Ten Smart Ways to Maintain and Repair Large Pipeline

Keeping pipelines open keeps the profits coming. However, it’s not so easy as it sounds. Furmanite’s Tony Scataglia provides some concrete answers.

A specialist monitors a pipeline valve for a low concentration of hydrocarbon leaks. Courtesy of Furmanite.

Do more with less” is the new work reality for the petroleum industry, as the practical effects of competition, workforce reductions and increased regulatory requirements are felt in daily operations. Today, petroleum companies must find cost-effective and efficient ways to meet performance and regulatory goals while keeping their product flowing, avoiding costly plant shutdowns and reducing fugitive emissions. Industrial maintenance and repair companies help meet these challenges, using a variety of techniques to provide rapid, reliable repair and maintenance services to pipelines.

For this article, I selected ten of the most valuable maintenance and repair techniques commonly used at refineries, terminals or bulk plants. It is important to note that these methods are but a sampling of all the maintenance and repair services available to address both operational reliability and regulatory compliance—however, an extremely important sampling, indeed, to maintain the piping flow and economic health of a refinery, terminal or bulk plant.

1. Leak-sealing
Leak sealing on large petroleum piping systems is a typically non-destructive, on-line repair technique that has been practiced since 1922. That was the year that Clay Furman introduced the world’s first pipeline leak-sealing compound. The term on-line, when referring to maintenance and repair services, means that services can be completed without shutting down the flow of product.

Originally, leak sealing was used to stop leaks in the valve packing, the material needed to seal the space between the valve stem and body. The technique involved injecting the compound into the valve stuffing-box (which held the packing) to replace or add to the original packing. Since its introduction nearly 80 years ago, this technique has been used to stop valve leaks. Similar techniques—using packing and sealant to make on-line repairs—have evolved for stopping leaks in piping and other components and equipment.

The later techniques include using wire wraps and clamps to stop flange leaks; enclosures to stop leaks in piping unions, couplings and ells; and total valve enclosures to stop valve leaks when other methods are not feasible. Also, improved sealing compounds have been, and continue to be, developed for use at higher temperatures and in various chemical, nuclear and food grade processes.

The wire wrap technique (see Photo 1) involves peening or hammering brass into the flange gap to create a barrier to hold the sealing compound. The compound is then injected on-line through stud bores to create a new gasket, thus sealing the leak.

The enclosure technique involves manufacturing a piece of hardware and installing it over the leaking area. Sealing compound can then be injected on-line into the enclosure to form a seal over the leaking area and stop the leak.

One of the injection methods used on-line is the drill and tap method. This involves drilling a blind hole and tapping or cutting an injection point into a valve in the packing area. Leak sealing compound and packing materials can be injected on-line using an injection gun to overcome the pressure in the line. The method adds to or replaces the old packing in the valve to stop the leak.

Most leak-sealing techniques can be applied at temperatures ranging from cryogenic to 1,400 degrees Fahrenheit and at pressures from a vacuum to 5,000 pounds psi. Leak sealing forms a sound, continuous molded gasket around the leaking component. Innumerable applications and configurations can be used to contain the leaking component on-line. Clamps, enclosures and boxes can be custom-manufactured to fit around specific leaking components. Repairs can be performed on leaks from valve packing, bonnets, flanges, valve bodies, pressure seals and nearly any piping component.

2. On-site machining
On-site machining is a cost-effective approach used by maintenance and service companies for some customers. The service company sets up an on-site shop equipped with proprietary tools and equipment to match the scale and scope of the customers’ needs. With on-site machining, the pumps, valves, pipes and pressure vessels do not have to be removed and sent to a machining facility. Therefore, the cost and time saving can be significant.

Typical on-site machining applications include flange facing (see Photo 2), pipe beveling, in-line boring, journal turning, drilling and tapping, grinding and polishing, valve rebuilding and milling.

Photo 2: A machining specialist sets up a flange-facing machine to recondition the badly eroded sealing surface of an 18-inch, 300-pound flange. Courtesy of Furmanite.

3. Fugitive emissions monitoring
Fugitive emissions monitoring is a technique for detecting extremely small concentrations (parts per million volumes) of hydrocarbons escaping from pipelines. Such monitoring is necessary for decreasing product losses, as well as for complying with federal and state regulations and operating permit stipulations. Finding and repairing such low-level leaks not only reduces product losses, but also costs less than repairing leaks that have progressed to the point of dripping or greater (and more obvious) volume losses.

Most fugitive emission monitoring programs include process reviews; system identification; use of intrinsically safe, portable inspection equipment; data logging systems; data management and reporting services; emission estimates; and detailed future control plans. In addition, regulatory consulting and research, training programs and technical manual development can be provided if necessary.

The monitoring is performed using a portable Flame Ionization Detector coupled with a hand-held data logging system (see Lead Photo). The monitoring data is uploaded to PC-based software for tracking purposes. This is done to produce reports for government regulatory compliance, estimate emissions and plan for emissions reduction through leak repair programs.

4. Bolting services
In the large pipeline dictionary, a bolted connection is a combination of studs and nuts used to connect equipment, such as flanges that connect pipes. Today’s emphasis on safety, economics and environmental protection from fugitive emissions has made the elimination of leaks from bolted connections a high priority. To ensure that a petroleum plant continues to operate at maximum efficiency, a complete bolting service, from design to final tightening and measurement, is required.

Bolting services include bolt tensioning, torque tightening and bolt stress measuring. These services are increasingly important in today’s high-temperature, high-pressure plants operating under increased run duration expectations. Bolt tensioning—tightening threaded fasteners uniformly with advanced hydraulic technology—ensures that gaskets are com- pressed as required by the manufacturer to achieve joint integrity. Torque tightening is done with pneumatically energized hydraulic torque wrenches. Bolt stress measuring involves mechanical or ultrasonic devices to ensure reliable measurements.

5. Hydraulic-lift valve testing
Several hydraulic-lift systems are available to test safety and relief valves on-line for set point and other parameters. Regular testing and repairs help to hold down replacement costs, meet stringent safety standards and minimize losses due to pipeline leakage.

6. Motor diagnostic testing
Diagnostic testing is the first step in preventive maintenance programs for critical motors used in large pipeline systems. Various on-line and off-line motor diagnostic systems can reliably test and predict failures of the motors. Such analyses provide the basis for planning maintenance services to avoid untimely failures.

One on-line system, Framatome Technologies’ Electric Motor Performance Analysis and Trending Hardware (EMPATH®), measures and analyzes electric motor current and voltage on critical processes and equipment. EMPATH™ tests for imperfections. These include: rotor bar deterioration; rotor eccentricity; stator phase imbalance; motor speed and slip; gear and belt imperfections; average running current; stroke-time on assemblies with defined start and stop points; changing friction forces and torsional vibration; and dynamic loading.

The EMPATH™ system harnesses the technology of Motor Current Signature Analysis (MCSA), which is used to analyze the health or deterioration of electric motors and the machinery being driven (see Photo 3).

7. Hot tapping
Hot tapping is a technique for putting a hole in a pressurized line or vessel. Such holes are usually for making tie-ins and branch connections or for installing instruments. The hot tapping technique can be used without shutting down the system, which also avoids the need to decontaminate the process line or vessel.

Hot tapping can be done on line from vacuum to 2,500 pounds psi and from cryogenics to 1500 degrees F. The technique requires the use of a fitting attached to the item being tapped, a valve, a special boring machine operating through a packing gland and a housing for the cutting tool. Machining is done by opening the valve and running the boring machine until the hole is complete, and then retracting the machine until the valve can be closed and the machine removed. The valve is then ready to receive whatever is being installed in the hole.

Hot tapping services range from small, emergency tie-ins to larger modifications to the operating plant. Hot tapping equipment can tap into lines or vessels containing hydrocarbons, natural gas, water, steam and heavy oil products.

8. Line plugging
Line plugging is used to isolate system components for repair or replacement and provides a shut-off option for pressurized pipes and vessels. The plugging of a petroleum pipeline is accomplished by first performing a hot tap and then using a special plugging machine. By inserting a line-plugging head into the line flow and using a special sealing element attached to the plugging head, the flow is stopped. This can be done without shutting down a whole system. Thus, line plugging, which is safe and cost-effective, is an important part of the overall “pipeline intervention system” for keeping a petroleum processing system up and running.

Photo 4: Technicians provide double isolation with simultaneous freezing of a vertical and horizontal line. Partly visible in lower right corner is the TV-like screen of a heat flux monitoring system. Courtesy of Furmanite.

9. Line freezing
Line freezing is another technique for isolating system components; this allows for repairs to be performed without shutting the system down. This specialized service involves installing a jacket around the pipe and injecting liquid nitrogen between the jacket and the pipe, causing a freeze plug to form inside the pipe (see Photo 4). When the plug reaches the desired length, work can be performed on the system. So long as the liquid nitrogen supply to the jacket continues, the freeze plug can be maintained.

Line freezing can be done on various piping materials, including carbon steel, cast iron, nickel alloy, aluminum alloy, copper-based alloy and stainless steel. The technique can be used when line stop fittings or welding jobs are needed.

10. Pipe cutting and beveling
Pipe cutting and beveling are two interrelated maintenance techniques that also help reduce “down” time. Many pipeline service companies use a variety of multi-purpose cutting equipment to meet such needs as the parting of vessels and the cutting and profiling of pipes, boiler headers, valves and tubes.

Pipe cutting and beveling services can cover pipes of any diameter and wall thickness. Further, pipe cutting allows maintenance companies to remove weld material and repair heat-affected zones, weld slag, general cracking and other defects that could cause unwanted shut-downs.

More for less
Today’s worldwide “more for less” philosophy applies to the petroleum industry where the goal is to stay on-line and in production every possible second. That is why industrial service and maintenance companies strive to provide the petroleum industry with effective solutions to their toughest challenges and help to keep the product flowing.

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