Proven Solution for Sealing Industrial Ductwork: Covalence TWDB

 

If you work with industrial HVAC and piping systems, chances are you’ve come across Covalence (formerly Raychem) TWDB. TWDB is a thermofit, wrap-around duct band specifically designed to create a pressure-tight seal on ductwork—helping ensure long-term system integrity even in challenging environments.

Engineered for reliability, TWDB delivers a durable seal that stands up to demanding conditions where traditional sealing methods often fall short. Once installed, it provides confidence that your ductwork will remain protected and leak-free over the long haul.

For ease of use in the field, TWDB is stocked in both 3" and 4" widths and supplied in a 165-foot continuous roll. Each roll is packaged in a purpose-built box that allows installers to quickly and accurately measure the required length before cutting, reducing waste and improving installation efficiency.

Installation is straightforward and familiar to most crews. TWDB can be applied using either a propane torch or an industrial heat gun, allowing it to conform tightly to the duct surface and activate the thermofit properties that make the seal so effective.

TWDB is not a new or unproven product—it has seen consistent use for decades across industrial applications. That longevity speaks to its performance, reliability, and the trust it has earned among contractors and maintenance professionals alike.

When long-term sealing performance matters, Covalence TWDB remains a simple, proven solution.

Waterwrap: A 50-Year Journey That Started with an Opportunity

 

It was October of 1975 when a team of Raychem pipeliners headed south to Grand Gulf, Mississippi with a simple goal: solve a real problem in the field.

At the time, the large-diameter pipe market was struggling with a familiar challenge—how to reliably coat field joints in a way that was consistent, repeatable, and practical for crews working under tough conditions. And in those days, when Raychem identified a need, the company didn’t hesitate. They saw opportunity.

In the mid-1970s, Raychem was best known for manufacturing tubular heat-shrink sleeves for oil and gas pipelines. One of the flagship products was the TSS (Tubular Shrink Sleeve). It worked well—but only when pipe sizes and logistics allowed for a sleeve that could slide over the pipe.

Large-diameter pipe created a new challenge. You couldn’t easily slip a tubular sleeve over it in the field. So Raychem’s engineers did what they did best: they invented something new.

The result was a wrap-around heat-shrink sleeve prototype designed specifically for large pipe. And what did they call it?

LTSS — Large Tubular Shrink Sleeve
(…even though it wasn’t actually supplied as a tube).

Raychem was exceptional at innovation and rapid R&D. Naming products? Maybe not their strongest suit—but the technology was what mattered.

Armed with LTSS sleeves and a team of field technicians, Raychem went to work evaluating the new design under real-world conditions. What’s fascinating—at least to those of us who live and breathe pipeline coatings—is that this LTSS prototype was the first generation of what we now know as Waterwrap.

Over the decades, that original concept evolved dramatically:

• Improved formulations

• New backing materials

• Multiple thickness options

• Enhanced performance for demanding environments

Each improvement built on the last, refining the product into something truly special.

Waterwrap Today

Fast-forward nearly 50 years, and Waterwrap stands as the premier field joint coating for water pipelines. It’s trusted around the world for its reliability, ease of installation, and long-term performance.

Even more impressive? Waterwrap has proven itself capable in weld-after-backfill applications—one of the most demanding scenarios a field joint coating can face.

Every proven product has a beginning. For Waterwrap, that beginning was a forward-thinking team in 1975, a job site in Mississippi, and a willingness to rethink how field joints could be protected.

So here’s to 1975 Raychem—seeing a problem, seizing an opportunity, and laying the groundwork for a product that’s still protecting pipelines half a century later.

Well done.

Waterwrap: Weld after backfill sleeve

 Coating CHALLENGE: Covalence Waterwrap (Weld After Backfill)

Today we’re taking a look at Covalence Waterwrap – Weld After Backfill (WAB), a product designed for one of the most demanding coating applications you’ll ever encounter.

Let’s start with the baseline challenge.

You’re dealing with massive, heavy pipe. It’s already in the ground. Preheating a pipe with that much thermal mass is no small task. Installation crews have to be absolutely disciplined—every square inch of the sleeve must be properly heated to ensure a reliable bond. None of this is easy on a good day.

Now add this twist:
the pipe is going to be welded after the sleeve has been installed.

Yeah… kind of nuts.

Don’t let the photo above fool you (I borrowed it from tomorrow’s history post, which goes all the way back to 1975). What’s interesting about that image isn’t just what you see—it’s what it represents.

The product shown, LTSS, was literally Raychem’s first serious attempt at developing a solution for large-diameter water lines. It was an important starting point, but very much a first pass.

Fast forward to today.

Waterwrap WAB is the result of dozens of generations of product evolution, refined over decades. Each iteration has been driven by real-world field experience—improving long-term performance on the pipe while simultaneously making life easier for installation crews. Better materials. Better installation tolerance. Better outcomes where failure simply isn’t an option.

That kind of evolution matters when you’re coating buried pipe, welding after backfill, and asking a system to perform flawlessly for decades underground.

If you’re in the water pipeline construction world and dealing with these kinds of challenges, we’d love to talk. There’s a lot of hard-earned history—and a lot of practical knowledge—behind today’s Waterwrap systems, and we’re always happy to share it.