Siemens S5 PLC switch of Outputs

[TONY]

I have a Siemens S5 CPU 928B with a main rack and 3 remote racks. The plant is stopping without any alarms or fault indication. You can go to the SCADA and start the plant again. This is a happening at any time. The plant can run for 6 hour and at some times it happen every 20min. PLC do not go to a stop mode.

My program is looking at one HP fan that has to run all the time. The interlock is using an always on bit (F1.0) that is generated in OB1. This fan keeps on stopping without any req. to stop.

This program is working for the last 10Years.

I have done the following to try eliminated it without any success
Change power supply’s at all the racks.
Install new 24V field power supplies.
Replace all Input and Output cards.
Replace IM cards.
Change CPU.
Record all power 24V and 220V all OK
Insert DB1 (For hardware Setup)
Make sure that all error OB is removed
Only OB in program are OB1 an OB20, OB21 and OB22

Can someone give me any suggestions that I can do to try to eliminate it?

 

[Ned_Flanders]

Put a counter in the program to actually monitor the "Run" bit and see if it is incrementing.

 

[KalleOlsen]

Any resent program changes? I am thinking of crashing M/MB/MW/MD's or similar.


Kalle

 

[L D[AR2P#0.0]]

Any resent program changes? I am thinking of clashing M/MB/MW/MD's or similar.


Kalle

You mean clashing.

 

[L D[AR2P#0.0]]

My program is looking at one HP fan that has to run all the time. The interlock is using an always on bit (F1.0) that is generated in OB1. This fan keeps on stopping without any req. to stop.

Post your interlock logic. How have you monitored the interlock logic to determine that there is no request to stop?

 

[TONY]

No the program run for the last year with out any change

 

[TONY]

I try to attach my program I battle to do this. I have add a counter on the F120.0 that is for a stop request and it stay at 0

 

[Marshy]

Could it be a problem with the supply that enables the outputs on that card? e.g. a dodgy safety contact

 

[TONY]

This is my PB120
PB 120 -FN416_P C:FPRD@@ST.S5D LEN=41
Page 1
Segment 1 Drive Interlocks Circuit
!
!-ALWAYS_1 -FN416_I
+---] [---+---------+---------+---------+---------+---------+---------+--( )-!
F 1.1 = ALWAYS_1 Utility Bit Allways Set to On -F1.1
D 120.2 = FN416_I FN416 Bin Roof Vent Fan Interlock

Segment 2 Drive Required to Run Circuit
!
!-FN402_R -FN416_N
+---] [---+---------+---------+---------+---------+---------+---------+--( )-!
! !
!-FN403_R !
+---] [---+
! !
!-FN404_R !
+---] [---+
! !
!-FN405_R !
+---] [---+
! !
!-FN406_R !
+---] [---+
! !
!-FN407_R !
+---] [---+
! !
!-FN408_R !
+---] [---+
! !
!-FN409_R !
+---] [---+
! !
!-FN410_R !
+---] [---+
! !
!-FN502_R !
+---] [---+
! !
!-FN701_R !
+---] [---+
D 93.0 = FN402_R FN402 Bin 33 Vent Fan Running OK
D 94.0 = FN403_R FN403 Bin 34 Vent Fan Running OK
D 95.0 = FN404_R FN404 Bin 35 Vent Fan Running OK
D 96.0 = FN405_R FN405 Bin 36 Vent Fan Running OK
D 97.0 = FN406_R FN406 Bin 37 Vent Fan Running OK
D 98.0 = FN407_R FN407 Bin 38/39 Vent Fan Running OK
D 99.0 = FN408_R FN408 Bin 40 Vent Fan Running OK
D 100.0 = FN409_R FN409 Bin 41 Vent Fan Running OK
D 101.0 = FN410_R FN410 Bin 43/44 Vent Fan Running OK
D 103.0 = FN502_R FN502 Mixer F7 Fan Running OK
D 106.0 = FN701_R FN701 Bin 42 Vent Fan Running OK
D 120.1 = FN416_N FN416 Bin Roof Vent Fan Run Needed
PB 120 -FN416_P C:FPRD@@ST.S5D LEN=41
Page 2
Segment 3 Drive Control and Indication
!
! -DRIVE1_F
! +--------------+
! ! DRIVE D1 !
! +120 --!DEV X-Q !-- -FN416_Q
! -FN416_F --!X-F ! :BE
! -FN416_B --!X-B !
! +--------------+
I 65.6 = FN416_F FN416 Bin Roof Vent Fan Feedback -I65.6
I 65.7 = FN416_B FN416 Bin Roof Vent Fan Bypass -I65.7
Q 65.6 = FN416_Q FN416 Bin Roof Vent Fan PLC Out -Q65.6
FB 211 = DRIVE1_F Drive Type D1 Control & Feedback -FB211

 

[L D[AR2P#0.0]]

Post the S5 code in a zip file.

 

[TONY]

I try if I click on attach it give me error on page

 

[Andrew Hardy]

If your software has run fine for 10 years, why are you looking for a software fault?

 

[TONY]

Andrew,

I have check every thing in the field and do not get a fault. Thats why I have ask for help. The outputs just go off and the comminication to the SCADA.

 

[L D[AR2P#0.0]]

Communication to SCADA stopping - how come you can start the plant from the SCADA ?

 

[Andrew Hardy]

Are you communicating to the SCADA via H1/L1? Is so has there been any change on the network? Dodgy terminating resistor or similar?

Do you have a watchdog bit monitoring comms to SCADA?