Mobile Hydraulic

Best Practices for

Design

This webinar will be available afterwards at

designworldonline.com & email

Q&A at the end of the presentation

Hashtag for this webinar: #DWwebinar

Other resources: www.mobilehydraulictips.com

www.pneumatictips.com

Before We Start

Paul Heney Design World

Moderator

Haubold vom Berg MTS Systems,

Sensor Division

Presenters

Dr. Christian Bauer Pall Corporation

Joel Johnson Simrit Division,

Freudenberg-NOK

Filtration Solutions for Off-highway Vehicle On-board Hydraulic Systems

Filtration Solutions for Off-highway Vehicle

On-board Hydraulic Systems

Presented by:

Christian M. Bauer, Ph.D.

Pall Corporation

Scientific and Laboratory Services Department (SLS)

Port Washington, New York

WTWH Webinar for Mobile Hydraulic Design, October 13th 2011

Contents

• Application description

• Contamination control

• Filtration technology for hydraulic fluid power applications

• Summary

• Multiple hydraulic subsystems o e.g. boom, arm, bucket, dump, level, swing

• High duty cycles

• High actuating pressure

• Critical components o Hydraulic cylinders

o Directional valves

o Gear/piston pumps

• High contamination environment

• Recirculatory system

• Return line filtration o Built-in bypass

o Change-out per maintenance schedule

Application Description

Contamination Control

• Contamination type: o Environmentally ingressed contamination:

• Dust and dirt from the environment

o Internally generated contamination:

• Wear debris from normal or abnormal wear of system components (pumps, bearings, valves, seals, etc.)

• Fluid degradation products (e.g. precipitated additives due to water ingression)

• Contamination effect: o Accelerated wear of system components, e.g.

• Control valves (stiction) – hydraulic systems

• Bearings (fatigue wear) – lubrication systems

• Gears (fatigue wear) – lubrication systems

• Pumps (abrasive wear) – hydraulic and lubrication systems

Photomicrograph of typical

contamination, 100X magnification

Dynamic Fluid Film

Thickness (µm)

LOAD

Abrasive Wear Effects

• Dimensional changes

• Leakage

• Lower pump efficiency

• Generated wear = more wear

Typical components subjected to Abrasive wear

• All hydraulic components (pumps, motors, spool

valves and cylinders)

• Gears

Dynamic Clearances and Abrasive Wear

To minimize wear and maximize component service life, clearance size

particles must be removed from the system.

Component Improvement

Pump motor 4 to 10x increase in pump and motor life

Hydrostatic transmission 4 to 10x increase in hydrostatic transmission (HST) life

Valve 5 to 300x increase in valve life

Valve spool Elimination of valve stiction

Roller bearing 50x extension of roller bearing fatigue life

Journal bearing 10x extension of journal bearing life

Fluid Extension of fluid service life and reduction of disposal costs through reduced contamination caused fluid degradation

Impact of Wear Control on Component Life

Servo valves 16/14/11 15/13/11 14/12/10

Proportional valves 17/15/12 16/14/12 15/13/11

Variable volume pumps 17/16/13 17/15/12 16/14/11

Fixed piston pumps 18/16/14 17/16/13 17/15/12

Pressure/flow control valves 19/17/14 18/16/14 17/16/13

Gear pumps 19/17/14 18/16/14 18/16/14

• Cleanliness recommendations* are based on: o System operating pressure and duty cycle

o Operating environment

o Component sensitivity and life expectancy

o Economic liability and cost of downtime

o Safety environment * Based on bottle sampling; cleanliness recommendations based on on-

line particle monitoring would be significantly lower. On-line monitoring

is strongly recommended for today’s operating system conditions.

System <140 bar 140-210 bar >210 bar Components (<2000 psi) (2000-3000 psi) (>3000 psi)

Industry Fluid Cleanliness Recommendations

Impact of Filtration on Abrasive Wear in Hydraulic Pumps

• Pump parameters

measured: o Piston to cylinder bore

o Universal link-pin clearance

o Pressure control pilot valve

clearance

o Pressure control

o piston diameter

o Pump flow

This test on 3,000 psi (207 bar) piston pumps clearly shows the wear-reducing benefit of

filtration. The report concludes that the dominant wear mechanism causing pump performance

degradation was hard particle abrasive wear between sliding surfaces.

Presented at SAE A6 Meeting – J. Ohlson, NADC

This study illustrates how valve silting/stiction from

particle build-up between moving surfaces increases

valve shifting force. Note how the highest force is

required when the valve is challenged by particles in the

dynamic clearance size range (~ 10 µm). Reference: Oklahoma State University

Valve Shifting Force vs. Contamination in Fluid

• Conditions of Directional Valve o Flow: ~ 15 gpm (56.8 L/min)

o Pressure: 3,000 psi (207 bar)

o Valve Radial Clearance: 8 µm

• Valve held stationary and under

pressure before shifting force

was measured

Benefits of High-Performance Filtration

• Inadequate filtration o System stabilizes at high contamination

level

o High metallic content in contaminant

• Replacement with high performance filtration o Rapid reduction of contamination in

system

o Significant reduction of metallic content

• Re-installation of inadequate filtration o Re-starts “chain reaction of wear”

o Rapid rise of contamination level and metallic content

In-to-out flow path Benefit: Reduces the chance of

cross contamination during filter

element change

Upstream cushion layer Benefit: Reliable, consistent

performance

High performance

filtration medium Benefit: Improved

performance over the service

life of the filter element, more

consistent fluid cleanliness

Up and downstream mesh

layers Benefit: Extended filter element

service life for lower operating

costs

Laid-over pleat shape Benefit: Smaller filter element

for an application; improved

resistance to cyclic and surge

flows and cold starts

Coreless/Cageless design Benefit: Lighter, environmentally friendly

element; reduced disposal costs; easy filter

element change-out

Outer helical

wrap Benefit: Reliable consistent

performance and resistance

to severe operating conditions

Anti-static design Benefit: No damage to filter element

or housing or other system

components from electrostatic

discharge; minimizes fluid

degradation

High Performance Filter Element Construction

Fiber size and fiber density govern the filter medium’s pore size and porosity

Benefits of smaller fiber diameter:

• Higher dirt capacity

• Lower pressure drop

• Longer service life

Benefits of inert inorganic fibers:

• Wide chemical compatibility

• No swelling

• No shelf life limitations

Cellulose Polymeric Glass fiber

15 to 25 μm 10 to 15 μm 1 to 5 μm

Filtration Medium - Importance of Fiber Diameter

Tapered Pore Design Uniform Pore Design

• Coarser upstream surface acts as a

pre-filter, capturing larger particles,

allowing finer downstream pores to

capture critical clearance-sized particles

• Reduces operating costs by combining

maximum particle retention with extended

service life

• Limits the effective use of the available

void volume to capture particles

• Increases operating costs by reducing the

total number of particles captured and

hence filter service life

Tapered Pore vs. Uniform Pore Structure

Laid-over pleat

filter element

Traditional

Fan pleated

filter element

Core Filter

Medium Mesh

Layer Filter

Medium

Mesh

Layer Mesh

Layer Mesh

Layer

Unused

volume

Laid-over Pleat Shape vs. Fan Pleat Shape

Field Cleanliness Levels Achieved with High-Performance Filtration

ISO 4406 Cleanliness Target Achieved ISO 4406

Cleanliness Level

Hydraulic systems truck 1

• Brake

• Hoist

• Torque converter

• Steering

-/18/15

-/16/13

-/16/13

-/16/13

-/12/9

n/d

n/d

-/13/10

Hydraulic systems truck 2

• Brake

• Hoist, Torque converter

• Steering

-/18/15

-/16/13

-/16/13

-/13/9

n/d

-/14/12

• The high level of cleanliness achieved protects critical system components against excessive wear and, potentially, premature failure

o Low cost of ownership to end user due to increased uptime

o Fewer OEM warranty claims

Summary

• On-board hydraulic systems on off-highway mobile equipment are

characterized by o High duty cycles and high loads

o Tight clearances and tolerances of critical system components

• Hydraulic cylinders

• Directional and proportional valves

• Load sensing pumps and motors,

o High contamination environment

• Maintaining high levels of fluid cleanliness critical to reliable operation o Requires high efficiency, stress-resistant filtration technology

• Consistent performance over the entire maintenance period

o Critical system components are protected against excessive wear

• Low cost of ownership to end user due to increased uptime

• Fewer OEM warranty claims

Best practice to automate a mobile hydraulic

machine to increase safety, efficiency and control

using in-cylinder position sensors.

Intelligent Hydraulic Cylinders to improve Safety, Efficiency and Control

Command

Intelligent Hydraulic Cylinders to improve Safety, Efficiency and Control

Feedback

Intelligent Hydraulic Cylinders to improve Safety, Efficiency and Control

Magnetostrictive Sensor

Magnet

Electronic

Barrel Rod / Shaft

Intelligent Hydraulic Cylinders to improve Safety, Efficiency and Control

- Automation of work motion

- Programmable work limits

- Electro-hydraulic end of stroke damping

- Track tension

Intelligent Hydraulic Cylinders to improve Safety, Efficiency and Control

- Front loader, parallel guidance

- Cabin suspension, auto leveling

- Hitch control - Suspension - Steering, steer-

by-wire, autoguidance

Intelligent Hydraulic Cylinders to improve Safety, Efficiency and Control

Important design features

- in-cylinder design - Non-contact technology - Sensor/Magnet system - IP 67 sensor - IP 69K connector system - EMI protection 200 V/m - Withstand more then 100oC

Best Practices For Mobile Hydraulic Sealing

How OEM Design Engineers Incorporate Sealing Into Hydraulic

Systems On Mobile (Off-road) Equipment

Joel Johnson, Global Vice President of Technology

Simrit, Division of Freudenberg-NOK Sealing Technologies

Hydraulic Remote Controls

Drive Motors

Hydraulic Pumps

Cylinders

Hose & Fittings

Control Valves

Filters

Hydrostatic Drive Pumps

Hydraulic Systems and Sealing – A Very Broad Topic

• There are many items

in a hydraulic system

that require sealing

• We will focus on:

o Pumps

o Motors

o Cylinders

• First question - does it reciprocate or rotate?

• Different sealing solutions for each

o An engine turns a pump which converts mechanical energy into fluid energy

o The pump

• Turns a hydraulic motor which turns a shaft (i.e. an axle)

• Energizes a cylinder that lifts – reciprocating motion

Hydraulic Systems and Sealing – Relative Motion

• What is the pressure range?

o Low pressure – usually less than 50 psi

o Medium pressure – 50 to 500 psi

o High pressure– 500 to 6000+ psi

Low

Medium

High

Typical Pressure Variation

Housing

Shaft Contact width

Oil

a b Contact angles

Radial seals must create a pumping action!

Oilside outside

Segment

streams

Overall stream

Structure

distorted in

circumference

Radial load distribution and

shearing stress characteristic

in the area of contact

Sliding motion

Rotating Application – Elastomer Lip Design

Special Issues with Pressure Seal Applications

Seal must resist lip deformation from internal fluid pressure to minimize friction, wear, and heat.

Seal material should have high mechanical strength.

Special retention and support mechanisms are usually required to resist seal back-out and extrusion.

System eccentricities need to be more carefully considered than with non-pressure seals.

Surface finish parameters may need to change depending upon pressure

Pressure deformation causes increased seal

contact with the shaft, thus increases friction,

heat generation, and wear.

How Pressure Effects Seal Designs

14.5 psi (1 bar)

Deformation

Typical Low Pressure Seal (BABSL) With 50 PSI Limit

60

43.5 psi (3 bar)

Deformation

Typical Low Pressure Seal (BABSL) With 50 PSI Limit

101 psi (7 bar)

Deformation

Typical Low Pressure Seal (BABSL) With 50 PSI Limit

145 psi (10 bar)

Deformation

Typical Low Pressure Seal (BABSL) With 50 PSI Limit

Unique Designs for Specific PV Ranges

Choose a seal design to match the pressure / velocity curve (PV)

0 1 2 3 4 5 6

SPEED (RPM X 1000)

0

200

400

600

800

1000

1200

1400

1600

PR

ES

SU

RE

(P

SI)

High Pressure

Designs

Medium Pressure

Designs

Standard Oil

Seal

SEAL LIFE

Application of Seals in Hydraulic Cylinders

Piston seal

Wear ring

Contamination seal

Rod seal

Buffer seal

Wiper seal Prevention of outside dust invasion

Prevention of external oil leakage

Reduction of high pressure and high temperature

Prevention of internal oil leakage

Restraint of

eccentricity

Removal of foreign object in oil

Piston

End

Rod

End

• High Temp - handle continuous 120 degree Celsius upper temp limit

• High Pressure - capable of 6000 psi (42 MPa) @ 0.5mm diametrical extrusion gap

• Cold Temp - TR10 of -30º C; - 40º C actual application capability

• Fluid Compatibility - compatible with standard hydraulic and biodegradable fluids

• Water and chemical resistance - hydrolisis and glycolosis resistant

• Retrofit – in North American, DIN, and JIS standard grooves

Hydraulic Cylinder Market Requests

Excessive Temperature

• .

Problem: excessive temperature levels; oil sump temperatures

can be much lower than those by the seal; increased

temperatures due to high friction between seal and running

surface.

characteristics: hardening of material; loss of interference;

often very shiny brown color

Problem: influence of water or glycol at temperatures

over 40 °C break the chemical bonds of the material.

Water can separate from some bio-oils at elevated

temperatures.

characteristics: crumbling material; often matte brown

color can be found either in the oil or filter.

Hydrolysis / Glycolysis

Hydraulic Cylinder Reported Field Problems

• If conditions are good (no problems with contamination, oil, rod surface, etc.), the packing usually fails due to loss of remaining interference (wear and material related).

• Bench testing can be correlated to actual field test results. Bench test hours are usually less than actual field hours due to accelerated test conditions.

• Our bench testing has shown that increasing or decreasing the system temperature can increase or decrease the system life by 5 to 20 times.

0

10

20

30

40

50

60

70

80

90

100

1 10 100 1000 10000 100000

Tim e（ｈ）

Remain

g Interenc

e（％）

0

10

20

30

40

50

60

70

80

90

100

1 10 100 1000 10000 100000Tim e（ｈ）

Remain

g Interfe

renc

e（％）

Remaining Interference（Rod Seal）

5~20 times effect on life with temp change

Bench test Field samples

High temp

Low temp Low temp

High temp

Temperature Effect on Long-Term Life

U641 “all urethane” solution

o Best cost / benefit commercially available

solution on the market

o Seal design handles pressure needs

o Years of lab and field proven results

o Retrofits in existing grooves

o Retrofits in existing tools

o Extremely hydrolysis and glycolysis resistant

o Good low temperature capability (-21 C)

110 degree C

Solution

120 degree C

Solution

Ge

ne

ral D

escrip

tion

Detailed Testing Data

Available

Potential 5X Life

Increase

UH05 / G928 high temp systems

o Unique 120 deg C capable urethane buffer plus proprietary HNBR rod seal

o Sealing system handles pressure needs

o Lab tested with exceptional results

o Current production for select cylinders

o Retrofits in existing grooves

o G928 is extremely water and glycol resistant; UH05 has good resistance

o Best low temperature solution (-40 C)

All Urethane sealing system

U641 U641

UH05 G928

U801

U801

IUY sealing system

All Urethane sealing system

U641 U641

UH05 G928

U801

U801

IUY sealing system

Simrit’s Innovative Rod Sealing Solutions

Piston Seal Standardization

Numerous designs prevent standardization

Many different piston seal designs are necessary

No clear optimization based on operating conditions

Different piston designs

Standardization of housing and seal possible

Substitution - PTFE to Polyurethane or Polyamide

Substitution - multiple component seal to 2-piece

Up to 30% cost saving for cylinder / seal

Piston design to ISO 7425-1

2-piece using PA

Polyurethane PTFE Multiple component seals

Polyurethane PTFE

currently

Target

Goal: only use 2 piece piston seals and minimize the need for more expensive PTFE seals

Highest sealing capability

Higher friction than PTFE

Most optimal pricing level

Simple assembly

Up to 40 MPa with correct extrusion gap

Lowest sealing capability

Lowest friction

Rougher surf finishes possible

Capable of running over ports etc.

Used for extreme operating conditions (up to

80 MPa)

Mid sealing capability

Lower to mid friction

For extreme low or high stroke speeds

(<0,05 m/s ... > 0,8 m/s)

For high temperatures (up to 200°C)

Up to 40 Mpa with the correct extrusion gap

Polyurethane

PA 6.6 GF

Fiber re-enforced Bronze filled

PTFE

Housing for piston seals

Simrit offers polyurethane,

polyamide, and PTFE

solutions that can fit into

the ISO 7425-1 piston

housing groove standards

while matching the cost /

performance objectives of

the cylinder.

Standard Sealing Solutions in ISO Standard Sizes

Standard Designs Matched With Performance Expectations

30MPa

50MPa

10MPa

Increasing Sealing Capability

Increasing Friction

segment

Construction

equipment

Excavator

Wheel loader

Crane

Industrial

equipment

Forklif t

Steel mill

Injection machine

Electric

product

Low

High

Pre

ss

ure

re

sis

tan

ce

98 Shore A

Extrusion

Resistant

Urethane

Simko 300

Precision

Molded

PA

HDP330

High

Strength

Bronze

Filled

PTFE

High

Strength

Bronze

Filled PTFE

OMK-MR

• The piston seal has

slight leakage

• Leakage is internal

to the system

• Choose seal design

based on friction

verses sealing

capacity

Questions? Design World Paul Heney Email: pheney@wtwhmedia.com Phone: 440.234.4531 ext. 104 Twitter: @DW_Editor

MTS Systems, Sensor Division Haubold “Hub” vom Berg Email: hub.vomBerg@mts.com Phone: 919.677.2370

Simrit Division, Freudenberg-NOK Joel Johnson Email: Joel.Johnson@simrit.us Phone: 847.421.1621 ext. 81222

Pall Corporation Dr. Christian Bauer Email: Christian_Bauer@pall.com Phone: 516.801.9139

Thank You

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