The structure of the tube side or shell side of the oil cooler includes the scale formed due to the poor water quality, the oil scale caused by the oil stain, and the forms of coking deposition and thermal adhesion scaling. Before chemical scale removal, chemical analysis should be carried out on the scale substance of oil cooler to make clear the composition of scale substance, decide which reagent to choose and make hanging piece. Generally, the scale of sulfate and silicic acid is cleaned by alkali washing method, and the scale of carbonate is cleaned by acid detergent.
As for the deposit of some fluid medium or the decomposition product of organic matter, there are some alloy scales formed by several metals, and the corresponding activator should also be selected. After heating and soaking the activator solution, the surface tension between the scale layer and the oil cooler will be reduced or loosened; then acid cleaning or alkali cleaning will be determined according to the chemical characteristics of the scale layer. Before acid or alkali cleaning, hang pieces with the same or nearby raw materials as the cleaned surface. During cleaning, put them in the cleaning tank and monitor them at any time, so as to avoid excessive corrosion to the oil cooler due to improper cleaning formula. Take samples of the cleaning solution according to the time to analyze the change of iron ion concentration.
In order to ensure the expansion quality of the oil cooler, it is necessary to select the appropriate expansion rate, which is usually indicated by the percentage of the expansion degree and the diameter of the pipe hole thickness. The whole expanding process can be divided into two steps:
1. The oil cooler uses a tube expander to expand the pipe in the pipe hole, so that the outer wall of the pipe is closely connected with the pipe hole;
2. Expand the tube and tube hole to the required value, and turn the end into the shape of horn. In this process, the inner diameter of the pipe expands by a value, which is the degree of expansion.
Generally, the expansion degree of the oil cooler is indicated by the relative percentage of the inner diameter of the tube plate, the thickness of the tube wall or the inner diameter of the tube. If the expansion rate of the tube is too small, the deformation amount of the tube and the tube hole is insufficient, the plastic deformation of the tube is not good, and the elastic deformation of the tube hole is correspondingly small, so that the condenser tube and the tube plate can not fit tightly, and the sealing capacity is small, which is called "under expansion".
If the expansion rate of the tube is too large, the diameter of the tube hole will increase, which is larger than the elastic deformation, and plastic deformation will occur. The oil cooler will not be able to withstand the fluctuation of temperature difference and pressure change, and some micro cracks may occur on the tube or tube plate, which will reduce the strength and tightness of the tube plate, which is called "over expansion".