Walking Beam Furnace Water-Cooled Skid Insulation: Cutting Cooling-Water Heat Loss

A walking beam reheating furnace spends a surprising share of its fuel heating water, not steel. The water-cooled skid rails and support columns that carry slabs through the furnace are a permanent heat sink: field studies of walking beam furnaces typically attribute on the order of 15% of furnace heat input to the cooling water. Insulating those water-cooled components with nano microporous blankets attacks that loss directly.

The Skid-Mark Problem

Water-cooled skids do two things to a reheating furnace. First, they drain heat — the cooling water leaves carrying energy that should have gone into the slabs. Second, they cool the slab locally where it rests on the skid, producing the well-known ‘skid marks’: colder bands that force the mill to roll with uneven temperature and often push the furnace to run hotter than the slab average would require. Both problems trace back to the same cause: too much heat crossing the skid into the water.

How the Skids Are Insulated

The standard fix is to wrap the water-cooled pipes in insulation before the refractory is applied. With nano microporous material, two layers of 5 mm blanket are wrapped over the water-cooled pipes, fixed with steel wire, and then the castable is applied over them.

• Clean the water-cooled pipe surface.
• Wrap two layers of 5 mm microporous blanket around the pipe.
• Secure the blanket with steel wire so it stays in place during castable application.
• Apply the castable over the blanket to form the finished skid profile.

The blanket is flexible and cuttable, so it follows the pipe and the skid profile closely, with no air gaps for heat to short-circuit through.

What the Numbers Show

Compared with ceramic fibre insulation of the skids, wrapping the water-cooled components in microporous blanket is reported to reduce the heat carried away by the cooling water by roughly 24%. Since the cooling water is responsible for a large slice of the furnace’s total heat loss, that single change translates into a meaningful drop in fuel consumption per tonne of steel reheated.

• Lower cooling-water heat loss — reported around 24% less than ceramic fibre.
• Reduced fuel consumption per tonne of reheated slab.
• More even slab temperature and less pronounced skid marks.
• Longer life for the skid and support structure through a lower thermal load.

Board Selection for Skid Insulation

Skid insulation runs close to the hot face, so it is specified in a higher grade and in blanket form. The blanket wraps tightly, and its low thermal conductivity means two 5 mm layers do the work of a far thicker ceramic-fibre wrap.

Property	Value
Form	Flexible microporous blanket / flexible sheet
Typical application	2 × 5 mm wraps over water-cooled pipes
Density	200-400 kg/m³
Thermal conductivity, 600 °C	0.028 W/m·K
Thermal conductivity, 800 °C	0.034 W/m·K

The blanket’s non-fibrous microporous core is cuttable on site, so skids of different diameters can be insulated with the same stock, trimmed to length as needed.

Recommended products for this application: flexible nano microporous sheet for the pipe wrap and standard boards for the furnace walls.

Frequently Asked Questions

Why two layers instead of one thicker wrap?

Two 5 mm layers wrap more cleanly around a curved pipe and let the installer stagger the seams, which closes the through-gaps that a single thick wrap can leave at the overlap.

Does the blanket survive the castable pour?

Yes. The wire fixing holds the blanket in place during castable application, and the castable then protects it from the furnace atmosphere. The blanket only has to keep its shape long enough to be encapsulated.

How quickly does the change pay back?

Because cooling-water heat loss is a large and constant load, reducing it by roughly a quarter typically repays the insulation cost within a single campaign. The secondary benefit — more even slab temperature and fewer mill-side skid-mark issues — often outweighs the energy saving on its own.

Does the blanket need a vapour barrier?

The blanket is encapsulated inside the castable, so it is protected from the furnace atmosphere. Where a hydrophobic grade is required for damp storage or a wet castable system, a water-repellent option is available on request.

Recover the heat your cooling water is carrying away. Ask our furnace engineers for a skid-insulation specification, or review our flexible sheet range for the right blanket. Contact us to get started.