With an increased focus on plant productivity and equipment reliability, Supervisory Control and Data Acquisition (SCADA) systems have become vital tools to reduce downtime while increasing asset reliability in hydraulic systems. A SCADA system is a computer system that essentially gathers and analyzes real-time data.

Figure 1. The ISO 4406:1999 fluid cleanliness standards for typical hydraulic components.

These systems monitor critical sensors and data points, providing information on a plant’s network or localized human-machine interface (HMI). Having knowledgeable data and information related to a hydraulic system provides key values that help maintain and protect assets and improve productivity and reliability.

A SCADA system can be used to monitor the following elements of a hydraulic power unit:

  • Reservoir temperature
  • Fluid contamination/particle counter
  • Pressure sensors
  • Level sensors

Reservoir Temperature

Figure 2. The Icount particle detector communicates the 4μ, 6μ, and 14μ channels to the SCADA system.

Maintaining a stable temperature within a hydraulic power unit will prolong the unit’s life and improve hydraulic oil health. Over-temperature and under-temperature alarms can be monitored and recorded to provide information about temperature-related failures. Cold temperatures can cause cavitation due to viscosity change, and high temperatures can also affect system performance and loss of efficiency.

How hot is too hot? Hydraulic fluid temperatures above 180 °F (82 °C) damage most seal compounds and accelerate oil degradation. Hydraulic systems that operate above 180 °F should generally be avoided. Some fluid temperatures are also too high when viscosity falls below the optimum value for the hydraulic system’s components, which can occur well below the 180 °F temperature, depending on the fluid’s viscosity grade.

Fluid Contamination/Particle Counter

Most machine and component manufacturers specify a target ISO cleanliness level for equipment in order to achieve optimal performance (Figure 1). A SCADA system can track and record ISO codes to provide predictive and proactive equipment failure information related to contamination. Contamination types include:

  • New oil: new fluid is not necessarily clean
  • Generated contamination: abrasive wear, cavitation wear, fatigue wear, erosive wear, and corrosive wear
  • External contamination: reservoir breathers, cylinder rod gland, and hydraulic hose

To help meet the fluid cleanliness requirements for typical hydraulic components, a particle counter can communicate the 4μ, 6μ, and 14μ channels to the SCADA system (Figure 2). By collecting real time ISO codes, users can pinpoint specific system issues or internal maintenance processes that can be improved.

Pressure Sensors

Figure 3. A level graph from Parker’s SCLTSD level/temperature controller. The SCLTSD combines the function of a level/temperature switch, sensor, and display. The graph shows data points over time and can be displayed on network or local HMI.

Pressure sensors can be either pressure transducers or pressure switches. Most filters use a DELTA “P” pressure switch, which indicates when it is time to change a filter. A SCADA system can provide a date stamp for when the filter bypass switch has been indicated, and a local user can be notified via local display or network escalation. The ability to monitor the time it takes to change a filter can also provide management and stakeholders with viable information related to maintenance reliability.

Pressure transducers provide analog output to the SCADA system to maintain system performance within a predetermined range. Pressure transducers can be used to measure main system pump pressure and accumulator pre-charge pressure. This is important because pressure spikes and low pressure in the main system pump can indicate that system calibration is required. In addition, accumulator pre-charge pressure loss can drastically upset system function causing equipment failure, loss of production, and poor manufacturing quality.

Level Sensors

Level sensors provide critical information related to system reliability (Figure 3). The minimum level sensor would be a low-level switch tied to the SCADA system and pump-motor control. This process protects the pump from cavitating and degrading the system over time. Multiple level switches can also provide information related to premature failure.

Level transducers provide additional protection for hydraulic system performance, while offering information about oil loss. Oil leaks not only increase environmental concerns, but also raise issues concerned with unplanned cleanup and hazardous waste. Having the ability to capture and record proper oil levels can protect against unplanned downtime and environmental issues.

Other Areas for SCADA Hydraulic Performance

SCADA systems can also be used in a number of other applications related to a hydraulic power unit. These include: case drains for hydraulic pumps, horsepower consumption for prime movers, moisture sensors for hydraulic oil indicating heat exchanger failure, suction ball valve switches for pumps, and ITM (Interactive Technical Manual) upgrades.

This article was written by Matt Shelton, Certified Fluid Power Specialist and Sales Engineer for Kaman Fluid Power, Indianapolis, IN. For more information, Click Here .