Instruments documents a Instrumentation engineer should know about:

There are different kinds of documents in a process industry that are helpful to assist a technician/engineer working in the process industry. Such standard documents help to understand the process, installation, wiring and specifications for an experienced or fresher technician in the plant.

Here are different kinds of documents commonly used in a plant:

Tubing schedule:

The document that contains lists of instrument tubing that serves as an impulse line, hydraulic/pneumatic supply and return line, process tubing such as chemical injection line, fusible loop.

This paper also displays the tubing information needed to connect two points. The minimal information contained in the tubing plan shall be:

  • Tubing tag number
  • Description of source and destination points
  • Tubing size
  • Tubing wall thickness
  • Tubing material
  • Tubing length
  • Tubing rating

Where to use:

Tubing schedule documents are the primary reference to purchase materials. The tubing schedule will also be referred to as a comprehensive installation list during the construction phase, but the tubing length specified in this document should be checked on the field before any cutting is done.

Instrument Data Sheet:

Instrument Data Sheet is a file that includes an instrument system configuration and data.

It specifies general instrument information such as tag number identification, service description, location (line number / equipment number), P&ID or drawing number reference, process data (if applicable), calibrated range (if applicable), material, performance details (such as accuracy, linearity, if applicable), hazardous (electrical device) certification, required accessories, etc. Information details in the datasheet may vary from one instrument type to another such as a transmitter, switch, gage, control valves.

Purpose of Datasheet:

  • Instrument data sheets are used by vendors to determine to evaluate their products.

  • The machine is purchased by the vendor after understanding its technical and economic aspects. The seller must send a supporting report and draw after the purchase order. The instrument data-sheet can be updated based on vendor data to accommodate details to “as-built” the datasheet.

An instrument Datasheet includes:


Provides general information such as instrument tag number, description of service, line number/equipment number, P&ID number.

Process data:

For instrument selection, some of the following process data should be available: fluid type, fluid state (gas/liquid), design pressure, operating pressure, design temperature, operating temperature, flow rate, density, viscosity, specific gravity, specific heat ratio (gas), molecular weight (gas). Nevertheless, the information required to determine the system data in the datasheet varies depending on the type of instrument. A pressure gage datasheet, for instance, does not require a specific heat ratio. Instrument engineer can pick instrument content, adjusted range, body score, etc. by understanding these system data.

Project specification:

The organization has a standard specifying the minimum instrumentation requirement. It also includes a standard to be added to the instrument to have standardized standards throughout the plant for a certain instrument.

Code and Standard:

Cross-checking of the relevant code and standard is important, although this concern was primarily addressed by design requirements.


Preparation of the data-sheet is needed for this measurement. Some of the instruments that need to be measured are a regulation valve, stress safety valve, orifice board, thermowell.

Cable Schedule:

Cable schedule contains details of the instrument cables. The document shows the cable provided by each instrument or attachment as well as the gland. The cable scheduling details shall be:

  • Cable Number
  • Cable Type / Specification
  • Cable Size
  • Cable Length
  • Source and destination termination description
  • Cable gland type and size for each incoming cable



Cable schedule is a reference in the preparing Take-Off of cable for procurement. However, the length of the cable shown in this document is only approximate. Therefore, flexibility for the procurement of materials would make spare for cable cutting, unforeseen field wall, riser, etc.

The cable schedule will also be deferred during the construction phase, but it is not advised to cut the cable based on the cable schedule duration data.

Cause and Effect:

In some projects, cause and effects are considered as a part of instrument documents and in another case, it is part of instrument deliverables.

Cause and effect are viewed as a matrix form. The causes are listed in the left section while the effects are listed in the top section, both of which are described with their descriptions in the form of tag number (other additional information such as P&ID may be added).

There are two categories of Cause and Effect Diagram:

  • ESD C&E Diagram
  • Fire and Gas C&E Diagram


Document of cause and effect will be translated by the control system engineer into program language and implemented as logic in the control system. Throughout the operation, these logics will always track the plant and operate if the predetermined state has been reached.