Anti-Corrosive Composites for Oil and Gas Industry

Written by Anup Kumar Dey in Engineering Materials,Piping Design Basics

What are Composites?

Composites are novel materials made by combining two or more materials, the resultants of which possess the combination of better properties of the ingredients.

Constituents of composites

Base material – Matrix – metal, ceramic, or polymer
Reinforcement – e.g. fiber
Fillers

Dual Laminate Composite

Thermoplastics lined to thermosets e.g. PVC-FRP, CPVC-FRP, PVDF-FRP, ECTFE-FRP, PP-FRP, FRP-FRP
FRP – made of fiberglass impregnated with either –
- Unsaturated polyester resin
- Vinyl ester resin
- Furan resin
Fiberglass – provides structural stability

Various other combinations of Composites

FRP-Polymer Concrete
FRP-Steel
FRP-Concrete
Thermoplastic reinforced cement concrete
Thermoplastics on Steel

FRP-Polymer Concrete

Unsaturated polyester resin filled with quartz
Cast like concrete in molds
High compressive strength
High corrosion resistant
High impact strength

Application: used for electrolytic cells in copper refineries replacing lead-lined RCC cells

Fibre Reinforced Composites

Glass is the chief reinforcement used for composite materials in chemical process industries.

Mostly in the form of GRPs

S-glass – for high strength
C-glass – corrosion resistant
Carbon fibers – superior mechanical properties, low density, and corrosion resistance used for offshore oil field applications
For some strength: CFRP composite
- 80% lighter than steel
- 60% lighter than aluminum

Applications of GRP composites

Resistant to most chemicals including acids, where metals like SS and Ni-alloys fail to survive Also handle lethal and corrosive Chlorine gas, halide salts, and bleaching solutions including hypochlorite Unlike metals can withstand wide fluctuations in pH and temperature. E.g. effluent treatment process Resistant to corrosion in damp soil conditions, oxidizing and reducing agents such as H₂S

Industries served

Water and waste-water treatment
Pulp & paper
Food/chemical processing
Mining-mineral recovery
Microprocessor manufacturing
Pharmaceutical
Power generation

Chemical Industry Applications

Piping
Chimney and Stacks
FGD applications
Offshore applications
Storage tanks and Pressure vessels
Composites are attractive for this application due to the following parameters:
- Corrosion resistance, strength & ease of fabrication
- Installed cost as compared to SS or CS-lined e.g. CNG tanks

Dimensions:

Diameter: 1 to 10m
Wall thickness: 5 to 50mm

**Fig. 2: Typical Anti-Corrosive Composite Pipes**

Composite Piping

GRP piping applications include
- Potable water distribution
- Firewater systems
- Cooling water lines
- Handling De-mineralized water
- Effluent systems
- High-pressure pipelines handling aggressive media such as saltwater, oil, or brine
Unsaturated polyester, vinyl ester resin used for chimneys and Stacks.
Can withstand high temperatures (up to 240 Degrees C) and severe corrosive gases
Carbon fiber reinforcements and epoxy resins are used only in selective cases, wherein high strength and light weight are more important than corrosion resistance.
Deep well platforms – tension leg platforms(TLPs)
- spars and drilling risers
- choke and kill lines

Offshore Applications

Secondary structures including ladders, handrails, and gratings
Flow and gathering lines
Firewater lines
Casings
Surface injection
Saltwater disposal lines
CO₂ handling
Tank battery piping

Materials used in Offshore composites

Bisphenol(A) polyester, bisphenol vinyl ester, Novalac epoxy, and phenolics – Fire retardant

Summary

Glass fiber-reinforced composites are being selectively used in chemical processes and oil & gas industries for the following advantages:

Exceptional freedom of design and manufacture of many complex shapes.
Outstanding durability even in extremely harsh environments
A custom selection of resin and reinforcements
Superior strength and stiffness-to-weight ratios
Highly corrosion resistant in almost every chemical environment
Lower maintenance and replacement costs

Glass Lining

Glass

Inert, hard, and biologically inactive
Can be formed into a very smooth and impervious surface
Brittle in nature

Types of Pfaudler Glass

World Wide Glasteel 9100
Pharma Glass PPG
Stainless Steel Glass 4000
Ultra Glass-6500
Anti-static Glass

World Wide Glasteel 9100

Offers an unmatched combination of
Corrosion resistance
Impact Strength
Thermal shock resistance
Non-adherence
Heat transfer efficiency

Stainless Steel Glass 4000

Reliable glass lining of stainless steel for pharmaceutical / FDA applications
Suitable for cryogenic processes & pure products for electronics
A virtually inert glass that resists corrosion, abrasion, and product adherence

Pfaudler Ultra Glass

Addresses the requirement of chemical reactions at high temperatures
Enhanced thermal tolerance up to 343 Degrees C – an improvement over WWG 9100
Extended thermal shock protection for faster heating and cooling

Limitations:

Operating temperature
Chemicals
Cavitation
Electrostatic discharge
Abrasion

FRP

What is FRP?

FRP is a resin lining into which layers of Fibers are incorporated to optimize lining structure capability and performance.

Types of FRP

Glass Fiber Reinforced Plastics (GFRP)
Carbon Fiber Reinforced Plastics (CFRP)
Polymer (Aramid) Fiber Reinforced Plastics (PFRP)

Why FRP?

FRP is widely used because of its relatively low cost, good chemical resistance, and its mechanical properties:
Specific tensile strength (GPacm³/gm) – Tensile strength per unit density
Specific stiffness (GPacm³/gm) – Tensile modulus per unit density

Scope of Use of FRP

The bottom lining of AST
Piping
Automotive
Naval
Aerospace

Why tank lining?

An effective method for preventing internal corrosion in storage tanks
Maintaining the stored chemicals’ purity and quality
The long lifetime for storage tanks
To overcome tank bottom perforations due to external corrosion

Graphite

Impervious Graphite is a traditional material selected for high conductivity, chemical resistance, and good mechanical properties. It is specially treated with synthetic resins to ensure that the base structure is fully impervious to liquids under pressure.

Graphite forms no compounds due to corrosion, and no surface films as do many metals. Hence graphite surface remains smooth and more resistant to scale build-up.

Graphite lining can replace most of the other types of linings due to:

Better thermal conductivity
Superior chemical corrosion resistance. Corrosion loss is < 0.05mm/yr
Lower initial/lifetime costs
Has higher temperature applications compared to all the polymeric linings except for the PTFE family
The trouble-free operating life of approx. 5 yrs
Can be used for lining very large size equipment

Regularly available equipment with graphite

Reaction vessels
Heat exchangers
Falling film absorbers
Acid dilution units
Tail gas scrubbers
Raschig rings
Dry HCL gas handling equipment
Impervious graphite tiles

Patch repairs: Can be repaired easily as compared to other linings, especially glass lining.

Few more useful Resources for you…

An Article on Forms of Corrosion
Corrosion under insulation: A Presentation
Corrosion Protection for Offshore Pipelines
Corrosion Monitoring Techniques & Surveys: A short Presentation
Guide for Coating Selection for External Bolting to Reduce Corrosion
Application of Anti-Corrosive Linings in Oil and Gas Industry

ASME Section VIII Flange Leakage Checking Method in Caesar II

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

My last two articles on flange leakage explain the basic theory behind flange leakage checking and methods for performing flange leakage checking using the pressure equivalent method. In this article, I will explain the steps taken to perform a flange leakage check using Caesar II by the ASME Sec VIII method.

Background of ASME Sec VIII Flange Leakage Checking

ASME Sec VIII flange leakage method is performed when the flange analysis using the pressure equivalent method shows failure in Caesar II. The pressure equivalent method is believed to be highly conservative and does not provide the actual results. In most situations, the pressure equivalent flange leakage checking shows failure even with very less axial force and bending moments. It is, therefore, a standard engineering practice to perform the ASME Sec VIII method for those flanges where the pressure equivalent method shows failure.

ASME Sec VIII flange leakage checking method is widely accepted in industries and frequently used to qualify the flanges where the pressure equivalent method shows a failure.

Inputs for ASME Sec VIII Flange Leakage Checking

The following codes and standards are required for data input in the Caesar II flange leakage spreadsheet while performing the ASME Sec VIII method.

ASME B 16.5/ASME B 16.47- Latest Edition (For Flange Data)
ASME B 16.20- Latest Edition (For Gasket Data)
Piping Material Specification (For Flange, Bolt, and Gasket Materials and types)

Steps for ASME Sec VIII Flange Checking Method in Caesar II

The basic steps involved in performing ASME Sec VIII flange leakage checking in Caesar II are mentioned below:

Creating the Flange Analysis File

1. After performing static analysis click “Analysis” and then click “Flanges” in CAESAR II as shown below.

**Caesar II ASME Sec VIII Flange Leakage Module**

2. Provide a file name and select the proper Flange Type in the section as mentioned in the PMS. Input the flange parameters in the consistent unit as per the used UNIT FIL as shown below:

Entering Flange Parameters

3. Press the key “Ctrl+F” to select the concerning Size and Rating. Few data will automatically be filled from the Caesar II database. However, it is good practice to confirm the data from the governing code.

4. Flange Class is the flange pressure rating and is required for checking the P-T Rating of Equivalent Pressure.

5. Flange Grade: Select Material Group No. as per ASME B 16.5 Table 1A list of material specifications. The following table can be used as a reference:

6. Refer to the applicable flange code ASME 16.5 or ASME B 16.47 and update automatically filled flange data. Take special care while inputting for ‘Small End Hub Thickness’& ‘Large End Hub Thickness’. ‘Small End Hub Thickness ’ must be equal to the Pipe Thickness. Large End Hub Thickness must be equal to (X-B) where X is Hub Diameter and B Flange ID.

Enter hub Length h=(Y-t_f) where Y is length through Hub and t_f is flange thickness.

Inputting Bolt and Gasket Data

7. Now enter the Bolts and gasket parameters. Take parameters from ASME B 16.20 or ASME B 16.21 as shown below:

8. Check the Bolt Circle Diameter, Number of Bolts, and Bolt Diameter, suggested by CAESAR II in reference to ASME B 16.47, 16.5.

9. Correctly input for Gasket information in conjunction with ASME B 16.20 or 16.21 as applicable.

10. For Effective Gasket Modulus, press Shift+? Key and then follow “High End” in the Help statement. Leak Pressure Ratio m, Gasket Seating Stress y shall be in accordance with ASME SECTION VIII Div.1. Values for Caesar II help can be taken by pressing Shift+? or by pressing the F1 key keeping the cursor on the relevant box. Click here to know more about leak pressure ratio m and gasket seating stress y.

11. For Nubbin Width on the right side, Leave blank for Welding Neck Type and input Ring joint width as per the ring no. as described on ASME B 16.20 Table 3 TYPE R RING GASKET DIMENSIONS AND TOLERANCES for ring type joint.

12. Facing Sketch/ Facing Column can be inputted as follows mentioned below:

**Facing Sketch and Facing Column for Flange Leakage Checking**

Entering Material Data

13. Now input the material data as shown below:

**Flange and Bolt Material Data for Flange Leakage checking**

14. Select the material of the Flange and bolt, and the Input design temperature.

15. Flange Allowable & Bolt Allowable at design and ambient temp can be taken from the CAESAR II database for particular flange and bolt material.

16. Flange Modulus of Elasticity shall be taken from table C-6 of ASME B-31.3.which is given in millions of psi to convert it to the consistent unit.

Inputting Pressure and Load Data

17. Use 1.0 for Flange Allowable Stress Multiplier and 2.0 for Bolt Allowable Stress Multiplier. Use project-specific data if available.

18. Now Input Design Pressure, Axial Force, and Bending Moment from Static analysis of the Caesar file as shown below:

Performing Flange Leakage Analysis and Reviewing Results

19. Now run the analysis to study the output results. Normally If the safety factor is less than one then joint failure is predicted and in output, this is shown by a * mark.

**Output Data in Caesar II Flange Leakage Checking Module**

20. If the output result shows failure then try to reduce the bending moment or axial force and reanalyze. If that is not possible check if the flange rating can be increased.

Sometimes, the flanges are seen to be failing in seating stresses. In such a scenario, try to get actual gasket seating stress data from the vendor and enter it into the spreadsheet. Normally with reduced gasket seating stress value seating failure can be avoided.

Click here to find out the Flange leakage checking methodology based on NC 3658.3 Method

Recent changes in ASME B31.3 and their implementation in CAESAR II

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

This presentation is prepared by Mr. Deepak Sethia (working in Imagegrafix software) who has extensive experience in using Caesar II software and troubleshooting. The points that will be covered in this article are:

Allowable Displacement Stress Range
Expansion Allowable Stress Change
Longitudinal stress due to sustained loads
Appendix P
B31J

Allowable Displacement Stress Range (SA)

SA is defined in equations (1a) & (1b) of ASME B 31.3 (Reproduced below)
SA is a function of the cyclic factor f

The definition of f has changed over the years.

Sc and Sh are each limited to 20 ksi when calculating SA allowable displacement stress range.

Expansion Allowable Stress Change

CAESAR II Has Always Determined & Used the “Maximum Value”.

But What Does “Considering All Support Conditions” Mean?

Alt Sustained (formerly Hot Sustained approach)

“… All Support Conditions (Positions) of The Pipe …”

Each Operating Load Case (For a Particular Support Condition) Could Produce a Different Sustained Stress Distribution.
The Expansion Allowable Must Be Based on The Maximum Sustained Stress, Considering All of These Operating Load Cases.
Consider the following Example:
Only 2 of The Branch Lines are Hot.
One Branch Line is Cold.

The system Has Three “Real” Operating Conditions, All Producing a Different Primary (Sustained) Stress State Due to Different Nonlinear Support Conditions.

How Can This Be Achieved, Automatically In The Software?

New Load Case Template Recommendations

ASME B31J

Standard Test Method for Determining Stress Intensification Factors (i & k Factors) for Metallic Piping Components
The scope of this standard has recently been revised to add the ability to update new i & k Factor information as it becomes available
B31J provides a set of calculations for revised SIFs and flexibility factors, as defined in the revision to ASME B31J. By using these revised SIFs and flexibilities, your stress analyses produce more accurate results. B31J provides the “more applicable data” referenced in recent editions of the piping codes.

What 319.3.6 is saying……

i-factor requirement as per the Latest Code

As shown in Figure the previous code (Appendix D) you had SIF(i) and SIF(o) which were valid for both Expansion Stress and Sustained Stress. Now you can find the following. Not only the SIF are different for the primary and secondary stress but in addition, you have to consider SIF for Tortion and axial effect!

SIF is valid for Expansion Stress (SIF)and Index(SSI) is valid for Sustained Stress.

Do you know that the i & k factors from ASME B31.3/ASME B31.1 can be calculated according to B31J and it is freeware available with CAESAR-II software?

B 31J calculations in CAESAR II…..

B 31J result for Flexibility (k) & SIF (i)…..

CAESAR-II model with “more applicable data”….

We open the translated model in CAESAR II using B31J option

Top 15 Piping Books for a Piping Engineer

Written by Anup Kumar Dey in Piping Design Basics,Piping Stress Analysis

This post is solely for beginners in the piping industry. If you want to learn the basics from books or literature, then try the following 15 listed books. Most experienced piping professionals will be aware of these piping books. Most of the piping books and literature mentioned below are available for free downloading over the internet. Simply search with the book name along with the term pdf, and you will get it. All these piping engineering books are also available in the Amazon online portal, from where you can easily buy them. Additionally, simply do an exclusive search on the internet, and you will find some links to download these piping books for free.

1. PIPE STRESS ENGINEERING by L C Peng and T L Peng:

This is the best book on piping stress engineering. If you are planning a career in piping stress analysis, then you must collect this book and read it effectively to build solid basics. This book explains the ideas so nicely that it will provide effective results to you.

It delves deeply into the principles and methodologies of pipe stress analysis. The book offers an extensive exploration of stress analysis techniques, focusing on the mechanical behavior of pipes under various loads and conditions. It covers critical topics such as thermal expansion, pipe supports, and the impacts of different loading scenarios on pipe integrity. Detailed explanations are provided on methods for calculating stress, evaluating pipe supports, and designing systems to manage stress-related issues. The inclusion of practical case studies and real-world examples further enriches the content, illustrating how theoretical principles are applied in practice.

What sets Peng’s book apart as a premier resource for pipe stress engineers is its comprehensive and practical approach to a complex subject. The authors’ ability to break down intricate concepts into understandable segments makes this book invaluable for both seasoned professionals and those new to the field. The practical guidance on managing stress-related issues and the integration of case studies provide actionable insights that are directly applicable to everyday engineering challenges. The book’s focus on real-world applications and problem-solving ensures that it remains a crucial reference for engineers aiming to enhance their expertise in pipe stress engineering and ensure the reliability and safety of their piping systems.

2. DESIGN OF PIPING SYSTEMS by M W Kellogg Company:

This is the second-best book on piping stress analysis. Even though the language used is quite difficult to comprehend and the contents are not interesting, this book shares a great place for describing the topics effectively and was the best book earlier before the Peng book.

M. W. Kellogg’s “Design of Piping Systems” is a classic text that provides a detailed examination of the principles and practices involved in designing piping systems. The book covers a range of topics including pipe sizing, stress analysis, and material selection. Kellogg’s text is known for its depth of coverage and its methodical approach to addressing the various challenges encountered in piping system design. It also includes practical examples and case studies to illustrate key concepts.

The enduring relevance of Kellogg’s book lies in its thorough and systematic approach to piping system design. The book’s detailed explanations and comprehensive coverage make it a valuable reference for engineers seeking a deep understanding of piping design principles. Its combination of theoretical knowledge and practical examples ensures that it remains a key resource for both learning and applying piping design techniques.

3. INTRODUCTION TO PIPE STRESS ANALYSIS by Sam Kannapan:

One of the best books on piping stress analysis and is easy to understand. “Introduction to Pipe Stress Analysis” by Sam Kannapan is an accessible yet thorough guide designed to introduce engineers to the principles and practices of pipe stress analysis. This book covers fundamental concepts such as the behavior of pipes under various loading conditions, stress calculation methods, and the importance of proper pipe support and restraint systems. Kannapan provides a clear explanation of key topics including thermal expansion, pipe flexibility, and the impact of different types of loads on pipe systems. The book is structured to build a solid foundation in pipe stress analysis through clear illustrations, examples, and straightforward explanations.

The strength of Kannapan’s book lies in its approachability and clarity, making it an ideal resource for both newcomers and seasoned engineers seeking a refresher. The practical focus and structured presentation of complex concepts makes it easier for readers to grasp and apply pipe stress analysis principles in real-world scenarios. The book’s emphasis on fundamental techniques, combined with practical examples and problem-solving strategies, ensures that it serves as an excellent reference for engineers aiming to understand and address stress-related challenges in piping systems effectively.

4. COADE STRESS ANALYSIS SEMINAR NOTES by COADE:

Must have a tutorial guide for every piping stress engineer using CAESAR II. Explains in detail all the basics of Caesar II’s application. The guidebook is developed by Hexagon (COADE) and explains all the basic concepts that are used for the development of the Caesar II software program.

5. PIPING HANDBOOK by M L Nayyar:

One good book for both stress and layout engineers with the huge important databases on piping engineering. Refer to this book for any data you require during your day-to-day piping work. The “Piping Handbook” by Mohinder L. Nayyar is a definitive resource that encompasses a wide array of topics essential for piping engineers. This book covers everything from basic piping design principles to advanced topics such as pipe stress analysis, hydraulic calculations, and material properties. Nayyar’s handbook is renowned for its detailed tables, charts, and formulas that aid in the design and analysis of piping systems. It also addresses various industry codes and standards, providing a thorough grounding in compliance and best practices.

What makes Nayyar’s Piping Handbook an excellent reference is its broad scope and depth of coverage. The book’s extensive collection of practical data and guidance makes it a useful tool for engineers working in diverse industries, from oil and gas to chemical processing. Its emphasis on real-world applications and problem-solving, combined with its comprehensive coverage of standards and regulations, ensures that it remains a critical resource for professionals seeking reliable and detailed information.

6. PIPE DRAFTING AND DESIGN by Rhea and Perisher:

The best book for a beginner. Covers the basics in simple language. Very easy to understand. “Pipe Drafting and Design” by Rhea and Perisher is a comprehensive guide that provides a detailed overview of the principles and practices involved in drafting and designing piping systems. The book covers a wide range of basic topics, including the fundamentals of pipe drafting, design standards, and the various types of piping systems used in different industries. Rhea and Perisher delve into the technical aspects of piping design, such as pipe layout, the selection of materials, and the application of industry codes and standards. The text also emphasizes the use of drafting software and tools, making it relevant for modern design practices.

This book is highly regarded for its practical approach and its ability to bridge the gap between theoretical knowledge and real-world drafting application. Rhea and Perisher’s clear explanations and step-by-step guidance make complex design concepts more accessible, helping both novice and experienced engineers enhance their drafting and design skills. The inclusion of detailed illustrations, case studies, and practical examples provides valuable insights into the design process, making it a valuable reference for anyone involved in the drafting and design of piping systems. Its focus on both traditional techniques and modern tools ensures that it remains relevant in today’s evolving engineering landscape.

7. PROCESS PLANT LAYOUT AND PIPING DESIGN by Hunt and Bausbacher:

The best book for a piping layout engineer. Covers the basics of the piping layout. Most of the preliminary layout ideas connected to any equipment evolve from this book. So read this book attentively for effective layout knowledge.

“Process Plant Layout and Piping Design” by Ed Bausbacher and Roger Hunt is a highly regarded text that provides an in-depth exploration of the principles and practices involved in the layout and design of piping systems in process plants. The book covers a wide range of topics essential for effective process plant design, including the fundamentals of layout planning, equipment arrangement, and the integration of piping systems with plant processes. Bausbacher and Hunt address critical considerations such as safety, accessibility, and efficiency in piping design, offering practical guidelines for optimizing plant layout and ensuring operational effectiveness.

The value of this book lies in its comprehensive and practical approach to process plant layout and piping design. Bausbacher and Hunt’s expertise is evident in their detailed explanations and real-world examples, which help readers understand complex design concepts and apply them to practical situations. The book’s focus on optimizing plant layouts for safety and efficiency makes it an essential resource for engineers involved in the design and operation of process plants. Its combination of theoretical knowledge and practical application ensures that it remains a crucial reference for achieving effective and efficient process plant design.

8. PROCESS PIPING DESIGN HANDBOOK by John Mcketta:

One of the good books. The “Process Piping Design Handbook” by John J. McKetta Jr. focuses on the detailed aspects of designing piping systems specifically for process industries. McKetta’s handbook covers various design considerations such as flow dynamics, material selection, and the integration of piping with process equipment. It provides in-depth guidance on designing for safety, reliability, and efficiency, addressing issues such as thermal and mechanical stresses, as well as corrosion control.

McKetta’s handbook is highly valued for its targeted focus on process piping, making it an essential resource for engineers working in process industries. The book’s detailed coverage of design principles and its emphasis on practical design considerations ensure that it provides relevant and applicable knowledge for engineers looking to optimize their process piping systems. Its thorough exploration of industry-specific challenges and solutions enhances its utility as a reference for both design and troubleshooting.

9. THE FUNDAMENTALS OF PIPING DESIGN by Peter Smith

Peter Smith’s “Fundamentals of Piping Design” is an accessible yet comprehensive introduction to the principles and practices of piping design. The book covers fundamental topics such as system layout, pipe sizing, and material selection. Smith’s approach is designed to build a solid foundation in piping design, making complex concepts understandable for newcomers while providing enough depth to be valuable to experienced engineers. It also includes practical design examples and problems to reinforce the learning experience.

The strength of Smith’s book lies in its clear and methodical approach to piping design fundamentals. It provides a structured pathway for learning the basics of piping design, making it an excellent resource for engineers new to the field or those seeking to refresh their knowledge. Its emphasis on practical examples and clear explanations makes it a valuable tool for developing a strong understanding of piping design principles and practices.

10. “PIPING AND PIPELINE ENGINEERING” by George A. Antaki

“Piping and Pipeline Engineering” by George A. Antaki is a comprehensive guide that covers all critical aspects of piping and pipeline design and maintenance. The book delves into the fundamental principles of fluid dynamics, materials selection, and the mechanical aspects of pipeline systems. Antaki’s text is structured to provide both theoretical knowledge and practical insights, making it an invaluable resource for understanding the lifecycle of piping systems from design through construction and maintenance. It includes detailed coverage of pipe stress analysis, corrosion, and inspection techniques.

This book stands out as a top reference for piping engineers due to its extensive scope and clarity. Antaki’s approach integrates real-world scenarios with theoretical concepts, offering practical solutions to common issues encountered in the field. The inclusion of case studies and practical examples helps bridge the gap between theory and practice, making it a go-to resource for both novice and experienced engineers seeking to deepen their understanding of piping systems.

Other Notable Piping Books

Some other notable piping books that readers can keep as a reference book are:

11. PROCESS PIPING DRAFTING By Rip Weaver: A very nice book in simple, easy-to-understandable language.
12. THE PLANNING GUIDE TO PIPING DESIGN by Richard Beale
13. One must-have book for piping materials engineers is PIPING MATERIALS GUIDE by Peter Smith
14. PIPING SYSTEMS MANUAL by Brian Silowash
15. PIPING DESIGN FOR PROCESS PLANTS by Rase Howard F

In addition to all the above-mentioned piping books, you must remember that you have to read the latest applicable piping codes as well.

All of You are already aware that books are our best friends. It helps us without charging us. So enjoy reading.

Cooling Tower Water Treatment Basics

Written by Anup Kumar Dey in Maintenance,Mechanical

We all know that Cooling towers are essential components in various industrial processes and HVAC systems. They play a crucial role in dissipating excess heat generated during these processes. However, for cooling towers to function smoothly, efficiently, and sustainably, proper water treatment is paramount. Proper water treatment Increases Energy Efficiency, Reduces the water-consumption, and Extends Equipment Life. In this blog post, we’ll explore the importance of cooling tower water treatment, its key components, and the benefits it offers. Additionally, we will learn about the cooling tower water treatment chemicals.

Why Should You Treat Cooling Tower Water?

Cooling towers rely on the evaporation of water to remove heat from processes, making them susceptible to various water-related issues such as scaling, corrosion, and biological growth. Without adequate water treatment, these problems can lead to reduced efficiency, increased maintenance costs, and even system failure. Therefore, cooling tower water treatment is essential for several reasons:

Prevent Scaling: Scaling occurs when minerals in the water, such as calcium and magnesium, precipitate and form deposits on heat exchange surfaces. These deposits insulate the heat exchangers, reducing their efficiency and potentially causing equipment damage.
Corrosion Control: Cooling tower components, including pipes, pumps, and heat exchangers, are often made of metal. Corrosion can lead to the deterioration of these components, compromising the system’s reliability and lifespan.
Microbial Growth Prevention: Cooling towers provide an ideal environment for the growth of bacteria, algae, and fungi. These organisms can clog water distribution systems, degrade water quality, and pose health risks to workers.
To control the water pH.

Effect of Changes in Water Composition

Cooling water operation changes water composition radically causing the circulating water composition really affect the system’s operation and life

Factors affecting physical and chemical properties of water

Temperature change
Evaporation
Air contact
Product contamination

Cooling Tower Water Treatment

Scaling and Fouling of Cooling Tower

Main causes:

Scaling – Due to salts that deposit on high-temperature surfaces due to retrograde solubility
General fouling – Due to insoluble suspended particles forming deposits on the surface
Biological fouling -This results from abundant growth of Algae, Fungi, or Bacteria on the surface

Scale Control in Cooling Tower

Blowdown control
Increased Blow-down limits cycles of concentration.
Treatment is required to keep the dissolved solids in the non-scale forming state.
Scale inhibitors do this permitting operation at supersaturated conditions
Acid Dosing- Sulfuric Acid
Relatively inexpensive method
The acid treatment removes the bicarbonate acidity by converting HCO3- to SO4 and CO2
CO₂ is released to the atmosphere and Sulfate remains as by product
Caution – Overdosing causes corrosion

Fouling Control in Cooling Towers

Fouling occurs when insoluble suspended particles like iron, mud, silt, and other debris deposit on the surfaces.
Removal of suspended matter from make-up water, re-circulating water, basin by use of Side-stream filters (filtering 1-5% of the total circulation)
High Water Velocities- A design stage measure for deposit control. This is always not possible ( Shell side)
Dispersants-Keep the particulates in suspended form
Surfactants-Keep the Hydrocarbons in emulsified form

Controlling Corrosion in Cooling Tower

Achieved by dosing a Corrosion inhibitor. This primarily works by forming a protective film on the surface.
Different types of treatments:
Chromate based program
Phosphate/ Phosphonate Programs
Di-anodic
Alkaline Zinc
Alkaline Phosphate Program
All Organic
Molybdate based

Micro-Biological Control in Cooling Tower

Microorganisms enter through wind, dust, and make-up water
Results in Slime and algae growth
Important to minimize slime and algae growth as they reduce
heat transfer
decrease cooling water flow
localize corrosion
serve as a mortar for the rapid buildup of deposits
Control is done by dosing chemicals
Biostatic agents: Chemicals that inhibit the growth of microbes
Biocides: Chemicals that kill the microorganisms
Advisable to use biocides in the cooling water treatment – two classes :
Oxidizing Biocides: Chlorine, bromine, Hypochlorite, Chlorine dioxide, Ozone
Non-Oxidizing Biocides: Methylene-bis-thiocyanate (MBT), Organotin compounds, Aldehydes, Chlorophenols, Sulphones and Thiones, Carbamates, Isothiazoline
Biofouling – accumulation of deposits of microorganisms forming films
Biodispersants are used for dislodging the biofilms and preventing their formation
Followed by the addition of biocide which kills the released bacteria

pH Control in Cooling Tower

Important to minimize the rate of corrosion in a heat transfer/cooling system
To avoid corrosion problems, controlling the pH in an alkaline range of between 8 and 9 is important
Alkaline pH has a greater tendency towards scaling from dissolved solids
Conductivity measurement measures the level of TDS in water.

Cooling Tower Water Treatment Chemicals

For cooling towers to remain effective and reliable in a variety of industrial and commercial applications, cooling tower water treatment chemicals are crucial. Specific water-related problems like scale, corrosion, and microbiological development are addressed using these compounds. The following are some of the main compounds used in cooling tower water treatment and what they do:

Biocides:

Biocides are those chemicals that are used to control microbial growth in cooling tower water. Various microorganisms like bacteria, algae, and fungi can thrive in the warm and nutrient-rich environment of cooling towers, leading to biofilm formation and clogging. Biocides help eliminate or prevent the growth of these microorganisms, ensuring the water remains clean and free from biological fouling.

Oxidizing Biocides: Examples include chlorine and bromine-based compounds. These chemicals are effective at killing existing microorganisms.
Non-Oxidizing Biocides: Compounds like quaternary ammonium compounds (quats) and isothiazolinones are non-oxidizing biocides used to prevent the regrowth of microorganisms.

Scale Inhibitors:

Scaling occurs when minerals in the cooling water, such as calcium and magnesium, precipitate and form deposits on heat exchange surfaces. Scale inhibitors, often referred to as antiscalants, work by sequestering these minerals, preventing them from forming scale deposits. Common types of scale inhibitors include polyphosphates and phosphonates.

Corrosion Inhibitors:

Cooling tower components are typically made of metal, making them susceptible to corrosion. Corrosion inhibitors are chemicals that create a protective film on metal surfaces, preventing corrosion and extending the life of equipment. Common corrosion inhibitors include orthophosphates, molybdates, and filming amines.

pH Adjusting Chemicals:

Maintaining the proper pH level in cooling tower water is essential to prevent both scaling and corrosion. Chemicals such as sulfuric acid and caustic soda are used to adjust and control the pH of the water within the desired range.

Dispersants and Surfactants:

Dispersants are used to keep suspended particles and solids in the water from settling and forming deposits. Surfactants can improve the wetting ability of the water, enhancing its contact with surfaces and facilitating the removal of deposits.

Anti-Foaming Agents:

Foaming in cooling towers can reduce their efficiency by interfering with the heat transfer process. Anti-foaming agents are added to control and minimize foam formation.

Scale and Deposit Removers:

In cases where scaling or deposits have already formed, specialized chemicals may be used to dissolve and remove these accumulations. Acid-based descaling chemicals are often employed for this purpose.

Oxygen Scavengers:

Oxygen in the cooling water can promote corrosion. Oxygen scavengers, such as sodium sulfite or hydrazine, are used to remove dissolved oxygen from the water, reducing the risk of corrosion.

Dissolved Solids Control:

Cooling towers can concentrate impurities as water evaporates. To prevent the buildup of excessive dissolved solids, chemicals like phosphates and polymers are used to control their levels.

Air Cooler Piping Design

Written by Anup Kumar Dey in Piping Design Basics

Air Cooled Heat Exchangers are used in the plants to utilize the atmospheric air to cool the hydrocarbon, process, and utility fluids by means of direct heat transfer from the fluid (within the tube) to be cooled by air circulated by means of forced/induced draft fan.

In Order to increase the heat transfer area, fins are also attached periphery of tubes. These heat exchangers are generally designed, inspected, and tested as per EN-ISO 13706.

The purpose of this article is to provide guidelines for the Piping Design/Layout connected to Air Cooled Heat Exchanger (Fig. 1) or Air Fin Fan Coolers. Click here to have a brief idea of Air Cooled Heat Exchangers.

Types of Air Cooled Heat Exchangers / Air Cooler Types

There are three types of Air cooled heat exchangers

Forced Draft: The bundle is located on the discharge side of the fan. The fan is below the finned tube bundle.
Induced draft: The tube bundle is located on the suction side of the fan, that is, the fan is above the tube bundle and sucks the air from the bottom.
Natural Draft (Used only for applications like transformer Oil Cooling)

Depending on the position of the inlet and outlet nozzle air coolers, are of the following types:

EVEN PASS ARRANGEMENT: Inlet nozzle of the air cooler is at the top side of the header and the outlet nozzle is on the same side but at bottom of that header.
ODD PASS ARRANGEMENT: Inlet is at the top of the header and the outlet nozzle of the air cooler is at the opposite header side but at bottom of the header.
SPLIT HEADER TYPE: When the differential temperature between inlet and outlet nozzles exceeds 111 degrees Celsius then a split header arrangement is used.

Different Types of Construction Air-cooled Heat Exchangers

Single Pass Cooler
Multipass Cooler
U Tube Cooler

**Fig. 1: A typical Air Cooled Heat Exchanger**

Air Cooler Equipment Layout Design

As this equipment needs a good flow of air for the purpose of better cooling, the location of the air fin fan cooler has to be such that it is not directly crowded or surrounded by other structures or equipment which blocks the path of plenty of airflows.

This static equipment is generally installed on the top of the pipe rack or other structure so that there is no difficulty or obstruction which can reduce proper airflow. Again by installing the air-cooled heat exchangers on top of the rack, huge space on the ground can be saved and the plant will become more compact.

Based on the width of the pipe rack or structure, normally the tube bundle length is fixed. Thus supporting legs of the air cooler bundle comes on the main civil or structural beams, which simplifies the pipe rack design. At the same time, it is desirable to adjust the pipe rack or the structure’s longitudinal column spacing based on the width of the air cooler bundle such that bundle legs straight away sit on top of the columns. Sometimes, This may not be possible to adjust as each tube bundle might have varied widths depending on service conditions, and adjusting pipe rack columns for different widths may not be feasible from a structural design and detailing point of view.

Walkways between two sets of air coolers are desired, which means if one cooler consists of ten bundles and the other of five bundles then walkways have to be provided in between, after the 10^th bundle and before of next five bundles. This dimension of this walkway has to be a minimum of 1.5 to 2.0 m wide as this will be the only place at such elevation to keep tools and parts during maintenance.

The air Fin Fan coolers on the pipe rack shall be located in such a way that the bundles are accessible with a crane at least from one side.

Air Fin Fan coolers must have access platforms mounted on the air-cooled heat exchanger structure at least on the operating side. An all-around platform is a better provision for maintenance.

Air Fin coolers have motors hanging at the bottom of the coolers. Hence, It is required to give access platforms underneath the cooler for maintenance of the motors. The localized platform can also be used.

A regular staircase needs to be provided for accessing the air fin cooler platforms or motor maintenance platforms.

Normally Inlet piping of air cooler requires a symmetrical distribution and loops. The piping needs to be supported so either air cooler structural columns or pipe rack structure columns need to be extended upwards to properly support the piping. Such data has to be given at a very early stage in the project as this needs to be considered during pipe rack design.

If the Air cooler is grade mounted then the area beneath the air cooler shall be paved to avoid the flow of sand/ dust on tubes.

**Fig. 2: Typical Layout of Air Cooled Heat Exchanger Piping**

For two fans per bay, the height of the underside of the fan inlet bell (on forced draft units) or of the underside of the bundle (on induced draft units) shall be at least 2 m or one fan diameter (whichever is the greater) above the ground level, elevated floor or pipe bridge. For three or more fans per bay, the height of the underside of the bundle shall be agreed upon with the Principal.

Air Cooler Piping Design Considerations

Air coolers are normally used when a large quantity of vapor is required for condensation or a huge quantity of gas or liquid needs to be cooled. Such an application is common in the case of column overhead vapor condensation. The major points which need to be taken care of while pipe routing or laying air fin cooler connected piping (Refer Fig. 2, Fig. 3, Fig. 4, and Fig. 5) are as follows:

From the center line of the complete air cooler assembly, the piping distribution to the air cooler should be symmetrical.

If the supply line has very low pressure, care needs to be taken to keep no. of bends or elbows to a minimum. But functionality and stress requirements have to be considered. Line sizing during the distribution has to be proper if required the same has to be checked with the process or operations department.

**Fig. 3: Typical Air Cooler Inlet Piping Arrangements**

The length of all branch pipes for all tube bundles from its header has to be more or less similar to keep pressure drop the same and this will ensure equal distribution of fluids to all bundles.

Normally inlet side header box is considered fixed for piping connection and the other header is floating. But the bundle can move in the transverse direction of tubes = 6 mm or if it is fixed at one edge then it can move by 13 mm in the other direction (as per API 661). This displacement is required for piping header expansion compensation. However the same has to be checked with the air cooler vendor as they may provide other displacement provisions.

**Fig. 4: Air Cooler Outlet Piping Arrangements**

The movement of tube bundles in a transverse direction could occur only when the piping connected to equipment nozzles generates enough force to overcome the friction at the bundle supports that is why it is a common practice to provide SS or PTFE plate at the support point (but this must be consulted with the vendor) to ease the movement.

The loads due to thermal expansion, pipe, insulation & fluid weight, and an inside pressure of piping created on the bundle nozzle shall be less than the limits given by EN-ISO 13706. Sometimes vendor allows a more allowable load (normally 2 times the code given allowable nozzle loads). So it is required to discuss the same with the vendor at the initial stage of the project. The stress analysis of air cooler-connected piping systems is covered here.

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