FORM 2
THE PATENTS ACT 1970
(39 of 1970)
&
The Patent Rules, 2003
Complete Specification
(See section 10 and rule 13)
An Integrated Hydraulic Fluid Quality Monitoring Device And A Method To Monitor Hydraulic Fluid Quality In Hydraulic Systems
Mahindra and Mahindra Ltd.
An Indian company registered under the Indian Companies Act, 1956.
Gateway Building, Apollo Bunder, Mumbai - 400001, Maharashtra, India.
The following specification particularly describes the invention and the manner in which it is to be performed:

An integrated hydraulic fluid quality monitoring device and a method to monitor hydraulic fluid quality in hydraulic systems
Field of invention:
The present invention relates to indication and monitoring of fluid contamination of the hydraulic system. In particular, the invention relates to monitoring of fluid quality in an auto mode as well as through visual comparison.
Normally, the fluid contamination indicators currently available in the market are high cost equipment which works on the principle of foreign particle counting per specific volume of hydraulic fluid. Hydraulic fluid contamination indicator helps the equipment operator to monitor the condition of the hydraulic fluid in auto mode as well as visually through color comparison of the hydraulic system fluid flowing through glass tube and the sample fluid kept in test tubes by its side.
Background of invention:
The terms 'oil', 'hydraulic system oil', system oil, and 'fluid', hydraulic system fluid', and 'system fluid' are used interchangeably in this specification. It is extremely important to use clean fluid in a hydraulic system, fluid that contains contaminants can shorten the life of a hydraulic system's components. In fact, it has been widely regarded that the primary cause of a hydraulic system failure is fluid contamination.

US patent 6449580 mentions that mineral and synthetic working fluids, such as motor oil, gear oil and hydraulic liquids, are frequently used essential components of mechanical systems. Working fluids provide lubrication and/or force and energy transfer in the mechanical system. Unfortunately, working fluids are subject to degradation with use over time. For example, working fluids may be contaminated by water or debris. In addition, contamination of working fluids by water and dissolved air leads to accumulation of oxide products, increasing the fluid viscosity and reducing its lubricating effect. Such contamination and degradation leads to increased friction in the mechanical system and ultimately to premature failure due to wear.
It has also been reported that the most common type of oil contamination is particulate contamination causes by solid particles. It has been reported that up to 90% of all hydraulic system failures can be attributed to contaminated oil. Another study found that particle contaminated hydraulic oil accounts for 82% of all wear. Filtration systems may help avert the problem, but knowing what gets into hydraulic oil and why is key to selecting the correct one. In fact, to ascertain that contamination has actually taken place is a key step in adopting preventive measures against failures related to oil contamination.
There are various devices and systems available to monitor the degradation of hydraulic oil. For example, US patent 6449580 discloses a method for evaluating properties of oil using dielectric spectroscopy. It further states that in many

industrial environments, working fluids are regularly analyzed to determine if fluid breakdown is occurring, threatening mechanical failure. Laboratory methods for detecting working fluid viscosity and degradation are described in ASTM standards D445-94 entitled Kinematic Viscosity of Transparent and Opaque Liquids (the Calculation of Dynamic Viscosity), D95-83 (1990) entitled Water in Petroleum Products and Bituminous Materials by Distillation and D664-95 entitled Acid Number of Petroleum Products by Potentiometric Titration.
One drawback of such methods is that accurate analysis of hydraulic system fluid
typically requires shipment of a fluid sample to a laboratory for analysis. This
results in latency between the sampling of the working fluid and the generation of
analysis results. This problem is particularly vexing where the mechanical system
is in a moving vehicle such as a ship or aircraft, or is located in a rural area such
as a factory.
Unfortunately, these laboratory methods have other major weaknesses. First, laboratory analysis has a significant cost, and typically cannot be performed on-site. Furthermore, if a working fluid sample must be transported off-site for analysis, a significant delay will occur between sampling and receipt of the test results.
The US patent 6449580 further states that a relatively simple method for analysis of working fluid which does not require extensive laboratory equipment and can

be performed on-site without expertise, would clearly be preferable. Ideally, the
simplicity of the method would permit an analyzing device for evaluating the
working fluid, to be incorporated into the mechanical system, so that analysis of
oil in the system is performed continuously while the system is on-line, i.e., still
operating. Such an approach would eliminate all unnecessary downtime, because
the system could be operated continuously until the oil is found to need
replacement, and the replacement can be made immediately rather than after an oil
sample has been delivered to a laboratory and analyzed. Furthermore, in
automotive applications, an on-line oil analysis method that identifies when oil
should be changed, could in many instances lead to greater mileage between oil
changes reducing maintenance costs, environmental strain caused by disposal of
waste oil, and inconvenience.
The US patent 6449580 further mentions that several proposals have been made for performing on-site or on-line analysis of working fluid using relatively simple analyzing devices. One popular proposal involves measuring dielectric properties of the working fluid and implying properties of the working fluid from the results. For example, U.S. Pat. No. 4,646,070 describes a sensor including a pair of electrodes which are placed in an oil-carrying passage of the mechanical system, and immersed in the flowing oil to form a capacitor. The capacitance of this capacitor varies as a function of the permittivity of the oil. A measuring circuit determines the permittivity of the oil and generates a measure of the quality of the oil.

U.S. Pat. No. 4,733,556 describes a sensor with two pairs of capacitive electrodes.
The first pair of electrodes is immersed in oil flowing in the operating mechanical
system, and a second pair of electrodes is immersed in reference oil. A circuit
compares the capacitance measured from the two pairs of electrodes, and
produces a measure of the quality of the oil. Other sensors measure the variation
of the permittivity of oil over frequency, and use the resulting data to determine a
measure of the quality of the oil.
Unfortunately, these proposed systems have not been widely accepted for measurement of oil parameters. The permittivity of a working fluid such as oil depends on a large number of independent parameters. For example, the concentration of oxidized molecules (acid content), water content, particulate content, viscosity and temperature of oil all influence the permittivity of oil and its variation over frequency. Thus, a measurement of permittivity per se or the variation of the permittivity over frequency will not determine a value for any one of these parameters independent of the others. However, to adequately characterize the performance of a working fluid and determine whether the working fluid should be replaced, all of the parameters of water content, acid content, viscosity and density, need to be independently and accurately measured, and then evaluated separately. The quality measurements produced by the systems described in the above patents, are dependent upon several different oil parameters, and thus cannot be related to any one parameter or easily used to answer the basic question of whether oil should be replaced.

Soviet patent 1,566,291, authored by an inventor of this application, describes a
method for analyzing the properties of oil based on variation of dielectric
parameters of the oil over temperature. This method produces measurements of
parameters of oil that are independent of most other parameters. In this method, a
capacitive-type sensor is immersed in the oil, and a circuit stimulates the sensor to
determine the dielectric loss in the capacitive sensor. The dielectric loss of the oil
(which results from the imaginary part of the complex function for permittivity)
varies non-linearly with temperature. In accordance with the method of the Soviet
'291 patent, the oil is heated while monitoring the change in the dielectric loss.
The ratio of the imaginary to the real part of the permittivity is known as tangent
delta or tg.delta.. At the oil's "critical temperature", tg.delta. reaches a maximum
value. This critical temperature is identified by monitoring tg.delta. as the oil
temperature is increased, and identifying the temperature at which tg.delta. ceases
increasing and begins decreasing.
Unfortunately, the method described in the Soviet '291 patent is flawed in several ways. First, the described method for locating the critical temperature is not accurate. Measurement variations can produce an apparent decrease in tg.delta., incorrectly suggesting that the critical temperature has been located, resulting in a mis-determination of the critical temperature and mis-determination of the oil viscosity. Furthermore, the value of tg.delta. at the critical temperature is not only related to the acid content of the oil, it is also related to the water content of the

oil. Accordingly, in the described method, variation in water content of the oil can lead to an incorrect measurement of acid content.
Other technologies, such as the one disclosed in US patent application no. 20100027006, for oil contamination indication based on the NAS value examiner work on principle of particles counting per unit volume to determine its grade as per NAS standards. Though this technology claims to precisely determine the NAS value, it is not economically viable to install such expensive technology on every hydraulic power pack in a typical the machine shop/shop floor.
Accordingly, there remains a need for a method for measuring parameters of oil including viscosity, density, acid content and water content, independently of other parameters, which is accurate and requires relatively simple analyzing devices suitable for on-site or on-line applications.
Objects of the invention:
1. The main object of the present invention is to provide a simple, low cost device to indicate the contamination of hydraulic system fluid.
2. Yet another object of the invention is to provide such a device which can directly be coupled to hydraulic system of the machine to monitor various critical parameters.

3. Yet another object of the invention is to provide a device through which machine can be operated only in safe working zone of fluid contamination beyond which the machine should stop automatically.
4. A further object of the invention is to provide a device which will raise an alarm on surpassing the safe fluid contamination limit.
5. Yet further object of the invention is to monitor the hydraulic fluid level to ensure proper working of hydraulic system.
6. Still further object of the invention is to monitor and control the hydraulic system by continuously monitoring the hydraulic fluid temperature and shut down the hydraulic system if the hydraulic fluid temperature overshoots the prescribed range.
7. Still another object of the invention is to provide a device to monitor the hydraulic fluid pressure to avoid any malfunctioning of the system.
Summary of invention:
The invention provides an integrated device to monitor parameters related hydraulic fluids used for proper functioning of hydraulic systems. The invention provides a system of sensors and indicators which allows the hydraulic system operator to take the necessary corrective action. The system is simple to install and monitor and easy to maintain. It is also extremely inexpensive but of acceptable reliability.

List of parts:
1. Integrated hydraulic fluid 10. Third transparent tube monitoring device 11. Fluid return line
2. Analog pressure controller 12. First relay
3. Digital temperature controller 13. Second relay
4. Fluid level sensor 14. A system of indicators
5. Alarm system 15. First indicator
6. Fluid contamination level 16. Second indicator indicator 17. Third indicator
7. First transparent tube 18. Fourth indicator
8. Contrast sensor
9. Second transparent tube
List of figures:
Figure 1 shows the fluid contamination level monitoring device
Figure 2 shows the schematic of the integrated device of the invention
Figure 3 shows a flow chart for operation of a hydraulic system using the present invention

Description of invention:
In the less affluent parts of the world, there is a need for providing a simple and cost-effective system for continuous on-site monitoring of the quality of hydraulic system fluids. Throughout this specification the words oil and fluid are used interchangeably and taken to mean fluid used in a hydraulic system.
Visual examination of oil or any hydraulic fluid is one of the simplest and most effective ways to determine the fluid's condition. In this respect, fluid colour has been found to be one of the simplest indicators to monitor. It is well known that typical clean hydraulic fluid is amber in color. A milky, dark, or otherwise abnormal color may indicate the presence of one or more contaminants. A milky appearance implies contamination by water. A marked change in the smell of the hydraulic fluid can indicate a chemical breakdown. This type of breakdown is generally due to air that has become entrained in the fluid, which creates varnishlike nitrogen-oil compounds that contaminate the fluid.
Typically three issues are related to chemistry-related issues. Issues related to fluid colour change can be categorised as:
• Cleanliness-related issues. Issues related to contamination during manufacture, assembly or operation
• Wear-related issues.
• Issues related to wear mechanisms.

Determination of fluid degradation by color change is a well-accepted method. It has been reported that fluid color was an accurate indicator of the level of 3um to 5|im particles within the fluid.
There are also other indicators such as the system pressure, hydraulic fluid temperature and hydraulic fluid level, which when considered together with the hydraulic fluid colour, provide a much better indication of the fluid quality.
The present invention provides a system that provides an integrated monitoring device (1) for hydraulic fluid quality based on the hydraulic pressure, temperature, level of the hydraulic fluid and visual quality. The pressure and temperature parameters are monitored using preferably an analog pressure controller (2) and a digital temperature controller (3) respectively. A fluid level sensor (4) is provided to monitor the fluid level.
If any of these parameters go outside the prescribed range, an alarm system (5) has been provided to allow further action to be taken, including system shutdown. Figure 1 shows the front elevation of the fluid contamination level indicator (6) which forms a part of the integrated monitoring tool of the invention. It shows an open ended first transparent tube (7), preferably made of glass, a contrast sensor (8) and a second and a third transparent tubes. The first transparent tube is open at both ends whereas the second and third transparent tubes (9, 10) are typically similar to test tubes used in chemistry experiments.

Typically the hydraulic systems have a reservoir of hydraulic fluid from which the fluid is circulated through the system and returns back to a reservoir of hydraulic fluid. The center-mounted, open-ended first transparent tube is connected to the fluid return line (11) from a hydraulic actuator of the hydraulic system at one end, and the other end is connected to return line to the reservoir.
The second and third transparent tubes contain samples of hydraulic fluid at the ends of the purity spectrum of the specific fluid. In a specific case where the hydraulic fluid conforms to NAS grading, one of these two tubes will carry the desired lowest NAS grade sample and the other one the most allowed highest NAS grade. For example, in the case of hydraulic systems complying with NAS standards, one of the tubes may carry the fluid of the most allowed highest of the allowable NAS grade, whereas the other tube may carry the desired lowest of the allowable NAS grade.
The contrast sensor (8) may be of any type that will sense the level of impurity in the system fluid. The accuracy of the device of the invention will depend on the accuracy of the contrast sensor.
The sensors and measuring devices for other parameters, namely the pressure, the temperature, and the level are provided in accordance with the schematic of Figure 2.

The contrast sensor (8) mounted in front of the first transparent tube, through which the system fluid flows, allows an automated comparison of the system fluid quality with the NAS gradation. The contrast sensor (8) is set by rotating the set screw provided in it. The comparison may be made using any standards and not just the NAS standards. The highest allowed and lowest desirable grades may therefore be based on any industry standards.
The contrast sensor is set at the acceptable level of contamination by keeping it in front of the allowed highest NAS grade sample (i.e. tube at right side of middle tube as indicated in Figure 1) and by rotating the setting screw until its circuit opens. In some types of sensors, the setting may be done up to the point of closing of the circuit. Next, the sensor is placed in front of the first tube. The movement of the contrast sensor between the various tubes is facilitated by any suitable means. Preferably the means provided for this purpose is a slide/frame (8a) as shown in Figure 2. The contrast sensor (8) is slid over the slide/frame (8a) to near the appropriate tube and after the setting is completed, it is slid back to its position in front of the first transparent tube and fitted there.
During the operation of the device, the status of the circuit changes from its initial setting. In the case of the sensor which has an open circuit at the acceptable grade fluid, and closed otherwise, when the fluid quality is equal to or higher than the acceptable quality, the sensor circuit will remain closed. During the operation of

the system, as the fluid color changes with use and time, the sensor continuously, or at set intervals, senses the change of colour of the fluid. Whenever the darkness of the system fluid, as detected from the fluid in first tube, equals or exceeds to that is set in sensor, it suggests that the fluid contamination level has equaled or exceeded the acceptability limit.
At this stage the system sends a signal/feedback to a first relay (12) and raises alarm which is typically in the form of a system of indicators (14). The operator of the system has the choice of shutting down the system if he wishes or of taking any other action. The system will restart only if the cause of the alarm is removed - that is if the system fluid is replaced by fluid of level of contamination at acceptable or lower level.
As shown in Figure 2, the integrated device shows that a single power source feeds into the first relay and a second relay (13). Another single power source supplies the temperature and pressure controllers.
Alternatively, it is possible to supply power to all sensors and/or controllers individually or in a group. The supply of power may be through the mains or generator based or using standalone batteries.
The integrated device of the present invention for hydraulic fluid monitoring operates on the basis of the logic described above. With regards the fluid level,

when the level falls below prescribed level, the second relay (13) receives signal from level sensor (which senses the presence/absence of liquid) the relay closes the circuit of a third indicator (17) and raises the fluid level alarm. Similarly, when the hydraulic fluid temperature raise beyond the prescribed temperature, the temperature controller closes the circuit of the first indicator (15) and raises the high temperature alarm by making the first indicator (15) glow. Finally, the pressure controller will raise the pressure alarm by sending an appropriate signal to a fourth indicator (18) if the fluid pressure falls below set point or range, depending upon application.
An alarm will be raised in the case any one of the parameters falls outside the acceptable limits. The indicators may be of any colour. Alternatively, the indicators may be of audio type. What action to take if any, and when to take it -that is whether to take an action in the case any single parameter or any specific parameter falls below the acceptable limit, or a combination of parameters fall below their respective limits - is entirely operator dependent.
Likewise, the contrast sensor which is provided at a suitable location, preferably just in front of the first transparent tube through which the hydraulic system oil flows, continuously or intermittently senses the darkness/contrast level of oil to that which is set in sensor by operator. Until its contrast level reaches the set point its circuit remains close. Now as and when it touches the set contrast level, immediately its circuit opens and sends signal to the first relay which raise the

alarm by glowing the second indicator (16). Also this signal can be used to shut off the hydraulic system likewise.
The indicators may be of audio or visual type or a combination thereof. The transparent tubes may be made of glass or any other transparent material compatible with the system fluid it is expected to carry.
As a hydraulic system of the machine fitted with the integrated hydraulic fluid quality monitoring device of the invention is operated, the returning oil from the hydraulic actuator is passed through the see-through first transparent tube mounted in the middle of oil contamination indicator unit. As an added advantage, as all tubes, namely the first, the second, and the third, are transparent, the quality or contamination of the fluid flowing through the system is easily visually color-compared with the fluids contained in the second and the third tubes.
It is thus evident that the present invention comprises the following embodiments.
1. An integrated hydraulic fluid quality monitoring device to monitor hydraulic fluid parameters such as the fluid level, the fluid pressure, the fluid temperature, and the fluid contamination level in hydraulic systems, characterized in that it comprises a combination of sensors, relays and indicators, and wherein the fluid contamination level is monitored using a contrast sensor.

2. An integrated device as described in embodiment no. 1, said combination of monitors and sensors comprises a fluid pressure monitor, a fluid level sensor, and a fluid temperature monitor, a set of relays, namely a first relay connected to either of said contrast sensor or said fluid level sensor, and a second relay connected to the remaining sensor, a set of indicators comprising at least one indicator, wherein when the value of at least one of the parameters falls outside the acceptable limit for that parameter, the corresponding relay or controller raises an alarm through the relevant indicator.
3. An integrated device as described in embodiment no. 2, wherein the number of indicators is four and each indicator is connected to one of the two relays or one of the two sensors, namely the fluid level sensor or the contrast sensor, and wherein none of the indicators receive more than one input.
4. An integrated device as described in embodiments 1 to 3, wherein said set of indicators comprises a first indicator, a second indicator, a third indicator, and a fourth indicator, each indicator receiving signal from either any one of the two relays, or from the temperature or pressure controllers.
5. An integrated device as described in claims 1 to 4, wherein said visual monitor comprises a three transparent tubes, namely a first tube, a second tube, and a third tube, wherein said first tube is open at both ends, said second tube is connected at its one end to the return line from a manifold at one end, and the other end is connected to return line to a reservoir containing hydraulic system fluid, and further wherein, a contrast sensor is attached to said first tube on its side surface, and said second and third tubes are

positioned on either side of said first tube, one of said second and third tubes carrying fluid of highest acceptable and lowest acceptable qualities.
6. An integrated device as described in embodiments 1 to 5, wherein said contrast sensor is set to sense colour of system hydraulic fluid and compare it with the colour of fluid of lowest acceptable quality.
7. An integrated device as described in embodiments 1 to 6, wherein if the colour of hydraulic system fluid is darker than that of the lowest acceptable quality fluid, said colour sensor sends an alarm signal to the corresponding indicator.
8. A method of monitoring hydraulic system fluid parameters comprising the steps of:
- providing a combination of sensors, relays and indicators, and wherein the fluid contamination level is monitored using a visual monitor,
- setting the range of acceptable values for fluid colour, fluid pressure, fluid level, and fluid temperature in respective sensors,
- raising alarm if any of the said parameters falls outside the corresponding acceptable limits.
9. A method of monitoring hydraulic system fluid quality as described in
embodiment 7 to 8, wherein said combination of monitors and sensors
comprises a fluid pressure monitor, a fluid level sensor, and a fluid
temperature monitor, a set of relays, namely a first relay connected to either
of said contrast sensor or said fluid level sensor, and a second relay connected
to the remaining sensor, a set of indicators comprising at least one indicator,

wherein when the value of at least one of the parameters falls outside the acceptable limit for that parameter, the corresponding relay or controller raises an alarm through the relevant indicator.
10. A method of monitoring hydraulic system fluid quality as described in embodiments 7 to 9 wherein the number of indicators is four and each indicator is connected to one of the two relays or one the two fluid level sensor or the contrast sensor, and wherein none of the indicators receive more than one input.
11. A method of monitoring hydraulic system fluid quality as described in embodiments 7 to 10, wherein said set of indicators comprises a first indicator, a second indicator, a third indicator, and a fourth indicator, and wherein said method further comprises a step of each indicator receiving signal from either any one of the two relays, or from the temperature or pressure controllers.
12. A method of monitoring hydraulic system fluid quality as described in embodiments 7 to 10, wherein said visual monitor comprises a three transparent tubes, namely a first tube, a second tube, and a third tube, wherein said first tube is open at both ends, said second tube is connected at its one end to the return line from a manifold at one end, and the other end is connected to return line to a reservoir containing hydraulic system fluid, and further wherein, a contrast sensor is attached to said first tube on its side surface, and said second and third tubes are positioned on either side of said

first tube, one of said second and third tubes carrying fluid of highest acceptable and lowest acceptable qualities.
13. A method of monitoring hydraulic system fluid quality as described in embodiments 7 to 12, wherein said method further comprises the step of sending an alarm signal to the relevant indicator if the colour of hydraulic system fluid is darker than that of the lowest acceptable quality fluid.
14. A method of monitoring hydraulic system fluid quality as described in embodiments 7 to 13, and wherein said method further comprises the step of visually comparing the colour of hydraulic fluid in said first tube with that of the fluid of lowest acceptable quality.
15. An integrated device as described in embodiments 1 to 7, wherein said indicators may be audio or visual type or a combination of audio and visual types.
16. A method of monitoring hydraulic system fluid quality as described in embodiments 8 to 14, wherein said indicators may be audio or visual type or a combination of audio and visual types.
17. An integrated device as described in embodiments 1 to 7 and 15, wherein said
transparent tubes may be made of glass, plastic or any transparent material.
18. A method of monitoring hydraulic system fluid quality as described in
embodiments 8 to 14, and 16, wherein said transparent tubes may be made of
glass, plastic or any transparent material.

While the above description contains much specificity, these should not be construed as limitation in the scope of the invention, but rather as an exemplification of the preferred embodiments thereof. It must be realized that modifications and variations are possible based on the disclosure given above without departing from the spirit and scope of the invention. Accordingly, the scope of the invention should be determined not by the embodiments illustrated, but by the appended claims and their legal equivalents.

We claim:
1. An integrated hydraulic fluid quality monitoring device to monitor hydraulic fluid parameters such as the fluid level, the fluid pressure, the fluid temperature, and the fluid contamination level in hydraulic systems, characterized in that it comprises a combination of sensors, relays and indicators, and wherein the fluid contamination level is monitored using a contrast sensor.
2. An integrated device as claimed in claim 1, said combination of monitors and sensors comprises a fluid pressure monitor, a fluid level sensor, and a fluid temperature monitor, a set of relays, namely a first relay connected to either of said contrast sensor or said fluid level sensor, and a second relay connected to the remaining sensor, a set of indicators comprising at least one indicator, wherein when the value of at least one of the parameters falls outside the acceptable limit for that parameter, the corresponding relay or controller raises an alarm through the relevant indicator.
3. An integrated device as claimed in claim 2, wherein the number of indicators is four and each indicator is connected to one of the two relays or one of the two sensors, namely the fluid level sensor or the contrast sensor, and wherein none of the indicators receive more than one input.
4. An integrated device as claimed in claims 1 to 3, wherein said set of indicators comprises a first indicator, a second indicator, a third indicator, and a fourth indicator, each indicator receiving signal from either any one of the two relays, or from the temperature or pressure controllers.

5. An integrated device as claimed in claims 1 to 4, wherein said visual monitor comprises a three transparent tubes, namely a first tube, a second tube, and a third tube, wherein said first tube is open at both ends, said second tube is connected at its one end to the return line from a manifold at one end, and the other end is connected to return line to a reservoir containing hydraulic system fluid, and further wherein, a contrast sensor is attached to said first tube on its side surface, and said second and third tubes are positioned on either side of said first tube, one of said second and third tubes carrying fluid of highest acceptable and lowest acceptable qualities.
6. An integrated device as claimed in claims 1 to 5, wherein said contrast sensor is set to sense colour of system hydraulic fluid and compare it with the colour of fluid of lowest acceptable quality.
7. An integrated device as claimed in claims 1 to 6, wherein if the colour of hydraulic system fluid is darker than that of the lowest acceptable quality fluid, said colour sensor sends an alarm signal to the corresponding indicator.
8. A method of monitoring hydraulic system fluid parameters comprising the steps of:
- providing a combination of sensors, relays and indicators, and wherein the fluid contamination level is monitored using a visual monitor,
- setting the range of acceptable values for fluid colour, fluid pressure, fluid level, and fluid temperature in respective sensors,

- raising alarm if any of the said parameters falls outside the corresponding acceptable limits.
9. A method of monitoring hydraulic system fluid quality as claimed in claims 7 to 8, wherein said combination of monitors and sensors comprises a fluid pressure monitor, a fluid level sensor, and a fluid temperature monitor, a set of relays, namely a first relay connected to either of said contrast sensor or said fluid level sensor, and a second relay connected to the remaining sensor, a set of indicators comprising at least one indicator, wherein when the value of at least one of the parameters falls outside the acceptable limit for that parameter, the corresponding relay or controller raises an alarm through the relevant indicator.
10. A method of monitoring hydraulic system fluid quality as claimed in claims 7 to 9 wherein the number of indicators is four and each indicator is connected to one of the two relays or one the two fluid level sensor or the contrast sensor, and wherein none of the indicators receive more than one input.
11. A method of monitoring hydraulic system fluid quality as claimed in claims 7 to 10, wherein said set of indicators comprises a first indicator, a second indicator, a third indicator, and a fourth indicator, and wherein said method further comprises a step of each indicator receiving signal from either any one of the two relays, or from the temperature or pressure controllers.
12. A method of monitoring hydraulic system fluid quality as claimed in claims 7 to 11, wherein said visual monitor comprises a three transparent tubes, namely a first tube, a second tube, and a third tube, wherein said first tube is

open at both ends, said second tube is connected at its one end to the return line from a manifold at one end, and the other end is connected to return line to a reservoir containing hydraulic system fluid, and further wherein, a contrast sensor is attached to said first tube on its side surface, and said second and third tubes are positioned on either side of said first tube, one of said second and third tubes carrying fluid of highest acceptable and lowest acceptable qualities.
13. A method of monitoring hydraulic system fluid quality as claimed in claims 7
to 12, wherein said method further comprises the step of sending an alarm
signal to the relevant indicator if the colour of hydraulic system fluid is darker
than that of the lowest acceptable quality fluid.
14. A method of monitoring hydraulic system fluid quality as claimed in claims 7 to 13, and wherein said method further comprises the step of visually comparing the colour of hydraulic fluid in said first tube with that of the fluid of lowest acceptable quality.
15. An integrated device as claimed in claims 1 to 7, wherein said indicators may be audio or visual type or a combination of audio and visual types.
16. A method of monitoring hydraulic system fluid quality as claimed in claims 8 to 14, wherein said indicators may be audio or visual type or a combination of audio and visual types.
17. An integrated device as claimed in claims 1 to 7 and 15, wherein said transparent tubes may be made of glass, plastic or any transparent material.

18. A method of monitoring hydraulic system fluid quality as claimed in claims 8 to 14, and 16, wherein said transparent tubes may be made of glass, plastic or any transparent material.