Heat–Shrink Sleeves

Canusa heat-shrink sleeves are most often used for girth weld coating. They guarantee a high quality joint protection and are compatible with all anti–corrosion mainline coating systems.

Heat–shrink sleeves comprise of a three–layer coating system. The outer layer consists of a dual laminated polyolefin backing – a cross–linked and pre–stretched sheet, which upon heating will shrink the polyolefin layer
to its original size, and copolymer hot melt or mastic adhesive. Under the heat–shrink 2–layer film is a 2–part liquid epoxy primer.

The two–component epoxy primer is one of the major components of the corrosion protection system.

Competitors' shrink sleeves result in a non–uniform corrosion barrier layer of epoxy coatings because they are installed over "wet" primer. In such case, during installation and shrinking, the primer is distorted. This liquid primer runs off the convex parts of the welded joint, or it is rubbed off during installation, thus leaving these parts practically unprotected by primer.

Only when the sleeve is installed over primer that has already been cured, as Canusa heat shrink systems are, the benefits of the corrosion protection system are fully realized.

When heat is applied to the sleeve wrapped around a joint,
the adhesive melts and becomes a liquid, while the sleeve backing begins to shrink.

The radial shrinking forces of the sleeve squeeze the fluid adhesive into all the pipe surface irregularities, while the sleeve conforms tightly to the joint profile and to the mainline coating.

Upon cooling, the adhesive solidifies, effecting a tough bond
to the pipe and the mainline coating.

Canusa heat–shrink sleeve
being installed using gas torch

There are three basic types of sleeves used to protect joints (fig. below):

Sleeve Backing Types

Backings are available for normal or heavy duty service.

• Yellow backing is typically used for buried application and also for hot climates to reflect the heat during prolonged exposure to the sun during construction.
• Black UV resistant backing is used for above ground applications.

The yellow sleeves come with standard built–in thermochromic pigment which changes to orange at the correct temperature
and then reverts to yellow upon cooling.

The backing can optionally be supplied with a surface painted indicator.

Adhesive Types

The sleeve adhesives falls into two main categories mastics
and hotmelts.

Mastics are tacky, pressure–sensitive, sticky, and softer adhesives. Therefore they bond relatively easily to substrates upon contact and pressure. The heat helps the adhesive flow and thus enhances the bonding action.

They are more forgiving than hotmelt adhesives to installation conditions, such as pipe cleanliness and heat input. Mastics have lower but still good peel strength and generally good cathodic disbondment resistance. Mastic sleeves are self healing; a puncture in the backing is sealed by the mastic.

Hotmelts are non–tacky, dry, hard adhesives based
on semicrystalline resins. They have very high shear strengths,
and often high peel strengths.

Hotmelts are formulated to operate at high temperatures.

On the downside, they require a much higher degree of surface cleanliness and high preheats. The preheat temperature can be reduced by using epoxy primer with appropriate sleeves.

There is a full range of heat shrink sleeves, tapes, and systems based on in–service and application requirements.

Canusa Product Line

application of
Canusa heat shrink sleeve

Special heat–shrinkable corrosion protection sleeves are designed for hot water transmission pipelines.

These sleeves provide not only corrosion protection for the joint, but thermal insulation as well.

Local damage to coating may be repaired with melt sticks
and special patches.

Similar patches are used for corrosion protection of points where cathodic protection electrodes attach to the pipe.

patch to cover cathodic protection hookup