Hitachi cranes typically use programmable logic controller (PLC)-based control systems combined with dedicated crane safety electronics, including load moment indicators, anti-two-block devices, and operator display units. These systems manage lifting operations by continuously monitoring load, angle, and boom geometry to keep the crane within its rated capacity. The sections below explore each major component of Hitachi crane control systems in detail.
What types of control systems do Hitachi cranes typically use?
Hitachi cranes typically use a layered control architecture that combines PLC-based machine control with dedicated crane safety electronics. The PLC governs motion sequences, hydraulic valve commands, and operator inputs, while a separate safety layer handles load monitoring, anti-two-block protection, and rated capacity management. Together these layers ensure both operational precision and regulatory compliance.
The specific configuration varies by crane model and application, but most Hitachi lattice boom and hydraulic cranes share a common set of control components:
- Main PLC or microcontroller unit: Processes sensor inputs, executes motion logic, and communicates with the operator display
- Rated capacity indicator (RCI) or load moment indicator (LMI): Continuously calculates the relationship between actual load and the crane’s rated capacity at any given configuration
- Anti-two-block (ATB) device: Prevents the hook block from contacting the boom tip by cutting motion when the limit is reached
- Angle and length sensors: Measure boom elevation and extension to feed real-time geometry data into the capacity calculation
- Pressure transducers: Monitor hydraulic pressure at the lift cylinder to derive load values
- Operator display unit: Presents load percentage, boom angle, radius, and alarm status to the crane operator
On larger or more modern Hitachi models, the control system may also include CAN bus communication between subsystems, enabling faster data exchange and more sophisticated diagnostics. Offshore and heavy-lift variants often incorporate additional redundancy, with dual sensors and independent safety channels to meet class society requirements.
How does a load moment indicator work on a Hitachi crane?
A load moment indicator on a Hitachi crane works by continuously comparing the actual load moment, which is the product of the lifted load and its horizontal distance from the crane’s slewing centre, against the crane’s rated capacity chart for the current configuration. When the actual moment approaches the rated limit, the LMI triggers audible and visual alarms and can cut crane motion to prevent overload.
The calculation relies on several real-time inputs gathered simultaneously:
- Load measurement: Derived from hydraulic pressure at the lift cylinder or from a load pin in the hook suspension
- Boom angle: Measured by an inclinometer or angle sensor mounted on the boom
- Boom length: Measured by a cable-drum length sensor or encoder on telescoping booms
- Jib or fly configuration: Entered manually or detected automatically depending on the system
Using boom angle and length, the system calculates the working radius, which is the horizontal distance from the crane centre to the load. Multiplying the measured load by this radius gives the actual load moment. The system then looks up the rated capacity for that radius and configuration from an internal chart stored in the controller’s memory.
Most LMI systems display the result as a percentage of rated capacity rather than raw moment values, making it immediately intuitive for operators. A reading of 90% signals that the crane is approaching its limit; a reading above 100% triggers a cut-out that stops hoist-up and boom-down motions. This prevents structural stress from exceeding design parameters and protects both the crane and the load.
What safety systems are built into Hitachi crane control units?
Hitachi crane control units incorporate multiple independent safety systems that work in parallel to protect the crane, the load, and personnel on site. These include load moment limiting, anti-two-block protection, slewing and travel limit switches, wind speed monitoring on larger machines, and emergency stop circuits that cut all powered motion immediately.
Load and structural protection systems
The load moment indicator or rated capacity indicator forms the primary structural protection layer. It monitors the relationship between actual load and rated capacity in real time and initiates a motion cut-out before the crane reaches an overload condition. Separate overload relays may provide a secondary cut at a defined threshold above the rated capacity as a final backstop.
Pressure relief valves in the hydraulic circuit complement the electronic safety systems by providing a purely mechanical limit on lift cylinder pressure, ensuring that even a complete electronic failure cannot result in structural overload through the hydraulic path.
Motion and position protection systems
Anti-two-block devices use a weight-and-switch assembly hanging from the boom tip. When the hook block rises close enough to contact the weight, the circuit opens and cuts hoist-up motion. This prevents the wire rope from being pulled over the sheave, which can cause catastrophic rope failure.
Slewing limit switches restrict the crane’s rotation arc when operating near structures or in confined areas. Boom angle limit switches prevent the boom from being raised beyond its maximum design angle or lowered below the minimum working angle, both of which can compromise structural integrity or stability.
Can Hitachi crane control systems be upgraded or replaced?
Yes, Hitachi crane control systems can be upgraded or replaced, and doing so is a common practice when original equipment becomes obsolete, spare parts are no longer available, or operational requirements have changed. Modern replacement systems are designed to interface with the crane’s existing sensor wiring and hydraulic valves, minimising the need for mechanical modifications.
Several scenarios typically drive an upgrade decision:
- The original LMI or RCI manufacturer has discontinued support for the installed model
- The crane is being recertified or re-rated for a different capacity or configuration
- The operator requires additional functionality such as data logging, remote monitoring, or anti-collision integration
- Sensor technology has advanced to the point where accuracy and reliability improvements justify the investment
When replacing a control system, the new unit must be calibrated against the crane’s actual structural capacity chart, not simply swapped in with generic settings. This calibration process involves load testing at known weights across multiple radii and configurations to verify that the system’s readings align with actual conditions. Documentation of this process is typically required by the relevant inspection authority or classification society.
Retrofitting also provides an opportunity to add capabilities that were not available when the crane was originally built, such as wireless data transmission, GPS-based anti-collision, or ATEX-certified sensors for use in hazardous areas.
What is the difference between a safe load indicator and a load moment indicator on a crane?
A safe load indicator (SLI) measures and displays the actual lifted load and compares it to a fixed rated capacity, triggering an alarm when the load approaches or exceeds that limit. A load moment indicator (LMI) goes further by calculating the load moment, which accounts for both the weight of the load and its distance from the crane centre, and compares that moment against a variable rated capacity that changes with boom angle, length, and configuration.
The practical difference is significant in variable-radius operations:
- Safe load indicator: Suitable for cranes with a fixed working radius or where the rated capacity does not change with configuration. It answers the question: “Is the load too heavy?”
- Load moment indicator: Required for cranes where the safe working load changes with radius and boom geometry. It answers the question: “Is the combination of load and radius within the crane’s rated capacity for this configuration?”
A crane can lift a load that is well within its maximum rated capacity in terms of weight, yet still exceed its structural limits if that load is lifted at a large radius. An SLI would not detect this condition; an LMI would. For this reason, most mobile cranes, crawler cranes, and offshore pedestal cranes are required to be fitted with an LMI rather than a basic SLI. Hitachi’s larger hydraulic and lattice boom cranes fall into this category and are equipped accordingly.
How do anti-collision systems integrate with Hitachi crane controls?
Anti-collision systems integrate with Hitachi crane controls by connecting to the crane’s motion control circuit, typically at the same point as the safety cut-out from the load moment indicator. When the anti-collision system detects that the crane is approaching a defined exclusion zone or another crane, it sends a signal to the control unit that slows or stops the relevant motion before a collision occurs.
The integration method depends on the technology used:
- Zone-based radar or ultrasonic systems: Sensors mounted on the boom detect obstacles within a set distance and trigger a slow-down zone followed by a stop zone
- GPS or total station-based systems: The crane’s position and slewing angle are tracked in real time and compared against a digital map of exclusion zones, such as building facades, power lines, or adjacent crane working areas
- Crane-to-crane communication systems: Multiple cranes on a shared site exchange position data wirelessly, and the system calculates potential collision trajectories before they occur
From the control system’s perspective, the anti-collision output is treated as an additional safety input alongside the LMI and ATB signals. When the signal is active, the relevant motion, whether slewing, hoisting, or luffing, is inhibited or restricted. On more sophisticated installations, the system can provide proportional slow-down rather than a hard stop, reducing shock loads and improving operational efficiency.
Effective integration requires that the anti-collision system’s coordinate reference matches the crane’s actual slewing centre and boom geometry, which is established during commissioning through a calibration process specific to each installation.
What data logging and remote monitoring options exist for Hitachi crane systems?
Hitachi crane systems can be equipped with data logging and remote monitoring solutions that record operational parameters over time and make that data accessible from off-site locations. Logged data typically includes load values, boom angle and length, slewing position, operating hours, alarm events, and wind speed where applicable. This information supports maintenance planning, incident investigation, and regulatory reporting.
Data logging can be implemented at several levels depending on the requirement:
- Local logging: Data is stored on an SD card, USB drive, or internal memory within the control unit and retrieved physically during inspections
- Cloud logging: Data is transmitted over a cellular or satellite connection to a secure cloud platform, enabling access from any internet-connected device
- Wireless local logging: Data is transmitted wirelessly within the site, typically with a range suited to yard or port environments, to a local server or gateway
Remote monitoring extends data logging by providing live visibility of crane status, active alarms, and current load conditions without requiring personnel to be physically present at the crane. This is particularly valuable for fleet managers overseeing multiple machines across different sites, or for engineering teams providing remote technical support.
Mobile application readout and Windows-based software platforms are common interfaces for accessing logged and live data, allowing operators and supervisors to review trends, export reports, and set threshold alerts that notify them when specific parameters are exceeded.
How PAT-Krüger supports Hitachi crane control systems
We design, manufacture, and install control and safety solutions that work with Hitachi cranes across a wide range of applications, from onshore construction to offshore heavy lift. Whether you need to replace an obsolete load moment indicator, add anti-collision capability, or implement a full remote monitoring setup, we provide purpose-built systems calibrated to your crane’s specific configuration and capacity chart.
Our solutions for Hitachi crane applications include:
- Load moment indicators and rated capacity indicators calibrated to Hitachi structural capacity charts
- Custom-fabricated force sensors and load pins designed to fit existing hook suspensions and boom tip geometry
- Crane anti-collision systems that integrate directly with the crane’s motion control circuit
- ATEX-certified sensors and control units for Hitachi cranes operating in hazardous area classifications
- Cloud and local data logging with mobile app and Windows software access for load and wind speed monitoring
- Remote monitoring via secure private cloud for live operational visibility and alarm management
- Worldwide installation, calibration, and maintenance services backed by a global spare parts inventory
We work closely with crane owners, operators, and inspection authorities to ensure that every system we deliver meets the relevant safety standards and is fully documented for certification purposes. If you are looking to upgrade, replace, or expand the control and safety systems on your Hitachi crane, contact our team to discuss your requirements and receive a solution tailored to your specific crane and operating environment.
Frequently Asked Questions
How often should a Hitachi crane's load moment indicator be recalibrated?
An LMI should be recalibrated whenever the crane undergoes a structural modification, re-rating, or major repair, and as a minimum it should be verified during each scheduled inspection cycle — typically annually or as required by the relevant inspection authority. Calibration involves load testing at known weights across multiple radii to confirm the system's readings match actual conditions. If the crane has been relocated to a new site or fitted with a different attachment configuration, a recalibration check is also advisable before commencing lifting operations.
What should an operator do if the LMI display shows an error code or goes blank during a lift?
If the LMI display shows an error code or loses power during a lift, the operator should immediately stop all crane motion, secure the load in its current position, and avoid any further lifting, luffing, or slewing until the fault is diagnosed. Most Hitachi control systems are designed to default to a safe state on sensor or communication failure, but this should never be assumed without verification. The error code should be recorded and reported to a qualified technician who can trace the fault to a specific sensor, wiring connection, or controller module before operations resume.
Can a Hitachi crane's control system be integrated with a site-wide lift planning or fleet management platform?
Yes, modern Hitachi crane control systems equipped with cloud data logging can be integrated with third-party lift planning and fleet management platforms via API connections or standardised data export formats. This allows load data, alarm events, and operating hours to feed directly into site management software for real-time oversight and reporting. The specific integration approach depends on the platform in use, so it is worth confirming compatibility with your control system supplier during the specification stage.
What are the most common causes of false overload alarms on crane load moment indicators?
False overload alarms are most commonly caused by dynamic load effects during fast hoisting or sudden stops, which create momentary pressure spikes that the system reads as an elevated load. Other frequent causes include a misconfigured capacity chart in the controller's memory, a drifting or damaged pressure transducer, or an angle sensor that has lost its calibration reference point. Checking sensor readings against known static loads and reviewing the controller's configuration settings are the first diagnostic steps when false alarms occur repeatedly.
Is it possible to add ATEX-certified safety systems to a Hitachi crane that was not originally built for hazardous area use?
Yes, Hitachi cranes can be retrofitted with ATEX-certified sensors, control units, and wiring systems to meet hazardous area classification requirements, provided the retrofit is designed and documented by a qualified supplier familiar with both the crane's existing architecture and the applicable ATEX directives. The process typically involves replacing non-certified sensors with ATEX-rated equivalents, installing certified junction boxes and cable glands, and producing the necessary conformity documentation for the relevant certifying authority. This type of retrofit is common when cranes originally deployed onshore are reassigned to offshore or petrochemical environments.
What is the difference between a hard cut-out and a proportional slow-down in a crane safety system, and which is better?
A hard cut-out instantly stops the relevant crane motion when a safety threshold is reached, while a proportional slow-down progressively reduces motion speed as the crane approaches the limit, transitioning to a full stop only at the boundary. Proportional slow-down is generally preferred in operational terms because it reduces shock loads on the structure and the suspended load, and gives the operator a clearer physical indication that a limit is near. Hard cut-outs remain the standard for final safety boundaries such as anti-two-block and structural overload protection, where there is no tolerance for motion beyond the threshold.
How is a Hitachi crane control system affected when switching between different boom or jib configurations?
When a Hitachi crane changes configuration — for example, switching from a main boom to a main boom with fly jib — the control system must be updated to reflect the new geometry and load chart applicable to that configuration. On manually configured systems, the operator selects the correct configuration from a menu on the display unit before commencing operations; on more advanced systems, configuration changes may be detected automatically through sensor inputs. Using the wrong capacity chart for the installed configuration is one of the most serious operator errors possible, as it can cause the LMI to permit lifts that actually exceed the crane's structural limits for that setup.