Sealing Large-Diameter Cast-Iron Pipe Joints Under Live Conditions. (Quarterly Report, March 25, 2005-June 24, 2005).

[摘要] Utilities in the U.S. operate over 75,000 km (47,000 miles) of old cast-iron pipes for gas distribution. Bell-and-spigot joints that connect pipe sections together tend to leak as these pipes age. Current repair practices are costly and highly disruptive. The objective of this program is to design, test and commercialize a robotic system capable of sealing multiple castiron bell and spigot joints from a single pipe entry point. The proposed system will perform repairs with the pipe in service by traveling through the pipe, cleaning each joint surface, and installing a stainless-steel sleeve lined with an epoxy-impregnated felt across the joint. This approach will save considerable time and labor, minimize excavation, avoid traffic disruption, and eliminate any requirement to interrupt service to customers (which would result in enormous expense to utilities). Technical challenges include: (1) repair sleeves must compensate for diametric variation and eccentricity of old cast-iron pipes; (2) the assembly must travel long distances through pipes containing debris; (3) the pipe wall must be effectively cleaned in the immediate area of the joint to assure good bonding of the sleeve; and (4) an innovative bolt-on entry fitting is required to conduct safe repair operations on live mains. The development effort is divided into eleven tasks. Task 1 (Program Management) and Task 2 (Establishment of Detailed Design Specifications) were completed previously. Task 3 (Design and Fabricate Ratcheting Stainless-Steel Repair Sleeves) progressed to installing prototype sleeves in test cast-iron pipe segments. The sleeve system design has been improved based on laboratory testing in preparation for field trials. Efforts in the current quarter continued to be focused on Tasks 48. Highly valuable lessons were learned from field tests of the 4-inch gas pipe repair robot in cast-iron pipe at Public Service Electric & Gas. (These field tests were reported previously.) Several design issues were identified which need to be implemented in both the small- and large-diameter repair robots. For Task 4 (Design, Fabricate and Test Patch Setting Robotic Train), previous problems with bladder design and elastomeric material expansion in the large mains were addressed. A new bladder based on a commercially available design was obtained and tested with success. Minor improvements (such as additional rows of ratchets) were highlighted during patch-setting tests and have been added to the design.

[发布机构] Technical Information Center Oak Ridge Tennessee

[学科分类] 工程和技术（综合）

[关键词] Gas utilities;Gas distribution;Pipe joints;Cast-iron;Gas pipelines