In modern steel rolling mills, unexpected incidents—such as bar breakage, guide misalignment, or roll jamming—can cause severe damage to downstream equipment if not addressed immediately. To mitigate such risks, specialized safety devices are installed at critical points in the production line. من بين هؤلاء, ال flying shear for accidents plays a vital role in protecting high-value machinery like pre-finishing and finishing mills. HANI Intelligent Products has developed a robust, reliable solution tailored precisely for this purpose.
What Is a Flying Shear for Accidents?
Often referred to as an emergency cut-off shear or gripping shear, this device is strategically positioned between the pre-finishing and finishing stands in a hot strip or bar rolling mill. Its primary function is simple yet critical: to instantly sever the incoming hot steel bar during an emergency, preventing it from entering sensitive downstream equipment.
Unlike conventional flying shears used for length cutting, this type of shear isn’t designed for precision trimming—it’s built for speed, مصداقية, and brute-force interruption. When a fault occurs upstream (على سبيل المثال, a broken bar looping into the mill), the system triggers within milliseconds, clamping and tearing the moving billet apart using its own kinetic energy.
كيف يعمل: Simplicity Meets Efficiency
The design follows a dual-blade, scissor-like mechanism:
- One blade is mounted above the rolling line.
- The other is positioned directly below.
- Both blades remain retracted during normal operation to avoid interference.
- Upon emergency signal, a pneumatic cylinder actuates, driving a linkage system that forces both blades to close simultaneously onto the moving bar.
بشكل حاسم, the shear doesn’t rely on sharp cutting edges alone. بدلاً من, it exploits the high-speed motion of the hot steel (typically traveling at 5–15 m/s). As the blades clamp down, the bar’s forward momentum generates immense tensile stress at the pinch point, causing it to fracture cleanly—a process known as “tearing by self-propulsion.” This method eliminates the need for massive hydraulic force or complex synchronization.
Key Technical Specifications
HANI’s flying shear for accident protection is engineered for harsh mill environments. Below are verified performance parameters based on real-world installations:
| المعلمة | قيمة / يتراوح |
|---|---|
| Applicable steel grades | الصلب الكربوني, low-alloy steel (على سبيل المثال, Q235, SS400, ساي 1045) |
| Operating temperature | >950درجة مئوية (typical exit temp from roughing mill) |
| Pneumatic cylinder size | Φ100/Φ32 × 240 مم (double-acting) |
| Air pressure requirement | 0.4 - 0.6 الآلام والكروب الذهنية (standard plant air supply) |
| Response time | ≥ 0.3 seconds from signal to full closure |
| Max bar speed at shear point | حتى 12 آنسة (depending on mill layout) |
| Frame construction | Welded steel base with stress-relieved structure |
Design Features That Matter in Real Operations
Field experience shows that reliability under extreme conditions is non-negotiable. HANI’s design incorporates several practical enhancements:
Robust Mechanical Structure
The entire assembly sits on a heavy-duty welded base, minimizing vibration and ensuring alignment stability over years of thermal cycling. The shear body uses hardened tool steel for blades, with replaceable inserts to reduce maintenance downtime.
Smart Lubrication Strategy
To survive in a high-heat, high-dust environment, the system avoids complex oil circuits. بدلاً من:
- Pivot points on the blade arms use sintered bronze oil-impregnated bushings—maintenance-free for thousands of cycles.
- All other joints (linkages, pins) are fitted with grease nipples for manual lubrication during scheduled stops.
This hybrid approach balances longevity with service simplicity—no pumps, filters, or leak-prone lines.
Pneumatic Actuation: Why Air Over Hydraulics?
While hydraulic systems offer higher force, they introduce complexity: oil leaks, temperature sensitivity, and slower response in cold starts. In contrast, plant-compressed air is already available throughout most mills. Using a standard Φ100 cylinder at 0.5 MPa delivers ~3,900 N of thrust—more than enough to clamp a red-hot bar when combined with mechanical leverage. Plus, air systems reset faster and pose no fire risk near hot steel.
تثبيت & Integration Tips
For optimal performance, consider these field-proven guidelines:
- تحديد المواقع: Install 1.5–2 meters upstream of the first finishing stand. This provides enough clearance for the severed head-end to drop safely without jamming.
- تنسيق: Ensure the shear centerline matches the rolling axis within ±1 mm. Misalignment causes uneven blade wear and incomplete cuts.
- Control Logic: Integrate the shear trigger with multiple fault signals—e.g., motor overload, loop detector activation, or emergency stop buttons. Use redundant sensors to avoid false negatives.
- Cooling Protection: Shield the cylinder and linkages with refractory curtains or water-cooled jackets if ambient radiation exceeds 150°C.
Maintenance Checklist for Long-Term Reliability
Even the toughest equipment needs care. Follow this routine:
| Task | Frequency | ملحوظات |
|---|---|---|
| Inspect blade wear | أسبوعي | Replace if edge chipping >3 mm or gap >1 mm when closed |
| Lubricate pivot joints | كل 2 weeks | Use high-temp lithium grease (NLGI #2) |
| Check air filter & regulator | شهريا | Drain condensate; verify pressure stability at 0.5 الآلام والكروب الذهنية |
| Test emergency trigger | ربع سنوية | Simulate fault signal; confirm full closure within 0.3 ق |
When properly maintained, this system can operate reliably for over 5 years without major overhaul—providing peace of mind and significant cost savings by preventing catastrophic mill damage. In one documented case at a 600,000-ton/year bar mill, the installation of HANI’s flying shear for accidents reduced unplanned downtime by 18% in the first year alone, primarily by avoiding roll pass destruction during bar breaks.
For mill engineers and operations managers, investing in a well-designed emergency shear isn’t just about hardware—it’s about building resilience into the production line. And in an industry where every minute of downtime costs thousands, that resilience pays for itself many times over.
