Basic Guide lines to be followed during DCS/PLC Loop Checks

 Basic Guide lines to be followed during DCS/PLC Loop Checks

Basic Guide lines to be followed during DCS/PLC Loop Checks

1. Location of the instrument Tag no. to be checked (As per P&ID)

2. Tag number & Description of the Tag to be checked.

(For Ex: Flash drum level or Instrument air header pressure or Hot oil heater inlet Temp or HP Fuel gas inlet flow)

3. Range & Alarm values for that Particular instrument to be noted. (As per Instrument index or IO List)

4. Unit of that particular tag both in DCS & Field also to be verified.

(Level: m, %, Flow: m3/hr or Nm3/hr or Sm3/hr or Kg/hr, Pressure: barg or bara or mbarg or mmwc or mmhg, Corrosion: mm/yr, Temperature: “C, Control valves: arrow for Fail Open or Fail Close types)

5. For All Transmitters, the checks to be done for 0%, 50% & 100% of the total range.

6. If the Flow Transmitters is of DP type, checks to be as follows: For Eg. For Transmitter Range: 0 to 100 m3/hr & DP Range: 0 to 500 mbar, 0% (0 mbar) = 0 m3/hr; 25% (125 mbar) = 50 m3/hr; 50% (250 mbar) = 70.7 m3/hr; 75% (375 mbar) = 86.6 m3/hr; 100% (500 mbar) = 100 m3/hr

7. All Level Transmitters to be checked only with water. If they are not using water (except vessel mounted Radar Transmitter), report in DPR that LIT was checked with mA & to be checked with water again.

8. For DCS Transmitters, normal checks, Alarm values & its recovery values to be checked by simulating from field.

9. If Instrument Index & Data Sheet Ranges are not matching, please record in your DPR

10. For all Alarm values simulation, check for alarm in Current Alarm Manager (CAM). When an Alarm comes, it has to blink in graphics in Red, if we accept it will become static.

11. For ESD Transmitters, Alarm values, LL or HH or either & SC (Short Circuit), OC (Open Circuit) to be checked by simulating from field.

12. Alarm description to be checked (For Ex: IA header pressure low or Hot oil heater all temp. High or HP fuel gas inlet flow low)

13. Color of the Display in Graphics also required to verify.

14. For Control valves, the stroke checks to be done for 0%,25%.50%, 75%, 100%, 75%, 50%, 25% & 0%.

The valve openings actually in Field to be confirmed from Person on Field & Recorded in Loop checks report.

For Checking Fail Open type, Close the valve, isolate the instrument air supply & reduce the air pressure by bleeding off (the Control Valve should open & opening in DCS & Field should match).

For Checking Fail Close type, open the valve 50%, isolate the instrument air supply & reduce the air pressure by bleeding off, (the Control Valve should close). Color change also to be checked.

15. Manual & Auto change over from Face plate Controllers to be checked & control valve moving action, in case of Control valves.

(Direct & Reverse action of Controllers as per control narrative also to be verified). Some of the controllers, we have seen Action given in Control narrative is wrong. Please identify & report in DPR.

16. Check Control Valves, XV’s, SDV’s, BDV’s either permanent instrument air tubing is connected or not. If not, don’t check that valves. BDV’s, few SDV’s, few XV’s, few PCV’s has Volume Bottle. Ensure Volume bottle is connected or not as per design. Otherwise report in your DPR.

17. During SDV Loop Checks: Open, Close, Fail Open, Fail Close, reset, PST & mismatch alarm to be checked. Color change in Graphics & Face plate for SDV’s to be checked while open & close operation.