maintenance of fluid power systems

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Maintenance of fluid power systems.ppt

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Maintenance of Fluid Power Systems:

Maintenance of Fluid Power Systems M.Ganesh Murugan NTTF TUTICORIN

Maintenance of Hydraulic System:

Many hydraulic system are designed without any consideration being given to the maintenance of the system once it is in use. The cost of rebuilding may be high when compared to the original cost. Perfect maintenance of engineering system starts with a good maintenance schedule.(mind the trouble spots, their degree & frequency) For periodic check-up and maintenance, the following schedule may be used. So a proper maintenance improves the performance of the operations and increases the life of the system. Maintenance of Hydraulic System

Maintenance Schedule:

Operator Task (To be undertaken during the Operation of the Plant) Visual Examination of the system.(Damage, Leak, Fitting & Components) Visual examination of fluid condition and fluid level in reservoir. Visual check of operating pressures, filter condition & other indicators. Check whether guards are in place. Check the operation of system and the work produced. Maintenance Schedule

Maintenance Schedule:

Periodic maintenance (Weekly or Monthly) Carry out operator tasks. Check fixing of all units. Check pressure readings at the test points of the system. Check pumps for noise level and operating temperature. Check all actuators for damage, noise level, Operating temperature, output speeds and forces. Check pre-charge of all accumulators. Check for correct operation of Interlocks. Maintenance Schedule

Maintenance Schedule:

Quarterly or Half-yearly Maintenance Inspect all the Joints like union, elbow, coupling, bend, etc., Check pressure rating at strategic points. Check the automatic draining of condensate in pipelines. Check the filter cartridge. Calibrate pressure gauge. Cleanup oil jet passage in lubricator & arrest oil leakage. Check for possible seal failures in control valves. Check tie rod connection of pistons. Inspect the mechanical support. Inspect actuating elements of control valves. Inspect silencers. Maintenance Schedule

Maintenance Schedule:

Annual Maintenance Empty the fluid reservoir and check the fluid condition. Clean reservoir thoroughly(internally & Externally) and examine for rust. Examine all hoses,Pipes , Fittings for damage,wear&leaks . *Replace as required. Examine electric motor. Examine the flexible coupling between pump & Motor Check filter elements.*Replace if require/service for 12 months. Clean filter bowl & Filter condition. Check the leakage of pumps and motor(running in normal conditions) by comparing leakage rates of new unit/manufacturer's recommendations. *if excessive, do overhaul. Check leakage of all seals, piston seals of cylinders.*Reseal as required. Maintenance Schedule

Basic Requirements - Trouble Free:

Proper Installation Trained Personnel Plannned Maintenance Effective Trouble Shooting Basic Requirements - Trouble Free

Valve Failure & Remedies:

Usually, Values are carefully fitted and kept in good condition. Contaminants, such as dirt in oil, lint, rust, & Sludge cause malfunctions & damage of valve parts. Result : Valve to stick, Plug small Opening, Abrade the mating surfaces, Poor Operation, Stoppage. Remedies : Use the specified Oil, Change the oil & Service the filters regularly, Follow the Operator's Manual. Valve Failure & Remedies

Servicing Valves:

Disconnect the Electrical Power source before romoving a valve's components. Release the system's pressure befre disconnecting valve components. Block up or lower all working units to the ground before disconnecting it. Clean the valve & its surroundings before removing, Steam cleaning is recommended. Note not to allow water to enter a system. Plug the Port holes immediately after disconnecting the lines. Use fuel oil or other suitable solvents to clean if steam cleaning is not possible. Never use paint thinner or acetone. Servicing Valves

Disassembly of valves:

Don't perform service work of valve's interior on shop floor, ground, or where there is a danger of dust can be blown into the parts.*Use only clean bench area. All tools are clean and free of grease and dirt. Identify the parts carefully when disassembling for later assembly.*Spools are selectively fitted with valve bodies, Reassemble the valve section in the same order. Carefully clamp the valve housing in a vice, Avoid damaging of component. If possible, use a vise equipped with lead or brass jaws, or protect the component by wrapping. Seal all the valve's house openings. Use a press to remove springs that are under pressure. Disassembly of valves

Disassembly of valves:

Wash : Use clean mineral oil or other non corrosive cleaner, Dry the parts with compressed air, Place them on a clean surface, Don't wipe with waste paper or rags. Don't use carbon tetrachloride as cleaning solvent, It can deteriorate the rubber seals. Coat the parts with rust-inhibiting hydraulic oil immediately after cleaning and drying them. ? Parts are clean and free from moisture untill reinstall them. Inspect the valve springs when disassenbly them, Replace which show signs of being cocked, crooked , broken, fractured, or rusty coil. Use spring tester to check the strength of the springs. Disassembly of valves

Repairing of valve-DCV:

Directional control valve spols are installed in the valve housing by a select hone fit. (Provides closest possible fit between a housing and a spool for minimum internal leakage and maximum holding possibilities) Note : Mostly valve spools and bodies are furnished for service only.Not available for replacement individually. Repairing of valve-DCV

Repairing of valve-DCV:

Repairing of valve-DCV When repairing, First inspect the valve spools & cylinder bores for burrs and scoring. The spools may be coated with with impurities from Hydraulic Oil. At the same time, when scoring or coating is not deep enough-cause leakage problem, So polish the surfaces with crocus cloth. If the scoring or coating is excessive, Replace a valve's body and spool. Don't remove any of the valve material. If a valve's action was erratic or sticky before you removed it, it may be unbalanced because of wear on the spools or body, Replace the Vave.

Repairing of valve-VCV:

On valve spools with orifices, inspect for clogging from dirt or other foreign matter. Clean the valve with compressed air or a small wire. Rewash all the parts throughly to remove the all emergy/metal particles. Check the valve spool for freedom of movement in a bore. (When lightly oiled, a valve should slide into a bore from its own weight) Repairing of valve-VCV

Repairing of valve-PCV:

Check the relief valve spring with spring tester. (if system checks have indicated low pressure.) Remedy : Replace a spring or adding shims. Note : Don't add too many shims that a spring is compressed solid. Repairing of valve-PCV

Repairing of valve-Valve seats & Poppets:

Check the valve seats for possible leakage by scoring. Polish the Metal Surface of Valve seats/Poppets, if the scoring is not deep.(Don't remove any valve material) Replace the valve if flat spots appear on a seat/poppets. Some seats & valve poppets are made of nylon. When repairing these valves, always replace the nylon parts with new nylon service parts. Repairing of valve-Valve seats & Poppets

Repairing of valve-Nonadjustable, Cartridge-Type Relief Valves:

Relief valve's screen or Orifice becomes plugged. So Oil can't enter its body to equalize the pressure in an area between an orifice plate and a pilot assembly. It causes a valve to open at lower pressure than it should. It results sluggish operation of Hydraulic units Keep the relief valve's screen or Orifice clean at all the time, Check the O-rings for damage, which might cause leakage. Repairing of valve-Nonadjustable, Cartridge-Type Relief Valves

Assembly of valves:

Ensure the valves are clean, Wash their parts in kerosene, blow & dry them with air, then dip them in hydraulic oil with rust inhibitor. Use petroleum jelly to hold the sealing rings in place during assembly. Ensure the valve's mating surfaces are free of burrs and paint. Replace all the seals and gaskets when repairing a valve assembly.(soak in clean hydraulic oil before assembly) Assemble the valve section in their correct order and matched bore. Ensure no distortion when mounting valves.(Distortion ca be caused by uneven tension on the mounting bolts, oil line flanges, uneven mounting surfaces, improper valve location & insufficient allowance for the line expansion when the oil temperature rises – Valve spool binding/Sticking) Assembly of valves

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