U-Type Cover Plate
Heat-resistant steel U-type cover plates for cement plant preheater dip tubes and meal pipes. Protective sleeve design with inspection windows for high-temperature zones. Temperature rating 900-1050 C
U-Type Cover Plate
Material Specifications & Selection Guide
| Grade | Standard | Max Temp | Wall Thickness | Key Feature | Application |
|---|---|---|---|---|---|
| ZG35Cr24Ni7SiN | GB/T 8492 | 1050 C | 8-20 mm | Nitrogen-strengthened, best creep & erosion resistance | Stage 4-5 dip tube cover plates, hot zone |
| ZG40Cr25Ni20Si2 | GB/T 8492 | 1050 C | 8-20 mm | Superior oxidation resistance, highest Ni | Calciner dip tube covers, heavy-duty sleeves |
| ZG40Cr25Ni12Si2 | GB/T 8492 | 1000 C | 8-18 mm | Balanced thermal fatigue & cost | Stage 3-4 standard cover plates |
| ZG30Cr26Ni5 | GB/T 8492 | 950 C | 6-15 mm | Cost-effective, good thermal shock resistance | Stage 1-3 cover plates, lighter-duty |
| ZG30Cr20Ni10 | GB/T 8492 | 900 C | 6-12 mm | Economical for cooler zones | Stage 1-2 cover plates, top-stage |
| Grade | C (%) | Cr (%) | Ni (%) | Si (%) | Mn (%) | N (%) | P/S Max |
|---|---|---|---|---|---|---|---|
| ZG35Cr24Ni7SiN | 0.30-0.40 | 23.0-26.0 | 6.0-8.0 | 1.30-2.00 | 0.50-1.50 | 0.15-0.25 | 0.040 |
| ZG40Cr25Ni20Si2 | 0.35-0.45 | 24.0-27.0 | 19.0-22.0 | 1.50-2.50 | 0.50-1.50 | – | 0.040 |
| ZG40Cr25Ni12Si2 | 0.35-0.45 | 24.0-27.0 | 11.0-14.0 | 1.50-2.50 | 0.50-1.50 | – | 0.040 |
| ZG30Cr26Ni5 | 0.25-0.35 | 24.0-28.0 | 4.0-6.0 | 1.00-2.00 | 0.50-1.50 | – | 0.040 |
| Grade | Tensile (MPa) | Yield (MPa) | Elong. (%) | Hardness (HBW) | Density |
|---|---|---|---|---|---|
| ZG35Cr24Ni7SiN | 480 | 245 | 8 | 170-220 | 7.75 |
| ZG40Cr25Ni20Si2 | 450 | 235 | 8 | 180-240 | 7.75 |
| ZG40Cr25Ni12Si2 | 440 | 220 | 6 | 180-230 | 7.70 |
| ZG30Cr26Ni5 | 450 | 235 | 10 | 170-220 | 7.80 |
Selection Quick Reference
- Stage 5 / calciner dip tube (950-1050 C, heavy erosion): ZG35Cr24Ni7SiN — nitrogen-strengthened for maximum creep strength and abrasion resistance in high-velocity gas streams
- Calciner / tertiary air duct (900-1050 C, oxidative): ZG40Cr25Ni20Si2 — highest Ni content (20%) for sustained oxidation resistance with long service life
- Stage 3-4 dip tube (800-950 C): ZG40Cr25Ni12Si2 — balanced performance, standard choice for mid-stage preheater protective sleeves
- Stage 1-2 dip tube (650-850 C): ZG30Cr26Ni5 — cost-effective with good thermal shock resistance for cooler zones
- All grades supplied with inspection window cutouts per specification, compatible with FLSmidth, KHD, Polysius, Sinoma, IKN preheater designs
Certifications & Authorizations
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Custom OEM / ODM
From drawing to delivery — one-stop customization, no minimum order
Send Drawing
Upload your technical drawing (PDF, DWG, STEP, IGES) or share sample photos with dimensions
Engineering Review
Material recommendation, casting process design, DFM analysis — free quotation within 24 hours
Sampling & Test
Prototype production with full inspection: hardness test, spectrometer, dimensional check
Production & Ship
ISO 9001 certified. 15-25 days standard lead time. Global shipping with full documentation
Frequently Asked Questions
The U-Type Cover Plate is a cylindrical protective sleeve installed around dip tubes and meal pipes in cement plant suspension preheaters. It serves three critical functions:
- Thermal protection: Shields the dip tube structure from direct flame and high-temperature gas impingement, reducing metal temperature at the tube surface by 100-150 C.
- Erosion barrier: Acts as a sacrificial wear layer against abrasive raw meal particles in high-velocity gas streams (15-25 m/s). Cover plates are designed to be replaced independently without changing the entire dip tube.
- Inspection access: The U-shaped profile with inspection windows allows visual inspection and measurement of internal dip tube condition without removing the entire assembly.
Key advantage: Cover plates are bolted/slip-fit designs that can be replaced during a short maintenance stop, avoiding costly full dip tube replacements. Keep one spare set per preheater stage in inventory.
Cover plates are custom-fit to your specific dip tube geometry. To ensure a perfect replacement, please provide the following measurements:
- Dip tube outer diameter (OD): The cover plate ID must match the dip tube OD with a 3-5 mm clearance for thermal expansion and easy installation.
- Cover plate length: Overall sleeve length from top flange to bottom edge. Also specify the position and dimensions of any inspection windows.
- Wall thickness: Standard is 8-15 mm. Thicker walls (15-20 mm) are available for high-erosion zones but add weight — verify dip tube support structure can handle the additional load.
- Mounting method: Bolted flange, slip-fit with retaining lugs, or welded tabs. Include flange bolt pattern (number of bolts, PCD) for bolted designs.
No drawings? Send us the dip tube model and preheater stage number. Our engineers can reverse-engineer from the cyclone geometry or from photos and measurements of your existing worn cover plate.
Cover plates are wear components designed to protect the more expensive dip tube structure. Their service life depends on temperature, gas velocity, and raw meal abrasiveness:
Key replacement triggers — inspect during every annual shutdown:
- Wall thinning >50%: Measure remaining wall thickness with ultrasonic thickness gauge. When half the original wall is gone, plan for replacement at the next opportunity.
- Through-wall cracking: Any crack that penetrates more than 60% of the wall thickness is a critical defect. Thermal cycling fatigue cracks are normal, but penetrating cracks require immediate attention.
- Window edge erosion: The inspection window edges are high-wear points. If the window opening has enlarged by more than 10 mm from original, gas bypass is occurring.
- Mounting point looseness: Loose flanges or retaining lugs indicate thermal creep deformation. This can lead to cover plate detachment if not addressed.
Life extension tip: Rotate cover plates 180 degrees during annual maintenance if wear is concentrated on one side (typically the gas-on side). This doubles effective service life before replacement is required.
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