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目前在國內(nèi)外均已采用一種結(jié)構(gòu)的管道連接方式，即卡套式管接頭連接方法。國家標(biāo)準(zhǔn)局于1983年頒布了全國通用的卡套式連接標(biāo)準(zhǔn)?？ㄌ资竭B接的類型很多，如擠壓式、撐脹式、自撐式、噬合式等。根據(jù)標(biāo)準(zhǔn)局頒發(fā)的標(biāo)準(zhǔn)，我國卡套式連接屬于擠壓式和噬合式，其結(jié)構(gòu)由接頭體、卡套及螺母三個零件組成。其中的關(guān)鍵零件是卡套—一個帶有切割刃口的金屬環(huán)（室內(nèi)熱水采暖用的卡套為橡膠卡套）。
經(jīng)過對國內(nèi)卡套式管接頭進(jìn)行研究發(fā)現(xiàn)，國產(chǎn)卡套式管接頭存在以下幾方面的缺陷。
1.卡套式管接頭標(biāo)準(zhǔn)陳舊
我國現(xiàn)行的卡套式管接頭標(biāo)準(zhǔn)依舊是十多年前實(shí)行的標(biāo)準(zhǔn)，在近幾年來并沒有依據(jù)使用的需求對其進(jìn)行研究與改進(jìn)。國外的卡套式管接頭已經(jīng)經(jīng)過了多次的更新?lián)Q代，而我國國產(chǎn)的卡套式管接頭始終停留在某一個標(biāo)準(zhǔn)上，遠(yuǎn)遠(yuǎn)地落后于國外卡套式管接頭的發(fā)展水平。
2.就國內(nèi)標(biāo)準(zhǔn)而言依舊存在缺陷
雖然我國國內(nèi)的卡套式管接頭標(biāo)準(zhǔn)較為陳舊與落后，但是相對于國內(nèi)的這種標(biāo)準(zhǔn)而言，依舊存在著低于標(biāo)準(zhǔn)、存在缺點(diǎn)的問題，例如接頭系列不完全、壓力級別較低等，不能夠?qū)Ω鞣N復(fù)雜的高壓使用場合進(jìn)行應(yīng)付。
3.缺乏國際變徑接頭
當(dāng)前國產(chǎn)卡套式管接頭中沒有國際變徑接頭，雖然有行標(biāo)變徑接頭，但是這類接頭在材料、熱處理等方面存在問題，導(dǎo)致了結(jié)構(gòu)不能夠承受高壓。同樣的原因，B型扣壓式膠管接頭（與卡套式管接頭配套使用）也不能夠在加氣站中使用。
4.不合格品比例較高
在國際規(guī)定的標(biāo)準(zhǔn)中對于卡套式管接頭的卡套制造精度、刃口熱處理硬度與鋼管的硬度、圓度等都有較高的要求。再加上我國國內(nèi)卡套式管接頭生產(chǎn)廠家經(jīng)驗(yàn)不足等原因，導(dǎo)致了不合格品比例較高，使卡套式管接頭在使用的過程中出現(xiàn)漏氣、拔脫等情況。
5.卡套式管接頭裝配質(zhì)量不穩(wěn)定
卡套式管接頭裝配的工藝較為復(fù)雜，需要裝配人員具有較高的水平與經(jīng)驗(yàn)，尤其是卡套式管接頭預(yù)裝方面。我國當(dāng)前專業(yè)的預(yù)裝機(jī)較少，大部分還是依靠手工進(jìn)行卡套式管接頭預(yù)裝，工作效率較低，而且裝配質(zhì)量受到工人技術(shù)水平、職業(yè)素質(zhì)等方面的影響，裝配質(zhì)量較不穩(wěn)定。
At present at home and abroad has been used in a structure of pipe connection, that is, the bayonet pipe joint connection method. In 1983, the national bureau of standards issued the universal standard for card and socket connection. There are many types of sleeve connection, such as squeeze type, expansion type, self-support type, bite type, etc. According to the standards issued by the national bureau of standards, the clamp-sleeve connection in China belongs to squeeze type and bite type, and its structure consists of three parts: the connector body, clamp-sleeve and nut. One of the key components is the sleeve - a metal ring with a cutting edge (the sleeve for indoor hot water heating is rubber).
Through the research on the domestic bayonet type pipe joint, it is found that the domestic bayonet type pipe joint has the following defects.
1. The bayonet pipe joint is out of date
China's current standard of sleeve type pipe joint is still the standard implemented more than ten years ago. Foreign bayonet tube joint has been updated many times, but our domestic bayonet tube joint always stays at a certain standard, far behind the development level of foreign bayonet tube joint.
2. There are still defects in terms of domestic standards
Although the standard of the sleeve pipe connector in China is relatively old and backward, but compared with the domestic standard, there are still problems below the standard, there are shortcomings, such as incomplete connector series, lower pressure level, can not cope with a variety of complex high-pressure occasions.
3. Lack of international diameter changing joint
At present, there is no international tapered joint in the domestic bayon-sleeve pipe joint. Although there are tapered joints with standard diameters, there are some problems in the materials, heat treatment and other aspects of such joints, which lead to the structure not being able to withstand high pressure. For the same reason, type B gusset hose couplings (used in conjunction with bayonet couplings) cannot be used in filling stations.
4. A high proportion of unqualified products
In the international standard, there are high requirements for the manufacturing accuracy, heat treatment hardness of cutting edge, hardness and roundness of steel pipe. Coupled with the lack of experience and other reasons of the domestic manufacturers of bayonet type pipe joints, leading to a high proportion of unqualified products, making the bayonet type pipe joints in the use of the process of leakage, pulling and other conditions.
5. The assembly quality of bayonet pipe joint is unstable
The assembly process of bayonet tube joint is complicated, which requires the high level and experience of the assembler, especially the pre-installation of bayonet tube joint. At present, there are few professional preassembly machines in China, and most of them rely on manual preassembly of bayonet pipe joints, which is of low working efficiency, and the assembly quality is affected by workers' technical level and professional quality, so the assembly quality is not stable.
