U-Type Tube Shield
Integrated stamped alloy U outer half round protective sleeves, exclusively protect boiler U-bend / return bend outer arcs against high-speed fly ash scouring and high-temperature flue corrosion, multi stainless alloy optional.
Heat-treatable SS420 martensitic half round tube shields, higher hardness than SS410 for medium abrasion economizer tube bundles, complete matched SS420 C/U snap ring installation fasteners.
420 stainless steel tube shields, also known as SS420 U-type half round boiler sleeves, belong to high-carbon martensitic stainless protective casings, an upgraded variant of SS410 material series. Compared with standard SS410, SS420 features higher carbon content, which can be heat-treated to achieve higher surface hardness and outstanding anti-scouring performance, perfectly matching boiler tail flue working conditions with medium fly ash abrasion and low sulfur concentration.
Many biomass boilers, small CFB circulating fluidized bed boilers and industrial waste heat boilers have economizer sections operating under flue temperature below 600°C, where fly ash particle impact intensity is higher than conventional light-abrasion scenarios suitable for SS410. In such environments, SS420 half round tube shields deliver longer service life without jumping to high-cost nickel-containing 309S stainless grades, balancing abrasion performance and overall project budget effectively.
We manufacture full structural series in pure SS420 material: straight half sleeves, inner U-bend wrap shields, outer bend full wrap sleeves and wave fin inter-tube baffles. All supporting C-type & U-type snap lock fasteners are produced from identical SS420 alloy, eliminating dissimilar metal galvanic corrosion risk under long-term high-temperature flue gas operation.
SS420 stainless steel tube shields fill the performance gap between low-cost SS410 and high-temperature austenitic stainless materials, supporting three mature protection schemes for different flue abrasion severity levels:
Integral hydraulic stamped 180° semicircular sleeve is our flagship SS420 product. Precision-matched radian fully fits standard ASME boiler heat transfer tube outer diameters without gaps, avoiding trapped ash and localized concentrated abrasion. Two installation options including snap ring clamping and spot welding support flexible construction during annual boiler shutdown maintenance, widely adopted for mass economizer tube bundle renovation projects requiring medium anti-scour capacity and controlled procurement cost.
For working conditions with continuous heavy fly ash impact where single SS420 plate cannot reach expected service cycle, we supply composite shields combining SS420 outer shell and thin alumina ceramic lining. This design retains martensitic steel cost advantages while greatly lifting overall wear resistance, ideal for medium-sulfur biomass boiler tail flues and medium-load CFB economizer zones.
Thin SS420 plate can act as base carrier for high-temperature wear-resistant ceramic coating spraying, applied on densely packed compact tube bundles where standard half round sleeves cannot be mounted. It forms dual metal + coating composite protection layer to extend the service cycle of base heat transfer tubes.
SS420 (UNS S42000) is high-carbon martensitic stainless steel complying with ASTM A240 standard, its chemical composition and mechanical indicators are specially optimized for medium-temperature boiler tail flue anti-abrasion components:
| Performance Item | Standard Parameter Value | Inspection & Test Standard |
|---|---|---|
| Carbon Content (C) | 0.15 ~ 0.25 % | ASTM A240 Spectral Composition Test |
| Chromium Content (Cr) | 12.0 ~ 14.0 % | ASTM A240 Spectral Composition Test |
| Tensile Strength (Annealed State) | ≥ 655 MPa | ASTM A370 Tensile Mechanical Test |
| Yield Strength (0.2% Offset) | ≥ 345 MPa | ASTM A370 Tensile Mechanical Test |
| Max Continuous Long-term Service Temperature | ≤ 600°C | Actual Boiler Flue Application Verification |
| Maximum Hardness After Heat Treatment | HRC 48 ~ 50 | Rockwell Hardness Test |
Material Selection Critical Reminder: SS420 tube shields are only applicable to low-sulfur flue environments below 600°C; do not deploy in high-sulfur coal-fired furnace zones or flue temperature over 620°C. For ultra-high temperature and heavy sulfur working conditions, select 309S or 310S austenitic stainless half round tube shields instead.
All SS420 erosion protective sleeves adopt integrated hydraulic stamping forming process, with strict incoming material inspection and surface finishing treatment to guarantee stable long-term service performance inside boiler flues:
Stock SS420 semicircular sleeves match mainstream ASME SA179, SA210, SA213 heat transfer tube outer diameters, non-standard arc radian and total sleeve length support dedicated mold customized development:
| Matched Base Tube Outer OD (mm) | SS420 Alloy Plate Thickness (mm) | Shield Total Length Range (mm) | Common Structural Form Type |
|---|---|---|---|
| 32 / 38 / 42 | 6 / 8 | 100 ~ 1200 | Straight half round single tube anti-erosion sleeve |
| 51 / 57 / 60 | 8 / 10 | 150 ~ 1800 | Straight half wrap / wave fin inter-tube protective baffle |
| 76 / 89 | 10 / 12 | 200 ~ 2500 | Outer U-bend full wrap semicircular shield |
Note: Extra thick enhanced wear-resistant SS420 plate, super long customized sleeves and oversized large radian bend shields can be custom manufactured strictly according to customer boiler construction layout drawings.
Two mature installation schemes are provided to adapt different boiler overhaul construction cycles and flue fly ash abrasion intensity levels:
All supporting snap lock fasteners adopt pure SS420 stainless material consistent with tube shield body, effectively avoid electrochemical corrosion phenomenon generated by dissimilar metal contact under long-term high-temperature sulfur-containing flue gas environments.
| Supporting Product Name | Core Functional Description | Matching Application Working Scene |
|---|---|---|
| 420 Stainless Half Round Tube Shield | Semicircular outer wall anti-scour wrap for single boiler heat transfer tube | Economizer, low-temperature superheater straight tube bundle protection |
| SS420 C & U Snap Lock Fasteners | Non-weld quick locking clip matched for half round tube shields | Small & medium diameter tube bundles with frequent inspection requirements |
| SS420 Wave Fin Inter-tube Anti-wear Baffle | Ash impact buffer plate installed between adjacent finned heat exchange tubes | Water wall fin transition medium abrasion flue zones |
| SS420 Cast Alloy Saddle Pipe Clamp | Heavy-duty fixed support for full tube bundle assembly layout | Large-scale economizer tube bundle overall fixed installation framework |
420 stainless steel tube shields are specially developed for medium-temperature tail flue heating surfaces with medium fly ash abrasion and low sulfur flue gas content:
Application Limit Reminder: SS420 tube shields cannot be applied to furnace arch, high-temperature superheater zones over 600°C and high-sulfur coal combustion flue environments, please select 309S / 310S high-temperature stainless half round shields for above harsh working conditions.
| Comparison Item | 410 Stainless Shield | 420 Stainless Shield | 309S Stainless Shield | 310S Stainless Shield |
|---|---|---|---|---|
| Max Continuous Service Temperature | 550°C | 600°C | 850°C | 1150°C |
| Post Heat-treatment Hardness (HRC) | 38 ~ 45 | 48 ~ 50 | 22 ~ 28 | 23 ~ 29 |
| Medium Fly Ash Abrasion Resistance | General | Excellent | Good (High Temp Only) | Good (Ultra High Temp Only) |
| Sulfur Flue Corrosion Resistance | Only low-sulfur flue | Only low-sulfur flue | Medium sulfur tolerance | High temp anti-oxidation, average sulfur resistance |
| Raw Material Procurement Cost Level | Lowest | Low | Medium | Highest |
| Core Applicable Boiler Zone | Light abrasion economizer below 550°C | Medium abrasion economizer below 600°C | Medium-high temperature superheater | Furnace arch severe scouring ultra-high temp zone |
SS420 high-carbon martensitic stainless steel has strict standardized welding requirements; following operation specifications can effectively avoid cold crack defects and extend tube shield overall service life:
1. Hoisting & transportation handling rule: Avoid violent knocking, extrusion and impact on SS420 shield plate surface during loading and installation, to prevent invisible stamping microcracks on semicircular arc body.
2. Welding operation mandatory specification: Preheat workpiece to 320 ~ 400°C before spot welding construction, adopt special martensitic stainless welding rod, implement slow air cooling treatment after welding to eliminate welding residual stress and cold cracks.
3. Snap ring clamping installation inspection point: Ensure full seamless fitting between SS420 half round shield and heat transfer tube outer wall, symmetrically lock C/U snap rings on both sleeve ends to prevent shield sliding displacement under long-term flue gas vibration impact.
4. Annual boiler shutdown overhaul inspection item: Check SS420 plate wall thinning thickness and welding crack propagation status, replace severely worn and cracked shields in advance to prevent base heat transfer tube abrasion perforation leakage accidents.
5. Warehouse finished product storage protection: Stack SS420 tube shields with isolation paper between layers, seal warehouse space with dehumidification measures to avoid surface moisture rust before shipment delivery.
The structural shape and chemical alloy formula of our SS420 half round tube erosion shields are fully optimized targeting medium abrasion low-temperature low-sulfur economizer boiler flue working conditions:
1. One-piece integral hydraulic stamping semicircular U-shaped structure eliminates assembly splicing gaps, completely avoid ash accumulation and localized concentrated abrasion defects commonly seen in segmented tile-spliced protective covers.
2. High-carbon 12~14Cr martensitic formula balances moderate raw material cost and high post-heat-treatment hardness, providing cost-effective medium anti-abrasion solution for mass boiler tube bundle transformation projects that cannot use SS410 due to heavier fly ash impact.
3. Interchangeable multi-type structural variants (straight half wrap, fin inter-tube baffle, outer U-bend full cover) cover all mainstream low-temperature heating surface layout designs, eliminating secondary on-site cutting and transformation work for most standard boiler tube bundles.
4. Uniform consistent alloy plate thickness design guarantees synchronous wear speed across the whole SS420 shield surface, avoiding partial premature plate thinning under uneven fly ash particle impact distribution inside boiler flues.
We provide full customized SS420 half round tube shield manufacturing service strictly against customer boiler overhaul construction drawings, flue operating temperature and fly ash abrasion intensity technical parameters:
Customizable core technical parameters: Matched heat transfer tube outer diameter, SS420 alloy plate thickness, half round shield total length, semicircular arc radian, wave fin baffle height, outer U-bend wrap coverage angle.
Special customized optional solutions: Extra thick enhanced wear-resistant SS420 alloy plate, oversized outer U-bend full wrap shield, pre-assembled integrated shield + snap ring assembly for fast on-site installation.
Attached professional technical supporting service: Boiler low-temperature medium-abrasion flue anti-wear scheme consultation, on-site welding construction technical guidance, long-term bulk spare parts supply framework contract for thermal power plant annual maintenance cycles.
420 stainless steel half round tube shields adopt layered isolation shockproof packaging design to protect stamped semicircular arc structure from extrusion deformation damage during cross-border sea and land long-distance transportation:
Small batch small-size SS420 shields separated by foam isolation paper and packed into fumigated export wooden cases; large quantity bulk finished products stacked on standard steel pallets, fixed with steel binding strips, whole pallet outer layer wrapped anti-rust stretch plastic film for moisture isolation.
Multiple international trade terms FOB / CFR / CIF are fully supported, sea freight and land highway transportation options available according to customer designated delivery port and delivery schedule time requirements.
Each shipment batch attached complete full set delivery documents: SS420 material spectral composition test report, dimensional inspection record, on-site installation operation manual, convenient for overseas power plant project customs clearance and equipment acceptance inspection work.
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When you partner with Sunny Steel, you can stop worrying about meeting deadlines thanks to our responsive and timely service. You'll also say goodbye to unnecessary shopping around. Instead, you'll get white glove service from an expert who understands your needs and can get you the materials you need quickly.
