Polyurethane insulation pipe plays an important role in many important fields, such as aerospace, heating system, central air conditioning, chemical industry and petroleum, etc., so the construction of polyurethane insulation pipe has been widely concerned, and any detail may cause construction failure. And in the real construction, different construction methods are selected for different site environment, different construction methods have different characteristics, and the details to be paid attention to are also different. Let's take a look at the construction process of polyurethane insulation pipe, which are the issues to be paid special attention to:
Details to be paid attention to in the project:
First, after entering the site, the staff must carefully carry out inspection, which is very important for the relevant inspection procedures before construction. Any unqualified equipment, heat preservation pipes and raw materials are rejected.
Second, in the construction and welding of polyurethane insulation pipe, it is also the key to the quality of the whole project. So we must pay more attention to the fixing of supports, welding of pipes and other procedures. It should be known that these two steps directly affect the quality and effect of the whole insulation project in the later stage, and also directly determine the service life of the whole pipeline.
Third, in order to meet the pressure standard, we should pay attention to the pipe pressure. This step should be divided into two parts. First, the pressure can be adjusted if there is no leakage within 10% of the stabilized pressure. Then use a small hammer conforming to the standard weight to knock around the weld to check whether there is leakage. Finally, adjust the pressure in the polyurethane insulation pipe to the working pressure range. If there is no leakage in about half an hour, then it is qualified.
Fourth, it is necessary to know that such polyurethane insulation pipe construction is directly laid underground, usually such projects are concealed works. If there is a slightest carelessness or careless completion acceptance in the process of construction or inspection, there may be frequent faults or other phenomena in the future use and operation process. Even after the construction of polyurethane insulation pipe is completed, relevant units need to send special personnel to carry out strict and serious acceptance inspection.
Fifth, no matter which polyurethane insulation pipe construction method is selected, attention should be paid to the quality of the pipe and the situation of no cracking and delamination. The most important thing is to ensure that the joint of the pipeline has the waterproof, tightness and integrity as required.
Because of the different materials of the heat preservation pipes, pipe fittings and joints produced by different manufacturers, the melt flow rate of the materials will be different. If the melt flow rate value of the outer sheath at the joint does not match with that of the outer sheath of the adjacent straight pipe or pipe fitting, the welding quality will be affected and the sealing performance of the outer sheath of the joint will be affected. Therefore, heat preservation pipes, pipe fittings and joints of the same manufacturer shall be used as far as possible. When the working pipe is made of different materials and wall thicknesses, local stress concentration will occur, which needs to be checked by design.
During winter construction, due to the low ambient temperature, the quality of interface insulation and foaming will be affected, so winter construction should be avoided as far as possible. If it can't be avoided, the working steel pipe, the surface of outer protective pipe and foaming raw material shall be heated before foaming.
If the wetted insulation material is not removed, during the high temperature operation of the pipe network, the water remaining in the insulation layer will vaporize due to the increase of the pipe network temperature, which will cause the carbonization of the insulation layer and destroy the sealing of the outer protective layer of the joint.
The overlapping length between the outer protective layer and the outer protective tube of the insulation tube on both sides shall not be less than 100mm to ensure the strength and sealing of the outer protective layer of the joint. Especially for the hot-melt welding joint, the fusion welding area of the outer protective layer shall be completely overlapped with the outer protective tube of the insulating tube to ensure the fusion welding quality and tightness.
The joint quality has a crucial influence on the overall quality and service life of the pipe network. If the sealing at the joint cannot be guaranteed, when the water enters the joint, the high temperature operation will lead to the carbonization failure of polyurethane insulation materials, damage the integral structure of the prefabricated directly buried insulation pipe system, and lead to the failure of the whole pipe network system. Therefore, 100% air tightness test must be carried out at the joint.
