Cathodic Protection
The local AHJ has asked if any part of the system piping will be routed below ground and has requested details on required corrosion protection system, trenching, and backfill. They cite the following sections of NFPA2: 7.1.15.3.2 Contact with Earth. 7.1.15.3.2.1 Gas piping in contact with earth or other material that could corrode the piping shall be protected against corrosion in an approved manner. "55:7.1.17.2" 7.1.15.3.2.2 When cathodic protection is provided, it shall be in accordance with 7.1.18. "55:7.1.17.2.1" 7.1.15.3.3 Underground piping shall be installed on at least 6 in. (150 mm) of well-compacted bedding material. "30:27.6.5.1" 7.1.15.3.4 In areas subject to vehicle traffic, the pipe trench shall be deep enough to permit a cover of at least 18 in. (450 mm) of well-compacted backfill material and pavement. "30:27.6.5.2" 7.1.15.3.5 In paved areas where a minimum 2 in. (50 mm) of asphalt is used, backfill between the pipe and the asphalt shall be permitted to be reduced to 8 in. (200 mm) minimum. "30:27.6.5.3" The instrument, air and hydrogen lines are stainless steel and will be installed in a PVC sleeve. In the Panel’s experience, is this adequate cathodic protection for the lines?
The Panel considers two approaches to be acceptable.
- Stainless steel (corrosion resistant) lines embedded in concrete. This keeps the piping out of direct contact with the earth and provides a degree of physical protection from activities such as digging.
- Lines enclosed within a PVC sleeve. The PVC sleeve would usually be directly buried but could also be embedded in concrete for additional protection.
Cathodic protection is also an available and acceptable means of corrosion protection for underground lines, particularly for carbon steel. Each installation should be evaluated for local hazards and soil conditions to develop a thorough corrosion protection system.
FAQ Category
FAQ Keyword
Submission Year
2024
Month
04