By Martin Cuthbert, Managing Director, Webtec
There are seven good reasons why it makes sound business sense to monitor hydraulic flow on mobile machines. Such are the advantages available to both OEMs and end users from the permanent installation of flow monitoring equipment that Webtec, a manufacturer of hydraulic measurement and control products, today sees it as the ‘missing link’ in on- and off-highway hydraulic condition monitoring.
By listening to many customers in the mobile machinery market over the past five years, Webtec was able to identify seven clear challenges that set the premise for the development of an innovative new hydraulic flow meter which meets the needs of modern hydraulic condition monitoring and delivers considerable business gains. Specifically, the challenges were: minimizing unscheduled downtime to save costs, monitoring cycle times to stay abreast of machine health, reducing warranty costs by understanding machine usage patterns, improving energy efficiency to save on fuel, optimizing actuator control to enhance certainty, improving machine safety to protect workers and supporting the elimination of live work (ELW).
Read on to learn more specifics about each of these challenge and how to solve them.
1 — Minimize unscheduled downtime
Installing a flow meter is one of the best ways to monitor pump and actuator performance, allowing engineers to schedule service requirements before the onset of catastrophic failure and enormous costs. A day of downtime for a municipal vehicle could amount to $20,000 a day, while for mining in the precious metals industry, costs can sometimes top $70,000 an hour.
Sure enough, hydraulic machine condition monitoring is not new, but in historical terms many considered ‘flow’ too difficult, so most machines rely on pressure measurement as it is relatively simple to perform. However, pressure is not always useful in locating a fault. For example, suppose a cylinder in normal operation takes 5 seconds to travel full stroke and the applied load creates an operating pressure of 1,000 psi. If a fault occurs, caused perhaps by a loss of pump flow or circuit leakage, the reduced flow would cause the cylinder piston to move slowly, but it would still lift the load. If the load lifts then the pressure must still be 1,000 psi, so the pressure gauge would read the same as normal.
Figure 1: Preventive maintenance may not always be the most suitable.
Instead, to diagnose a problem with actuator speed (too much or too little) it is necessary to measure flow rate. Such an approach can help pinpoint situations such as: insufficient flow caused by pump wear; excessive return or drain line flow prompted by increased component leakage; or a mismatch between actuator flow rate and speed (indicating a loss of volumetric efficiency of the actuator).
To this end, hydraulic flow testers and data loggers are ideal tools in preventative maintenance strategies. Here, scrutinizing pump health periodically helps to estimate remaining life and ensure replacement before catastrophic failure, while simultaneously avoiding the waste of any useful pump life.
Preventive maintenance is a useful and practical procedure wherever there is robust documentation of component service life data and operating conditions are predictable. However, the reality for most on- and off-highway mobile machines is somewhat different. Factors such as vibration, temperature swings, shock and unstable power supply can lead to unexpected events and sudden failures.
Practicality therefore suggests that continuously monitoring hydraulic performance via a permanently mounted flow meter will immediately detect any sudden deterioration and prompt appropriate action. Furthermore, with the right flow monitor it becomes possible to transmit data to the cloud via the vehicle’s CANbus network. Users can subsequently record and analyze performance data remotely and predict problems before they arise, with alarms highlighting any sudden changes.
Webtec’s newly developed CTA series turbine-type flow monitor with CAN bus interface fulfils this exact purpose. Developed in close collaboration with customers, the CTA series monitors both flow rate and temperature at high operating pressures, transmitting data via an SAE J1939 CAN bus found commonly on many vehicles. IP69K-rated for use in harsh operating conditions and fully EMC compliant, this compact, rugged flow monitor is an invaluable instrument that enables maintenance engineers to monitor system performance and schedule remedial service only when necessary rather than at estimated intervals.
Importantly, the new CTA is easy to integrate with IoT solutions and is currently in use at over 10 customers in sectors that include mining, municipal, agriculture and screening/crushing, deploying many different CAN buses and controllers.
2 — Track cycle time to indicate machine health
With the CTA flow meter permanently installed, a number of further benefits arrive from the continuous monitoring of machine health and operational parameters. Monitoring cycle times, in particular, can highlight a gradual loss of productivity long before this becomes an issue or leads to a catastrophic failure.
Figure 2: Remote monitoring is especially useful for autonomous vehicles
Assuming an overall machine cost of $500 per hour, a 5-hour job will cost $2,500 at 100% efficiency. However, a machine that is only 80% efficient means the same 5-hour jobs now needs 6.25 hours, suddenly costing $3,125. A machine operating 5-10% slower is hard to see without monitoring the pump’s power output. For OEMs, this tactic supports the provision of a ‘health monitoring’ subscription service, and provides extra detail and confidence around scheduling future maintenance.
3 — Reduce warranty costs
Combining flow and pressure data permits the calculation of hydraulic power, which in turn can indicate how ‘hard’ a machine is working – whether due to operator behavior or the ‘hardness’ of the earth or rock. These usage patterns relate directly to wear and can feed into a ‘power by the hour’ business subscription model. This type of data can also prove invaluable when deciding warranty claims.
Figure 3: Predictive maintenance continuously monitors performance
4 — Monitor drive motor efficiency to save fuel
For actuators that operate continuously over long periods, such as those found on conveyor or mixer drives, comparing the actuator flow rate to the actuator speed will establish its volumetric efficiency. Any deterioration in efficiency will therefore signal the need for remedial action. In addition, this approach takes into account any leakage from the inlet port to the outlet port that would not be obvious simply by monitoring the case drain flow.
Such a strategy is also applicable to the overall machine. If the engine is only driving hydraulics, then measuring the hydraulic power output will reveal the power output of the entire machine, which indicates how long the fuel/battery will last.
Figure 4: Auto Flow Monitor principle of operation
5 — Improve certainty with closed-loop speed control
Using closed-loop feedback will help to optimize flow control, particularly where an actuator is operating in a hostile environment. Where actuators function in challenging conditions, possibly subject to rain or salt water, electrical discharges or lightning strikes, or extreme temperatures, monitoring and transmitting the actuator speed by electrical sensors and cabling may prove problematic.
Instead, a feedback signal proportional to the actuator speed is obtainable by monitoring the actuator flow rate, which is then suitable for use in the closed-loop speed control system of the actuator. This signal can relay back to the proportional hydraulic flow control valve, with flow adjusted accordingly.
Figure 5: Flow Monitor used in control loop in difficult environments
6 — Enhance safety
Any mobile machine with hydraulic flow presents a safety risk if someone inadvertently opens a cover, for example. Normal practice here is the use of trip switches, but these are not tamper-proof. Flow monitoring is a good back-up strategy.
By monitoring pump flow, the system designer has a built-in secondary safety function with real-time feedback. It is possible to see whether the pump is delivering flow or not by witnessing whether oil is returning to tank or the motor drive. The set-up can subsequently enable/disable other functions to keep operators safe.
Figure 6: System performance can be monitored remotely.
7 — Elimination of Live work (ELW)
In a continuous drive to improve safety in the heavy machinery industry, OEMs, dealers and operators in the construction & mining industry are increasingly focused on how such machines can be maintained and repaired without a person having to enter the machine while its operating, hence the phrase Elimination of Live Work. Traditionally to test a hydraulic pump on a machine you would need two technicians to attend to fit the flow meter into the circuit, and then for one to run the machine while the other monitors the pump performance. By using a permanently installed flow monitor, no additional equipment needs to be installed, so only one person is required to carry out the job and flow rates can be monitored remotely thus removing the technician from a potentially dangerous environment.
Webtec
webtec.com
Filed Under: Components Oil Coolers, Sensors, Sensors & Gauges, Technologies
