Instrument Hook-up Diagrams

What is an instrument hook-up drawing?

An instrument hook-up diagram, also known as an installation drawing, describes the scope of work between the mechanical and instrumentation departments.

The hook up drawing explains how to properly install the instruments, from the tapping point in the process line up to the measuring and control instrument, to ensure that the instrument performs well and to eliminate difficulties that could affect the measurement.

Detailed Explanation of Instrument hook-up diagram:

An instrument hook-up diagram is a detailed diagram that shows the components of a control loop in an industrial automation system and how they are connected to the process tapping points.

It is used to specify the various instruments and devices that are used to measure and control process variables such as temperature, pressure, flow rate, and so on.

What are the details in the hook-up drawing?

  • The hook-up drawing depicts tubing slopes, the position of the instrument in relation to the process tapping point, and the separation between the instrument and the piping.
  • The hook-up drawing also specifies the amount of bulk material required for each installation. It also specifies the size, type, and material, as well as the quantity.

What are the different types of instrument hook-up drawings?

There are two kinds of hook-up diagrams:

Process Hook-Up:

This hook-up picture illustrates the typical connections that are made between instruments and the process.

Instrument Hook-up Diagrams 1

Pneumatic Hook-up:

This hook-up drawing shows typical installations for instruments that need instrument air, such as a control valve or an actuated valve.

Instrument Hook-up Diagrams 2

What is included in the instrument hook-up drawing?

Generally, the following are included in the hook up diagram of an instrument:

  • The tag number
  • The loop drawing’s numbers.
  • The layout and routing drawing, as well as the isometric piping drawing, must include the specific control loop component.
  • Elevations of the primary control loop component as well as the process connection.
  • Interface tagging of mechanical (piping or equipment) to instrumentation
  • Item numbers are assigned to all elements, fittings, and valves.
  • Slope orientation in hook-up lines.
  • Instrument elevation.
  • Maximum allowable hook-up line lengths
  • Mono-flanges, Double Block and Bleed Valves and Fittings, and other accessories are frequently detailed.
  • Take off material with part numbers, number of specific fittings, size, connection, material type, and mounting type.
  • Specifications for the weather shield and tubing
  • The hook-up drawing also specifies the amount of bulk material required for each installation. It also specifies the size, type, and material, as well as the quantity.

What is the purpose of an instrument hook-up drawing?

The objective of an instrument hook-up drawing is:

  • As previously stated, the bulk material required for installation is stated on each sheet, so the bulk material required for the entire drawings could be summarized and tabulated in a document called Material Take Off.
  • During the project construction phase, this drawing is also referred to as a guide for properly installing the instrument.

What are the requirements for creating an instrument hook-up drawing?

  • Piping Specification: The battery limit between instrument and piping must be clearly stated in the P&ID symbol and typical sheet or piping documents.
  • Classification of Piping Materials (PMC) or Piping Material Specification (PMS)
  • Installation Detail Specification: Installation detail specifications will also specify which items should be used and which factors should be considered in a single installation.
  • P&ID: P&ID informs the designer which instruments necessitate a hook-up drawing. A good designer can also tell if the instrument is in gas or liquid service.
  • Project Design Criteria and Contract Requirements
  • Instrument Datasheet list
  • Grouping of Instrument Racks, Tap Elevation, and cabinet Racks
  • Control Valves to be listed for instrumentation air supply
  • Drawings for the fluid storage Tank and Heat Exchanger etc.

An example of an instrument hook up drawing is shown below.

The diagram below depicts the components and tubing required for the installation of a pressure transmitter (installed below the tapping point). The required parts (bill of materials) are listed in the table below:

Instrument Hook-up Diagrams 3

Guidelines for installation of the instrument:

Before starting an instrument erection, an instrumentation construction engineer should evaluate and confirm a number of essential details, as below:

  • Check the instrument’s tag number or the list of instruments.
  • Separating mechanical and instrumentation in terms of task scope.
  • Bill of materials, such as stainless-steel fittings, tubing, plugs, isolation valves, manifold blocks, and transmitter mounting bracket types.
  • Each installation should be checked for bulk materials.
  • Depending on the fluid’s characteristics and the instrument sensing type to be used for measurement.
  • Instrument positioning in relation to the process tapping point.
  • It’s important to pay attention to the tubing slopes.
  • Requirements for weather protection and tubing.

What is hook-up piping?

A hook-up piping refers to the piping systems that connect different pieces of equipment or processes together.

These piping systems can include both process piping, which carries fluids or gases as part of the production process, and utility piping, which carries water, steam, air, or other substances used to support the operation of the facility.

Hook-up piping is typically designed and installed by a team of piping engineers and technicians, who ensure that the piping systems are properly sized, routed, and supported to meet the needs of the facility.

The hook-up piping is usually installed after the equipment has been set in place, and it is often a critical component in the overall operation of the facility.

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