Blog: The Importance of Instrument Specifications (Specsheets) During Pre-Commissioning and Commissioning

In any industrial project, particularly in sectors like oil and gas, chemical processing, and power generation, the accuracy and reliability of instruments are vital. This is where instrument specifications (specsheets) come into play. Specsheets are detailed documents that provide critical technical information about the instruments to be used in a project, such as sensors, transmitters, and controllers. These documents are essential during both the pre-commissioning and commissioning phases of a project to ensure proper installation, functionality, and safety.

What is an Instrument Specs Sheet?

An instrument specs sheet is a technical document that contains all necessary information about a specific instrument, including:

• Model Number and Manufacturer

• Process Variable (e.g., temperature, pressure, level)

• Range and Accuracy of measurement

• Operating Conditions, such as temperature limits and pressure ratings

• Materials of Construction, especially for parts exposed to the process

• Electrical Specifications, such as power requirements, signal outputs, and communication protocols (e.g., 4-20mA, HART)

• Calibration Data and Installation Instructions

Examples of Specsheets

1. Pressure Transmitter Specs:

   • Model: Rosemount 3051 Pressure Transmitter

   • Range: 0-100 PSI

   • Accuracy: ±0.075% of span

   • Output: 4-20mA with HART communication

   • Process Connection: ½” NPT

   • Material: Stainless steel wetted parts

2. Temperature Sensor Specs:

   • Model: PT100 RTD Sensor

   • Range: -200°C to 500°C

   • Accuracy: Class A (±0.15°C at 0°C)

   • Output: 3-wire configuration

   • Installation: Spring-loaded thermowell fitting

   • Material: Stainless steel sheath

How Instrument Specsheets Help During Pre-Commissioning

In the pre-commissioning phase, where systems are being built and installed, specsheets are essential for:

1. Instrument Selection and Procurement: Engineers use specsheets to ensure that the correct instruments are chosen for specific applications. For example, a pressure transmitter with the correct range and material will be selected based on the operating environment.

2. Installation Guidance: Specsheets provide installation instructions that ensure instruments are mounted properly, including details on process connections, wiring diagrams, and installation tolerances.

3. Calibration and Testing: Instruments need to be calibrated to their specified range and accuracy. Specsheets provide calibration data that technicians rely on to perform accurate checks before the system goes live.

4. Documentation and Verification: As part of the pre-commissioning documentation, specsheets verify that all instruments are installed and set up as per the project’s design and safety requirements.

How Instrument Specsheets Aid During Commissioning

The commissioning phase involves testing and validating systems before they are handed over for operation. Specsheets play a critical role here as well:

1. Functionality Testing: Instrument specsheets allow engineers to verify whether each instrument is functioning as intended. For example, the accuracy and range of a pressure transmitter can be cross-checked against its specs to ensure it meets project requirements.

2. Loop Checks: During commissioning, control system loops are tested to ensure proper signal transmission from the field device to the control system. Specsheets provide vital information such as output signal ranges and communication protocols (e.g., 4-20mA, HART), ensuring that the loop behaves as expected.

3. Safety Checks: Specsheets outline the operational limits of instruments, such as maximum pressure and temperature ratings. During commissioning, these limits are validated to ensure the instruments will operate safely within the process parameters.

4. Troubleshooting: If issues arise during commissioning, specsheets can be invaluable for diagnosing problems. For instance, if an instrument isn’t giving accurate readings, the specsheets can help engineers verify whether the issue lies in calibration, installation, or communication settings.

Conclusion

Instrument specsheets are more than just documentation—they are a critical tool for ensuring the success of pre-commissioning and commissioning activities. By providing detailed technical data, specsheets guide the selection, installation, and testing of instruments, ensuring systems operate efficiently, safely, and as intended. At Navonlogic, we emphasize the importance of using specsheets as part of our commissioning services, helping to ensure that all systems meet the highest standards of performance and safety.