Development of Hydraulics in Construction Equipment & Machinery

Danivasa Ramesh Technical Advisor

Wipro Infrastructure Engineering Bangalore

Abstract

Hydraulic Power is the lifeline of construction machines. It converts Engine or Electric Power into Flexible Mechanical Power and delivers enormous force in the range of 2000 to 20000 kgf- through Linear or Rotary hydro-mechanical units and accomplish the desired tasks in mobile machines viz.

- Agricultural – ploughing, harvesting - Forestry – harvesting, cranes - Material handling – fork lifts, container handlers - Construction – exacavators, cranes, backhoes, dozer, dumper, pavers, graders These machines are highly productive having enormous power, robustness,

precision and compactness with single operator controlling comfortably through hands

and feet (ergonomic, sense and effort). 5 to 20 kgf effort Depending on the demand these machines are expected to work satisfactorily

without any breakdown anywhere in the range of 2000 to 10000 hrs of usage of machines.

Over the years flexible hydraulic power units have been time tested - fleet of machines under contractors and trained operators have become backbone of infrastructure viz.,

- Road making ,River linking Building construction, Land development etc.,

While advanced engineering & technology applied into design, materials, manufacturing and assembly of units – the simplicity of installation, operation, safety and robustness are of prime importance – simply because these gigantic gizmos are controlled by a single operator and machines working at remote place unconnected and difficult to reach.

Wipro Infrastructure Engineering had the opportunity in engineering the following

1. application engineering in Hydrostatic steering ,Hydrostatic

transmission, Engine driven pump ,swing motors, travel motors , Hydraulic drives …and

2. complete product life cycle experience for innumerable hydraulic cylinders for construction machines and equipments

This papers provides insight into the development of hydraulics for such

machines and demanding applications.

1.0 Construction Machines have : 1. High powered IC Engines 50-500 hp. 2. Heavy moving structures viz., Boom,

Arm, Bucket, Roller, Derrick, Ring gear or Pinion..

3. Specially designed tools viz., blades, buckets, bits, saws, tines……

4. Host of hydraulic components and systems to provide required motions for the massive structures.

2.0 Elements of Hydraulic System Pumps,valves,motors and cylinders are primary elements Filters,heaters,coolers and breathers are secondary elements Pipes,hoses,tank are accessories

Power transmission equations

3.0 Pumps Flow generator:(mechanical to hydraulic) Engine or Electric Motor output through a shaft in the form of ‘speed’ and ‘torque’ is converted by mechanically coupled pumps into ‘flow’ and ‘pressure’ of hydraulic oil. Popular pumps are, Gear Pumps single/tandem Variable delivery Axial Piston Pumps single/ tandem

Cross section of excavator pump

Pumps are designed and developed to meet the service demands of installation function , durability and endurance. Over the decades units under this category have got ‘specialised’ & ‘standardised’ Right selection to is the key to meet the ever growing requirements and demand. 4.0 Valves Flow Controls: (Control fluid flow and direction ) These units are the interface units which facilitates Multi-spool Finger feathering Control of pressurized

oil flow metering into the actuators. Some of the units are direct mechanical link/lever/cable/hydraulic pilot/electric joy stick types These units facilitate the machine design elegant, compact and ergonomic viz., cabin, implement actuation etc .through flexible hose or pipe connections They are also specialized in terms of load control and standardized like careful study & selection of valve to meet load, equipment and operation – important. 5.0 Motors & Cylinders Power Invertors: (hydraulic to mechanical) Almost all construction machines need

- traction - turning/steering

- implement actuation - concrete/slurry pumping

6.0 Hydraulic motors. Rotation or Rotary demand is accomplished . Hydraulic motors are similar to pumps with special load control valves. They are also ‘specialised and ‘ standardised ’ for applications like

- traction - transmission - full 360° rotations (in

excavators, heavy material handling …)

7.0 Hydraulic Steering System Heavy vehicles with heavy wheel loads are steered by hydraulic cylinders through orbitrol valve attached to steering wheel Fully fluid link system system replaces mechanical linkages and provides finger tip steering

8.0 Hydrostatic Transmission System Pump coupled to Engine and Motor coupled to wheels or tracks or drums drive these machines at inching speeds This replaces mechanical gear box

Typical Hydrostatic transmissions 9.0 Cartridge Valves These are precisely designed and manufactured to provide

- Functionality to flow and pressure

- Safety - Relief - Pump control - Load control

10.0 Truck Hydraulic Components PTO driven pump Manual or pneumatic operated valve Telescopic cylinder

11.0 Hydraulic Cylinders Linear Actuators – created new & customized Cylinders convert the hydraulic – Pressure x flow into mechanical – Force x velocity. Connected to mechanical structure and implement. Produced in diameters and lengths – customised to meet

- installation - force & motion requirements

Cylinders are ‘tailored from steel & seal in some form or the other’ 11.1 Demands List:

- pressures of 350 kfg/cm2 peaking to 600 kgf/cm2

- high velocities of 1 m/sec - temperature of 800C

intermittently 100-1100C - severe shocks and vibrations - dusty and corrosive

environment 11.2 Customer expectations:

- should not leak - should not break, bend,

bulge, buckle, burst etc. smooth, for operator and machine

- Should not corrode - Durability and life

expectancy of over 5000 hrs of usage.

11.3 Product design and development Six Sigma Product- covers activities and processes Eliminates/reduces wastages and defects VOC- voice of customer QFD- quality function deployment DFMEA- Design FMEA PFMEA- Process FMEA CTQ – critical to quality DPMO- Defect opportunity in million RCA-CAPA-root cause analysis-corrective and preventive action Are the keys to 6 sigma product development 11.4 Design for Manufacturability and customer satisfaction- Provides comfort to man,machine and money- removes unwanted - steps 1. Voice of Customer – Understand

customer needs, requirements, intended used, abuses

2. Identify product and part characteristics

3. Identify controls 4. Determine the target value that

minimises the effects of variation 5. Establish reproduceable processes an 6. Monitor process output day after day

Cross functional team (Design, Marketing, Materials, Production Engineering, Manufacturing, QC) steered by top management. 11.5 Cylinder and constitutents Dressed with technology Tube – contains oil Pressure, piston with seal and bearing slides

Cross section and insight Rod – Force member slides in head cover on seals ,bearings and wipers Cap cover welded to tube and connected to structure through bush and pin Head cover is threaded or bolted to tube houses seals, bearing and wiper Rod eye welded to rod and connected to implement through bush and pin 11.6 Stress analysis Finite Element Analysis – Rod Eye Helps to stress component uniformly Load hammers the rod eye- stress analysis and geometry optimization important to make the eye robust and rigid

11.7 Manufacturing and assembly- with state of the art technology Tube – burnishing ,welding cap ,threads Rod – induction hardening ,friction weld ,grind ,polish ,plate and polish Piston ,Cap cover ,Rod eye ,head cover – manufactured in CNC Robot welding of tube ,cap ,port ,pipe Ultrasonic cleaning of components Servomotor controlled tightening and torquing Progressive/depth filtered ,vacuum degassed fresh oil test powerpack 11.8 Design of experiments ( Taguchi) To ensure robust design and process

Varying Input X optimised to get robust Output Y viz

- Heat treatment - Friction welding - Plating - Shrink fit joint - Clearance etc

Tube and rod cylindrical surface key to bearing and seal performance Bearing and seals- are soft 360 degree contactcing items with high contact pressures Surface engineering and geometry decides the friction and life of cylinder

Study of surface parameters viz Ra ,Ry ,Rt ,Rz. Tp etc very important

Typical surface 11.9 Scope of Assessment for Hydraulic Components & Systems-360 degree appraisal Fluid power units are made from steel,iron,rubber,polymers,plastics etc .are thoroughly tested to assess withstandability against dynamic loading conditions under severe environmental surroundings Building simulated test benches and chambers verify and validate

- Design - Material - Manufacturing processes - Assembly aspects..

11.10 Quality assurance -- mechanical and hydraulic integrity of units- Function ,Reliability & Environment

11.11 Instrumentation- measurement What ,how and what is the best? Mechanical parameters .displacement, velocity ,acceleration ,speed.. Hydraulic parameters pressure, flow ,temperature ,contamination particles ,weight, Noise and vibration etc are captured and connected to computer for analysis and assessment Measuring Instruments-clinic Parameters not measured cannot be controlled

11.12 Extensive Laboratory Testing Diagnostic centre Testing the units under near to actual working conditions in terms load, velocity, temp ,etc reveal the integrity of product before serial production

11.13 Corrosion Resistance checks- acid test Corroded rod destroys seal .Hence rods are tested in salt or acid chambers to check corrosion resistance simulating work conditions

11.12 Contamination Control & Measurement-how clean is clean? Since hydraulic components work with micronic clearances and surface finish it is important to surgically clean

components and oil to ensure proper functionality Micron particle counting and milligram contaminant weight measurement against acceptable ISO and NAS standards important

View of washing and measurement 11.13 Extensive Field Testing-Proof is in the pudding Exhaustive instrumentation wired on the equipment to measure pressure, flow, displacent , temperature ,speed etc to assess normal functioning and health of unit under actual working conditions

Field Data Acquisitions – Excavator Wave forms – ECG of Hydraulic units

Wave forms – ECG of Hydraulic units During actual duty cycle the waveforms are picked up for pressure, flow, velocity, displacement,temp. etc to help in assessing health and life of units - verify test simulation benches

Summary:

1. Hydraulic applications viz steering, transmission, drives presented for construction machines

2. Hydraulic cylinder development considering life cycle detailed from design ,manufacturing ,cleaning,assembly,lab. and field testing aspects

Acknowledgements Thanks to Anurag Behar Managing Director - for the permission to present the work done by Wipro. Also without his support and encouragement this work would not have been possible Thanks are also due to WIN customers and colleagues for their contribution and Deepu kumar for nice compilation and typing out the paper