Insulation After Thermite Welding
Pipeline can be insulated both manually or with special devices which provide appropriate integrity and thickness of the insulation layer in accordance with the project requirements. Benches, sleeves, latches and T-joints should be manually insulated.
Insulation covers, their designs and types
- Pipelines with the diameter of more than 820 mm and the temperature of the transported product of more than 40°С are insulated with asphalt mastic based coatings. The same coatings are also used to insulate the pipelines with the diameter of up to 1,020 mm at the ambient temperature of max. 25 °С.
- Insulation coatings based on the polymer tapes are used to insulate the pipelines with any diameter. Polymer tapes are used at the temperature of carried product of up to 60 °С, while in case the temperature of up to 35 °С polyvinyl chloride tapes are applied.
- Polyvinyl chloride tapes can withstand quite significant pressure. They are highly durable, heat resistant, have good adhesive, sealing properties and are quite elastic, thus they can be used both inside and outside. These tapes are widely spread in households, during repairs and construction to insulate the cables, in assembly.
- Cotton insulation tape is a cotton-based rubber-coated sticky tape. It is more heat resistant in comparison with polyvinyl chloride tape and withstands more than 100 °С, but it is not moisture resistant.
- The defects in the factory polyethylene-based and heat shrink tape-based coatings are repaired with hot-melt repairing filler and a heat shrink armored tape-patch.
Factory insulated pipelines are recommended to be used for the pipelines of any diameter with polyethylene coating at the temperature of transported product of max 60 °С, and in case of the products with epoxy resin-based insulation it is 80 °С.
The crossings under the highways and railway roads, at the places where the main pipeline is exposed it is necessary to strengthen the facility with a
rubber neck gasket and insulation tape.
Water tight rubber neck gasket is mounted at the crossings under the buildings, utilities, highways and railway roads. Visually it is a truncated cone.
When installed, it seals the distance between the casing and the carrier pipe of 108 -- 1,420 mm in diameter of the main pipeline. In this case temperature regime is of critical importance - from −60 to +50 °C. A neck gasket can be of two types:
-
- a separable gasket is used for the operating water utilities;
- an inseparable one is for the utilities being under construction, under turnaround maintenance, when a pipeline part should be replaced.
A
cone-shaped rubber neck gasket is fixed with metallic clamps to seal the space between the carrier pipe and the casing.
Different climates require different gaskets:
- for moderate climate;
- for cold climate.
protective cover of water tight neck gasket
-
is used to protect the insulation from deformation during the maintenance, from soil pressure and mechanical damages. The cover can also protect the pipeline from ultraviolet attacks, incidental opening, it gives enough space for the pipeline deformation at temperature changes in seasons and/or in a transported product. This cover can also be used in different climatic conditions. It does not change its properties from −60 to +60 °С.
Cover of the rubber neck gasket is manufactured from fiber glass and can be of three types depending on a particular purpose:
- U-PMTD-S protects a cone rubber neck gasket PMTD;
- U-PMTD-S-OKS with the holes for telecommunication cables protects PMTD-OKS gaskets;
- U-PMTD-SK protects rubber gofferred neck gaskets PMTD-GP.
Welding joints of isolation valves with a pipeline must be insulated with coatings with the protective properties matching the properties of the main insulation coating of the pipeline.
Insulation works should be performed with the materials in accordance with the regulatory documents stated in a project. The choice of the insulation materials should be based on the ambient temperature during the works, maximum temperature of the transported substance, required service life.
Effectiveness of the protective and insulation materials depends on many factors. Insulation coatings should work under absolutely different temperature conditions of construction and pipeline maintenance and reliably protect the pipelines against corrosion for a long service life.
Back to the list of articles