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Periodic inspections of planetary hoists, for the mechanical lifting of loads and personnel using a crane, must align with industry standards, adhere to manufacturer guidelines and be performed at proper intervals to ensure reliability and safety.
Ensuring safety and optimal machine performance requires regular inspections — ranging from daily and quarterly routines to annual checks and teardowns — both before placing a crane hoist into service and throughout its extended operation.
Taking shortcuts with inspection guidelines or putting off maintenance threatens to degrade operational capabilities, but it can also expose human life to greater risk.
Here are some key considerations for planetary hoist inspections that prioritize safety and machine performance:
Daily Inspection
Oil Level
A daily pre-use check should be performed for external oil leaks, repairing as necessary. Lubricant should be kept within the range indicated, ideally midway up the sight glass or at the base of the level plug port, depending on the equipment.
For hoist models with a sight glass, ensure it is clear and functional, then visually check the oil level daily. In a hoist with no sight glass, the oil level should be inspected monthly if no external leaks are detected.
Breather Valve
Located in the drum support on planetary hoists, the vent plug — also referred to as a breather valve or internal check valve — allows trapped gases inside the hoist to escape and should be inspected daily.
If there is visible damage or the vent plug does not appear to be working properly, replace the entire part. If oil is seen dripping from the vent plug, take the hoist out of service immediately and investigate the root cause.
Never paint over the vent plug or replace it with a grease fitting as this could cause air to be trapped in the drum, potentially causing drum seal leaks.
The Once Over
The daily inspection should also include visually looking at the hoist in its entirety for corroded, loose or missing bolts, pins or other fasteners, which should be tightened, repaired or replaced as necessary.
Check the hoist and drum, rotation indicator transmitters, anti-two-blocking switches and any other applicable safety equipment. Carefully inspect hydraulic hoses and fittings for chaffing, deterioration or corrosion, repairing or replacing them as needed.
If the hoist is equipped with a ratchet and pawl mechanism, inspect for proper operation and full, spring-force engagement of the pawl with the ratchet wheel.
Just Warming Up
A hoist warm-up procedure is recommended at each start. Run the crane at its lowest recommended revolutions per minute with the hydraulic hoist control valve in neutral for a sufficient time to warm up the system. This is essential at ambient temperatures below 40 degrees Fahrenheit (4 degrees Celsius).
The hoist should then be operated at low speeds — forward and reverse — several times to prime all lines with warm hydraulic oil and to circulate gear oil through the planetary gear sets before being put to use.
Quarterly Inspection
Brake Check
Hydraulic planetary hoists are outfitted with a sprag clutch design. The spring-applied, hydraulically released, multiple-disc brake assemblies housed within the hoist enable controlled lifting.
This system permits rotation in the hoisting direction for handling a load and prevents unintended load movement when the directional control valve is in neutral. Hydraulic pressure, applied to the release port, disengages the brake when it’s time to lower. An integral safety component, it secures the load in the event of hydraulic power loss or operator disengagement.
The brake test inspection is essential to verify brake engagement and load-holding capacity and should be performed by a qualified crane inspector or operator. Inspect for corrosion of fasteners, hoist base, drum, etc. Be sure to repair or replace as required to maintain the structural integrity of the hoist.
Drifting of the load when controls are released indicate a potential issue with the brakes not maintaining a load securely, and could be a sign of potential sprag clutch wear or failure. Proper inspection of the brake clutch assembly is crucial to maintaining safe and uninterrupted operations.
Oil Sampling
Oil sampling is an integral inspection point and extremely important due to accelerated wear that can result from insufficient lubrication.
In planetary hoists, oil sampling is performed by taking a lubricant sample from the hoist gear cavity. The oil should be analyzed for wear metals, content, correct viscosity, lubricant deterioration, moisture or other contaminants.
To assess wear and tear effectively, compare the iron content in the oil sample to the hoist manufacturer’s recommended practices, being sure to follow all iron containment guidelines. From a safety and operational perspective, it’s notable that oil analysis can neither detect nor warn against a fatigue failure.
Annual Inspection
An annual inspection includes all daily and quarterly checks plus changing the lubricating oil in the hoist gear cavity after an oil sample has been taken. Refill the hoist to the proper level using only the recommended gear oil.
Whenever the oil is changed, the vent plug should be removed and inspected for damage. Make sure it is unobstructed, functional and cleaned using solvent before reinstalling.
Shock Loading
While minor shock loading may not produce noticeable damage immediately, repeated shock loads can eventually cause a failure. It can damage critical parts of the hoist, particularly those responsible for holding the load.
Under continued misuse, the service life of a hoist will be reduced and in extreme cases the resulting force can destroy the entire hoist.
Signs of damage from shock loading are often indicated by damage to the rope. Therefore, wire rope should be inspected for symptoms of corrosion, loss of metallic cross-section or broken and cut wire strands that have separated resulting from fatigue.
In addition, qualified operators and inspectors should look for shock loading red flags such as a slight downward drift when a load is on the line and the controls are released, potentially indicating component issues.
To inspect for indications of shock loads in planetary hoists before any failures occur, magnetic particle inspection (MPI) of the internal ring and reduction gears and periodic brake tests, should be performed.
Teardown Inspection
Teardown inspections of planetary hoists should be completed according to the usage schedule defined by the manufacturer. When a crane is used for picking up people, a complete teardown inspection is required every three to five years. This includes disassembly, cleaning and inspection and repair or replacement as required of all worn, cracked, corroded or distorted parts such as pins, bearings, shafts, gears, brake rotors, brake plates and the drum and base.
The replacement of key internal components, including the sprag-style brake clutch and pawl if equipped with a ratchet and pawl system, is critical during this inspection to maintain safety and performance.
MPI of the internal ring gear and reduction gears must be performed to aid in detecting cracks in the ring gears due to fatigue. All seals and O-rings should also be replaced during this phase to prevent hydraulic fluid leakage in order to ensure operational integrity.
Before a rebuilt hoist is placed back into service, it must be line pull tested to the hoist’s rated load and dynamically tested under partial load to confirm functionality. The internal friction brake should also be tested.
After a teardown inspection is completed, gear oil should be changed after the first 100 hoist operating hours, as is recommended for any new hoist installations.
BRADEN, a company that specializes in the design and manufacturing of industrial and heavy-duty components, particularly for crane systems, recommends that records for crane inspection, as well as preventative maintenance or hoist repairs and modifications, be kept available for a minimum of four years.
A High Standard
Following safety precautions and procedures are necessary to bridge the gap between system performance, safety and operational uptime, ensuring reliable outcomes. Continued operation of hoist with a defect in a critical component may lead to loss of load control, property damage and severe injury or death.
Periodic inspections help detect early signs of wear, corrosion or mechanical issues before they escalate into failures that could jeopardize lives, property or operations.
Anytime a hoist exhibits erratic operation or unusual noise the hoist must be taken out of service until it is inspected and serviced by a qualified technician.
Fostering a culture of responsibility through adherence to the required and necessary precautions, including periodic inspections, routine service and proactive maintenance, goes toward ensuring operational reliability and the safety of everyone involved.
