Commissioning and Startup Training Curriculum

Mod 5 - Instrument & Loop

Module from the Commissioning and Startup Training Curriculum curriculum.

Module 5 — Instrument and Control Loop Commissioning · Learning Objectives · 1. Plan and execute instrument loop checks from field device through DCS display. · 2. Calibrate field instruments using 5-point sequences and traceable standards. · 3. Commission SIS / ESD logic and execute proof-test procedures. · 4. Verify alarm priorities, set points, and deadband in the DCS database. · 5. Troubleshoot common loop failures during energization. · Instrument Calibration — 5-Point Sequence

Point	%	Check
1	0%	Zero
2	25%	Linearity
3	50%	Linearity + repeatability (up/down)
4	75%	Linearity
5	100%	Span
Typical Calibration Tolerance
Instrument Class	Accuracy
Custody transfer flow	±0.25% of rate
Process flow	±1.0% of span
Pressure (non-SIL)	±0.5% of span
Pressure (SIL)	±0.25% of span
RTD temperature	±1.8 °F (1 °C)
Thermocouple	±4 °F (2 °C) or per class
Control valve position	±2% of travel
Loop Check Sequence
Step	Action
1	Field device calibrated and certificate attached
2	Inject 0%, 50%, 100% signal at field
3	Verify DCS reading in engineering units
4	Verify scaling, range, units on graphic
5	Verify alarm setpoints and priority
6	Stroke valve via DCS output; confirm travel time
7	Sign off loop folder; mark punch as cleared
SIS Proof Testing (IEC 61511)
Parameter	Typical
PFDavg target SIL-2	1e-3 to 1e-2
PFDavg target SIL-3	1e-4 to 1e-3
Proof test interval	1–5 years per PFDavg
Proof test coverage	>90% of dangerous undetected failures
Bypass management	Signed authorization; time-limited
End-to-end test	Sensor → logic solver → final element
Alarm Rationalization Checklist
Item	Target
Alarm priorities	Critical/High/Low/Journal
Priority distribution	~5% critical, 15% high, 80% low
Alarm rate	<6/hr steady state per EEMUA 191
Chattering alarms	<1% of total
Standing alarms	<5 per operator position
Shelving	Time-limited with supervisor approval
Common Loop Problems
Symptom	Cause	Fix
Loop reads backwards	Polarity or scaling error	Swap +/- or re-enter range
Valve hunting	Tuning / deadband	Re-tune PID, check positioner
Transmitter offset	Impulse line blocked	Blow down, verify seal fill
SIS trip on startup	Bypass not armed	Authorized bypass per procedure
RTD drift	Loose terminal	Re-terminate, thermal compound
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Source: Commissioning_and_Startup_Training_Curriculum_v1.xlsx · Sheet: Mod 5 - Instrument & Loop

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