In recent years, steel-jacketed steam insulation pipe laying has been more and more applied in heating engineering. With the development of heating scale, strict requirements are put forward for cost control and heat loss reduction of directly buried steam insulation pipe. The thermal insulation structure of steel-jacketed insulating pipe is directly related to temperature drop, heat dissipation loss and project cost. The common insulation materials include aerogel insulation felt, ultra-fine glass wool felt, aluminum silicate needle felt and calcium silicate tile.
(1) aerogel insulation blanket + superfine glass wool felt and air layer composite insulation structure.
This structure is an external sliding type. The design idea of this insulation structure is from the thermal pipe trench. A bracket is set up in the outer protective pipe, which causes the sliding between the working steel pipe and its corresponding insulation material and the outer protective pipe (i.e. the external sliding) and forms the structure of "steel pipe trench". The characteristics of this thermal insulation structure are that the working steel pipe is in close contact with the thermal insulation material, and the working steel pipe is supported in the outer protective pipe by the support, so that the support slides in the inner part of the outer protective pipe. The 20 mm air layer in the thermal insulation structure not only plays the role of thermal insulation, but also is a good channel for tidal discharge.
(2) (Aluminum silicate needle-punched blanket +) superfine glass cotton felt + air layer composite insulation structure
This structure is also an outer sliding type. It only changes the composite insulation structure of aerogel insulation blanket and ultra-fine glass wool felt compound into the single layer ultra-fine glass wool felt (or aluminum silicate needle blanket + glass cotton) in the first structure. With the first structure, because the thermal conductivity of the ultra-fine glass felt is larger than that of the aerogel insulation blanket, the thickness of the insulation layer and the outer diameter of the outer guard tube are larger than that of the first structure.
(3) Microporous Calcium Silicate+Polyurethane Composite Insulation Structure
The steel-sleeved steam insulation pipe is of internal sliding type, and its structural design idea comes from hot water prefabricated insulation pipe. Generally, there is a resistance-reducing layer with a thickness of 5 mm between the outer surface of the working steel pipe and the inner layer of the insulation structure, which is firmly integrated with the working steel pipe. Its material is aluminium silicate felt with high temperature resistance, and the inner layer of the insulation structure is aluminium silicate felt with high temperature resistance. Microporous calcium silicate with high temperature resistance and polyurethane outer layer. The characteristics of this insulation structure are: sliding between the working steel pipe and the inner micro-porous calcium silicate (i.e. internal sliding), and bonding between the micro-porous calcium silicate and the outer tube with polyurethane material. The disadvantage of this structure is that the micro-porous calcium silicate bears the load of the working steel pipe.