Troubleshooting and Installing the DTPD100UZ002 Induced Draft Fan Bearing Housing

One of the most persistent headaches during the overhaul of an induced draft (ID) fan is the improper installation of the main bearing housing. This often leads to misalignment, excessive vibration after tightening, and, in severe cases, the impeller rubbing against the casing. The root cause usually lies in one of two areas: the fan casing and the bearing housing were not mounted precisely, or the concentricity was not properly adjusted.

Using the DTPD100UZ002 bearing housing as our example, let's detail how to securely mount it to the fan casing while ensuring the main shaft runs smoothly and stably.

1. Positioning: The Guiding Role of the Casing's Shoulders

This ID fan utilizes a horizontally split casing structure. The lower half of the casing is equipped with a locating shoulder (止口/jizhima) specifically designed to receive the bearing housing.

• The DTPD100UZ002 housing has a matching locating boss  on its bottom surface.

• The fitting clearance between the shoulder and the boss is tightly controlled at 0.02 to 0.03 mm.

• Significance: By simply placing the housing gently into the shoulder, the lateral (horizontal) position is inherently corrected. This eliminates the need for repeated manual measurements, making the process both faster and more accurate.

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2. Fastening: Precision Tightening Sequence

The housing flange has eight highly precise bolt holes (H7 tolerance class), perfectly suited for high-strength bolts.

• Crucial Tip: The Three-Step Diagonal Tightening

  • Do not rush the tightening process. It must be performed diagonally and in three stages to prevent housing deformation under stress.

    1. First Pass: 50% of the final torque.

    2. Second Pass: 80% of the final torque.

    3. Final Pass: 100% of the final torque (typically 80–100 N·m, depending on bolt specifications).

• This method is not just a best practice; it is explicitly required by standards like GB/T 1236-2017 to ensure a rigid and non-deformed installation.

3. The Key to Success: Achieving Concentricity

True stability depends on achieving proper concentricity between the bearing housing and the fan's rotational centerline. The DTPD100UZ002 design achieves this through two main features:

1. Precision Machining: The inner bore of the bearing seat and the bottom locating boss are machined simultaneously using CNC equipment. This process guarantees a coaxiality error of no more than $0.02 \text{ mm}$.

2. Self-Correction: The fan casing's locating shoulder guides the entire bearing housing, causing it to automatically "self-align" to the fan's central axis.

4. Verification and Adjustment

How do you verify that the installation is successful?

• Procedure: Mount a dial indicator on the fan casing, position the stylus against the inner bore of the bearing seat, and slowly rotate (bar) the main shaft.

• Acceptance Criteria: If the radial runout is 0.01  mm, the alignment is satisfactory.

• Adjustment: If the runout exceeds the tolerance, slightly loosen or tighten a few of the flange bolts. This allows for small, controlled "micro-adjustments" to nudge the housing back into perfect alignment.

5. Associated Components

The bearing housing is only one part of a robust assembly. Field work often involves the following associated parts:

• Seals: CPMW laminated seal U184011 UZ22000 and seal ring HU25244-12G are used to prevent flue gas from entering the bearing box.

• Bearings/Bushings: Spherical plain bearing GE17, FAG radial bearing, and composite bushing ⅢDTYD30LG023 ensure the main shaft rotates flexibly.

• Tools: The YKS1120-10TH specialized puller is essential for safely removing old impellers without damaging the shaft.

• Other Parts: Components such as the intermediate shaft, crank, impeller shroud, and end caps are all designed as a matched set, and must be installed together for overall stability.

Final Reminder

If you consistently struggle to achieve the correct concentricity, first check the locating shoulder and boss for any nicks, dents,

or accumulated dust/debris. If the fit is found to be loose, you may need to replace the seals and re-calibrate the entire assembly.

HKZX-2025-12-16