Fluoroplastics pumps and stainless steel pumps are corrosion-resistant pumps, fluoroplastics pumps are generally divided into fluoroplastics centrifugal pumps, fluoroplastics magnetic pumps, fluoroplastics alloy pumps. Stainless steel pump can be divided into stainless steel centrifugal pump, stainless steel magnetic pump. Fluoroplastics pump and stainless steel pump have vertical and horizontal structure, with self-priming, magnetic, centrifugal and other forms, so what is the difference in performance between the two anti-corrosion pumps? Fluoroplastics material, also known as plastic king, can transport any concentration of strong acid, strong alkali, strong corrosive solution. Generally, stainless steel material is suitable for conveying light rotten liquid. Stainless steel pump has better temperature resistance and wear resistance, and fluoroplastics pump has good corrosion resistance, which is the advantage and disadvantage of the overall performance. Structurally, due to the difference in performance between stainless steel pump and plastic pump, the structural design of stainless steel pump has the following particularities.
I. Connection Form of Impeller and Shaft
1. The metal parts embedded in the impeller are connected with the shaft by keys, or the impeller is directly connected with the shaft by keys, and the end of the impeller is protected by impeller nuts. This structure comes from metal pump, because of many sealing surfaces, the reliability is poor. After a long time of use, the shaft is easily corroded by medium.
2. The metal parts embedded in the impeller are connected with the pump shaft by threads, and the impeller nuts are cancelled. This structure can protect the shaft completely and avoid the possibility of the shaft being corroded by the medium. The disadvantage is that the thread processing accuracy is required to be high, and motor inversion is strictly prohibited when running.
Stainless steel pump
2. Thickness and Fixation of Pump Body Lining Layer
According to pump enterprise standards, the thickness of lining layer is generally 5-8 mm. If the lining layer is too thin (e.g. 1.5-2 mm), local lining defects are likely to occur during the pressing process, resulting in a decrease in the allowable operating temperature and service life of the pump, and the possibility of the lining layer falling off from the base metal of the pump body and back cover is also increased.
The method of fixing the lining layer can adopt the method of arranging dense annular dovetail groove on the base metal, so that the lining layer can be fixed firmly and the machining quantity is small. It can also use the method of arranging denser holes (or threaded holes) on the base metal. The lining layer is not as fixed as the swallow tail groove.
At present, there is no relevant standard to limit the force on the inlet and outlet nozzles of plastic pumps. Generally, it is required by the design unit, and it depends on the manufacturing conditions of the manufacturer itself. For integral plastic pump shell, looper flange is usually used to connect with pipeline, looper flange is connected with both ends of cover plate, and flange and cover plate can also be used to make integral connection with pipeline.
4. Operating Clearance between Impeller Seal and Back Blade and Pump Body
Because the linear expansion coefficient of plastics and FRP is 2-6 times larger than that of steel, it is easy to bite along the running clearance of stainless steel pump, which causes damage to the pump. Excessive clearance will reduce the efficiency of the pump and cause the unbalance of the axial force of the pump. Because the radial clearance is not adjustable, the axial clearance can also be considered, so that the operating clearance can be checked and adjusted without dismantling the pump. In order to prevent the plastic pump shell from falling off or cracking caused by temperature change, the tortoise shell wire mesh can be welded on the pump shell, so that the lining pump can achieve a larger size and the diameter of the inlet pipe can reach DN600.
V. Axial Equilibrium Force
Metal parts are embedded in the impeller of fluoroplastics pump. Generally, it is not appropriate to balance the axial force by means of balancing holes. Back blade balancing axial force is widely used at home and abroad.