Dear CSA

We have newly upgrade our frame-III gas turbine control panel from MK-II to MKVIe. We used to simulate Servo valve calibration and function checking when required on MK-II. Hydraulic/control oil solenoid dump valve (20HD) need to be energized for above activity. How we can energized 20HD in MKVIe control ST? please elaborate.

 

Haroon,

Congratulations!

It's very likely there is a logic signal name something like l20hd1, or l20hd1x. (Lower-case signal names are supposed to indicate an input or output of the Mark VIe--when they are correctly named).

You will likely need to force l20hd1 (or l20hd1x) to a logic "1" in order to be able to energize 20HD.

You may also need to force L4_XTP to a logic "0" (it's the inverse of L4) at the same time, in order to get both sides of the 125 VDC supply to 20HD.

There should be an "elementary" diagram (schematic drawing) provided with the Mark VIe which can be used to find 20HD and determine exactly what signals need to be forced in order to get +/- 125 VDC power to the "solenoid." (It's useful to know that some older turbines did NOT use and actual solenoid coil for 20HD; rather they used an electro-hydraulic servo-valve instead as 20HD. If this is the case, it's likely the Mark VIe includes a special solenoid output terminal board such devices were connected to--unfortunately I can't recall the name of that terminal board at this writing.)

I hope this helps! Please write back to let us know how you fare!

 

Thanks Dear CSA;

That is absolutely the correct procedure as you mentioned by forcing two signals (l20hd1x and L4_XTP), still 20HD could not energized.
It seems that signal are properly changing but 125VDc voltages not appeared on Solenoid and hence no voltage on terminals of solenoid.
I further investigated and observed that "ComposTrip1" signal is "true", is that can lead any problem for 20HD energization?? what is actually function of this signal?

again thanks for your earlier reply...

 

Haroon,

ComposTrips come from the PPROs. Something in the E-Stop P/B circuit, or one of the discrete trip inputs to the SPROs/TPROs is open. I've seen this happen when the panel is a SIMPLEX panel and they wire trip inputs like something from the fire protection to the <P> cards. BUT, there should be a Process Alarm to tell you which input is open.

Is this a SIMPLEX control system? What other Process Alarms are annunciated and active?

 

Haroon,

When I make recommendations about procedures, they always presume there are no active trips. I guess I need to be stating that clearly from now on.

And, as much as I intensely dislike--and I do INTENSELY DISLIKE it--asking if you've tried clicking on 'Master Reset', have you initiated a 'Master Reset' to see if that clears the ComposTripn signal? Any ComposTripn signal that's enabled in ToolboxST and is active will prevent the protective relays (driven by the SPROs/PPROs) from picking up. I've seen grounds cause ComposTripn signals to be active for a brief time; I've seen induced electrical noise (on the E-Stop P/B wiring circuit) cause ComposTripn signals to be active. They are a very nebulous group of trip signals, and, not very well defined (meaning that sometimes the conditions seem to change with changes in product code--the files that get downloaded as the "operating system" to the SPROs/PPROs).

 

Thanks for your remarks.

That's true we have Simplex Control system with R/S controller, single PTUR and Three PPRO I/O packs. (That's about our system)

Further there is not any process or other trip signal available also machine ready to start appeared when all checks normalized. While forcing l20hd1x signal (relay signal at PTUR Kq1 goes ON), however by forcing L4_XTP no change on PPRO card. PPRO card status remains as mentioned below.

PPRO LED STATUS:. RUN LED is RED soild, other LED are green by forcing or releasing L4_XTP signal.

 

Haroon,

Actually you have a [Semi] DUAL redundant system, which is a hybrid SIMPLEX system.

When a turbine is at zero speed, if I recall correctly the RUN LED is red, and that's because the PPRO isn't seeing any speed. So, that shouldn't be a problem (presuming the unit is at zero speed!).

If I recall correctly, l20hd1x (when a logic "1") applies +65 VDC to 20HD-1, and when there are no trips on the PPROs and L4_XTP is a logic "0" the emergency trip relays apply -65 VDC to 20HD-1. So, if you measure the voltage at 20HD-1 when l20hd1x is a logic "1" and you measure +65 VDC (with respect to ground), and then you unforce l20hd1x and for L4_XTP to a logic "0" you should measure +65 VDC with respect to ground at 20HD-1. That's if the PPROs are picking up the emergency trip relays. If you measure nothing at 20HD-1 when L4_XTP is a logic "0", and you don't hear any relays clicking in the control panel when you force L4_XTP to a logic "0", then something is not allowing the PPROs to pick up the emergency trip relays.

I've seen a LOT of START CHECK and TRIP displays not configured properly--meaning they don't accurately depict all of the start-checks or all of the trips. And, if I recall correctly (I don't have access to a Mark VIe System Guide, GEH-6721, at this writing) there are at least seven possible trip inputs to the PPRO terminal board(s) that can trip the turbine on a SIMPLEX/[Semi]DUAL system, and those contacts all have to be closed to allow the emergency trip relays to be picked up when L4_XTP is a logic "0". Any of those seven inputs which are used are supposed to have Process Alarm messages associated with them to tell the user when the input is abnormal (such as low-low L.O. pressure; or, say in the case of a two-shaft compressor drive unit, a low-low compressor seal oil pressure; or, if the unit exhausts into an HRSG a low-low or high-high boiler drum level).

Sorry, but without being able to see the application code and configuration in ToolboxST it's very difficult to say. And, again, the E-Stop P/Bs all have to be in the "run" position--every one of them. I know some sites that use them as part of their LOTO (Lock Out/Tag Out) procedure, locking them into the "trip" position, thinking that that will just prevent a START, when it has an impact on other controls-related work, too.

Please write back to let us know what you find!

 

Thanks and I really appreciate your responses.

I want to share you that we have 03 nos. MKVIe control panel and we always experienced that 20HD energized by forcing L4_XTP and l20hd1x signals, this was first time we faced such problem that said procedure did not worked. (surely due to Compostrip1 signal, but we did not noticed before truly speaking).

Now, I have very much interesting points which I want to share with you. First, there was't any process trip alarm and we also used to "Master reset" and "diagnostic reset" as and when required. Although, We could not energized 20HD solenoid manually however, our unit started successfully.

After a long exercise we could not get the actual cause of "Compostrip1" as no diagnostic or trip signal was appearing.
Further, I checked voltages across 20HD as you mentioned above. I found -55Vdc w.r.t ground when l20hd1x signal energized and clearly heard sound, but no voltages observed either forcing or un-forcing L4_XTP signal.

Again Thanks very much and really I found this forum very much informative and relative...

See you with new discussions in future..

 

Haroon,

Thank you for the feedback!

The next time that happens, try rebooting the PPROs. The unit is off-line anyway, so it can't trip the unit.

My best presumption is that something happened with turbine speed inputs to the PPROs during shutdown; that is a two-shaft machine and sometimes the PPROs get a little confused at part speed. Don't know why, but it's been known to happen--unfortunately.

Again, thanks for the feedback. It was definitely not getting +65 VDC from the ETRs (Emergency Trip Relays).