9.7 Natural Gas Piping
All Natural Gas Piping installations shall be designed and specified per the following requirements:
A. Material for Natural Gas Piping (above ground and underground) shall be ASTM A 53, Grade B, Schedule 40, Type E or S.
1. Protective Coating for Underground Piping: Factory-applied, three-layer coating of epoxy, adhesive, and polyethylene (PE).
B. Material for Underground Natural Gas Piping shall be PE Pipe, ASTM D 2513, SDR 11.
1. PE Fittings: ASTM D 2683, socket-fusion type or ASTM D 3261, butt-fusion type with dimensions matching PE pipe.
2. PE Transition Fittings: Factory-fabricated fittings with PE pipe complying with ASTM D 2513, SDR 11; and steel pipe complying with ASTM A 53/A 53M, black steel, Schedule 40, Type E or S, Grade B.
C. Natural Gas Piping shall be constructed with threaded joints for gas pressure 5.0 PSIG or less.
D. Natural Gas Piping shall be constructed with welded joints for gas pressure higher than 5.0 PSIG.
E. Corrosion protection shall be provided for gas pipes installed underground, encased in concrete, and in wet or corrosive environments.
F. Exposed gas pipes subject to damage shall be protected. All installations shall follow NFPA 54, ANSI Z 223.1, Current Edition. Piping installed aboveground shall be securely supported from physical damage by vehicles or hand trucks, dollies, platform trucks, etc. Provide shields, bollards or pipe sleeve to protect exposed gas pipes as required.
G. Exposed natural gas piping shall be protected against mechanical damage in accordance with requirements of NFPA 54-7.2.
H. Comply with NFPA 54 and the International Fuel Gas Code for design, installation and purging of natural-gas piping.
I. Outdoor Natural Gas Piping Installations
1. All underground natural-gas piping installations must be buried at least 36 inches below finished grade. If natural gas piping must be installed less than 36 inches below finished grade, it must be installed in an appropriate containment conduit
2. Trench Backfill
a. The gas pipe shall be placed in the trench on top of a minimum of 6 inches of aggregate bedding material, which also extends to 4 inches above the top of pipe and compacted. If the gas pipe is to be installed in an area with new bituminous or concrete pavement, then the aggregate bedding material shall be extended above new gas to the bottom of proposed subbase material. Compaction of earth or aggregate material in pipe trench shall only be accomplished by using hand mechanical tampers until the backfill material has been placed a minimum of 2 feet above the gas pipe.
J. Indoor Natural Gas Piping Installations
1. Above Ceiling Installations: Natural-gas piping, fittings, valves, and regulators may be installed in accessible concealed ceiling spaces. Natural gas piping in concealed ceiling spaces does not require containment conduit. Provide proper access in locations where appropriate for maintenance and shut offs. Natural gas pipes must be identified utilizing permanent labels as required by code.
2. In-Floor Installations: Natural-gas piping may be installed in cast-in-place concrete interior floors with a minimum of 1½ inches of concrete cover. Natural gas piping installed in interior floors must have welded joints and protective coating. All in-floor natural-gas piping installations must be in containment conduits constructed of steel pipe with welded joints. A vent pipe must be provided from containment conduit to outdoors and terminated with weatherproof vent cap cover. Gas pipes shall not be in physical contact with other metallic structures such as reinforcing rods or electrically neutral conductors. Do not embed piping in concrete slabs containing quick-set additives or cinder aggregate. Provide proper access in locations where appropriate for maintenance and shut offs.
3. In-Floor Channels: Natural-gas piping may be installed in floor channels where appropriate and not in public view. Channels must have cover and be open to space above for ventilation.
K. Prohibited Locations:
1. Natural gas pipes shall not be installed in or through circulating air ducts, clothes or trash chutes, chimneys, or gas vents (flues), ventilating ducts, or dumbwaiter or elevator shafts.
2. Natural gas pipes shall not be installed in solid walls or partitions.
3. Natural gas pipes shall not be installed on roofs of any building except branch pipes to roof mounted HVAC equipment. Branch Pipes shall be mounted on pipe stands.
4. Natural gas pipes shall not be installed on the exterior fascia of any building except where it may need to enter buildings or branch pipes to exterior equipment.
5. Natural gas pipes shall not be installed in Electrical and Communication Rooms.
L. LABELING AND IDENTIFYING
1. Underground gas pipes:
a. Detectable Warning Tape: Acid- and alkali-resistant, PE film warning tape manufactured for marking and identifying underground utilities, a minimum of 6 inches (150 mm) wide and 4 mils (0.1 mm) thick, continuously inscribed with a description of utility, with metallic core encased in a protective jacket for corrosion protection, detectable b metal detector when tape is buried up to 30 inches (750) deep; colored yellow.
2. Aboveground Pipe Labels:
a. Preprinted, color-coded, with lettering indicating service, and showing flow direction.
b. Spaced at maximum intervals of 25 feet along each run, and 2 feet on either side of wall penetrations.
M. VALVE TAGS
1. Install ceiling tags for above ceiling mounted valves, ceiling tags shall be provided for all kinds of ceilings including suspended ceilings.
9.7.1 Metering of Gas
Gas meter shall be provided by each tenant. These meters must be compatible with MDOT MAA Power Monitoring System (Square-D Power Logic System). With prior coordination with MDOT MAA Utilities, RS 485 communication cable with one spare cable in one-inch conduit shall be extended from the meter to the nearest MDOT MAA Power Logic metering panel.
The gas meter shall be compatible with MOD BUS RTU – RS 485 protocol or MOD BUS RTU – TCP/IP protocol. The output gas reading displayed in Power Logic should be in units of Standard Cubic Feet per Minute (SCFM). Information for conversion from pulse rate to SCFM should be provided with meter specifications. Gas meter and any accompanying devices needing power should be compatible with power available on site.