Field Testing of ConcretePipelines and Joints

Concrete PipeAssociationof AustralasiaACN 007 067 656

TECHNICALBULLETIN

CONTENTS

ABSTRACT

1 INTRODUCTION

2 OVERVIEW OF TEST METHODS

3 HYDROSTATIC TESTING NON PRESSURE PIPELINES3.1 Introduction3.2 Purpose of Test3.3 Test Criteria3.4 Preparation and Procedure3.5 Test Assessment

4 HYDROSTATIC TESTING PRESSURE PIPELINES4.1 Introduction4.2 Purpose of Test4.3 Precautions4.4 Test Procedure4.5 Test Acceptance

5 INDIVIDUAL JOINT TESTING5.1 Introduction 5.2 Test Criteria5.3 Preparation, Precautions and Procedure 5.4 Test Acceptance

6 AIR TESTING NON PRESSURE PIPELINES6.1 Introduction6.2 Features of Air Testing6.3 Special Requirements6.4 Safety Aspects

APPENDIX A Test Procedure for Air Testing of Concrete Non Pressure Pipelines

CONCRETE PIPE ASSOCIATION OF AUSTRALASIA

FIELD TESTING OF CONCRETE PIPELINES AND JOINTSPUBLICATION SECOND EDITION 1995

ABSTRACT

Although rigorous tests are specified in Australian and New Zealand Standards for client acceptance of pipesbefore delivery, the development and establishment of standard test procedures for checking the integrity of an installed pipeline have often been neglected.

New Zealand practice for non-pressure pipelines is covered by New Zealand Standard NZS 4452:1986“Code of Practice for the Construction of Underground Sewers and Drains”.

In this document four separate test methods are outlined in an attempt to standardise the application of fieldtesting in Australia and ensure a high quality pipeline.

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Key: A – jointing performed correctlyB – rubber ring positioned correctlyC – no damage to line during layingD – line will resist the pressure for which it was designed

Table 1 Summary of Test Methods and Their Application

This test demonstrates CommentsTest and

Field test for medium A B C D limitations

Non pressure pipeline Water Yes Yes Yes YesPressure pipeline Water Yes Yes Yes YesPipeline joint Water Yes Yes No No See Note 1Non pressure pipeline Air Yes Yes Yes No See Note 2

1 INTRODUCTIONAustralian and New ZealandStandards for precast concrete pipemake provision for hydrostaticpressure testing for rubber-ringjointed pipes.

Routine factory hydrostatic pressuretesting is undertaken for drainageand sewerage pipes only wherespecified by the purchaser at thetime of order. It is, however,mandatory for pressure pipes.

Field testing of concrete pipelinesand joints is applicable only topipes which have been subject toroutine factory hydrostaticpressure testing by themanufacturer.

Within Australia and New Zealand,and elsewhere the worldAuthorities, Consultants and othershave from time to time producedrecommended procedures forchecking the integrity of a pipelinesubsequent to laying. These havediffered markedly in certainaspects.

It is the aim of this document torectify this situation for concretepipelines and standardise theapplication of these tests withinAustralia.

New Zealand practice is coveredby New Zealand Standard NZS4452:1986 “Code of Practice forthe Construction of UndergroundSewers and Drains”.

2 OVERVIEW OFTEST METHODS

Various field tests are in use toensure the integrity of concretepipelines. These, together withtheir correct application arediscussed in the following sectionsand summarised in Table 1 as it isimportant that these tests are usedfor the correct reasons and in thecorrect manner. The various testsare:

• Field testing of rubber ring jointnon-pressure pipelines byapplication of a hydrostatic test(Section 3)

The purpose of this test is tocheck that the jointing has beenperformed correctly and the rubber ring properly located. It is intended to pick up anyfault that has occurred duringthe laying process.

• Field testing of reinforcedconcrete pressure pipelines bythe application of a hydrostatictest (Section 4)

This test may be applied to anydiameter of pressure pipeline forthe purpose of:

(a) revealing the occurrence offaults in the laying procedure,eg incorrect jointing methodsor pipes damaged.

(b) ensuring that the pipelinewill resist the sustainedservice pressure.

• Field testing of individual rubberring joints in installed reinforcedconcrete pipelines (Section 5)

This test is used to establish that each jointing operation hasbeen performed correctly andthe rubber ring is in position. It is not appropriate for use onsmall pipes and is recommendedfor diameters over 1200 mm.

• Field testing of non-pressureconcrete pipelines by theapplication of an air test (Section 6)

This test uses low pressure airand is only applicable where it ismore convenient than using thehydrostatic test. It can providethe criteria for acceptance of apipeline but not for its rejection.

Notes:

1 The joint test is not in anyway equivalent to a line testat the specified test pressureand must not be used assuch.

2 When unacceptable leakagerates occur during the air testthe contractor has the optionto revert to the hydrostatic(water) test, ie air testing pro-vides criteria for acceptanceof a line but not for rejection.

3 HYDROSTATICTESTING NON PRESSUREPIPELINES

3.1 IntroductionConcrete drainage and sewerpipes are manufactured to meetthe requirements of Australianand New Zealand Standards.For rubber ring jointed pipe theseStandards provide an option forthe purchaser to specify a hydro-static test on each pipe before itleaves the factory.

To ensure that the pipes are stillin good condition and have beencorrectly laid a low pressurehydrostatic test can also beapplied to the pipeline after it hasbeen laid. The test is a goodindicator of the integrity of theline because it simulates serviceconditions. It is relatively simpleto perform and can be applied tothe full range of diameters ofrubber ring joint drainage andsewer pipelines. It should not beapplied in the same manner topressure pipelines, eg water supplyor irrigation installations, for whichthe equivalent test procedures andacceptance criteria must be morestrict.

It should be noted that this fieldtest is not intended to reassessgeneral pipe permeability as theoriginal factory test is designedto do.

3.2 Purpose of TestWhen so determined by the owneror principal that a hydrostatic test isto be carried out, this should be doneafter laying the pipes and placinganchors, but before completingback-filling or placing surroundconcrete. The test is designed toreveal the occurrence of damagedpipes, joints incorrectly installed,or other laying deficiencies.

3.3 Test CriteriaThe pipe when tested under aminimum head of 1.2 metres anda maximum head of 6 metres shallnot show any leakage in excess of0.5 litre per hour per linear metreper metre of nominal internaldiameter. The minimum andmaximum heads specified shallbe measured above the internalcrown of the pipe.

3.4 Preparation andProcedure

By fitting temporary bulkheadsthe test can be applied to thecompleted pipeline or progressivelyto sections as laid. Depending onthe grade some pipelines must betested in stages otherwise maximumhead could be exceeded.All bulkheads must be suitablystrutted and restrained, and plugsmust be similarly fitted at anyinlet/outlet connections.

Whenever possible testing shouldbe carried out from manhole tomanhole. Short branch drainsconnected to a pipeline betweenmanholes should be tested as onesystem with the main pipeline.Long branches and manholesshould be separately tested.

For the purpose of filling the lineand obtaining the required 1.2metres head above the crown atthe high point of the test section,a water entry point must beprovided through the temporarybulkhead. It is suggested that aflexible hose be attached to thisfitting.

To obtain the correct head leveland also to enable the leakage rateto be simply estimated, a drum orcontainer should be attached tothis hose. The drum which shouldbe calibrated by marking with alitre scale is then supported so thatthe top mark of the scale is at1.2 metres above the crown of thepipe. This is the reference markand by noting the time and rate offall an estimate of the leakage ratecan be quickly obtained.

When filling there must be provi-sion for air to bleed out or escapefrom high points. After filling, thewater level will initially fall due to:

• absorption into the pipe wall

• air which is trapped at jointsneeds time to escape.

Allowance should be made for thisby adding water to maintain somehead on the pipe for an appropriatestabilising period before themeasuring time commences.This stabilising time will dependon factors such as the age of thepipes, their moisture condition,ambient conditions, etc. It willusually be of the order of 24hours. Whilst the aim is tocommence the test proper as soonas possible, the appropriate periodwill best be determined byconferring with the pipe suppliers.

At the end of the stabilising periodthe head of water is adjusted backto the correct level. The loss ofwater over a period of 30 minutesis then measured by adding waterand noting the quantity required tomaintain the correct water level.The average quantity added shouldnot exceed the equivalent leakagerate as specified under the test cri-teria in Section 3.3. above.

3.5 Test AssessmentWater loss in excess of the specifiedrate may be due to a defect.The line should be inspected andif a defect is detected by visiblesigns of leakage then remedialaction is to be taken.

If no defect is found then it maybe that the stabilising period wasinsufficient and after a furtherwaiting period the test should bere-run.

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DIAGRAM OF HYDROSTATIC TESTING BETWEEN MANHOLES

4 HYDROSTATICTESTING PRESSUREPIPELINES

4.1 IntroductionAustralian and New ZealandStandards require routine factoryhydrostatic pressure testing ofconcrete pressure pipe.

To ensure pipes are being correctlylaid and jointed, a field hydrostatictest can be applied. Temporarybulkheads will have to be installedat the ends of the pipeline orsection of pipeline to be tested.

This field test is not to be appliedfor the purpose of reassessingindividual pipe performance.The manner in which the pipeshave been treated and theconditions to which they havebeen subjected prior to and duringlaying may have affected theperformance of the pipeline.It is well recognised that initialleakage may occur through soundconcrete pipes if they have beenstored on-site for an extendedperiod. Desirably such storageshould be minimised by installingpipes as soon as possible,preferably before they dry out.

Pipes may show initial damp spotsor weeps which will graduallydiminish with time. This may notbe the case if the damp sports arethe result of damage.

4.2 Purpose of TestThe purpose of a hydrostatic test isto:

• reveal the occurrence of faults inthe laying procedure, eg jointsincorrectly installed or pipesdamaged.

• ensure that the pipeline willresist the sustained internalservice pressure to which it willbe subjected.

4.3 PrecautionsIt is recommended that backfillingbe partly completed before the testis applied, to minimise the chancethat pipes will 'float' in trencheswhich become accidentally filledwith water.

It is important that a pipeline to betested be properly restrained toprevent movement of pipes,bends, tees, junctions, adaptors,and reducers. It is recommendedthat straight sections of pipeline beprevented from moving out ofalignment by placing adequatesidefill to restrain the pipe.Excessive deflection of any pipedue to internal pressure may resultin a failure at a joint.

4.4 Test ProcedureIt is desirable to conduct an initialtest as soon as possible after thefirst 500 metres of line has beenlaid and jointed, as an early checkon the standard of pipelaying. Thefeasibility of doing this willdepend on the rate of laying andwhether the delay to pipelayingcan be accommodated.

Considerable care and attentionmust be given to the provision andfixing of adequate bulkheads,which must be properly designedto prevent blow out and leakage.Such leakage unless monitored,can confuse the final test result.

The preconditioning of the line isimportant. It should be allowed tostand under some hydrostatic pres-sure say, up to 50 kPa at the high-est point on the line for as long aperiod of time as necessary toallow absorption of water by theconcrete. Time taken will dependon the age, moisture condition ofthe pipes and the ambient siteconditions. Some lines will needno more than 24 hours beforepressurisation commences, othersmay need longer.

Pressurisation should be carriedout slowly and can begin at50 kPa per hour. A guide to therate of pressure increase can beobtained at any stage by measuringthe rate of loss, ie the leakage perhour, and checking how thiscompares with the rate given by

the formula below. If the rate issubstantially above this there islittle point in raising the pressurefurther at this stage. Furtherpreconditioning should be appliedif there are no obvious leaksoccurring anywhere along the line.

Once the pressure has reached thespecified test pressure for the lineand provided no major faults haveappeared the loss of water shouldbe measured at hourly intervals,over a period of three hours.If these measurements show asteadily decreasing rate of leakageit indicates that the test sectionof line has not yet reachedequilibrium. In this event it maybe necessary to allow a furtherperiod of preconditioning andthen repeat the measurement.The test result may be consideredsatisfactory when the amount ofwater lost in one hour does notexceed the amount defined by theformula expressed under testacceptance.

4.5 Test AcceptanceAt the specified site test pressurethe line shall not show anyleakage greater than that givenby the formula:

QL =

Where

QL litres/hour – leakage

N – number of jointsin the section ofline under test

d metres – diameter of pipe

P kPa – specified sitetest pressure

It is strongly recommended thatthe specified site test pressure benot greater than the sustainedworking pressure to which thepipeline will be subjected inservice.

Nd√P70

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5 INDIVIDUALJOINT TESTING

5.1 IntroductionJoint testing is generally limited tointernal diameter 1200 mm andupwards. Access to smaller diam-eters makes testing impracticable.

The purpose of a joint test is toestablish the integrity of the joint.It is not equivalent in any way to aperformance test for the line at fullpressure. However, it requiresvery little water and the equipmentis simple and safe to use.

5.2 Test CriteriaUnder a test pressure of 90 kPavisual assessment of moisture inthe form of water dripping orrunning from the external jointsurfaces is the accepted criterionof joint failure.

Assessment by pressure loss versustime is not practical because ofthe small volumes of waterinvolved and the initial absorptionof water into the concrete surfaces.

5.3 Preparation,Precautions andProcedure

The testing equipment consists of ashort internal annular ring, smallerin diameter than the minimumpipe bore. There are rubber seal-ing rings at each end of the cylin-der, so that the joint is effective-ly isolated.

The Concrete Pipe Association canadvise on the general arrangementof this equipment.

The test is performed by positioningthe mobile test equipment so thatit seals across the joint to be tested.For maximum benefit this jointshould be as close behind thelaying as is practical. Because ofthe end thrust transmitted bypressure on the vertical endsurfaces of the pipe joints the testneeds to be at least three pipesbehind the laying face of the line.

Water is pumped into the spacebetween the joint and the sealsuntil a pressure of 90 kPa isreached.

5.4 Test AcceptanceAs previously outlined the assess-ment of the joint integrity is basedon a visual inspection of theexternal joint surfaces for moisturedripping or running whilst thepressure is maintained.

Although there is necessarilysome small pressure drop withtime (ie absorption into theconcrete surfaces under test) thetest is still sufficiently sensitivefor an experienced operator todistinguish between a sound jointand a defective joint.

Joint test rig being prepared.

Joint test rig in-situ.

6 AIR TESTING NONPRESSUREPIPELINES

6.1 IntroductionThe most reliable proof test of theworkmanship in a laid concretepipeline is by the application of ahydrostatic test but it is not alwaysconvenient to carry this out.There can be problems or excessivecost in obtaining water at somelocations, and then in disposingof it afterwards.

Instead of the hydrostatic test itmay be possible to apply a lowpressure air test. However,pipelines will tend to show greaterand more variable permeability toair than to water, so care is neededin applying the air test and ininterpreting results. Althoughresults of air tests and water testsdo not correlate very well asatisfactory air test can serve as auseful indication that a line willpass a water test.

6.2 Features of Air TestingThe test procedure recommendedby the Concrete Pipe Associationof Australasia is given in Appendix A

Points to note in the application ofair tests are as follows:

• Pipes are more permeable to airthan they are to water. They willalways show a basic but smallamount of air leakage per unit ofarea of the pipe wall. This leak-age, which is called the basicpermissible leakage rate, asmeasured by a pressure drop,might vary considerably (possiblyby a factor of five times) indifferent pipelines, which wouldall be quite satisfactory in awater test.

• The basic air leakage is consid-erably affected by the degree ofdampness in the pipe walls,probably the main reason for thepoor correlation with water testresults.

• With a pipeline exposed tovarying ambient conditions,especially sunshine, the airtemperature within the pipe canbe subject to wide and rapidfluctuations. Being inverselyproportional to the temperature,the internal air pressure can besimilarly affected and as it is thispressure which is the measureof air leakage the resultantfluctuations can be wronglyinterpreted. It is possible tolargely overcome the effects ofvarying temperature by havingthe applied average pressuresufficiently high.

• Care is needed in making airtight seals at plugs, joints andpipes of the air test equipment.Again loss of air pressure at suchpoints, often difficult to detect,can be wrongly interpreted asbeing due to faults in thepipeline.

• As pipe diameters increase theair test becomes more hazardousbecause of the danger of endseals (which can have imposedloads of several tonnes) blowingout.

• Defects may not be easy tolocate with air tests.

• The test can be much too sen-sitive to leaks in short lengths ofsmall diameter pipelines andhave too little sensitivity to leaksin long lengths of large diameterpipelines.

Various air test procedures areused in overseas countries withnotable differences between themin the manner of application.These procedures were consideredwhen drafting the procedure recommended by the ConcretePipe Association of Australasia(see Appendix A), although mostreliance was placed on data fromAmerican sources.

The recommendation is notintended to be an unqualifiedendorsement of air testing which is not an accurate guide to perfor-mance under hydrostatic head, butis intended to standardise andavoid misapplication of the test.

It can provide the criteria foracceptance of a pipeline but notfor its rejection.

The option to carry out a watertest if the pipeline fails the air testmust always be available to theinstaller.

6.3 Special RequirementsIn fixing the permissible holdingtimes for the air test (ReferAppendix A) two limiting conditions need consideration:

• For long lengths of largerdiameter pipes the pipe wallarea and hence the basicpermissible leakage rate is high.A defect in the pipeline mightbe masked by the slow pressuredrop.

To overcome this disadvantageit is proposed that for larger pipediameters the allowable testlength should be generallyrestricted to lengths betweenmanholes (the most convenientplaces for fixing temporary bulk-heads), and should not apply tolengths in excess of 100 metresnor to pipes larger than 1200mm in diameter.

• For small pipe wall areas, iesmall diameters and shortlengths the calculated volumeleakage rate is small and thepermissible holding time is verylow. If the average pipe wallpermeability is a little higherthan allowed for, then thiscombined with the experimentalerror means that the test is toosensitive.

To overcome this a minimumleakage rate has been set whichwill permit a reasonably accurate measure.

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6.4 Safety AspectsThe procedure for air testing largediameter pipelines is hazardousbecause of the very large forcesto be resisted by temporarybulkheads and the seriousconsequences of accidentalbulkhead blow out.

The bulkhead force increases asthe square of the socket diameterand the cost of maintaining safeworking conditions increasesrapidly with increasing pipediameter.

The American Concrete PipeAssociation advocates that airtesting is not practical in pipes ofdiameter greater than 1000 mmdiameter and beyond this it isrecommended to apply a waterpressure test to the joints only.Because the Concrete PipeAssociation of Australasia recom-mended procedure uses a reducedapplied pressure it is consideredthat pipes up to 1200 mmdiameter can be safely air tested,but beyond that diameter either aseparate joint test or a hydrostatictest should be adopted.

APPENDIX A

TEST PROCEDURE FOR AIR TESTING OF CONCRETE NON PRESSURE PIPELINES

1 The section of line to be tested should be flushed and cleaned. This serves to clean out any debris and wetthe pipe.

2 Isolate the section of line to be tested by means of inflatable stoppers or other suitable test plugs. The endsof all branches, laterals, tees or wyes to be included in the test should be plugged to prevent possibleblowout due to internal pressure. One of the plugs should have an inlet valve for connection to a source ofair under pressure.

3 Prior to setting up the air test, ensure that ground water is not leaking into the isolated section of the line.

4 Connect the air hose to the inlet tap and a portable air control source. The air equipment should consist ofnecessary valves and pressure gauges to control the rate at which air flows into the test section and to enablemonitoring of the air pressure within the test section. Also, the testing apparatus should be equipped with apressure relief device to prevent the possibility of loading the test section with the full capacity of the compres-sor.

5 Add air slowly to the test section until the pressure is just over 1000 mm of water. Regulate the air supplyto maintain the pressure between 1000 and 1100 mm head whilst checking all plugs, bulkheads and fittings,with soap solution if necessary, to ensure there is no stray leakage. This period, which should be a mini-mum of two minutes, also allows the air temperature to stabilise with the temperature of the pipe walls.

6 After the stabilisation period ensure that the pressure is just above 1000 mm head. Commence measuringtime as the pressure falls to 1000 mm and note the time taken for it to drop another 200 to 800 mm head.For the pipe to pass the test this time should not be less than the holding time given in Table A.1 appropriateto the diameter and length of line under test.

7 If the pipeline fails the test the cause of the failure must be detected by audible or visual means and rectifiedand the test repeated. If no defect can be detected the installer can either:• apply water to the pipeline internally and/or externally and then repeat the air test, or• apply a hydrostatic test to prove that the pipeline is sound.

Table A.1 Air Test Holding Times (mins–secs) for an Average Applied Pressure of 900 mmHead of Water (ie falling from 1000 to 800 mm head)

Pipe Length of test section (metres)dia.

(mm) 15 20 25 30 35 40 50 60 70 80 90 100

150 0–13 0–17 0–22 0–25 0–30 0–35 0–45 0–50 1–00 1–10 1–20 1–30225 0–30 0–40 0–50 1–00 1–10 1–20 1–40 2–00 2–10 2–10 2–10 2–10300 0–50 1–10 1–30 1–40 2–00 2–20 3–00 3–00 3–00 3–00 3–00 3–00375 1–20 1–50 2–20 2–40 3–10 3–40 3–40 3–40 3–40 3–40 3–40 3–40450 2–00 2–30 3–10 3–50 4–20 4–20 4–20 4–20 4–20 4–20 4–20 4–20525 2–40 3–30 4–20 5–10 5–10 5–10 5–10 5–10 5–10 5–10 5–10 5–10600 3–30 4–30 5–50 5–50 5–50 5–50 5–50 5–50 5–50 5–50 5–50 5–50750 5–20 7–10 7–10 7–10 7–10 7–10 7–10 7–10 7–10 7–10 7–10 7–10900 7–40 8–50 8–50 8–50 8–50 8–50 8–50 8–50 8–50 8–50 8–50 8–50

1050 10–10 10–10 10–10 10–10 10–10 10–10 10–10 10–10 10–10 10–10 10–10 10–101200 11–40 11–40 11–40 11–40 11–40 11–40 11–40 11–40 11–40 11–40 11–40 11–40

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DIAGRAM OF AIR TEST ARRANGEMENT

AUSTRALIAN OFFICE:Locked Bag 2011St Leonards, NSW 2065Phone (02) 9903 7780Fax (02) 9437 9478

NEW ZEALAND OFFICE:26-30 Prosford Street,(PO Box 47-277)Ponsonby, Auckland, NZPhone (09) 378 8083Fax (09) 378 6231

MEMBER COMPANIES:ATHLONE CONCRETE PIPESBCP PRECASTCSR HUMESHUME INDUSTRIESHYNDS PIPE SYSTEMSMIDLAND CONCRETE PIPESROCLA PIPELINE PRODUCTS

DISCLAIMERThe Concrete Pipe Association ofAustralasia believes the information givenwithin this brochure is the most up-to-dateand correct on the subject. Beyond thisstatement, no guarantee is given nor is anyresponsibility assumed by the Associationand its members.

Second Edition: October 1995Publication No. TB6/95

Concrete PipeAssociationof AustralasiaACN 007 067 656