Covalence WPCT - Wraparound Pipe Coating

Raychem, now operating under the Covalence brand as part of Seal For Life, offers WPCT shrink sleeves that are widely recognized for their effectiveness in protecting pipeline girth weld joints from corrosion. These sleeves are specifically engineered for use on both distribution and transmission pipelines carrying oil, gas, or water, and are particularly valuable in field applications where robust, reliable corrosion protection is essential.

WPCT shrink sleeves feature a two-layer construction. The first layer is a visco-elastic, butyl-based adhesive that forms a strong bond with both the pipe surface and any existing factory applied pipe coatings. This adhesive is designed for low preheat application, making installation faster and more easier. The second layer consists of a radiation cross-linked, high-density polyethylene (HDPE) backing, which provides mechanical protection and acts as a barrier against moisture. A unique feature of the outer layer is the Permanent Change Indicator (PCI), which visually confirms that the sleeve has fully shrunk and is properly installed.

The application process for WPCT sleeves is straightforward. After the pipe joint is cleaned and preheated, the sleeve is wrapped around the joint. Heat is then applied, causing the sleeve to shrink tightly over the pipe and the adhesive to flow, creating a secure, corrosion-resistant seal. The PCI changes appearance to indicate that the sleeve has been properly installed. WPCT sleeves are compatible with most standard mill-applied pipe coatings and can be used on bare pipe sections and large-radius bends. They are available as pre-cut “Uni-sleeves” with a pre-attached closure patch or in roll form, with closure patches ordered separately.

These sleeves are typically used for corrosion protection of field girth welds in pipelines that operate at ambient or moderately elevated temperatures. They are suitable for both new pipeline construction and maintenance projects and are ideal for large-diameter water pipes or pipelines in moderate climates and low-stress environments.

WPCT sleeves come in a wide range of sizes to accommodate various pipe diameters, from 2.375 inches to 68 inches and beyond (DN50 to DN1700). Standard sleeve widths include 11, 17, 24, and 34 inches (285 mm, 450 mm, 600 mm, and 870 mm), and it is recommended to overlap the sleeve onto the adjacent pipe coating by at least 2 inches (50 mm) on each side, with an additional 10% allowance for shrinkage.

The primary benefits of WPCT shrink sleeves include fast and easy installation with minimal equipment, no requirement for primer, and the provision of a tough, durable barrier against corrosion, mechanical damage, and moisture ingress. Their proven performance and compatibility with a variety of pipeline coatings have made them a trusted choice in the industry.

Raychem pioneered the development of heat-shrinkable sleeve technology, and this legacy continues under the Covalence brand by Seal For Life. Covalence offers a comprehensive range of two- and three-layer heat-shrinkable sleeves for corrosion prevention and mechanical protection in pipeline applications. WPCT shrink sleeves, in particular, are known for their ease of installation, strong adhesion, and long-lasting protection, making them a field-proven solution for pipeline joint corrosion protection.

Two Piece WPC Heat Shrink Sleeve Install

     WPC sleeves (available in numerous different variations: WPCT, WPC100M, WPC60, WPC80, WPC120, WPC65M - though this post focuses specifically on the mastic coated sleeves and WPCT in particular) are composed of irradiated, modified polyolefin backing which upon brief exposure to a temperature in excess of 125C, will shrink from its expanded diameter (as supplied) to a predetermined recovered diameter. The WPC sleeves are precoated internally with a controlled thickness of a thermally activated, self priming, rubber modified thermoplastic adhesive that provides an excellent bond to the metal pipe and yard applied coatings.

     During installation the sleeve is wrapped loosely over the joint and closed with a heat activated 'closure' patch (WPCPIV). The patch is manufactured so that with proper heating the fiber mesh built into the closure backing becomes visible, giving the appearance of an alligator skin texture to the closure strip.

     Internally, the patch is coated with a heat activated high shear adhesive which assures a reliable closure.

Here you see the shrink sleeve and the closure strip as separate parts.

Now on to the install:

Step 1: Joint Preparation.

Remove all weld spatter by grinding, filing or chipping
The exposed steel should be power brushed to a near white metal (as with all coatings, the cleaner the surface, the better the bond)
The steel and yard coated areas should be wiped clean of foreign materials such as dirt, rust, oil, grease and moisture just prior to installation.
The sleeves shall not be applied during rains or sandstorms unless portable welding tents or equivalent are used.
Please note: WPCT (just like WPC65M and WPC100M) requires no primer or epoxy bonding agent.

Field joint being cleaned with a power wire brush

Step 2: Preheating of the Joint Area

Preheat the joint area and the adjacent yard coating using a propane torch, induction heater or ring burner.
WPCT to be preheated to a minimum temperature of 140F
WPC65M to be preheated to a minimum temperature of 165F
WPC100M to be preheated to a minimum temperature of 212F
It is always necessary to verify the temperature with tempil sticks, contact pyrometer or equivalent.

Field joint preheating with a JS-2601 Torch Kit

Verifying that proper preheat temperature has been reached

Step 3:

After preheating (and verifying preheat temp) remove the protective release paper and wrap the shrink sleeve centrally around the weld joint.
The sleeve will overlap itself by at least 50mm