How to Insulate Hot Pipes with ROCKWOOL Mineral Wool

When comparing both insulation systems with equal heat loss, use the table below to compare insulation thicknesses under these conditions:

• Average temperature: 250°C
• Ambient temperature: 10°C
• Wind speed: 5 meters/second
• Jacket: Aluzinc
• Heat loss rate: 150 watts/meter
• Spacer installation required for wire mesh insulation system

Typically, pre-formed mineral wool insulation is more suitable for straight pipes as it doesn’t require spacer installation, allowing faster work. For flanges or elbows, wire mesh types are necessary as they can be easily cut to shape. Here’s a table for recommended insulation selection:

The table below helps design insulation thickness to prevent hazards from pipe surface contact, with these example conditions:

• Ambient temperature: 25°C
• Wind speed: 0 meters/second
• Jacket: Galvanized sheet
• Maximum surface temperature: 60°C
• Insulation used: ProRox PS960

Installation

ROCKWOOL ProRox PS960 mineral wool comes as hollow tubes with inner diameters matching steel pipe sizes and layered thicknesses, fitting perfectly when slipped onto steel pipes.

• For horizontal pipes, we rotate the insulation split beneath the pipe to prevent rainwater from dripping through the split to the steel pipe.
• For vertical pipes, we offset the insulation gaps by about 30 degrees to prevent water droplets from flowing through splits to the steel pipe.
• After installing insulation, we secure it with galvanized wire or metal straps.
• Pipe insulation thicker than 120 mm (or for temperatures above 300°C) requires 2 or 3 layers of insulation. The splits must be staggered to prevent water penetration to the inner pipe surface.

Typically, pre-formed pipe section systems don’t need spacers and pipe supports. However, for pipes with significant vibration and/or temperatures above 300°C, spacer installation may be necessary.

For vertical pipes taller than 4 meters, pipe supports lock insulation to the pipe. We install the first support ring at the pipe’s lowest point, with subsequent rings spaced no more than 4 meters apart.

The table below helps design insulation thickness to prevent hazards from pipe surface contact, with these conditions:

• Ambient temperature: 25°C
• Wind speed: 0 meters/second
• Jacket: Galvanized sheet
• Maximum surface temperature: 60°C
• Insulation used: ProRox WM950

Installation

• Cut mineral wool insulation to length that wraps around pipe completely
• Pull wire mesh of mineral wool tight and secure with 0.5 mm metal wire
• Stainless steel pipes and pipes above 400°C use wire stitching to prevent wire tearing and rust
• For insulation thicker than 120 mm or temperatures above 300°C, multiple insulation layers are needed. Split joints must not align to prevent water penetration to inner pipe surface.

Wire mesh type insulation is not compression-resistant, so cladding cannot be installed directly on the insulation. Spacers or pipe supports must be installed before cladding.

For vertical pipes taller than 4 meters, pipe supports lock insulation to the pipe. We install the first support ring at the pipe’s lowest point, with subsequent rings spaced no more than 4 meters apart.

Spacers are installed to support cladding weight installed after insulation. Spacers are necessary with wire mesh mineral wool but not with pre-formed pipe sections.

The pipe structure includes an outer metal ring against the cladding, followed by metal or ceramic spacers installed on the pipe, such as Omega Clamps commonly used for vibration reduction.

• Metal spacers require at least 3 pieces with spacing not exceeding 16 inches (400 mm) when measured against the outer metal ring.
• Ceramic spacers require at least 4 pieces with spacing not exceeding 10 inches (250 mm) when measured against the outer metal ring.

The number of spacers depends on operating temperature and external forces. Spacer spacing can be referenced from CINI 1.3.23.

For pipe bend spacer installation, such as elbows, install at bend start and end. If spacer spacing exceeds 27 inches (700 mm) when measured at the outer bend line, additional spacers must be installed.

We install pipe supports for vertical pipes because they carry significant weight from pipe, insulation, and cladding, and experience more vibration than horizontal pipes. Support selection depends on pipe size and temperature, using screws, welding, or double clamps for high-temperature pipes. Supports must be made from high-temperature resistant metal.

Cladding protects thermal insulation from weather and other environmental pollutants. Material selection depends on factors like pipe vibration, maintenance foot traffic, weather, and ambient temperature.

We select cladding materials as follows:

1. Galvanized sheets for indoor use due to good strength and fire resistance
2. Aluminum sheets for outdoor use due to good weather resistance and lower cost than stainless steel

For corrosive areas, aluminum sheets, stainless steel sheets, or reinforced plastic sheets are used for cladding, with stainless steel recommended in potentially flammable environments.

Basic Guidelines

• Secure longitudinal joints with self-drilling screws or rivets every 1 meter
• Do not use aluminum screws

Increased insulation thickness, insulation thermal conductivity, and environment – surface temperature depends on cladding heat emission

For general thermal insulation applications, the more reflective the surface, the higher the surface temperature. Below is a comparison of surface temperatures for different cladding materials:

• Pipe diameter: 4″ NPS (114 mm)
• Internal temperature: 500°C
• Location: Indoor
• Wind speed: 0.5 meters/second
• Mineral wool: ProRox WM950
• Cladding materials:

1. 1. Aluminum sheet
   2. Galvanized steel sheet
   3. Stainless steel sheet
   4. Plastic-coated color sheet

There are various types of pipe hangers and supports, illustrated below:

• • Direct-mount pipe hangers
  • Direct-mount pipe supports
  • Indirect-mount pipe supports (typically used in cold insulation)

Heat loss occurs at uninsulated joints or flanges. We can roughly estimate that a valve loses heat equivalent to 1 meter of uninsulated straight pipe.

Without insulation at valves or flanges, internal material temperature drops, reducing system efficiency. Valves and flanges should be insulated with at least the same thickness as pipe insulation.

Guidelines for Thermal Insulation of Joints and Flanges

Joint or flange insulation should overlap straight pipe insulation by about 50 mm

Elbow or T-piece cladding is easily damaged from pipe vibration or expansion, and must resist moisture and vapor when installed outdoors.

We cut pre-formed pipe section insulation to match elbow curves

We cut wire mesh mineral wool into a fish-shaped elbow pattern for perfect fit against the elbow, then secure wire mesh with wire or ties. Install spacers at start and end points of elbow.

In insulation systems, pipe and cladding expansion can differ significantly. Uneven expansion results from different materials, thermal insulation, and temperatures causing different expansion coefficients.

We use Al as the symbol for longitudinal expansion

Δl = l * Δt * α

l = pipe length
Δt = temperature difference between hot and cold pipe (or cladding)
α = longitudinal expansion coefficient

Avoid walking on insulated pipes as this can damage insulation, such as creating gaps in cladding joints that allow moisture to reach pipes and cause rust.

In limited space where maintenance requires pipe walking, use ProRox PS970 pre-formed pipe sections that resist both cladding weight and foot traffic compression. For wire mesh insulated pipes, cladding must be installed on pipe support brackets to handle walking weight and cladding weight.