02551_en.doc

SECTION 02551

NATURAL GAS DISTRIBUTION

PART 1 - GENERAL

1.1 REFERENCES

The publications listed below form a part of this specification to the extent referenced. The publications are referred to within the text by the basic designation only.

AMERICAN SOCIETY OF MECHANICAL ENGINEERS (ASME)

ASME B31.8

Gas Transmission and Distribution Systems.

ITALIAN NORMS AND CODES

Law No. 46 (5 Mar. 1990) Plant Safety.

Law No. 1083 (6 Dec. 1971) Gas Distribution Safety Norms.

Norm P11724/4134 Gas Distribution.

Ministerial Decree (12 Apr. 1996) Approval of the Fire Prevention Technical Norm for Design, Construction and Operation of Gas Fired Thermal Plants.

D.P.R. No. 412 (26 August 1993) Regulation for Design, Construction, Operation and Maintenance of Thermal Plants in Execution of Law No. 10, Art.4, Paragraph 4, dated 9 January 1991.

D.P.R. No. 447 (6 December 1991) Technical Regulations for the Execution of Law No. 46 dated 5 March 1990, concerning plant safety.

D.P.R. No. 547 (27 April 1955) Safety at Work.

Legislative Decree No. 493 (14 August 1996)Execution of 92/58/CEE

Regulation Concerning Minimum Requirement for Signs.

ITALIAN NATIONAL INSTITUTE FOR THE UNIFICATION OF STANDARDS (UNI) PUBLICATIONS

UNI 5634

(1997)Identification colors for pipes conveying liquid or gaseous fluids.

UNI 7129

(2001) Gas plants for domestic use fed by network distribution. Design, installation and maintenance.

UNI 7615

(1976) High Density Polyethylene Pipes. Test Methods.

UNI 7616

(1976) High density polyethylene fittings for pipes under pressure. Test methods.

UNI 9034

(1997) Gas distribution pipelines with maximum operating pressure < or = 5 bar. Materials and joining systems.

UNI 9165

(1987) Gas distribution networks with maximum working pressures up to 5 bar. Design, construction and testing.

UNI EN 10208-1

(1999) Steel pipes for pipelines for combustible fluids - Technical delivery conditions - Pipes of requirement class A.

UNI EN 10208-2

(1998) Steel pipes for pipelines for combustible fluids - Technical delivery conditions - Pipes of requirement class B.

UNI ISO 4437

(1988)Buried polyethylene (pe) pipes for the supply of gaseous fuels. Metric series. Specification.

1.2 RELATED REQUIREMENTS

Section 15050, entitled "Basic Mechanical Materials and Methods," applies to this section unless otherwise specified.

1.3 SYSTEM DISTRIBUTION

The gas distribution system includes natural gas piping and appurtenances from point of connection with future gas main interior distribution system as indicated on drawings.

1.4 SUBMITTALS

Submit the following.

1.4.1 Product Data

a. Pipe

b. Fittings

c. Valves

d. Pipe identification

1.4.2 Test Reports

a. Pipe pressure test

1.4.2.1 Pipe pressure test

Provide certified copies of piping pressure tests.

1.4.3 Operation and Maintenance Manuals

a. Gas distribution system and equipment operation data.

b. Gas distribution system maintenance.

c.

Gas distribution equipment maintenance.

1.4.3.1 Gas Distribution System and Equipment Operation Data

Include maps showing piping layout, locations of system valves, and gas line markers; step-by-step procedures for system start up, operation and shutdown (index system components and equipment to the system maps); isolation procedures including valve operation to shutdown or isolate each section of the system (index valves to the system maps and provide separate procedures for normal operation and emergency shutdown if required to be different).

1.4.3.2 Gas Distribution System Maintenance Data

Include maintenance procedures and frequency for system and equipment; identification of pipe materials and manufacturer by locations, pipe repair procedures, and jointing procedures at transitions to other piping material or material from a different manufacturer.

1.4.3.3 Gas Distribution Equipment Maintenance Data

Include identification of valves and other equipment by materials, manufacturer, vendor identification and location; maintenance procedures and recommended tool kits for valves and equipment; recommended repair methods (i.e., field repair, factory repair, or replacement) for each valve and piece of equipment; and preventive maintenance procedures, possible failure modes and troubleshooting guide.

1.5 QUALITY ASSURANCE

Materials and equipment shall conform to Law No. 1083, Norm P11724/4134 and Ministerial Decree 12 April 1996 to the extent specified herein, to local utility requirements, and to other requirements specified.

1.6 DELIVERY, STORAGE, AND HANDLING

1.6.1 Delivery and Storage

Inspect materials delivered to the site for damage, and store with a minimum of handling. Store materials on site in enclosures or under protective coverings. Store plastic piping under cover out of direct sunlight. Do not store materials directly on the ground. Keep inside of pipes and fittings free of dirt and debris.

1.6.2 Handling

Handle pipe, fittings, valves, and other accessories in such manner as to ensure delivery to the trench in sound, undamaged condition. Take special care not to damage coatings on pipe and fittings. Repair damaged coatings to original finish.

PART 2 - PRODUCTS

2.1 PIPING MATERIALS FOR GAS SERVICE LINES

2.1.1 HDPE Pipe and Heat Fusion Fittings

Conform to UNI ISO 4437 Series S5. Minimum wall thickness shall be as specified in UNI ISO 4437. HDPE pipe and fittings shall have joints as specified for gas distribution main piping. The pipe size diameter indicated on the drawings shall be the minimum exterior diameter. Pipe shall have minimum pressure rating of 4 bars and shall pass pressure tests conforming to UNI 7615 and UNI 7616. Pipe shall be yellow color, in compliance with the norms.

Acceptable Manufacturers

The following manufacturers generally meet the provisions of these specifications for HDPE plastic piping and fittings:

a. FITT S.P.A.

Via Astico 40

36030 Fara Vicentino (VI)

Tel. 0445/399111

Fax 0445/897593

b. SOCIETA' DEL GRES

ING. SALA S.P.A.

Via Marconi, 1

24010 Petrosino (BG)

Tel. 035/579111

Fax 035/579342

c. ROMANA EDILIT PRIMA S.R.L.

Via Pier Vittorio Aldini, 41

00178 - Roma

Tel. 06/7267.0492/3

d. SIREA

Via Corriera 25

48010 - Ravenna

Tel. 0545/78008

Fax 0545/78790

e. SAMI PLASTIC S.P.A.

Loc. Piego, Fraz. Monterone

52038 Sestino (AR)

Tel. 0575/71711

Fax 0575/772369

2.2 GAS SERVICE LINE VALVES AND ACCESSORIES

2.2.1 Plug Valves

Valves shall be suitable for the foreseeable operating pressure of the pipelines where are shall be installed. Valve body shall be factory tested by the manufacturer with an hydraulic test at a pressure 1.5 times the nominal pressure they are rated. Valves shall be full bore type. Minimum bore size for full bore valves shall be 95 percent of the internal cross sectional area of pipe of the same nominal diameter. Cast iron valves installed on buried HDPE piping shall have mechanical joint. Plug valves shall be lubricated. Lubricating fittings on installed valves shall be accessible for re-lubrication, or extensions shall be provided to make them accessible. Plug valves shall be wrench or gear operated.

2.2.2 On-Off Valve

Valves shall be suitable for the operating pressure of the pipelines where they shall be installed. Valves shall be polyethylene material and shall be S5 Series. Valves shall have the same diameter of the pipes where they will be installed and shall be operable form the top with control wrench.

2.2.3 Exhaust Valves and Unions

Floating ball valve DN 1-1/2” with ends to be butt-welded, and ANSI 150 flanges. Valves shall be operated by hinged metal rod. Valve shall have on the top a steel blank flange in compliance with ANSI 150 R.F. Unions to the polyethylene pipes shall be steel, suitable for natural gas, with smooth ends. Unions shall be coated with exterior polyethylene sheath. The unions shall be connected to the natural gas main with polyethylene coupling sleeves to be electro-welded suitable for natural gas, and with a polyethylene 90 degree bed to electro-welded.

2.2.4 Stainless Steel Cabinet

Provide stainless steel cabinet to house manual shut off valve and gas regulator according to Ministerial Decree dated 12 April 1996. On the cover the words “ GAS” and “METANO” shall be written.

2.3 PIPE IDENTIFICATION FOR ABOVEGROUND PIPING

UNI 5634 for legends and type and size of character. For pipes 20 millimeters and larger, provide printed legends to identify contents of pipes and arrows to show direction of flow. Color code UNI 5634 label backgrounds to signify levels of hazard. Make labels of plastic sheet with pressure-sensitive adhesive suitable for the intended application. For pipes smaller than 20 millimeters provide brass identification tags 40 millimeter in diameter with legends in depressed black-filled characters.

2.4 WARNING TAPE AND BARE COPPER TRACER WIRE

As specified in Section 02315, "Excavation and Fill".

Warning and identification wording shall read "DANGER – GAS, PERICOLO – GAS”. Use permanent code and letter coloring unaffected by moisture and other substances contained in trench backfill material.

PART 3 - EXECUTION

3.1 LOCATION OF GAS LINES

Do not install gas piping in the same trench with other utilities. The minimum horizontal clearance between gas pipe and parallel utility pipe shall be 600 mm, except for the communication and electrical lines; for these lines such distance shall be 1000 millimeters. Do not install gas pipe through catch basins, vaults, manholes or similar underground structures.

3.2 VERIFICATION OF CONDITIONS

3.2.1 Installation

Installation shall conform to UNI 7129 ( 2001), and D.P.R. No. 547 dated 27 April 1955, D.P.R. No. 412 dated 26 August 1993, Law No. 46 dated 5 March 1990, D.P.R. No. 447 dated 6 December 1991 and Legislative Decree No. 493 dated 14 August 1996. Pipe, fittings, valves and accessories will be carefully inspected by the Contracting Officer’s Technical Representative before and after installation and those found defective will be rejected. Pipe and fittings shall be free from fins and burrs. Before being placed in position, clean pipe, fittings, valves, and accessories and maintain in a clean condition.

3.2.2 Pipe Laying and Jointing

Provide proper facilities for lowering sections of pipe into trenches. Cut pipe accurately to measurements established at the site and work into place without springing or forcing. Replace pipe or fittings that do not allow sufficient space for proper installation of jointing material with pipe or fittings of proper dimensions. Grade pipe in straight lines, taking care to avoid the formation of dips and low points. Support pipe at proper elevation and grade, taking care to secure firm and uniform support. Wood support blocking will not be permitted. The full length of each section of pipe and all fittings shall rest solidly on the pipe bed, with recesses excavated to accommodate joints and couplings. Provide anchors and supports where indicated. Make provision for the expansion and contraction of pipe lines as indicated. Keep trenches free of water until joints have been made. Close open ends of pipe temporarily with wood blocks or plastic end closures at the end of each work day. Gas mains shall have a minimum earth cover of 760 mm, except that in rock excavation, minimum earth cover shall be 610 mm. Provide drains in depressed spots as required by UNI 9165. Make buried connection between buried HDPE piping and the steel pipe entering the building.

3.2.3 Warning Tape and Bare Copper Tracer Wire

As specified in Section 02315, "Excavation and Fill".

3.2.4 Special Requirements for Gas Service Piping Installation

Work shall include the connection to the building piping where the building piping has been installed. Where building piping has not been installed, terminate service lines with a temporary cap approximately 1.5 meters from building line as shown on drawings and at a point as directed by the Contracting Officer’s Technical Representative. Installation shall be in accordance with the applicable requirements of UNI EN 10208-1 e UNI EN 10208-2 and Ministerial Decree 12 April 1996. Minimum earth cover for service lines shall be 800 mm as shown on drawings and in compliance with the Aviano Design Guide.

3.2.4.1 Earthwork for Gas Service Piping

Earthwork shall be in accordance with Section 02315 "Excavation and Fill". Employ hand excavation within 1500 mm of existing gas pipelines or other underground structures. HDPE tubing may also be laid by the plow-in technique. The plow-in technique of laying tubing shall be accomplished by approved equipment especially designed for this type of work. The equipment shall have a vibratory plow, feed chute, soft rubber tubing cushion guide, and a tubing reel. The vibratory plow shall be capable of cutting a slit in the ground of width consistent with the size of the tubing and of depth to have the specified depth of cover over the tubing when laid. The unit shall be capable of feeding the tubing and the warning tape into the ground to the specified depth, without kinking. The reel shall be of a diameter appropriate for the tubing and shall operate smoothly. In the event the tubing breaks or kinks, the kink shall be cut out and a joint as herein specified for the material shall be made.

3.2.4.2 Service Connections

Make service connections at the top of the main, whenever the depth of the main is sufficient to allow top connections. When service connections cannot be made at the top of the main, they shall be made on the side of the main as close to the top as possible. Service connections shall not be made lower than the horizontal midpoint of the gas main. Install service connections in accordance with the applicable requirements of ASME B31.8.

3.2.4.3 Gas Service Piping Joints

a.

HDPE Pipe or Tubing: Make joints for HDPE pipe or tubing and fittings in accordance with UNI 9034 and the recommendations of the manufacturer of the pipe or tubing and fittings.

3.2.4.4 Valve Installation on HDPE Service Lines

Restrain curb cocks installed on HDPE service lines so that no turning torque can be transmitted to the pipe. Support curb boxes as indicated.

3.3 FIELD QUALITY CONTROL

Do not bury, cover or conceal joints and fittings until they have been inspected, tested and approved.

3.3.1 Pressure Tests

Use test pressure of 1.5 times maximum working pressure, but in no case less than 600 kPa. Do not test until every joint has set and cooled at least 8 hours at temperatures above 10°C. Test system gas tight in accordance with UNI 7616, UNI 9165. Use clean dry air or inert gas, such as nitrogen or carbon dioxide, for testing. Systems which may be contaminated by gas shall first be purged as specified. Make tests on entire system or on sections that can be isolated by valves. After pressurization, isolate entire piping system from sources of air during test period.

Maintain test pressure for at least 8 hours between times of first and last reading of pressure and temperature. Take first reading at least one hour after test pressure has been applied. Do not take test readings during rapid weather changes. Provide temperature same as actual trench conditions.

There shall be no reduction in the applied test pressure other than that due to a change in ambient temperature. Allow for ambient temperature change in accordance with the relationship PF+100 = (P1 + 100)(T2 + 273)/(T1 + 273), in which "T" and "PF" represent Celsius temperature and gauge pressure, respectively, subscripts "1" and "2" denote initial and final readings, and "PF" is the calculated final pressure. If "PF" exceeds the measured final pressure (final gauge reading) by 3.4 kPa or more, isolate sections of the piping system, retest each section individually, and apply a solution of warm soapy water to joints of each section for which a reduction in pressure occurs after allowing for ambient temperature change. Repair leaking joints and repeat test until no reduction in pressure occurs. In performing tests, use a test gauge calibrated in 6.89 kPa increments and readable to 3.4 kPa.

3.4 PURGING LINES

After completing pressure tests, and before testing a gas contaminated line, purge line with nitrogen at junction with main line to remove all air and gas. Clear completed line by attaching a test pilot fixture at capped stub-in line at building location and let gas flow until test pilot ignites. Procedures shall conform to UNI 9165.

3.5 FINAL CLEAN-UP

Upon completion of the work, remove and dispose of excess spoil and leave the areas in a clean condition. Restore service line trenches as nearly as possible to the original appearance and condition.

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Section 02551

Section 02551