After long-term use of fluorine-lined centrifugal chemical pump, the vulnerable parts in the fluorine-lined centrifugal chemical pump will be worn to a certain extent. It mainly includes mechanical seals, bearings, impellers, etc., and the equipment will be damaged as the operating time increases. When we use fluorine-lined centrifugal chemical pumps, we must pay attention to the maintenance of fluorine-lined centrifugal pumps. On the contrary, we can reduce the cost during overhaul. So how should we overhaul the parts of fluorine-lined centrifugal chemical pumps?
1 fluorine-lined centrifugal chemical pump coupling overhaul
Chemical pump couplings mainly include rigid couplings and gear couplings.
(1) Rigid coupling
Rigid couplings are generally used on centrifugal pumps with lower power. First remove the connecting bolts and rubber elastic ring during maintenance. For liquids with low temperature, the plane clearance of the two couplings is 2.2～4.2 mm. , When the temperature is high, it should be 1. 55～2.05 mm greater than the forward displacement. The rubber elastic ring of the coupling should be 0.15～0.35 mm smaller than the diameter of the perforation. At the same time, special tools must be used when disassembling and assembling, keep it clean, and no bruises or scratches are allowed.
(2) Gear coupling
Gear coupling has good flexibility and has automatic centering performance. The maintenance is generally carried out according to the following methods:
①Check the gear tooth surface meshing of the coupling, the contact area is not less than 50% along the tooth height, and not less than 70% along the tooth width, and the tooth surface must not have serious pitting, wear and cracks;
②The radial runout of the outer gear ring of the stainless steel pump coupling is not more than 0.03 mm, and the end circle runout is not more than 0.02 mm;
③If you need to remove the gear ring, you must use a special tool, do not knock, so as not to bend or damage the shaft. When reinstalling, the ring gear should be heated to about 200 ℃ and then installed on the shaft. The interference between the outer gear ring and the shaft is generally 0.01 to 0.03 mm;
④When reinstalling the intermediate tube or other parts, it should be assembled according to the original markings and data;
⑤ Use a torque handle to tighten the bolts evenly.
2 Fluorine-lined centrifugal chemical pump dynamic seal part maintenance
The dynamic seal of fluorine-lined centrifugal pump refers to the seal of the impeller orifice ring. Generally, the radius direction should be controlled within 0.20～0.45 mm. If the clearance is too small, it will be difficult to crank the assembly after assembly; if the clearance is too large, it is easy to cause pump vibration. The radial direction of the clearance between the bushing and the backing ring is generally 0.2～0.6 mm.
3 Fluorine-lined centrifugal chemical pump static seal part maintenance
The static sealing part of the chemical pump includes the split joint surface of the pump body, the joint surface of the bearing gland and the bearing box, the joint of the lubricating oil system, the flange of the inlet and outlet pipes, etc. run. For the sealing of the above parts, as long as the suitable adhesive and gasket are selected according to the medium, no leakage can be guaranteed. Nanda 703 and Nanda 704 are commonly used for split bonding surface adhesives.
4 Fluorine-lined centrifugal chemical pump impeller and rotor maintenance
Commonly used fluorine-lined centrifugal chemical pumps are mostly single-stage impellers or single-stage double-suction rotors. When overhauling, first check the appearance of the impeller and clean it. Whether it is replacing spare parts to install a new impeller or cleaning the old impeller, static balance should be done after reinstallation, and dynamic balance should be done if necessary. The matching of impeller and shaft adopts H/h. When installing the impeller, the key and the keyway should be in correct contact. The allowable bending of the shaft diameter of the rotor part should not be greater than 0.013 mm, the maximum bending of the low-speed shaft should be less than 0.07 mm, and the maximum bending of the high-speed shaft should be less than 0.04 mm. The assembly of the sleeve part and the shaft adopts H/h.
For the shaft of the rotor part, the radial runout of the shaft after maintenance is not more than 0.013 mm, the shaft sleeve is not more than 0.02 mm, the impeller mouth ring is not more than 0.04 mm, and the impeller end face runout is not more than 0.23 mm. The shaft diameter at both ends is not greater than 0.02 mm. But for centrifugal pumps with more complicated structures, the above data varies according to the pump condition standards.
5 Fluorine-lined centrifugal chemical pump mechanical seal maintenance
When overhauling the mechanical seal of a chemical process pump, first use special tools to correctly remove the dynamic and static rings of the mechanical seal, and check the wear on the end face. All pump rotors with mechanical seals, regardless of power, should be tested for dynamic or static balance. . In order to ensure that the seal does not leak, the dynamic and static surfaces can be pressed tightly on the fitter's platform, and water is poured for a leakage test. If the static water does not leak, it indicates that the surface roughness and flatness of the sealing surface meet the requirements. The verticality deviation of the end face during installation is not more than 0.015 mm.
The axial movement of the shaft after installation is not more than 0.45 mm. It should be emphasized that after the mechanical seal is installed as required, the machine must be cranked and the cooling water part must be checked for reliability to prevent leakage or damage to the end face of the machine seal after rotation. The mechanical seals of pumps used in chemical plants are mostly single-stage, double-stage, and tandem seal arrangements, but no matter what kind of seal arrangement, there should be no leakage.
(1) Single-stage seal arrangement of pump
When installing a single-stage seal, it is necessary to ensure that the moving and static rings are parallel, and there should be no burrs or scratches on the shaft sleeve and shaft neck.
(2) Two-stage seal arrangement of machine and pump Two-stage seal arrangement of machine and pump.
Two-stage layout seal installation must ensure the size and clearance of the positioning ring, and push it to the position once, the O-ring cannot fall out of the groove, otherwise the sealing surface of the mechanical seal will be damaged.
