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To add to Bob Johnston's excellent description, I've looked at the sequencing of several units and some used L3 as part of the permissive string for closing L20CB1X and some used L14HS. Here is a <b>typical</b> rung for most of the sequencing I reviewed:<pre> L52GX1 L4 L14HS...

The only time I've every heard of "core engine" is when the Mark VI was used in a unique aero-derivative control system called the "Millennium" control system. I believe the core fuel control functions (probably including speed control and load control and start-up/shutdown fuel control and some...

Dan Griffin, Thanks for the feedback. This is one of the few "faults" of the Mark IV. In the first implementation of TMR each processor had dedicated exhaust thermocouples and did not know what the other processors believed the average exhaust temperature was. (This was solved in the Mark V...

This must be a very old Frame 6, as I've never seen one with un-modulated IGVs. I would have to review the Piping Schematics (P&IDs) and the sequencing in the control system to understand when the IGVs move from closed to open, and if there was any intermediate position. From this latest...

You may be using natural gas, but the same can still occur if the temperature is at or only slightly above the dew point temperature. Whatever those liquids are (and it would be good to have them tested to see what they are--just plain water, or what--I've seen lube oil (from compressors)...

It would seem that what's missing here is an understanding of what a loop isolator does. It "isolates" the analog card electronics from the electronics of the field device, usually to prevent multiple ground loops from adversely affecting one or both of the ends of the loop (the analog card and...

Well, this is very interesting. I'm looking at a Mark IV+ Speedtronic Elementary for a Frame 6B unit, and it only "rejects" thermocouples <b>less than</b> a certain value--and <b>only</b> for calculating the average exhaust temperature. I remember that some early Mark IVs used on some Frame 5s...

Ayman, When you post to a site like this, you need to provide much more information in order to get a more concise response. For example, you said the unit is a Frame 5, but is it driving a generator or a compressor or pump? In other words, is it a generator drive unit or a mechanical drive...

JiM, The setpoints are Control Constant values, in other word they are "fixed" they are not calculated like TTRF is. TTRF is calculated from a number of parameters, including axial compressor inlet temperature, compressor discharge pressure, I believe ambient (barometric) pressure is also...

GRJS, Thanks for the feedback and information. While it's conceivable that the Hydraulic Pump could be running on the edge of its curve, most of the pumps I have seen used for hydraulic supply on GE-design heavy duty gas turbines have been positive displacement pumps. These pumps are...

ashiq, We don't get too many Siemens-related posts here on control.com. I think most are unfamiliar with the terms used in Siemens control systems, and possibly with the types of actuators and the inputs to the references and feedbacks from the IGVs that might be causing problems with the...

I was always taught that to derive the polarization index of a motor or generator to use 500 VDC for devices rated at approximately 500 V or less, and 1000 VDC for devices rated over 500 V. Also, motor-driven meggars are typically specified for use in deriving polarization index values. I am...

Oluwafemi Ogundaisi, I don't understand "with several thermocouples rejected." What control system is being used for this unit? What do you mean by "rejected thermocouples"? There were older GE control systems (Mark II and earlier) that used a method of rejecting thermocouples that I've seen...

This is not directly about my dream. It's about the dreams of people who want to become competent and confident in their knowledge of GE-design heavy duty gas turbine operation and Speedtronic control systems. While there is a lot to be learned from the information available in the manuals...

IrishAl_0, It's presumed you have meggared the wiring between the Mark VI TBCI terminals and the switch contacts, and between any intermediate junction boxes, looking for any possible source of high resistance between the Mark VI input terminals and the switches themselves. The worst...

Hello! Yes; TTRF (Turbine Temperature-Reference, Firing) is a calculated value which is compared to various setpoints to determine when to change combustion modes. These temperatures occur at roughly identical loads, hence the 75-80 MW range you referred to. If combustion mode switching...

I'm not really familiar with these old ratchet mechanisms that don't use the self-sequencer, but I believe there is still an alarm that would be generated if the unit did not "see" a ratchet stroke after a couple of cycles had expired. The alarm message is something like "Hydraulic Ratchet...

A UCVx is like a PC, it has a microprocessor and it has non-volatile memory and it requires an operating system to be downloaded to it in order to be able to schedule and execute the tasks in the application code. At least that's the way I understand Mark VI control systems. It's like having...

<b>From the information provided</b> (and I'm not exactly clear on the whole problem/sequence of events here), it would appear that <S> is calculating a completely different IGV reference position (CSRGV, Control Stroke-Reference, Guide Vane). From what you're saying, it appears the IGV LVDT...