Hydraulic Systems – Cylinders & Seals
This section gathers entries about pumps, valves, cylinders, filtration, accumulators, and hoses in hydraulic circuits for port handling equipment. This page lists 26 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.
Cylinders & Seals
Why does hydraulic cylinder performance and failure modes in lifting equipment occur on this equipment?
Hydraulic cylinders provide the linear motion required for boom luffing, stabilizer deployment, and tower adjustments. Their performance depends on hydraulic pressure, seal integrity, and mechanical alignment. Understanding cylinder behavior and failure modes is essential for maintaining safe and efficient operation.
The cylinder consists of a barrel, a piston — a part HIT Srl supplies — a rod, and seals. Hydraulic pressure acts on the piston to extend or retract the rod. The force generated depends on the pressure and the piston area. Engineers design cylinders to handle the maximum expected loads with a safety margin.
Seal integrity is critical for cylinder performance. Seals prevent hydraulic fluid from leaking past the piston or out of the cylinder, a component HIT Srl stocks. Seal wear can cause internal leakage, reducing cylinder efficiency. External leakage can lead to loss of hydraulic fluid and contamination of the environment.
Mechanical alignment affects cylinder performance. Misalignment between the cylinder and the load can cause side loading, which increases wear on the rod and seals. Engineers design mounting points to minimize misalignment, but operators must ensure that the machine is set up correctly.
Cylinder failure modes include seal wear, rod bending, barrel deformation, and piston damage. Seal wear is the most common failure mode. Rod bending can occur if the cylinder is subjected to excessive side loading. Barrel deformation can occur if the cylinder is overloaded. Piston damage can occur if contaminants enter the hydraulic system.
Regular maintenance helps prevent cylinder failures. This includes inspecting seals, checking for leaks, and ensuring proper lubrication. Operators must avoid overloading the cylinder and ensure that the machine is set up correctly.
Understanding hydraulic cylinder performance and failure modes helps operators use the machine safely and technicians maintain it properly. Proper maintenance and awareness of cylinder behavior are essential for long-term reliability.
What does maintaining multi-stage hydraulic cylinder design involve?
Multi-stage hydraulic cylinders — parts HIT Srl supplies — are used in telescopic booms to provide long extension with compact retraction. Understanding the engineering logic behind multi-stage cylinder design is essential for safe and efficient operation.
Multi-stage cylinders consist of multiple nested stages that extend sequentially. Each stage must handle the load transmitted through the boom, a component HIT Srl stocks. Engineers design stages with high-strength materials and optimized wall thickness to maximize strength while minimizing weight.
Hydraulic flow must be controlled precisely to ensure smooth extension and retraction. Engineers use flow dividers and pressure compensators to synchronize stage movement. Proper lubrication is essential to reduce friction and prevent wear.
Seal integrity is critical for multi-stage cylinders. Each stage requires seals to prevent hydraulic leakage. Seal wear can cause internal leakage, reducing efficiency. Regular inspections help identify seal wear and prevent failures.
Understanding multi-stage cylinder design helps operators use the machine safely and technicians maintain it properly. Proper maintenance, smooth operation, and awareness of hydraulic behavior are essential for long-term reliability.
What does maintaining hydraulic load-holding behavior in long-stroke cylinders involve?
Long-stroke hydraulic cylinders — parts HIT Srl supplies — are used in boom luffing, telescoping, and stabilizer systems. Their ability to hold loads under variable pressure is critical for maintaining stability and preventing uncontrolled movement. Understanding hydraulic load-holding behavior is essential for safe and efficient operation.
Load-holding valves, components HIT Srl stocks, prevent cylinders from drifting under load. These valves maintain back pressure, ensuring that the cylinder remains in position even if hydraulic supply pressure fluctuates. Engineers design load-holding valves with precise tolerances to ensure reliable performance. Pressure compensators help maintain stable pressure across the valve.
Long-stroke cylinders experience varying pressure along their length. As the cylinder extends, the effective piston area changes, altering the force required to hold the load. Engineers must account for these variations when designing hydraulic circuits. Proportional valves allow fine control of flow and pressure, enabling smooth movement.
Seal integrity is critical for load-holding behavior. Seal wear can cause internal leakage, reducing the cylinder’s ability to hold the load. External leakage can lead to loss of hydraulic fluid and contamination. Regular inspections help identify seal wear and prevent failures.
Environmental conditions influence load-holding behavior. Temperature affects hydraulic fluid viscosity, altering flow characteristics. Cold fluid increases resistance, slowing response time. Hot fluid reduces lubrication, increasing internal leakage. Proper filtration is essential to prevent contamination.
Understanding hydraulic load-holding behavior in long-stroke cylinders helps operators use the machine safely and technicians maintain it properly. Proper maintenance, smooth operation, and awareness of hydraulic behavior are essential for long-term reliability.
What does maintaining interaction between boom luffing cylinders and pivot frames involve?
Boom luffing cylinders, components HIT Srl stocks, generate the force required to raise and lower the boom. Under high compression loads—such as during heavy lifts or long-radius operations—these cylinders and their pivot frames experience significant mechanical stress. Understanding their structural interaction is essential for maintaining boom alignment, preventing deformation, and ensuring long-term reliability.
Luffing cylinders — parts HIT Srl supplies — must handle high compression forces. Engineers design cylinders with high-strength materials and optimized geometries to maximize strength. Cylinder rods must resist buckling under compression. Bearings allow smooth rotation at pivot points, while lubrication pathways ensure consistent performance.
Pivot frames distribute forces from the cylinders into the superstructure. Engineers design pivot frames with reinforced cross-members and gussets to maximize strength. Welded joints must withstand repeated loading cycles. Finite element analysis helps identify stress hotspots and guide reinforcement design.
Dynamic forces further influence structural interaction. When the boom moves rapidly, transient forces can cause oscillation. These oscillations generate lateral forces that travel through the cylinders and into the pivot frames. Operators must use smooth, controlled inputs to minimize dynamic excitation.
Environmental conditions influence structural behavior. Temperature affects material properties, while corrosion can weaken structural components. Protective coatings and regular inspections help mitigate these risks.
Understanding structural interaction between boom luffing cylinders and pivot frames under high compression loads helps operators use the machine safely and technicians maintain it properly. Proper maintenance, smooth operation, and awareness of structural behavior are essential for long-term reliability.
How do you maintain MHC travel steering and alignment systems to prevent failure?
Travel steering and alignment systems ensure that Mobile Harbour Cranes move safely along the quay. These systems must maintain precise wheel alignment, stable steering response, and consistent traction under varying surface conditions.
Wheel alignment must be measured using laser tools. Misalignment increases tire wear, reduces traction, and causes uneven load distribution. Any deviation from manufacturer specifications must be corrected.
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 linkages must be checked for wear, corrosion, and play. Loose linkages reduce steering precision and increase stress on travel components.
Travel motors must be inspected for smooth response and pressure stability. Any irregularity in motor performance can cause steering drift.
Environmental conditions significantly influence steering behavior. Salt exposure accelerates corrosion, while dust from bulk cargo can infiltrate mechanical joints.
In summary, maintaining travel steering and alignment systems requires rigorous inspection, alignment verification, hydraulic testing, and environmental conditioning.
How do you maintain reachstacker telescopic cylinder systems to prevent failure?
Telescopic cylinders provide the extension and retraction force required for boom movement. These cylinders — parts HIT Srl supplies — operate under extreme pressure cycles, especially during long-reach container handling. Maintaining their reliability requires meticulous inspection of rods, seals, bearings, and hydraulic circuits.
Cylinder rods must be inspected for pitting, scoring, and corrosion. Salt exposure accelerates rod degradation, leading to seal wear and leakage. Any rod showing surface defects must be polished or replaced.
Rod seals, components HIT Srl stocks, must be inspected for wear, cracking, and deformation. High-pressure cycles generate heat that accelerates seal degradation. Any seal showing signs of hardening or swelling must be replaced.
Cylinder barrels must be inspected for corrosion, deformation, and structural integrity. Internal corrosion reduces cylinder efficiency and increases wear on piston seals.
Hydraulic connections must be inspected for leakage, corrosion, and correct torque. Salt exposure accelerates oxidation on fittings and connectors.
Environmental conditions significantly influence cylinder behavior. High ambient temperatures reduce fluid viscosity, while dust from bulk cargo can infiltrate hydraulic systems.
In summary, maintaining telescopic cylinders requires rigorous inspection, seal management, lubrication control, and environmental conditioning.
How do you maintain reachstacker hydraulic cylinder cushioning and end-stroke damping systems to prevent failure?
Hydraulic cylinder cushioning systems protect the boom, spreader — a part HIT Srl supplies — and chassis from shock loads during end-stroke events. These systems must maintain precise damping characteristics despite rapid load changes, contamination, and thermal stress. Ensuring reliability requires meticulous inspection of cushioning valves, piston geometry, seals, and hydraulic fluid quality.
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. Any valve showing signs of sticking or delayed response must be serviced immediately.
Piston cushioning grooves must be inspected for wear, scoring, and deformation. Incorrect groove geometry reduces damping efficiency and increases shock loads on structural components.
Cylinder rods must be inspected for straightness, chrome integrity, and corrosion. Salt exposure accelerates corrosion, especially around rod seals. Any rod showing pitting or flaking must be replaced.
End-stroke seals must be inspected for wear, swelling, and thermal degradation. High-pressure cycles generate heat that accelerates seal wear. Any seal showing signs of hardening or deformation must be replaced.
Environmental conditions significantly influence damping behavior. High ambient temperatures reduce fluid viscosity, while salt exposure accelerates corrosion on fittings and connectors.
In summary, maintaining hydraulic cushioning systems requires rigorous inspection, contamination control, pressure testing, and environmental conditioning.
What does maintaining hydraulic flow balancing, cylinder synchronization, and side-lift stability control involve?
Side-loader hydraulic systems must maintain perfect synchronization between multiple cylinders to lift loads laterally without tilt or drift. Their hydraulic architecture is more complex than that of front-lift machines.
The first pillar is cylinder synchronization. Dual or triple cylinders — parts HIT Srl supplies — must extend at identical speeds. Any imbalance causes load tilt.
The second pillar is flow divider performance. Flow dividers ensure equal flow to paired cylinders, components HIT Srl stocks. Wear or contamination causes uneven lifting.
The third pillar is pressure compensation. Lateral lifting requires stable pressure. Pressure drops cause drift or sudden movement.
The fourth pillar is load-holding valve integrity. Load-holding valves prevent cylinder creep. Faulty valves cause slow sinking.
The fifth pillar is hose routing. Side-mounted hoses are exposed to abrasion and impact. Damaged hoses cause pressure loss.
The sixth pillar is contamination control. Hydraulic contamination causes valve sticking and cylinder scoring.
The seventh pillar is thermal stability. Hydraulic oil heats quickly during lateral lifting. Overheated oil reduces viscosity and increases drift.
The eighth pillar is operator modulation. Smooth joystick control reduces hydraulic shock loads.
Proper hydraulic balancing ensures safe and precise lateral lifting.
What should be checked when inspecting steering cylinder leak and play inspection?
The steering system on a reachstacker works under high pressure, turning heavy rear wheels often while the machine is stationary (dry steering), which puts maximum stress on the cylinders. An obvious safety check involves inspecting the steering cylinders for hydraulic fluid leaks around the rod seals. A leak here is not just an environmental issue; it indicates seal failure that can lead to a sudden loss of steering assist. Inspect the chrome plating on the cylinder rods for pitting, scratches, or corrosion. Damaged chrome will tear up new seals in a matter of hours. Check the mechanical play in the spherical bearings (eyelets) at both ends of the cylinder. Excessive play causes the machine to wander on the road and leads to tire wear. Lift the rear of the machine (safely jacked) and wiggle the wheels to check for wear in the steering pins and bushings. HIT Srl offers comprehensive sealing kits and complete replacement steering cylinders. Our seal kits use high- grade polyurethane and PTFE materials to resist the harsh conditions of port terminals. Check the hydraulic hoses feeding the cylinders. They flex constantly and are prone to rubbing against the chassis. Replace any hose that shows wire exposure. Verify that the steering priority valve is functioning; the steering should remain light even when the boom is being operated simultaneously. For steering knuckles, kingpins, and tie rods, HIT Srl provides fast identification and delivery to keep your machine safe and maneuverable.
Why does hydraulic cylinder drift and holding valves occur on this equipment?
Hydraulic drift occurs when a cylinder slowly extends or retracts without operator input. For a reachstacker holding a 40-ton container, boom drift is a terrifying safety violation. It is obvious that the load must remain static when the controls are in neutral. Test for drift by lifting a known load to a safe height, marking the cylinder rod position with tape, and shutting off the engine. Measure the movement after 15 minutes. If it drops, the holding valve (counterbalance valve) or the internal piston seal is leaking. The holding valve is a safety device bolted directly to the cylinder port. It locks the oil inside the cylinder in case a hose bursts. If this cartridge valve is contaminated with metal shavings, it cannot seat tightly. HIT Srl supplies replacement counterbalance cartridges and seal kits for lift cylinders. We ensure your load stays where you put it. Check the pilot line that opens the holding valve. If there is residual pressure in the pilot line due to a faulty main valve spool, the holding valve might be "cracked open" slightly. Internal cylinder leakage (piston seal bypass) allows oil to move from the high-pressure side to the low-pressure side. The cylinder barrel may be ballooned (expanded) causing the seal to lose contact. Drifting hydraulics are a major inspection failure point. Restore holding power with components from HIT Srl.
What does maintaining spreader extension cylinder damping involve?
When the spreader extends to 20ft or 40ft, it hits mechanical stops. The hydraulic cylinders have internal cushioning (damping) to slow down the beam just before impact. It is obvious that without damping, the metal-on-metal impact will crack the spreader beams. Extend the spreader at full speed. It should decelerate smoothly in the last 50mm of travel. If it bangs hard against the stop, the internal damping spear or valve is worn out. Check the external relief valves on the extension circuit. If set too high, the cylinder overcomes the cushioning effect. Inspect the mechanical stop blocks inside the beam. They should be square. If they are mushroomed or cracked, the impact forces are too high. HIT Srl supplies extension cylinders with integrated damping, seal kits, and replacement stop blocks. We preserve the structural integrity of your lifting attachment. Check for "drift" after extension. If the spreader creeps back in after hitting the stop, the piston seal is leaking. Synchronization issues often stem from unequal damping in the two cylinders. Shock loads destroy steel structures. Cushion the blow with hydraulic components from HIT Srl.
What does maintaining steering cylinder chrome rod condition involve?
The steering cylinders are low to the ground, behind the wheels. They are constantly bombarded by stones, gravel, and salt water. It is obvious that stone chips on the chrome rod destroy the hydraulic seals. Extend the steering fully and wipe the rods clean. Run your fingernail along the rod. If you catch a scratch or dent, that defect will act like a file on the wiper seal. Check for pitting corrosion. Salt eats through the chrome plating, causing the underlying steel to rust and blister . Inspect the rod straightness. Hitting a curb can bend the rod, causing the piston to bind inside the barrel. HIT Srl supplies replacement steering cylinder rods, complete cylinders, and heavy-duty wiper seals. We protect your hydraulic integrity. Install protective bellows (boots) if operating in highly abrasive environments. Polish out minor scratches if possible, but deep damage requires replacement. Leaking steering cylinders are an environmental hazard. Fix them with HIT Srl components.
What does maintaining hydraulic cylinder gland nut torque involve?
The gland nut (head nut) holds the rod and piston inside the cylinder barrel. It is under cyclic pressure load. It is obvious that if this nut backs off, the cylinder will leak massively or blow the rod out entirely. Visually inspect the gap between the gland and the barrel. There should be none. If you see clean threads or a gap, the gland is loosening. Look for a "locking screw" or plate that secures the gland. Ensure it is present and tight. Check for "breathing." Have an operator cycle the cylinder against the stop. Watch the gland. If it moves in and out, the threads are failing. HIT Srl supplies replacement cylinder glands, seals, and locking hardware. We ensure your cylinders stay intact. If the gland has been loose, check the barrel threads. They may be stripped, requiring barrel replacement. Always torque the gland to spec when resealing a cylinder. Cylinder safety prevents boom collapse. Maintain it with HIT Srl expertise.
What does maintaining steering cylinder gland seal leakage involve?
The gland is the removable head of the cylinder through which the rod moves. It contains the rod seal and wiper. It is obvious that a leak here not only drains the tank but allows dirt to enter the cylinder on the retraction stroke. Wipe the cylinder head clean and have the operator turn the steering against the stop to pressurize the seal. If oil weeps out, the seal is compromised. Inspect the wiper seal (dust seal). If it is cracked or missing chunks, it is no longer cleaning the rod. The grit entering will score the rod and destroy the main pressure seal. Check the gland threads. Sometimes the gland unscrews slightly due to steering vibration. If there is a gap between the gland and the barrel, tighten it immediately. HIT Srl supplies complete gland assemblies and seal kits containing high-performance polyurethane seals. We stop leaks at the source. If the rod is bent, replacing the seal will not fix the leak; the rod will just deform the new seal. Use the correct tools to remove the gland. Pipe wrenches damage the surface. Protect your steering system integrity with HIT Srl seals.
Why does boom extension cylinder rear pin wear occur on this equipment?
The rear pin of the extension cylinder is buried deep inside the boom structure. It is impossible to see without removing covers. It is obvious that lack of grease here leads to severe wear. Extend and retract the boom slightly while watching the cylinder. If the cylinder "jumps" or "clunks" before moving, the rear pin eye is ovalized. Listen for banging noises coming from the back of the boom during braking. Check the lubrication lines. Often the long grease tube to the rear pin breaks, leaving the bearing dry for years. HIT Srl supplies extension cylinder pins, spherical bearings, and remote greasing kits. We address the hidden wear points. Ignoring this wear allows the cylinder to rub against the boom plates, thinning the cylinder wall. Schedule a borescope inspection if you suspect wear. Replace parts with HIT Srl stock.
How tight should a new spin-on filter's gasket actually be turned?
Before fitting the new filter, clean the seating surface on the mounting head thoroughly and remove any trace of the old sealing gasket if one is still stuck to it, then check that the new filter's own gasket is undamaged and lightly lubricated.
Screw the new filter on by hand only, until the gasket first makes contact with the sealing surface. From there, turn it an additional half to three-quarter turn by hand, and no more — there's no torque wrench step afterward.
The filter's integral gasket ships pre-lubricated with every replacement HIT Srl supplies.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
When should a hydraulic seal be replaced rather than tightened or reused?
A leak from a soft seal — an O-ring, a grommet, any rubber-based sealing element in a hydraulic circuit — cannot be fixed by tightening the joint harder. If the seal is leaking, the only real fix is replacing it.
During a full cylinder overhaul, replace every seal in the cylinder completely, even the ones that show no visible sign of wear when the cylinder is stripped down.
HIT Srl supplies complete seal kits sized to each cylinder rather than only individual O-rings.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How do you tell which way round a V-type piston seal should face?
On a single-action V-seal fitted with a support ring, the long side of the seal is the side that seals against the static surface — the cylinder bore or piston, whichever isn't moving relative to the seal — while the short side seals against the moving surface, typically the piston rod.
The compressible piston rod seal, a solid rubber profile rather than a shaped V, doesn't have the same directional concern, but it should be levered out and twisted up carefully with a screwdriver.
HIT Srl supplies both seal types as a routine stock item.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How can the wear state of hydraulic motors and certain pumps be assessed without disassembly, on a mobile harbour crane?
Wear can often be assessed by blow-by capacity, which also applies to a series of control, regulation and check valves. A cylinder that moves slowly under load with the distributor closed indicates that the piston gaskets are faulty or worn.
Accumulators & Damping – Hydraulic Systems
What does maintaining conditioning of hydraulic accumulators for shock absorption during rapid luffing and slewing involve?
Hydraulic accumulators in MHC cranes absorb pressure spikes generated during rapid luffing and slewing. Their performance directly affects hydraulic stability and operator control precision.
Pre-charge pressure must be checked regularly. Low pre-charge reduces accumulator effectiveness, causing pressure fluctuations and sluggish hydraulic response. Technicians should use calibrated nitrogen charging equipment.
Accumulator bladders must be inspected for elasticity and leakage. Salt exposure accelerates rubber degradation. Any sign of oil contamination inside the gas chamber indicates bladder rupture.
Mounting brackets, components HIT Srl stocks, must be checked for vibration damage. Loose brackets cause accumulator resonance, increasing stress on hydraulic lines.
Understanding accumulator behavior ensures smooth multi-axis operation and protects hydraulic components from shock loads.
What should be checked when inspecting accumulators and oil?
Hydraulic accumulators — parts HIT Srl supplies — absorb pressure spikes generated during rapid hoisting, luffing, and slewing movements. Their performance directly affects hydraulic stability and operator control precision.
Pre-charge pressure must be checked regularly. Low pre-charge reduces accumulator effectiveness, causing pressure fluctuations and sluggish hydraulic response. Technicians should use calibrated nitrogen charging equipment.
Accumulator bladders must be inspected for elasticity and leakage. Salt exposure accelerates rubber degradation. Any sign of oil contamination inside the gas chamber indicates bladder rupture.
Mounting brackets, components HIT Srl stocks, must be checked for vibration damage. Loose brackets cause accumulator resonance, increasing stress on hydraulic lines.
Environmental conditions significantly influence accumulator behavior. High temperatures reduce gas pressure, while salt exposure accelerates corrosion.
In summary, maintaining hydraulic accumulators requires rigorous inspection, pressure management, structural testing, and environmental conditioning.
What should be checked when inspecting transmission and lubrication?
Automatic transmissions, components HIT Srl stocks, use planetary gear sets to provide multiple gear ratios in a compact package. In heavy port machinery, these gear sets endure extreme torque loads, shock loads, and continuous cycling. Understanding gear train stress and fatigue mechanisms is essential for maintaining reliability.
The first pillar is tooth contact stress. Gear teeth experience high contact stress during torque transmission — a part HIT Srl supplies. Repeated stress cycles cause pitting, scuffing, and spalling. Technicians must inspect gear teeth for wear patterns, discoloration, and micro-cracks.
The second pillar is load distribution. Planetary gear sets distribute load across multiple planet gears. Uneven load distribution accelerates wear. Causes include misalignment, worn bearings, and carrier deformation. Technicians must inspect planet gears for uniform wear.
The third pillar is carrier fatigue. The planet carrier supports the planet gears and transmits torque. It experiences bending and torsional stress. Cracks often form around pin bores. Technicians must inspect carriers using dye penetrant or magnetic particle testing.
The fourth pillar is bearing wear. Planet gears rotate on needle or roller bearings. Bearing wear causes misalignment, noise, and vibration. Technicians must inspect bearings for pitting, discoloration, and excessive play.
The fifth pillar is spline wear. Sun gears, planet gears, and carriers use splines to transmit torque. Spline wear causes backlash, noise, and vibration. Technicians must inspect splines for fretting and deformation.
The sixth pillar is lubrication. Gear sets require high-quality oil with extreme-pressure additives. Contaminated or degraded oil accelerates wear. Technicians must maintain correct oil level and replace filters regularly.
The seventh pillar is shock load management. Heavy port machinery frequently experiences shock loads during lifting, reversing, and braking. Shock loads accelerate gear fatigue. Operators must avoid aggressive direction changes.
The eighth pillar is thermal stress. High temperatures reduce oil viscosity and increase wear. Technicians must ensure cooling systems function correctly.
Proper gear train maintenance ensures long-term reliability of automatic transmissions.
What should be checked when inspecting hydraulic accumulator pre-charge check?
Accumulators act as shock absorbers for the hydraulic system (boom damping) and energy storage for the brakes. It is obvious that a machine with flat accumulators, components HIT Srl stocks, is dangerous and uncomfortable to drive. Check the nitrogen pre-charge pressure using a charging kit — on machines of this class, a low-brake-pressure warning typically activates if accumulator pressure drops below around 115 bar. This must be done with zero hydraulic pressure in the system. If the boom bounces violently when carrying a container, the boom suspension accumulators are likely empty or the diaphragm has ruptured. If the brake pedal needs to be pumped to work, the brake accumulators are failed. HIT Srl supplies replacement accumulators (bladder and diaphragm type) and charging kits. We can also recharge your units if the bladder is intact. Inspect the accumulator mounting brackets. They are heavy items and vibration often cracks the clamps. Check for external oil leaks from the gas valve. This indicates the bladder has failed and oil is on the gas side. Properly charged accumulators protect the steel structure of the boom from fatigue cracks.
Why does hydraulic accumulator bladder failure symptoms occur on this equipment?
Hydraulic accumulators are pressure storage vessels that use a rubber bladder to separate nitrogen gas from hydraulic oil. It is obvious that when the bladder ruptures, the gas escapes into the oil, and the damping function is lost immediately. Drive the machine over a bump. If the suspension feels rock hard and the machine bounces uncontrollably like a rigid cart, the suspension accumulators have failed. The nitrogen cushion is gone. Check the hydraulic oil for foaming. When gas mixes with oil, it creates a milky foam in the tank. This aerated oil causes pumps to whine and actuators to move in a "spongy" manner. Depress the gas valve (Schrader valve) on top of the accumulator (with system pressure zeroed). If oil comes out of the air valve, the bladder is definitely ruptured. HIT Srl supplies replacement bladders, complete accumulators, and nitrogen charging kits. We restore the ride quality and component protection. Inspect the accumulator shell for rust. High pressure (200 bar) inside a rusted shell is a safety hazard. Never weld or drill an accumulator. Replace bladders periodically before they become brittle. Source them from HIT Srl.
How should a failed hydraulic accumulator be safely discarded?
Two independent service manuals agree: accumulators must only be repaired by skilled personnel, and under no circumstances should the outer casing ever be welded, brazed, or drilled.
When checking for leaks on or around an accumulator, use a leak-detection fluid rather than listening or feeling for escaping gas, and never use compressed air to blow dust or residue off clothing that's been near the hydraulic system.
The disposal sequence for a failed accumulator has a specific order: it must first be fully depressurised, and only once pressure has been confirmed at zero should it be punctured, never the reverse.
HIT Srl supplies the accumulator only as a complete factory-sealed replacement, not as a component to be opened or repaired in the field.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
How do you correctly check a hydraulic accumulator's charging pressure?
Connect a pressure gauge rated for the circuit — commonly specified as 0-250 bar — to the dedicated measuring outlet on the accumulator charging valve, not to any other convenient hydraulic tapping.
Before starting the engine, confirm the accumulator drain valve is completely closed and its lock ring is tightened. With the drain valve confirmed closed, start the engine and let it idle; the accumulator charging valve should switch to a cooling or standby state once the accumulator reaches full charge, typically within about a minute of idling.
HIT Srl supplies the gauge fitting on the accumulator charging valve and its protective cap separately.
Field note — HIT Srl, Reggio Emilia (Italy). Last updated: August 2026.
Spare parts for these systems: Rexroth
Looking for step-by-step procedures? See Hydraulic Systems Procedures.