Hello Control Team,
I recently installed a 1-5VDC Rosemount Pressure Transmitter on a GE MARK V control system for CPD,but the range of the signal on the MARK V is 0-5VDC. Is it possible and how can I re-range the 0-5VDC signal on the MARK V to 1-5VDC on the transmitter. The old transmitter is Rosemount 1151 the new one is Rosemount 2051

 

The Rosemount 2051 low power transmitter (Output Code M) has a 3 wire 1-5Vdc output.
The lower range output value, 1Vdc, is fixed, it cannot be ranged or shifted to zero.

Your range adjustment has to be on the controller/receiver end, where for example, a 0-2.0 bar output over 1-5Vdc would be ranged -0.5 to 2.0bar for a 0-5Vdc analog input (the LRV (zero) is a negative 25% of the total span at the receiver).

Or use a signal converter to convert 1-5Vdc to 0-5Vdc.

 

The Rosemount 2051 low power transmitter (Output Code M) has a 3 wire 1-5Vdc output.
The lower range output value, 1Vdc, is fixed, it cannot be ranged or shifted to zero.

Your range adjustment has to be on the controller/receiver end, where for example, a 0-2.0 bar output over 1-5Vdc would be ranged -0.5 to 2.0bar for a 0-5Vdc analog input (the LRV (zero) is a negative 25% of the total span at the receiver).

Or use a signal converter to convert 1-5Vdc to 0-5Vdc.

Yes , this is exactly what I want to achieve, Do you know how I can do it on a MARK V?

 

No, someone else will have to advise you on the specifics.

 

@Da

No, someone else will have to advise you on the specifics.

@David_2 Thanks for your assistance.

Anyone else with an idea on how to solve the problem.?

 

cheedee,

I DO NOT have access to any Mark V drawings at this writing (I may be able to get access next week, but there are no guarantees).

If I recall correctly, there is an Offset value (in Volts DC) and a Gain value (in Volts per PSIG, or PSIG per Volt DC--I can't recall exactly, but it should be clear in the I/O Configurator) in the I/O Configurator for the CPD input(s). And, the CPD input(s) are usually configured in either the DCC/SDCC or IOMA configuration display in the I/O Configurator. (HINT-HINT-HINT:You should WRITE DOWN the As-Found Values!!!)

And, if I recall correctly (and this may be detailed in the Mark V Application Manual, GEH-6195) the Mark V CPD input(s) can be any DC voltage value from 0-10 VDC, including 0-5 VDC and 1-5 VDC.

Set the Offset value to 1.000 VDC (sometimes, if I recall correctly it won't let you choose EXACTLY 1.000 VDC, but defaults to something like 1.0005 VDC--which is FINE!). For the gain value, let's say the transmitter is calibrated for 1-5 VDC equals 0-300 PSIG. That would be a range of 300 PSIG for a range of 4 VDC, which would equate to 75 PSIG per Volt DC, or 1 Vol DC per 75 PSIG.

Once you set the values in the I/O Configurator, you have to click on 'Verify Screen,' and if there are no purple vields then you have to "back out" of the I/O Configurator and 'Exit and Save Changes' when that target/button is available. (Remember: You should WRITE DOWN (have written down) the As-Found Values!!!)

Then you need to use the EEPROM Downloader to download the IOCFG partition to the EEPROM of <R>, <S> and <T>, one at a time. (It IS NOT necessary to a MK5MAKE or execute any compiler--the I/O Configurator files are saved in compiled format be default!) Once that is complete, you need to re-boot each of <R>, <S> and <T> ONE AT A TIME, waiting at least 1 minute after each re-booted processor returns to I/O State A7 before rebooting the next processor. (Re-boot the processors using the power switches in the <PDM>--NOT the white buttons on the DCC/SDCC cards.)

Then check to be sure the inputs are working properly (displaying 0 psig at 0 psig, 75 psig at 75 psig (if that's how your transmitter is scaled); etc.

Again, I don't have--and won't have for a few days at least--access to any Mark V documents/files. But, using the I/O Configurator and GEH-6195 you should be able to reason this through, save the necessary changes in the I/O Configurator (AFTER writing down the as-found values!), download the changes to the three control processors one at a time, and then re-boot the three control processors one at a time waiting at least 1 minute after the re-booted processor returns to I/O State A7, and then testing your changes.

Hope this helps!!! Please write back to let us know how this worked for you--and any changes you noted!

 

Thanks for the reply CSA!!! I am on it now. The unit has been started already, Is it possible to proceed with the configuration and restarting of the core while the unit is running?
Can this configuration be done for FPG2 (intervalve transmitters)?

 

cheedee,

”The book says....” you should be able to download to all three control processors (one at a time), and then re-boot each control processor one at a time waiting at least one minute between re-booting each processor, and starting with <T> processor then <S> then <R>. It is STRONGLY recommended to re-boot the processors with the unit running at between 25-50% load, as you may experience a load upset at higher loads when <S> comes back to I/O State A7. BUT if there are a lot of Diagnostic Alarms or Process Alarms before you begin re-booting then the chances of tripping the unit are much higher than if the Alarm windows are clearer.

Best of luck! Please write back to let us know how you fare.

 

cheedee,

”The book says....” you should be able to download to all three control processors (one at a time), and then re-boot each control processor one at a time waiting at least one minute between re-booting each processor, and starting with <T> processor then <S> then <R>. It is STRONGLY recommended to re-boot the processors with the unit running at between 25-50% load, as you may experience a load upset at higher loads when <S> comes back to I/O State A7. BUT if there are a lot of Diagnostic Alarms or Process Alarms before you begin re-booting then the chances of tripping the unit are much higher than if the Alarm windows are clearer.

Best of luck! Please write back to let us know how you fare.

Thanks for your replies CSA, I really appreciate them. On the unit, there are a bunch of DIAG and PRC alarms and I won't want to risk the trip.. . Once the unit is down I'll carry out the configuration and write back my observation.

Please a little question, can this 0-5V modification be for the Interstage fuel gas pressure transmitter?

 

cheedee,

Weather and holiday flyers are going to keep me from reaching home any time soon.... So, I don't have access to any Mark V files at this time. I believe something similar is possible for the P2 pressure transmitter inputs--BUT, the type of transmitters used for P2 pressure sensing SHOULD BE VERY FAST-RESPONDING. The transmitters GE uses are expensive not just because GE chose to use them or GE sells them, it's because they have a fast response rate (meaning the rate of change of the output signal is very close to the rate of change of the input pressure). Most sites want to change transmitters because they are expensive and many unknowing sellers offer much less expensive transmitters--without understanding the application requirements.
Many sites have replaced the GE-recommended transmitters and many have done so rather successfully. It really depends on several factors: the stability of the gas fuel supply pressure and flow, the stability of the grid frequency and load, and the condition of the gas valves, the type of combustion system (conventional or DLN) and the condition of the oil and servo-valves.
I also pointedly mentioned the number of Diagnostic- and Process Alarms.... Because while it should be possible to download and re-boot processors while the unit is running the presumption is that the number of active alarms is minimal and all of them are understood--and none of those things is true of most sites these days. And just recently I neglected to ask about the number and type of alarms when asked about on-line downloads and re-booting and received a VERY NASTY early morning phone call when the unit tripped and couldn't be quickly re-started. And, while it was never said I was to blame for the trip....
Please write back to let us know how you fare in resolving this issue.

 

@CSA, Merry Christmas . I hope you're having a wonderful holiday. Thanks for all your help. I replaced the 2051 transmitter for another unit, did the core reset and am glad to say it's working well!!.

 

cheedee,

Happy to hear the download and re-boot went well.

I am concerned about the value of gain shown in the photo you attached--but only because you never told how the new transmitter was scaled. I made an example of a transmitter scaled for 0-300 psig for 1-5 VDC resulting in a gain of 75 psi/volt--but, again, I don't think you ever said exactly how your new transmitter was calibrated/scaled for the 1-5 VDC output.

Anyway, thanks for the feedback!

 

cheedee,
What type of unit(s) do you have at your site?

CSA,
We have six 7EA DLN1 of 2001 vintage with MARK V's at our particular site. I noticed the value cheedee has for the "compressor stall detection disable" is set at 12.5, while our units have a value of 512. With a value of 512, stall detection will always be disabled. I brought this up to our engineers wondering if it was intentional by GE or if it was maybe an oversight. One of them checked the other units in the fleet (at different sites) and basically found that the 7EA's had a value of 512 and the 7FA's had a value of 12.5. He also checked the CSP and didn't find the alarm logic in any of the 7EA's while the 7FA's do have alarm logic. Is it safe to ASS-U-ME that the stall detection SHOULD be disabled on 7EA units? He did find two 7EA's that were set to 12.5, but these units were originally designed for use in Brazil (we're in the USA) and they were not commissioned by GE. There is no alarm logic for these two either. Do you know why this would be disabled on 7EA units?

 

RichT1,

Axial compressor stall detection was NOT deemed as critical to the B/E-class units (including Frame 5s, 6Bs and 7E/EA units) as it was for the Femme-class units (the F-class unit fleet). The B/E-class units all had LOTS of engineering- and safety margin built in to them, while (originally) the F-class units did not. (Further "improvements" to F-class axial compressor and inlet designs also proved to be somewhat questionable, but have gotten better.) Many B/E-class units were commissioned without axial compressor stall detection, even if they had DLN-1 combustion systems. It was never clear to me when, or why, axial compressor stall detection for B/E-class units was deemed to be configured as part of the standard factory default configuration; but, really, I think it was done in the interest of "standardization" and because some Safety Review (which often included lawyers) decided that if it was possible it should be included as a "standard" (more to provide cover in the event of lawsuits than any engineering reason). Another possible reason was because I think was it was deemed that more than one compressor discharge pressure transmitter was required for redundancy, and some B/E-class units (mostly those WITHOUT DLN combustors) only had a single CPD transmitter for many years, until that, too, became a standard (redundant CPD transmitters on all B/E-class units, even with conventional combustors--at least from Greenville; Belfort has always been extremely inconsistent (consistently so)).

Because many F-class units (and I'm including FA-class units, and FB-class units, and F.0n units) operate at IGV angles less than 54 DGA at low loads and FSNL compressor stall is a bigger problem than for B/E-class units which do not operate at IGV angles less than 57 DGA, typically, ever, except during starting and shutdown. These are not subtle differences, and, again, the B/E-class fleet has always had a very high engineering- and safety margin built in to the design of the units which made them more robust in many respects. Because of the requirements of DLN combustion systems, particularly, on F-class units--and the need for owners/operators to have high turn-down (get to as low loads as possible in low emissions mode) the IGVs had to be operated at what were--and still are--considered "low" angles, which puts the units at risk of stalling (and even surging) under certain conditions.

Finally, there were far too many commissioning personnel during The Bubble (late 1990's and early 2000's) that just took many liberties with configurations, copying things between units without knowing why or if it should be done. ("Can you spell Mark V? Close enough--go start one up!")

Is it safe to ASS-U-ME anything--especialy when it comes to GE-design heavy duty gas turbines? No; absolutely not. It would be interesting to know what GE's thoughts are on this, though by saying it should be enabled after it wasn't would help enrich their coffers with people scrambling to get it implemented on their units (paying to have it implemented). In my own personal opinion, it's not necessary for any "legacy" B/E-class unit (now some newer 9Es and the 9E-Max (kind of sounds like the 737MAX doesn't it?) should probably have it enabled, but as a rule for units which have been in service without any major mechanical upgrades or modifications it's probably overkill and just a nice-to-have.)

Hope this helps! It's rare to hear of a B/E-class unit experiencing stalling (or surging); but it's not such an uncommon occurrence on an F-class unit if it's not operated properly, or it's even slightly abused (which many are).