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Pump Suction Intake Design with Sample Calculation

Written by Anup Kumar Dey in Mechanical,Piping Design Basics,Piping Interface

We all see pumps day in and day out. We see them in our houses, roadsides, industries etc. They are extensively used in adverse applications to transport fluids from one place to another.

What is a pump?

A pump is a mechanical device that moves fluids, solid wastes, chemicals, and slurries by mechanical action. The pump has two important components i.e. Flow & Head.

  • Flow: It determines the amount of fluid pumped.
  • Head: It tells the extent or distance to which fluid is to be exported.

There are two types of Pumps based on their operating principle.

  • Dynamic pumps: They are further classified as Centrifugal Pumps, Vertical centrifugal, Submersible pumps, etc.
  • Displacement pumps: They are further classified as Gear pumps, Piston pumps, Lobe pumps, etc.

As the pump works 24*7 in adverse environmental conditions, it has to be designed properly. Starting from NPSH(A) calculation to pipeline sizing calculation everything should be perfect. In this article, we will learn about “Pump Suction Intake Design Calculation.” The pump suction is designed as per the HIS (Hydrological Institute Standard). So, let’s see what the different terms are associated with pump suction design & how they are calculated.

Terms Associated with Pump Suction Intake Design

Bell Mouth

It is a piping structure that guides the intake of fluid to the pump.  Bell Mouth width is given by D. Width of the bell mouth is calculated as 1.5 to 2 O.D. of the suction pipe.

Typical Pump Bell Mouth Section
Fig. 1: Typical Pump Bell Mouth Section

End Wall Clearance (B)

It is the Clearance between the centreline of the pump suction intake bell and the end wall of the tank. It is calculated as 0.75D.

Centreline Spacing (a)

Centreline spacing between two adjacent pump bell mouths in the same tank will be calculated as 2.5D. This 2.5D is the minimum value.

Bell Mouth Floor Clearance (C)

It is the minimum gap that should be maintained between the bell mouth bottom and the top of the tank floor. It is calculated as 0.3D to 0.5D.

Minimum Submergence (S)

It is the minimum submergence of the pump bell inlet in water. This is calculated as D (1.0 + 2.3FD). Where FD stands for Froude’s number.

Minimum tank width (A)

This is the minimum distance between the pump bell centreline and the next pump wall. It is given by 5D.

Minimum Liquid Depth (H)

It is the minimum liquid depth required in the tank. This is given by the submission of Minimum submergence(S) + Bell Mouth Floor clearance(C). The lowest water level intake is calculated by minimum liquid depth.

The angle of floor slope (α)

This is the slope of the floor required in the tank. Generally, the floor is sloped so that an adequate amount of water is always available near the pump suction.

Typical Pump Suction Cross section
Fig. 2: Typical Pump Suction Cross section
Suction Design Parameters
Table-1: Suction Design Parameters

Impacts of Improper Design

  • Cavitation
  • Pump Dry Run
  • Improper process parameters
  • Improper calculation of NPSH(Available)
  • Increase in OPEX.
  • Vibration in pump body & suction piping
  • Pump Head Loss

The pump suction should be designed considering the above-mentioned parameters. If the suction of the pump is not designed properly there may be problems like cavitation, pump dry run, the problem of priming, etc. So, if you don’t want that these problems to be part of your real life & you want your OPEX to be the least these design considerations should be followed carefully while a pump system is being designed.

Typical Calculation of Pump Suction Intake Design

Consider a pump of flow Q = 1640m3/hr.

  • Pump suction bell design (D) = 1.5* O.D. of pipe

To Calculate the Diameter of the Pipe: Q = A.V. 

Where

  • A = Cross-section area of Pipe or (A=π/4 * D2)
  • V= Velocity in pump suction side (velocity in the suction pipe is generally considered in the range from 06 to 1.5m/s.

Minimum submergence (S): S = D (1+2.3Fd)

Where

  • Fd = Froudes Number (It is a dimensionless number)
  • FD = V/(gD)^0.5
  • V = Velocity in m/s
  • D= Suction bell diameter
  • g = Gravitational acceleration i.e. 9.81 m/s^2

Minimum sump clearance (C)= 0.3 to 0.5D

Lowest water level (H) = S+C

The gap from the centre of the wall to the pipe centre (B)= (0.3D to 0.75D)

Flow(m3/hrInside Diameter(m)Outside diameter(mm)Bell design D) (mm)Velocity(V)(m/s)Froudes Number (FD)Minimum submergence(S) (mm)Minimum sump clearance (C)  (mm)Lowest Water level (H) (mm)Gap of pipe from the centre wall (B) (mm)
16400.6957111066.51.200.371197832022971386
Table 2: Table Showing Results of Sample Calculation

Tutorial Video for Pump Suction Intake Design

For more clarification watch the below-attached video & subscribe to our channel

Few more Useful Resources for you.

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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