1. Introduction
Shotcrete equipment operates under extreme mechanical, hydraulic, and pneumatic stress.
High pumping pressures, abrasive materials, cyclic loading, and chemically aggressive admixtures place continuous strain on every component of the system.
Equipment reliability is therefore not a maintenance issue alone. It is a structural and safety issue.
Failures in shotcrete equipment directly affect lining quality, operator safety, and excavation stability.
For this reason, EFNARC recognises equipment condition and inspection discipline as fundamental to sprayed concrete execution.
2. Equipment reliability as a quality driver
Unstable equipment produces unstable shotcrete.
Mechanical irregularities manifest at the nozzle as:
• Pulsation
• Inconsistent flow
• Irregular accelerator dosing
• Variable compaction
These effects cannot be compensated for by operator skill.
Consistent lining quality therefore begins with mechanically stable equipment.
3. Philosophy of daily inspection
Daily inspection is preventative rather than reactive.
Its purpose is to identify developing faults before failure occurs.
Inspections must be performed at the beginning of every shift and documented.
Operating defective equipment in shotcrete work is unacceptable due to the risks involved.
4. Mixer inspection and function
The mixer ensures uniform distribution of cement, aggregates, fibres, and admixtures.
Key inspection points include:
• Cleanliness of the mixing chamber
• Integrity of mixing blades
• Correct blade spacing
• Condition of drive system
• Presence and function of safety grids
Incorrect mixing leads to fibre balling, segregation, and inconsistent rheology.
The mixer must also rotate in the correct direction. Reverse rotation compromises mix homogeneity.
5. Pump mechanical inspection
The concrete pump is the heart of the system.
Inspection includes:
• Visual inspection for oil leaks
• Integrity of hydraulic hoses
• Condition of cylinders and seals
• Function of changeover system
• Condition of hopper and cleaning doors
Any leakage or abnormal movement indicates developing failure and must be corrected before spraying.
6. Changeover system reliability
In piston pumps, the changeover system controls material direction between cylinders.
Irregular changeover causes:
• Pressure spikes
• Flow interruption
• Nozzle surging
Inspection must confirm smooth, continuous movement without jerking or hesitation.
Abnormal noise or vibration indicates mechanical wear.
7. Lubrication systems
Lubrication reduces wear and prevents seizure of moving components.
Grease points typically include:
• Changeover hinge points
• Swing arms
• Outlet bearings
Lubrication must be performed at the beginning of each shift using the correct grease type.
Under-lubrication accelerates wear. Over-lubrication causes contamination.
8. Hose inspection and integrity
Delivery hoses are subjected to high internal pressure and abrasive flow.
Hoses must be inspected for:
• External damage
• Bulging
• Soft spots
• Worn collars
• Internal contamination
Damaged hoses represent one of the highest safety risks in shotcrete operations.
A hose rupture under pressure can result in severe injury or fatality.
9. Hose length management
Excessive hose length increases pressure loss and pulsation.
Shorter hose sections improve flow stability and simplify cleaning.
Industry practice typically limits hose sections to 10 metres for delivery hoses and shorter sections near the nozzle.
Long hoses significantly increase blockage risk.
10. Clamps and pressure seals
Every hose connection is a potential failure point.
Clamps must be:
• Clean
• Undamaged
• Fully closed
• Secured with safety pins
Pressure seals must be intact and correctly positioned.
Concrete leakage at joints indicates improper sealing and must not be ignored.
11. Reducers and transitions
Reducers must be installed whenever hose diameter differs from pump outlet size.
Incorrect or missing reducers cause concrete build-up and initiate blockages.
Reducer edges must be clean to allow proper clamp engagement.
12. Nozzle assembly inspection
The nozzle assembly is where final mixing occurs.
Inspection includes:
• Injector cleanliness
• Integrity of O-rings
• Function of non-return valves
• Clean air and accelerator ports
Blocked injector holes result in uneven accelerator distribution and inconsistent setting behaviour.
O-ring failure allows internal leakage, reducing effective dosing.
13. Accelerator pump inspection
The accelerator pump must deliver consistent flow.
Inspection includes:
• Hose condition
• Direction of rotation
• Leak-free fittings
• Clean suction line
• Adequate chemical level
Incorrect pump rotation or air ingress results in under-dosing and lining instability.
14. Air system inspection
Compressed air drives projection energy.
Air hoses must be inspected for:
• Damage
• Kinks
• Secure couplings
• Functioning safety devices
Air line failure under pressure presents severe safety hazards.
15. Electrical and control systems
Electrical systems must be intact and protected.
Inspection includes:
• Control panels
• Emergency stops
• Lockout switches
• Cable integrity
Emergency stops must be tested regularly to ensure immediate shutdown capability.
16. Mechanical checks under operation
Mechanical inspection includes running checks.
During operation, inspectors should observe:
• Abnormal vibration
• Irregular sound
• Pressure fluctuations
• Oil temperature behaviour
Any abnormality requires shutdown and investigation.
17. Cleaning and washout discipline
Failure to clean equipment properly is a primary cause of next-shift failures.
Concrete residue hardens rapidly and creates obstructions.
Cleaning must include:
• Hoses
• Hopper
• Pump cylinders
• Accelerator lines
• Nozzle assembly
Incomplete cleaning leads to cumulative deterioration.
18. Documentation and accountability
All inspections must be documented.
Checklists provide traceability and ensure consistency.
Recorded defects must be addressed before operation resumes.
19. Relationship between maintenance and safety
Equipment failure directly threatens operator safety.
High-pressure systems store significant energy.
Strict maintenance discipline is therefore essential for safe operations.
20. Engineering responsibility
Shotcrete equipment must be treated as a precision system.
Neglect, shortcuts, or deferred repairs inevitably lead to failure.
EFNARC emphasises that reliable equipment operation underpins safe and consistent sprayed concrete execution