have the spark plugs LOTO placed.

Failure to remove the H2 generator and not have to work in the load compartment area, do not stop the 88VG.

 

cactus_chris,

I don't have access to any Mark IV elementaries at this writing, and I don't recall what kind of connectors are involved at the AIO terminal boards (I presume that's where you're talking about unplugging and plugging-in cables). If I recall correctly, the outputs of the flame detector modules were connected to one of the AIO modules (AIO.1 I think it was), and that was essentially 28 VDC. So, removing these cables (if they're the ones you're referring to) won't remove the 335 VDC power output of the flame detector modules to the flame detectors. I think some of the Mark IVs used 125 VDC from one of the relay modules (Relay Module 1, if I recall correctly) to power the flame detector modules--but it's been a VERY long time and I don't recall exactly.

I was thinking were describing a simple two- or four pin cable plug using 16-ga. twisted, shielded pairs connecting the discrete outputs of the flame detector modules to the Mark IV circuitry--but it's not clear from your post if you're trying to isolate the flame detector power supply--and thereby remove the 335 VDC output to the flame detectors--or the discrete outputs of the flame detectors to the Mark IV circuitry. So, depending on the type of cable/connector I can understand the reluctance.

Also, if it's possible to isolate the power to the flame detector modules by removing fuses in the <PDM>, then as one is already removing fuses to isolate other components in the Mark IV then it would seem reasonable to just remove the fuses for the flame detector modules at the same time. Again, I don't have any elementaries to refer to to remind me if the 125 VDC for the flame detector power supplies is supplied directly from a pair of fuses in the <PDM>, or if the fuses also supplied power to other circuits.

I can tell you this from VERY painful experience--there are small relays on the Mark IV processor power supplies that control the removal/application of crowbar circuits to protect the power supplies, and the physical elements of the relays can sometimes stick in the position that continuously applies the crowbar which will continuously blow fuses, eventually resulting in the destruction of other power supply components. So, powering them down and re-powering them can be costly in terms of hardware, production and your sanity.

You mentioned removing the power to the 45FT fire detectors; I presume you're referring to the entire fire detection and extinguishing agent discharge circuitry.?.?.? Most Mark IVs for GE-design Frame 6B heavy duty gas turbines used two dedicated relays and special circuitry of the Mark IV to detect fire in the Accessory-, Turbine- and Load Compartments; trip the turbine; and discharge extinguishing agent (CO2, or Halon). It's very common for the Fenwal temperature switches to be very easily damaged during mechanical work in the compartments, resulting in 125 VDC battery grounds (earths). Also, sometimes it's necessary to remove the fire detectors for some maintenance activity, so the circuits must be de-energized. Finally, since the same circuitry is typically used for energizing the discharge solenoids on the extinguishing agents it's always advised to remove the power to the fire detection/discharge circuitry. If high-pressure CO2 cylinders are used for the extinguishing agent, it's easy to damage the discharge solenoid coils if left energized for hours/days at a time, which can unintentionally happen during maintenance work--resulting in a system that won't work when needed!

As for the other fuses/circuits, without elementaries I can't be of too much help. Also, many sites used unused "spare" fuses in the <PDM> for extra circuits/purposes, so without being able to see the elementaries for your site and know what all the fuses are used for it's impossible to offer an opinion on those fuses/circuits.

Hope this helps!

 

Hi,

Wanted to kow if you by any chance want any Mark IV cards?

Regards,
Briha

 

> Why do you not like unplugging cables with pluggable connectors?

Our new policy requires locks, and if locks and devices can not be used we have to consider additional means of full individual protection before placing a tag only. So, it's not that I don't like it, its more of a due-diligence thing.

 

Understood.

 

> I don't have access to any Mark IV elementaries at this
> writing, and I don't recall what kind of connectors are
> involved at the AIO terminal boards (I presume that's where
> you're talking about unplugging and plugging-in cables).

I've looked at the elementary and the max case, and it really looks like the only wires to these flame detector modules are 28V, COM, CH.1(3), CH.2(4) coming from RELAY 1 via AIO.1. and the connections to the scanners, as you mentioned.

Link to image(s)

ELEMENTARY
http://imageshack.com/a/img907/1520/7yU3Mg.jpg 39B FLAME DETECTION

MAX CASE
http://imageshack.com/a/img905/995/tewfnj.jpg 29A <PDM>
http://imageshack.com/a/img907/3757/lPInVw.jpg 02A <RELAY 1>
http://imageshack.com/a/img903/1107/GZv8TT.jpg 03D <AIO.1>
http://imageshack.com/a/img905/2141/TvDMSV.jpg 24A <FD1>

>I was thinking were describing a simple two- or four pin
>cable plug using 16-ga. twisted, shielded pairs connecting
>the discrete outputs of the flame detector modules to the
>Mark IV circuitry--but it's not clear from your post if
>you're trying to isolate the flame detector power
>supply--and thereby remove the 335 VDC output to the flame
>detectors--or the discrete outputs of the flame detectors to
>the Mark IV circuitry. So, depending on the type of
>cable/connector I can understand the reluctance.

I'm pretty sure that we've been removing the plug from AIO to FD1,2

>Also, if it's possible to isolate the power to the flame
>detector modules by removing fuses in the <PDM>, then as one
>is already removing fuses to isolate other components in the
>Mark IV then it would seem reasonable to just remove the
>fuses for the flame detector modules at the same time.
>Again, I don't have any elementaries to refer to to remind
>me if the 125 VDC for the flame detector power supplies is
>supplied directly from a pair of fuses in the <PDM>, or if
>the fuses also supplied power to other circuits.

These are the <PDM> fuses for our installation:<pre>
FU-2 < PS REL 1 > P28VR
FU-3 < PS REL 2 > P28VR

FU-4 <RELAY 1 > 125P1/125N1 (VOTING)
FU-5 <RELAY 1 > 125P2/125N2 (NON-VOTING)

FU-6 FIELD POWER - NOT USED
FU-7 FIELD POWER - FIRE PROTECTION - 16A (45FTX)
FU-8 FIELD POWER - NOT USED

FU-9 < PS.R >
FU-10 < PS.S >
FU-11 < PS.T >
FU-12 < PS.C >
FU-13 SPARE
FU-14 SPARE

FU-15 < CIM .1 through CIM.6 >
FU-16 NOT USED
FU-17 NOT USED
FU-18 NOT USED
FU-19 < CIM.6 >

FU-20 DOOR SWITCH, INTERNAL LIGHTS
FU-21 PRINTER
FU-22 CRT

FU-23 IGNITION TRANSFORMERS</pre>
So, it looks like, according to the above image(s), that <PDM> FU-2 and FU-3 de-energize <PS REL 1> and <PS REL 2> who's 28V outputs are auctioneered in <RELAY 1> (P28VR) and passed to, among other recipients, < AIO.1 > (CR#362) which passes the 28V from JA to JBA and JBB the connectors to < FD 1 > and < FD 2 > which also contains the analog wire for each detector (2 per connector).

>I can tell you this from VERY painful experience--there are
>small relays on the Mark IV processor power supplies that
>control the removal/application of crowbar circuits to
>protect the power supplies, and the physical elements of the
>relays can sometimes stick in the position that continuously
>applies the crowbar which will continuously blow fuses,
>eventually resulting in the destruction of other power
>supply components. So, powering them down and re-powering
>them can be costly in terms of hardware, production and your
>sanity.

So to be sure, will this stuck crowbar cause problems when applying power to the power supply? Or is it something that only happens when powering up via the ON-OFF switch? If it happens when applying power to the input of the power supply, that would seem to be a pretty good reliability based reason for continuing to remove the plug.

***Otherwise, what would be the harm in removing Fuses 2-5,7,15,19 and 23?

>You mentioned removing the power to the 45FT fire detectors;
>I presume you're referring to the entire fire detection and
>extinguishing agent discharge circuitry.?.?.? Most Mark IVs
>for GE-design Frame 6B heavy duty gas turbines used two
>dedicated relays and special circuitry of the Mark IV to
>detect fire in the Accessory-, Turbine- and Load
>Compartments; trip the turbine; and discharge extinguishing
>agent (CO2, or Halon). It's very common for the Fenwal
>temperature switches to be very easily damaged during
>mechanical work in the compartments, resulting in 125 VDC
>battery grounds (earths). Also, sometimes it's necessary to
>remove the fire detectors for some maintenance activity, so
>the circuits must be de-energized. Finally, since the same
>circuitry is typically used for energizing the discharge
>solenoids on the extinguishing agents it's always advised to
>remove the power to the fire detection/discharge circuitry.
>If high-pressure CO2 cylinders are used for the
>extinguishing agent, it's easy to damage the discharge
>solenoid coils if left energized for hours/days at a time,
>which can unintentionally happen during maintenance
>work--resulting in a system that won't work when needed!

Yes, FU-7 removes power from that whole circuit.

>As for the other fuses/circuits, without elementaries I
>can't be of too much help. Also, many sites used unused
>"spare" fuses in the <PDM> for extra circuits/purposes, so
>without being able to see the elementaries for your site and
>know what all the fuses are used for it's impossible to
>offer an opinion on those fuses/circuits.
>
>Hope this helps!

As always, yes, and thank you!

 

Hi,

>Wanted to kow if you by any chance want any Mark IV cards?

I've got a spare Mark 4 cabinet spilling over with cards. I just don't know what shape they're in. It would really help if I knew which one I am going to need next I'd send that one out.

 

Hi Briha,

I am interested in these spares. Could you please share your mail ID so that I can contact you in private

Regards...
Samson16