Pipe stress analysis

Uses

Domestic water systems

Pipelines transporting gas or liquid over long distances

Scaffolding

Structural steel

As components in mechanical systems such as:

o Rollers in conveyor belts

o Compactors (E.g.: steam rollers)

o Bearing casing

Casing for concrete pilings used in construction projects

High temperature or pressure manufacturing processes

The petroleum industry:

o Oil well casing

o Oil refinery equipment

Delivery of fluids, either gaseous or liquid, in a process plant from one point to another

point in the process

Delivery of bulk solids, in a food or process plant from one point to another point in the

process

The construction of high pressure storage vessels (note that large pressure vessels are

constructed from plate, not pipe owing to their wall thickness and size).

Design Considerations

Several factors must be taken into consideration when selecting the core pipe best suited to a

particular application, such as:

TEMPERATURE: the operating temperature of the system must be considered to ensure that the

pipe is recommended for operation at the temperature required of it.

THERMAL EXPANSION: there is a considerable variation in the expansion and contraction of the

various pipe types as can be seen from the following table. Changes in the length indicated are

approximate and may vary depending on the actual resin used by a particular pipe manufacturer.

CORROSION RESISTANCE: if the fluid being carried within the pipe is corrosive , the core pipe

must be suitable for the service required.

ABRASION RESISTANCE: in mine tailings and slurry applications, consideration must be given to

the ability of the pipe to withstand the abrasive nature of the tailings being transported. Pre-

Insulated pipes may be flanged at pre-determined intervals to permit the rotation of the tailings

lines, thus increasing the life expectancy of the system.

INTERNAL DIAMETER: it must be noted that there is a considerable difference between the

internal diameters of the various pipe types of similar nominal size. This is especially so in the

higher pressure ratings.

JOINT TYPE: care must be taken to ensure that the correct joint is used for the service required.

Some jointing methods are not recommended for above ground use, while others must be

secured with thrust blocks when buried.

WEIGHT: the weight of the pipe can be an important factor when choosing the core pipe,

especially if transportation to a remote job-site is involved or in bridge crossing applications.

PIPE LENGTH: a compromise between ease of handling on the job and the reduction of the

number of joints must be arrived at when selecting the length of pipe best suited to the particular

application.

INSTALLATION COST: is any special equipment or personnel required for pipe jointing? What is

the time required to complete each pipe joint? Is heavy equipment required to lay the pipes?,

etc. These are all factors which must be considered when estimating the overall installed cost of

the pre-insulated pipe system.

Outer Jacket on Pipe Insulation

Urecon offers several outer jacket alternatives, the choice of a particular outer jacket material

depending on several factors, including:

DURABILITY: is the pipe being buried or is it being exposed to possible mechanical damage

above ground? Is it a mine application where the pipeline may be dis-assembled, moved and re-

installed at another location in the future?

UV RESISTANCE: pipes installed above ground must be resistant to long term UV attack.

BEAM STRENGTH: is the pipe supported only at intervals as in a bridge crossings or pipe rack

applications?

CAESARII Software features Intergraph CAESAR II evaluates the structural responses and stresses of piping systems to international codes and standards. CAESAR II is the pipe stress analysis standard against which all others are measured. CAESAR II analyzes the effects of wind, support settlement, seismic loads and wave loads. Nonlinear effects such as support lift off, gap closure and friction are also included. CAESAR II also selects the proper springs for supporting systems with large vertical deflections. Dynamic analysis capabilities include modal, harmonic, response spectrum and time history analysis.

Static and dynamic analysis

Intuitive analysis model creation

Load and view plant model

Comprehensive error checking

User-definable reports

Wind and wave and seismic and support settlement analysis

International piping codes

Extensive material, steel, and expansion joint and hanger databases

Pipe Supporting Criteria & General Guidelines. Piping system shall be properly supported taking into account the following points: a.) Sustained Loads - Weight of Piping (Bare pipe, service fluid, valves, flanges, jacketting etc) - Weight of Insulation (if any) - Weight of online equipments (if any) - Weight of instruments (if any) - Pressure relief loads due to safety valve operation - Dynamic loads due to pulsating flow/two phase with slug flow

Pressure-Thrust loads in case of expansion joints

b) Occasional Loads Wind/Seismic loads(as and when required) c.) Thermal Loads Thermal loads due to operating/design/steam out/decoking or any other possible abnormal condition.

1) Pipe flange leakage analysis Factors considered in flanged joints analysis

1) Selection and design - Consideration of service conditions ( including external loads, bending moments and

thermal insulation) - Flange rating , type , material ,facing and face finish - Gasket type, material, thickness and design - Bolt material, strength and specifications for tightening of bolts - Design for access to the joint

2) Installation - Condition of flange mating surfaces - Joint alignment and gasket placement before bolt up - Implementation of specified bolting procedures.

2) Trunnion support analysis

Trunnion end plates serve two purposes:

(a) to keep the pipe from slipping off the end and

(2) to keep the end of the neck round under load.

Factors to be considered

1) Type of material of Trunnion and pipe

2) Size of Trunnion and pipe

3) Weight of pipe

4) Shear and bending loads

5) Material Non-Linearity

-The material law should include nonlinear effects (plasticity and strain hardening)since the

material is usually stretched beyond its elastic limit in tubular joints

6) Geometric Non-Linearity

- A large-deformation formulation of the finite element equations has to be adopted tobetter

predict the possibility of buckling of the pipe wall.

7) Fracture Criterion

- Where fracture is a dominant mechanism in the analysis, fracture criterion has to beincluded

to predict better the formation and propagation of the cracks.

3)System such as pump suction-discharge or turbine compressor system Factors to be considered

1) Type of material of pipe, fittings and equipments 2) Sizes of above 3) Support span calculation 4) Type of supports required 5) Analyze system as per the following loads

a.) Sustained Loads - Weight of Piping (Bare pipe, service fluid, valves, flanges, jacketting etc) - Weight of Insulation (if any) - Weight of online equipments (if any) - Weight of instruments (if any) - Pressure relief loads due to safety valve operation - Dynamic loads due to pulsating flow/two phase with slug flow

Pressure-Thrust loads in case of expansion joints

b) Occasional Loads Wind/Seismic loads (as and when required) c.) Thermal Loads Thermal loads due to operating/design/steam out/decoking or any other Possible abnormal condition.