结焦是因螺杆压缩机油发生一系列的化学变化而致。润滑油属于有机化合物，以矿物油为例，其主要组分为各种烃类(分烷烃、芳烃、环烷烃等），烃类化合物受热、氧、光的作用会发生氧化反应，接触热、氧强度越高，其氧化反应速度越强烈。氧化会使分子链断裂，也有可能交联，无论断链与交联都会使烃类化合物产生性质改变。在实际应用中表现为油品粘度增长，酸值增加，颜色改变，不溶物增加等，当发生深度氧化反应时油品粘度显著增长超过了一定范围，就产生了油品结焦现象。

Coking is caused by a series of chemical changes in screw compressor oil. Lubricating oil belongs to organic compounds. Taking mineral oil as an example, its main components are various hydrocarbons (including alkanes, aromatics, naphthenes, etc.). Hydrocarbon compounds can be oxidized by heating, oxygen and light. The higher the contact heat and oxygen intensity, the stronger the oxidation reaction speed. Oxidation can break or cross-link molecular chains, which will change the properties of hydrocarbons. In practical application, oil viscosity increases, acid value increases, color changes, insoluble matter increases, etc. When deep oxidation occurs, oil viscosity increases significantly beyond a certain range, resulting in oil coking phenomenon.

当然，不同性质的压缩机油发生氧化反应时性质改变有所不同，在实际应用中，螺杆压缩机油大部分结焦事故都是使用低档矿物油引起，下面举一些常见螺杆压缩机油深度氧化后氧化产物。

Of course, the properties of compressor oils with different properties change differently when they are oxidized. In practical application, most coking accidents of screw compressor oils are caused by using low-grade mineral oils. Here are some common oxidized products of deep oxidation of screw compressor oils.