Instrument Index

What is an instrument index?

An instrument index is a document that lists and provides information about the instruments and devices used in a process industry setting. The instrument index typically includes details such as the type, location, and function of each instrument, as well as its manufacturer and model number.

Instrument indexes are used to document the instruments and devices used in a process plant or facility, and to provide a reference for maintenance, repair, and calibration activities. They may also be used to identify the location of instruments and devices within a plant or facility, and to provide information on their interconnections.

An instrument index may include the following information for each instrument or device:

• Name or description of the instrument
• Manufacturer and model number
• Location of the instrument within the plant or facility
• Process variable being measured or controlled by the instrument
• Range and accuracy of the instrument
• Electrical characteristics, such as voltage and current requirements
• Maintenance and calibration requirements
• Any relevant certifications or approvals

Instrument indexes are an important tool for process control engineers, technicians, and operators in understanding the instrumentation and devices used in a process industry setting, and in ensuring that they are properly maintained and calibrated.

All physical instruments, including field instruments, physical alarms, indicators, and pseudo instruments sometimes known as “soft tags,” must have a tag number (e.g., DCS indication, alarm, and controller) which will be listed in this Instrument Index.

The instrument index shall be prepared at the outset of the project and treated as a living record maintained. If there are any plant or system modifications that result in the addition, removal, or resetting of instruments, the instrument index must be updated.

What is the purpose of an instrument index?

An instrument index catalogs all instrumentation for a specific project or plant. The purpose of an instrument index is to provide a comprehensive list and reference for the instruments and devices used in a process industry.

An instrument index serves several important functions, including:

1. Documenting the instruments and devices:

An instrument index helps to document the type, location, and function of each instrument, as well as any relevant technical details such as manufacturer and model number.

2. Facilitating maintenance and repair activities:

An instrument index can be used to identify the location of instruments and devices within a plant or facility, and to provide information on their maintenance and repair requirements.

3. Providing a reference for calibration activities:

An instrument index can be used to identify the instruments and devices that require calibration, and to provide information on the calibration procedures and standards that should be followed.

4. Facilitating troubleshooting and analysis:

An instrument index can be used to identify the instruments and devices that are connected to a specific process or system, and to understand their role in the overall process. This can be helpful in troubleshooting problems and analyzing the performance of the process.

For the following reasons, an instrument index will be referred to as an index:

• As a foundation for generating the I/O list by extracting only the tag number that has an I/O point.
• The instrument index is typically presented in tabular form and it is generated at the beginning of a project for Searching, Displaying, and Filtering a Tag Number.

What is included in an Instrument index?

Instrument index should include, but are not limited to, the following details in document:

• Tag number
• Instrument type
• Location
• Service Description
• P&ID number
• Line number or equipment number
• I/O type
• Control system
• Range or set point with engineering unit
• Manufacturer reference Document
• Model Number
• Manufacturer
• Package Number
• Hook-up Drawing Number
• Instrument Layout Number
• Loop Drawing Number

How do you create an instrument index?

For the instrument index to be full of information, the following references are required

1. P&ID (Piping and Instrumentation Diagram )

From the P&ID, all instrument tag numbers and the information that goes with them are gathered, such as the service description, instrument type, line/equipment number, and set point. A good P&ID may have symbols that show which control system each instrument is connected.

 2. Instrument datasheet

From datasheet information such as the range of measurements that the instrument is capable of making, the accuracy and precision of the measurements, the input and output signals, the power requirements, and any other relevant technical details.

Example Instrument Index

The below schedule is a typical instrument index

Instrument index template (To download)

The instrument index template for download is available below.