Liquid nitrogen freezing and cutting device for medium-low pressure gas pipeline and using method of liquid nitrogen freezing and cutting device

Abstract

The invention discloses a liquid nitrogen freezing and cutting device for a medium-low pressure gas pipeline and a using method of the liquid nitrogen freezing and cutting device and belongs to the technical field of medium-low pressure gas transmission and distribution. The liquid nitrogen freezing and cutting device is mainly used in engineering occasions where a medium-low pressure gas transmission and distribution network needs to be quickly cut off under the conditions of no valve, failure of an existing valve and inconvenient operation of a glasses valve when a pipe network opening jointpipe is newly built and maintenance is needed. A quick freezing valve for the medium-low pressure gas pipeline comprises a hard pipe sight glass, a liquid nitrogen cooling system, a water spraying system, traversing assemblies and other components. Each traversing assembly adopts a two-stage sealing and air entrainment mode to realize small friction resistance lifting adjustment of the sight glass, a liquid nitrogen pipe and a water spraying head. The invention further provides a using method for a valve group. The liquid nitrogen freezing and cutting device and the using method have the beneficial effects that a valve-free gas pipeline can be quickly cut off on line, the safe and leakage-free cutting can be realized, the gas stopping range is small, the influence of large-area gas stopping on the production and life of gas users can be avoided, the cost of conventional valves and platforms can be greatly reduced with small replacement, the length and engineering quantity of a purgingpipe section can be reduced, and the construction period can be shortened.

Description

Technical field: [0001] The invention belongs to the technical field of medium and low pressure gas transmission and distribution, and in particular relates to a medium and low pressure gas pipeline liquid nitrogen freezing cut-off device and its use method. It is suitable for engineering occasions that need to cut off quickly, such as pipe network opening connection, maintenance, etc. Background technique: [0002] During the expansion, transformation and maintenance of a large number of medium and low pressure gas pipelines in cities and towns, due to valve failures, lax closures, and newly connected branch pipes, etc., it is often necessary to perform complex tasks such as large-scale gas shutdown, blind plate insertion, and purging; Moreover, enterprises, especially iron and steel complexes, also have gas pipeline networks that are rich in carbon monoxide and have large pipe diameters, such as blast furnace gas, converter gas, coke oven gas, and mixed gas. , poisoning a...

AI Technical Summary

Problems solved by technology

For conventional gate valves, butterfly valves and blind plates, there are the following main technical problems: medium and low pressure pipelines have large diameters, and when laying overhead, a large platform for valve installation, inspection and operation needs to be installed at the place where the valves are installed; No matter whether the valve is used or not, regular inspection and maintenance are required, otherwise it is easy to block, rust and cannot be operated; the valve is often difficult to open and close due to mechanical failure, or the valve is not closed tightly, and the blind plate needs to be inserted and removed during pipeline maintenance or connection construction, which is complicated. , and explosion casualties are prone to occur; when valve failures or long-distance main lines without valves need to add branch pipelines, the interface construction will cause a wide range of gas stoppages and high cleaning costs; it is necessary to operate glasses valves or insert blind plates , There is a large amount of air leakage in the ring flange gap, and accidents of poisoning and casualties of workers often occur

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