In the daily operation and maintenance of electro-hydraulic grabs, the electrical and hydraulic systems constitute the core power and control carriers, while simultaneously representing the two subsystems with the highest potential risks. Electrical work involves hazards of electric shock, short circuits, and arc flash burns; hydraulic work encompasses high-pressure fluid injection injuries, burns, fire hazards, and environmental contamination. Consequently, safe operations on these two systems cannot rely on empirical judgment alone. Still, they must be built upon a rigorous, standardized framework encompassing personnel qualification, access, procedural workflows, protective measures, and emergency response protocols. Based on the safety sections of internationally recognized grab manufacturer operating manuals, this article systematically elaborates on the core safety requirements for electrical and hydraulic system operations, providing clear operational guidance for on-site engineering and technical personnel.
Part One: Electrical System Safety Notes
1. Personnel Qualification – Strict Definition of Authorized Operators
In accordance with electro-technical regulations, any work on electric-hydraulic grabs electrical systems – including installation, troubleshooting, repair, and circuit modifications – may only be performed by the following two categories of personnel:
Certified Electricians: Individuals holding statutory electrical operation qualifications, with proficiency in electrical schematics, protection device logic, and fault diagnosis methodologies.
Instructed Persons: Trained individuals who operate exclusively under the guidance and direct supervision of a certified electrician. They are not permitted to work independently, nor to make discretionary judgments or bypass safety procedures.
This requirement establishes "qualification" rather than "experience" as the legal prerequisite for electrical work, aiming to eliminate systemic risks arising from unlicensed operations.
2. Fuse Management – Strict Rating Control and Prohibition of Substitutes
Fuses in the electric-hydraulic grab's electrical system serve the critical function of overcurrent protection. Only original fuses with the specified amperage rating (as listed in the spare parts list) shall be used. The use of copper wire, iron wire, or any other non-standard substitute is strictly prohibited, as such practices will disable the overcurrent protection function, potentially leading to cable overheating and even fire incidents.
3. Fault Response – Immediate Shutdown Upon Power Supply Anomalies
Should any abnormality occur in the electrical power supply – including voltage fluctuations, phase loss, RCD tripping, unexpected power interruption, or persistent arcing – the operator must immediately shut down the electric hydraulic grab and report the issue to the responsible department for investigation. Under no circumstances shall the operator attempt to continue operation or repeatedly restart the equipment, as this may exacerbate equipment damage or cause personal injury.
4. The "Five-Step Safety Procedure" for De-energized Work
When inspection, maintenance, or repair work is to be performed on the electric hydraulic grab or its system components, the following de-energization safety sequence must be executed in order:
Disconnect: Completely isolate the equipment from the main power supply network;
Verify Dead: Use a certified voltage tester to confirm that the disconnected parts are indeed free of voltage;
Ground and Short-circuit: Apply grounding and short-circuit protection against any residual static or induced charges;
Insulate Neighboring Live Parts: Provide insulating shielding for adjacent components that remain energized;
Lock-out/Tag-out: Affix warning tags at the disconnection points to prevent accidental re-energization.
These steps are mandatory, and their sequence must not be altered or omitted.
5. Special Control Measures for Live Work
If operational constraints make it necessary to perform work on live parts, the following additional safety measures shall be strictly enforced:
Attendant Supervisor Requirement: A second person must be present on-site throughout the entire operation, maintaining visual or wireless contact, and capable of immediately actuating the emergency-off switch or disconnecting the master switch in an emergency;
Work Area Securing: Delineate the work zone with red-white safety chains and prominent warning signs to prevent unauthorized personnel from entering;
Insulated Tools Only: All tools used must be certified insulated tools; standard metal tools are not permitted.
6. Regular Inspection and Post-Installation Verification
Electrical equipment shall be subject to periodic routine inspections. Any defects – such as loose connections, damaged cable insulation, terminal oxidation, or broken grounding conductors – must be rectified immediately without deferral to scheduled downtime. Furthermore, upon completion of any electrical installation or repair, the installed protective measures (e.g., earthing resistance values) shall be measured and verified to ensure they remain within the specified limits before the equipment is returned to service.
Part Two: Hydraulic System Safety Notes
1. Personnel Qualification – Specialized Knowledge and Schematic Literacy
Work on the electric hydraulic grab's hydraulic system of the electric hydraulic grabs may be performed only by persons possessing specialized hydraulic knowledge and proven practical experience. Such personnel must demonstrate the following competencies:
Ability to correctly read and fully comprehend the hydraulic diagram;
Clear understanding of the functional interrelationships and interlocking logic of integrated safety systems (e.g., relief valves, check valves, counterbalance valves, pressure switches);
Capability to correctly identify pressure release paths according to the system's construction and functional description.
Personnel lacking the above capabilities are not authorized to perform any hydraulic line disassembly, valve adjustment, or seal replacement work.
2. Mandatory Personal Protective Equipment (PPE)
When performing electric hydraulic grab's hydraulic system work, personnel must wear the following PPE at all times:
| Protection Area | Recommended Equipment |
|---|---|
| Hands | Oil-resistant cut-resistant gloves |
| Body | Protective work clothing |
| Eyes/Face | Safety goggles or full-face visor |
| Head (optional) | Hard hat with visor mount |
High-pressure hydraulic oil jets can penetrate the skin, causing severe injuries (hydraulic injection injuries) that require surgical debridement – a particularly serious industrial trauma. PPE is therefore non-negotiable.
3. The Cardinal Prohibition: No Work on Pressurized Components
The hydraulic system of the electric hydraulic grab operates under high pressure (often several tens of MPa). It is absolutely prohibited to loosen or tighten any screw fittings of hydraulic lines (hydraulic couplings) while the system remains under pressure. Before any line work, the electric hydraulic grab's system pressure must be fully released following the depressurization procedure described in the construction and functional description, using designated manometer connection points. Work may commence only after the pressure gauge confirms zero reading.
4. Oil Leakage Control and Environmental Compliance
Prevention First: Take all practicable measures to avoid oil leakage during operations;
Immediate Containment: Any leaking oil must be collected on-site using appropriate receptacles (not improvised containers);
Regulatory Disposal: Waste oil shall be disposed of strictly in accordance with applicable environmental regulations, through authorized recycling contractors. Disposal by incineration or direct pouring is prohibited.
5. Line Inspection and Zero-Tolerance for Defects
All hydraulic lines, hose assemblies, and connections shall be subject to regular comprehensive inspections, with particular attention to:
External leakage (seepage or dripping);
Hose surface abnormalities – bulges, cuts, abrasion through the outer layer, hardening, or cracking;
Loose fittings or extruded/deformed seals.
Any damage must be repaired immediately upon discovery, without deferral under the pretext of "monitoring for a few more days." Loose screw fittings may be tightened only after the system has been fully depressurized.
6. Hose Selection and Routing Requirements
Hydraulic line routing and installation shall comply with the following specifications:
Correct Routing and Bend Radius: Lines shall be routed clear of moving parts, sharp edges, and heat sources;
No Interchange of Connections: Ports shall not be interchanged, as this will cause erroneous actuator logic;
Component Compatibility: The fitting type, length, pressure rating, and material of all hoses must fully meet the system design requirements. Substitution with "similar length" or "thread-compatible" parts is prohibited.
7. Modification Prohibition and Cleanliness Management
Absolutely No Unauthorized Modifications: Any alteration to the hydraulic system of the electric-hydraulic grab – including pressure settings, line routing, or valve configuration – without prior written approval from the manufacturer constitutes a violation;
Strict Cleanliness Requirements: All hydraulic work must be performed under the highest cleanliness standards. The external surrounding area shall be cleaned before disconnecting any connections. All openings shall be immediately sealed with protective caps after disconnection until reconnection is completed, to prevent ingress of dirt, sand, fibers, or metallic debris.
8. Prevention of Unintended Movements
Before performing any hydraulic maintenance work, mechanical locking or supporting measures shall be applied to ensure that the electric hydraulic grab shells, cylinder piston rods, and associated mechanisms cannot move unexpectedly – whether due to gravity settling, residual pressure release, or accidental control valve actuation – thereby avoiding crushing or shearing injuries.
