Pre-insulated pipes which may also be referred to as insulated pipes are pipelines extensively used in homes and factories to prevent freezing in water supply pipes and to reduce heat loss in heating ducts.
The main purpose of these pipes is to maintain the temperature of the liquid or gas in the pipes. Other reasons for using pre-insulated pipes are:
- limiting condensation
- Protecting personnel from extreme temperatures
- Minimising harmful emissions
The most common types are the single pre-insulated pipes, though the practice of insulating two pipes in one casing is picking up.
Parts of a Pre-insulated Pipe
A pre-insulated pipe usually comprises three parts. The carrier/conveyance pipe, an insulating layer of polyurethane (PUR) foam, and an outer protective casing.
It is used for carrying fluid within pre-insulated pipes. Suitable materials for making the carrier pipe are dependent on use. The materials are:
- Stainless steel
- Cast iron
- Poly vinyl (PVC)
- Fibre glass
- Polybutene (PB)
- Ductile iron
- Acid-resistant steel
- Galvanised steel
- High-density Polyethylene(PE 100)
- Polypropylene (PP)
- Extruded cross-linked polyethylene (PEX)
The casing prevents moisture from entering the insulation while also safeguarding the pipe against damage and corrosion.
The casing of underground pipes must be watertight, non-corrosive, resistant to salt and chemicals, hygienic and impact-proof. Some casings are UV-resistant due to the addition of anti-UV elements.
A suitable casing material is selected according to the environment the pre insulated pipe will be used in as shown below.
- Polyethylene(PEH) for underground installation or also for above-ground installation. When pipes are erected above-ground, cross-linked joints must be used.
- Steel-zinc coated or aluminium spiral overlaid sheet (Spiro casing) for above-ground installation
- Steel-zinc coated or aluminium spiral overlaid sheet coated with PVC foil to be used when pipes are put-up above-ground.
- Plastic-coated steel for demanding applications
PUR foam is used for insulating liquids or gases transported in pre-insulated pipes. Because of its unrivalled insulation qualities, this material preferred for pipe networks with temperatures ranging from -196 to +142°C.
For higher temperatures, pipes containing PUR with enhanced temperature resistance of up to 165°C are available. It is used in combination with mineral wool for temperatures above +250°C.
The main advantages of polyurethane are that it is pressure-resistant and retains its mechanical properties for more than 30 years.
Joints are used for the insulation of a pipeline in the welded areas where the carrier pipes interconnect.
The joints prevent moisture from breaching the PUR insulation while also protecting it from mechanical damage.
Types of joints
There are various joints according to their performance and application.
Weldable shrinkable joints
These joints are made using a computer-controlled thermoplastic welding procedure. Weldable joints are the most reliable solution for joining pre-insulated pipes. They are designed to remain watertight and durable while ensuring that heat loss is at an absolute minimum. They are suitable for the most demanding surroundings and sites with ground water.
Double-sealed shrinkable joints
These joints are the most common. They are appropriate for most applications. The pipe's PUR insulation is protected from moisture by an arrangement of two autonomous waterproof seals.
Cross-linked shrinkable joints
Cross-linked joints are made of PEX. They are made for an environment subjected to the strain of mechanical and thermal forces.
They can also be used in sites with ground water.
Uses of pre-insulated pipe systems
Pre-insulated pipe systems are used in petrochemical, chemical, pharmaceutical, and food industries to carry the following substances:
- Drinking water
- Cooling water
- Hot water
- Waste water
For more information, contact a business that knows about pipe systems.