PUF pipes application in sewage systems
Insulation of sewage pipes with polyurethane foam is a highly efficient solution for pipelines buried on the level of soil freezing in the cold months. Using PUF pipes almost completely prevents the risk of wastewater freezing, resulting in formation of an “ice plug” and, consequently, pipe rupture.
Typically, HDPE (polyethylene) pipes are used for laying sewage systems, which are additionally insulated with a heat-saving layer of PUF. In the regions of the country where sub-zero mean annual temperatures are observed, it is preferable to used steel pipes in PUF insulation with a heating cable or tracer. In terms of design, these pipes consist of:
- Main pipe which the waste water flows through
- Tracer pipe or self-regulating heating cable designed to heat the main pipe
- Polyurethane foam layer acting as thermal insulation
- Polyethylene layer with the function to protect the complete inside structure from exposure to the environment.
Typically, the tracer pipe or heating cables are installed in a straight line along the entire length of the pipeline in operation. However, for improved heating results, they can be laid on the main pipe in the form of a spiral.
In regions where deep and continuous freezes are observed, GOST 30732-2020 prescribes to construct pipelines using pipes with type 2 insulation. As opposed to type 1 insulation, these pipes feature a thicker layer of polyurethane foam, hence the capability to withstand harsher climatic conditions.
Other materials used for thermal insulation of sewage pipelines
PUF is a material which has relatively recently become widely accepted and used in Russia. Earlier, mineral wool, plastic foam and foam polymer insulation were frequently used for the thermal insulation of sewage pipes.
Table of comparison of thermal insulation materials:
|
PUF | Mineral wool | Plastic foam | Foam rubber | Foam Polymer Insulation |
---|---|---|---|---|---|
Thermal conductivity | 0,033 W/(m·К) | 0,04 W/(m·К) | 0,038 W/(m·К) | 0,036 W/(m·К) | 0,047 W/(m·К) |
Density | 80-100 kg/m3 | 55 kg/m3 | 15 kg/m3 | 40-80 kg/m3 | 200-250 kg/m3 |
Service life | > 30 years | > 30 years | > 30 years | 10-20 years | > 30 years |
Strength | 0,3 MPa | 0,1-0,15 MPa | 0,2-0.4 MPa | - | 0,3 MPa |
Material structure | Closed pores | Layered | Honeycomb | Porous | Closed pores |
Heat resistance | Moderately flammable | Practically inflammable | Moderately flammable | Weakly flammable | Strongly flammable |
Water absorption | None | Up to 30% | 1% | 2,4% | 7% |
Adhesion to pipe | At least 0.12 | None | None | None | 0,4 |
Environmental friendliness | High | Medium | Releases toxins when burning | High | High |
RRCS | Yes | No | No | No | No |
In terms of performance, PUF is miles ahead of its competitors, because it offers:
- Long service life
- Possibility of using the pipeline even under very cold climatic conditions
- Relatively low weight and ease of installation of sewage pipes
- Resistance to mechanical loads
- Immunity to aggressive alkaline and acidic media
- Excellent adhesion (bonding force between the polyurethane foam and the pipe)
- Absence of water absorption and, consequently, pipe corrosion.
At the moment, application of PUF sewage pipes is economically feasible both in the household and industrial field. Moreover, pipelines in polyurethane foam insulation are successfully used both in the oil and gas industry, and in construction of heating mains, minimizing heat losses and ensuring a long service life.
At the moment, application of PUF sewage pipes is economically feasible both in the household and industrial field. Moreover, pipelines in polyurethane foam insulation are successfully used both in the oil and gas industry, and in construction of heating mains, minimizing heat losses and ensuring a long service life.