Removable Insulation

What sets removable insulation apart

Fixed lagging - mineral wool under a sheet metal casing - works well on straight runs of exhaust or steam pipe that are rarely disturbed. It works badly on flanges, valve bodies, expansion joints, turbocharger housings and anything else that needs to come apart for inspection or repair, because cutting and rebuilding metal casing every time adds hours to a job that should take minutes. A removable jacket solves this: a tailored blanket of insulation material stitched into a fire-resistant outer cover, closed with hook-and-loop straps, buckles or lacing, that lifts off in one piece and goes back on the same way. The insulating performance is close to fixed lagging when the jacket is properly fitted and sealed at its edges; the advantage is entirely in maintainability.

Main components

• Inner insulation layer, typically needled mineral wool or ceramic fibre blanket chosen for the surface temperature, compressed and quilted to hold its shape
• Outer cover, a woven silica or glass fabric for high-temperature exhaust duty, or a coated glass cloth for lower-temperature steam and process lines
• Closure system - stainless hook-and-loop straps, lacing cord through grommets, or quick-release buckles, sized so the jacket can be refitted by one person
• Shaped panels or gussets cut to the specific flange, valve or elbow geometry, since a generic wrap leaves gaps at odd-shaped fittings
• Thermocouple pockets or a small removable flap on some jackets, allowing a surface temperature check without lifting the whole cover

Selection and sizing

The controlling figure is surface temperature at the specific fitting, since that sets both the insulation material grade and the outer cover fabric. Exhaust manifold and turbocharger jackets commonly need to hold surface temperature at or below the touch limit against gas temperatures well above 400 degrees C, while steam line jackets deal with lower absolute temperatures but longer continuous exposure. Jackets are normally made to a template or measurement taken from the actual fitting rather than ordered from a size chart, because flange bolt patterns and valve body shapes vary enough between manufacturers that an off-the-shelf fit rarely seals properly at the edges.

Regulations and class

SOLAS Ch. II-2 sets the underlying requirement that exhaust pipes and other surfaces which oil could contact must be insulated or shielded to keep exposed surface temperature below the ignition point of oil that might spray or leak onto them - this is the rule that removable jackets on exhaust manifolds and turbocharger casings exist to satisfy. Class surveyors check for insulation that is missing, saturated with oil, or removed and not refitted after maintenance, particularly around the exhaust system and any hot surface within reach of a fuel or lube oil line.