I recently repaired a multi-stage pump, and there are some issues I still can’t figure out; I hope some experts can give me some advice
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For the feed pump in the delayed coking unit, the mechanical seals and bearings were installed at the appropriate times; both end seal plates were in a locked position. A dial indicator was used to measure the axial movement, with the shaft being pushed towards the drive end, after which the bearing caps were tightened until they could no longer be moved any further. It was found that the amount of axial movement was quite large, around 140 units. This amount seems to represent half of the shaft’s total axial movement. Later, a copper sheet with a thickness of 130 units was added behind the adjustment shims. My questions are: 1. Why is the axial movement so large when using this setup? 2. Could such a large axial movement be caused by wear on the balance weights? 3. The pump operates fine now, but once the axial movement increases, can it always be adjusted by adding more shims?
1. Wear of the wear plate, 2. Bearing clearance, 3. Impeller wear, I guess
It’s really difficult to determine your issue without pictures of the pump – there are many different types of multi-stage pump structures! It would be best to have images or a structure diagram! It’s certain that 140 strands (1.4mm) is definitely not half the penetration depth!
The OS pump is an axial split-volute centrifugal pump. It is mainly suitable for applications such as water treatment plants, air conditioning circulation water systems, building water supply systems, irrigation, drainage pump stations, power plants, industrial water supply systems, fire protection systems, and ships, where industrial liquids need to be transported. Structural features: 1. Compact structure: linear design, attractive appearance, good stability, and easy to install. 2. Smooth operation: The optimally designed double-suction impeller minimizes axial forces, features blade shapes with excellent hydraulic performance, and is manufactured through precision casting; as a result, the inner surface of the pump casing and the impeller are extremely smooth, granting significant cavitation resistance and high efficiency. 3. Bearings: High-quality bearings are used to ensure smooth operation, low noise, and a long service life. 4. Oil seal: High-quality mechanical seals that prevent leakage can be used, or soft packing that meets environmental requirements can also be employed.
There are several types of axial clearances in multi-stage pumps. The first type is the rotor clearance; when no balance disk is used, it represents the total clearance, while with a balance disk in place, it refers to the partial clearance, which is generally half of the total clearance. In the case of high-temperature pumps, the front clearance is about 0.5–1 mm greater than the rear clearance. The second type is the clearance provided by the balance disk, which is usually around 0.2–0.3 mm. The third type is the thrust clearance of the bearings; the axial clearance between the rolling bearings and the gland is generally 0.02–0.06 mm. Based on what you said, since the bearing seals have been installed, it should be the clearance between the rolling bearing and the bearing cover, that is, the thrust clearance. The place where you should insert shims is either at the bearing cover or at the shoulder of the bearing; however, it is generally not recommended to use shims for the inner ring.
1.4 is definitely not serial communication; I guess what you’re describing is adjusting the axial clearance of the balance disc to 0.1