In actual use, some non oil vacuum pump users will find no oil vacuum pump for airtight container pumping, found that the actual pumping rate and pump specifications of the pumping rate differences, and even greater differences. In principle, as one of the volume pumps, the pumping rate of the micro vacuum pump is determined only by the pump itself. In the case of pump failure and leakage of the container, the reasons are mostly from the gas extraction pipeline.

 

密闭容器的抽气速率是被抽气体在离开密闭容器处的速率，其影响因素有：

 

The extraction rate of a closed vessel is the rate at which the extracted gas moves away from the closed vessel, and the influencing factors are:

 

1、漏入密闭空间的外界空气量。虽然有些密闭空间可以做到只有极低的空气泄漏量，但几乎没有一个能达到完全气密。必须考虑到空气泄漏量。压差越大泄漏泄漏也越大。

 

1. The amount of external air leaking into the confined space. Although some confined spaces can be operated with very low air leakage, almost none of them can be completely airtight. The amount of air leakage must be taken into account. The greater the pressure difference, the greater the leakage and leakage.

 

2、密闭空间中的可凝蒸气量。对一个存在气液两相的密闭空间，在抽真空时，其液面上的可凝蒸气也将被抽走，所以必须考虑这些可凝蒸气的量。

 

2. Condensable steam in confined space. For a confined space with gas-liquid two-phase, the condensable vapor on the liquid surface will also be evacuated when the vacuum is evacuated, so the amount of condensable steam must be considered.

 

3、生产过程中释放的气体量。1504598048138028.png

 

3, the amount of gas released during the production process.

 

真空泵抽气速率与密闭容器实际抽气速率的关系如下。

 

The relationship between the pumping rate of vacuum pump and the actual pumping rate of airtight container is as follows.

 

真空泵与密闭容器之间一般均用管道连接。管道对气体流动有阻力，形成了压降。

 

The vacuum pump and the airtight container are generally connected by pipes. The pipeline has a resistance to gas flow and a pressure drop is formed.

 

P1为密闭空间的压力；

 

P1 is the pressure in confined space;

 

P2为真空泵入口的压力;

 

P2 is the inlet pressure of the vacuum pump;

 

Q1，Q2分别为密闭空间和真空泵的抽气流量，mmHg·m3/h；

 

Q1, Q2 is the pumping volume of confined space and vacuum pump, mmHg / m3/h;

 

S1，S2分别为密闭空间和真空泵的抽气速率，m3/h。

 

S1 and S2 are the pumping rate of confined space and vacuum pump, respectively, m3/h.

 

其中，S1=Q1/P1，S2=Q2/P2。

 

Among them, S1=Q1/P1, S2=Q2/P2.

 

稳定状态时，Q1=Q2，故S1×P1=S2×P2，可知，S2=S1×（P1/P2）。

 

When stable, Q1=Q2, so S1 x P1=S2 x P2, knowable, S2=S1 x (P1/P2).

 

在任何操作情况下，要抽气必然密闭空间的压力大于空泵入口的压力， P1>P2，（P1/P2）>1，故，S2>S1。

 

In any operation, the pressure in the confined space must be greater than the pressure at the inlet of the air pump, P1>P2, (P1/P2) >1, so S2>S1.

 

引入管道流体阻力（W）或流体通导能力（U）并分别定义为：W=（P1-P2）/Q，U=1/W，已知封闭空间抽气速率S1，则推出：S2=S1/（1-S1/U）=S1/（1-WS1）。抽气管道的压力损失越小，S1和S2之差越小。只有当管道阻力无限小或流体通导能力无限大时，真空泵的抽气速率才等于密闭空间的抽气速率。

 

The pipeline fluid resistance (W) or the fluid conductivity (U) are defined as W= (P1-P2) /Q, U=1/W, and the S2=S1/ (1-S1/U) =S1/ (1-WS1) is introduced when the pumping rate is S1 in the enclosed space. The smaller the pressure loss of the suction pipe, the smaller the difference between S1 and S2. The pumping rate of vacuum pump is equal to the pumping rate in confined space only when the pipeline resistance is infinite or the fluid conduction capacity is infinite.

 

抽气管路的阻力对抽气速率影响较大，实际使用中不可忽视。技术人员对各种型号微型真空泵的抽气速率进行了测试，连接11m长的抽气管道时，抽气速率甚至会下降到连接1m长抽气管道时的50-60%。真空泵性能说明书的抽气速率是在标准实验条件下进行的，而用户实际的使用条件是千差万别。为了保证抽气速率，客户使用时应尽量缩短抽气管道长度，增大管道口径，减少弯头、阀门等阻力元件。用户在选用无油真空泵时，如果抽气管路阻力较大，应选用流量较大的型号。

 

The resistance rate of gas pumping exhaust pipe affect the actual use can not be ignored. The pumping rate of various types of micro vacuum pumps was tested by technicians. When the gas pipeline with 11m length was connected, the pumping rate would even drop to 50-60% when connecting 1m long suction pipe. The pumping rate of the performance specifications of vacuum pumps is carried out under the standard experimental conditions, while the actual conditions of users are varied. In order to ensure the pumping speed, customers should shorten the length of the gas extraction pipeline, increase the caliber of the pipeline, reduce the elbow, valve and other resistance components. In the selection of oil-free vacuum pump, if the suction pipe resistance is larger, the larger flow type should be selected.