The Basics Of Pipes And Bends On Ships - Marine Insight

The Basics ofPipes and Bendson Shipswww.marineinsight.com

Marine Insight The Basics of Pipes and Bends on ShipsPublication date: Oct 2012Author: Mohit SanguriEditor : Raunek KanthariaPublished by: Marine Insightwww.marineinsight.comGraphic Design: Anish Wankhede(copyright symbol) Copyright 2012 Marine InsightNOTICE OF RIGHTSAll rights reserved. No part of this book may be rewritten,reproduced, stored in a retrieval system, transmitted or distributedin any form or means, without prior written permission of thepublisher.NOTICE OF LIABILITYThe authors and editors have made every effort possible to ensurethe accuracy of the information provided in the book. Neither theauthors and Marine Insight, nor editors or distributors, will be heldliable for any damages caused either directly or indirectly by theinstructions contained in this book, or the equipment, tools, ormethods described herein.www.marineinsight.com

Is this Book Right For Me?Not quite sure if this eBook is right for you? See the belowdescription to determine if your level matches the contentyou are about to read.IntroductoryIntroductory content is for professionals whoare new to the subject or who want to learnthe basics of the subjectIntermediateIntermediate content is for professionals whoare familiar with the subject with basicexperience and knowledge on the topic.AdvancedAdvanced content is for professionals whoare, or want to be, experts on the subject.www.marineinsight.com

AboutThis eBook is a compilation of series of articles written by ChiefEngineer Mohit Sanguri on “Pipes and Bends on Ships”Chief EngineerMohit SanguriAbout the AuthorChief Engineer Mohit Sanguri is a Marine Engineer(Class I Unlimited Power). He has 12 years of experienceworking on ships. He is currently working with DynacomTankers Ltd on their Bulk Carriers division and hasserved in the past in Wallems Ship Mgmt. on CarCarriers and PCTC’s, MSC Ship Mgmt. on Containers,Univan Ship Mgmt on RoRos, Five Stars Shipping onBulkers, and SNP Ship Mgmt. on General Cargo atvarious designations.

TABLE OF CONTENTS:1Basics of Pipes. . . 42Bends & Elbows 103Types of Elbows4Types of Nipple . .195Types of Adapter . .236Types of Tee . .267Miscellaneous Fittings . .30 . .16

CHAPTER 1:Basics of PipesThere are several important aspects of the duties of marineengineer on ships as he is someone who is in charge of allthe operations and watch keeping of the engine room.In case of new fabrication of a pipe line, repair work, ormaking dry dock specification, a marine engineer musthave good knowledge of piping and fittings to be used inthe engine room of the ship.Page 4

The Basics of Pipes and Bends on ShipsPipes vs. Tubes – What is theDifference?There is always a doubt among marineengineers about the difference betweenpipes and tubes. Several engineers considerthem as synonyms and even think that theyare interchangeable.However, it is to note that there is adifference and it is based primarily on therules of nomenclature of the pipes and thetubes.In the following points we endeavour to clarify the issue: Pipe is rigid and resistant to bending whereas sometubes such as copper tubes and brass tubes can beflexible. However, in structural projects tubes are rigid. Pipes are classified by schedule and nominal diameter.For example, a 250mm nominal diameter and schedule80 pipe. Tubes are classified by outside diameter and thickness.For example, 10mm copper tube 2 mm thickness.Page 5

The Basics of Pipes and Bends on Ships In pipes, all the fittings can be matched by nominalsize and schedule. For example a schedule 40 one inchpipe will have fittings specified by the same name.These pipe fittings would not fit a 1” tube. Pipe is always round or cylindrical. Tubes may besquare, rectangular and cylindrical. Pipes generally start from ½ inch to very large sizes.However, tubes are generally of smaller diameter only.We use a 10 inch pipe but not 10 inch tube. Tubes are used in applications where the outsidediameter must be precise, like in cooler tubes, heatexchanger tubes, boiler tubes etc. Pipes are generally used to carry fluids and mustcontain them. They also have pressure rating andhence are scheduled. In tubes the thickness increases in standard steps like1 mm thick, 2 mm thick etc. In pipes however thethickness depends on the schedule of the pipe andthere is no fixed step.Page 6

The Basics of Pipes and Bends on Ships Pipe joining is more time consuming . For e.g. welding,threading, flanges with bolts etc. The tubes joining arefaster using flaring, brazing, couplings etc. Tube dimensions are actual dimensions. Whereas thepipe dimensions are only nominal. That means that a 1”tube will have actually OD as 1”. The pipes on the otherhand are named nominally, which means only for name.The 1” schedule 40 Nominal size pipe has an ID of 1.049”,OD of 1.32” and a wall thickness of 0.133”. Tube fittings are compression fittings such as ferrule andunion nut, flared fittings, biting fittings, mechanical griptype fittings. The pipe fittings on the other hand are pipeto pipe butt welding, threaded pipe fitting connectors,flange to flange bolted fittings etc.Page 7

The Basics of Pipes and Bends on ShipsWhat is Nominal Diameter?The dictionary meaning of nominal is, “existing in nameonly”. For example a 250 A nominal size pipe has an ID of242.8 mm and OD of 273 mm and as per schedule 80. Butinstead of saying 242.8 mm IDF pipe with wall thickness of15.1 mm, we say 250A, SH80. It is easier to speak andremember.Nominal diameter is the approximate inner diameter of thepipe. It is a rounded figure easier to use and remember. Byprescribing the nominal size of the pipe, all different fittingscan be selected based on the same nominal diameter,without physically checking the dimensions and compatibilityof each component.Nominal diameter is not the internal diameter but is similarto it. With reference to the above example the nominal boreof the pipe is 250 mm, but the ID varies from 266.2 mm to222.3 mm depending on schedule of the pipe.“Nominal diameter isthan a size.”Page 8more of a label

The Basics of Pipes and Bends on ShipsSchedule of Pipes: What does it mean?In marine field we generally use schedule 40 for light dutyand schedule 80 for heavy duty. There are however manyother schedules which have been incorporated due toimprovement in metallurgy and requirements due toincreased pressure demands.Basically the schedule of a pipe refers to its pressure rating.The higher the schedule the higher pressure it can contain.The schedules are normally 5S, 10S, 10, 20, 30, 40S, 40, 60,80 100, 120, 140 and 160. As the schedule increases thewall thickness increases and the ID deceases.“The higher theschedule number,the thicker is the pipe.”Page 9

CHAPTER 2:Bend & ElbowBends and elbows are important parts of any pipingsystem as they allow the integration of flexibility ofdesign by change in the flow direction of the media to becarried insideThe details of these important components arediscussed in this chapterPage 10

The Basics of Pipes and Bends on ShipsBend or ElbowThere is always a doubtabout the terms bendsand elbows on ships.They are frequently used as synonyms. The differencebetween them is as follows: Bend is a generic term for any offset or change ofdirection in the piping. It is a vague term that alsoincludes elbows. An elbow is an engineering term and is classified as 90deg or 45 deg, short or long radius. Elbows have industrial standards and have limitations tosize, bend radius and angle. The angles are usually 45deg or 90 degrees. All others offsets are classified aspipe bends.Page 11

The Basics of Pipes and Bends on Ships Bends are generally made or fabricated as per theneed of the piping; however elbows are prefabricated and standard, and are available off theshelf. Bends are never sharp corners but elbows are. Pipebending techniques have constraint as to how muchmaterial thinning can be allowed to safely contain thepressure of the fluid to be contained. As elbows arepre fabricated, cast or butt welded, they can be sharplike right angles and return elbows which are 180degrees. Elbow is a standard fitting but bends are customfabricated. In bends as the pipe is bent and there is no weldinginvolved, there is less pipe friction and flow issmoother. In elbows, the welding can create somefriction. All elbows are bends but all bends are not elbows. Bend has a larger radius then elbows.Page 12

The Basics of Pipes and Bends on Ships Generally the most basic difference is the radius ofcurvature. Elbows generally have radius of curvaturebetween one to twice the diameter of thepipe. Bends have a radius of curvature more thantwice the diameter.Short Radius and Long RadiusElbows are again classified as long radius or short radiuselbows. The difference between them of the length andcurvature.Following are some points to differentiate these two: Long radius elbows give less frictional resistance tothe fluid than the short elbows. Long radius elbows create lesser pressure drop thanshort radius elbows. Short radius is less costly than long radius elbows. The short radius elbows are used where there isscarcity of space.Page 13

The Basics of Pipes and Bends on ShipsA short radius elbow will begiving the piping a sharper turnthan a long radius elbow.In a long radius elbow theradius of curvature is 1.5 timesthe nominal diameter. In astandard elbow the radius ofcurvature is 1.0 times thenominal diameter of the pipe.In addition to this classification the elbows of 45 degrees,90 degrees and 180 degrees are called as a return elbow.Page 14

The Basics of Pipes and Bends on ShipsMiter bendsAnother type of bend is a Miterbend. A Miter bend is a bendwhich is made by cutting pipeends at an angle and joining thepipe ends. A true miter bend isa 90 degree bend made bycutting two pipes at 45 degreesand joining them bywelding. Similarly three pipescut at 22.5 degrees will give a90 degree miter bend.“Mitered bends are simple to makeand can be readily compensated to actacoustically.”Page 15

CHAPTER 3:Types of ElbowWithout elbows, it is impossible to think of a piping systemon ship, especially in a limited place of installation. Elbowsgive flexibility for directing and building the piping systemleading to saving of space and material.Different types of elbows are used in the piping system ofships as per the space and design of installation.Page 16

The Basics of Pipes and Bends on Ships Female ElbowA female elbow is a pipe fitting thatis used to change the direction ofthe piping and has female threadson both sides, which allow for fixingpipes or fittings with male threads.They come in various angles like 45degrees and 90 degrees. Male ElbowA male elbow is a fitting with malethreads on both sides and is used forchanging the direction of the piping.They fix on to female threads of thefittings on both sides. They come invarious angles like 45 degrees and90 degrees.Page 17

The Basics of Pipes and Bends on Ships Street ElbowA street elbow is different from themale and female elbows in therespect that it has a male thread onone side and a female thread onother side. The advantage of usingthe street elbow is that it candirectly fix to the pipe withoutconnecting a nipple. They come invarious angles like 45 degrees and90 degrees. Reducing Street ElbowA reducing street elbow is a pipefitting that has male thread on oneside and unequal female threads onother side. They are used foraltering the direction of flow as wellas joining pipes of two differentsizes. They come in various angleslike 45 degrees and 90 degrees.Page 18

CHAPTER 4:Types of NippleA nipple is basically a pipe with male threads on each sideto facilitate joining two pipes or fittings with similar femalethreads.It is made by cutting threads on both sides of a pipe by die ora suitable process. The nipples may be short or long.Page 19