The main external inspection of the pressure vessel includes: 1 Check the cylinder, cylinder head, etc. for cracks, deformation, leakage, shrinkage, sand holes, pores, shrinkage, obvious wear marks, etc. 2 The outer surface of the dryer has no corrosion and mechanical damage. Visual inspection of the bolts for the connection between the 3-cylinder and the cylinder heads at both ends (including the inspection of the performance level). 4The bearing support is intact and firm. 5 Whether the steam inlet and discharge device are intact and firm. 6 The transmission is in good condition. The internal inspection is mainly whether there is crack, deformation, etc. on the inner surface of the cylinder head; whether the inlet cover is defective; whether the siphon is firm, broken, corroded and perforated. Geometric size checks include: 1 Check that the outer dimensions of the dryer are consistent with the drawings. 2 For multi-cylinder complete installation, the maximum outer diameter and minimum outer diameter error of the same group of dryers should be no more than 0.5m. 3 The largest diameter and the smallest diameter of the same section. 4 Check if the discontinuous structure of the cylinder meets the design requirements. The wall thickness measurement position should be representative. Generally, it should be measured on both sides of the cylinder and not less than 4 points on one side. The middle section of the cylinder should be measured.