At present, the stem seals of low-temperature stainless steel stop valves include stuffing box and bellows. Among them, the valve stem of mass-produced air separation devices mostly adopts stuffing box sealing structure. For valves working in toxic, flammable and explosive gas medium, the valve stem can be sealed with wave tube. However, in high-pressure gas greater than or equal to 80MPa, the bellows can not bear such high external pressure, so the stuffing box seal can only be used. The stuffing box seal is widely used in actual production because of its simple manufacturing and processing and convenient maintenance.

良工閥門

Lianggong valve

但是為保證填料的密性能,其工作溫度一般不能低于-40℃,這就要求低溫閥門上工作的填料函裝置應(yīng)盡量在接近環(huán)境溫下工作。通常情況下,填料不結(jié)霜即認為其處于正的工作狀態(tài),但如果由于填料本身或工作壽命的原使填料不密封,則低溫氣體通過填料就會造成泄漏并使填料函冷凍結(jié)霜,又會造成填料的進一步泄漏失效。

However, in order to ensure the tightness of the packing, its working temperature shall not be lower than - 40 ℃, which requires that the stuffing box device working on the low-temperature valve shall work as close to the ambient temperature as possible. Under normal circumstances, the packing is considered to be in a positive working state if it does not frost. However, if the packing is not sealed due to the original of the packing itself or service life, the low-temperature gas will cause leakage through the packing and freeze the stuffing box, which will also cause further leakage and failure of the packing.

在航天領(lǐng)域應(yīng)用的很多低溫閥門系列中,由于成原因大多采用了填料函密封結(jié)構(gòu),而為了確保閥桿填料函的溫度,均采用了加長閥桿長度的方法,所造成這些低溫閥的尺寸均比較大。

In many low-temperature valve series applied in the aerospace field, the stuffing box sealing structure is mostly adopted due to the reasons. In order to ensure the temperature of the valve stem stuffing box, the method of lengthening the valve stem length is adopted, resulting in the relatively large size of these low-temperature valves.

低溫不銹鋼截止閥多用于介質(zhì)不允許微量泄漏和不適填料的場合。在波紋管的設(shè)計中,其壽命是關(guān)鍵,波紋管的壽命與其行程大小和初始安裝狀態(tài)有關(guān)。

Low temperature stainless steel stop valves are mostly used in occasions where the medium does not allow micro leakage and unsuitable packing. In the design of bellows, its service life is the key. The service life of bellows is related to its stroke size and initial installation state.

良工閥門

Lianggong valve

保證波紋管截止閥的使用壽命,在行程一定的情況下,安裝波紋時要保證其不承受附加外力的作用;在工作狀態(tài)下由于波紋管承受的是外壓,其工作狀態(tài)較好,但由低溫閥門的快速關(guān)閉或管道中可能存在的氣穴都可能引水擊。因此在波紋管承受的計算壓力時,要加上定的安全系數(shù),并盡可能使波紋管避免直接承受水擊。

Ensure the service life of the bellows stop valve. When the stroke is certain, ensure that it does not bear the effect of additional external force when installing the bellows; In the working state, because the bellows bears external pressure, its working state is good, but water hammer may be caused by the rapid closing of low-temperature valve or possible cavitation in the pipeline. Therefore, when calculating the pressure borne by the bellows, a certain safety factor shall be added, and the bellows shall avoid directly bearing water hammer as far as possible.