Wednesday, August 23, 2017

Basics of Piping discipline

Basics of Piping discipline 

I am writing this post to help young engineers to prepare for job interviews. Because every engineer goes for industrial  or job tanning for  a few months during their courses where they had been introduced to all engines seeing discipline so they are suppose to know about each engineering discipline.
Don't worry if you forget all about that, just read below about piping discipline and comment on the post if you like it . Than I will post about other disciplines also.

Piping to a chemical plant is often compared with what  the veins and arteries to a human body are, the means for transporting all the essential fluids from and to the equipments necessary for running a plant. 
It incorporates valves and instrumentation and other in-line equipments for the purpose of flow regulation as well as to ensure the safety of the plant.
Preparation of Plot plan for the plant being designed.
Preparation of Equipment Layout.
Preparation  of the layout for the piping connecting different equipments and utility stations in a plant.
Providing proper supports to the piping systems to avoid overstressing 
Piping Material take-off
Procurement of piping materials.
While designing the equipment layout / plot plan of a plant and its piping systems, the requirements stipulated in the following documents form the basis of the same:
1.Piping Design Basis
It is the document that forms the very basis of the philosophy to be  followed in designing the plant layout and the piping systems.
2.ASME codes B-31.3
For Chemical and Process industries this code is followed universally. It gives the complete guidelines – from design to construction to non- destructive examinations to pressure testing of the piping systems.
3.Piping and Instrumentation Diagram
This document is received from Process Engineering, The lines, their sizes and the equipment and their sizes are decided based on Process calculations and the same data is provided in the P&ID.
4.Line List
This documents consist the data pertaining to the piping class, pressure-temperature conditions, type of fluid, density, test pressure and insulation requirements of the line. These data are essential for calculating the pipe thickness and for the stress calculations.
Equipment Drawings
The drawings are first prepared by the Mechanical Equipment department and finalized after due deliberation with the client and the supplying vendor. These drawings are required for preparing the plot plan / equipment layout, piping layout preparation and for stress calculation of the connected piping.
International Codes and Standards – 
There are a number of codes and standards which are followed worldwide as the base specifications for the purpose of plant piping  design and for the purpose of procuring the piping materials.
These standards are prepared by some globally acknowledged engineering societies based on their century old experience with the materials / commodities and inputs from the manufacturers and feedback from the engineers worldwide who are the end users of those materials. 
As example, few of them are mentioned below:
American Society of Mechanical Engineers:
ASME B-36.10 – Welded and seamless wrought steel pipe
ASME B-36.19 – Stainless Steel pipes
ASME  B-16.10 -  Face to face dimensions of valves
ASME B-16.34 – Valves- flanged, threaded and butt-welding end
ASME B-16.5  - Pipe flanges and flanged fittings
ASME B-16.9 -  Wrought Butt-Welding Fittings
ASME B-16.11 – Forged Fittings, Socket welding and threaded
ASME B-16.20 – Metallic Gaskets for pipe flanges
American Petroleum Institute:
API 5L – Specifications for Line pipes
API-6D – Pipeline Valves
API – 598  -  Valve Inspection and Testing
British Standards:
BS - 1868 : Steel Check Valves
BS - 1873 : Steel Globe and Globe stop and Check valves
BS - 5351 :  Steel Ball Valves
BS – 14692: Petroleum and Natural Gas industries – GRP Piping
International Organization for Standardization :
ISO 14313 – Pipeline Valves (adopted from API- 6D)
ISO 17292 -  Steel Ball Valves (adopted from BS-5351)
ISO 10474 -  Steel and Steel Products – Inspection Documents
Client’s specifications
Many of the clients are having their own set of requirements which are specified in their own in-house specifications.  In particular, the clients with huge operations like Shell, ADCO, Takreer  etc. do have their own specifications covering each aspect of design. These specifications are either covering some top-up requirements to the international codes and standards mentioned above, or in the pretext of some engineering aspect for which no international standard is available. These specifications are to be followed while designing any plant / piping system in an existing plant for the same client.
Piping layout activity consists of two parts –
1.Preparation of the Plot Plan and the Equipment Layout:
In preparing the equipment layout, each major company has got its own norms. Normally this incorporates the local regulations about the inter-equipment spacing and other safety measures. Wherever a number of equipment are involved, usually the equipment are placed on both sides of one or more pipe ways.
2.Preparation of the piping routings :
The lines are routed through the shortest route possible. At the same time, it is required to ensure that the configuration is not too tight to generate a stress which may cause failure or overloading on the connecting equipment nozzles.

Piping Materials

Generally the piping materials consist:

1.Pipes 2. Flanges 3. Elbows 4. Tees 5. Reducers / expanders 6. Branch 7. Fittings 8. Valves
9.Gaskets 10. Bolts and nuts
and other specialties like strainers, flame arrestors etc.

Out of these items, valves are the most costly and complicated items and are available in different types:

1. Gate valve, 2. Globe valve, 3.Check valve, 4.Butterfly valve, 5. Ball valve,
6. Plug valve, 7.Diaphragm valve, 8.Needle valve, 9. Safety valve etc.

with separate standards available for each one of them.

Piping Stress analysis and supporting.

Each line is supported considering its flexibility.
Where the line is more rigidly supported / restrained, stress developed with thermal expansion is more.
Lines become more rigid with an increase in diameter and thickness.
For each project a stress critical line list is prepared based on the client’s / project-specific requirement. Usually those are very big diameter lines or connected to some sensitive equipments or are prone to vibration due to two phase flow.
Allow stress limit in the piping system is as specified in ASME B- 31.3
Loadings on the supports are provided to Civil Engineering department for designing the supports
The procurement related activities include the preparation of Material Requisitions & Technical Queries, carrying out Technical Analysis of Quotations, preparation of Purchase Requisitions and carrying out Vendor Document Review.
The template for Material Requisitions is prepared by the QA department for each project.  This is used along with the Data Sheets and other attachments as applicable. Upon receipt of Client and End User comments, these are incorporated in the revised document and issued for enquiry.  The Client or the End User floats the same to the Vendors as per approved list.
• The Vendor Offers are first reviewed and Technical Queries, if any, are raised to Vendors using TRE TQ template.
• The Vendors response to Technical Queries, if any, are evaluated and then the Technical Analysis of Quotations raised to Client using TRE TAQ template.
• Based on project scope, the Material Requisition is then updated with selected vendor specific information and reissued as Purchase Requisition for order placement by Client.
• For critical items like valves etc. the Vendor after receipt of order, proceeds with his engineering and submits the various documents & drawings for review.  This process is called Vendor Drawing Review where each drawing is reviewed and commented by the piping material engineer.
• Based on inspection requirement for the specific item (based on the appropriate code), the Vendor notifies the Client for Inspection at Factory when the same is required.
• Following inspection and successful pressure testing, the items are shipped to the construction site.
1.AUTOCAD (for 2-D modelling)
2.PDS (For 3-D modelling)
3.PDMS (For 3-D modelling)
5.CAPS (For MTO prepn)
6.CAESAR – II (For stress analysis)
7.MS Office

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