The main forms of valve damage are wear, bending and skew. The reasons are as follows:

　　①氣門和氣門座圈受高溫、高壓氣體的沖擊和承受工作過程中的機械負荷，容易燒蝕和磨損。氣門與氣門座圈的工作斜面，由于氣門不停地開啟和關閉，相互撞擊、敲打，承受反復的沖擊負荷，引起工作斜面的磨損、起槽、斑點和凹陷。

　　Valves and seat rings are easily ablated and worn by the impact of high temperature and high pressure gas and the mechanical load in the working process. The working incline of the valve and the valve seat ring is attacked, grooved, spotted and sunken due to the constant opening and closing of the valve, the impact and knocking of each other, and the repeated impact load.

　　②氣門桿部在氣門導管內運動時不斷摩擦，潤滑條件又差，加上竄進的灰塵磨料，使兩者均受到磨損。

　　(2) When the valve rod moves in the valve conduit, it rubs continuously, and the lubrication condition is poor, together with the dust abrasive, which makes both of them suffer from wear and tear.

　　③氣門導管內進人積炭結膠，加速氣門桿與導管間的磨損。

　　(3) Carbon deposit cementing is introduced into the valve duct to accelerate wear and tear between the valve stem and the duct.

　　④氣門桿尾端與搖臂之間相互撞擊，使兩者都受到磨損。

　　(4) The tail end of valve rod and rocker arm collide with each other, which makes both of them suffer from wear and tear.

　　⑤氣門頂部受氣缸內氣體壓力、氣門桿尾端受凸輪通過挺柱的撞擊，造成氣門桿的彎曲。

　　The top of the valve is subjected to the gas pressure in the cylinder and the end of the valve rod is impacted by the cam passing through the tappet, which causes the bending of the valve rod.

　　⑥氣門頂與活塞碰撞而使氣門桿彎曲。

　　_The valve rod is bent by the collision between the valve top and the piston.

　　⑦氣門桿尾端面搖臂間的間隙過小，受熱膨脹后，頂住氣門桿尾端而使其彎曲和端面不平。

　　_The clearance between rocker arms at the end of the valve rod is too small. After being heated and expanded, the end of the valve rod is held against and the bending and end surface of the valve rod are uneven.

　　⑧氣門或氣門座圈工作面與氣門桿不同心，氣門座與氣門導管不同心而使氣門桿彎曲。

　　_The working face of valve or valve seat ring is not concentric with the valve stem, and the valve seat is not concentric with the valve duct, which makes the valve stem bend.

　　⑨氣門桿與氣門導管受磨損后，使配合間隙增大，氣門桿在管內晃動使氣門歪斜，引起氣門頭部的偏磨。

　　_After wear and tear of the valve rod and the valve duct, the fit clearance increases, and the valve rod sloshing in the tube causes the valve to skew, causing eccentric wear of the valve head.

　　⑩氣門桿彎曲后，形成氣門頂部的歪斜和偏置。

　　_After the valve stem is bent, the inclination and offset of the top of the valve are formed.