How are Glass-Lined Vessels Made? | De Dietrich

Editor’s Note: This post was originally published in August 2015 and has been updated for accuracy, clarity, and to reflect the latest information.

Whether you’re already running glass-lined reactors in your facility or are just beginning to explore this unique technology, understanding how these vessels are made offers valuable insight into why they’re so effective—and so widely trusted.

From corrosion resistance to exceptional purity, glass-lined steel delivers a powerful combination of properties that standard stainless steel and alloy vessels can’t match. But what exactly goes into making one?

Creating a glass-lined vessel involves three major steps:

1. Producing the glass enamel
2. Fabricating the steel vessel
3. Fusing the glass and steel together

Let’s walk through each phase of this specialized process.

Step 1: Producing the Glass Enamel

The process starts with the production of the enamel—the key material used for the vessel’s glass lining. This enamel is made from carefully selected raw materials that are melted at around 2,500°F (1,400°C) in a rotary furnace. Once melted, the glass is rapidly cooled in water, which fractures it into small granules called frit.

The frit is then dried, milled, and screened into a fine powder, ready to be applied. At De Dietrich, we offer enamel in two color options—blue and white—with identical chemical and mechanical properties. The choice often comes down to visibility needs based on the chemicals used in your process.

Every batch is processed separately in closed containers to prevent contamination. Our proprietary 3009 glass is manufactured at our global headquarters in Zinswiller, France, then shipped to De Dietrich facilities around the world—including our Corpus Christi, Texas site, where steel fabrication and glassing for North American orders take place.

Step 2: Steel Fabrication

Glass-lined vessels have unique geometries, and precise steel fabrication is critical to ensure proper glass bonding and performance. The process begins with shaping the vessel heads and cutting pilot holes to locate nozzles. These holes are expanded using a process called swaging, which involves heating the steel and forcing a die through the opening to form a smooth nozzle seat.

All components that will interface with the glass—such as the drive mounting, jacket, and other attachments—must be installed before glassing begins, since nothing can be welded to the vessel afterward without compromising the lining.

Key welds include:

• Inner shell to the top head (for close-welded designs)
• Bottom head to the shell
• Jacket closure rings around the outlet and knuckle radius

Once welded, the vessel is grit blasted inside and out to create the ideal surface for bonding with glass.

Step 3: Fusing the Glass and Steel

With the steel prepped, the final stage begins—glass application and fusion.

The first layer applied is the ground coat (or “slip”), which adheres to the steel but offers no corrosion resistance. This slurry is sprayed onto the steel, allowed to dry, then fired in an electric furnace at a high temperature to fuse it to the vessel’s surface. After firing, the vessel is slowly cooled in a controlled booth to relieve internal stress.

Subsequent cover coats are applied in a similar cycle—spray, dry, fire, cool—but at slightly lower firing temperatures to avoid re-melting the ground coat. Between each coat, spark and thickness tests are performed to ensure quality and consistency.

The entire process is repeated until the desired thickness is achieved, typically 40–90 mils (1–2 mm). The result? A smooth, durable glass lining that offers exceptional chemical resistance and purity. The glass-to-steel bond is incredibly strong—comparable to pre-stressed concrete, with bonding strength around 16,000 psi.

Final Assembly and Testing

Once the lining is complete, the vessel returns to the welding area for jacket installation. The preassembled jacket shell and head are welded to the vessel’s closure rings, and a diaphragm is added to accommodate thermal expansion.

Next, the vessel undergoes:

• Hydro testing for pressure integrity
• Surface blasting and painting
• Final spark testing and inspection
• Nozzle outfitting with ANSI Class split loose flanges, which help prevent stress on the glass lining

When everything passes inspection, the vessel is ready to ship.

Why It Matters

Glass-lined steel technology isn’t new—it’s been trusted for over 300 years. But today’s manufacturing methods have elevated its reliability, consistency, and versatility, making it the go-to choice for a wide range of industries.

Key Advantages of Glass-Lined Vessels:

• Corrosion Resistance – Protects against most acids and alkalis
• Purity – Ideal for pharmaceuticals and food-grade applications
• Non-stick Surface – Reduces buildup, eases cleaning
• Chemical Versatility – Compatible with a broad range of materials
• Catalytic Inertness – Won’t interact with or alter reactions
• Cost-Effectiveness – Competitive with stainless steel and alloys

By combining the strength of steel with the protective qualities of glass, these vessels offer unmatched performance in demanding chemical environments. Each one is built to the highest standards, with rigorous quality checks throughout production.

Want to dive deeper? Download our Introductory Guide to Glass-Lined Equipment to learn more.