Rehabilitation of fire water mains with trenchless methods – a recipe for success

Fire water mains are considered critical infrastructure in industrial complexes such as chemical plants, refineries or airports, since they are highly safety-related. In ageing industrial premises, however, corrosion and pipe damages frequently impair the smooth operation of such fire water mains. Failures can have catastrophic consequences: Therefore, the maintenance of these facilities is indispensable.

For the rehabilitation of fire water mains, operators are often faced with major challenges, both in technical as well as economic points of view: High pressure ratings up to 232 psi, the limited accessibility of the pipe by overlapping or crossing other pipelines or power lines, lining in concrete and, above all, safety regulations during rehabilitation significantly complicate maintenance work.

Short downtimes are essential for continued operation. With its special properties, Primus Line® helps to overcome these hurdles: Short installation time with minimum space requirements for equipment and small construction pits, high operating pressures of the liner that are absorbed completely independently of the host pipe, and the simultaneously low wall thickness of the liner constitute an ideal system for renovating critical infrastructure such as fire water mains. “Primus Line® has already proven its advantages in this respect – and it does not matter whether the section to be rehabilitated is 65 or 650 feet, as the following projects show,” explains Michael Senbert, head of the business unit for the DACH region at Rädlinger primus line GmbH.

Multiple use at major oil company

Due to the safety regulations and protocols, refineries are particularly dependent of functional fire water mains. Primus Line® has already demonstrated its special capabilities twice for a large, globally active oil company.

The oil company operates a pipeline from the Caspian to the Mediterranean Sea that runs through three countries. In a refinery situated directly on the Caspian Sea, Primus Line® was used to rehabilitate 530 feet of 16-inch fire water mains made of PVC. Since fittings and hydrants had to be reintegrated, this required four rehabilitation sections with only five construction pits. The folding of the liner in U-shape reduced the tensile forces during insertion to a minimum. Therefore, the 90° bends on the course could be passed without any problems. The rehabilitation work on the fire water mains in the refinery was completed after five working days, and as a result, there was almost no impact on the refinery’s operation.

For the same oil company, a total of 4,265 feet of fire water mains are to be rehabilitated in a pumping station in Turkey over the next few years. The first rehabilitation section had a length of 1,740 feet. The host pipes consist of 6.3-inch glass-fibre reinforced epoxy resin (GRE) and have an operating pressure of 174 psi. The pumping station is located at an altitude of 5,250 feet above sea level in an area characterised by heavy snowfall and low temperatures in winter. This was the reason why the activity could only be carried out in the period from April to September.

During installation, the assembly team demonstrated its flexibility in coping with unforeseen events on several occasions:

  • There was a lack of space in the valve shafts. In order to close possible gaps between the flat-cut host pipe and the Primus Line® connector and connection plate, a specially developed fitting piece with variable length was finally installed.
  • The joints of the originally laid out GRE pipe were made of epoxy resin. Its excessive use, however, significant epoxy resin edges had remained in the pipe itself. These were removed with the aid of steel scrapers and a special milling robot before pulling in the Primus Liner.
  • The existing construction drawings did not correspond to the actual isometrics of the fire water system. The drawings were updated almost in real time during installation.
  • Contrary to the as-built drawings, a construction pit could not be opened at the originally planned location: A crude oil pipeline ran underneath. At the new position, the liner had then to pass two horizontal and two vertical 90° bends with r = 1.5 x D. Instead of using the conventional air pressure of 14 psi, in this case the installation team brought the liner into its circular shape with 72 psi of water pressure.

Despite the additional tasks, the assembly team completed the rehabilitation activities with Primus Liner® for this section after a net working time of two days.

Reduced investment and operating costs

For the Caspian Sea site, the oil company compared in a study the costs of repair work using conventional, open-trench construction methods and Primus Line® – with astonishing results: Trenchless rehabilitation reduces the costs per metre to about half, whereas the number of metres of pipe rehabilitated per month increases tenfold to fifteenfold.

Furthermore, the operator accumulated the repair costs including follow-up costs for a three-digit number of leaks at this site over a period of thirteen years. The result was an amount in the low double-digit millions. Rehabilitation of these leaks with Primus Line® would limit the renovation work to five years, reduce the investment sum for the execution period by a third and not entail any follow-up costs.

Small footprint

The sprinkler pipeline of a worldwide leading technology group in the drive and chassis technology from South Germany was leaking. The defective PE pipe only has a length of 246 feet, but runs from the sprinkler control centre in the basement below a production line to a changing room. In addition, there are four 45° bends in the section to be rehabilitated as well as a change in dimension of the nominal line diameter from 11 to 14 inches. Replacing or building a new pipeline would have been far too time-consuming and cost-intensive.

The group therefore requested a long-term rehabilitation with a pressure rate of 232 psi, bend flexibility and a loose-fit liner in one line to be able to pass the change in dimension. Furthermore, the solution should be able to be installed quickly and not restrict or even interrupt the company's three-shift operation. In addition, the cramped conditions in the sprinkler control centre and changing room demanded an extremely space-saving solution.

“And for this, the Primus Liner also takes unusual paths for once,” Senbert explains. “The reel with the folded liner was outside the building. The 10-inch Primus Liner first was unrolled and laid out through a lift, a staircase and the basement floor. It was then pulled in from the changing room into the direction of the sprinkler centre.” After only four working days for the rehabilitation, the fire water pipeline went back into operation. All of the client’s requirements – especially for rapid implementation and the small amount of space required for the construction site equipment – were met.

The small space required for the excavations for the rehabilitation of defective fire water mains was also the main reason for a chemical company from South Africa and the largest refinery in Great Britain to entrust Rädlinger primus line GmbH with rehabilitation work.

Durability of Primus Line®

For a customer from Austria, a refinery located at the Vienna-Schwechat airport, the small construction pits also played an important role for pulling in the Primus Liner. The fire water mains run underneath the refinery, enclosed in concrete and asphalt. Furthermore, other pipelines cross the fire water mains. And neither operation at the refinery nor at the airport were to be affected.

Between 2004 and 2007, a total of 4,265 feet of fire water mains were rehabilitated with Primus Line®, assigned to ten individual projects. The diameters of the pipelines ranged from 8 to 16 inches. The longest rehabilitated section amounted to 279 feet.

This project proves the durability of the Primus Liner that has a service life of 50 years according to the manufacturer’s specification: The rehabilitated fire water mains still function perfectly.

According to the operator, the cost savings compared to open-trench construction were around 50 percent.

Ingredients of the recipe for success

Satisfied customers prove that Primus Line® is an excellent option for the rehabilitation of fire water mains: Under the right conditions, the flexible hose liner masters up to four 90° bends in one rehabilitation section. Bends up to 45° can be negotiated without any problems.  The small construction pits can be created at suitable locations – crossing pipelines can thus be avoided. Little equipment required ties up little personnel: Rädlinger primus line GmbH trains the operators’ maintenance staff accordingly so that they can carry out the rehabilitation activities themselves. This facilitates handling in complex structural conditions or the assignment to danger zones as well. Fast insertion speeds also significantly reduce rehabilitation times and the impact on ongoing operation. “The extension of the service life of the rehabilitated pipelines by 50 years, together with the other advantages mentioned, forms exactly the mixture that makes Primus Line® a recipe for success for the rehabilitation of fire water mains,” Senbert is convinced.

Link to another article "Fire water mains - challenges"

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