Canadian Common Practice in Piping Design and Pipe Stress Analysis

1. Introduction

1.1. Definition of Piping

1.2. Piping Nomenclature & Components

1.3. Regulatory Acts, Codes & Standards

1.4. Line Designation Tables

1.5. Important Questions

2. Codes & Standards

2.1. ASME

2.2. NEPA / NFC / NFPA

2.3. CSA

2.4. MSS

2.5. API

2.6. ASTM

3. Supplemental Documents

3.1. Owner’s Specifications & Documents

3.2. Contractor’s Standards & Documents

4. Piping Design

4.1. Failure Mechanisms

4.2. Code Considerations for Design

4.3. Material Selection

4.4. Fabricated Tees & Area Reinforcement

4.5. Piping Flexibility Analysis

1.0 Introduction

1.1 Definition of Piping

Pipe is a pressure tight cylinder used to convey a fluid or to transmit a fluid pressure, ordinarily designated pipe in applicable material specifications. Materials designated tube or tubing in the specifications are treated as pipe when intended for pressure service.

Piping is an assembly of piping components used to convey, distribute, mix, separate, discharge, meter, control or snub fluid flows. Piping also includes pipe-supporting elements but does not include support structures, such as building frames, bents, foundations, or any equipment excluded from Code definitions.

Piping components are mechanical elements suitable for joining or assembly into pressure-tight fluid containing piping systems. Components include pipe, tubing, fittings, flanges, gaskets, bolting, valves and devices such as expansion joints, flexible joints, pressure hoses, traps, strainers, in-line portions of instruments and separators.

Piping is typically round.


1.2 Piping Nomenclature, Components

Piping Nomenclature, Components by meena rezkallah, p.eng. the best piping stress engineer

Graphic of piping system illustrating

  • header

  • branch connection

  • valve

  • flange

  • expansion joint

  • expansion loop

  • pipe support

  • reducer

  • elbow

1.3 Regulatory Acts, Codes & Standards

Codes

Codes are rules for the design of prescribed systems which are given the force of law through provincial, state and federal legislation. In Canada, provincial governments have the responsibility for public safety which includes these facilities, among others:

  • Pressure piping

  • Pressure vessels

  • Boilers

  • Pipelines

  • Plumbing systems

  • Gas piping

Alberta Safety Codes Acts and Codes of Practice

The following are applicable to the first four facilities listed above.

Boilers and Pressure Vessels Regulation

  • Prescribes requirements for registration of pressure vessels, boilers, pressure piping and fittings

Design, Construction and Installation of Boilers and Pressure Vessels Regulations

  • Cites the codes and “bodies of rules” that form part of the regulations

  • CSA B51 Boiler, Pressure Vessel and Pressure Piping Code

  • CSA B52 Mechanical Refrigeration Code

  • CAN/CSA Z184 Gas Pipeline Systems

  • ASME Boiler & Pressure Vessel Code

  • ASME B31 Pressure Piping Codes

  • B31.1 Power Piping

  • B31.3 Process Piping

  • B31.4 Liquid Transportation Systems for Hydrocarbons, Liquid Petroleum

  • Gas, Anhydrous Ammonia and Alcohols

  • B31.5 Refrigeration Piping

  • ANSI K61.1 Safety Requirements for the Storage and Handling of Anhydrous

  • Ammonia

  • NFPA 58 Standard for the Storage and Handling of Liquefied Petroleum

  • Gases

  • DOT Regulations of the Department of Transportation Governing the

  • Transportation of Hazardous Materials in Tank Motor Vehicles

  • MSS Standard Practice SP 25 Standard Marking System for Valves, Fittings,

  • Flanges and Unions

  • TEMA Standards of Tubular Exchanger Manufacturers Association

Pipeline Act

Cites the “minimum requirements for the design, construction, testing, operation,

maintenance and repair of pipelines”:

  • CAN/CSA Z183 Oil Pipeline Systems

  • CAN/CSA Z184 Gas Pipeline Systems

  • CSA Z169 Aluminum Pipe and Pressure Piping Systems

  • Canadian Petroleum Association Recommended Practice for Liquid Petroleum

Pipeline Leak Prevention and Detection in the Province of Alberta

Currently, CSA Z662 Oil and Gas Pipeline Systems

(This standard supersedes Z183 & Z184)


In the US:

As in Canada, some facilities are governed by federal regulations. Interstate pipeline

facilities are defined by the:

  • Code of Federal Regulations, Title 49

  • Part 192 Transportation of Natural and Other Gas by Pipeline – Minimum Federal Safety Standards

  • Part 193 Liquefied Natural Gas Facilities

  • Part 195 Transportation of Hazardous Liquids by Pipeline

Other pipeline pressure piping codes include:

  • ASME B31.4 Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

  • ASME B31.8 Gas Transmission and Distribution Systems


1.4 Line Designation Tables

The Province of Alberta Safety Codes Act "Design, Construction and Installation of Boilers & Pressure Vessels Regulations" par 7(2) requires that construction of a pressure piping system must include submission of drawings, specifications and other information and include:

  1. flow or line diagrams showing the general arrangement of all boilers, pressure vessels, pressure piping systems and fittings

  2. pipeline identification lists showing the maximum pressures and temperatures for each pressure piping system

  3. a list of pressure relief devices, including the set pressure

  4. material specifications, size, schedule and primary service rating of all pressure piping and fittings

  5. the welding procedure registration number

  6. the pressure pipe test procedure outlining the type, method, test media , test pressure, test temperature, duration and safety precautions

  7. a form, provided by the Administrator, completed by the engineering designer or contractor which relates to the general engineering requirements for design and field construction of pressure piping systems

  8. such other information as is necessary for a safety codes officer to survey the design and determine whether it is suitable for approval and registration


1.5. Important Questions

  1. Which Act governs the design of plant pressure piping systems in Alberta?

  2. Are process plant water lines considered pressure piping systems?

  3. For what fluid service category may a hydro test be waived per B31.3?

  4. What is the difference between a pipe elbow and a bend?


2.0 Codes and Standards

The following codes are used for the design, construction and inspection of piping systems.


2.1 The ASME B31 Piping Codes

Piping codes developed by the American Society of Mechanical Engineers:


B31.1 Power Piping

Piping typically found in electric power generating stations, in industrial and institutional plants, geothermal heating systems and central and district heating and cooling plants.

B31.3 Process Piping

Piping typically found in petroleum refineries, chemical, pharmaceutical, textile, per, semiconductor and cryogenic plants and related processing plants and terminals.

B31.4 Pipeline Transportation Systems for Liquid Hydrocarbons and Other Liquids

Piping transporting products which are predominately quid between plants and terminals and within terminals, pumping, regulating, and metering stations.

B31.5 Refrigeration Piping

Piping for refrigerants and secondary coolants.

B31.8 Gas Transportation and Distribution Piping Systems

Piping transporting products which are predominately gas between sources and terminals including compressor, regulating and metering stations, gas gathering pipelines.

B31.9 Building Services Piping

Piping typically found in industrial, institutional, commercial and public buildings and in multi-unit residences which does not require the range of sizes, pressures and temperatures covered in B311.1

B31.11Slurry Transportation Piping Systems

Piping transporting aqueous slurries between plants and terminals within terminals, pumping and regulating stations.


The following codes are used to specify the geometric, material and strength of piping and components:


ASME B16 Dimensional Codes

The ASME B16 Piping Component Standards

ASME B36 Piping Component Standards

Other ASME or ANSI

2.2 NEPA Codes

National Electrical Protection Association

Piping covering fire protection systems using water, carbon dioxide, halon, foam, dry chemical and wet chemicals.

NFC - NFPA Codes

National Fire Code / National Fire Protection Association

NFPA 99 Health Care Facilities

Piping for medical and laboratory gas systems.


2.3 CSA Standards

Canadian Standards Association

CSA Z662 Oil & Gas Pipeline Systems

This standard supersedes these standards:

  • CAN/CSA Z183 Oil Pipeline Systems

  • CAN/CSA Z184 Gas Pipeline Systems

  • CAN/CSA Z187 Offshore Pipelines

2.4 MSS Standard Practices

These are piping and related component standards developed by the Manufacturer’s Standardization Society. The MSS standards are directed at general industrial applications. The pipeline industry makes extensive use of these piping component and quality acceptance standards.

2.5 API

American Petroleum Institute

The API standards are focused on oil production, refinery and product distribution services. Equipment specified to these standards are typically more robust than general industrial applications.

2.6 ASTM

ASTM

There are numerous American Society for Testing and Materials designations cover the specification of wrought materials, forgings and castings used for plate, fittings, pipe and valves. The ASTM standards are directed to dimensional standards, materials and strength considerations.

Some of the more material standards referenced are:

3.0 Supplemental Documents

3.1 Owner’s Specifications & Documents

Many of the Owners in the industries we service are technically sophisticated and will often have supplementary specifications, standards or practices. It is the intent of these documents to clarify and provide interpretation of the legislated Codes and industry accepted standards specific to the Owner’s facilities.

These specifications typically go beyond the requirements of Codes and without exception do not contravene a Code requirement.

3.2 Contractor’s Specifications & Documents

The engineering contractor and may be called upon to provide the engineering specifications for a project if an Owner does not have his own standards or if required by terms of the contract.


4.0 Piping Design

Piping design deals with the:

  • analytical design

  • material selection

  • geometric layout

  • fabrication

  • inspection specification

  • component specification

of piping and piping components.


4.1 Failure Mechanisms

Piping and piping components may fail if inadequately designed, by a number of different mechanisms. These failures, in the majority of cases are either load controlled or displacement controlled failures.

  • Pipe rupture due to overpressure

  • Bending failure in pipe span

  • Elbow cracking after 10 years of service, 5000 cycles of heat up to 500 F

  • On heat up, a line comes into contact with adjacent header which is at ambient temperature

  • During startup on a cold winter day in Grande Prairie, an outdoor gas line located above grade and constructed to Z662 is suddenly subjected to full line pressure and ruptures.

  • A 12” Sch.40 header, bottom supported, 40 feet long runs vertically up a tower and connects to a nozzle. On steam out of the vessel, a 1’ deflection is observed in the pipe and remains after the steam out procedure is completed and the pipe returns to ambient temperature.

  • A header of a reciprocating compressor has been stressed checked; during operation vibration is observed in the line. During the unit turnaround, cracking is found at midspan in the wrought piping material.

  • A stress check determines that a hot, high alloy line does not pass the flexibility requirements per B31.3. Twenty-five cycles are expected over the lifetime of the line.

4.2 Code Considerations for Design

Design of piping systems is governed by Codes. All codes have a common theme, they are intended to set forth engineering requirements deemed necessary for safe design and construction of piping installations.

The Codes are not intended to apply to the operation, examination, inspection, testing, maintenance or repair of piping that has been placed in service. The Codes do not prevent the User from applying the provisions of the Codes for those purposes.

Engineering requirements of the Codes, while considered necessary and adequate for safe design, generally use a simplified approach. A designer capable of applying a more rigorous analysis shall have the latitude to do so, but must be able to demonstrate the validity of such analysis.

Design Conditions

Design conditions refer to the operating and design temperature and pressure that the piping system will operate at over the course of its design life.

Code Design Temperature & Design Pressure

Read more:

  1. ASME B31.8 VS CSA Z662

  2. ASME B31.4 VS CSA Z662

  3. ASME B 31.1 & ASME B 31.3 CODE COMPARISON

  4. ASME B31.3 (Power Piping) VS ASME B31.3 (Process Piping)