From its early days as a method of connecting signalling system cables to railway lines, pin brazing is now increasingly being specified as a safe, quick and cost effective alternative to exothermic welding attachment techniques, which although cheap do have some distinct disadvantages.
Mechanical clamp type devices are not easy to apply, particularly as a retrofit on an existing buried pipeline and conductive resin systems need sufficient cure time to ensure a positive connection. thermit welding requires skilled application whereas pin brazing is safe, quick and reliable and permits a large number of connections to be made in a relatively short time using unskilled labour -- training takes about an hour. The process can be carried out in all weathers and damp pipes pose no problem.
Pin brazing dates back to the early 1950s but it was not until the 1980s that BAC Corrosion Control introduced its own fully portable equipment to produce electrical bonds for connections in pipeline cathodic protection systems. Each connection takes about a minute to complete. It is the most common method used in the North Sea, is extensively used in the Middle East and is approved for use by Transco. For ductile or cast iron pipes, threaded pins to accept a crimped cable lug and a nut are used. For steel pipes, either threaded brazing pins with nuts or a special lug for direct cable brazing is the norm. In a cathodic protection system there are often a great number of connections for anode cables, test posts and measuring cables to be made.
The portable nature of the equipment means that connections can be made in almost any location above or below ground and if necessary overhead. In situations where a great many connections need to be made in one place such as pipecoating yards and pipelay barges, the BAC pin brazing system can use a welding generator as its power source.
As demand for pipelines as a cost effective means of transporting fluids over vast distances continues to grow so does pressure from the world’s safety bodies to ensure that installations conform to accepted standards. Welding of steel pipelines on land and offshore is a critical element and operators need to ensure that undue stresses or damage to the internals of lined pipes are not being created when attaching components for protective systems. Extensive tests have confirmed that as pin brazing is a relatively low temperature process, the heat affected zone is only a small percentage of that produced by thermit welding techniques which, being exothermic produce high temperatures. These can generate stresses in the pipe and possibly damage internal linings.