What is Loop Folder?

A loop folder is a manila folder or an electronic folder that contains an assortment of documents related to the instrumentation for a specific process control loop.

The exact contents of a loop folder are defined in a project's standards/requirements.

A loop folder typically includes
- instrument manufacturer's spec/data sheet
- P&ID
- loop diagram
- loop check test sheet/checklist
- instrument calibration cert
- plot plan/location diagram

It can include
- loop test procedure
- hook-up diagram/instructions
- control/function narrative
- alarm setpoint list
- construction completion certificate
- interlock diagram
- flow sizing sheet
- CoC Certificate of Conformance
- COE Certificate of Origin
- MRT Material Test Report
- NACE certificate
- instrument configuration

The world runs on paperwork.

. . . what is loop checking?

Here's Mr. Emerson's view on loop checking:

Wiring Checkout and Loop Check

The first step in commissioning a new instrument is the physical installation. The physical installation steps are the same for both the traditional and new approach:

1. Review P&ID drawings for location and piping instructions.

2. Review device instructions for proper location, mounting, and piping.

3. Verify field device is physically located in the correct location per the P&ID. Verify that a permanent tag label is securely attached to the device that clearly indicates the assigned loop tag number.

4. Verify field device is correctly connected by performing the following inspections:
a. Physical inspection- properly mounted and oriented as designed, ensure close-coupled connections are securely fastened; pipe stands are structurally sound

b. Mechanical - Sensing lines, and other process connections are properly installed, connected and verified per instrument design specification

c. Electrical - Conduit runs are properly connected; seal drains are installed correctly, etc.

5. Verify the input or output signal is within the device's normal operating range.

6. Verify that any special/custom device characteristics required are present (example: custom gas curves, special construction materials, etc.)

7. Measure and adjust associated air and electrical power supplies.

8. Measure loop impedance by disconnecting the signal wiring at both the transmitter and rack room ends, shorting the signal wiring at the transmitter and measuring the loop resistance with an ohmmeter at the termination panel end.
This process typically takes two technicians with two-way radios for communication.

9. With an ohmmeter, verify there are no shorts to ground in the signal wiring by checking the wiring to ground while the wiring is still disconnected. This process typically takes two technicians with two-way radios for communication.

10. Verify proper wiring polarity.

11. Connect the wiring to the transmitter in the field and in the rack room.

12. Verify that all field wiring is properly labeled per the instrument loop diagram. This includes
all terminations per the instrument loop diagram.

13. Verification that all instrumentation wiring is mechanically sound by performing a physical "Tug Test" of the wires.

14. Verify that the field device enclosure is closed, all temporary shipping stops removed, and the device is mechanically fit for service as defined above and in the device instruction manual.

15. Apply power to device.