Plumber's Licensing Exam: Gas Piping Installations

The proper and safe installation of natural gas to the population is essential. To ensure that this is done, interested persons combined their experiences and knowledge to develop what we now know as the UPC. The principal hazards of improper and inadequate fuel gas installation include poor equipment operation, fire, explosion, and asphyxiation.

Objectives
- Identify materials that are permitted by the codes for the installation of fuel gas supply and distribution systems.
- Calculate the proper size of a gas main and gas distribution system.
- Develop familiarity with the potential hazards present in a gas distribution system.

General Rules
Coverage of gas piping systems must extend from the point of delivery to the appliance connection. The point of delivery is the outlet of the service meter assembly or the service shutoff valve if no meter is provided (UPC 1201.1). Upon installation of a fuel gas system, it is required that the systems be inspected by the Authority Having Jurisdiction. There are two inspections: the rough piping inspection, which is done before the installed pipes are covered up in walls; and the final inspection, when the portions of gas piping that are to be concealed have been concealed and fixtures and appliances have not yet been attached.

The rough inspection is done to determine that the gas piping size, material, and installation meet the requirements of the code.
The final inspection is an air test, and the gauges used in conducting the test shall be in accordance with Section 318.0 of the UPC. This inspection shall include an air, CO2, or nitrogen pressure test, and the piping must withstand a pressure of 10 psi gauge pressure. The length of time that this test should last will be determined by the Authority Having Jurisdiction, but in no case less than 15 minutes, and there must not be a drop in pressure. For welded piping and for piping carrying gas pressure that is in excess of 14 inches water column pressure, the test pressure shall not be less than 60 psi for a period of time satisfactory to the Authority Having Jurisdiction. The permit holder will supply all the necessary apparatuses to perform the test (UPC 1213.13).
Gas connection and appliances can be disconnected by the Authority Having Jurisdiction or the serving gas supplier if it is found that the gas piping is not in accordance with the requirements of the UPC 1201, or is defective and in such condition as to endanger life or property. Upon the completion of the final inspection and the finding that the gas piping installation is in accordance with the provisions of the relevant codes, the Authority Having Jurisdiction shall then issue a certificate of inspection.
Before a gas piping system can be installed, a plan or piping sketch shall be prepared for approval of the Authority Having Jurisdiction authorizing the installation of the gas system. This plan must show the proposed location of piping, the size of the different branches, the various load demands, and the location of the point of delivery.

Materials
When installing gas piping systems, the UPC states that pipes, fitting, and valves must be free of any foreign material and ascertained as approved for the system by NFPA 54:5.6.1.2. Cast-iron pipe shall not be used—only steel and wrought-iron pipe, which shall not be less than standard weight (schedule 40). It shall comply with the following standards: (1) ASME B36.10, (2) ASTM A53, and (3) ASTM A106 (NFPA 54:5.6.2.2).
Copper and brass pipes shall not be used where the gas contains more than an average 0.3 grains of hydrogen sulfide per 100 standard cubic feet (scf) of gas (NFAP 54:5.6.2.3). The method used to join this piping will be either with threads or the pipe should be welded together (UPC 1208).

Pressure
Correct gas pressure must be supplied to an appliance, or else it will not perform correctly and may become harmful to life and property. As a result, a line pressure regulator must be installed where the gas supply pressure exceeds that at which the appliance is designed to operate (UPC 1208.7, NFPA 54–12:5.8.1).
In light of this code, the installer needs to verify the appliance design pressure and ensure that the gas supply pressure does not exceed that design pressure. Inspectors need to verify that overpressure protection is installed to code and manufacturer’s instructions, when appropriate (UPC 1208.7.1). When gas lines are installed under grade or slab it must be done in a conduit. This conduit, if it terminates inside a building, must not be sealed. This will allow for any gas buildup to escape and not accumulate inside of the conduit (UPC 1210.1.6.2). This termination point must also be made accessible.
All gas piping systems for industrial, commercial, and public facilities must be purged to the outdoors only. The purging of these systems shall be in accordance with the provisions of the UPC Section 1213.6.1.1 through Section 1213.6.1.4, where the piping systems meet either of the following: (1) the design operation gas pressure exceeds 2 psig, or (2) the piping being purged contains one or more sections of pipe or tubing meeting the size and length criteria of UPC Table 1213.6.1.

Sizing
When installing a gas piping system, you must ensure that it is sized correctly or else you may end up with insufficient gas to supply the demand that is needed. As a result, when having to size piping for gas systems, it is necessary to refer to UPC Table 1216.2(1) through Table 1216.2(36) (UPC 1215.0 and 1216.0 references).