Monitoring the operation of Cathodic Protection (CP) systems on 39,000km (22,000 miles) of pipeline through site visits and manual readings is a time consuming and costly task. (Figure 1) Of the 1300 plus rectifier sites in the subject pipeline network, more than 40 sites are accessible only by helicopter and an additional 15-20 sites can only be accessed in the winter months by snowmachine, snowshoe or helicopter. Not only do the costs for performing this function lead one to investigate alternative solutions, but the philosophy of having corrosion technicians' carry out reactive instead of proactive work reduces their productivity.
TransCanada operates a pipeline system that includes over 39,000km (22,000 miles) of pipeline in the provinces of Alberta, Saskatchewan, Manitoba, Ontario, and Quebec Canada. This vast pipeline network is comprised of gathering and transmission systems in Alberta and large diameter transmission piping in the remainder of the provinces listed above. With over 1300 rectifiers, the requirement to monitor the operation of these units on a monthly basis became a time consuming and costly task as the number of rectifiers increased. Some remote locations required helicopter and snowmobile access, further increasing the monitoring costs. Other factors, such as utilizing fewer corrosion technicians in a higher capacity such as troubleshooting, and downsizing of the work force, resulted in the decision to investigate alternatives to the methods being used at the time.
Several types of remote monitoring equipment were evaluated to engineer a solution to this problem. The primary criteria required that the unit be able to communicate the operating parameters of the rectifier via the existing radio system. Since the radio system is used essentially for voice communication, it was decided that the remote units should not automatically transmit information. It was determined that a software application would be developed to poll each unit during the night hours when the radio system was idle.
In addition to the task of ensuring continued operation of the CP systems, a mechanism was needed to provide rectifier interruption capabilities. The mandate to measure close interval (5 to 10 metres spacing) off potentials across the pipeline system on a 3 to 5 year rotation requires that in many areas, up to 30 rectifier sites must be interrupted simultaneously. Many of the sites include multiple high output rectifiers. The present method of visiting each site to install portable interrupters is time consuming and leads to significant reduction in survey productivity. Part of the requirement for the monitoring units was that the hardware and software included in the equipment allow remote setup of a schedule for beginning and ending of rectifier interruption, and for user defined rectifier off and on cycles. This would eliminate a significant amount of redundant work.
REMOTE MONITORING EQUIPMENT / INSTALLATION
Approximately 95% of the pipeline system is covered by an existing voice radio / SCADA system. The vendor of the radio system was asked to develop a radio modem with functionality similar to the existing mobile transceivers including the ability to handle small packets of serial data. A server resides at the head office in Calgary, Alberta, the purpose of which is to direct the request to one of several servers located at company offices across Canada. The information packet contains addressing information that causes it to be directed to, and transmitted from a specific radio tower servicing a geographic region. The packet is received by all radio modems within transmitting range of the tower. Only the modem whose