What is Pipe:

The pipe is a cylindrical conduit or tube used to transfer fluids (e.g: liquid, gas ) or solids ( e.g: Powder, Pellets ) or semis solids ( e.g: Crude Oil ) under pressure from one point to another point.

Stresses in Pipes:

1. Hoop stress or Cylindrical Stress
2. Axial Stress
3. Radial Stress

Pipes Designator:

1. IPS (Iron Pipe Size)
2. NPS (Nominal Pipe Size)
3. NB (Nominal Bore)
4. DN (Diameter Nominal)

IPS:

it is  dimensionless size designator of pipe. it represent the Inside diameter of pipe in inches.

e.g: IPS6 means Inside diameter is 6″.

NPS:

it is  dimensionless size designator of pipe. it represent the Outside diameter of pipe in inches.

e.g: NPS6 means OD of Pipe is 6.625″ or NPS14 means OD of Pipe is 14″.

NB:

it is  dimensionless size designator of pipe. it represent the Outside diameter of pipe in millimeter.

e.g: NB100 or 100NB means OD of Pipe is 114 mm.

DN:

it is  dimensionless size designator of pipe. it represent the Outside diameter of pipe in millimeter.

e.g: NB100 or 100NB means OD of Pipe is 114 mm.

it is same as NB.

Small Bore Pipe:

Pipes having Size less than NPS 2 or 40 NB is called Small Bore Pipes.

Big Bore Pipe:

Pipes having Size greater than or equal to NPS 2 or 40 NB is called Big Bore Pipes.

Pipe Wall Thickness:

Pipe wall thickness is represented in terms of Schedule Number or Pipe Weight.

Schedule No. – 5,5S,10,10S,40,40S,80,80S,160,160S

Number with S represent for stainless pipe & Number without S represent Carbon steel or Alloy Steel pipes.

Pipe Weight – STD,XS,XXS

STD means Standards Weight Thickness

XS means Extra Strong Thickness

XXS means Double Extra Strong Thickness.

This all about basics of pipes.

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What is Mean By Code?

It consists of Standard or Rule for Design, Fabrication, Installation, Inspection, Testing of Industrial process plants.

What is Mean By Standards?

It is a group of Rules prepared by professional group of people for the Design,Manufacturing and pressure Integrity of the components.

Use of standards is responsibility of users but code has to followed as Mandatory requirement.

Codes – It is applicable For all Piping system.

Standards- It is applicable for Individual Components of Piping System.

Some Piping Codes:

1. B31.1 – Power Piping
2. B31.3 – Process Piping
3. B31.4 – Liquid Piping
4. B31.5 – HVAC Piping
5. B31.8 – Gas Piping

Major Organizations for Standards:

Principals of Piping Engineering

1. Safety : The piping system design,fabricated,installed and Inspected should be safe.
2. Construct-ability : The piping system design and fabrication Should be construct table.
3. Operation-ability : The piping system design and fabrication Should also be operable.
4. Maintainability : The piping system design and fabrication Should also be Maintainable.
5. Economy : The piping system design and fabrication Should also be economical.

Types of piping projects:

1. Greenfield project : it is Completely new piping project.
2. brownfield project : it is replacing the plant and reconstruction of the piping system.

Piping software:

1. 2D software: AutoCAD, Microstation
2. 3D software: PDMS, PDS, SP 3D, Auto Plan
3. Stress analysis software: CAESAR – II
4. Review software : SPR , Nasivwork

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What is Mean By Pressure:

Pressure is force exerted on surface per unit area.

Unit of Pressure is Pascal or N/m2.

Pressure Terms Used in Pressure Vessels and Piping:

1. Operating Pressure
2. Design Pressure
3. Maximum Allowable Working Pressure
4. Hydro test Pressure

Operating Pressure:

Pressure which is required for Process,served by vessel, at which vessel is normally operated. It can also be called as normal working Pressure.

Design Pressure:

Pressure Used in Design of Pressure Vessel or Piping System. This pressure is called as Design Pressure.It is recommended to design vessel and its parts for a higher pressure than operating pressure. it is recommended that always use design pressure should be 30 psi or 10% higher than the operating pressure.

Maximum Allowable Working Pressure (MAWP):

Internal Pressure at which the weakest element of the vessel is loaded to the ultimate permissible point, when the vessel is assumed to be in corroded condition, under the defect of designated temperature, in normal operation position at the top and under the effect of other loading such as wind load, external pressure, hydro-static pressure etc. which are additional to internal pressure.

When MAWP Calculation are not done, then Design pressure may be used as Maximum allowable working pressure.

As common practice followed by many users and manufacturers of pressure vessel is to limits the Maximum allowable working pressure by the head or shell, and not by small element such as flanges.

New and Cold Maximum allowable working pressure term very often used in pressure vessel manufacturing It means that the pressure at which weakest element of the vessel is loaded to ultimate permissible point when the vessel is not corroded (new ) and the temperature does not affects its strength at room temperature ( Cold ) and the other condition need not to be taken in to consideration.

Hydro Static Pressure:

Hydro test is the technique in which pipes, pressure vessels, gas cylinders, tanks are tested  at required design pressure of the system or pipes or vessel to check the leak and strength.

Hydro-static Pressure Calculation for Pressure Vessel:

At least,

Hydro-static Pressure = 1.3 x Maximum Allowable Working Pressure or MAWP.

When Maximum Allowable Working Pressure or MAWP calculation is not done, then we used Design pressure in place of MAWP.

Hydro-static Pressure = 1.3 x Design Pressure.

if the stress value of the vessel material at design temprature is less than the stress value at test temprature then hydrostatic pressure should increase proportionaly.

So,

Hydrostatic Pressure = 1.3 x MAWP or Design Pressure x ( stress value at Test Temperature / stress value at design temprature ).

Hydrostatic Pressure Calculation for Piping:

Hydrostatic Pressure = 1.5 x Design Pressure.

if the stress value of the Pipe material at design temprature is less than the stress value at test temprature then hydrostatic pressure should increase proportionaly.

So,

Hydrostatic Pressure = 1.5 x Design Pressure x ( stress value at Test Temperature / stress value at design temprature ).

Process of Hydro Static Testing:

Stages of Hydro Static Testing:

First Stage: Raise the pressure to 40% of the final pressure, stop pressurizing, keep it for 5 minutes, and then make a fast visual inspection of the external surface.

Second Stage: Restart pressurizing up to 70% of final pressure, stop the operation, keep for 5 minutes and make a fast visual inspection on external surface.

Third Stage: Restart pressurizing up to 100% of the final pressure, stop the operation, and keep for 45 minutes.

Activities Before Hydro testing:

1. Checking all welding already finished and fully accepted by the NDT examination per the project Inspection and test plan.
2. Making sure the inner part of the vessel is clean and free of remaining slag or other elements and also Making sure the external surface is dry for the correct execution of the visual inspection during the vessel pressure testing.
3. Checking the pressure gauges’ calibration tag and certificate and the range of the lower limit and upper limit of the gauges. It needs to be between 1.5 and 4 of the pressure test value.
4. Controlling testing equipment such as the test pump and housing for soundness and tightness.
5. Making sure the test temperature will not violate the following values:
6. Min. Test temperature= MDMT + 30°F
7. Max. Test temperature = 120°F
8. MDMT is the pressure vessel minimum design metal temperature, and it is stated in the pressure vessel design document. This reduces the risk of a brittle fracture during the test.
9. Making sure which reinforcement pads are already soap tested.
10. Controlling the testing water quality and using corrosion inhibitor if it is necessary or when the vessel metal is sensitive material
11. Checking of vents. It is required to be placed at high points of the vessel in a position where it is possible to purge air pockets while the vessel is filling.

Activities During Hydro-testing:

1. Making sure the filling and pressurizing are done from the lowest point and venting from the highest point.
2. Witnessing water overflow through the venting in order to assure that no air bubbles remain in the vessel.
3. Controlling and witnessing pressurizing stages.
4. When 45 minutes elapse, making sure the de-pressurizing is started and the pressure is dropped to the “Inspection Pressure.”
5. Making sure the pressure vessel hydro-static testing pressure calculated correctly.
6. Making sure the vessel is immediately and carefully drained after the test and dried by air.

In this post we learn Hydrotest pressure calculation for pressure vessels and piping.

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ASME B31 was earlier known as ANSI B31. The B31 Code for Pressure Piping, covers Power Piping, Fuel Gas Piping, Process Piping, Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids, Refrigeration Piping and Heat Transfer Components and Building Services Piping.

Piping consists of pipe, flanges, bolting, gaskets, valves, relief devices, fittings and the pressure containing parts of other piping components. It also includes hangers and supports, and other equipment items necessary to prevent over stressing the pressure containing parts. It does not include support structures such as frames of buildings, buildings stanchions or foundations.

B 31.1 – 2001 – Power Piping:

This Code Describe Power Piping.This Code Required to piping for industrial plants and marine applications. This code prescribes requirements for the design, materials, fabrication, erection, test, and inspection of power and auxiliary service piping systems for electric generation stations, industrial institutional plants, central and district heating plants.

The code covers boiler external piping for power boilers and high temperature, high pressure water boilers in which steam or vapor is generated at a pressure of more than 15 PSIG; and high temperature water is generated at pressures exceeding 160 PSIG and/or temperatures exceeding 250 degrees F.

B 31.2 – 1968 – Fuel Gas Piping:

This Code Describe Fuel Gas Piping. This has been withdrawn as a National Standard and replaced by ANSI/NFPA Z 223.1, but B 31.2 is still available from ASME and is a good reference for the design of gas piping systems (from the meter to the appliance).

B 31.3 – 2002 – Process Piping:

This Code Describe Process Piping. Code rules for design of chemical, petroleum plants, refineries, hydrocarbons, water and steam. This Code contains rules for piping typically found in petroleum refineries; chemical, pharmaceutical, textile, paper, semiconductor, and cryogenic plants; and related processing plants and terminals. It prescribes requirements for materials and components, design, fabrication, assembly, erection, examination, inspection, and testing of piping. Also included is piping which interconnects pieces or stages within a packaged equipment assembly.

B 31.4 – 2002 – Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids:

This Code Describe Pipeline Transportation System for Liquid Hydrocarbons and other Liquids. This Code prescribes requirements for the design, materials, construction, assembly, inspection, and testing of piping transporting liquids such as crude oil, condensate, natural gasoline, natural gas liquids, liquefied petroleum gas, carbon dioxide, liquid alcohol, liquid anhydrous ammonia and liquid petroleum products between producers’ lease facilities, tank farms, natural gas processing plants, refineries, stations, ammonia plants, terminals (marine, rail and truck) and other delivery and receiving points.The requirements for offshore pipelines are found in Chapter IX. Also included within the scope of this Code are: Primary and associated auxiliary liquid petroleum and liquid anhydrous ammonia piping at pipeline terminals (marine, rail and truck), tank farms, pump stations, pressure reducing stations and metering stations, including scraper traps, strainers, and proper loops; Storage and working tanks including pipe-type storage fabricated from pipe and fittings, and piping interconnecting these facilities;
Liquid petroleum and liquid anhydrous ammonia piping located on property which has been set aside for such piping within petroleum refinery, natural gasoline, gas processing, ammonia, and bulk plants; Those aspects of operation and maintenance of liquid pipeline systems relating to the safety and protection of the general public, operating company personnel, environment, property and the piping systems.

B 31.5 – 2001 – Refrigeration Piping and Heat Transfer Components:

This Code prescribes requirements for the materials, design, fabrication, assembly, erection, test, and inspection of refrigerant, heat transfer components, and secondary coolant piping for temperatures as low as -320 °F (-196 °C), whether erected on the premises or factory assembled, except as specifically excluded in the following paragraphs.
Users are advised that other piping Code Sections may provide requirements for refrigeration piping in their respective jurisdictions.

This Code shall not apply to:Any self-contained or unit systems subject to the requirements of Underwriters Laboratories or other nationally recognized testing laboratory: Water piping and piping designed for external or internal gauge pressure not exceeding 15 psi (105 kPa) regardless of size; or Pressure vessels, compressors, or pumps, but does include all connecting refrigerant and secondary coolant piping starting at the first joint adjacent to such apparatus.

B 31.8 – 2003 – Gas Transmission and Distribution Piping Systems:

This Code covers the design, fabrication, installation, inspection, and testing of pipeline facilities used for the transportation of gas. This Code also covers safety aspects of the operation and maintenance of those facilities.

B 31.8 S-2001 – 2002 – Managing System Integrity of Gas Pipelines:

This Standard applies to on-shore pipeline systems constructed with ferrous materials and that transport gas. Pipeline system means all parts of physical facilities through which gas is transported, including pipe, valves, appurtenances attached to pipe, compressor units, metering stations, regulator stations, delivery stations, holders and fabricated assemblies.

The principles and processes are applicable to all pipeline systems. This Standard is specifically designed to provide the operator (as defined in section 13) with the information necessary to develop and implement an effective integrity management program utilizing proven industry practices and processes. The processes and approaches within this Standard are applicable to the entire pipeline system.

B 31.9 – 1996 – Building Services Piping:

This Section has rules for the piping in industrial, institutional, commercial and public buildings, and multi unit
residences, which does not require range of sizes, pressures, and temperatures covered in B31.1. This Code prescribes requirements for the design, materials, fabrication, installation, inspection, examination and testing of piping systems for building services. It includes piping systems in the building or within the property limits.

B 31.11 – 2002 – Slurry Transportation Piping Systems:

Rule for design, construction, inspection and security requirements of slurry piping systems. This code
covers piping systems that transport aqueous slurries of no hazardous materials, such as coal, mineral
ores and other solids between a slurry processing plant and the receiving plant.

B 31 G – 1991 – Manual for Determining Remaining Strength of Corroded Pipelines:

The scope of this Manual includes all pipelines within the scope of the pipeline codes that are part of ASME B 31 Code for Pressure Piping, ASME B 31.4, Liquid Transportation Systems for Hydrocarbons,Liquid Petroleum Gas, Anhydrous Ammonia, and Alcohols; ASME B 31.8, Gas Transmission and Distribution Piping Systems; and ASME      B 31.11, Slurry Transportation Piping Systems. Parts 2, 3, and 4 are based on material included in ASME Guide for Gas Transmission and Distribution Piping Systems, 1983 Edition.

This all about is ASME codes for Pipings.

If you are working in the field of fabrication then we have simplified your day to day fabrication activity by developing various calculators so that you can minimize your time and cost of fabrication also increase the accuracy of your fabrication works and improve your workmanships, so let’s try our free apps, Click here for more details…

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