Polyurethane (PU) foam (Details and specifications for Polyurethane foam)
Polyurethane foam is a low density rigid insulating foam. It comprises of a 90% closed cell formation, thus drastically reducing the chances of water absorption or transmission. Polyurethane has tremendous flexural and compression abilities, and can support up to 25 times its own weight relative to water. It has exceptional thermal properties and boasts a k value of between 0.018-0.023 W/mk.
When polyurethane foam in its liquid form comes into contact with foreign surfaces, it forms a moisture impenetrable silicone vapour barrier, thus giving a dual vapour barrier i.e. on the outer surface of the pipe, and on the inner surface of the metal cladding. BKV Thermal (Pty) Ltd utilises high pressure proportioning units in order to inject or spray the Polyurethane as per requirements.
Foam injection Procedure
The cladding is installed and secured to the vessel, piping and components using preformed foam spacer blocks. Once all the piping and components have been encapsulated, foam is then pumped into the enclosed space at high pressure with a proportioning unit to insure impingent mixed foam. The agitated mixture then has a rising time of +/- 27 seconds and a gel/setting time of +/- 10 minutes.
Polyurethane foam being injected around a NH3 Vessel
Foam Spraying Procedure
Polyurethane foam is sprayed onto the required surface by means of a high pressure proportioning unit. A two pass system is used, in order to build up a 25mm layer of low density, rigid Polyurethane. The agitated mixture then has a rising time of 7 seconds and a gel/setting time of +/- 10 minutes.
When polyurethane foam in its liquid form comes into contact with foreign surfaces and air, it forms a moisture impenetrable silicone vapour barrier, thus giving a dual vapour barrier i.e. on the outer metal surface of the component, and on the surface exposed to the atmosphere. After the foam has set, a protective coating is applied to a colour prescribed by the customer.
A IBR roof insulated using Polyurethane Foam
Advantages and Characteristics of PU Foam
- Any circumferential and longitudinal joints are eradicated due to a continuous layer of insulation, thus not permitting any moisture transmission.
- Injected Polyurethane is light, very rigid and has a density of between 35kg/m³ and 60kg/m³
- Dual silicone vapour barrier on the external pipe surface, and the internal metal cladding surface.
- Installation time is reduced and the foam has a curing time of +/- 10 minutes.
- Injected polyurethane has normal life span of up to 40 years under working conditions.
- Has a 90 % closed cell formation.
- Has a thermal conductivity of between 0.018 W/mK to 0.023 W/mK
- Excellent acoustic and vibration resistant properties.
- Resistant to most chemicals, particularly hydrocarbons and solvents.
Specifications (Details and specifications for Polyurethane foam)
| Injected Polyurethane Foam | Sprayed Polyurethane foam | |
Density (kg/m³) |
60 | 35 |
| Compressive Strength (kPa) | ||
| Parallel to rise Perpendicular to rise |
250 170 |
225 150 |
| Thermal conductivity @ 10ºC (W/mk) | 0.023 | 0.023 |
| Water absorption (%) | 5 | 5 |
| Temperature Range (ºC) | -180ºC to +140ºC | -180ºC to +140ºC |
Complete NH3 Plant, done in 1200h04 Aluminium
Foam Proportioning unit
NH3 Plant and H2O Tank done in 1200h04
Various pumps and tank, done in 1200h04