Electronics Guide

Ship-to-Shore Container Cranes

Modern ship-to-shore (STS) container cranes use electric drives for all major motions including hoist, trolley, and gantry travel:

Main hoist drives: Container crane hoists raise loads of 40-80 tonnes at speeds up to 180 meters per minute, requiring drive power ratings from 1 to 4 MW depending on crane size. These drives operate continuously during cargo operations, generating electromagnetic interference throughout the working period. The hoist motor cables, which can be 100 meters or more long depending on trolley position, act as effective antennas for radiated emissions.

Trolley and gantry drives: While individually smaller than hoist drives, the trolley and gantry drives add to the aggregate electromagnetic emissions from the crane. The gantry drive moves the entire crane along the quay, with drives that must handle both the acceleration of the crane mass and wind loads.

Spreader and twist-lock systems: The container spreader includes motors and sensors for positioning and twist-lock engagement. These systems use control signals that must function reliably in the electrically noisy environment near the main hoist drives.

Container cranes operating near berthed vessels can affect shipboard electronics. Ships have reported GPS degradation, communication interference, and radar anomalies while under crane. The close proximity of the crane boom to ship antennas during cargo operations creates challenging coupling conditions.

Rubber-Tired Gantry Cranes

Rubber-tired gantry (RTG) cranes work in container storage yards:

Traditional diesel-electric RTGs generate power on board using diesel generator sets. The generator's power electronics and the crane's drive systems create an electromagnetic environment similar to a ship's engine room, with all the associated EMC challenges contained within the crane structure.

Electric RTGs (eRTGs) receive power from the port grid through cable reel or conductor bar systems. The long power connections can propagate conducted emissions from the crane into the port electrical network, potentially affecting equipment throughout the terminal. Conversely, electrical noise on the port supply can affect crane control systems.

Automated RTGs (ARTGs) use positioning systems including differential GPS, optical sensors, and sometimes radar for container location and crane guidance. These systems must operate correctly despite the electromagnetic emissions from the crane's own drives.

Automated Stacking Cranes

Rail-mounted gantry cranes in automated terminals operate without operators:

Automated stacking cranes (ASCs) rely entirely on electronic sensors and control systems for all operations. Position sensing, obstacle detection, container identification, and communication with the terminal operating system must all function reliably in the presence of electromagnetic interference from the crane drives and adjacent equipment.

The communication links between ASCs and the terminal control system typically use radio or optical systems. Radio links operating at 900 MHz, 2.4 GHz, or 5 GHz must coexist with other wireless systems in the terminal and must resist interference from crane power electronics.

Safety systems including collision avoidance and emergency stop functions must maintain high reliability despite the electromagnetic environment. These systems are typically designed to Safety Integrity Levels (SIL) with appropriate attention to EMC as part of the functional safety assessment.

Crane EMC Mitigation

Reducing electromagnetic emissions from container cranes requires attention throughout the crane design and installation:

Drive filtering: Input line filters and output sinusoidal filters reduce conducted and radiated emissions from VFDs. dV/dt filters protect motor insulation while reducing the high-frequency content of motor cable emissions.

Shielded cables: Motor cables should use properly terminated shields to contain radiated emissions. The shield termination at both the drive and motor ends must provide 360-degree connection for effectiveness at high frequencies.

Grounding and bonding: A comprehensive grounding system ties all crane metalwork together, providing return paths for interference currents and reducing voltage differences between equipment. The connection between the crane and port ground system is particularly important for cranes that receive shore power.

Enclosure integrity: VFD equipment enclosures should be designed for good EMC performance with proper treatment of cable entries and ventilation openings.

Optical Character Recognition

OCR systems automatically read container identification numbers:

Gate OCR systems photograph containers entering and leaving the terminal, with image processing software extracting the container number and other markings. The cameras and image processing equipment operate in the electromagnetic environment created by terminal operations and passing vehicles.

Crane OCR systems mounted on STS cranes read container numbers during loading and discharge. These systems must function correctly despite the electromagnetic fields from the crane's drives and the radio communications between the crane and the terminal operating system.

High-intensity lighting for OCR systems can generate electromagnetic interference from the lamp ballasts or LED drivers. The lighting system design should consider EMC implications.

RFID and Electronic Seals

Radio frequency identification technologies support container security and tracking:

RFID readers at terminal gates query electronic seals on containers to verify seal integrity. The readers must reliably communicate with tags on containers passing through the gate at normal traffic speeds despite interference from terminal equipment and vehicle electronics.

Some terminals use RFID for equipment identification and tracking. Tags on chassis, trucks, and handling equipment support logistics optimization. These systems operate at frequencies including 125 kHz, 13.56 MHz, 900 MHz, and 2.4 GHz, each with different EMC characteristics and susceptibilities.

Real-time location systems (RTLS) using active RFID or ultra-wideband technology track containers and equipment throughout the terminal. The wireless signals must coexist with other terminal radio systems and must resist interference from crane VFDs and other industrial equipment.

Terminal Operating Systems

The terminal operating system (TOS) coordinates all cargo handling activities:

TOS servers in the terminal control center communicate with equipment throughout the terminal. Network infrastructure including switches, routers, and wireless access points must provide reliable communication despite the terminal's electromagnetic environment.

Mobile data terminals on vehicles receive work instructions and report completions. Vehicle-mounted equipment must withstand vibration and environmental exposure while maintaining reliable wireless communication in the presence of interference sources.

Hand-held devices used by tally clerks, planners, and maintenance staff connect wirelessly to the TOS. These devices operate throughout the terminal in varying electromagnetic conditions.

Automated Guided Vehicles

Some automated terminals use driverless vehicles for horizontal transport:

Automated guided vehicles (AGVs) or automated straddle carriers navigate using GPS, magnetic guidance, optical systems, or combinations thereof. The navigation sensors must provide accurate position information despite electromagnetic interference from the vehicle's own drives and from terminal equipment.

Vehicle-to-infrastructure communication provides traffic management and work assignment. This communication, typically using dedicated radio channels, must be highly reliable because loss of communication could stop operations across the terminal.

Safety systems on automated vehicles include collision avoidance sensors that must detect obstacles reliably. EMC immunity of these safety sensors is critical because interference-induced false negatives could allow collisions.

Vessel Traffic Services

Vessel traffic service (VTS) centers monitor and manage ship movements:

VTS radar systems survey approaches and harbor areas. The radar installations must be sited to provide required coverage while avoiding interference to and from port industrial equipment. Radar performance can be affected by reflections from cranes and other large metallic structures.

VTS communication systems include VHF radio for voice communications with ships. The radio equipment in VTS centers must meet maritime EMC requirements, and antenna siting must consider the port's electromagnetic environment.

AIS (Automatic Identification System) base stations receive ship position reports and transmit shore station information. The AIS receivers must function correctly despite interference from port radio transmitters and industrial equipment.

VTS operator workstations integrate radar, AIS, and communication data. These computer systems should meet appropriate EMC standards and be protected from interference that could affect display reliability.

Port Navigation Aids

Navigation aids guide vessels through port approaches and channels:

LED navigation lights have replaced traditional lights at many ports. The LED driver electronics must not generate interference affecting ship's navigation receivers. Lights with integral AIS transponders require particular attention to EMC to ensure the transponder signals are not corrupted by the lighting electronics.

Radar beacons (racons) respond to ship radar interrogation to identify navigation marks. The racon must receive and respond to radar signals despite any interference from port equipment.

Differential GPS base stations provide correction signals for precise navigation in port areas. The GPS receiver at the base station must be protected from interference to maintain accuracy.

Hydrographic Systems

Ports survey water depths and monitor silting:

Survey vessels use multi-beam echo sounders and other acoustic systems. These systems can be affected by electromagnetic interference coupling into the acoustic transducers or signal processing electronics.

Permanent water level and current monitoring stations may be located near port industrial equipment. The telemetry systems transmitting data from these stations must resist interference from the port environment.

Access Control Systems

Electronic access control manages entry to secure port areas:

Card readers, biometric scanners, and vehicle identification systems at gates must function correctly in the port's electromagnetic environment. Failed authentication due to electromagnetic interference could cause security breaches or operational delays.

Intercom and video systems at access points allow remote verification of credentials. These communication systems must maintain audio and video quality despite interference from nearby equipment.

Barrier systems including gates, rising arm barriers, and bollards use motor drives that can generate interference affecting access control electronics. Proper installation practices help ensure reliable operation.

CCTV and Surveillance

Video surveillance covers port areas for security and operational purposes:

Cameras deployed throughout the terminal operate in varying electromagnetic environments. IP cameras transmit video over network connections that must maintain data integrity despite interference.

Video analytics for automatic intrusion detection and container tracking depend on reliable video capture. Interference-induced video noise could cause false alarms or missed detections.

Long cable runs to remote cameras can pick up electromagnetic interference from crane power cables and other sources. Fiber-optic connections eliminate this susceptibility.

Radiation Detection

Radiation portal monitors (RPMs) screen containers for illicit radioactive materials:

RPMs contain sensitive radiation detectors that measure gamma rays and neutrons. Electromagnetic interference can generate false signals in the detection electronics, potentially causing false alarms that disrupt operations or, worse, desensitizing the system.

Portal monitors are often located at terminal gates where containers pass at low speed. The gate area may have substantial EMI from container handling equipment, OCR lighting, and other systems.

The data communication from RPMs to security centers must be secure and reliable. Any EMC-related communication failures could compromise the security screening process.

Perimeter Security

Intrusion detection systems protect port perimeters:

Fence-mounted sensors using fiber optic, cable, or electronic technologies detect intrusion attempts. The sensors must resist false alarms from electromagnetic sources while remaining sensitive to genuine intrusion attempts.

Ground-based radar and other area surveillance systems may be affected by interference from port equipment. The radar frequency bands used should avoid frequencies heavily used by other port systems.

Integration of multiple sensor types into a coherent security management system requires reliable data communication from sensors throughout the port.

High-Voltage Shore Connection

Large vessels typically connect at 6.6 kV or 11 kV:

The shore-side equipment includes transformers and switchgear that must meet EMC requirements. Frequency conversion may be required for ships designed for 60 Hz operation connecting to 50 Hz port supplies or vice versa. The frequency converters use high-power electronics with associated EMC implications.

The connection cable and plug system must maintain safety and EMC integrity. The cable connection carries not only power but also ground connections that affect the EMC relationship between ship and shore.

During the connection process, transients can occur as the ship's electrical system is transferred from onboard generators to shore power. These transients must not disrupt either shipboard or port systems.

EMC at the Ship-Shore Interface

The shore power connection creates an electromagnetic connection between ship and shore systems:

Ground potential differences between ship and shore can drive common-mode currents through the shore power cable. These currents can cause interference in both shipboard and shore-side equipment and can affect the integrity of sensitive communication and control signals.

The shore power connection should not create ground loops that circumvent the ship's internal grounding system design. Careful attention to the grounding arrangement at the connection point helps maintain EMC integrity.

Power quality on the shore supply affects shipboard equipment. Harmonics, voltage fluctuations, and transients from the port electrical network propagate to the ship through the shore power connection.

Low-Voltage Connections

Smaller vessels may connect at low voltage:

Yacht marinas and small craft harbors provide shore power at 230 V or 120 V depending on region. While power levels are lower than commercial ship connections, EMC principles still apply.

Ground fault protection on marina shore power connections must function correctly to provide safety while not being susceptible to nuisance tripping from electromagnetic interference.

Bulk Handling Systems

Bulk terminals for coal, ore, grain, and other commodities use large conveyor and material handling systems:

Conveyor drives, often using VFDs for speed control, generate electromagnetic interference similar to crane drives. Long conveyor systems with drives distributed along their length create an extended interference source.

Weighing systems measuring cargo throughput use load cells that produce low-level analog signals susceptible to electromagnetic pickup. Proper shielding and signal conditioning help maintain measurement accuracy.

Dust suppression systems in bulk terminals may include electrostatic precipitators or other equipment with high-voltage power supplies that generate electromagnetic fields.

Liquid Cargo Terminals

Oil, chemical, and LNG terminals have specific EMC requirements:

Hazardous area classifications in liquid cargo terminals require attention to EMC as part of overall explosion protection. The principles discussed for offshore platforms apply to shore-side liquid cargo facilities.

Loading arm controls and custody transfer metering must function reliably in the terminal's electromagnetic environment. Flow measurement errors due to EMI could have significant commercial implications.

Fire and gas detection systems protecting liquid cargo areas must be immune to interference that could cause false alarms or missed detections.

Passenger Terminals

Cruise and ferry terminals have different EMC considerations from cargo facilities:

Passenger screening equipment including X-ray scanners and metal detectors must function correctly in the terminal environment. These systems are designed for airport-like conditions and may require additional EMC protection in port environments.

Public address and information display systems must provide clear communication to passengers. Audio interference from terminal electrical systems would degrade the passenger experience.

Baggage handling systems use conveyors and sorting equipment similar to airport installations. Barcode and RFID readers for baggage identification must function reliably.

X-Ray Scanning Systems

Large-scale X-ray systems scan shipping containers and vehicles:

Fixed and mobile container scanners use high-energy X-ray or gamma sources to image container contents. The detection systems are sensitive to electromagnetic interference that could create image artifacts or system malfunctions.

The X-ray generation system typically uses high-voltage power supplies operating at hundreds of kilovolts. These power supplies can generate electromagnetic emissions affecting nearby equipment.

Image processing and analysis systems interpret scan results. Reliable data communication between the scanner and analysis workstations is essential for effective border security.

Non-Intrusive Inspection

Various technologies support cargo inspection without opening containers:

Density and weight measurement systems help identify anomalies suggesting hidden contraband. These systems use sensors that must resist electromagnetic interference.

Heartbeat detectors and CO2 sensors identify human presence in containers. The sensitivity of these detectors makes EMC immunity particularly important.

Shipyard Equipment

Ship repair facilities use various heavy equipment:

Floating and land-based cranes for ship repair have EMC characteristics similar to cargo handling cranes. Welding equipment, both on shore and on vessels under repair, generates significant electromagnetic interference.

Machine shops with numerically controlled equipment require EMC-appropriate installation to maintain precision in the presence of interference from adjacent heavy equipment.

Hot Work Operations

Welding and cutting on vessels creates specific EMC situations:

High-current welding creates substantial electromagnetic fields. Electronic equipment on vessels undergoing welding can be affected and may require protection or removal during hot work.

The welding return current path must be controlled to prevent stray currents that could damage electronic equipment or create interference with ship's systems not involved in the repair work.

Testing and Commissioning

After repair, ship's systems require testing and commissioning:

EMC testing may be required to verify that repairs have not degraded the electromagnetic compatibility of shipboard systems. This is particularly important for vessels that have undergone extensive electrical work.

Radar and communication system testing at the shipyard must not interfere with port operations or other vessels.

Site Surveys

Baseline EMC surveys establish the electromagnetic environment:

Spectrum surveys identify the radio frequencies in use at the port and their signal levels. This information helps plan new radio systems and diagnose interference problems.

Field strength measurements near major EMI sources characterize the interference potential. These measurements help establish exclusion zones and equipment protection requirements.

Surveys should be conducted during typical operational conditions to capture representative interference levels. Crane operations, ship movements, and other activities affect the electromagnetic environment.

Interference Investigation

When interference problems occur, systematic investigation identifies causes:

Time correlation between interference symptoms and equipment operation often identifies the source. Interference that occurs only during crane operations, for example, strongly suggests the crane as the source.

Frequency analysis of interference helps identify specific sources. VFD switching frequencies, harmonic patterns, and other spectral signatures can point to particular equipment.

Field strength measurements with directional antennas can locate interference sources by triangulation or signal strength gradient following.

Compliance Verification

Ports may need to verify EMC compliance for various purposes:

New equipment installation should be verified to meet applicable EMC standards before being placed in service. Post-installation testing confirms that the equipment performs as specified in the actual port environment.

Radio system licensing may require verification that equipment meets regulatory emission limits. Measurement according to appropriate standards documents the compliance status.

Periodic reassessment ensures that the port's electromagnetic environment remains acceptable as equipment is added or modified over time.

Industrial EMC Standards

Much port equipment falls under industrial EMC requirements:

IEC 61000-6-2 specifies immunity requirements for industrial environments, with higher immunity levels than residential or commercial standards. Equipment meeting this standard should withstand typical port interference levels.

IEC 61000-6-4 specifies emission limits for industrial environments. Equipment meeting these limits should not generate unacceptable interference in typical port installations, though the concentration of equipment at ports may require additional attention.

IEC 61800-3 addresses variable speed drives specifically, with emission limits and immunity requirements relevant to the many VFDs used in port equipment.

Maritime EMC Standards

Some port equipment may need to meet maritime standards:

IEC 60945 specifies EMC requirements for maritime navigation and communication equipment. VTS equipment and navigation aids at ports should meet these requirements.

Shore power connection systems may reference IEC/ISO/IEEE 80005 series standards, which include EMC considerations for the ship-shore interface.

Radio Regulations

Port radio systems must comply with national and international radio regulations:

VHF marine radio meets ITU Radio Regulations and national licensing requirements. AIS equipment meets technical standards specified by IMO and IEC.

Private mobile radio systems at ports must comply with national radio licensing requirements and may be subject to type approval or conformity assessment requirements.