The Canadian Pipe Stress Analysis Design Manual for Owners, Engineers and Contractors

The Canadian Pipe Stress Analysis Design Manual for Owners, Engineers and Contractors for a premium piping engineering & full-service pipe design and pipeline / pipe stress analysis services across Canada & globally. Using CAESAR II and pipe stress calculations as per API, ASME B31.3, B31.1, B31.8, B31.4, CSA Z662.


The Canadian Pipe Stress Analysis Design Manual for Owners, Engineers and Contractors
The Canadian Pipe Stress Analysis Design Manual for Owners, Engineers and Contractors

Index:

1. GENERAL

2. DRAWING DISTRIBUTION AND PROCEDURES

3. INITIAL PIPING STUDIES

4. STRESS RELIEVED VESSELS AND PIPING

5. REVIEW OF CRITICAL PIPING

5.1 Pumps

5.2 Compressors

5.3 Turbines

5. 4 Airfans

5.5 Heaters

5.6 Buried Piping

5.7 Cryogenic & Low Temperature Piping

6. STANDARDIZATION OF APPROACH TO PIPING PROBLEMS

6.1 Allowable Pipe Spans

6.2 Allowable Pipe Overhang

6.3 Pipe Guide Spacing

6. 4 Instrument Strong Back Flexibility

6.5 In-Line Pumps

6.6 Expansion Loop Design

6.7 Pipe Anchors

6.8 Stacked Exchangers

6.9 Off Plot Pipeways

7. MISCELLANEOUS AND SPECIAL PROBLEMS

7.01 Slug Flow

7.02 Mitered Elbows

7.03 Tee Connections

7.04 Injection Connections

7.05 Heater Coil Decoking

7.06 Catalyst Regeneration

7.07 Reformer Furnace Pigtail Design

7.08 Cold Spring

7.09 Blowdown Systems

7.10 Field Checkout

7.11 Soot Blowers

7.12 Settlement and Frost Heave

7.13 Ambient Temperature Effect on Bare Piping

7.14 Control Valve Piping

7.15 Hydrotest of Large Low Pressure Piping

7.16 Pipe Supports

7.17 Tank Field Piping

7.18 Steam Trace and Steam Trap Piping

7.19 Plastic Piping

7.20 Rotations, Reactions and Stresses at Nozzle Connections to Vessels

7.21 Bowing of Pipe

7.22 Compressor Bottle Support

7.23 Tank Nozzle Movements Due to Pressure and Temperature

8. PIPING STRESS ANALYSIS WORK CHECK LIST


1. GENERAL


1.1 This Design Guide is intended to aid stress personnel / Piping Stress Engineer in following approved procedures and techniques to complete their work (Pipe Stress Analysis) on an assigned project.


1 .2 Although it is recommended that the standards be followed closely, individual thought and sound engineering judge­ment must be used at all times.


1.3 In reviewing piping isometrics, models or drawings, the Pipe Stress Analysis Engineer should keep in mind that the aesthetic de­sign of the piping systems is the responsibility of the piping design groups and therefore he should review them from a stress and support standpoint only. Exceptions to the above should only be made when a situation ridiculously improper or a large economic saving is involved, keeping in mind lost time in making revisions and their affect on schedules.


1 .4 All piping systems reviewed by the Piping Stress Analysis Group shall be considered for all the "Design Conditions" as listed under Section 301 of the Code for Pressure Piping ANSI B31 .3, latest revision, or other applicable codes. As a general rule most computer analyses of piping should include only the effects of thermal expansion, restraints and effects of support, anchor and terminal movements. Effects of dead load on a well supported system are generally small. Other effects are to be studied by special calculations only when engineering judgement deems them to be possibly severe.


2. DRAWING DISTRIBUTION & PROCEDURES


The following normal procedures may be adjusted for particular projects or office locations to suit the special conditions and requirements of those projects and locations.

2.1 The assigned Piping Stress Analysis Engineer shall confer with the Pressure Vessel Job Supervisor and indicate his preference of draw­ings which should be distributed to him. These drawings should generally be plot plans, P&ID's, paving and grading, underground piping, pipe way stanchions, line designation tables, basic data, flow diagrams, piping drawings and piping isometrics. When vessel drawings and structural drawings are included, the filing of drawings becomes a major problem. In fact, much filing would be avoided if P&ID's and paving grading drawings were not included. This judgment is left to each individual.


2.2 The routing of piping isometrics between the Plant Design Group and the stress group has been standardized to increase efficiency of all groups concerned and to reduce the amount of paper handling. Isometrics will be referred to as iso's in further discussions. The presently adopted procedure for iso distribution on modelled jobs is:


a) After isometrics are drawn up and checked within the Plant Design Group and are ready to issue for construction, a print of each together with a transmittal list shall be sent to the Pipe Stress Analysis Engineer one week before date to be issued for construction.


b) The Piping Stress Analysis Engineer then places a design data stamp on all iso's except those which can be approved for stress by inspection without specific design data. The stamped iso's should then be filled in with the necessary design data from piping specifications and line design tables. An efficient and acceptable method of recording the expansion temperatures is to prepare a list of maximum "exp" temperatures for each particular service as shown in the Line Designation Table, i.e.:


IA (instr. air)--------100°F

UA (util. air)--------100°F

N (nitrogen)--------100°F

DW (drinking water)--------100°F

PW (potable water)--------100°F

RW (raw water)--------100°F

CW (cooling water)--------120°F

LS (low press. steam)----40# sat stm temp.

MS (med press. steam)-150# sat stm temp

HS (high press. steam)-600# sat stm temp


But process lines require individual temperature assignment from the line tables.

Likewise, a list can be prepared for pipe specifications which are repeated often that are of carbon steel and the same schedule. Alloy spec.'s and their schedules should be specially listed for ease of identification.


c) The iso's are then reviewed at the models and passed by judgment as much as possible, leaving only a few to verify by computer calculation. All iso's passed by inspection should be marked up with support designations during the review of each iso. This in general will be the most efficient operation except where a group of iso's must be immediately released by the Plant Design Group for prompt delivery to the fabricator to meet a schedule. After all the iso's listed on a particular transmittal have been reviewed, those which can be field-supported, or require no supports, or which can be supported by wholly standard support details, are indicated on the transmittal and the blue print of the iso itself with the designations FTS, NS or STD respectively. The Plant Design Group can stamp the original iso's accordingly without need of their passing through the pipe support groups. Technicians, will be retained by The Plant Design Group for the purpose of assigning proper designations to the "STD" supports required on every iso. This should expedite the preparation of iso's to be issued for construction on the Rev. 0 issue. All other iso's are checked off on the original transmittal as being approved for stress with an engineered support designation ES except where a flexibility change or calculation is needed. The symbol HFS indicating "Hold For Stress" will be tagged on the transmittal opposite the iso involved. Two copies of the trans­mittal with the above notations should then be given to the Plant Design Supervisor.

d) All iso's as they are approved by the Pipe Stress Analysis Engineer, should be initialed on the tracing by the Pipe Stress Analysis Engineer or his designated alternate. Where iso's require a calculation, the tracing should be detained by the Plant Design Group until the Piping Stress Analysis Engineer finalizes his study of them. The Piping Stress Analysis Engineer should assign the highest priority to finalizing these iso's.

e) When iso's are verified as satisfactory by calculation, the Plant Design Group should be immediately notified for its release. And if iso's require a revision, the print should be marked up with the required change and a copy of the print should be given to the plant Design Group. After the iso revisions have been made, a new print should be again issued to the Pipe Stress Analysis Engineer for final review. If the iso is correct the Pipe Stress Analysis Engineer will initial the tracing as approved.

f) All prints marked up by the Piping Stress Analysis Engineer with the support require­ment symbol £S are then turned over to the Support Group. If iso's are stamped for review of critical support details, the pipe support designer must return the iso and support details to the Piping Stress Analysis Engineer who, upon approval of the detail, initials the stamped area on the iso.

g) The Support Group then adds the "PS" numbers and locations to the iso tracing and initials the tracing. The tracing is then returned to the Plant Design Supervisor for issue.

h) If after an iso is issued for construction, the Plant Design Group makes a revision to the piping, it is the responsibility of the Plant Design Supervisor to stop the support group from further work on the iso and reclaim the print marked up by the Pipe Stress Analysis Engineer. The Piping Supervisor then reissues the iso and the originally marked up print to the Pipe Stress Analysis Engineer who reviews the iso for further approval and support mark-up. Where piping revisions are judged insignificant by the Plant Design Supervisors, (i.e. not affecting flexibility or support of the system) the iso is then just reissued for construction, by-passing the Stress Group.

i) If piping isometric numbers are revised by the Plant Design Group, a cross reference list of new numbers versus old numbers must be provided to the Stress Group to keep records straight. To keep better control of iso's marked up by the Stress Group, the Plant Design and Support Groups should also keep a check list of iso's received.

j) The stress markups are then kept in alphabetical and numerical order in special long binders by the Ripe Support Group for reference.

k) When the job is complete the marked isometrics are returned to the Piping Stress Analysis Engineer who keeps them close at hand for approximately 1 year, then files them in storage.


2.3 A sepia of all orthographic drawings of piping on-plot or off­ plot should be issued to the project Pipe Stress Analysis Engineer prior to being issued for construction. The sepia shall be stamped and distributed per owner's standards upon stress review completion. The Piping Stress Analysis Engineer shall convert sepias of the piping drawings into stress STR drawings and maintain a drawing control of all STR drawings per Owner's standards.


3. INITIAL PIPING STUDIES


3.1 Study preliminary plot plan and pipe way layouts for troublesome arrangements.


a) Indicate pump placements which will aid in achieving flexible piping arrangements. Avoid placing pumps directly opposite connecting equipment.

b) Estimate the number and position of pipe way expansion loops for steam, condensate and other long, high-temperature systems.

c) Keep movements in steam lines to generally 4 inches or a maximum of 6 inches by judicious number and location of loops. Determine the loop size to help in positioning the header in the pipe way to avoid large overhangs or the necessity of auxiliary means of supporting loops. Design /rests of loops as early as possible and give exact layout to Plant Design Group. Expansion movements, insulation thickness, effect of cold spring and extra clearance should all be included. Generally keep a minimum of 1^ to 2" extra clearance from adjacent piping or other obstructions for worst case of design temperatures or differential pipe movements.


3.2 Review preliminary alloy piping isometrics or layouts by inspec­tion for material commitment. Generally this is done to avoid large differences between material commitment and final purchase of alloy pipe and fittings required; therefore, an exact analysis should not be made. Retain the preliminary study for comparison with the final iso to be issued-for-construction At this time many iso's can still be passed for stress by inspection, but it is recommended that piping to pumps, compressors and possibly heaters, exchangers or reactors when high reactions are suspected, should be run as a formal calculation on the computer.


4. STRESS RELIEVED VESSELS AND PIPING


4.1 The Pressure Vessel Job Supervisor will provide a list of all stress relieved vessels on the job and all established dates from the fabricator for stress relief of each particular vessel. These dates will be marked on tags put on the vessel models by the vessel department. Normally the model should be completed and "checked" a minimum of (6) weeks ahead of the stress relief date. This gives the Pipe Stress Analysis Engineer and support group (2) weeks to complete their work and get details sent to the fabricator(4) weeks prior to actual stress relief.


4.2 It is very important that the Plant Design Supervisor remind all his designers that the piping should not be revised thereafter. If the change must be made, the revision has to be coordinated with the vessel fabricator immediately to avoid serious problems such as re-stress relieving and delay in delivery.