Pre-commissioning is where E&I installation gets proven before systems are put into service. Done thoroughly, it turns commissioning into confirmation. Rushed, it turns commissioning into fault-finding with operators watching. The pre-commissioning checks for electrical and instrumentation systems are listed below, along with how to organize them so they do not become the bottleneck.
What are E&I pre-commissioning checks?
E&I pre-commissioning checks are the static, de-energized or low-energy tests carried out after installation to confirm that electrical equipment, cables, instruments and control loops are installed correctly, undamaged and ready for commissioning. Where pre-commissioning ends and commissioning begins is explained in pre-commissioning, commissioning and startup: key differences.
Electrical checks
- Cable continuity and insulation resistance, re-tested after termination
- Earthing system resistance and equipment bonding continuity
- Phase sequence and polarity
- Motor insulation and winding resistance, plus uncoupled solo runs where the project classes them as pre-commissioning
- Lighting and small power functional checks
- Heat tracing circuit insulation and resistance
- Panel testing, as described in panel installation and testing
Instrumentation checks
- Calibration verification against datasheet ranges, on the bench or in situ
- Impulse line leak tests
- Control valve stroke tests: full travel, fail position on loss of air or signal, and stroke timing for on-off valves
- Cold loop checks from field device to control system
- Fire and gas detector checks with test gas or simulation, which may extend into commissioning
Loop checks need their own plan
A loop check confirms that a signal from a field device reaches the right point in the control system with the correct range, units and alarms, and that control outputs drive the field device correctly. On a sizeable plant, the loop count can run into the thousands.
Plan loop checks by system, starting with those commissioning needs first, usually utilities. Work in two-person teams, one in the field and one at the console, in radio contact. Agree in advance what happens when a fault is found: fix it on the spot if it takes minutes, otherwise punch it and move on. Teams that stop to fault-find every issue fall behind fast. This is where control system installation errors surface, as described in control system installation.
Organizing the records
| Record | Contents |
|---|---|
| Test sheets per item | Readings, test equipment ID and calibration date, signatures |
| Loop folders | Loop diagram, datasheet, calibration certificate, loop check record |
| Punch list | Defects found, category and owner |
| System status | Percentage of checks complete per system |
Many projects keep these in a completions database so status by system can be reported daily instead of being rebuilt from paper at the end. Test equipment calibration must be current. Readings taken with an out-of-date meter are unlikely to be accepted at handover.
Why pre-commissioning stalls
- Cables tested before termination but never re-tested after
- Vendor data missing for package instruments
- Instruments removed for flushing and not tracked back in
- Too few instrument technicians at the loop check peak
When checks are complete, each system goes through the gate described in the commissioning readiness checklist. Cable test requirements are covered in cable tray, cabling and termination controls.
Apex Core Engineering supports E&I pre-commissioning with technicians and supervisors deployed through its manpower services, and with planning and coordination through its project support services.
Frequently asked questions
What is a cold loop check?
A check of a loop’s wiring and signal path without process conditions. The signal is simulated at the field device and confirmed at the control system.
What are punch A and punch B items?
Category A items must be closed before the system is commissioned. Category B items can be closed later without affecting safe commissioning.
Who carries out E&I pre-commissioning?
Usually the construction or completions team with E&I technicians, witnessed by the commissioning team and the client.
Get E&I pre-commissioning support from Apex Core Engineering.