Truck cranes are the workhorses of urban construction, logistics yards, and utility maintenance. They lift, reach, and relocate heavy loads in tight spaces where a single miscalculation can cost lives, equipment, and project schedules. A Load Moment Indicator (LMI) transforms that risk into a controlled, measurable workflow by continuously monitoring the crane’s working radius, boom angle, boom length, and actual load—and stopping dangerous motions before they become accidents.
At Yichang Seezol Technology Co., Ltd. (www.szlmi.com), we engineer LMI systems that meet the real-world demands of truck crane operators. The SZ-TC01 truck crane LMI is built around a 7-inch color display, dual pressure sensors, a combined length/angle sensor, an A2B height limit switch, and a three-color status light. It is designed to satisfy ISO 10245, GB/T 12602, and EN 13000 requirements, giving fleet owners, rental companies, and OEMs a compliance-ready safety layer that installs in hours, not days.
What the SZ-TC01 Truck Crane LMI Actually Does
The SZ-TC01 is not just an overload alarm. It is an integrated electronic safety system that calculates the actual load moment in real time and compares it against the crane’s rated load chart. When the system detects that the working load is approaching the limit, it triggers visible and audible warnings. If the operator continues into an overload condition, the LMI outputs relay signals that interface with the crane’s control circuit and stop hazardous motions—typically hoisting upward—while still allowing the operator to move the load to a safe position.
The complete SZ-TC01 kit — display host, dual pressure sensors, length/angle sensor, A2B limit switch, three-color light and shielded cabling.
The core sensor set includes:
- Two hydraulic pressure sensors: installed on the rod and rodless sides of the luffing cylinder to derive boom force.
- One length/angle sensor: measures boom extension and boom angle, which are essential for calculating radius and load capacity.
- One A2B height limit switch: protects against over-hoisting by detecting when the hook block reaches the boom head.
- One three-color stack light: provides at-a-glance status indication in the cab or on the roof.
- 7-inch display host: presents real-time load, radius, boom length, boom angle, rated load, and sensor health.
Because the system uses a DC 12–36 V power supply and consumes less than 10 W, it integrates easily into the existing electrical architecture of most truck cranes without requiring a dedicated generator or inverter.
Verified Technical Specifications
The following figures are taken directly from the SZ-TC01 installation and commissioning manual (document SZ-TC01251101, issued November 2025):
| 参数 | 规格 |
| 工作电压 | DC 12–36 V |
| 工作温度 | -30 °C to +80 °C |
| Relative humidity | < 95 % at 25 °C |
| Operating mode | Continuous |
| Total power consumption | < 10 W |
| Control output capacity | 2 A @ AC 220 V / 10 A @ AC 36 V |
| Overall system error | ≤ ±5 % |
| Alarm error | ≤ ±5 % |
| Display | 7-inch colour touchscreen |
| Sensor configuration | 2 × pressure, 1 × length & angle, 1 × A2B switch |
| Relay outputs | Overload, small-angle limit, large-angle limit |
A ±5 % system error is the practical working tolerance for hydraulic-pressure-based LMI systems on telescopic boom truck cranes. It is important to state this honestly: an LMI of this architecture is a protective and advisory instrument, not a legal-for-trade weighing scale. Operators should continue to follow the crane manufacturer’s load chart and site safety procedures.
Key Functional Advantages
In-cab display: live load, radius, boom angle and boom length on one screen, with blue / amber / red status colouring.
1. Real-Time Load Visualization
The color display shows a graphical truck crane icon, current boom length, boom angle, working radius, actual load, and rated load in one screen. Load values turn blue in normal operation, yellow at pre-warning, and red when overload protection activates. Operators no longer need to estimate capacity from paper charts or memory.
2. Automatic Overload Interlock
When actual load exceeds 100 % of rated capacity (user-adjustable threshold), the LMI closes the control relay and prevents further dangerous movement. The release threshold is configurable—for example, control resets only when load falls below 98 % of rated load—preventing chattering and unnecessary downtime.
3. Angle Limit Protection
Upper and lower boom angle limits can be set to trigger independent relay outputs. This is useful for cranes working on slopes, near overhead lines, or in confined spaces where geometry itself becomes a hazard.
4. High Environmental Tolerance
The system is rated for -30 °C to +80 °C operating temperature and <95 % relative humidity at 25 °C. That range covers desert heat, freezing yards, and humid coastal sites without reliability degradation.
5. Strong Anti-Interference Design
The SZ-TC01 uses a large-scale integrated circuit platform and shielded aviation connectors. Sensor cabling can be routed through corrugated tubing for additional protection against vibration, oil, and dust.
6. Straightforward 9-Step Calibration
Version 5.0 software streamlines commissioning into nine ordered steps: parameter entry, angle calibration, length calibration, optional radius calibration, empty-hook sampling, automatic calculation, load calibration, control setting, and load correction. Each step is password-protected, so calibrated data cannot be accidentally modified by untrained personnel.
应用场景
The SZ-TC01 is designed for truck-mounted cranes, also known as boom trucks or lorry cranes, used in:
- Urban infrastructure: lifting precast panels, transformers, and signage where space and clearance are tight.
- Rental fleets: protecting machines operated by different drivers with varying experience levels.
- Utility maintenance: telecom and power-line work that requires precise load placement at extended radii.
- Logistics and material handling: loading and unloading heavy cargo in yards and industrial plants.
- OEM integration: crane manufacturers who need a CE/EN 13000-aligned safety system on new builds.
Because the LMI is programmable for boom geometry, it adapts to single-boom and two-section boom truck cranes commonly found in the 2-ton to 16-ton lifting class.
Cost-Effectiveness: Safety as an Investment
A single overturn incident can exceed the cost of dozens of LMI systems when accounting for crane damage, third-party liability, project delays, and insurance premium increases. The SZ-TC01 offers a different equation: predictable upfront cost, low operating power, and minimal maintenance.
| Item | Without LMI | With SZ-TC01 LMI |
| Overload/ overturn risk | High; dependent on operator judgment | Controlled by continuous monitoring and automatic interlock |
| Compliance | Manual documentation; harder to prove due diligence | Aligned with ISO 10245, GB/T 12602, EN 13000 |
| Operator training burden | Heavy; must memorize load charts | Reduced; visual display guides safe operation |
| Downtime after incident | Days to weeks for investigation/repair | Minutes; reset after correcting the overload |
| Power draw | None | <10 W continuous |
| Typical maintenance | Ad hoc | Scheduled 3–6 month accuracy check |
| Warranty / support | N/A | 12 months (non-human damage); free remote installation assistance |
The system ships within 15 working days after payment, and SeeZol provides free remote installation assistance. That means most customers can go from order to protected operation in under a month, with no specialized service engineer required on site.
Installation and Commissioning
Sensor layout on a truck crane: pressure sensors on the luffing cylinder, length/angle sensor on the boom, A2B switch at the boom head, display in the cab, warning light on the roof.
Installation is quick and follows the crane’s existing geometry—no structural modification needed. Sensors bolt onto the luffing cylinder, boom, and boom head; the display drops into the cab and the warning light onto the roof. Mechanical fitting takes about half a day, and the guided nine-step software calibration finishes the same day. Most customers go from unboxing to protected operation within one working day, with no specialist engineer required on site.
Maintenance and Troubleshooting
Maintenance is minimal by design. Daily checks take only seconds, system accuracy needs re-verification just every 3–6 months, and all sensors connect through standard aviation plugs—so a faulty unit can be swapped in the field without replacing the whole system. The main unit and sensors are factory-calibrated and sealed, and SeeZol provides free remote diagnosis whenever a fault cannot be cleared on site.
常见问题
Can the SZ-TC01 be retrofitted to an older truck crane?
Yes. The system does not depend on the crane’s original electronics. As long as the luffing cylinder can accept pressure sensor fittings and the boom can carry a length/angle sensor, the LMI can be retrofitted. Commissioning simply requires measuring the crane’s structural dimensions and running the nine-step calibration.
How long does installation and commissioning take?
Mechanical installation typically takes half a day. Calibration adds a few hours because the empty-hook sampling routine requires the operator to move the boom through several length and angle combinations. Most single-crane installations are completed within one working day.
Does the LMI stop the crane completely during overload?
No. It interrupts motions in the dangerous direction only. The operator retains the ability to lower the load or retract the boom to return to a safe condition, at which point the interlock releases automatically once the load drops below the reset threshold.
What happens if a sensor fails?
The signal-viewing screen shows live values for every sensor channel. A dead or erratic channel is visible immediately. Because sensors are connected through standard aviation connectors, a faulty unit can be swapped without replacing the whole system—though recalibration of the affected channel is required.
Is the system suitable for cranes working near power lines?
The angle limit outputs can be configured to restrict boom movement into defined zones, which helps with clearance management. However, an LMI is not a proximity warning device. Sites working near live conductors should also deploy dedicated insulation monitoring or proximity alarm equipment.
How often should accuracy be verified?
Every three to six months, with written records retained. Recalibration is also required whenever boom configuration, hook block, or reeving is changed.
结论
The SZ-TC01 truck crane Load Moment Indicator is more than a regulatory checkbox. It is a decision-support and protection system that lets operators work faster, managers sleep better, and fleet owners demonstrate due diligence. With wide voltage input, harsh-environment tolerance, automatic overload interlock, and a calibration workflow designed for field technicians, it delivers safety and productivity in the same package.
To request specifications, pricing, or a remote installation plan, visit www.szlmi.com or contact 宜昌思卓科技有限公司 directly.
About the Manufacturer
Yichang Seezol Technology Co., Ltd. designs and manufactures load moment indicators, load limiters, and onboard weighing systems for construction and material-handling machinery. Our product range covers truck cranes, mobile cranes, crawler cranes, articulated boom cranes, excavators, loaders, forklifts, telehandlers, and reach stackers. Each system is supplied with a bilingual installation and commissioning manual, and every unit is factory-calibrated before shipment.
Product reference for this article: SZ-TC01 Truck Crane Load Moment Indicator, installation and commissioning manual, document number SZ-TC01251101, issued November 2025. All technical parameters, calibration thresholds, warranty terms, and troubleshooting procedures cited above are drawn from that document.
披露： This article is published by the manufacturer of the product described. Specifications are accurate as of the manual issue date and may be revised without notice. Figures such as installation time are typical values based on field experience and will vary with crane model, boom configuration, and site conditions.
Standards referenced: ISO 10245 (Cranes — Limiting and indicating devices), GB/T 12602 (Overload protection devices for lifting appliances), EN 13000 (Cranes — Mobile cranes). Buyers should confirm the specific certification requirements applicable in their own market before purchase.
Last reviewed: August 2026
Product: SZ-TC01 Truck Crane Load Moment Indicator
Document No.: SZ-TC01251101
Issued: November 2025
Manufacturer: Yichang Seezol Technology Co., Ltd. — www.szlmi.com
