A heavily corroded 30-metre section of 450mm ductile iron sewer pipe in an underground force main in Hawaii is refurbished by an engineering company, rectifying a previous repair attempt which put a 75mm round hole in the line.

Case Study Overview

Site Sewer force main in underground vault
Location Hawaii
Pipe Type 450mm ductile iron
Pressure 3 bar
Repair Type Pipe repair and refurbishment
Products Industrial Metal Epoxy Paste, Liquid Metal Epoxy Coating, SylWrap HD Pipe Repair Bandage

Pipe Defect

The 450 ductile iron pipe was installed inside the vault in the 1970s. It was the final section before the sewer force main discharged into a manhole housing a gravity collection system. Its operating pressure was around 3 bar.

Conditions inside the vault over a period of 50 years had led to severe corrosion and a significantly weakened pipe. A previous attempt to clean off the main before adding structural strength succeeded only in sandblasting a 75mm round hole in the pipe.

The hole was located in a difficult position between a flange and the concrete wall where the main entered the manhole. Wastewater was able to escape through the hole when the line was pressurised.

An engineering company were called in to seal the leak. They ordered a custom-made pipe repair clamp fabricated specifically for the line.

But because the surface was so deformed, the clamp could not achieve a watertight seal. There were also concerns that tightening the clamp fully could lead to the metalwork collapsing.

The contractors now needed to improve the surface profile of the pipe to make the clamp effective, followed by refurbishment of the entire 30-metre section inside the vault to keep the main operational and prevent further degrading.

SylWrap Solution

Stages 2, 3 and 4 of the Sylmasta Pipe Refurbishment System were used for the ductile iron sewer main repair. Loose material was carefully cleaned off using wire brushes, after which attention turned to the hole.

Wire mesh was used to bridge the gap. 5kg of Industrial Metal Epoxy Paste was applied around the entire diameter of the pipe between the flange and wall, including over the hall. The wire mesh prevented any epoxy paste entering the pipe.

Industrial Metal filled all imperfections in the pipe surface and increased the thickness of the line surrounding hole. Once cured, it left a rebuilt area of pipe strong enough to withstand the clamp being fitted and smooth enough for achieving a watertight seal.

10kg of Liquid Metal Epoxy Coating was then painted onto the main, two flanges at either end and a coupling in the middle. Two coatings were used.

Liquid Metal cured to form a new metallic, hard-wearing pipe exterior for the main, providing a shield against corrosion and a waterproof barrier containing future leaks.

Finally, the pipe was reinforced with 20 x SYL866HD SylWrap HD Pipe Repair Bandage. Based on the operating pressure of 3 bar, SylWrap HD was wrapped around the pipe for six layers. It set to form a rock-hard, impact resistant, final layer of protection.

Outcome

From sealing the hole to reinforcement with SylWrap HD, the repair was completed over the course of one week. The most time-consuming aspect was the four hour re-coat time of Liquid Metal, although this could have been accelerated using a heat gun.

At a total cost of just under $5000 including product delivery to Hawaii, refurbishing the corroded sewer main provided a significant financial saving compared with ripping out and replacing the pipe.

Follow Up

The engineers making the repair were particularly impressed with how easy all three Sylmasta products were to apply given the cramped, wet and dirty conditions inside the vault.

They had originally planned to encase the main in concrete after refurbishment as an additional protective measure. This was no longer deemed necessary once they saw the strength of the repair.

Products Used

Industrial Metal
Epoxy paste used to strengthen pipes by rebuilding and thickening exterior surfaces

Liquid Metal
Epoxy coating brush applied to refurbish and protect pipelines suffering from heavy corrosion

SylWrap HD Bandage
Water-activated wrap which reinforces pipes by forming a rock-hard outer shell

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