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10

3R international · International Edition 2007

Modern methods of installing dependable hydrants

By Marc van den Bosch, Bernd Schuster and Manfred Schmidt

In cases of fire outbreaks, a constant and reliable supply of water must be readily avail-able to enable the fire fighters to complete their allotted task. At the same time the watersupply utilities are obliged to take the necessary measures to ensure that a piping net-work can be effectively filled, vented, flushed and drained as well as to be able to providetemporary or emergency supplies through the use of hydrants. Each and every pipelinecomponent installed up to the hydrant outlet must function in a reliable manner. Otherfactors such as traffic flow, space requirements and hydrant type must be taken into con-sideration during the installation of such water hydrants. This paper is intended to givean overview of the products and methods in use today as well as future developments inthis direction.

Hydrant systems

Fundamentally, there are two distinctly dif-ferent types of hydrant; one is designed to beinstalled below the surface of the groundwhilst the other is conceived for aboveground installation. The respective standardapplicable for installation in potable watersystems for the underground types is DIN3321 whilst DIN 3222 applies to the aboveground types. The dimensions of belowground hydrants are in accordance with the

commonly used installation depths of1.00 m, 1.25 m and 1.5 m. In Germany, theunderground hydrant type finds more fre-quent usage due to its low purchase price,light weight and resultant simplified installa-tion procedure coupled with the fact this var-iation offers no hindrance or hazard to roadtransport. However, wherever it is necessaryto have a rapid site location, perhaps duringhours of darkness or even after snowfall, fastwater extraction with large throughputs, theabove ground or so-called stand post hy-drants are much preferred.

Both versions of these two hydrants can besub-divided into two shut-off patterns; thesimple shut-off and the double shut-off type.Double shut-off hydrants have two separateshut-off systems (Figure 1), which also en-ables all maintenance and repair work to becarried out under full working pressure. Sim-ple shut-off types require an additional shut-off valve. The current trend is clearly towardsdouble shut-off hydrants due to fundamentalinstallation reasons and those of costs.

Reliable and safe hydrants

Modern underground hydrants should fulfilthe following requirements:

■

Double shut-off design

■

Fast and efficient exchange of the valveunit

■

Safety inter-locking of the inner assembly

■

One piece outer body

■

Integrated multi-functional seal

■

Optimum drainage.

Double shut-off design

During recent years the hydrant types pos-sessing an extra shut-off (

Figure 1

) havefound increased interest amongst users. Amajor advantage is that when exchangingthe inner parts there is no necessity to shut-down the flow of the medium in the mainline. In this way any additional shut-off is notrequired.

Fast and efficient exchange of the valve assembly

The reason behind the exchange of the en-tire inner unit is usually the result of damageto the rubber sealing on the valve cone. Thedesign of the valve cone containment mustbe made in such a way so that it can be ex-changed without difficulty and is also avail-able as a separate assembly complete withall relevant parts.

The economics behind the provision of aseparate valve cone lie not only with the re-use of valuable parts such as pressure pipeand spindle nut, but they also include thepossibility to use the identical cone for both

Fig. 1:

Underground hydrant with double shut-off; ball body with flanges

Fig. 2:

Hydrant with safety mechanism

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underground and above ground standposthydrants at all depths of pipe cover.

Safety inter-locking of the inner assembly

Uncontrolled internal pressure can representa hazard to maintenance personnel whenworking on opened-up hydrants. A safety in-ter-locking mechanism prevents the suddenejection of the inner assembly in such cases.

Following removal of the bonnet any internalwater pressure will force the inner assemblyupwards. However, a fixed stop prevents anunexpected and possibly dangerous ejectionof the inner unit. The assembly can be sub-sequently unlocked with a turning action andthen removed (

Figure 2

).

One-piece outer body

The conception of a one-piece outer bodyrepresents a substantial advancement (

Fig-ure 3

). Otherwise a flange connection be-tween the outer body and housing aroundthe double shut-off itself (Figure 1) would benecessary. Leakages can no longer occur atthis point. Additionally, an enormous weightsaving is achieved considerably easing trans-port and installation.

Integrated multi-functional seal

As can be seen in the sectioned hydrant (Fig-ure 3) the cone for the additional shut-off isassembled from below. A plastic reinforcedsealing ring set in the connector flange

serves primarily as an integrated seal to theflange used to attach the pipeline. Neithersupports or adjustment is necessary, as atiresome lining-up of the loose flange gasketis avoided. Assembly can be achieved easilyand without great effort.

Furthermore, this seal retains the cone inthe outer casing. When filling sections ofpipeline from the hydrant, four cams serveas a seat for the cone and provide the ne-cessary free cross-sectional area betweencone and outer casing.

Optimum drainage

As a result of tests on more than 50,000 un-derground hydrants from 20 utility compa-nies, it was established that for approximate-ly 9,000 hydrants, the most common causeof a malfunction (

Figure 4

) was a defective(blocked) drainage system. Such faults canoften only be remedied following time con-suming and costly repairs (e.g. drilling outthe drainage channel). In many cases it isnecessary to dig out and exchange the com-plete hydrant. The resultant costs in manycases exceed the original procurement priceby up to ten times. For these reasons it isvery important to pay close attention to thedrainage method adopted for the hydrant inquestion. Ideally, hydrants should possess awater drainage channel from a non-corrosivematerial (

Figure 5

) in order to prevent a po-tential build-up of corrosion. Just as impor-tant is to integrate a tapered design for thedrainage channel to prevent any possibleblockage caused by foreign bodies (stones,sand).

The VAG hydrant types UH SUPRA and UEHNOVA fulfil the afore-mentioned points in allrespects. Above ground hydrants should onlybe of the robust and maintenance-free types

Fig. 3:

Underground hydrant with one-piece body

Fig. 5:

Optimum drainage

Fig. 4:

Damage frequen-cy for underground hydrants

Fig. 6:

Standpost Hydrant VAG NIVO NIRO

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such as the VAG NOVA NIRO (

Figure 6

) andpossess the following characteristics:

■

all above ground components to be fromcorrosion resistant materials

■

have a chalk resistant polyester coating ina bright fade-proof, warning colour

■

if aluminium alloys are used, these are tobe corrosion and salt water resistant

■

hydrant head to be directionally adjusta-ble with a free orientation

■

have a reliable by-pass system

Pipelines

There has been an extensive network of wa-ter distribution pipes in Europe since the19

th

century. Cast iron was the predominantmaterial up to the 2

nd

world war. Pipes fromthis material were originally connected to-gether using flanges and then later overlap-ping jointing methods were used. However,cast iron as a piping material was substitut-

ed successively by ductile cast iron as wellas various plastics. Until the end of the1980’s PVC was the dominant plastics ma-terial but today, pipes in PE are normallyused.

As a result of the historical background, a va-riety of methods have been created to couplethe various pipeline materials with their dif-fering jointing techniques to hydrants. Partic-ular attention must be given to the point ofconnection. The chances of a leakage occur-ring reduces in adverse proportion to thenumber of joints in use whatever quality theypossess.

Types of hydrant connection

In principle there are three different configu-rations. The choice is usually dependantupon the actual hydrant itself, local condi-tions as well as the customs practised by the

network engineer. These configurations areas follows:

■

direct mounting on the mains pipe

■

off-set to the mains pipe

■

as end hydrant or in feeder line.

Table 1

illustrates the different characteris-tics and particulars.

Applied connection methods

The flange connection is the classic way fortying a hydrant and other valves into a pipe-line network. Unfortunately, this jointingtechnique is especially susceptible to agingand this is the reason why it has been givenparticular attention.

As with joining pipelines, the overlappingpush-fit joint finds increasing popularityfor hydrants. The BAIO Plus

®

system (

Fig-ure 7

) is the principle method in use for hy-drants because a positive locking system as-sures for the necessary retention and safety.

When applying modern, heat fusible plasticmaterials an increased demand exists forjointing methods which, like for pipe connec-tions, ensure the highest levels of reliabilityand a long working life.

Classic methods of attaching hydrants

Tying into cast-iron pipelines

As a rule cast-iron pipes are joined togetherusing overlapping jointing techniques.Should it be necessary to install a hydrant,this is accomplished by using standard fit-tings (

Figure 8

), which allow a direct up-right assembly, an off-set installation andwhich can also be used for the various stylesof hydrant attachment.

Tying into PVC piping

Lengths of PVC pipe are joined together us-ing specially designed push-fit fittings fromeither cast-iron or PVC. Flanges are generallyused when installing a hydrant into such pip-ing systems. Ancillary fittings (

Figure 9

)from cast-iron or PVC permit an off-set at-tachment. A direct vertical mounting is usu-ally avoided for various reasons.

Table 1

Fig. 7:

Underground hydrant with BAIO Plus

®

bayonet connection

Fig. 8:

Hydrant assembled directly above cast-iron mains

Fig. 9:

Combination of PVC tee and cast-iron ducks-foot bend

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3R international · International Edition 2007

Tying into PE piping

Heat fusion tees are used almost without ex-ception when installing hydrants in PE pipe-lines. The hydrants are either mounted di-rectly above the mains line or are mountedin an off-set manner. In such cases a combi-nation similar to that illustrated in

Figure10

is generally used.

Modern concepts for installing hydrants

The demands and requirements for the pro-cedures applied when installing hydrantshave altered. Changed environmental factorsand constant technical progress necessitaterevised needs. Amended environment-relatedconditions such as the constant need to re-duce costs, traffic densities or rehabilitationinstead of replacement, just to mention a few,demand an optimisation of installation meth-od and a more refined product. The constanttechnical progress taking place with respectto pipeline materials and installation practicesencourages a rethinking of traditional meth-ods and applied products. As a subject “In-stallation of Hydrants” has clearly defined is-sues which are extensively covered in variousstandards, instructions and codes of practice.Minimum throughput performance levels forhydrants and standardised coverage for pipesare typical examples of these. With respect tothese new fundamental requirements the fol-lowing section describes application possibili-ties using new products, modern techniquesand case histories.

Hydrant bases for PE and other pipe materials

All ducks-foot fittings (

Figure 11

), whetherfor PE or other pipeline materials, for hy-

drants with PE stub ends or with flange con-nections, must fulfil their purpose with com-plete safety. The purpose of a hydrant foot isto prevent the product sinking into the earthdue to its own weight or through traffic load-ing. This must be assured over the entireminimum working life of 50 years. The sec-ond reason for the hydrant foot is effectiveimmediately following the initial installation.Until the final fixation after backfilling iscomplete the hydrant must remain upright inan absolutely vertical position. Before then,it has to withstand winds, weather and thedaily hard conditions experienced on build-ing sites. These conditions often prevail formany days or even weeks until the trench isfilled or the manhole cover is finally at-tached.

Most hydrants are tied-in to a pipeline net-work using flange connections. The flangeconnection represents the absolute classictechnology ever since there have been hy-drants. It is clearly obvious that the more

modern methods to install hydrants shouldbe also taken into consideration. Thisthought is applicable for both metal and forplastic solutions irrespective of which pipe-line material is being used. Furthermore, hy-drants with PE stub ends have been avail-able for some time now. Such products canbe fused directly into a mains network.Therefore, an assurance is given that thecomplete system has an identical system ofjointing throughout. Thus differences withinthe system regarding concerns for aging,pressure resistance and flexibility of the ap-plied product, are deliberately avoided.

A ducks-foot bend made entirely from PEwith integrated ELGEF Plus

®

electrofusiontechnology especially designed for hydrantapplications is on offer. A MULTI/JOINT

®

ducks-foot bend is also available which issuitable for all materials including PE. Incontrast to the version completely from PE,which is designed for flange connections aswell as direct fusion jointing, the metal

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Fig. 10:

Combination of PE fitting and cast-iron ducks-foot bend

Fig. 11:

Ducks-foot bend with MULTI/JOINT

®

couplings

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3R international · International Edition 2007

ducks-foot bend is more popular for flangingto hydrants. Although influenced by the ma-terial in question, the all-metal version re-mains decidedly more flexible in use be-cause of the proven multi-dimension me-chanical pipe coupling it is equipped with.Another advantage is that such couplingsare end-load taking for all pipe materialtypes. As no-one knows the local conditionsand requirements better than the respectivenetwork operator, the decision should be leftto him if the choice should be, flexibility atthe attachment and to remain standard forthe mains pipe, or alternatively, to be stand-

ardised for the connection and then main-tain flexibility at the mains pipe. However,whatever the final decision, Georg Fischerhas a suitable solution.

Integrated service connection avoids standing water

Water quality and hygiene are becomingmore and more important in today’s world.Hygiene in particular, is a constant discus-sion topic amongst utilities, the media andduring public debates. According to EN 805feeder lines to hydrants, amongst otherthings, must be carefully considered. It isrecommended to install a service branch-offat the end of each feeder line to avoid a pos-sible build-up of stagnant water. In this waythe work to carry out a time-consumingflushing operation of the feeder line is eitherminimised or completely avoided. The sim-plest solution is to install a ducks-foot bendwith integrated service branch outlet. Suchfittings are available not only especially forPE but also for all other pipeline materials.

Connector fittings for PE piping systems

There are many utility companies that valuethe flexibility of PE as a pipeline material.Originally, house service connections weremade using one single piece of uncoiled PEpipe which was joined at one end to thebranch take-off at the mains and to a wall in-let fitting at the other end. Irrespective of thelength of the service no further connectionswere necessary between these two points.For the same reason many engineers appre-ciated the possibility to be able to uncoilPE pipes with outside diameters of up tod 180 mm in the same way from drums andin long lengths. In this manner, and like withno other material, trench-less installationprocedures could be adopted. Relining is an-other ideal application. It hardly makessense to interrupt an unbroken continuouslength of installed pipe just to insert abranch tee. In our opinion the branch fittingsfrom Georg Fischer +GF+ (

Figure 12

) offera considerable potential with respect to im-provements concerning installation proce-dures and overall cost savings. ELGEF Plus

®

branch fittings are available for all commonmains sizes and are equipped with outlet siz-es of d 90, d 110 and d 125 mm. An elec-trofusion socket is an integral part of the fit-ting so that a valve or flange adapter, for ex-ample, can be fused directly into the outlet.Branch fittings are therefore, both time-sav-ing and economical in use.

Draw-lock

®

Flanges for optimum transi¬tions from PE to metal

Transitions from PE to metal require studiedsolutions. PE has a tendency to creep under

high stress conditions. High stress levels canbe induced when flange or compressionjoints are over-tightened. The patented Draw-lock

®

(

Figure 13

) offers a viable transitionfrom PE to metal which is ideally suited toboth materials. Forces and stresses areequally distributed. The metal flanged endson tee and flange fittings permit the usualand familiar connections to metal valves.The range of Draw-lock

®

fittings offers anoptimal connection possibility for long-termreliable transitions using the proven metalflange jointing procedure.

PP-V flange for plastic flange connections

Special loose flanges should be used on thePE side of metal to PE flanged connectionsto prevent cold material creep. The V in theproduct name represents an integral v-shaped groove (

Figure 14

). Each grooveensures an even distribution of forces overthe shoulder of the stub end. The stressbuilt-up in the v-groove assists the tighteningtorque to produce an improved jointing ac-tion. The design of these PP-V flanges in-cludes an integral bolt fixation which effec-tively prevents a falling-out of the bolt duringthe assembly of the flange connection. Thisinstaller- friendliness and corrosion resist-ance reflect the hidden advantages of this in-novative loose flange.

Pipe support as foundation

Hydrants which are mounted directly on themains pipe can subject the pipe to radialstresses during the installation phase. How-ever, a pipe support can be placed as a sta-biliser under the PE mains in order to pre-vent any undesired radial movement awayfrom the vertical axis and resultant misalign-ment of the hydrant. This pipe support platealso acts as an ideal foundation for a mainspipe and represents an effective safeguardagainst any sinking of such pipes due to thehigh inherent weight of hydrants. These pipesupports can be used universally for the pipesizes from d 90 to d 160 mm. The supportincludes a strap which is used to attach thesupport beneath the respective pipe.

Application examples

Made entirely from plastic. Simple, elegant and corrosion-free

The simplest and most economical methodto create a lateral branch take-off from a PEpipe (

Figure 15a

) is by using a branch fit-ting. This particular fitting is tailor-made forthe installation of hydrants and is availablefor all mains and branch dimensions. Thisproduct is suitable for the installation of newpipelines as well as for extension work onpressurised networks. The design of the PEducks-foot bend is based on the well-proven

Fig. 12:

Saturn branch saddle

Fig. 13:

Draw-lock

®

Fig. 14:

PP-V flange

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3R international · International Edition 2007

ELGEF Plus

®

technology. A hydrant with PEstub ends can be electrofused directly intothe socket outlet, or, can be attached usinga flange adaptor and PP-V flange. This flangeis corrosion-proof and has the strength ofequivalent metal flanges. Another possibilityis offered by Georg Fischer +GF+ namely, aplastic ducks-foot bend with integratedflange outlet and service connection.

Subsequent installations, universal application

The stainless steel saddle (

Figure 15b

) al-lows all hydrants to be connected easily toany mains pipe. Additionally, suitable tap-ping equipment is available permitting un-der-pressure tapping. Therefore, and if so re-quired, a hydrant can be attached to a pres-surised mains. The MULTI/JOINT

®

ducks-foot bend can be supplied if necessary witha female thread incorporated in the body.This means that a service connection can bemade directly from the bend itself. Transitionfittings with metal threads from the ELGEF

®

Plus or POLY 16 ranges enable a simple con-nection to be made to a service line. Similar-ly, any trapped and subsequently stagnantwater will be avoided.

MULTI/JOINT

®

universal pull-out resistant couplings

MULTI/JOINT

®

tee pieces with flangedbranch connections (

Figure 15c

) enable aleak-tight tie-in of hydrants in all piping sys-tems quite independent of pipe material.These couplings are end-load taking up to aworking pressure of 16 bar and accept awide tolerance range of pipe outside diame-ters. In addition, MULTI/JOINT

®

fittings canbe installed under all weather conditions.

PE to metal transitions, material- matched flange connections with Draw-lock

®

The Draw-lock

®

transitions with flangedends (

Figure 15d

) permit an optimum tran-sition from PE pipes to metal hydrants. Theconnection is material-matched i.e. possiblestresses can be correctly absorbed. There isa variety of ways to install these transitionson PE pipes. Butt-fused or electrofusion ver-sions (tees) can be used for new installa-tions. At the same time, the transition fittingis recommended for use on pressurisedpipelines. Additional support can beachieved using pipe supports when mount-ing the hydrant vertically on a plastics pipe.

Conclusion

Both underground and above ground hy-drants are used for fire extinguishing purpos-es. Basically, there are two different types ofhydrant; the simple shut-off type and thedouble shut-off type. Many metal and plastic

material types have been used to date inpipeline construction but, nowadays, PEfinds the greatest usage for distribution net-works. Hydrants are either mounted directlyabove the mains line or are off-set. Tradition-ally, such hydrants are connected to the wa-ter supply system by means of flanges. De-mand for alternative methods, for example,BAIO Plus

®

is steadily increasing.

New techniques can be introduced to poly-ethylene network systems using the ELGEF

®

Plus range. The classic tee piece, can be re-placed by the use of branch fittings. Ducks-foot bends from PE are equipped with thevery well-proven electrofusion technology.Special loose flanges and product groupspermit highly reliable flange connectionsover the entire operational life span.

The MULTI/JOINT

®

range of fittings pro-vides optimum solutions for the ever-growingspheres of rehabilitation and maintenance.The same fittings can be used under all siteconditions and for all pipe materials.

Fig. 15:

a) Saturn branch fitting with ducks-foot bend from PE, b) Stainless steel saddle, c) MULTI/JOINT

®

tee with flanged branch, d) Draw-lock

®

flanged transition

Marc van den Bosch

Georg Fischer Rohrleitungs-systeme AG, Schaffhausen (CH)Market Segment Manager Gas and WaterTel. +31(0)653/267444E-mail: marc.vandenBosch@ piping.georgfischer.com

Authors:

Dipl.-Ing. Bernd Schuster

Georg Fischer Piping Systems Ltd., Schaffhausen (CH)Market Segment Manager CPI

Tel. +41(0)52/631-3553E-mail: Bernd.Schuster@georgfischer.com

Dipl.-Ing. Manfred Schmidt

VAG-Armaturen, Mannheim (G)Manager Product Development

Tel. +49(0)621/749-1451E-mail: M.Schmidt@vag-armaturen.com