General Arrangement and Isometric Drawings Details

 Concept of Piping GA and Isometric

General Arrangement drawings for piping systems and equipments are developed by piping designers. These drawings indicate the locations of main equipments in the plant. The main piping items, valves, and fittings are also indicated in the General Arrangement or GA drawings.

Piping isometric is a representation of a single pipe line in a process plant with exact dimensions and Bill of Material (BOM). It is the most important deliverable of any project where piping plays a vital role.

INDEX:-

• Piping Layout (GA)
• GA Using 3D CAD Model
• Contents of Piping Layout
• Piping Isometric
• Contents of Piping Isometrics
• Piping Material

Piping Layout (GA)

Purpose

• For piping installation within a construction area.
• Information for construction planning.
• Information for testing and pre-commissioning.
• Information for Plant Operators.

Methodology

Piping arrangement drawings produced in two stages:

1. Planning drawing (study sketches / 2D CAD )

• To solve major design problems, transmit information & co-ordinate activities of the different design departments.

• Preliminary piping arrangement for inter-discipline review & comment.

2.Final drawings (3D CAD model or Non-CAD manual drawing)

• For 2" and larger lines with dimensions and labelling

GA Using 3D CAD Model

•  G.A. drawings to be extracted from 3D CAD model.

• All verification, geometric & clash checks to be completed (including equipment checks to vendor data) before IFC GA extraction.

Non-CAD GAs

• Additional Pipe support GA’s issued for construction to reflect pipe support requirements only.

Design Data

Column and vessel orientation design sketches including:

•  Nozzles and manway
•  Column and vessel piping
•  Platform and ladder size
•  Instrument orientation and location
•  Height of tower and vessel skirts

• Orientation of major equipment nozzles, i.e. pumps, exchangers, compressors, etc.

• Top of grout for all equipment foundations & pads.

• Pipe rack widths, bent spacing and top of support elevation of main pipe racks.

• Allocation of space for electrical, instrument racks, analyser houses, switchgear, and utility hose stations.

• Location of all main structural columns.

• Elevations of structural levels and extent of platforms, ladders and stairs required.

Contents of Piping Layout

• Equipment co-ordinates.

• Elevations (Piping, Equipment, Platforms, etc.).

• Line No. Identification and Flow Arrow.

• Instrument Identification

• Match lines.

• Drawing Continuation References.

• Key Plan Identification.

• Complete "Holds" List.

• Reference Drawings.

• Structural Column Identification.

• Piping Layout - Checkpoints

• Conformance with P&ID's for

• Line number, size, classification, direction of flow.

• Instrument connections and numbers (long form).

• Piping material classification changes.

• Drawing "Holds" list.

• Drawing title block & Drawing key plan.

• Compliance with standard drawings and plot plan.

• Adjacent drawings & key plans for correct co-ordinates & drawing references.

• Fire & Safety requirements & location of fire fighting equipment.

• Location of Drain hubs, Utility stations, safety showers, eyewashes, drinking fountains & ladders.

• No fouling of piping with structures, equipment and other lines.

• Requirements for operating aisles, headway and roadway clearances and other mandatory dimensional clearances.

Piping Isometrics

Purpose

• Adequate information to fabricate shop pipework.

• Adequate information to field run small bore piping.

• Adequate information to erect the pre-fabricated pipe spools.

• Adequate means of identifying materials for above mentioned isometrics.

• Adequate information for locating & identifying pipe supports welded to shop fabricated pipework.

Methodology

• Shop and field isometrics to be extracted/drawn & self-contained within a model base, plant or unit as defined at start of job.
• Shop isometrics to be adequately dimensioned to enable spooling and/or shop fabrication.
• Field isometrics to be extracted/drawn with overall dimensions only for material purposes & to assist field erection.

Isometrics using 3D CAD Model

• Isometrics to be extracted from 3D CAD model.

• Isometrics need not be fully checked dimensionally.

• P & ID check of the isometric and yellow off to be done.

• Material to be downloaded from model.

• Isometric to be downloaded for piping spool drawings.

Non-CAD Isometrics

• Manually prepared on Isometric Sheet.

• Both dimensional and P&ID checks to be done.

•  Material to be manually entered.

Contents of Piping Isometrics

• Line Number & Size

• Pipe Classification

• Direction of Flow

• Equipment Reference & Nozzle Identification

• Structural Number Identification

• Isometric Drawing Continuation References

• All Valving (except vent and drain valves)

• Strainers, Traps & Flexible Hoses

• Break with Shop and Field

• Field Welds (but not shop welds)

• Vents (as V) & Drains (as D)

• Orifice Assemblies

• Spectacle Blinds and Spacers

• Instrument Numbers, such as PI, TIs, TWs, etc.

• Instrument Connections

• Out of Specification Items

• Sample Points

• Special Shop Attachment of Pipe Support

• Dummy Legs

• Cold Pull

• Special Line Features, such as Fall, Reinforcing Pads, Weep Holes, Welded Lugs, etc.

• Spool Identification (suffix letter only)

• Insulation (include limit)

Piping Material

Scope

• Material take-off

• Updating & control of material quantities with design

• Monitoring of material requisitions.

Method

• Automated Material Control
• MTO download from 3D CAD Model
• Manual Material Entry (for non-modelled items).
• Link to Procurement Tracking System

Piping Stock Code

Project Stock Code Index generated by Piping Material Classes to be issued as a project specification.

Responsibility

• Lead Piping Engineer to schedule and co-ordinate all piping material take-off activities and material requisitioning.

• Civil Group to give take-off of underground carbon steel non-pressure piping using the appropriate piping class.

• Instrument Group to give take-off of all instrument piping beyond the primary (root) block valve (except at level instruments).

• Electrical Group to give take-off of all electrical cable duct piping.

• Piping Materials Engineer to transmit a summary of all tubing and tubing fittings requirements to Instrument Group for requisitioning.

Material Control

Initial material take off from :

• Completed preliminary line routings in the CAD model

•  Manual take off from P&IDs

• Total forecast material requirements including working surplus and contingency form the basis of the Bulk Material Requisitions.

• Frequency & timing of material extractions from CAD model & manual MTO ensure that bulk material status is concurrent with design.

• Field material control is possible as the data within the piping material control programme is downloaded to Procurement Tracking System.

• Material requisitions issued to procurement for enquiry/ purchase.

• MR quantities issued for purchase (initial & at each revision) are downloaded to Procurement Tracking System.

Welcome to Our Blog Active Piping Knowledge.

I am Afzal an experienced piping engineer from the last 8 years. Through this platform, I will share my experiences and knowledge with you in an innovative way. So be with me for the next couple of years!

For any Query 

afzalpipingknowledge@gmail.com