Documents and drawings, which is essential for instrumentation engineer.

Documents and drawings, which is essential for instrumentation engineer.

As an instrumentation engineer, one must be familiar with the following documents and drawings.

Documents

  • Instrument index.
  • Instrument data sheet
  • Cable schedule
  • Bill of material.

Drawing

  • JB & Instrumentation location drawing.
  • GA Drawings.
  • Piping instrument drawing.
  • Hook up drawing

Documents

Instrument index

An instrument index is a consolidated list of all instruments which is used in the plant. Instrument index is made according to the P&ID. In this all instruments tags are listed in an orderly manner. It consists of following details.
  • Type of instrument.
  • Location of an instrument.
  • Installation standard.

Data sheet

Data sheet is a document which contains information about the performance and characteristics of an instrument. 

Cable schedule

We can categorise the cables in to two type Primary cables and Secondary cables.

Primary cables

Cable which is laid between junction box and control room is called primary cable.

Secondary cables

These cable is laid between instrument and junction box.
Cable schedule gives the details about from where the cable has to come and where it has to go. For easiness each cable is tagged and the details is mentioned in cable schedule.

Bill of material

Bill of material is a list of raw material required. For impulse piping lot of materials are required. Eg: elbows,nipples,tees,coupling etc. By referring bill of material an engineer could get an idea about the material required and its specification.

Drawing

Junction box(JB) & Instrumentation location drawing.

What is an instrument location layout?
Instrument location layout is a layout which indicates the exact location of instrument/junction box, trench/trays etc.
Trench and duct is the path for primary cable and tray is the path for secondary cables. A tray is either made of metals or FRP (Fiber reinforced plastic).

What is Junction box and Junction box location drawing?

A junction box is an intermediate between instrument and control panel. A junction box is an electrical box which contains terminal blocks. The cables from the instruments come to one side of the terminal block and from the other end, it goes to the control panel. Cables from the control panel is called primary cables. Usually, multicore cables are used as primary cable. Cables to the instruments are called primary cables. Usually, single core cables are used as secondary cable.

What is the purpose of a Junction box?

Purpose of a Junction box is to give convenience and protection for cabling between instrument and control panel. In maintenance point of view, a junction box is very much important. It helps very much in troubleshooting. For proper entry of cables to the JB, Jb arches are used. Cables are entering to the JB through cable glands. The cable gland is used for the proper placing of cable. Different types of cable glands are available

Piping instrument drawing

A piping and instrumentation diagram (P&ID) is a detailed engineering diagram indicating and depicting the relationship between piping, process equipment, instrumentation, and control devices. A P&ID is used to describe the overall engineering processes.

How to Draw a Piping & Instrumentation Diagram

A piping and instrumentation diagram is drawn up at the design stage of a process to model the system. It consists of a combination of the process flow datasheet, the mechanical equipment design, and the instrumentation engineering design. Diagrams can range in complexity and either be hand-drawn or created using specialty software. Once the initial P&ID is complete, we like to use Bluebeam Revu for P&ID markups during online engineering squad checks.

Tools Required

  • A Computer
  • Appropriate Software

Simple steps to draw your own P&ID

Step 1: Define the scope of the system
Before drawing a P&ID, you need to understand the overall process? What does it achieve?
Step 2: Identify the inputs
Are they manual or automatic? Where are the inputs coming from and leading to?
Step 3: Identify the outputs
What is the end product? What do you need to achieve it?
Step 4: List all the equipment in the process
Think about the instrumentation, control devices, piping and equipment.
Step 5: Define the relationship between components
How do they interact? Are they compatible?
Step 6: Piece together your flow
Start either at the beginning or end of the process and work through it methodically. What happens next in the system?
Step 7: Add detail
Add pipe, component, and instrumentation details such as measurements and sizes.
Step 8: for bottlenecks and inefficiencies

List of P&ID items

  • Instrumentation and designations
  • Mechanical equipment with names and numbers
  • All valves and their identifications
  • Process piping, sizes and identification
  • Miscellanea – vents, drains, special fittings, sampling lines, reducers, increasers and swaggers
  • Permanent start-up and flush lines
  • Flow directions
  • Interconnections references
  • Control inputs and outputs, interlocks
  • Interfaces for class changes
  • Computer control system
  • Identification of components and subsystems

Hook up drawing

It is a detailed drawing showing typical installation of an instrument in a correct manner so that the instrument operates properly and prevent issues which could potentially affect the measurement such as liquid trap in gas impulse
In general, these hookups provides the details of the installation to ensure proper operation. Instrumentation Construction Personnel has to review and verify certain important points before going for an Instrument erection.
  • Tag number
  • Numbers of the loop drawing.
  • Layout & routing drawing and isometric piping drawing containing the particular control loop component.
  • Elevations of both the primary control loop component and process connection.
  • Tagging of mechanical (piping or equipment) to instrumentation interface
  • Tagging of all elements/fittings & valves with item numbers.
  • Direction of slopes in hook-up lines.
  • Elevation of Instrument.
  • Maximum allowable lengths of hook-up lines.
  • Accessories often detailed include Mono-flanges, Double Block and Bleed Valves and Fittings etc.
  • Material take off with part numbers, number of particular fittings, size, connection, material type, mounting type.
  • weather shield and tubing specification.

There are two types of Hookup drawings

  • Process Hookup drawing.
  • Pneumatic Hookup drawing

Requirements for a Hook-up drawing

  • Contract Requirement and Project Design Criteria
  • Piping and Instrument Diagrams 
  • Instrument List (with Instrument Datasheet)
  • Piping Material Classification (PMC) or Piping Material Specification (PMS)
  • Instrument Rack grouping, elevation of tapping and rack
  • Control Valve List (for Instrument Air)
  • Tank and Heat Exchanger GA drawings

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