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Electrostatic Discharge

in Hydraulic and

Lubrication Systems

May 23, 2018

Ralf Haller

Industrial Training / Northeast

HYDRAULIC AND LUBE FILTRATION

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Varnish formation is the buildup of insoluble soft contaminant oxidation

byproducts. It is promoted by a combination of

- Water

- Heat

- Oxygen

Remember, ESD is only one potential

source of varnish formation

• Friction• Compression, dieseling• ESD discharge• Forms free radicals

• Additive decomposition• Degradation of base stock• Formation of oxidation byproducts• Formation of metal oxides• Pressure induced thermal

degradation

• Agitated tank with insufficientsettling time

• Undersized tank

• High acidity• Loss of lubricity Problems in load

zones• Reduces surface tension of oil• Promotes corrosion (with O2)• Pulls additives from oil

• Gets into tank through breather• Is promoted by high humidity

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Contents

Cause and Theory (a brief review)

- Principles of electrostatic charging and discharging

- Main contributory factors

- Signs of electrostatic discharge

- Possible consequences of electrostatic discharges

Applications with high potential for ESD

What to do when you suspect ESD in your system?

Real World Examples with solution

Value Hypothesis

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Examples of electrostatic charging and discharging

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Electrostatic Discharge –

a Very Serious Subject

http://www.youtube.com/watch?v=fT3X93w5mwQ&feature=relatedSource:

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Requirement for consistently high quality oil

Trend towards group II and III base oils

Increased environmental awareness, more stringent

regulations

Trend towards biodegradable zinc and ash-free oils

0

500

1000

1500

2000

[pS/m]

Group I Group II Group III

23°C 50°C

Cause: low conductivity oils

Problem: These oils are mostly of low conductivity

high electrostatic charging!

Group Classification based On API (American PetroleumInstitute

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Unsaturated Hydrocarbons

Typically the less refined the base oil is, the higher its conductivity

Zinc used to be a common multipurpose additive in the form of Dithiophosphate, a metal organic compound which increased conductivity and today is regarded as having dangerous health implications and for that reason is now largely avoided

By means of hydrocrackingAnd dewaxing processesBase oils with saturatesOver 90% are produced

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Note:Hydro treatment processes were increasingly used during the 90s. Hydro treatment processes are more efficient at removing contaminants such as Sulphur and Nitrogen than distillation based and solvent based processes.

Hydro treatment also causes unsaturated hydrocarbons to saturate and in particular this means saturating and cracking of aromatic hydrocarbons such as Benzene.

• Turbine Manufacturers started to specify the new high performance Lube oils, expecting increased life for their turbines.

• What happened instead was that they increasingly experienced problems with varnish

• Where they retrofitted older turbines they ran into the same problem often with turbines that had run many years trouble-free.

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Principles – Charging of solids

Two materials with different electron

work functions

Separation distance < 0.01 µm (no friction necessary!)

Electron migration produces double layer

1 2

a < 10 nma < 10 nm

Double layer

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Principles – Charging of solids

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Separation causes electrostatic charging of the two

materials

The faster the separation, the higher the charging

Sufficiently high voltages = dielectric breakdown

Electrostatic Discharge (ESD) (Arcing)

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Accepto

r

Charging of solids - Details

1) Two materials brought together:

double layer formation

Charge:

2) Separation = increasing distance

Voltage rises from mV to kV

Donor

][][][ VUFCCQ

voltage) higher ecapacitanc (lower U C

capacitor) of ce(capacitan d

AC

e)capacitanc lower distance (higher C d

r

0

Accepto

r

Donor

Charge = Capacitance x Voltage

•Ɛ0 = absolute dielectric constant of a vacuum (8.854x10-12 F/m)

•Ɛr = dielectric constant of liquid (approximately 2 for oil)

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Principles – Charging of fluids

In fluids ions are the charge carriers

Flow of the fluid

charge separation along the shearing area

Prerequisite: low conductivity of fluid

+++++++++

Wall Fluid

Diffuse charge layer

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Summary - Main contributory factors

Conductivity:Low conductivity high charging

Filter material:Critical filter material high charging

Temperature:Low temperature high charging

Hydraulic load:High hydraulic load high charging

Contamination:

Generalized statement not possible

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Signs of Electrostatic Discharge

• Electrostatic discharge may present

itself as a clicking sound as the charge

builds in the system locally.

SIGNS OF ESD:

ESD changes the fluid structure

(damaging of additives) which can

deposit a varnish on system components

SIGNS OF ESD:

ESD can also break down the additives in the

hydraulic fluid and create a sludge that will

interfere with the operation of system components

and the filter itself.

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Possible results of ESD

Possible filter element conditions:

Burned holes in filter mediaHoles in the filter material (> 200 µm) put an end to fine filtration

Damage to support structureBrittle support layer reduces stability

Possible consequences to the oil:

Accelerated oil ageingFree radicals attack and break down the antioxidants

Varnish formationVarnish contaminates the filter, creates deposits in the tank or abrades, (wears)component surfaces

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Possible consequences of ESD

Consequences in hydraulic/lube

systems:

Explosion in tankCharged oil can cause discharges in the

tank

Damage to electronic components

(RF transmissions)

Damage to heat exchanger

components as the down stream

charges accumulate and finally

discharge through thin cooler

surfaces

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Typical Applications where we may see ESD

Plastic Injection Molding

80% of product defects stem from hydraulic contamination problems as the root

cause !

General conditions prevalent in Plastics Injection Molding:

- Temperature Extremes

- High Pressures

- High Cyclical Hydraulic Loads

Trends

- Toward increased clamping and discharge pressures

- Smaller Reservoirs

- Extended operating schedules

- Higher Cycle Rates

Increased Demands

- Moving large masses with higher speed and precision (clamping units)

- Perfect Control and reproducibility (injection process)

- on productivity

- on energy efficiency

- on reliability

Increased use of Servo Control

Increased demand on fluid cleanliness

Move to high performance fluids (generally Group II base stock)

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Other typical Applications where we may see ESD

Mobile Applications

Trends

- Move to better filtration as components get more sensitive

- Manufacturers have experienced tremendous cost pressures

- Increase in power density

- Tier IV pressure on manufacturers -> results in more

equipment under the hood

Consequences of the above

- Smaller space envelope for filters – increased hydraulic load

- Smaller tanks, less oil – less time for cooling and de-aeration

- Use of plastics for tanks

- Increase in pressure

- Temperatures are higher, sometimes overheating

Other conditions

- Cold Starts are common

The above trends and conditions favour the use of higher

performance Group II and Group III oils

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Shift from Group I to Group II and III base stocks

! There has been a shift in the use of oil base stocks away from group I

This shift still continues today and low oil prices have accelerated the trend

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What to do when you suspect ESD in your

system?

Do you have any of the conditions below in combination?

- Fluid loading > 0.017 gpm / in2 of the filter media

- Fluid conductivity < 500 pS / m

- Compact system with high flow rates

- Pulsating flow with high peak rates

- Ashless, zinc free fluids

- Low temperatures during operation

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What to do when you suspect ESD in your

system?

Bring your problem to the attention of the Product Management team

- Our distributors should work with us to analyze the system for

electrostatic charge under real life conditions

Our distributors may recommend Fluid Samples for Analysis

- Fluid samples can be analyzed for conductivity

Be careful with some solutions that are offered by our competitors

- Making internal filter parts conductive is dealing with the symptoms not

with the underlying problems

- Only charge dampening at the media level works

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Power plant

Initial Observations

Transfer Valve was kept open – both housings active

Reported ticking noise when operating with one housing

Conductivity measured at 31 pS/m at 130 C

Initial Situation

Spark discharges

After remedial action

Voltage measuredat -356V

With single housingin operation

SFREE elements solvedThe problem

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Offshore crane

Conductivity: 68 pS/m

• No discharges

• Voltage: 2-3 V

• Discharges in tank

• Voltage peaks: 17,000 V

• Explosion in tank

• Burned breather filter

5.00 kV5.00 V

After remedial actionInitial Situation

Lecture "Turbine Oil Degradation and Varnish Formation"

Speaker: Akira Sasaki, Ph. D., Maintek Consultant, STLE member

during HYDAC Symposium, January 21-22, 2009

Source:

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Power plant

Lubrication system of steam turbine

Conductivity: 1 pS/m

Initial Situation

Spark discharges

Remedial Action

Gas reservoir

Lubrication of compressor

Conductivity: 2 pS/m

Initial Situation

Burned holes,

Voltage: 2,280 V

Remedial

Action

- No burn marks

- Voltage: 60 V

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Discovery Phase - Value Hypothesis

First Step is to determine if your customer experiences ESD

If he does you have to create a value hypothesis

Diagnostic Phase

You have to calculate the cost for your customer if he has ESD problems and

present him with the magnitude of the problem in financial terms

- Aging the oil

- Destroying the elements

- Cost of remediation of the varnish issues

- Cost of hydraulic components

- Cost of downtime (loss of production) and unscheduled maintenance

- Cost of bad product quality

4D Sales Process1. Discover2. Diagnose3. Design4. Deliver

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Value Hypothesis - continued - Design Phase

Go over this with your customer

Explain that you have a solution that will do away with all those costs, at

relatively minor cost.

Delivery Phase

Present SFREE and be mindful of your audience.

- Remember, it won’t help you much to pitch the presentation we have just

seen to the Purchasing Manager

- It is important that you understand who feels what pain at your customer so

you can demonstrate your value more effectively

Estimate ROI to reinforce your arguments

4D Sales Process1. Discover2. Diagnose3. Design4. Deliver

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Exercise: Estimate cost of ESD at customer

Your customer is a Plastics Injection Company (enduser)

- They operate 20 Plastics Injection machines 10 Husky, 10 Milacron

- At least 10 of these machines have Return filtration, 5 have only a kidney loop, the

rest have both

- The Purchasing Manager told you they have no problems, but when you talked to the

Production Manager you found out that for the last 2 years they have had a lot of

varnish problems and they “lose” a servo valve every other month right now. Used to

be once in 6 months.

- He is having a lot of pressure from management due to the fact that his maintenance

costs have skyrocketed while machine availability is at an all-time low.

- Eventually you manage to talk to other decision makers and they all contribute

additional information to the problem.

- Some 3 years ago Purchasing apparently won the argument to cut cost by buying

cheap Chinese cross-over elements

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Exercise: Estimate cost of ESD at customer - continued

Determine what the problem is. You suspect ESD

- What do you do to confirm?

Create a Value Hypothesis

- Based on what we know, let’s consider the magnitude of your customers problems

with the help of some additional educated guesses

- Let’s put some numbers to this.

Let’s assume the oil need to be changed after 3 years instead of 6

Elements get changed twice a year instead of once. Chinese elements cost 60% of a HYDAC

standard element.

Cost of varnish remediation unit.

Cost of servo valves. Also assume some other hydraulic components

Cost downtime. Went from 5% to 10% loss of production. Current total revenue $25M, cost of

Product currently $10M

Product quality. Defects in the field rose from 0.01% to 0.04%.

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Exercise: Estimate cost of ESD at customer

Now that we know the total value and its constituent parts let’s look who

feels what pain at the customer

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Exercise: Who feels the pain?

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