Answer / carl ellis

Although the post has lots of information, it isn't clear
exactly what the problem is.

I think the problem is that the PLC does not alarm when the
pressure exceeds (goes above) 55mbar. But I'm not sure.

Given this description: when PAHH (pressure alarm High High)
goes more than the set point which is 55 it reached up to 71
but due to timer doesn't trip . We force it and we checked
everything nothing there, let's suppose that the PLC is not
indicating an alarm state.

a) what should the PLC do at the alarm condition?
b) How is an alarm indicated? A digital output (DO) goes
high? A lamp is driven by a DO lights up?
c) What exactly does not work as it should?

If the PLC does not indicate an alarm, yet the indicated
pressure goes higher than a high alarm, the problem is NOT
the field transmitter, the problem is in the alarm setup or
alarm annunciation.

Troubleshooting depends on
- an explanation of exactly what should be happening
- an explanation of how you know it is not working; that is,
what the evidence is that it is not working.

Yes, the pressure went above 55mbar.
How do you know that?
The transmitter's local display?
A milliampmeter in the analog input circuit?

Did the alarm ever work? Or is this a new commissioning and
you're trying to get the alarm to work?

Carl Ellis
Measure First

Answer / jigar anadkat

Dear,

As you mentioned pressure shot up to 71 mBar which means channel goes to BAD state and it might not activate the logic. (Truly speaking it should but depends on how the logic has been created and what are the parameters set in IO assignment for failure situation).

If you you are using Yokogawa Prosafe RS the please make sure to take Chanel status as well in the logic configuration. So in case of IOP(+) as well as IOP(-) it will actuate the logic.

Moreover, there is a setting in IO parameter builder regarding input processing at fault situation. Please go through that as well.

Hope this will help you in trouble shooting.

Regards,
Jigar Anadkat
Instrument Engieer
IBN RUSHD
A SABIC affeliate.

When a field input to plc is coming from 400 to 600 meters and the input is in 24 V DC? So signal cable of which cross section i should select for proper signal to plc?

5 Answers   Exxon Mobil,

---

what do u mean by compensation n pid tunning?in pid tunning what you tunned?is it possible 2 tune p i d

2 Answers  

---

Generally in which location ( JB or IO card or DCS) the thermocouple compensation is done.Also where they measure the atmosphere temp ( for compensation) in JB OR DCS panel? How they compensating that atmosphere temp? is any circuit for that ( like in rtd wheatstone bridge)?

3 Answers  

---

I have a LT of 10000mmwc range. can i use this LT in 1000mmwc range of tank?? if yes than what happened???

3 Answers   Nirma,

---

How will you calibrate an interface level trol/normal level trol in line and in w/s?

1 Answers   CCIE,

---

---

i want to know the interview format fot gail, instrumentation. pls answer me in habib.sami1003@gmail.com

0 Answers  

---

where can i find a flameproof hmi unit?

1 Answers  

---

What's the difference between cold loop test and hot loop test?

5 Answers  

---

How to calibration of vibration probe

1 Answers   Mina Al Ahmadi Refinery,

---

Can any body give detail about orifice sizing?

5 Answers   Essar,

---

i want use pressure transmitter for flow ,how?

5 Answers   Gasco,

---

LADDER LOGIC Can any body state Logic on following condition Instructions to use 1-XIC 2-XIO 3-Output ONLY Program Push 1st button On - 1st lamp should On Then Push 1st button Off - 1st Lamp Should remain on Push 2nd button On - 1st lamp should Off and 2nd lamp should On Then Push 2nd button Off - 2nd Lamp Should remain on.

4 Answers  

---