The pipeline safety regulations refer to NFPA 58 for materials and equipment used in propane gas systems. Where the subject is not covered in NFPA 58, 49 CFR Part 192 is used. In the event of a conflict between 49 CFR Part 192 and NFPA 58, NFPA 58 shall prevail.
It is important for an operator to know the piping materials and propane storage tank sizes for all systems. The operator should develop, or have the system installer or consultant develop, a list of qualified materials for construction and repair of the system. This can be accomplished by referring to NFPA 58 and referencing equipment manufacturers’ installation manuals.
When purchasing materials for use in a propane pipeline system, it is important to be sure that all materials conform with NFPA 58, and are recommended by the manufacturer for propane service. Of course, a propane pipeline system consists of storage tanks, valves, pressure regulators, pipe, fittings and meters.
NFPA 58 permits only pressure vessels built in accordance with:
NFPA 58 does not contain the specific requirements for these pressure vessels.
ASME tanks do not have to be retested or inspected after they are placed into service. Prior to the installation of a previously used container, it may be prudent to have the container inspected to assure that there is no corrosion or damage that could impair the integrity of the container. Welding repairs to ASME tanks can be made only by repair personnel who have been certified under the ASME Code and have been issued an “R” stamp. Repairs must be stamped with the “R” stamp and the work documented.
DOT cylinders are designed for transportation, so their weight is an important consideration. They use thinner walls than ASME tanks and must be periodically recertified and so marked. All DOT cylinders have one or more dates stamped on the cylinder, usually on the collar that protects the cylinder valve from damage. Cylinders cannot be filled if the date on the cylinder has passed. A filled cylinder can be used at any time after the date has expired.
The largest DOT cylinder for propane service has a water capacity of 1,000 pounds, about 420 pounds of propane. Cylinders are usually found only in smaller systems.
"[image showing "propane cylinder" available on page III-2 of the PDF linked at the right]"
NFPA 58 provides a list of pipe and tubing materials and fittings that can be used in propane systems. Be sure to check the latest edition of NFPA 58 referenced in 49 CFR Part 192 for any materials that may have been added or deleted.
Pipe meeting the following specifications can be used:
Wrought-iron pipe, ANSI B36.10M, Welded and Seamless Wrought Steel Pipe.
Steel pipe, ASTM A53, Specification for Pipe, Steel, Black and Hot-Dipped,
Zinc-Coated Welded and Seamless.
Steel pipe
ASTM A106, Specification for Seamless Carbon Steel Pipe for High-Temperature Service.
Brass pipe
ASTM B43, Specification for Seamless Red Brass Pipe, Standard Sizes.
Copper pipe
ASTM B42, Specification for Seamless Copper Pipe, Standard Sizes.
Polyethylene pipe
ASTM D2513, Specification for Thermoplastic Gas Pressure Pipe, Tubing and Fittings.
Note that pipe must be recommended by the manufacturer for use with LP gas. Polyethylene pipe must be marked in compliance with the product marking requirements of ASTM D2513, and must include:
Tubing meeting the following specifications can be used:
Steel tubing, ASTM A539, Specification for Electric-Resistance-Welded Coiled
Steel Tubing for Gas Fuel Oil Lines. Brass tubing ASTM B135, Specification for Seamless Brass Tube. Copper tubing ASTM B88, Type K or L, Specification for Seamless Copper
Water Tube. ASTM B280, Specification for Seamless Copper Tube for Air Conditioning and Refrigeration Field Service.
Polyethylene tubing ASTM D2513, Specification for Thermoplastic Gas Pressure Pipe, Tubing and Fittings.
Fittings used with Metallic Pipe - Fittings in metallic pipe and tubing must be steel, brass, copper, malleable iron, ductile (nodular) iron or plastic. No cast iron can be used. Pipe joints in wrought iron, steel, brass or copper pipe can only be flanged, threaded, welded or brazed. Brazed fittings must be made using a brazing filler material and must have a melting point exceeding 1,000º F. (All commercially available brazes meet this requirement.) This eliminates solder as a tubing joining material. When a flange is opened, the gasket must be replaced.
Joining Polyethylene Pipe and Tubing - Joints in polyethylene pipe and tubing must be made using the following procedures:
ASTM D2683, Specification for Socket-type Polyethylene (PE) Fittings for Outside Diameter Controlled Polyethylene Pipe; or ASTM D3261, Specification for Butt Heat Fusion Polyethylene (PE) Plastic Pipe andTubing; or ASTM F1055, Specification for Electrofusion Type Polyethylene Fittings for Outside Diameter Controlled Polyethylene Pipe and Tubing,
"[image showing "compress type mechanical fittings" available on page III-4 of the PDF linked at the right]"
Must comply with Category 1 of ASTM D2513 for mechanical joints and be tested and shown to be acceptable for use with polyethylene pipe and polyethylene tubing and meeting additional requirements in NFPA 58.
"[image showing "Factory assembled transition fittings" available on page III-4 of the PDF linked at the right]"
All fittings used to join polyethylene pipe or polyethylene tubing shall be tested and recommended by the manufacturer for use with polyethylene (PE) pipe and shall be installed according to the manufacturer’s written procedure.
"[image showing "Factory assembled transition fittings" available on page III-4 of the PDF linked at the right]"
Factory-assembled anodeless risers must be recommended for LP-Gas by the manufacturer. Field-assembled anodeless risers are design certified to meet the requirements of Category 1 of ASTM D2513 and the requirements of NFPA 58.
Anodeless risers are used to make the transition between underground PE pipe or tubing and metal pipe aboveground. As PE must be installed below ground, risers are commonly used to connect the underground PE to aboveground piping materials. Anodeless risers are available as factory assembled units and field assembled kits. Anodeless risers are made from PE pipe inside a protective metal sheath, usually schedule 40 steel pipe. The metal is protected from corrosion by a factory applied coating, and a separate anode is not required, hence the name, “anodeless”. Factory assembled risers usually have a 90 degree bend at the PE connection end and come in several lengths depending on the depth of burial of the PE pipe or tubing.
"[image showing "Polyethylene pipe cannot be joined by a threaded or miter joint" available on page III-6 of the PDF linked at the right]"
Polyethylene pipe cannot be joined by a threaded or miter joint.
Installation - All PE fittings must be installed in accordance with the fitting manufactures’ instructions by persons trained in the applicable joining procedure. The training must be documented.
Fittings for polyethylene pipe and tubing must be fabricated from materials listed in ASTM D2513, Specification for Thermoplastic Gas Pressure Pipe, Tubing and Fittings and must be recommended for LP gas use by the manufacturer.
Operating Pressure Fitting design pressure
Higher than container pressure 350 psig, min
Liquid propane or vapor over 125 psig 250 psig
Propane vapor less than 125 psig 125 psig
All valves used in metallic piping systems must have pressure containing parts of steel, ductile (nodular) iron, malleable iron or brass. All materials used, including valve seat discs, packing, seals and diaphragms, must be resistant to the action of LP gas under service conditions. Many valves are listed by independent testing laboratories for use in LP gas service. These can be used as recommended by the manufacturer. Other valves can be used, but must comply with the requirements of NFPA 58 and should be recommended by the manufacturer for LP gas service to be sure that all the component parts of the valve are approved for LP gas service.
"[image showing "Orange valve" available on page III-7 of the PDF linked at the right]"
Valves used with polyethylene pipe and tubing must meet the requirements of ASTM D2513 and be so marked.
"[image showing "Valves used with polyethylene pipe" available on page III-7 of the PDF linked at the right]"
The requirements for two-stage pressure regulators in NFPA 58 incorporate overpressure protection. No additional equipment for overpressure protection is needed when residential systems complying with NFPA 58 are installed. Overpressure protection is accomplished by reference to the requirements of UL 144, Pressure Regulating Valve for LP-Gas, which requires integral pressure relief to limit the outlet pressure of the second stage regulator to 2 psig or less in the event of failure of either the first or second stage pressure regulator under failure conditions.
All first stage propane pressure regulators up to a capacity of 500,000 BTU/hr are designed to deliver a maximum of 10 psig to the second stage regulators. This type of regulator incorporates a pressure relief valve which is operated by over-travel of the diaphragm stem. This pressure relief feature actuates when the diaphragm has traveled as far as it can in an effort to maintain the desired 10 psig outlet pressure. Integral pressure relief is required on all first stage regulators of this size. Regulators larger than 500,000 BTU/hr either incorporate integral overpressure protection or can use a separate external pressure relief valve. When specifying regulators larger than 500,000 BTU/hr it is important to specify an integral or separate overpressure protection device. The overpressure protection device can be a pressure relief valve, a second regulator in series (monitor regulator) or an automatic shutdown device. Regulators incorporating an integral pressure regulator are available up to 2,500,000 BTU/hr. Larger regulators use separate pressure relief valves which must be sized to insure that the rated inlet pressure of the second stage regulator is not exceeded. Regulator manufacturers can provide assistance in sizing larger systems.
"[image showing "Examples of regulators" available on page III-8 of the PDF linked at the right]"
The second stage pressure regulator, located near each gas user in the system, is designed to reduce the 10 psig propane pressure to 11 inches of water column. This regulator incorporates a full capacity relief valve similar in design to the relief valve in the first stage which will limit the downstream pressure to less than 2 psig in the event of an emergency situation.
The limit of 2 psig was selected to correspond to requirements for appliance pressure controls. The standards for appliance pressure controls have been revised to test for overpressure of up to 2 psig with no leakage out of the appliance control. The control is not required to properly operate following an overpressure of 2 psig, but must not leak gas into the building.
"[image showing "External pressure regulator" available on page III-9 of the PDF linked at the right]"
It must be remembered that this means of accomplishing overpressure protection operates by releasing propane to the atmosphere instead of inside a building in the event of a failure. Operators of small propane systems may elect to advise their customers of the need to report any releases of propane which will be identified by an obvious hissing noise coming from either regulator.
NFPA 58 and UL 144 were revised in the 1995 edition to incorporate this overprotection system. The final date to produce regulators under the previous edition of UL 144 was June 1, 1998. Most manufacturers have revised their regulators to meet the new requirements in 1995. If in doubt, specify that all regulators meet the latest edition of UL 144.
This chapter is designed to help the LP gas operator meet the construction and repair requirements set by the pipeline safety regulations. It outlines construction, pipe handling and pressure testing requirements for installation of a safe system. It explains the procedures to qualify a person to make a pipe joint. It gives directions for finding "qualified persons" to do construction and repair work on a gas system. Remember, it is always the operator’s responsibility to see that a contractor follows all requirements.
Manufacturers of pipe, valves, fittings and other gas system components must design and test them to mandatory industry specifications. The specifications are incorporated in NFPA 58 by reference into 49 CFR Part 192, the gas pipeline safety regulations. Components meeting the requirements are qualified for gas service and are marked with the "approved" markings (See Chapter III). In addition, manufacturers usually develop procedures for joining their products and joining other materials to their products. Manufacturers’ product manuals provide procedures for installation and operation that should be incorporated in the operator’s operations and maintenance plans.
It is essential that an LP gas operator knows the types of material and various elements of the gas piping system. A piping system consists of pipe, tanks, valves, fittings, regulators, relief devices and meters. The operator must select components for the system that meet all applicable standards and that comply with the pipeline safety regulations. For example, to develop a cathodic protection program, it is necessary to know the type of metal piping in the system.
Records of the types and locations of system components are critical for planning purposes. Operators who are uncertain of the type of material in their gas piping system must identify the materials. This may be done in one of the following ways:
Operators unfamiliar with the types of materials must rely on a qualified person to identify the components. These investigations may require the operator to engage a consultant if adequate in-house expertise is lacking.
Gas lines must be installed with at least 18 inches of cover. This can be reduced to 12 inches where damage to the pipe is not likely. If the minimum buried depth cannot be met, the pipe must be installed in conduit or bridged (shielded).
Installation of gas pipes must be conducted by qualified personnel. Local gas utilities and local gas associations may be able to recommend qualified persons/contractors who have the necessary background for gas pipe installation. However, contractor work must be supervised carefully. The following sections list the minimum requirements for joining and construction activities.
All the conditions listed below must be met when installing metallic pipe:
If welding steel is necessary in a pipeline, review NFPA 58 which requires that welding must be performed in accordance with ASME Section IX of the Boiler and Pressure Vessel Code. Welders must be qualified in accordance with ASME IX. Some states have special welding certification programs.
Welding of steel pipe is difficult. Both the procedures and the personnel must be qualified for the type of weld performed. If welding is done on a gas system, qualified welders can be referred by:
Plastic pipe is commonly used for distribution mains and services by the gas industry. Polyethylene pipe is the only plastic pipe that can be used for LP gas piping . PE plastic pipe must be manufactured according to standard ASTM D2513 and marked with that number.
Plastic pipe is not permitted for aboveground installation. Plastic pipe must be buried or inserted. The operator must include written joining procedures in the operations and maintenance plan. Each joint must be made in accordance with written procedures that have been proven by test or experience to produce strong gas tight joints. Plastic pipe joining procedures can be obtained from qualified manufacturers. Do not purchase a product if it is not certified by the manufacturer or supplier for qualified joining procedures.
If a contractor installs PE plastic pipe, the operator is still responsible to ensure that only PE pipe manufactured according to ASTM D2513 is installed. In addition, the operator must verify that the contractor follows written joining procedures which meet the manufacturers' recommended joining procedures for each type of pipe and fitting used.
According to the pipeline safety regulations, a person making and inspecting joints must be qualified. No person may make a plastic pipe joint unless that person has been qualified under the applicable joining procedure by making a specimen joint from pipe sections joined according to the procedure that passes inspection and test.
The specimen joint must be visually examined during and after joining and found to have the same appearance as a joint or photograph of a joint that is acceptable under the procedure. In the case of heat fusion, the specimen must be cut into at least three longitudinal straps, each of which is:
A person must be re-qualified under an applicable procedure, if during any 12-month period that person:
[Figure IV-1. Permasert system instructions is available on page IV-4 of the PDF linked on the right]
These are two types of fusion joints.
Butt fusion joint
Uniform double melt bead rolled
Saddle fusion joint
"[image showing "Types of joints" available on page IV-5 of the PDF linked at the right]"
"[image showing "Good melt pattern around pipe" available on page IV-5 of the PDF linked at the right]"
"[image showing "Yellow pipe with labeling" available on page IV-5 of the PDF linked at the right]"
[Figure IV-4. An example of a socket fused joint with polyethylene pipe listed in ASTM D2513 is available on page of the PDF linked on the right]
"[image showing "Image of yellow pipe in ground with vice grips" available on page IV-6 of the PDF linked at the right]"
"[image showing "Butt fusion of pipe" available on page IV-6 of the PDF linked at the right]"
"[image showing "Sidewall fusion" available on page IV-7 of the PDF linked at the right]"
1. Install plastic pipe manufactured under the ASTM D2513 specification. The pipe must have ASTM D2513 marked on it.
[Figure IV-8. a properly marked PE pipe is available on page IV-10 of the PDF linked on the right]
This is a properly marked PE pipe. ASTM D2513 is clearly marked on the pipe. If ASTM D2513 is not marked on a pipe, do not purchase it.
[Figure IV-9. An example of pipe not qualified for gas piping is available on page IV-12 of the PDF linked on the right]
An example of pipe not qualified for gas piping. This is PVC pipe. It was manufactured according to ASTM D2241. The pipe is qualified for use as water pipe, not gas piping. Remember to look for the ASTM D2513 marking on the pipe.
This is an example of an illegal installation which does not meet federal safety regulations. This is a picture of PVC plastic pipe installed aboveground. Remember: BURY PLASTIC PIPE!
"[image showing "an illegal installation which does not meet federal safety regulations" available on page IV-12 of the PDF linked at the right]"
"[image showing "another improper installation" available on page IV-13 of the PDF linked at the right]"
An example of metallic wire used to help locate buried plastic pipe. Pipe locators can detect metal but not plastic. Therefore, metallic wire must be buried along with the plastic pipe. A pipe locator can then detect the buried metallic wire and the adjacent plastic pipe.
"[image showing "An example of metallic wire used to help locate buried plastic pipe" available on page IV-14 of the PDF linked at the right]"
13. After installation, ensure that adequate and appropriate maps and records are retained.
Replacement of gas lines and repair of leaks are highly specialized and potentially hazardous operations. They should be attempted only by persons with adequate LP gas pipeline qualifications.
Leaks in service lines or mains may be repaired by cutting out a short length of pipe containing the leak and replacing it with a new segment of pipe. The pipe segment is commonly attached to the existing line with mechanical couplings, welds, PE fusion, etc. at each end. NFPA 58 requires, if PE pipe is used to replace a section of steel pipe, a tracer wire should be installed to connect the steel pipe ends in order to maintain continuity. Remember that written procedures are required to be followed for each joint. The procedures can be obtained from the manufacturer of the mechanical coupling. If the operator intends to make the repair with a mechanical coupling, then the written procedures must be incorporated into the operations and maintenance plan.
Small leaks in steel service lines or mains, such as those resulting from corrosion pitting, must be repaired with an appropriate leak clamp applied directly over the leak, by replacing a section of pipe or by another acceptable engineering method that can restore the serviceability of the pipe. All steel pipe and fittings installed below ground must be properly coated and cathodically protected before backfilling.
If several leaks are found and extensive corrosion has taken place, the most effective solution is to replace the entire length of deteriorated pipe. The normal installation practices must be followed. They include priming and wrapping of all steel piping, fittings, cathodic protection, etc.
Leaking metal pipe can often be replaced by inserting polyethylene pipe manufactured according to ASTM D2513 in the existing line and making the appropriate connections at both ends. Again, operators are cautioned that allowance for thermal expansion and contraction must be made at lateral and end connections. Operators unfamiliar with insertion techniques, including proper anchoring and offset connections should have a qualified contractor perform this work. Some of the polyethylene pipe manufacturers provide procedures for installation of their products by insertion.
One source of failure in plastic pipe is breaks associated with the transitions between plastic and metal pipes at mechanical fittings. The primary source of the problem is inadequate support of the plastic pipe. It is critical to firmly compact soil under plastic pipe to provide proper support. In practice, however, it is laborious, time consuming and difficult to achieve adequate compaction under such joints. Further, as the soil settles, stress may build and the insert sleeve will cut through the pipe. For example, an insert sleeve must be used in the plastic pipe to provide proper resistance to the clamping pressure of mechanical fittings. This internal tubular sleeve must extend beyond the end of the mechanical fitting. If the pipe is not properly supported at that point, the end of the insert sleeve will act as a shear. This source of failure in plastic pipe can be reduced or eliminated by using a properly designed outer sleeve to prevent stress concentrations at the point where the plastic pipe leaves the mechanical fitting.
The most prevalent cause of breaks or leaks in plastic pipe is "third-party" damage. This is usually caused by an excavator breaking or cutting the pipe. Plastic pipe is more vulnerable to such breaks than steel pipe. The lower strength of plastic pipe, however, is not necessarily a disadvantage. For example, if digging equipment hooks and pulls a steel pipe it may not break, but may be pulled loose from a connection at some distance from the digging. The resulting leaks could go undetected for a period of time and may result in a serious incident. Although there is no assurance that the plastic pipe will not also pull out, it is more likely to break at the point of digging. Then, the break can be detected and repaired. After a leak has been repaired with a coupling or a clamp, a soap-bubble test must be conducted. A CGI/barhole survey of the piping in the vicinity may be considered to ensure no remote pullouts/leaks have occurred.
IT SHOULD BE EMPHASIZED THAT ALL SOURCES OF IGNITION SHOULD BE
KEPT AWAY FROM THE LEAK REPAIR AREA. OPEN FLAMES SHOULD NEVER
BE USED TO DETECT A GAS LEAK OR TO TEST THE ADEQUACY OF A REPAIR
JOB.