Sorry for typo, it is Mark VIe. And we have Cimplicity 6.1, so TDC talks with master-slave modbus configuration (I am going to ask some questions regarding this to somebody or Process Value, as time permits). I was busy digging constants for gain and offset so i was late in replying, we have two fuels NG and C4 we can start on any fuel (F7-E). Here are the constants

IN Mark IV (previously control mode)
For NG " FPKGNG = 2.88 AND FPKGNO = -25.4
For C4 " FPKGN2G = 2.963 AND FPKGN2O = -25

And Mark VIe:
FPKGNO = -25 AND FPKGNG = 2.963 (Nat Gas)
FPKGNG2 = 2.963 AND FPKGNO2 = -25 (C4)

Please note signal names are changed but description says offset and gain, and they are same for both fuels on Mark VIe. If we put these values in formula with TNH, results are low P2 pressure. But with RPM it follows correctly. Last Saturday we started one of the unit after water wash, and I watched the flame, after ramping down from purge till about 8 % of the speed, GT started ramping up and at 10 % of the speed firing timer (60 secs) came in I got the flame (2) @ 10.4 to 10.6 %. Please correct me if I am missing something here. As you mentioned I have to start somewhere, I appreciate yours and everybody's help in this forum. Some questions may be silly for some one, but for me it may be like rocket science

Thanks

 

sardar9,

Why do you say:

>If we put these values in formula
>with TNH, results are low P2 pressure.
>But with RPM it follows correctly.

Please tell us where you obtained this formula with 0.08 as the gain. And where you obtained the -25 value you are citing as the Offset.

If we use the FPKGNG and FPKGNO values you cited, the P2 pressure at 100% speed would be:

FPRG = (100 * 2.963) - 25 = 296.3 - 25 = 271.3 psig

And, if we put the firing speed (10%) in for firing P2 pressure, the result would be:

FPRG = (10 * 2.963) - 25 = 29.63 - 25 = 4.63 psig.

Now, 4.63 psig seems very low. <b>Only YOU can observe the P2 pressure reference while firing and while operating at 100% speed and tell us if the numbers are correct.</b> Please do so--tell us what the P2 pressure references are at 100% speed and at 10% speed.

If those values of FPKGNG and FPKGNO are correct, and the P2 pressure references as listed above prove to be correct (from the Mark VIe), then your site would be unusual in that the P2 pressure reference at firing would be unusually low, but if it works at your site, then that's good! We can't know how the fuel nozzles are sized at your site, nor what the fuel characteristics are, nor if the fuel flows through the same gas fuel nozzle or through different nozzles. There's a lot we don't, and can't, know. But, if it works, that's good for you.

But, as otised and I have said, we have never seen a P2 pressure reference like the one you have cited, using RPM instead of TNH.

 

> Now, 4.63 psig seems very low. <b>Only YOU can observe the P2 pressure
> reference while firing and while operating at 100% speed and tell us if
> the numbers are correct.</b> Please do so--tell us what the P2 pressure
> references are at 100% speed and at 10% speed.

Hello Sirs,
I was watching the relationship between RPM and P2 pressure as unit was coming down for water wash, here are the actual readings taken at different RPM and corresponding P2 (real time)<pre>
RPM Reqd P2(0.08*RPM-25) Actual P2
2480 173.4 176
2443 170.44 170
2280 157.4 157
2107 143.56 143
1855 123.4 123</pre>
Hopefully these readings are related this way, if I am wrong please correct me, I am still digging info on topology at my plant soon I will be have lot of questions for all the gurus there. I just started reading on this forum may be for last three months or so, Believe me the knowledge I gathered can not be described in my words. Excellent jobs by everybody there. I spent at least 5 to 6 hours everyday on this forum.

Thanks again. When I reviewed the format of the above table it was confusing, For your info first four digits are RPM and last three digits are actual P2 pressure from M6e and all the middle digits are calculated as {( 0.08*rpm)-25} giving us calculated value of P2, this can be compared to actual p2 value ( last three digits).

Thanks
sardar9

 

sardar9,

From a previous post you said that the Mark IV Control Constants FPKGNG and FPKGNO were 2.88 <b>PSI/%</b> and -25.4 <b>PSI</b>.

If the data from the first column of your most recent post is converted to % TNH, and the data from the third column are used, then FPKGNG are FPKGNO are calculated to be approximately 2.870 <b>PSI/%</b> and -24.78 <b>PSI</b>, respectively.

<b>You</b> choose to use (insist on using, rather) a formula with values that relate RPM and P2 pressure, with values 0.08 <b>PSI/RPM</b> and -25 <b>RPM</b>.

<b>The Mark IV</b> (and <b>ALL</b> Speedtronic panels, including the Mark VIe) uses a formula with values that relate TNH and P2 pressure.

TNH for the machines at your site is equal to (RPM/36). It's <b>VERY</b> interesting to note that if you multiply 0.08 PSI/RPM by (RPM/36) which is the formula for TNH you obtain the value 2.88 PSI/%, where % refers to %TNH. And FPKGNG, per your previous post, is 2.88 PSI/% for the Mark IV, and is not that much different from 2.963 (the Mark VIe value you listed).

The two formulae are virtually identical, just that the one you choose to use (insist on using) relates P2 pressure to RPM, and the Mark VIe uses (and ALL Speedtronic panels use) a formula that relates P2 to TNH (which is (RPM/36 at your site)).

You can use whatever formula you like; the Mark VIe uses (and all Speedtronic panels use), and will continue to use (and all Speedtronic panels will continue to use), the formula that relates P2 pressure reference to TNH using the formula previously stated.

While both of these formula using values with different units yield a seemingly low P2 pressure reference at firing speed, it seems to work for the units at your site. That may be because of the dual gas fuels at your site. There's nothing that says the P2 pressure at firing needs to be a certain value or in a certain range; the required P2 pressure reference is a function of the equipment (fuel nozzles and control valves) and the fuel characteristics at a site.

So, the upshot of this is that your formula using RPM works relatively well for the calculation of P2 pressure reference; it's just that the Speedtronic panels use values with different units in a similar formula.

 

I really shouldn't be allowed to proof-read my own writing.

There's a mistake in the sentence paragraph below; it was originally written:

><b>You</b> choose to use (insist on
>using, rather) a formula with values
>that relate RPM and P2 pressure, with
>values 0.08 <b>PSI/RPM</b> and -25
><b>RPM</b>.

It should have been written:

<b>You</b> choose to use (insist on using, rather) a formula with values that relate RPM and P2 pressure, with values 0.08 <b>PSI/RPM</b> and -25 <b>PSI</b>.

Again, sorry for any confusion. The units for the offset (the second value) should have been PSI, not RPM.