What rock wool is used for: an application guide for industrial plant

Rock wool is used to insulate the hot side of industrial plant: steam and process pipework, vessels and tanks, ducts and air handling, boilers, kiln and furnace exteriors, smelting process piping and engine exhaust runs. On those jobs it is fitted as a wire-mesh stitched blanket cut from a roll, wrapped onto the surface and clad in metal sheet.

What separates one application from the next is the hot face: the temperature of the outside of the pipe, vessel, duct or casing the blanket sits on. Vulcanite Armor comes in three grades, each with its own published figure, so the job is to match the application to the grade whose figure clears it.

Grade	Hot-surface performance (ASTM C411 / C447)	Hot-face band it is listed for
Blanket 80, 80 kg/m³	650°C	At or below 650°C
Blanket 100, 100 kg/m³	700°C	650°C to 700°C
Blanket 120, 120 kg/m³	750°C	700°C to 750°C

The range is rated up to 750°C. That figure belongs to Blanket 120 alone. Above it, the job moves to ProTherm ceramic fibre blanket, working temperature 1050°C.

Rock wool uses at a glance: application, hot face and grade

Each grade carries its own published application list. The table below sets those lists against each other, so you can find your application and read across to the grade that names it.

Application	Where the temperature figure comes from	Grade whose published list names it
Steam pipes	Steam tables, then the measured hot face	Blanket 120
Boilers	Measured casing hot face	Blanket 120
Kiln and furnace exteriors	Measured casing hot face	Blanket 120
Smelting process piping	Measured hot face	Blanket 120
Any pipe, vessel or duct at 700°C to 750°C	Measured hot face	Blanket 120
Petrochemical and power-station process piping, vessels and ducts at 650°C to 700°C	Measured hot face	Blanket 100
Large-diameter piping, ducts and vessels at or below 650°C	Measured hot face	Blanket 80
HVAC and process ducting, air handling	Measured hot face	Blanket 80
Storage vessels and tanks	Measured hot face	Blanket 80
Lower-temperature process piping	Measured hot face	Blanket 80

Two rules sit behind the table. A grade rated higher than your hot face will also carry the job, so the list is a starting point and the measured temperature is what confirms it. And any surface above 750°C is off the table for rock wool altogether.

The sections below take each application in turn: what the temperature is driven by, which grade the published data points to, and what to check before you order.

Steam and process pipework

Steam lines

Steam pipes are named on the Blanket 120 list. Steam is also the one application where a published curve fixes the temperature inside the pipe, because saturated steam has a single temperature at each pressure. The US Department of Energy tabulates uninsulated steam line losses at 15, 150, 300 and 600 psig. Read off the NIST saturation curve, those pressures sit at roughly 121°C, 185°C, 217°C and 254°C. The conversion is ours, not DOE’s.

Saturated steam in that range sits below the rating of all three grades. Superheated steam does not follow the curve and runs hotter. So a steam line is confirmed against its measured hot face, not against the word steam: Blanket 120 is the grade whose list names it, and a line well inside 650°C is also within the published rating of Blanket 80 and Blanket 100.

Process piping on petrochemical and power plant

General petrochemical and power-station process piping, vessels and ducts with a hot face between 650°C and 700°C are the published application for Blanket 100. Its product data also names it as the grade to consider where one grade has to cover mixed piping and vessel work across a plant, for example a shutdown, where one stock of rolls goes onto many different lines.

Lower-temperature process piping is named on the Blanket 80 list, rated to 650°C.

Smelting process piping

Smelting process piping is named on the Blanket 120 list. On mines and smelters the same rule applies as everywhere else: measure the hottest reachable point on the run, then check it against 750°C. Above that figure the blanket is the wrong class, whatever the plant.

Stainless steel lines

On austenitic stainless pipework the insulation is a chloride question as well as a temperature one. Vulcanite Armor publishes chloride ion content of 5 ppm or less, and the datasheet states that it conforms to the stainless steel corrosion specification as per ASTM C692 and C871 test method. That applies to all three grades. Why the figure matters, and how water at the metal turns it into a cracking risk, is in corrosion under insulation and chloride on stainless steel.

The pipework case, with prices per roll beside each grade, is laid out on the rock wool pipe insulation page.

Vessels, tanks and columns

Storage vessels and tanks are named on the Blanket 80 list, and so are large-diameter piping, ducts and vessels with a hot face at or below 650°C. Petrochemical and power-station vessels between 650°C and 700°C move to Blanket 100.

No generic temperature is published for a storage tank, process vessel or distillation column, so this is one application where the measured hot face is the only figure you have. Take it at the hottest point you can reach, and record where it was taken.

The form of the product suits the shape. A column with nozzles, manways, saddles and a dished head has almost no flat area, and preformed sections exist only for standard pipe diameters. A mesh-stitched blanket is cut to the girth on site and pulled round the change in section, and the mesh holds it until the cladding goes on. Joints at a nozzle or a manway are cut and wired rather than ordered.

Ducts, air handling and plant rooms

HVAC and process ducting and air handling are named on the Blanket 80 list, rated to 650°C. Duct and plenum casing is mostly flat, so roll width sets the joint count: the 1200 mm roll covers the same casing in fewer longitudinal joints than a narrower one.

Ducting is not a single temperature, and the standards that cover it do not print one. BS 5970:2012, the code of practice for industrial thermal insulation from -100°C to +870°C, groups ductwork with pipework and plant and leaves the number to the designer. A hot process duct between 700°C and 750°C falls under Blanket 120’s list (“any pipe, vessel or duct”), not Blanket 80’s.

Where a plant room is lined for noise rather than heat, that case is covered under fire and acoustic duty below.

Boilers, flues, kilns and furnace exteriors

Boiler casings and flue work

Boilers are named on the Blanket 120 list. DOE publishes stack gas temperatures of 350 to 550°F, about 177 to 288°C, for a boiler at 4% excess oxygen, falling to 250 to 300°F, about 121 to 149°C, with an economiser fitted. Those are flue gas temperatures inside the breeching. No generic figure is published for the outside of a boiler casing, so the casing is measured like everything else.

One boundary on a boiler is easy to miss. Boiler insulation and boiler doors appear on the ProTherm ceramic fibre list, not on any rock wool list. The casing is on the rock wool list; the doors are on the ceramic fibre list.

Kiln and furnace exteriors

Kiln and furnace exteriors are named on the Blanket 120 list. The word that matters is exterior: the outer casing, behind the refractory. Furnace linings, furnace door linings and seals, reheating furnace and ladle covers sit on the hot side of the refractory and are on the ProTherm list instead, at a working temperature of 1050°C.

Engine and generator exhaust runs

The EPA Catalog of CHP Technologies records exhaust temperatures of 720 to 1000°F, about 382 to 538°C, for its example reciprocating engine systems. Those are exhaust gas temperatures at the engine, not skin temperatures on the run, and the published range for those examples spans more than 150°C. That spread is why the grade is selected against the measured hot face and not against the type of engine.

Measure the run at its hottest reachable point. Up to 650°C is within Blanket 80’s rating, 650°C to 700°C takes Blanket 100, and 700°C to 750°C takes Blanket 120. Reusable turbine covers are on the ProTherm list, not the rock wool one.

On a generator set the exhaust is often inside an enclosure that is also lined for noise. The lining and the exhaust are two separate surfaces, and the lining is covered in rock wool for sound insulation.

Fire and acoustic duty: what the data supports

Fire

Vulcanite Armor publishes a Flame Spread Index of 0 and Smoke Developed 20, tested per ASTM E84, Standard Test Method for Surface Burning Characteristics of Building Materials, on all three grades. The datasheet’s own wording is that the product holds ISO, CE and A1 certification approval.

That is reaction-to-fire data for a material. A fire-resistance rating belongs to a tested assembly rather than to a roll of insulation, and none of the figures above is one. Where a fire-resistance rating is in the specification, the assembly test report is the document to ask for.

Acoustic

The datasheet describes the blanket as suitable for thermal and acoustic insulation. No acoustic figure is published for the range, so none is given here. Where noise is part of the job, on a generator enclosure, a compressor house or a plant-room wall, rock wool for sound insulation sets out what a porous blanket does inside an assembly and what it does not do on its own.

What rock wool is not used for

Knowing where the blanket stops saves an order that comes back.

Hot faces above 750°C. Furnace and kiln linings, heat-treatment furnaces, ladle covers, boiler doors facing the fire and glass furnace crowns are ceramic fibre jobs. ProTherm ceramic fibre blanket is aluminium silicate at 96 kg/m³, working temperature 1050°C. Its classification temperature, 1260°C, is not a use temperature: specify against 1050°C. The 1450°C figure sometimes quoted for rock wool is the melt temperature of the rock in manufacture, explained in what rock wool is made of, and is not a rating of any kind.

Geyser and household water pipes. Search for pipe lagging in South Africa and the results are foam lagging for geyser and household water pipes, sold through plumbing suppliers. That is a different product. Vulcanite Armor is sold by the roll, cut on site and clad in metal, for industrial pipework; it is not made as a slip-on sleeve in household pipe sizes.

Lofts, ceilings and stud walls. Building fabric is usually insulated with rolls, batts and slabs sized for the cavity. A wire-mesh stitched blanket is the wrong form for that work. How glass wool and rock wool divide the building and industrial markets is in rock wool vs glass wool vs ceramic fibre.

Cold and below-ambient lines. On below-ambient lines the deciding question is condensation and vapour drive, not hot-surface performance. The same comparison post covers which classes are specified there.

Load-bearing points and preformed parts. Vulcanite supplies the blanket only: no pipe sections, boards or loose wool. Where a specification calls for a rigid insert under a support shoe, that part comes from a rigid class.

Ordering for an application

Three figures turn an application into an order: the measured hot-face temperature, the pipe diameter or casing dimensions, and the duty that sets thickness. Thickness is not read off an application list. It is calculated from the line conditions under ASTM C680, and the four duties that set it (process control, personnel protection, condensation control and energy savings) are worked through in choosing rock wool density and thickness.

For mixed work across a plant, Blanket 100 is the grade whose data names that case. For a single application, take the lowest grade whose rating clears the measured hot face, and cost the options against each other on the price list, where every grade, thickness and roll size is priced per roll.

Vulcanite Armor is imported and supplied in South Africa from Centurion. Who we supply, and how to buy online or on a project quote, is on the rock wool supplier page. The published figures for all three grades are on the Vulcanite Armor datasheet.

If you have the application, the measured hot face and the dimensions, get a quote and we will confirm the grade and a thickness band.