usually includes at least one long time period at a higher-than-normal pres- 

 sure. 



If leaks are evident (noted by unusual pressure drops), they must be 

 located and repaired. Pressure gauges along the route can isolate relatively 

 short sections that may contain the leaks. If water is the fluid used, wet 

 spots in the soil may give clues to the leak area. If air or gas is used for 

 testing, sensitive microphones or "gas sniffers" can be used by crewmen walking 

 the pipeline route to detect the leak. When the location of the leak has been 

 determined, a crew must move in to make repairs. Equipment will include 

 dragline or backhoe, side-boom tractor, materials for patching the wrapping, 

 and an x-ray crew. The excavation equipment digs out the earth around the 

 pipe. The coating is removed and visually inspected. Sometimes an x-ray of 

 the weld is required to check the length of the welding fault. The joint is 

 rewelded, and a new x-ray is taken. Then the spot is recleaned, primed, 

 coated, and wrapped. The excavation is refilled, and the equipment is removed. 



Pipeline operation. Pipeline operation is long term, measured in decades. 

 The activities associated with pipeline operation may be divided into opera- 

 tions at the pump station and along the pipeline route. 



Pump stations that are not simply booster facilities along the route are 

 manned at least part of the day, and sometimes continuously. Booster stations 

 are visited nearly every day. Thus, there is normal traffic back and forth 

 with shift changes on a regular basis. Most of the activities involve moni- 

 toring equipment; switching and diverting flows in the pipelines; maintenance 

 of the pumps and compressors; maintenance of outside equipment, including 

 scraping and painting; cleaning minor drips and leaks i^rom valves; and maintain- 

 ing the grounds. The inside of the pipe is cleaned by scraping the line 

 periodically to remove paraffin and scale. Sometimes large spheres are used 

 to separate fluids being pumped in the line. The removal of the spheres and 

 scrapers can result in small amounts of petroleum materials being exposed 

 outside the pipe. However, the amount is small and pump stations have sumps 

 and drains built into the launchers, traps, and areas where they are used to 

 confine any materials that might leak. Paraffin is a hard waxy material and 

 is handled as a solid waste. 



Pipeline activities. Pipelines are monitored constantly for sudden pres- 

 sure drops indicating leaks. Pipeline companies also make visual inspections 

 of pipelines from low-flying aircraft as often as several times a week. 

 Observers look for wet spots or signs of oil and gas bubbles, particularly in 

 marshy areas. Some inspection aircraft have "gas sniffers" to detect gas 

 leaks from the air. 



On-ground maintenance operations involve the many block valves and bypass 

 valves located along a pipeline route. These are periodically checked to 

 ensure their operation in case of leaks. Surface facilities at these valve 



121 



