ISO14692 modelling in Caesar II 5.10 (& below)

Since there are growing number of current projects are required to follow ISO14692 in GRE piping analysis, we are still "stuck" with Caesar II 5.10 (&below). Actual release date for C2 V5.20 are still unknown at the moment.

The are ways to "simulate" ISO14692, recommended by Mr Richard Ay (COADE, Inc.) using C2 v5.10 (&below). First, we need to know the major difference between these 2 codes:

1. SIFS are different for bends for piping diameters below 20”. ISO14692 had limit the SIF for Bend and Tee at 2.5 and 2.3 respectively.
2. Failure envelopes for ISO-14692 can be slightly more detailed (and therefore less conservative) often being defined by one more data point (having pentagon shape rather than trapezoid shape).
3. Allowable stress levels may be increased for Operating and Occasional load cases, by 24% and 33% respectively, as compared to Sustained load cases.
4. The “f2” term is excluded from the bending stress in ISO-14692, as opposed to being included in UKOOA. This resulting a slightly increase of Bending Stress in ISO14692.

Then, the "simulation" ways are:
1. Model and analyze the system in CAESAR II using the UKOOA code.
2. Make sure that the checkbox for “Exclude f2 from UKOOA bending stresses” is checked in the Configure/Setup.
3. If you have ISO 14692 failure envelopes, construct a trapezoid that will fully fit within those envelopes, and use those to get the values you need for UKOOA (Sa(2:1) and R).
4. Use a system factor f2 of 0.67.
5. Calculate the bend SIFs as per ISO-14692 and manually enter any of those which significantly differ from those of BS-7159 (which is what UKOOA references).
6. After analyzing your model, compare your Sustained stresses to 100% of the allowable, your Operating stresses to 124% of the allowable, and your Occasional stresses against 133% of allowable.
7. Where joint strengths may govern, you will need to check them manually against the forces from the CAESAR II local force report.

**p.s. From my experience, in step 6, I'll construct 3 types of Failure envelops, based on the size of 124% for operating and 133% for occasional stresses for easy comparison.

There are one more doubt for using ISO14692, is the "pressure stress multiplier, m" for the tee & elbow. The related explanation in ISO14692-3, Annex D.2.2.4 for elbow and D2.3.4 for tee. Both paragraph saying that if the fittings have been qualified according to precedure given in ISO14692-2, the pressure stress multiplier value may set as 1.

Else, there are some default value for bend, and formula to get the mutiplier value.

Pipe Wall Thickness Calculation

This calculation is relative important , piping designer will utilise formular as shown below to determine the suitability of the materials correspond to the project specification and budget. The pipe wall thickness calculation for metallic pipe and fibreglass reinforced pipe will be slightly disimillar due to the inconsistent of materials properties.

The major different between steel pipe and FRP pipe , steel pipe has fixed outer diameter and the increasing of wall thickness will increase upon inward direction. Oppositely, FRP has a fixed internal diameter while the outer diameter is vary depending on thickness was built through winding process.Additional , FRP pipe also need to consider the liner on the outer layers. Due to this factor thus the formula between steel pipe and FRP pipe is different , pleasw refer following formula :



Formula per ASME B31.3 (Typical for Steel Piping )

t = PDi / ( 2FS+ P)

Where ,

t = Wall Thickness

S = Hoop stress ( Hydrostatic Design Stress, obtained from materials catalogue)

Di = Pipe Internal Diameter

P = Internal Pressure ( Design Pressure , obtained from project specification design data)


Modification of ASME B31.3 to determine pipe wall thickness for FRP (Typical for Fibreglass Reinforced Pipe)

t = [P(Di+tL)+2S*tL ]/ (2S - p)

Where,

t =Wall thickness ( Included structural wall thickness and liner )

S = Hoop Stress (Hydrostatic Design Stress, obtained from materials catalogue)

tL= thickness of outer layer ( Liner)

P = Internal Pressure ( Design Pressure , obtained from project specification design data)

Di = Internal Diameter

Together we growth , let us be strong and tough

Ladies and gentlement , try to spend 2 min and 41 sec to watch the video , we should not give up every matter in our's life easily and think everything is possible "Im Possible" . We should live in the life with meaningful and wonderful . Dont give up easily for all piping engineer around the world , fall down and get back up yourself, fail and redo again.

Introduction of Piping Industrial

Piping is a indispendable facilities that exist in every industry such as offshore production unit ,factory ,plants , housing area , ship and so on . The attend of piping is to transmit the fluids or gas from a destination to the others location likes the refinery plants needs the help of piping to carry the crude oil to reach the refinery chamber , the offshore production units required piping to supply the water to heat exchanger and the heavy industrial plant compulsory require firewater system to perform as fire fighting in the case of plant inflamed by fire.

Inasmuch as piping is a vital facilities that occupied in every industrial , it is one of the reason why the piping engineering is remain the high demand in the market as well as the piping engineer. Piping Enginneering basically can categoried into 5 core depatment such as procurement ,design & engineering, pipe stress analysis , production&construction , and lastly is commissioning & maintainence. In order to complete a project perfectly and within the scheduled deadline as well as budget , each the department must have good relationship and collaboration.Either one of the department is playing very important role and none of them can be srewed up or delayed during the project is going on .

Procurement department duty as a buyer or purchaser for the materials and selection of the pipe vendors, this position holding relatively high responsible and required sophisticated knowledge in engineering and good marketing skills. Design & engineering generally is a department to design the piping routing, produce the engineering drawing likes isosmetric drawing , PID , general arragement drawing and overview planning the project flow .Due to the help of PDS or PDMS , the process has been simplify and more precision yet cost effective . Subsequently,Pipe stress department is a room of auditing which mean that pipe stress group duty will verify the flexiblity of the piping system, materials usage , equipments usage , expansion bellow which designed by piping designer and also provide solution to the inflexiblity or potential high stress piping system. Stress engineer is high responsible for any failure occur due to inflexiblity or insufficient pipe support .

Production & constuction will be the department to produce and fabricate the pipe as well as including the spools erection. Produce in the sense that plain pipe milled or supplied from vendors which purchase from procurement department , thereafter fabrication will take placed when the attend of the plain pipe ,the fabrication prcoess is making the spools according to the IFC drawing that provided by engineering disciple.For metallic piping , welding will take place to each joint and must adhere stricty to the welding procedure specification, then after NDT test carry out for each joint to ensure the quality . While for FRP piping ,the fabricated pipe will send to the inhouse for pressuried test with video recorded as envident thenafter the pipe can be ready for delivery to site installation.

The commionsioning is the department that perform hydrotest and leakage check , generally the pipe will be pressuried up to 1.5 times the design pressure . This process will begin when the piping had complete erected and it is the final stage of work for entire project. Lastly, maintenence will be schedule to be done by a cycle of period or if it is requested from site.

Pipe Stress Analysis Introduction

As far as readers concern , I begin my piping career from starting a pipe stress engineer and no doubt the first topic will be touched is on pipe stress analysis. Without going futher , i will brings readers to tour around the reason of we need a pipe stress analysis in piping industrial. Pipe stress analysis is to assure the quality and feasiblity of piping system , a pipe stress analysis is compulsory for every project and generally will be performed by mechanical engineer with at least bachelor degree in mechanical engineering and at least 5 years working experience in piping industrial.

As i mentioned before , stress analysis duty as a auditor to verify the piping system flexibility by checking against with design code . Beside that , also represent as a checker to check the maximum stresses against allowable values to prevent fatigue failure due to cycles of temperature expansion. Also. verify and limit the reaction forces & moments at terminal point and ensure the vertical displacement are within the code allowable. Furthermore , pipe stress engineer also holding the authority to determine the pipe wall thickness , selection of expansion bellow ,selection of equipments , selection pump and so on. Before selection of this heavy equipment , pipe stress engineer shall carry out an overall research and study before the conclusion is confirmed , this process involved a lot calculation and varies angle of consideration. In conclusion, i can say that pipe stress job look easy but high responsible , as a pipe stress engineer must be aware of the calculation , a single careless mistake may loss million dollars of money.

From where can we learn pipe stress analysis ? i can suggest the fresh graduate or engineer without piping knowledge to look for famous engineering consultancy such as Technip , Aker Kvaerner , Worley Parkson ,Foster Wheeler , CB&I and otherwise look for FRP pipe vendors because according code ISO 14692 , stress analysis for FRP shall performed by pipe vendor. The list of company provide sufficient information for a fresh graduate to gain the basic concept of piping and pipe stress philopsophy . Mastering the design code will be the 2nd options to improve the pipe stress knowledge , please find the ASME code as below may help much on improving for piping knowledge .From my personal recommendation , mastering code ASME B31.3 is more than enough for oil and gas industrial.

1. ASME B31.1 Power Piping
2.ASME B31.3 Process Piping ( Widely used in chemical and refinery plant )
3.ASME B31.4 Liquid Transportation Piping
4.ASME B31.8 Gas Transportation Piping
5.ASME Section III, Nuclear Components Design

The advance of the technology has accelerate the evolution of composite piping such Fibreglass Reinforced Pipe (FRP) as a result numbers of steel line today has been widely replaced by FRP pipe due to their reliablity , corrosion-free , simple installation , light in weight and etc. The lines such as Firewater , drain line , sewage water line , service water line has been replaced by FRP piping instead of metallic . The major between steel pipe and FRP pipe is steel pipe is isotropic materials (Having identical value of property in all crystallographic direction) while FRP pipe is anisotropic(Property vary systematically depending on the direction either hoop or axial) materials . Inasmuch as it happen slightly different in the calculation thus when dealing with FRP piping is recommended to refer the design code as follow :

1. BS 7159
2.UKOOA
3.ISO 14692

Summary of the chapter

Objective of pipe stress analysis to :

1.Ascertain the pipe support location.
2.Check the reaction force and moments at each support location or nozzle or terminals point.
3.Check the vertical displacment against the code allowable.
4.Check the flexibility of the piping between nozzle to the equipments.
5.Ensure the piping has enough flexibility to expand.
6. Compare the stresses result against the allowable code stress.
7. Verify the usage of appropriate equipments.
8. Identify the high forces, bending moments , overstress location and propose solution in order to maintain
system flexibility.