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Water Contamination in Oil Introduction Do you dare let this happen to your components? Water is widely considered as the second most destructive contamination to a lube system, after particulate contamination. This article will focus on how water exists in oil, the effects of water on oil and lube systems and measurement of water amount in oil, as well as setting alarm targets for water levels in oil. Where does water come from? Water in lubrication systems can originate from the environment, such as rain or moisture in the air. Leakage, damaged gasket on reservoir covers, underperforming air breathers, or a damaged wiper on a hydraulic cylinder are also possible sources. Condensation of air in oil reservoirs due to temperature difference between day and night will turn any moisture in the air into water droplets, mixing with the oil. A damaged water-based cooling system in a steam application is another potential water source. How does water exist in oil? Water in oil can exist in three stages: dissolved, emulsified and free. Below saturation level, the molecules of water are dispersed alongside oil molecules, resulting in water in the oil that is not visible. This is known as dissolved water, the least dangerous water state to a lube system. When the amount of dissolved water exceeds the saturation point, the oil is no longer able to absorb more water molecules, resulting in emulsified water. This is characterised by a hazy or cloudy appearance of the oil. Further increments of water content in oil will result in separate levels between oil and water forming. This state is known as free water. Due to its higher density, the water forms the lower layer, settling at the bottom of the sump, with the oil floating on top. However, emulsified water will also be present in an intermediate phase, continuing to circulate in the lube system.
Transcript

Water Contamination in Oil

Introduction

Do you dare let this happen to your components?

Water is widely considered as the second most destructive contamination to a lube system, after

particulate contamination. This article will focus on how water exists in oil, the effects of water on oil

and lube systems and measurement of water amount in oil, as well as setting alarm targets for water

levels in oil.

Where does water come from?

Water in lubrication systems can originate from the environment, such as rain or moisture in the air.

Leakage, damaged gasket on reservoir covers, underperforming air breathers, or a damaged wiper

on a hydraulic cylinder are also possible sources. Condensation of air in oil reservoirs due to

temperature difference between day and night will turn any moisture in the air into water droplets,

mixing with the oil. A damaged water-based cooling system in a steam application is another

potential water source.

How does water exist in oil?

Water in oil can exist in three stages: dissolved, emulsified and free. Below saturation level, the

molecules of water are dispersed alongside oil molecules, resulting in water in the oil that is not

visible. This is known as dissolved water, the least dangerous water state to a lube system.

When the amount of dissolved water exceeds the saturation point, the oil is no longer able to absorb

more water molecules, resulting in emulsified water. This is characterised by a hazy or cloudy

appearance of the oil.

Further increments of water content in oil will result in separate levels between oil and water

forming. This state is known as free water. Due to its higher density, the water forms the lower layer,

settling at the bottom of the sump, with the oil floating on top. However, emulsified water will also

be present in an intermediate phase, continuing to circulate in the lube system.

Figure 1 shows the visible difference between dissolved, emulsified and free water within oil

samples.

The saturation level of the oil is important, as it determines the amount of water that can be held

before an emulsion will develop. Saturation level depends on base oil type, additive package,

temperature and pressure. A highly refined mineral oil with minimum additive level has a saturation

level of about 100 parts per million (ppm) at 70°F, whereas ester-based hydraulic fluids can have

saturation levels of more than 3000 ppm at 70°F.

Figure 2 shows the saturation level curve of a typical turbine lube versus temperature.

Dissolved Water

Emulsified Water

Free Water

Figure 1: Dissolved, emulsified and free water

Figure 2: Saturation curve for a typical turbine lube oil (graph from Noria Corp)

Effect on Oil

Physical

• Higher viscosity

• Reduced load carrying ability

Chemical

• Hydrolysis – formation of acids, sludge

and varnish

• Reduced dielectric strength

(transformer application)

• Aeration – foam formation and air

entrainment

• Additive depletion

Effect on machinery

• Corrosion on metal surfaces

• Loss of lubrication film strength –

Increased wear

• Cavitation

• Filter plugging

What type of damage can water do?

The effect of water in oil is twofold, destroying both the beneficial physical and chemical properties

and characteristics of the oil. This can lead to machine component damage.

Based on a study by Cantley in 1977, it is estimated that bearing life can be extended by a factor of

five if the oil contains only 25 ppm water compared to 400 ppm, close to the oil saturation level at a

test temperature of 150°F.

Figure 3 shows the adaptation of Cantley’s findings and the strong correlation between water

content and relative bearing life.

Figure 3: The relationship between Relative Bearing Life and Water Content in Oil

(graph from Noria Corp)

Figure 4 illustrates Relative Wear Rates for similar systems running with different amounts of water

in oil. It shows that component wear rate directly correlates with the water content in the oil.

How is water in oil measured?

Water in oil can be measured in 3 ways; on-site by sampling, in the laboratory and online in real

time.

1. On-site (offline application)

1.1 Crackle Test

The most expedient and economical way to determine water content in oil.

Two drops of oil are placed on a hot surface (130°C) and any bubbling or crackling is observed. The

size of bubbles may give an indication of the amount of water in the oil (Figure 5). However, due to

its course and unitless results, a crackle test is suitable only as a screening test.

Figure 4: Relative wear rate vs. test time (graph from Noria Corp)

Figure 5: Water in oil determination by the crackle test

1.2 Calcium Hydride Test

One of the most widely used methods on-site; this method uses a pressurised call containing the oil

sample and a chemical reagent (calcium hydride). Water in the oil reacts with the calcium hydride

and forms hydrogen gas. The cell is shaken vigorously to accelerate the reaction. A change of

pressure due to the hydrogen build up is detected by a pressure sensor and this is converted to a

water content figure, either in % or part per million.

The advantages of this method are a very fast turnaround (less than 4 minutes per test) and a low

cost per sample. The electronic water in oil test developed by Kittiwake (Figure 6) is able to detect

water content between 100 ppm to 25,000 ppm, with an accuracy of ± 0.1%. A variation, based on

the same principal, is the Kittiwake DIGI Water in Oil Test Kit (Figure 7) with a detection range of 200

ppm to 200,000 ppm.

Figure 6: Kittiwake Electronic Water in Oil

Figure 7: Kittiwake DIGI Water in Oil

2. Laboratory

2.1 Karl Fischer Method

One of the more accurate water tests, able to measure as low as 10 ppm of water in oil, but usually

only available at a full service laboratory. A disadvantage of the Karl Fischer water test is that it is

expensive and often time consuming when water concentrations are high.

2.2 Fourier Transform Infra-Red (FTIR)

FTIR is used as a rapid test for multiple parameters on an oil sample. Infra Red light is passed

through a sample of oil and the absorption at different wavelengths in the optical spectra is

measured and from this, the concentration of water can be determined. The technique also allows

Nitration, Oxidation, Soot Concentration, Phosphate Anti-Wear and Anti-Oxidant depletion amongst

other parameters. Traditionally a lab based test due to the sensitivity of the equipment, FTIR

devices, such as Kittiwake’s FTIR3 Oil Analyser, are now available for field use.

Figure 8: Water by Karl Fischer test method

Figure 9: Kittiwake’s FTIR3 Oil Analyser

3. On-line (Real Time Measurement)

3.1 Moisture Sensor

As the critically of water ingress increases, continuous monitoring of water in oil may be needed. On-

line Moisture Sensors can be installed on machines where continuous, 24/7 monitoring is required.

Kittiwake’s Moisture Sensors measure the Relative Humidity of oil (resulting from dissolved water

within the lubricant). Using a combination of a proven thin film capacitance sensor combined with a

“smart” algorithm, the device measures both the temperature and % Relative Humidity Value.

3.2 On-line Infra-Red Measurement

Another advanced online instrument to detect water in oil is WaterSCAN, developed by Kittiwake.

This measures the water content in parts per million within the oil by utilising absorption of infrared

light by the water in the oil. This method has the advantage of being able to measure the total water

content (dissolved, emulsified and free water). It can also measure soot content within the oil at the

same time data is logged within the device and alarms can be set for notification purposes. The data

can also be transferred directly to a PC or downloaded via a USB drive.

Figure 10: Kittiwake Moisture Sensors

Figure 11: Kittiwake WaterSCAN

How much is too much water in oil?

Setting an alarm level for water in oil is very important for machine reliability. Establishment of

levels, combined with testing at proper intervals, will allow the end user to act quickly if a sudden

increment of water is detected.

Best practice is to maintain water levels at or below half of the saturation level of the oil at its

operating temperature. For example, if the saturation level is 1000 ppm at 50°C (used °F previously,

now switched to °C), the caution level should be set at 500 ppm, with the critical level at 1000 ppm.

Table 1 shows the levels of dissolved, emulsified and free water in oil that will be expected for

different types of oils. It is important to know the oil base oil type, additive package, operating

temperature and pressure before establishing the alarm level.

Oil Dissolved (ppm) Emulsified (ppm) Free (ppm)

New hydraulic fluid 0-200 200-1000 >1000

Aged hydraulic fluid 0-600 600-5000 >5000

New R&O Oil 0-150 150-500 >500

Aged R&O Oil 0-500 500-1000 >1000

New crankcase oil 0-2000 2000-5000 >50000

Case Study

Water ingression in a plastic injection moulding machine.

Location: Shah Alam, Selangor, Malaysia.

Date: March 2007

Overview

The plant has about 20 plastic injection moulding machines, producing spare parts for automotive

manufacturers in Malaysia. Most of the machines are running 24 hours a day, 7 days a week to meet

client requirements.

Machine No. 5, an 800 Tonne injection moulding machine, uses hydraulic oil, ISO 46 grade. The

hydraulic system consists of a proportional valve, requiring ultra-clean oil.

One evening during machine operation, a copper tube inside the oil cooler was damaged, allowing

rapid water ingression into the lube oil system.

The machine operator only realised this when the oil (now milky in colour) spilled out of the oil

reservoir. The machine was then immediately shutdown.

Table 1: Level of dissolved, emulsified and free water for various type of oil

On top of oil reservoir Damaged oil cooler

The oil cooler was dismantled and confirmed as the source of ingested water. A total of 1600 litres (8

drums) of hydraulic oil was drained and the oil tank cleaned. Flushing removed the remaining

contamination from the system. A new oil cooler was installed and new oil was transferred into the

system.

Overall cost of this failure to the plant owner:

Item Details Cost (MYR)

1 Eight (8) drums of new hydraulic oil 46 grade at MYR 1,200.00

per drum.

8 x MYR 1,200.00 per drum

9,600.00

2 One (1) new oil cooler

1 x MYR 3,500.00 per unit

3,500.00

3 Manpower:

- Drain the contaminated oil

- Clean internal surfaces of the oil reservoir

- Assemble the new oil cooler

- Flush the system with flushing oil

4 persons x MYR 50.00 per hour per person x 16 hours

3,200.00

4 Other costs and accessories for flushing, rags, etc. 3,000.00

5 Loss of production due to unscheduled machine downtime for

two (2) days

Approximately MYR 20,000.00 per day x 2

40,000.00

TOTAL 58,300.00

Lessons learned:

1. Water contamination cost the company more than MYR 50,000.00.

2. Prior to this case, this company had not implemented Condition Based Monitoring for their

machines.

3. Routine oil analysis would detect copper metal in the oil, originating from corroded copper

tubing in the oil cooler, allowing early diagnosis of a problem. Increasing water levels would

corroborate the cooler issue.

4. Early detection of this problem allows a planned, scheduled downtime in order to replace

the faded oil cooler. This would have resulted in a cost to the company of only 10% of that

caused by the machine breakdown.

Conclusion

Water in oil should be maintained at a level as low as possible, due to its destructive nature. Routine

oil analysis should be performed, including water content testing to ensure acceptable levels are

maintained. This also allows the user to perform necessary remedial action when appropriate.

Prevention, however, is even better than cure. Ensuring that water ingression is minimised offers

greater oil lifespan, machine reliability and productivity.

* Azhar bin Abdullah – Field Engineer, Kittiwake Asia Pacific Sdn. Bhd. Azhar has worked in the field

of Oil Condition Monitoring for 8 years. He currently works as a field engineer for Kittiwake,

demonstrating to and training customers in the use of oil condition monitoring equipment and

techniques. He holds a BSc in Mechanical Engineering (Universiti Teknologi Malaysia) and is a

certified ICML MLA Level III Oil Analyst.

* Steve Dye is the business development manager for Parker Kittiwake, concentrating on promoting

high end products into the market, including FTIR analysers. He has worked in high technology

businesses for all of his career including Hewlett Packard and Lucent Technologies, covering roles

from development and product management through to sales and marketing director. He has been

involved in the field of Condition monitoring for the past 3 years. Steve holds a Bachelors degree in

Communications Engineering and a PhD in Optoelectronics. He is also a ICML Level I certified

Lubrication Analyst.

* Jack Poley – Technical Director, Kittiwake Americas. Jack has over 50 years in Oil Analysis and is

recognised as a world expert in both laboratory and field measurement techniques. A member of

ASTM and STLE for over 35 years, Jack co-founded STLE’s Condition Monitoring Education Course. He

also co-founded the OMA (Oil Monitoring Analyst) certification program at STLE and is certified OMA

1 and OMA 2. Jack holds a B.S. in Chemistry (University of California [Berkeley]) and a B.S. in

Management (New York University School of Commerce).


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