1. The check valve installation position, height, directions to exit and entrance all should be agree with the design requirements, and also should pay attention to the addaccordance of flowing direction and that of valve Every connction should be firm.
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Check valve, a automatic working valve, can be classified into several categories that under different condition and purpose, the selection is different.
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The check valve can be classified into lift check valve, swing check valve, butterfly swing check valve, pipeling check valve, slow-closed check valve and diaphragm type check valve, etc. Belowing is a detail present of  the categories:
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There does exsit several structural featuers of butterfly valve, and the below article will express what are they.

1. Butterfly valve possesses the features of simple structure, small size, light weight,matrial economized, small installation size, speedy to switch, 90°reciprocated rotating, small drving torque. Used to cut, connect and adjust the medium in the pipeline, it is excellent to control the fluid and close sealing properties.

The disc of a butterfly valve is installed at the diameter direction of a lipeline, such as a stainless steel pipe. In the cylindrical channel of butterfly valve body, disc is rotated around the axes within a angle of 0°-90°, when 90°, the valve is full opening.

Butterfly valve is a widely used component, and of course, there must be several advantages of it, and some disadvantages. Below is a express of them.
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The relation between opening and flow of butterfly valve approximately presents a linear scale motion. If works to dominant discharge, there is a close relevance between diacharge characteristic and tube flow resistance, for example, even diameters and types of the two installed valve are all the same, there is a great difference of valve flow for different tube loss coefficient.  

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Stainless steel pipe is versatile in various industial fileds, below is a simple show of the applications:

In auto industry
Where there is a need of stainless steel pipe is the exhaust system, which covers over 1/2 of the whole stainless steel of the auto, among which 80% is ferritic stainless steel. In the exhaust system, the waste gas passes gas intake-tube, head tube, hose pipe, connutator, base pipe, and finally, fun off from silencer. The commonly used steel is 409L and 436L and silencer ofen mainly apply stainless steel welded pipe. According to estimating, stainless steel pipe used in the auto industry is 1.5% of that used in the final used, among which, the usage proportion of stainless steel seamless pipe and welded pipe is 2:1.
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Butterfly valve refers to a valve whose closure element is a disc which rounds with its shaft to control the valve's on and off to play a role of cutting and throttling on the pipeline, and it is also called flap valve which is simple structured regulating valve, and also be used as the on-off control of low pressure pipeling amboceptor.

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When contacting with oxygen mixed in the atmosphere, all metal will happen chemical reaction. What is worse is that there is a further oxidation on the ferric oxide which is oxygenized from general carbon steel to expand the corrosion constantly, and finally to form a corrosive hole. Peopel come up with a idea that we can utilize paint or galvanize the anti-oxide, however, as it known, this protection is just a thin film, when destroyed, corrosion of the under carbon steel is begin.

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