Electrostatic Discharge in Hydraulic and Lubrication Systems

Transcription

1 HYDRAULIC AND LUBE FILTRATION Electrostatic Discharge in Hydraulic and Lubrication Systems May 23, 2018 Ralf Haller Industrial Training / Northeast 1

2 Remember, ESD is only one potential source of varnish formation Varnish formation is the buildup of insoluble soft contaminant oxidation byproducts. It is promoted by a combination of - Water - Heat Gets into tank through breather Is promoted by high humidity Friction Compression, dieseling ESD discharge Forms free radicals High acidity Loss of lubricity Problems in load zones Reduces surface tension of oil Promotes corrosion (with O 2 ) Pulls additives from oil 2 - Oxygen Agitated tank with insufficient settling time Undersized tank Additive decomposition Degradation of base stock Formation of oxidation byproducts Formation of metal oxides Pressure induced thermal degradation

3 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 3

4 Source: Examples of electrostatic charging and discharging 4

5 Electrostatic Discharge a Very Serious Subject Source: 5

6 Cause: low conductivity oils Requirement for consistently high quality oil Trend towards group II and III base oils [ps/m] C 50 C 1500 Group Classification based On API (American Petroleum Institute Group I Group II Group III Increased environmental awareness, more stringent regulations Trend towards biodegradable zinc and ash-free oils 6 Problem: These oils are mostly of low conductivity high electrostatic charging!

7 Unsaturated Hydrocarbons By means of hydrocracking And dewaxing processes Base oils with saturates Over 90% are produced 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 7

8 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. 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. 8

9 Principles Charging of solids Double layer 1 2 a < 10 nm a < 10 nm Two materials with different electron work functions Separation distance < 0.01 µm (no friction necessary!) Electron migration produces double layer 9

10 Principles Charging of solids 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)

11 Donor Acceptor Donor Acceptor Charging of solids - Details 1) Two materials brought together: double layer formation Charge: Q[ C] C[ F] U[ V] Charge = Capacitance x Voltage 2) Separation = increasing distance d C C C U 0 (higher distance lower capacitance) A (capacitance of capacitor) r d (lower capacitance higher voltage) Voltage rises from mv to kv 11 Ɛ 0 = absolute dielectric constant of a vacuum (8.854x10-12 F/m) Ɛ r = dielectric constant of liquid (approximately 2 for oil)

12 Principles Charging of fluids Wall + + Fluid Diffuse charge layer In fluids ions are the charge carriers Flow of the fluid charge separation along the shearing area Prerequisite: low conductivity of fluid 12

13 Summary - Main contributory factors Conductivity: Low conductivity Filter material: Critical filter material Temperature: Low temperature Hydraulic load: High hydraulic load high charging high charging high charging high charging Contamination: Generalized statement not possible 13

14 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. 14

15 Possible results of ESD Possible filter element conditions: Burned holes in filter media Holes in the filter material (> 200 µm) put an end to fine filtration Damage to support structure Brittle support layer reduces stability 15 Possible consequences to the oil: Accelerated oil ageing Free radicals attack and break down the antioxidants Varnish formation Varnish contaminates the filter, creates deposits in the tank or abrades, (wears) component surfaces

16 Possible consequences of ESD Consequences in hydraulic/lube systems: Explosion in tank Charged 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 16

17 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 17 Increased use of Servo Control Increased demand on fluid cleanliness Move to high performance fluids (generally Group II base stock)

18 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 18

19 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 19

20 What to do when you suspect ESD in your system? Do you have any of the conditions below in combination? - Fluid loading > gpm / in 2 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 20

21 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 21

22 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 After remedial action Voltage measured at -356V With single housing in operation SFREE elements solved The problem 22 Spark discharges

23 Offshore crane Conductivity: 68 ps/m Initial Situation Discharges in tank Voltage peaks: 17,000 V Explosion in tank Burned breather filter No discharges Voltage: 2-3 V Source: Lecture "Turbine Oil Degradation and Varnish Formation" Speaker: Akira Sasaki, Ph. D., Maintek Consultant, STLE member during HYDAC Symposium, January 21-22, 2009 After remedial action kv 5.00 V

24 Power plant Lubrication system of steam turbine Conductivity: 1 ps/m Initial Situation Remedial Action Gas reservoir Lubrication of compressor Conductivity: 2 ps/m Initial Situation Remedial Action Spark discharges Burned holes, Voltage: 2,280 V - No burn marks - Voltage: 60 V 24

25 4D Sales Process 1. Discover 2. Diagnose 3. Design 4. Deliver 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 25

26 4D Sales Process 1. Discover 2. Diagnose 3. Design 4. Deliver 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 26

27 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 27

28 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%. 28

29 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 29

30 30 Exercise: Who feels the pain?

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