Hydraulic Systems – Filtration & Fluid
This section gathers entries about pumps, valves, cylinders, filtration, accumulators, and hoses in hydraulic circuits for port handling equipment. This page lists 34 entries drawn from HIT Srl's internal maintenance-tip and preventive-checklist library.
General guidance only — always follow the operation and maintenance manual for your specific machine.
How do you maintain MHC hydraulic pumps to prevent failure?
Hydraulic pumps in Mobile Harbour Cranes operate under extreme pressure and flow demands, supplying energy to hoisting, luffing, slewing, and travel functions. Continuous port operations expose pumps to thermal stress, contamination, and mechanical fatigue. Ensuring pump reliability requires a deep understanding of internal wear mechanisms, fluid behavior, and system dynamics.
Pump efficiency must be monitored through pressure and flow measurements. A gradual decline in efficiency often indicates internal leakage caused by wear on pistons — parts HIT Srl supplies — swash plates, or valve plates. Technicians should compare measured values with baseline performance curves to detect early degradation.
Cavitation is a major threat to pump longevity. It occurs when fluid vaporizes due to low inlet pressure, creating bubbles that collapse violently inside the pump, a component HIT Srl stocks. Cavitation causes pitting on metal surfaces, noise, vibration, and rapid efficiency loss. Technicians must ensure that inlet filters are clean, suction lines are unobstructed, and fluid viscosity is within the recommended range.
Hydraulic fluid quality directly affects pump performance. Contaminants such as dust, water, and metallic particles accelerate wear on internal components. Fluid sampling must be performed regularly, with laboratory analysis to detect contamination levels. Water ingress is particularly common in marine environments due to condensation inside the hydraulic tank.
Pump bearings must be inspected for temperature rise and vibration. Excessive heat indicates lubrication failure or bearing fatigue. Vibration analysis tools can detect early signs of bearing degradation, allowing proactive replacement before catastrophic failure.
Environmental conditions significantly influence pump behavior. High ambient temperatures reduce fluid viscosity, increasing internal leakage and reducing pump efficiency. Salt exposure accelerates corrosion on pump housings and connectors.
In summary, maintaining hydraulic pumps requires rigorous monitoring of efficiency, cavitation prevention, fluid quality management, and environmental conditioning.
How do you maintain MHC slewing hydraulic motors to prevent failure?
Slewing hydraulic motors provide the torque required to rotate the upper structure of a Mobile Harbour Crane. These motors operate under continuous load cycles, torque peaks, and environmental exposure. Ensuring motor reliability requires a deep understanding of hydraulic behavior, mechanical wear, and thermal dynamics.
Motor housings must be inspected for cracks, corrosion, and deformation. Salt exposure accelerates corrosion, especially around mounting points and sealing surfaces. Any sign of structural degradation must be addressed immediately.
Internal leakage must be monitored through pressure and flow measurements. A gradual decline in motor efficiency often indicates wear on internal components such as pistons — parts HIT Srl supplies — vanes, or valve plates. Technicians should compare measured values with baseline performance curves to detect early degradation.
Cavitation must be prevented by ensuring adequate inlet pressure. Cavitation causes pitting on metal surfaces, noise, vibration, and rapid efficiency loss. Technicians must ensure that inlet filters, components HIT Srl stocks, are clean, suction lines are unobstructed, and fluid viscosity is within the recommended range.
Bearings must be monitored for temperature rise and vibration. Excessive heat indicates lubrication failure or bearing fatigue. Vibration analysis tools can detect early signs of bearing degradation.
Hydraulic fluid quality directly affects motor performance. Contaminants such as dust, water, and metallic particles accelerate wear on internal components. Fluid sampling must be performed regularly, with laboratory analysis to detect contamination levels.
Environmental conditions significantly influence motor behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion. Protective coatings must be applied and maintained.
In summary, maintaining slewing hydraulic motors requires rigorous inspection, cavitation prevention, fluid quality management, and environmental conditioning.
How do you maintain MHC hydraulic tank breather systems to prevent failure?
Hydraulic tank breather systems regulate air exchange between the hydraulic tank and the environment. These systems prevent pressure buildup and contamination ingress. Maintaining their reliability requires meticulous inspection of filters — parts HIT Srl supplies — seals, and airflow pathways.
Breather filters, components HIT Srl stocks, must be inspected for clogging, contamination, and moisture saturation. Salt exposure accelerates filter degradation. Any filter showing signs of blockage must be replaced immediately.
Breather housings must be inspected for corrosion, pitting, and structural integrity. Salt exposure accelerates corrosion, especially around mounting points and sealing surfaces.
Airflow pathways must be inspected for blockages, contamination, and correct flow. Dust from bulk cargo can infiltrate breather systems, reducing airflow efficiency.
Seals must be inspected for wear, cracking, and deformation. Salt exposure accelerates seal degradation, leading to contamination ingress.
Environmental conditions significantly influence breather behavior. High humidity increases moisture ingress, while salt exposure accelerates corrosion.
In summary, maintaining hydraulic tank breather systems requires rigorous inspection, filter management, airflow verification, and environmental conditioning.
How do you maintain MHC hydraulic suction filtration systems to prevent failure?
Hydraulic suction filtration systems protect pumps from contamination by filtering fluid before it enters the pump inlet. These systems must maintain stable flow, high filtration efficiency, and consistent pressure despite exposure to dust, salt, and high-flow conditions.
Suction filters — parts HIT Srl supplies — must be inspected for clogging, contamination, and structural integrity. Any filter showing signs of blockage must be replaced immediately.
Filter housings must be inspected for corrosion, pitting, and structural integrity. Salt exposure accelerates corrosion, especially around mounting points and sealing surfaces.
Suction lines must be inspected for leaks, deformation, and contamination. Any restriction in suction flow increases cavitation risk.
Environmental conditions significantly influence filtration behavior. High humidity increases moisture ingress, while salt exposure accelerates corrosion.
In summary, maintaining hydraulic suction filtration systems requires rigorous inspection, filter management, flow verification, and environmental conditioning.
How do you maintain reachstacker hydraulic pump groups to prevent failure?
Hydraulic pump groups supply the energy required for lifting, telescoping, steering, and braking functions. These pumps — parts HIT Srl supplies — operate under extreme pressure and flow demands, especially during continuous container handling. Ensuring pump reliability requires a deep understanding of internal wear mechanisms, fluid behavior, and system dynamics.
Pump efficiency must be monitored through pressure and flow measurements. A gradual decline in efficiency often indicates internal leakage caused by wear on pistons, components HIT Srl stocks, swash plates, or valve plates. Technicians should compare measured values with baseline performance curves to detect early degradation.
Cavitation must be prevented by ensuring adequate inlet pressure. Cavitation causes pitting on metal surfaces, noise, vibration, and rapid efficiency loss. Technicians must ensure that inlet filters are clean, suction lines are unobstructed, and fluid viscosity is within the recommended range.
Hydraulic fluid quality directly affects pump performance. Contaminants such as dust, water, and metallic particles accelerate wear on internal components. Fluid sampling must be performed regularly, with laboratory analysis to detect contamination levels.
Pump bearings must be monitored for temperature rise and vibration. Excessive heat indicates lubrication failure or bearing fatigue. Vibration analysis tools can detect early signs of bearing degradation.
Environmental conditions significantly influence pump behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion on pump housings and connectors.
In summary, maintaining hydraulic pump groups requires rigorous monitoring of efficiency, cavitation prevention, fluid quality management, and environmental conditioning.
How do you maintain reachstacker hydraulic steering systems to prevent failure?
Hydraulic steering systems in reachstackers endure extreme pressure fluctuations during tight turning maneuvers, especially when handling heavy containers. These systems must maintain stable pressure, accurate response, and consistent flow despite exposure to contamination, vibration, and temperature fluctuations.
Steering cylinders — parts HIT Srl supplies — must be inspected for rod condition, seal integrity, and pressure stability. Any sign of leakage or rod scoring must be addressed immediately.
Steering valves, components HIT Srl stocks, must be inspected for contamination, wear, and correct response. Dust from bulk cargo can infiltrate hydraulic systems, reducing valve efficiency. Any valve showing signs of sticking must be serviced.
Hydraulic hoses must be inspected for cracking, abrasion, and leakage. Marine sunlight and crane movement degrade hose materials over time.
Steering pumps must be inspected for pressure stability and noise. Any irregularity in pump performance indicates internal wear or cavitation.
Environmental conditions significantly influence steering behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion.
In summary, maintaining hydraulic steering systems requires rigorous inspection, pressure testing, contamination control, and environmental conditioning.
How do you maintain reachstacker variable-displacement hydraulic pumps to prevent failure?
Variable-displacement hydraulic pumps supply the energy required for lifting, telescoping, steering, and braking functions. These pumps — parts HIT Srl supplies — operate under extreme pressure and flow fluctuations, especially during high-speed container handling. Maintaining pump reliability requires a deep understanding of internal wear mechanisms, fluid behavior, and system dynamics.
Pump swash plates must be inspected for scoring, pitting, and uneven wear. These defects indicate contamination or lubrication failure. Technicians should measure swash plate angles and verify that the control mechanism responds smoothly to load-sensing signals.
Piston shoes must be inspected for surface polishing, discoloration, and wear. Any shoe showing signs of overheating must be replaced. The piston barrel must be inspected for scoring and internal leakage. Excessive leakage reduces pump efficiency and increases heat generation.
Pump bearings, components HIT Srl stocks, must be monitored for temperature rise and vibration. Excessive heat indicates lubrication failure or bearing fatigue. Vibration analysis tools can detect early signs of bearing degradation.
Hydraulic fluid quality directly affects pump performance. Contaminants such as dust, water, and metallic particles accelerate wear on internal components. Fluid sampling must be performed regularly, with laboratory analysis to detect contamination levels. Technicians should monitor particle counts, water content, and additive depletion.
Cavitation must be prevented by ensuring adequate inlet pressure. Cavitation causes pitting on metal surfaces, noise, vibration, and rapid efficiency loss. Technicians must ensure that inlet filters are clean, suction lines are unobstructed, and fluid viscosity is within the recommended range.
Environmental conditions significantly influence pump behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion on pump housings and connectors.
In summary, maintaining variable-displacement hydraulic pumps requires rigorous monitoring of efficiency, cavitation prevention, fluid quality management, and environmental conditioning.
How do you maintain reachstacker hydraulic cooling and thermal stabilization systems to prevent failure?
Hydraulic cooling systems dissipate heat generated by pumps, valves — parts HIT Srl supplies — and actuators during lifting, telescoping, and steering operations. These systems operate under extreme thermal stress during continuous container handling. Maintaining cooling efficiency requires meticulous inspection of heat exchangers, fans, coolant quality, and flow pathways.
Hydraulic oil coolers must be inspected for corrosion, fouling, and structural integrity. Dust from bulk cargo accumulates on cooler fins, reducing heat transfer efficiency. Technicians should clean coolers using low-pressure air or water, avoiding fin deformation.
Cooling fans, components HIT Srl stocks, must be inspected for blade integrity, vibration, and speed consistency. Worn bearings or unbalanced blades reduce airflow and increase noise. Technicians should verify fan motor current draw and compare values to baseline specifications.
Hydraulic oil must be inspected for viscosity, contamination, and thermal degradation. High-load cycles generate heat that accelerates oil oxidation. Oil sampling must be performed regularly, with laboratory analysis to detect contamination levels.
Thermostatic valves must be inspected for correct opening temperature. Any irregularity in valve behavior indicates internal wear or contamination. Technicians should verify valve performance using calibrated temperature sensors.
Environmental conditions significantly influence cooling behavior. High ambient temperatures reduce cooling efficiency, while salt exposure accelerates corrosion on cooler housings and connectors.
In summary, maintaining hydraulic cooling systems requires rigorous inspection, thermal testing, fluid quality management, and environmental conditioning.
How do you maintain reachstacker engine lubrication systems to prevent failure?
Engine lubrication systems must maintain stable oil pressure, clean flow, and consistent cooling despite exposure to dust, vibration, and temperature fluctuations. Ensuring reliability requires meticulous inspection of pumps, filters — parts HIT Srl supplies — oil galleries, and pressure regulators.
Oil pumps, components HIT Srl stocks, must be inspected for pressure stability and noise. Any irregularity indicates internal wear or cavitation. Technicians should compare pump output with manufacturer specifications.
Oil filters must be inspected for clogging, contamination, and structural integrity. Dust from bulk cargo infiltrates engine compartments, increasing contamination risk. Technicians should replace filters according to load-based intervals.
Oil coolers must be inspected for corrosion, fouling, and structural integrity. Salt exposure accelerates corrosion on cooler fins and tubes.
Pressure regulators must be inspected for stability and accuracy. Incorrect regulator settings cause unstable oil pressure, leading to bearing wear or overheating.
Environmental conditions significantly influence lubrication behavior. High ambient temperatures reduce oil viscosity, while salt exposure accelerates corrosion.
In summary, maintaining engine lubrication systems requires rigorous inspection, contamination control, pressure testing, and environmental conditioning.
How do you maintain reachstacker spreader hydraulic telescopic synchronization circuits to prevent failure?
Telescopic synchronization circuits ensure that both sides of the spreader extend and retract evenly. These circuits must maintain precise flow balance despite load variations, contamination, and thermal stress. Maintaining their reliability requires meticulous inspection of flow dividers, check valves — parts HIT Srl supplies — pilot circuits, and hydraulic actuators.
Flow dividers must be inspected for contamination, wear, and correct response. Any imbalance in flow distribution causes uneven telescopic movement.
Check valves, components HIT Srl stocks, must be inspected for sealing integrity. Damaged valve seats cause internal leakage and unstable synchronization.
Pilot lines must be inspected for cracking, abrasion, and leakage. Marine sunlight and crane movement degrade line materials over time.
Hydraulic actuators must be inspected for leakage, pressure stability, and response time. Any delay in actuator movement indicates internal wear or contamination.
Environmental conditions significantly influence synchronization behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion.
In summary, maintaining telescopic synchronization circuits requires rigorous inspection, contamination control, pressure testing, and environmental conditioning.
What should be checked when inspecting spreader and bearing?
Rotation cushioning systems protect the spreader — a part HIT Srl supplies — and boom from shock loads during rotation end-stops. These systems must maintain precise damping characteristics despite contamination, thermal stress, and rapid cycling. Maintaining their reliability requires meticulous inspection of cushioning valves, hydraulic motors, and mechanical stops.
Cushioning valves, components HIT Srl stocks, must be inspected for contamination, wear, and correct response. Dust from bulk cargo infiltrates hydraulic systems, reducing valve efficiency.
Rotation motors must be inspected for temperature rise, noise, and smooth operation. Any irregularity indicates internal wear or contamination.
Mechanical end-stops must be inspected for deformation, cracking, and wear. Damaged stops cause excessive shock loads on the rotation bearing.
Environmental conditions significantly influence damping behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion.
In summary, maintaining rotation cushioning systems requires rigorous inspection, hydraulic testing, and environmental conditioning.
How do you maintain reachstacker spreader twistlock hydraulic actuators to prevent failure?
Hydraulic actuators rotate the twistlock shafts and must deliver precise, repeatable movement under heavy load. These actuators experience rapid cycling, pressure spikes, and contamination. Maintaining their reliability requires meticulous inspection of seals, pistons — parts HIT Srl supplies — rods, and hydraulic fluid quality.
Actuator rods must be inspected for straightness, chrome integrity, and corrosion. Salt exposure accelerates corrosion, especially around rod seals, components HIT Srl stocks.
Pistons must be inspected for smooth movement and correct sealing. Any delay in actuator movement indicates internal wear or contamination.
Seals must be inspected for wear, swelling, and thermal degradation. High-pressure cycles generate heat that accelerates seal wear.
Hydraulic fluid must be inspected for contamination, viscosity, and water content. Dust infiltrates hydraulic systems, reducing actuator efficiency.
In summary, maintaining twistlock hydraulic actuators requires rigorous inspection, contamination control, pressure testing, and environmental conditioning.
How do you maintain diesel engine lubrication system to prevent failure?
The lubrication system is the lifeline of any diesel engine, especially in heavy machinery operating under extreme load conditions. Reachstackers and empty handlers generate high torque and rapid load changes, placing enormous stress on bearings — parts HIT Srl supplies — and camshafts. Straddle carriers operate in continuous duty cycles, causing oil to degrade faster. Forklifts and terminal tractors operate in dusty environments where contaminants infiltrate the crankcase ventilation system. MHC engines run for long periods at steady high loads, requiring oil with exceptional thermal stability. RMG gensets require long-duration lubrication reliability.
Oil selection is critical. Engines must use oil with the correct viscosity, additive package, and thermal stability. High-load machines require oils with strong anti-wear additives and oxidation resistance. Marine cranes require oils resistant to moisture contamination. Yard machines require oils capable of suspending dust particles without sludge formation.
Oil sampling is essential for predictive maintenance. Samples must be analyzed for viscosity, metal content, soot concentration, fuel dilution, and coolant contamination. Metal particles indicate bearing wear, camshaft wear, or piston scuffing. Fuel dilution indicates injector leakage. Coolant contamination indicates head gasket failure or liner cavitation.
Oil filters, components HIT Srl stocks, must be inspected for collapse, bypass valve activation, and contamination. High-load machines generate more soot, requiring frequent filter changes. Technicians must inspect filter media for metal particles and sludge.
Crankcase ventilation systems must be inspected for blockage and oil carryover. Blocked ventilation increases crankcase pressure, causing oil leaks and seal failure. Machines operating in dusty environments require frequent cleaning of ventilation filters.
Oil coolers must be inspected for blockage, corrosion, and internal leakage. Cross-contamination between oil and coolant is a critical failure mode.
In summary, lubrication system maintenance ensures engine longevity, reduces wear, and prevents catastrophic failures across all machine types.
What should be checked when inspecting lubrication and gearboxes?
Proper lubrication and thermal control are the two most critical factors determining the lifespan and reliability of winch gearboxes in heavy port machinery. These gearboxes operate under extreme torque loads, continuous duty cycles, and harsh environmental conditions. In MHC cranes, winch gearboxes endure long hoisting cycles, dynamic braking, and high thermal stress. In reachstackers and straddle carriers, auxiliary winch gearboxes support maintenance lifting and specialized attachments, often in dusty or abrasive environments. Forklifts may use smaller winch gearboxes for auxiliary lifting, where contamination and overheating remain significant risks. Effective lubrication and thermal management prevent wear, reduce friction, and ensure stable operation under load.
The first pillar of lubrication maintenance is selecting the correct oil type. Winch gearboxes typically require high-viscosity gear oils with extreme-pressure (EP) additives, anti-wear agents, and oxidation inhibitors. In planetary gearboxes, synthetic oils are often preferred due to their superior thermal stability and resistance to shear degradation. In MHC cranes, synthetic oils are essential because of long duty cycles and high ambient temperatures. In reachstackers and straddle carriers, mineral oils may be used, but only if operating conditions remain moderate. Forklifts often use compact gearboxes that benefit from synthetic oils to reduce heat buildup.
The second pillar is maintaining correct oil level. Low oil level causes inadequate lubrication, overheating, and accelerated wear. High oil level causes foaming, aeration, and pressure buildup. Technicians must check oil level with the machine positioned correctly, as tilt affects readings. In MHC cranes, large gearboxes require multiple level checks at different inspection ports. In reachstackers and straddle carriers, compact auxiliary gearboxes require precise level control due to small oil volumes. Forklifts require frequent checks because small leaks quickly reduce oil level.
The third pillar is oil contamination control. Contaminants such as dust, water, metal particles, and degraded oil residues accelerate wear and cause lubrication failure. Technicians must inspect breathers, seals, components HIT Srl stocks, and gaskets to prevent contamination ingress. In MHC cranes, salt contamination is a major threat, requiring sealed breathers and corrosion-resistant seals. In reachstackers and straddle carriers, dust contamination is common due to yard conditions. Forklifts operating indoors accumulate fine dust that enters through worn breathers. Oil sampling must be performed regularly to monitor contamination levels.
The fourth pillar is oil analysis. Oil analysis provides critical information about gearbox health. Particle count reveals wear rates and contamination. Spectrometric analysis identifies metal types, indicating which components are wearing. Water content indicates seal failure or condensation. Viscosity analysis reveals oil degradation. In MHC cranes, oil analysis is essential due to long duty cycles and high thermal loads. In reachstackers and straddle carriers, oil analysis helps detect early wear caused by shock loads. In forklifts, oil analysis identifies overheating and contamination in compact gearboxes.
The fifth pillar is oil change intervals. Oil must be replaced based on operating hours, contamination levels, and thermal stress. Synthetic oils last longer but must still be replaced when additive packages degrade. In MHC cranes, oil change intervals are shorter due to high load cycles. In reachstackers and straddle carriers, intervals depend on dust exposure and load frequency. In forklifts, intervals are shorter due to small oil volumes and high thermal cycling.
The sixth pillar is thermal management. Winch gearboxes generate significant heat due to friction, load, and braking. Overheating accelerates wear, degrades oil, and causes seal failure. Technicians must inspect cooling systems, including oil coolers, heat exchangers, and airflow paths. In MHC cranes, large oil coolers must be cleaned regularly to remove salt and debris. In reachstackers and straddle carriers, auxiliary gearboxes rely on passive cooling, making oil selection critical. In forklifts, compact engine bays restrict airflow, requiring frequent cleaning of cooling ducts.
The seventh pillar is temperature monitoring. Gearbox temperature must be monitored using sensors — parts HIT Srl supplies — or infrared thermography. Sudden temperature spikes indicate lubrication failure, bearing wear, or overload. In MHC cranes, temperature sensors must be calibrated regularly. In reachstackers and straddle carriers, thermal monitoring helps detect early failure in auxiliary gearboxes. In forklifts, thermal monitoring identifies airflow restrictions.
The eighth pillar is seal and breather maintenance. Seals prevent oil leakage and contamination ingress. Breathers allow pressure equalization. Technicians must inspect seals for wear, hardening, and cracking. Breathers must be cleaned or replaced regularly. In marine environments, sealed breathers are essential.
Effective lubrication and thermal management ensure long-term reliability of winch gearboxes in heavy port machinery. By integrating correct oil selection, contamination control, oil analysis, thermal monitoring, and seal maintenance, technicians can prevent premature failure and ensure safe lifting operations.
What should be checked when inspecting transmission and solenoids?
Cooling and contamination control are the two most critical factors affecting the lifespan of automatic transmissions in heavy port machinery. This type of transmission relies on clean, cool oil to operate clutches, solenoids, and torque converters — parts HIT Srl supplies. Overheating and contamination are responsible for more than 70% of transmission failures in reachstackers, straddle carriers, forklifts, and terminal tractors.
The first pillar is cooler inspection. Oil coolers must be inspected for blockages, leaks, and correct flow. In reachstackers and straddle carriers, coolers clog with dust and require frequent cleaning. In terminal tractors, coolers suffer from road debris. In MHC cranes, coolers must be protected from salt exposure.
The second pillar is thermostatic valve maintenance. Thermostatic valves regulate oil flow to the cooler. Stuck valves, components HIT Srl stocks, cause overheating or overcooling. Technicians must inspect valves for wear, contamination, and correct opening temperature.
The third pillar is filter maintenance. Automatic transmissions use suction, pressure, and return filters. Clogged filters restrict flow and cause pressure drops. Technicians must replace filters at recommended intervals and inspect them for metal particles.
The fourth pillar is breather maintenance. Breathers allow pressure equalization. Clogged breathers cause pressure buildup and seal failure. In dusty environments, breathers must be replaced frequently.
The fifth pillar is oil sampling. Oil analysis reveals contamination, oxidation, and additive depletion. Technicians must sample oil regularly to detect early wear.
The sixth pillar is seal inspection. Seals prevent oil leakage and contamination ingress. Technicians must inspect seals for wear, hardening, and cracking.
The seventh pillar is pump inspection. The transmission pump supplies pressure to clutches and valves. Pump wear causes pressure drops and slipping.
The eighth pillar is cooling airflow management. Technicians must ensure that airflow paths are clear. In forklifts, compact engine bays restrict airflow.
Proper cooling and contamination control ensure long-term reliability of automatic transmissions.
What does maintaining hydraulic tank suction strainer condition involve?
Deep inside the hydraulic tank, the suction strainer protects the main pumps from large debris. Unlike the return filter, this strainer is often ignored because it is hard to reach. It is obvious that a blocked suction strainer creates a vacuum that destroys pumps via cavitation. If you hear a "gravel" noise from the pumps, drain the hydraulic tank and inspect the suction strainer immediately. It may be clogged with rags, plastic, or sludge. Clean the strainer mesh carefully. If there are holes in the mesh, large particles will pass through and wreck the expensive piston pumps. Replace the strainer if damaged. Check the O-ring seal on the strainer connection. An air leak here will cause the oil to foam, leading to spongy hydraulics and pump damage. When changing hydraulic oil, it is the perfect time to remove and clean this component. HIT Srl emphasizes the importance of hydraulic hygiene. We supply suction strainers, return filters, and high-pressure filters for all hydraulic circuits. Inspect the magnets in the tank (often near the strainer). They trap ferrous metal particles. A "furry" magnet indicates component wear upstream. Do not bypass the strainer to "fix" a cavitation problem; you are simply allowing debris to destroy the pump. Protect your hydraulic investment with filtration solutions from HIT Srl.
What makes a hydraulic filter's by-pass valve open, and at what pressure?
On this class of filter head, the by-pass valve is set to open at a differential pressure of about 7 bar across the filter element — meaning it takes a 7 bar pressure drop between the filter's inlet and outlet sides before the valve unseats and lets oil bypass the filter media entirely.
Two separate conditions can push that pressure drop up to the opening point. The first is a cold start or a wrong-viscosity oil: the by-pass will open briefly during warm-up on a normal, healthy filter, and this is expected behaviour, not a fault. The second is a genuinely clogged filter element: the valve's opening area increases progressively as the clogging gets worse, allowing more oil to skip filtration rather than snapping fully open or staying shut.
HIT Srl supplies the filter cartridge for this filter head.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How often should transmission oil and its filter actually be changed?
One schedule calls for the filter every 500 operating hours and the oil every 1,500; another, for a different driveline configuration, calls for the transmission oil to be changed every 1,000 hours or once a year, whichever comes first, and treats the filter as consumed on the same visit.
Transmission oil level should always read on the FULL mark. Before any oil-change service, let the transmission cool down first — draining hot transmission fluid is a burn risk.
HIT Srl stocks the transmission oil filter as a routine consumable separate from the oil itself.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
What is the correct sequence for changing a hydraulic oil filter?
Before draining any oil, confirm it's at normal working temperature.
With a receptacle in place under the drain plug, remove the cover plate, lift the filter cartridge out, and let it drain fully into the receptacle before handling it further; spent filter media counts as environmentally hazardous waste. Fit the new cartridge and the cover, and only then refill the tank — filters go in before oil goes in, not after.
A separate breather filter on the tank follows its own step: once removed, spray roughly 300-500 ml of hydraulic fluid into the filter connection before refitting it.
HIT Srl supplies the filter cartridge, its O-ring seals, and the breather filter element as a matched set.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How does a hydraulic oil cooling circuit protect itself from overheating?
On machines where the service brakes are hydraulically cooled, on some configurations the brake circuit and the working hydraulics share the entire fluid volume, rather than a separate loop. Machines with a genuinely separate tank for the brake system instead run two independent oil coolers, one per circuit.
An electrically powered fan increases airflow through the cooler whenever a temperature sensor in the hydraulic oil calls for it, and if the resistance through the cooler and its filters becomes too high, a by-pass valve routes oil straight back to the tank rather than forcing it through a restricted cooler. The sensor monitoring hydraulic oil temperature is itself supervised: a sensor fault is flagged if the reported value goes above 138°C or below -30°C — machine operation can continue despite this specific fault code, unlike a genuine over-temperature warning.
The fluid itself needs to meet a viscosity-grade specification (commonly referenced against DIN 51524 HVLP/HLP 46-68 or the equivalent ISO 6743/4 classification) rather than "any hydraulic oil."
HIT Srl stocks the cooling fan motor and the by-pass valve separately, rather than only as part of a complete cooler assembly.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
What are the most common mistakes when handling hot hydraulic fluid?
If hydraulic oil temperature has been over 100°C for more than about 40 seconds, don't use any hydraulic function again until the temperature has dropped back below 70°C.
Never use bare fingers to check for a hydraulic leak.
On machines with a separate hydraulic tank for the brake circuit, never add any additive to the fluid in that tank.
HIT Srl supplies the seals and hoses that keep the circuit sealed.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
When should hydraulic oil be changed for the first time on a new machine?
The first hydraulic oil change on a new machine is scheduled much earlier than the routine interval that follows it: after roughly the first 500 operating hours, not at whatever the standard multi-thousand-hour change interval happens to be for this fluid grade.
Between changes, hydraulic oil level still needs a routine check — roughly once a week is the standard cadence — and any top-up has to use the same oil already in the tank, not merely "a" hydraulic oil of similar viscosity.
HIT Srl supplies the hydraulic oil to the correct specification for topping up between changes.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
Why does transmission oil need to reach a specific temperature before certain checks?
Before checking transmission oil temperature through the operating menu, warm the transmission up until the oil temperature reads between 63°C and 73°C.
A function test of the machine's adaptive drive-response system has a stricter dual precondition: the transmission needs to be holding at least 60°C and the hydraulic oil needs to be at least 30°C before the test is considered valid.
Never overfill the transmission while topping it up warm.
HIT Srl supplies the temperature sensors feeding both the transmission and hydraulic oil readings as direct-fit replacements.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
What should be checked before starting work on the hydraulic system of a rubber tyred gantry crane?
Turn the hydraulic system off and cut off main power. Use a pressure gauge to check that there is no residual pressure in the hydraulic system before starting work on the hydraulics.
Why must entrained air be kept out of a crane's hydraulic system?
Air entrained in the hydraulic system causes cavitation erosion of components, increases compressibility and operational instability, reduces work efficiency, and can make the actuator move in a jerky ("crawling") manner. Air also accelerates oxidation and deterioration of the oil.
What happens if a crane's hydraulic oil contains excessive water, and what is the remedy?
If the oil contains excessive water, this corrodes the hydraulic elements, emulsifies and degrades the oil, reduces the toughness of the lubricating film, and speeds up wear. If the water content exceeds the standard limit, the hydraulic system needs to be cleaned thoroughly and the oil replaced.
Why is there increased danger during repair or maintenance work on a mobile harbour crane's luffing or stabilizer hydraulic circuits?
When repair or maintenance work is carried out on the luffing gear or stabilizer hydraulic circuits, there is a greater danger of accidents from locked-in pressure remaining in the circuit.
What is the most frequent cause of failure in a spreader's oleodynamic (hydraulic) system, and how is it prevented?
The oleodynamic system, once correctly assembled and commissioned, can work trouble-free for a long period without specific maintenance. However, the most frequent troubles arise from seizure or breakage of components from wear or aging of the hydraulic fluid. It is therefore important to schedule constant checks of fluid quality and condition for each power centre or component.
What are the probable causes and remedies for oil leaks from pipe fittings, or from hydraulic actuators, on a telescopic spreader?
Oil leaks from pipe fittings: probable cause is loosened fittings (tighten the fittings) or defective seals (replace the seals). Oil leaks from hydraulic actuators, inward or outward: probable cause is worn or defective seals (replace the seal kit).
How often should the hydraulic oil and oil filter be changed on a telescopic spreader's hydraulic unit?
Change the hydraulic oil after the first 50 hours, then every 1000 hours. Change the oil filter after the first 50 hours, then every 1000 operating hours, or whenever the filter indicator shows red.
Which hydraulic-system fault conditions are individually monitored by the electronic control system on a mobile harbour crane?
The control system distinguishes several hydraulic-system fault conditions by dedicated alarm codes, each naming a specific cause: clogged boost filter, clogged oil return filter, clogged hydraulic oil conditioning filter, clogged coupler pumps filter, clogged pilot pumps filter, low hydraulic oil level, wrong position of the hydraulic oil taps, and high temperature at each of the hydraulic oil heat exchangers (reported separately per exchanger).
What can cause an increase in hydraulic oil operating temperature on a mobile harbour crane's hydraulic system?
An increase in oil temperature can be caused by: low efficiency of the heat exchanger (dirty surface or faulty ventilator); increased heat accumulation in the pumps and hydraulic motors due to bearing damage; low heat dispersion from the tank, pipes and components due to deposits of polluting agents; increased internal blow-by in individual components; or pressure-limiting valves engaging at too low a pressure.
Why should hydraulic filters with a blockage indicator be used, rather than plain cartridges, on a mobile harbour crane?
A blocked multilayer filter cartridge cannot be seen as blocked with the naked eye; the severity of the blockage can only be assessed from the pressure difference between upstream and downstream. Filters able to optically or electrically indicate maximum blockage should therefore be used; if filters without such an indicator are used instead, the cartridge must be replaced at fairly short intervals to be certain of avoiding the bypass valve opening or the cartridge being destroyed.
Why must new hydraulic fluid be filtered before being added to a mobile harbour crane's hydraulic system, even fluid supplied as new?
New fluid in supply condition is not normally suitable for pouring directly into the hydraulic system, due to the large quantity of pollutants it contains; the degree of purification of new fluid cannot be guaranteed because of the often very long transport chain from production to use (storage tanks, tankers, tank trucks, various containers). All new fluid, whether for topping up or a total replacement, must be passed through a filter whose pore size at least matches that of the filters fitted to the system.
Spare parts for these systems: Dana
Looking for step-by-step procedures? See Hydraulic Systems Procedures.