When unit reaches zero speed, FSRSD on <R> and <T>
ramp to 100%. FSRSD on <S> stays at zero. Voting
mismatch on FSRSD is captured on diagnostic alarm.
Unit is "Ready to Start". (Master reset will ramp FSRSD to 100% and next run always successful.) If master reset is not done, the next "start" results in a immediate "master protective start-up lockout" numerous voting mismatches on <S> the unit does start successfully and come on-line.

Have replaced relay 4S (4 times at the suggestion of others...), replaced HRDB board slot A of RDM (thought we had it pegged with that effort, but it tells us "sorry, please try again!")

Have examined pulse rates for turbine speed and fuel flow divider speed. (appear OK, definately have 0 RPM on fuel flow divider after fuel cut-out and zero speed on TNH at zero speed.)

This problem is only occurring on <S>.

and a recent "interesting" finding-> the above scenerio only occurs when unit is in "remote",
running unit locally in "Auto"... no problems!

Possibly 28 volt relays associated with "Remote"
(L43R1 or L43R2)?

Other possibilities?

Many Thanks!
Anon

 

The easiest way to troubleshoot this is using the Auxiliary Display to check the Process Alarms being annunciated by <S>.

This is one of the quirks of the Mk IV: One processor can detect and annunciate any number of process alarms, and nothing will be logged to the printer or appear on the Alarm Display--and only certain voted signals (like FSRSD) will be alarmed on the Diagnostic Alarm Display.

Hopefully all the digits of the Aux. Display work....most don't these days, and most sites haven't kept them working because they don't realize how useful (important) a trouble-shooting tool the Aux. Display can be.

Select the <S> processor and follow the instructions on the magnetic sign on the door above the <OPM> to get to the Alarm Display. It will only show Alarm Drop Numbers, and the latest Alarm Drop Number will appear first. Use the PREV and NEXT buttons (you probably have to hold the SHIFT button down while pressing the NEXT or PREV button) to scroll through the list of Alarm Drop Numbers. Then use the 18 sheets in the Speedtronic elementary to troubleshoot the alarm.

Something is not "cancelling" (disabling) the STOP command in <S>. That's another place you can look--all the logics that drive L94X--to find out what is different in <S> processor.

There is a logic signal which also controls the ramping of FSRSD which you can check and "work backwards" from.

As this author recalls, your site has a LOT of REMOTE logic....since it's operated remotely from quite a distance away....

Let us know what you find out!

markvguy

 

Hello mkivguy,

If our paths ever cross, I'm buying you supper at the "Prime and Wine"....

here's what we have found ( with much gratitude for your helpful direction )......

Root cause of "Master Protective Start up Lockout" upon a "start" command due to FSRSD not ramping up to 100% after unit reached zero speed from previous shutdown:

During the shutdown, fuel is reduced (FSRSD in
control), when fuel drops below 2.67 #/sec the Nox water system is disabled. Our <S> processor is seeing a slightly elevated fuel flow compared to the other 2 processors. <R>and <T> are seeing a slightly lower fuel flow and their 2 of 3 vote actually does turn the Nox water pump off. <S> believes the pump should still be running ..... detects the low discharge pressure and "trips" the Nox water system
( but only in it's mind... because the Nox water system was shut down just moments earlier by the other 2 processors!)

Wala! our elusive condition which requires the master reset....and also prevents FSRSD from ramping to 100% at zero TNH ( dropping out L94 rung). but only if we are in "remote", not in remote, FSRSD will ramp normally.

This particular rung, our L30A135 - was a add-in which will automatically give the unit a normal "stop" if any ( of the 6 possible) problems related to Nox water injection are detected.
( added due to a midnight-shift dose of wisdom, wisdom - which comes from bad experiences, ('nuf said))

The magnetic pick ups on the fuel flow divider: there are 3, one for each processor, signal is from the pick-up
to the AIO card, then to the HPRB card in each processor. Pick-ups for <R>and<T> are next to each outher on
one end of the divider; Pick up for <S> is a lone soldier on the opposite end of the divider. Interesting.
( we did a comparison of FQ_PR on our other CT and found a similar disagreement on fuel flow between
<R>and<T> - however on that unit <S> is reading a lower value, so we do not have the FSRSD scenerio occurring
because <S> votes to shut down the Nox system before it's partners on the other side of the fuel flow divider do....)

We looked at the MaxCase drawings and noted the circuitry for <S> is slightly different than that of <R> and <T>,
believe it lacks a capacitor which the other ones have. Possibly (a) degrading capacitor(s) on circuits for <R> and <T>?
Also noted a pot on the HPRB card, but resisted making the adjustment until we are sure of our actions -
believe the one pot on HPRB sets the reference pulse rate,which will also effect all other pulse channels,
eg, turbine speed, diesel speed, water flow.

Our primary question: is there a adjustment we can make only to the FQ pulse rate on <S>?

control constants for offset, gain, mult etc will effect all pulse rates (once again).

Have replaced HPRB on <S>, conditions unchanged.

Many thanks!
Anon

 

mkivguy, eh? Guess this author qualifies since he's been pouring over Mk IV drawings lately, and realizing the Max Case drawings ain't quite what they could be...or what they were once thought to be.... It could be that the capacitor missing in the <S> circuit's drawing is in fact there.... Stranger things have happened.

Since you've tried replacing the HPRB in <S> and still have the same problem, have you tried replacing the AIO module?

Have you tried swapping one of <R>'s or <T>'s inputs with <S>'s and then observing what happens? It may just be a bad mag pick-up, or the gap could need to be adjusted. You could also use a zero-crossing output frequency generator to simulate speed inputs to all three processors simultaneously (temporarily disconnect the mag pick-ups and use some jumpers to connect the three inputs in parallel to the output of the frequency generator) and monitor FQ_PR on the Logic Forcing display to see if there's any difference between the three with a single source. You only need about 3-5 VAC on the output--and it MUST be zero-crossing (no DC offset) and NOT TTL output (which is zero-based). Sine wave, square wave, sawtooth--doesn't matter, just as long as it's zero-crossing.

It's been too long since this author has actually worked on a Mk IV to recall how the pots on the HPRB work. There may be some reference to the pots on the HPRB in the Mk IV Maintenance Manual, GEK-83886. Have you looked there?

It's rumored that some of the "back-sheets" for the Directo-Matic Plus (DOM+) hardware (printed circuit cards used in the Mk IV Speedtronic turbine control panels) have "escaped" into the public domain. If someone has a digitized copy of the HPRB card, they could post it to one of the web image hosting sites, and then post the URL of the image/location here on control.com. There may be some useful information there.

Still, you may be on to something there with the capacitor thing. Not being a competent electronics troubleshooter has long been a problem for this author, but he's never heard of this phenomenon happening before. It's even stranger that the other Frame 6B (Did you mention these were dual-fuel Frame 6Bs? Oops--guess you didn't!) at the site has a slight mismatch in FQ_PR, but different from the first unit's...so there just may be something to the circuit difference theory!

Mason City, Iowa, USA, is home to the finest laundromat this author ever visited: carpeted floors, snack bar with a cook (they've got the usual vending machines, too--but one could get hamburgers and hot dogs fresh from the grill!), children's play area, TVs, AND (drum roll, please!): tanning booths! That's right--you can work on your tan while you your clothes are being washed and dried! Make some use of that time while you're waiting for the clothes to spin and tumble dry--don't just sit around eating hamburgers and hot dogs! That evening, one could enjoy a fine dinner at the Prime and Wine, looking tanned and fit (as this author has done)!

markvguy

 

Hi mkvguy (sorry 'bout that extra "i" earlier, a typo error, now I start proofreading at the FIRST line!)

Good info re GEK-83886! hadn't looked there.
next trip out will take zero crossover source
and check things out; believe FQ_PR is within spec +/- 60 RPM, but again, will check.
Unit has run 8 times with successful -
- no problem - on shutdown!

Many thanks for your reply!
Anon