Recent Posts

Water Pumping Station Piping Stress Analysis using Flexible Sleeve Coupling

Written by Anup Kumar Dey in Caesar II,Piping Stress Analysis

A large number of Piping failures in Very Large Diameter Water pump piping systems forced client companies to consider water pump station piping as a critical system. Pump station piping is normally very compact due to space constraints and the possibility of including any inherent piping flexibility by adding elbows is limited. At the same time, the Very Large size (diameter) of the suction and discharge piping makes the system highly rigid. In this scenario, piping stress engineers are left with only two options to qualify the pump suction and discharge nozzles.

  1. Using Expansion Joint
  2. Using Flexible Sleeve Couplings

Both methods provide flexibility in the system and are highly effective in absorbing thermal movements in the system.

But The main drawback with Expansion Joints is their high cost with respect to design life and the requirement of additional standby expansion joints. So in recent times, design consultancies are using Flexible Sleeve Couplings to a large extent. Compared to the expansion joints, flexible sleeve couplings are economic for their design life.

In this article, We will describe the stress analysis of a Water Pump Station Piping employing Flexible Sleeve Couplings. Hexagon PPM software Caesar II is used for analysis.

Flexible Sleeve Coupling
Fig. 1: Flexible Sleeve Coupling

What is a Flexible Sleeve Coupling?

The Flexible Sleeve coupling (Fig. A) comprises a center sleeve located between two end rings. The sleeve and end rings are separated by wedge-shaped elastomeric gaskets. The tightening of the head bolts draws the end rings together, thus compressing the gaskets between the end rings and the center sleeve. As the gasket is forced onto the pipe surface, an effective leak-proof seal (Fig. B) is achieved. Such flexible couplings are capable of absorbing thermal expansion and contraction removing the need for expansion bellows (Fig. C).

Additionally, it has the ability to accommodate enough angular deflection to allow for pipeline movement or ground settlement, or to provide for long radius curves without the necessity of incorporating purpose-made bends (Fig. D).

Stress Analysis System Definition

The Stress Analysis system consists of a Water Pump station consisting of four pumps and two future tie-ins. The line parameters are given below for reference:

Pump suction and discharge side line parameters
Fig. 2: Pump suction and discharge side line parameters.

Data required from the Vendor

The following data need to be collected from the Vendor

  • Flange and Valve weights.
  • SIF values at branch connections.
  • Pump GA drawing with Nozzle Allowable loads.

Modeling the Stress system

Refer to Fig. 3 to visualize the complete system.

Water Pump Station Piping under Consideration
Fig. 3: Water Pump Station Piping under Consideration

The Governing code for the system is ASME B31.4. Pipe elements are modeled in the same conventional way. A fixed anchor is considered at the interconnection of buried and aboveground parts for the discharge header. The pump is modeled as rigid with zero weight.

The piping pressure thrust force is calculated as Pressure X Internal Cross-Sectional Area and added in direction changes.

Modeling the Flexible Sleeve Coupling in Caesar II

  • In Caesar II, the sleeve coupling (Fig. 4) is modeled as an expansion joint with very low stiffness values.
  • Effective ID is left blank as the sleeve coupling is used with a harness (tie rod) so no need to calculate coupling thrust force.
  • Axially a displacement of 20 mm is considered as the coupling can absorb a displacement up to 20 mm (Need to be checked with the vendor on a case-to-case basis).
  • An all-around guide is provided on both sides of the sleeve coupling at the nearest possible distance from the coupling.
  • Refer to Fig. 4 for more details.
  • The Flexible sleeve coupling (Fig. 5) is modeled by elements 6620-6630; 6620-6640; At nodes 6580 and 6660 all-around guides are provided to avoid bending of the coupling. At node 6630 a 20 mm displacement is provided for axial movement.
Modeling of Flexible Sleeve Coupling in Caesar II
Fig. 4: Modeling of Flexible Sleeve Coupling in Caesar II
Typical harnessed flexible sleeve coupling
Fig. 5: Typical harnessed flexible sleeve coupling

Load Cases for Analysis

Load cases are prepared considering 3 pumps as operating and one pump as stand-by. Refer to Fig. 6 for the analysis load cases. Seismic loads are considered to act in any single direction.

Load cases considered for analysis
Fig. 6: Load cases considered for analysis

Few more Useful Resources for You..

Stress Analysis Basics
Stress Analysis using Caesar II
Stress Analysis using Start-Prof
Piping Design and Layout basics
Piping Materials Basics

Importing an Autodesk REVIT model into Piping Stress Analysis Software START-PROF

Written by Alex Matveev in Piping Stress Analysis,Start-Prof

What is Autodesk REVIT

Autodesk REVIT is modeling software used mainly by Mechanical, Civil, Architectural engineers and designers. It offers a collaborative and multi-disciplinary approach for design and construction projects. Using this software, Engineers can produce a detailed model of plants, buildings, and infrastructure. REVIT offers features of work-sharing between interface disciplines and saving the work. It helps project teams to reduce costs and achieve better outcomes.

The Stress Analysis Software PASS/START-PROF provides an import feature so that the model can be directly imported into PASS/START-PROF and can be used as analysis input. This feature not only helps in reducing modeling time but also removes man-made modeling errors completely.

This video shows, how to import a piping model from Autodesk REVIT into PASS/START-PROF Piping Stress Analysis Software.

Import Autodesk REVIT

What is PASS/START-PROF

PASS/START-PROF is a part of the powerful and integrated PASS Suite:

  • PASS/START-PROF for piping system stress analysis of any size and complexity
  • PASS/EQUIP for pressure vessel design and analysis
  • PASS/HYDRO SYSTEM for piping systems fluid flow analysis of any size and complexity
  • PASS/NOZZLE-FEM for nozzle flexibility and stress analysis, SIF and k-factor calculation for tees not covered by ASME B31 codes (lateral, D/T>100, etc.)

Methods for Importing Autodesk REVIT into PASS/START-PROF

Export from Autodesk REVIT can be performed using a special plug-in for Autodesk REVIT. Export can be done in two steps:

  1. Select Revit to START-PROF plugin, select piping, export into START-PROF neutral format file
  2. Open START-PROF and open neutral format file

Video Tutorial to Import Autodesk REVIT Model into PASS/START-PROF

Few more useful Resources for You..

Stress Analysis using Start-Prof
Stress Analysis Basics
Stress Analysis using Caesar II
Piping Design and Layout Basics
Piping Materials Basics

How to import an AVEVA E3D or PDMS model into START-PROF Piping Stress Analysis Software

Written by Alex Matveev in E3D,PDMS,PDMS-E3D,Start-Prof

What is AVEVA E3D

E3D and PDMS are some of the frequently used plant design software developed by AVEVA.

The Stress Analysis Software Start-Prof provides import and export features that are included in standard software packages with no extra charge. Along with reducing modeling time, this feature helps in removing the man-made modeling errors completely.

This video tutorial shows the step by step procedures to import a piping model from AVEVA E3D or PDMS software into PASS/START-PROF Piping Stress Analysis Software.

Import from E3D to Start-Prof

What is PASS/START-PROF

PASS/START-PROF is a part of the powerful and integrated PASS Suite software module which is used for piping stress analysis.

Methods for Importing AVEVA E3D or PDMS Model into PASS/START-PROF

A special plug-in is available for AVEVA E3D and PDMS that allows the import of piping models and partially export of data back to AVEVA. The plugin is free and included in the standard START-PROF package.

Export and import can be done in three steps:

  1. Run START-PROF and AVEVA E3D or PDMS on the same machine
  2. Select the piping branches in AVEVA E3D or PDMS and click export to START-PROF. The model will be automatically created in START-PROF
  3. Modify the model in START-PROF and click Import changes from START-PROF in AVEVA E3D or PDMS. The changes will be imported back

Video Tutorial to Import AVEVA E3D or PDMS model into START-PROF

This video was provided by Modelosoft company, the PASS/START-PROF and AVEVA dealer in Mexico.

Few more Resources for You..

Piping Stress Analysis using Start-Prof
Piping Stress Analysis Basics
Piping Stress Analysis using Caesar II
Tutorials related to Piping Design Software

How to import a CADWorx model into START-PROF Piping Stress Analysis Software

Written by Alex Matveev in PDMS-E3D,Piping Stress Analysis,Start-Prof

What is CADWorx

CADWorx is one of the frequently used plant design software developed by Hexagon. It creates a semi-intelligent model using a specification based application.

Since this software is widely used for plant design, creating an interface with CADWorx with START-PROF is highly beneficial. The Stress Analysis Software Start-Prof provides an import feature so that the model can be directly imported into Start-Prof and can be used as analysis input. This feature not only helps in reducing modeling time but also removes man-made modeling errors completely.

This video shows, how to import a piping model from CADWorx into PASS/START-PROF Piping Stress Analysis Software.

Importing Piping Model from CADWorx to START-PROF

Features of Start-Prof

PASS/START-PROF enabling new users to perform piping systems analysis of any size or complexity in days rather than months. In PASS/START-PROF users can start working immediately, with minimal experience. Companies can put PASS/START-PROF into application immediately after purchase, significantly reducing costs in time saved without compromising on the quality of end results. Even a beginner can deliver good quality pipe stress analysis using PASS/START-PROF with minimal training and guidance.

In PASS/START-PROF, since you will be working with a modern object model, everything is easy and straightforward. Creating piping components like a pipe, bend, reducer, cap, tee, expansion joint, restraint, valve, flange, etc are very simple. Perfect Node numbering as found in other stress analysis software will not bother you. Modifying the created model using copying, rotating, mirroring, node renumbering, cut, copy, paste functions from menubar is quite easy.

Method-1: Importing CADWorx Model into Start-Prof using PCF file

There are several methods of how to import the CADWorx model. In this video, we will show the first method using the PCF file.

Export can be done in three steps:

  • Select the piping in CADWorx and export it into PCF file
  • Open PASS/START-PROF and convert PCF file into CTP file
  • Open CTP file in START-PROF

Video Tutorial to Import CADWorx Model into START-PROF: Method 1-Using PCF File

This video was provided by AECSoft company, the PASS/START-PROF dealer in China.

Method-2: Importing CADWorx Model into Start-Prof using Caesar II Neutral file

There are several methods of how to import the CADWorx model. In this video, we will show the second method using the CAESAR II Neutral Format File.

Export can be done in three steps:

  1. Select the piping in CADWorx and export it into CAESAR II
  2. Convert CAESAR II file into neutral format file
  3. Open neutral format file using PASS/START-PROF

Video Tutorial to Import CADWorx Model into START-PROF: Method 2-Using Caesar II Neutral File

This video was provided by AECSoft company, the PASS/START-PROF dealer in China.

Few more Resources for You..

Piping Stress Analysis using Start-Prof
Piping Stress Analysis Basics
Piping Stress Analysis using Caesar II
Tutorials related to Piping Design Software

Heat Exchanger Modeling in Caesar II and Stress Analysis

Written by Anup Kumar Dey in Caesar II,Piping Stress Analysis,Piping Stress Basics

Shell and Tube heat exchangers are frequently used in Oil & Gas, Power plants, Refineries, and Chemical and Petrochemical industries. As piping systems connected to such equipment are considered Critical, piping stress engineers need to model it quite frequently.  But sometimes, specifically for new stress engineers, the modeling steps seem to be very difficult. In this article, I will try to illustrate the modeling considerations in caesar II.

Two types of shell and tube heat exchangers are used in industrial applications.

  1. Heat exchanger without expansion bellow and
  2. Heat exchanger with an expansion bellow in the shell.

The thermal profiling considerations i.e, the temperature distribution during Caesar II modeling is different in both cases.

Inputs required for Modeling

Before modeling the equipment the following details need to be collected.

  • Equipment GA drawing with all dimensions.
  • Fixed and Sliding saddles.
  • Shell side inlet and outlet design parameters.
  • Channel or tube side inlet and outlet design parameters.

Modeling of the Heat exchanger without expansion bellow

Caesar II modeling of heat exchangers that do not have an expansion bellow is quite easy. Better engineering practice is to model the equipment as a rigid body. Refer to Fig. 1 and the Table below that simultaneously for modeling the elements as shown.

Schematic of Shell & Tube Heat Exchanger without bellow
Fig. 1: Schematic of Shell & Tube Heat Exchanger without bellow
Region Node No OD & Thickness Process Parameters Temperature Material Length Remark
Fixed Saddle (A) 10000 to 10020 Shell Shell ( Tis + Tos ) /2           Shell Shell OD/2 i.e Length A Fixed Anchor at node 10000
Part of Shell in between Fixed and Sliding saddle (B) 10020 to 10070 Shell Shell ( Tis + Tos ) /2           Shell Length B from equipment GA  
Sliding saddle (C) 10070 to 10090 Shell Shell ( Tis + Tos ) /2           Shell Shell OD/2 i.e Length C Hold Down + Guide at node 10090
Shell part after sliding Saddle (D) 10070-10110 Shell Shell ( Tis + Tos ) /2           Shell Length D from Equipment GA  
Channel Length (E) 10110-10120 Channel Tube ( Tit + Tot ) /2          Channel Length E  
Remaining Shell after Fixed Saddle (F) 10020-10200 Shell Shell ( Tis + Tos ) /2           Shell Length F from GA  
Channel Length (G) 10200-10210 Channel Tube ( Tit + Tot ) /2          Channel Length G  

Here

  • Tis = shell inlet temperature
  • Tos = shell outlet temperature
  • Tit =   tube inlet temperature
  • Tot =   tube outlet temperature

Modeling the Equipment Nozzle Connection

Modeling steps are shown for Nozzle N1

  • At first, model a rigid element from node 10210 to 10219, other parameters will same as the region (i.e, channel region G in this case). Then put the anchor at node 10220 and connecting node 10219.
  • Then model from 10220 to 10230 as the pipe element with all mechanical and physical properties of the nozzle (refer to mechanical datasheet)
  • Then model the element 10230 to 10240 as a flange element with all mechanical and physical properties of the flange (refer to mechanical datasheet).

All other nozzle modeling procedures will be similar to nozzle N1 modeling.

From node 10240 onwards connected piping can be modeled.

Modeling of the Heat exchanger with an expansion bellow in the shell

Refer to Fig. 2 and Table below that simultaneously to model the elements as shown.

Shell and Tube Heat exchanger with an expansion bellow in the shell
Fig. 2: Shell and Tube Heat exchanger with an expansion bellow in the shell
Region Node No OD & Thickness Process Parameters Temperature Material Length Remark
Fixed Saddle (A) 10000 to 10020 Shell Shell ( Tis + Tos ) /2           Shell Shell OD/2 i.e Length A Fixed Anchor at node 10000
Part of Shell in between Fixed Saddle and Channel (B) 10020 to 10200 Shell Shell ( Tis + Tos ) /2           Shell Length B from equipment GA  
Complete Shell Length (C) 10200 to 10110 Shell Tube ( Tit + Tot ) /2           Tube Length C from GA  
Shell Part in between Nozzle N4 and channel (D) 10110-10100 Shell Shell ( Tis + Tos ) /2           Shell Length D from Equipment GA  
Shell Part in between Nozzle N4 and sliding saddle (E) 10100-10070 Shell Shell ( Tis + Tos ) /2          Shell Length E from GA  
Sliding Saddle 10070-10090 Shell Shell ( Tis + Tos ) /2           Shell Shell OD/2 Hold Down and Guide at node 10090
Channel part (F) 10110-10120 Channel Tube ( Tit + Tot ) /2          Channel Length F from GA  
Channel part (G) 10200-10210 Channel Tube ( Tit + Tot ) /2          Channel Length G from GA  

Nozzle is to be modeled in the same way as shown for the above Heat exchanger.

Few companies model the Saddle/Skirt part from the bottom of the shell. In that case rigid element is to be modeled from nodes 10000 and 10090 with saddle length as per GA. (Different saddle temperatures are to be considered for these elements, However, shell material, OD, and thickness can be considered for modeling this part.). In such a situation, the fixed anchor and hold down+guide supports need to be considered at the bottom of the saddle.

A sample model is shown in Fig. 3 below.

Sample Shell and tube heat exchanger model in Caesar II
Fig. 3: Sample Shell and tube heat exchanger model in Caesar II

Few more Exchanger related resources for You..

Basics of Shell and Tube Heat Exchangers: A brief presentation
An article on Plate Heat Exchanger with Steam
A typical Check List for Reviewing of Shell & Tube Heat Exchanger Drawings
A brief presentation on Air Cooled Heat Exchangers
Basic Considerations for Equipment and Piping Layout of Air Cooled Heat Exchanger Piping
Reboiler Exchanger and System Type Selection

Coating Selection for External Bolting to Reduce Corrosion

Written by Mohammad Fouladi in Process

Bolts and Nuts are fasteners for joining two parts. Even though bolted joints are not permanently similar to welded joints, still they are used in industries to a large extent wherever there is a need for separation of the parts. Process, Power, and Steel Industries can not be thought of without Nuts and Bolts. But one of the major problems with Bolted joints is external corrosion due to the working environment.

How to Protect Bolts from Corrosion

Corrosion of nuts and bolts is a major concern for industries. One of the major causes of bolt failure and loose bolt is Extreme Corrosion. The use of Corrosion Resistant material is one option to prevent bolting corrosion but that translates into huge costs. So this is normally not suggested for Carbon or alloy steel piping. Use of bolt cap is another option that can be used for bolt sizes between 1/2 inch to 6 inches. But the most cost-effective way to increase bolt life from corrosion is by using corrosion-resistant coatings. In this article, I will highlight some important points for coating selection.

Types of Bolt Coatings

Various coating methods (Fig. 1) are used in industries. However, the most frequently used methods along with governing coating standards are listed below:

Various Types of Bolt Coatings used in Industry
Fig. 1: Various Types of Bolt Coatings used in Industry
  • Hot Dip Galvanized: ASTM A 153/ ASTM F 2329/ ISO 10684
  • Zinc Plating: ASTM B633/ ISO 2081
  • Zinc‐Aluminum: ASTM F 1136/ EN ISO 10683/ EN 13858
  • Zinc‐Nickel: ASTM B 841/ ISO 15726
  • Cadmium: ASTM B 766/ ISO 2082
  • Phosphate: ASTM F1137/ ISO 9717
  • Aluminum particle Filled (Ceramic): ASTM F 1428
  • PTFE: Normally Manufacturer Standard

Coating Material Selection Chart

Refer to Fig. 2 below. The image provides a quick guide for selecting coatings based on their application and operating temperature range. Refer to the General Notes and Special Notes mentioned at the bottom of the image while selecting the coating materials.

Coating Material Selection Guide Chart
Fig. 2: Bolt and Nut Coating Material Selection Guide Chart

General Notes for Coating Selection Chart

  • This chart is just a recommendation, other coatings may be used based on successful experience.
  • These coatings are normally applicable to carbon or low alloy steel bolting. CRA bolting is not included in the chart.
  • In the selection of coatings, their cost has been also considered.
  • Hydrogen embrittlement may occur on fasteners caused by hydrogen, introduced from chemical cleaning, pickling, or coating process e.g. electrolytic plating and Hot Dip Galvanized. Such coatings may need pretreatment/post-treatment.
  • Fasteners should be avoided in splash zone applications. However, when this is unavoidable, fasteners shall be made of seawater-resistant material, e.g. alloy 625/725 or similar.
  • Cadmium coating is still being used; however, due to the hazardous nature of the plating
    process and exposure to the environment, it is being phased out.
  • Wax-based systems may be used as maintenance systems.
  • For Hot Dip Galvanized coating, the Dip spin procedure should be applied.

Special Notes for Coating Selection Chart

Refer to the Numbers mentioned in Fig. 2.

  1. Zinc-plated, Hot-dip Galvanized, and phosphate coatings should not be used at continuous temperatures above 200˚C.
  2. Zinc/Aluminum coating is normally known under registered trademarks such as DACROMET, GEOMET, etc.
  3. Zinc/Aluminum coating may be used up to 300˚C by manufacturer approval.
  4. Phosphate coatings are normally used as a pretreatment to other coatings but may be used in noncorrosive or mildly corrosive areas especially when a sealer is used.
  5. Zinc plating + chromate treatment may be used in the coastal area for short-term applications (less than 10 years) or for long-term applications when they are painted.
  6. Hot Dip galvanized coating may be painted to the extent of its life in marine atmospheres.
  7. Most PTFE coating can be used up to 230˚C, but they may be used up to 260˚C by manufacturer approval.
  8. For subsea applications, the coating of low alloy bolting materials protected by CP is unnecessary. However, thin metal (hot spun galvanized or zinc‐nickel electroplate) is often specified to preserve the bolt surface prior to or during installation.
  9. Ceramic coating for marine applications shall be top-coated. The average coating thickness shall be 20‐30 μm. The base coat can be aluminum particles dispersed in a liquid binder of chromate /phosphate compounds. The top coat can be ceramic oxide pigments dispersed in a liquid binder of chromate/phosphate compounds.

Few more Resources for you..

FORMS OF CORROSION: An article
How to Select a Bolt: A definite Guide
Corrosion under insulation: A Presentation
PROCEDURE FOR FLANGE-BOLT TIGHTENING OF VARIOUS SIZES OF FLANGES
Corrosion Protection for Offshore Pipelines
Collar Bolts To Maintain Removable Bundles in Heat Exchangers
Corrosion Monitoring Techniques & Surveys: A short Presentation
Flange Insulating Gasket Kits for Industrial Application