Industrial Case Study: High-Density Polyethylene (HDPE) Pipe Lining

A construction facility near Ft. McMurray, Alberta that produces synthetic crude oil from oil sands, requires large volumes of water (12,500 m³/ hr), to separate the bitumen from the sand. Regulatory agreements require the client to be a zero liquid discharge facility.

The water is re-cycled through tailings ponds and has high salinity (primarily chlorides, sulfates, sodium and bicarbonate) and microbiological activity as well as dissolved oxygen, and varying amounts of fine particles. It therefore is corrosive and has high scaling and fouling tendencies.

In addition to its use in separating the bitumen from the oil sand, this recycled water (RCW) is used as a cooling medium for other processes in the plant. The continuous operation of the RCW system is critical to preventing unexpected plant outages, which could potentially result lost production costs in the millions.

The RCW system incorporates various products to address expected pipe corrosion issues. One included product was a 1,430 meter long section of buried 52” diameter steel pipe within the system. This section did not operate at the elevated temperatures of the rest of the system, which made the large-diameter HDPE pipe lining system an ideal choice for a corrosion barrier.

Solution

A High Density Polyethylene (HDPE) pipe lining system can be installed as an undersized “slip liner” or as an oversized, interference fit liner. The most common method for pressure applications is the interference fit method. This type of system utilizes a high-density polyethylene pipe with an outer diameter that is larger than the inside diameter of the steel pipe. The lining system is installed into the pipeline utilizing a braided cable (Wireline) and a means of reducing the diameter of the HDPE pipe during insertion. The Tite Liner® method utilizes a Roller Reduction Box to temporarily reduce the diameter while pulling the liner in via a wireline. After insertion, the liner naturally reverts back to its original O.D., resulting in an interference fit to the steel.

Original HDPE pipe installations were completed in Western Canada in 1986 and, to date; over 10,000 km of this type of lining system is in use solving a variety of service condition needs.

Installation of the Large-Diameter HDPE Pipe Lining

The 52” RCW line is 1430 meters long and constructed in 10 flanged sections to facilitate insertion of 90-degree elbows and tees. The O.D. is 52” with a .500” wall thickness, resulting in an I.D. of 51”. The lengths of the sections range from 20 meters to about 300 meters. During design of the 52” line, some of the details for consideration included:

  1. The HDPE pipe lining system would be only slightly oversized (51.25” O.D. inside 51” bore). The wall thickness of the liner would be 1.25”, a length considered the minimum for the installation method.
  2. Most of the size specific installation equipment could be fabricated. Other items like the pulling winch with >100,000-pound capacity and the large diameter McElroy fusion machine, could be leased.
  3. Given the short length of some of the steel sections, it was apparent that it would be extremely difficult to conventionally install HDPE stub ends. The best alternative appeared to be flaring the liner ends at the RFWN flanges.
  4. A significant amount of on site support would be required from the steel pipeline Contractor. Flaring of the HDPE pipe to facilitate a connection at a flange had been done before, although never in a diameter as large as 52”. After a successful flaring trial, installation could begin.

The process began with ten (10) flanged sections of steel pipe which were welded and tested. All RFWN flanges used were slightly modified to allow for liner insertion and flaring. The flanges had an identical bore (51”), along with a radius machined at the raised face. This radius provided a suitable base for the flared liner.

Most of the flanged pipeline sections were left above grade and then lowered into the ditch after lining. The longest sections, which were too heavy or awkward to handle in a single length, were lowered into the ditch in more than one piece, and then welded together

The lining system was butt fusion joined utilizing a McElroy 2065 fusion machine. The machine and operators set up inside a large tent that offered a controlled working environment. The fusion joining procedure, operator and equipment were pre-qualified by completing sample fusions, which were destructively tested (ASTM D638). After this process a test piece was inspected for any damage resulting from the pull.

During installation, the lining system was inserted at approximately 10 meters per minute. On the longer sections, a lubricant was applied to the outside of the liner at the Roller Box. Installation was completed by terminating the liner ends with the same flaring process.

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