AI ?PA ESection 7.1 ' Piping Underground 115

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that notifies utility companies of excavation work near their underground installations andnotifies them to mark the locations prior to excavation. All underground utilities, includinggas, electncity, telephone, and cable TV companies, are members of Dig Safe. The Dig safeprogram covers gas lines installed by gas transmission companies and by local gas utilitiesto buildings. It does not include gas lines run from a building to another building, such as

a garage, or to an outdoor appliance, such as a gas grill or pool heater. To avoid accidents,excavators should be made aware when underground gas lines exist that were not installedby gas utility companies.

If protective devices are needed, they must be of sufficient strength to protect the pipeand must be made of a material that will not corrode over time. Plastic pipe or pVC is oftenused as a protective material. Split along its length, plastic pipe or PVC provides the necessarystrength and does not corrode underground.

7.1.2.2 Tfenches. The trench shall be graded so that the pipe has a firm, substantiallycontinuous bearing on the bottom of the trench.

7.L.2.3 Backfilling. Where flooding of the trench is done to consolidare the backfill, careshall be exercised to see that the pipe is not floated frorn its firm bearine on the trenchbottom.

7.1.3* Protection Against Corrosion

Gas piping in contact with earth or other material that could corrode the piping shall beprotected against conosion in an approved manner. When dissimiiar metals are joined under-ground, an insulating coupling or fitting shall be used. Piping shall not be laid in contactwith cinders. Uncoated threaded or socket welded joints shall not be used in piping in contactwith soil or where internal or extemal crevice corrosion is known to occur.

4.7.1.3 For information on corrosion protection of underground pipe, see NACE Rp 0169,Control of Extenml Corcosion on (Jnderground or Submerged. Metallic Piping Systems.Information on installation, maintenance, and corrosion protection might be available fromthe gas supplier.

With the availability of polyethylene and othercorrosion-resistant piping systems (e.g., plastic-coated metal pipe and tubing and copper tubing where corrosion is not likely to occur), the needto provide corrosion protection for steel as required by 7 .1.3 often makes steel pipe the lastchoice for underground installation. Steel pipe that is instailed underground or in contactwith water deteriorates through galvanic corrosion, which is an electrochemical process.

With polyethylene and other corrosion-resistant piping systems, this electrochemicalprocess can be prevented by stopping the flow of electricity between the pipe and the soil.Stopping electricity flow is accomplished by coating the pipe with an electrically insulatingmatedal. Factory-applied coatings include polyethylene over a mastic primer and fusion-bonded epoxy' Field-applied coatings usually consist of either hot- or cold-applied tapes overa complementary primer.

- The second step in properly protecting a steel pipe underground is to maintain anelectrical charge on the pipe, relative to the surrounding soil, that is adequate to ensure thatthe corrosion-causing transfer of electrons will not occur. Maintaining this electrical chargeis called catlxodic protection and, is accomplished by an impressed voliage supplied by eithera passive sacrificial anode system or an active rectifier system. Sizing and spacing of eitherthe anodes or the rectifiers are important. Manufacturers of these components are a goodsource of guidance.

Partial steel pipe corrosion solutions, such as coating the pipe but not using cathodicprotection, usually fare worse than unprotected pipe. Uncoated pipe will corrode over itsentire surface area, whereas corrosion of coated pipe lacking cathoaic protection will beconcentrated at any pinhole or other imperfection (called a "holiday") in the coating. Because

National Fue! Gas Code Handbook 2006

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< FAQWhy is cathodic protection highlyrecommended in undergroundsteel pipe installations?

116 Chapter 7 . Gas Piping lnstallation NP?A @obtaining and maintaining a perfect coating application is virfually impossible, protecticinunderground steel pipe should include cathodic protection. Any cathodically protected ptshould be electrically isolated from upsffeam and downstrean components to preventloss of the required electrical charge. This isolation is accomplished with the use of diunions or flange-insulating kits.

In reality, it is not practical to protect short runs of buried steel pipe usingprotection, which is the reason that alternate materials are used.

The requirement forprotection against corrosion also recognizes that threadeA and welde&;steel pipe joints are especially prone to the effects of corrosion and should not be used where .

corrosion is anticipated. Similarly, the use of cinders as backfill is prohibited because thg1giaccelerate corrosion. .j..

, r.tillil 4.7.1,.4 The gas supplier can be consulted for recommendations. ,,,,i,1ZII 'i,};r:li

Ice problems are all but nonexistent with pipeline natural gas and propane, but they can-$I!E:exist in gas from alternative sources such as local wells, landfills, or waste treafinent plantsiThe user is to consult the gas supplier about the possibility of ice, which can block lines:iand prevent gas flow.

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@ 7.1.5 Piping Through Foundation Wall -.a

Underground piping, where installed through the outer foundation or basement wall of 6building, shall be encased in a protective pipe. The space between the gas piping and thebuilding shall be sealed to prevent entry of gas or water.

Subsection 7.1.5 is included in the code because gas leaks in outdoor underground pipingcan migrate along the buried piping and into the basement instead of venting to the atmosphereabove grade. This condition can be extremely hazardous. The requirement to seal the casingagainst water entry is intended to block this leakage path. See Exhibit 7.2 for an illustrationof a below-grade foundation wall penetration.

Caulking should not be used as a foundation wall seal where the gap is larger than thatrecommended by the caulking manufactrirer. Pipe can move reiative to the foundation, andthe caulking can fail if it is sealing a large gap.

The use of an inert wrapping material provides an additional method of protection. Thematerial must be approved and be suitable for the application. The material must also beable to seal around the pipe and the wall to prevent the entry of gas or water.

7.L.6 Piping Underground Beneath Buildings

Where the installation of gas piping underground beneath buildings is unavoidable, the pipingshall be encased in an approved conduit designed to withstand the superimposed loads andinstalled in accordance with 7.1.6.1 or 7.7.6.2.

Subsection 7.1.6 was revised in the 2006 edition to allow the installation of pipe urider,dq-',

building that originates and terminates inside a building. Previously, only pipe that orioutside a building was allowed. This change resulted from a representative of a gascompany who identified a need for this type of installation in some buildings. This typeinstallation presents no greater potential hazard than what was previously allowed.

Gas leaking from a pipe installed underneath a building can migrate into the buiThe code requires that any such pipes be cased and that the annular space between theand the case be vented to the outdoors. (See Exhibit 7.3.)The AHJ may require that

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:lI2006 National Fuel Gas Code

I.,IFPA @ Section 7.1 . Piping Underground 1'17

Ends of sleeve sealed to gas line

EXHIBIT 7.2 Piping Through a Foundation Wall. (Couftesyof J. J. Drechsler)

EXH|B|T 7.3 Venteci Sleerze.

sleeve be tested in the same manner as the gas pipe it contains. Although the resultinginstallation is pertectly safe, the installation is difficult and the repairs are more so. For these'reasons, practicality demands that most pipes run though buildings rather than under them.

i :. 7.1.6.L Conduit with One End Terminating Outdoors. The conduit shall extend into an

. - accessible portion of the building and, at the point where the conduit terminates in the. :.-'- i building, the space between the conduit and the gas piping shall be sealed to prevent the

:,p.gssible entrance of any gas leakage. Where the end sealing is of a type that will retain

Sq t"U pressure of the pipe, the conduit shall be designed for the same pressure as the pipe.ionduit shall extend at least 4 in. (100 mm) outside the building, be vented outdoors

grade, and be installed so as to prevent the entrance of water and insects.

requirement is not new. It has been in the code for many editions.

Conduit with Both Ends Terminating Indoors. Where the conduit originates andwithin the same building, the conduit shall originate and terminate in an accessible

of the buildins and shall not be sealed.

'new option recognizes the need to supply fuel gas to appliances located in the centerfloor room, without piping dropping from the ceiling. The most common use ismnges in kitchens. Where the gas meter or pressure regulator is located outside

T*tg, previously the only way to pipe gas under the slab was to route a branch linethe building and then back under the slab. The new option ailows shorter pipe runs

and eliminates the need for a vent, for which no sizing information is provided

?.1.7 covers the installation of plastic pipe and begins by clearly stating that'to be used outdoors, underground only, and 12 or 18 in. (300 or 460 mm)

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Code Handbook 2006

118 Chapter 7 . Gas Piping Installation

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EXHIBIT 7.4Inc.)

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Transition Fitting. (Courtesy of Ray Murray, EXHIBIT 7.5 Anode-Type Fiser Instailatioi.

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. . ,lt,,'.below finished grade. Plastic pipe may not be,use,d inside buildings for fuel g^. fVo," ,niiin new construction randscaping *uy "hung"

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: .:,::Risers and warl head adapters (also callled.srrrr* lrrii oioptrolare also

"ou.r"u*this subsection. These fittings are used to install polyethylene pii" ""0

ftrbing beyond thegas meter. For more than 30 years, polyethylene has been ur"a ,u"..rrruly in gas distributionservice upstream of the gas meter.Plastic pipe and tubing, is more susceptible to inadvertent damage during installationthan most metallic pipe' For this reason, special attention should be giuer'to proper compactionbelow the pipe, to the elimiaation of shear points on connections during backfilling, and tothe materials in the backfill, making

"ertuin that angular and large materials are not usednear the pipe.

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t connection of Plastic Piping. Plastic pipe shatl be instatied ourdoors, underground

11.;:r""""1,1:,:,::-l{1.":ir.::,""g.transition fiuings with anodes (Exhibir 7.4 and.Exhibit 7.5)

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* ,,,Exception I,{o. l:riser is used.

Plastic pipe shall be permittecrto terminate aboveground where an anoderess

EXHIBIT 7.6 ServicelWallHead Adapters (Cutaway).(Couftesy of R. W. Lyall &Company, lnc.)

Anodeless risers are-constructed with the piastic pipe mnning inside steel all the way to thetop end, where the pressure seal and the iransition t om ptaitic ,"1i."1 are located. Theserisers are accepted by the code because their design addresses the concerns regarding plasticpipe terminating aboveground.

Exception No' 2: Plastic pipe shall be permitted to terminate with a yvall head adapteraboveground in buildings, incruding basements, where the prarti, prp, )s insertecl in a pipingmaterial permitted for use in buildings.

Exception No' 2 permits plastic gas piping to be terminated aboveground and outside ofbuildings' This exception permits the uie of fittings, known as wall heai adapters, to terminateburied plastic pipe inside of builclings in basement areas. wall head adapters (Exhibit 7.6)often are used by utilities fbr insertitn renewals of steel service lines. within the scope of

20OG National Fuel Gas Code Handbook

5P Gc /f oe404.7 Above-ground outdoor piping. All piping installedoutdoors shall be elevated not less than 3tlt inches (152 mm)above ground and where installed across roof surfaces, shall beelevated not less than3l/rinches (152 mm) above the roof sur-face. Piping installed above ground, outdoors, and installedacross the surface ofroofs shall be securely supported and lo-cated where it will be protected from physical damage. Wherepassing through an outside wall, the piping shall also be pro-tected against corrosion by coating or wrapping with an inerlmaterial. Where piping is encased in a protective pipe sleeve,the annular space between the piping and the sleeve shall be

sealed.

404.8 Protection against corrosion. Metallic pipe or tubingexposed to corrosive action, such as soil condition or moisture,shall be protected in an approved manner. Zinc coatings (galva-nizing) shall not be deemed adequate protection for gas pipingunderground. Ferrous metal exposed in exterior locations shallbe protected from corrosion iu a manner satisfactory to thecode official. Where dissinilar metals are joined underground,an insulating coupling or fitting shall be used. Piping shall notbe laid in contact with cinders.

404.8.1 Prohibited use. Uncoated threaded or socketwelded joints shall not be used in piping in contact with soilor where internal or external crevice corrosion is known tooccur.

404.8.2 Protective coatings and wrapping. Pipe protec-tive coatings and wrappings shall be approved for the appli-cation and shall be factory applied.

Exception: Where installed in accordance with the man-ufacturer's installation instructions, field application ofcoatings and wrappings shall be permitted for pipe nip-ples, fittings and locations where the factory coating orwrapping has been damaged or necessarily removed atjoints.

404.9 Minimum burial depth. Underground piping systemsshall be installed a minimum depth of 12 inches (305 mm) be-low grade, except as provided for in Section 404.9.I.

404.9.1 Individual outside appliances. Individual lines tooutside lights, grills or other appliances shall be installed a

minimum of 8 inches (203 mm) below finished grade, pro-vided that such installation is approved and is installed in lo-cations not susceptible to physical damage.

404.10 Tienches. The trench shall be graded so thatthe pipehas a fum, substantially continuous bearing on the bottom ofthe trench.

4O4.lL Piping underground beneath buildings. Piping in-stalled underground beneath buildings is prohibited exceptwhere the piping is encased in a conduit of wrought iron, plasticpipe, or steel pipe designed to withstand the superimposedloads. Such conduit shall extend into an occupiable portion ofthe building and, at the point where the conduit terminates inthe building, the space between the conduit and the gas pipingshall be sealed to prevent the possible entrance of any gas leak-age. Where the end sealing is capable of withstanding the fuIlpressure of the gas pipe, the conduit shal be designed for thesame pressure as the pipe. Such conduit shall extend not less

- -than 4 inehes-(102 rnm)outside theSuilding' shall be vented

2006 INTERNATIONAL FUEL GAS CODE@

GAS PIPING INSTALLATIONS

above grade to the outdoors, and shall be installed so as to,prevent the entrance of water and insects. The conduit shall be

protected from corrosion in accordance with Section 404.8.

404.l2Outlet closures. Gas outlets that do not connect to ap-fpliances shall be capped gas tight.

Exception: Listed and labeled flush-mounted-fype quick-disconnect devices and listed and labeled gas convenienceoutlets shall be installed in accordance with the manufac-turer's installation instructions.

404.13 Location of outlets. The unthreaded portion of pipingoutlets shall extend not less than I inch (25 mrn) through frn-ished ceilings and walls and where extending through floors oroutdoor patios and slabs, shall not be less than 2 inches (51

mm) above them. The outlet fitting or piping shall be securelysupported. Outlets shall not be placed behind doors. Outletsshall be located in the room or space where the appliance is in-stalled.

Exception: Listed and labeled flush-moutrted-type quick-disconnect devices and listed and labeled gas conveuienceoutlets shall be installed in accordance with the matrufac-turer's inslallation inslructiorts.

404.14 Plastic pipe. The installation of plastic pipe shall com-ply with Sections 404.14.1through 404.14.3.

404.14.1Limitations. Plastic pipe shall be installed outsideunderground only. Plastic pipe shall not be used within orunder any building or slab or be operated at pressures

greater than 100 psig (689 kPa) for natural gas or 30 psig(207 kPa) for LP-gas.

Exceptions:

1. Plastic pipe shall be permitted to terminate aboveground outside of buildings where installed inpremanufactured anodeless risers or service headadapter risers that are installed in accordance withthe manufacfurer' s installation instructions'

2. Plastic pipe shall be permitted to terminate with a

wall head adapter within buildings where the plas-

tic pipe is inserted in a piping material for fuel gas

use in buildi:rgs.

404.14.2 Connections. Connections made outside and un-

derground between metallic and plastic piping shall be

made only with transition fittings categorized as Category Iin accordance with ASTM D 2513.

404.L4.3 Thacer. A yellow insulated copper tracer wire orother approved conductor shall be installed adjacent to un-

derground nonmetallic piping. Access shall be provided tothe tracer wire or the tracer wire shall terminate aboveground at each end of the nonmetallic piping. The tracer

wire size shall not be less than 18 AWG and the insulationtype shall be suitable for direct burial.

404.15 Prohibited devices. A device shall not be placed insidethe piping or fittings that will reduce the cross-sectional area orotherwise obstruct the free flow of gas.

Exception: Approved gas filters.

404.16 Testing of piping. Before any system of piping is put inservice or concealed. it shall be tested to ensure that it is gas

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