--- title: "Hydraulic Fluid & Fuel Cleanliness Monitoring | Aethair" description: "Fluid cleanliness monitoring for hydraulic systems, lubrication oil, and aviation fuel: online particle counting coded to ISO 4406 / NAS 1638 for…" url: https://aethair.io/solutions/industrial-fluids/ --- Aethair solutions # Hydraulic & Fuel Cleanliness ISO 4406 oil cleanliness and aviation fuel Fluid cleanliness monitoring for hydraulic systems, lubrication oil, and aviation fuel: online particle counting coded to ISO 4406 / NAS 1638 for hydraulic and lube systems, and filter differential pressure per ATA 103 / EI 1581 for jet-fuel filtration. [Schedule a call](https://calendly.com/d/ctdd-mkr-v9v/aethair-demo-website) [Build a Configuration](https://aethair.io/build/?params=particle_count_fluid\&solution=industrial-fluids) At a glance 1 core parameter [Fluid Particle Count (ISO 4406)](https://aethair.io/parameters/particle_count_fluid/) 2 devices cover it - **Thiamis** Parker Fluid & Fuel Quality Why it matters ## Why Hydraulic and Fuel Systems Monitor Cleanliness In hydraulic systems, engines, and fuel handling, the cleanliness of the fluid determines the life of the equipment it flows through. Most wear and most failures in hydraulic and lubrication systems trace back to particulate contamination (abrasive particles that score valves, seize spools, and erode pumps), so controlling and verifying fluid cleanliness is central to reliability. In aviation and fuel logistics, contaminated or water-laden fuel is a flight-safety and quality issue, and filtration must be shown to be working before fuel is delivered. Monitoring cleanliness turns maintenance from a fixed schedule into a condition-based practice and provides the documented proof that a fluid or a fuel meets its required standard. The economics are compelling: catching a rising particle count early prevents the cascade of wear that a contaminated system inflicts on itself. What to measure ## What to Measure The core panel covers the main program. Other parameters are added for a specific site or requirement. **Particle counting to ISO 4406** is the core measurement for hydraulic and lubricating oils. The standard expresses cleanliness as a code based on the number of particles above defined sizes: a single comparable rating for a fluid's condition. A rising count is an early warning of contamination ingress, filter failure, or component wear, well before performance suffers. **Filter differential pressure** is the companion measurement: the pressure drop across a filter rises as it loads, signalling when an element is spent, and in aviation fuel handling this check is central to the ATA 103 practice for clean fuel delivery. **Water content** is often added, since water is as damaging as solid particles in both hydraulic oil and fuel. Fluid Particle Count (ISO 4406) Fluid / Level / Flow Fluid particle counting coded to ISO 4406 is the core measurement of hydraulic, lubrication, and fuel cleanliness, since contamination is the dominant cause of component wear and system failure. Continuous inline particle counting tracks cleanliness in real time, driving filtration and maintenance decisions and providing the condition-monitoring record that protects expensive machinery. [Fluid Particle Count (ISO 4406): sensors, units, and every standard](https://aethair.io/parameters/particle_count_fluid/) Flow Rate Often added · Fluid / Level / Flow Volumetric flow rate (open-channel or pipe). [Flow Rate: sensors, units, and every standard](https://aethair.io/parameters/flow/) Fluid Differential Pressure Often added · Fluid / Level / Flow Differential pressure across a fuel or hydraulic filter or filter/separator vessel, flow-corrected per ATA 103 / EI 1581 so it can be read against a fixed change-out limit. [Fluid Differential Pressure: sensors, units, and every standard](https://aethair.io/parameters/differential_pressure_fluid/) Volume (totalized) Often added · Fluid / Level / Flow Totalized volume. [Volume (totalized): sensors, units, and every standard](https://aethair.io/parameters/volume/) **Methods and guidance:** [ISO 4406: fluid cleanliness coding (SAE AS4059; NAS 1638 legacy)](https://aethair.io/standards/iso_4406/) [ATA 103 / EI 1581: aviation fuel filtration and differential pressure](https://aethair.io/standards/ata_103/) [ISO 11171: calibration of automatic particle counters for liquids](https://aethair.io/standards/iso_11171/) The setup ## How a Monitoring Setup Works Fluid cleanliness monitoring uses a Thiamis gateway connected to an inline particle counter that reports the ISO 4406 cleanliness code, plumbed into the hydraulic or fuel line and logging continuously so that a rising count raises an alert. Filter differential pressure can be monitored alongside it with a pressure sensor rated for the line, also on the Thiamis, so a loading filter is caught before it is bypassed or blinded. (The Aethair PRO's differential-pressure cartridge measures air pressure between rooms and is not designed for a fluid line.) The counter is placed to sample representative fluid, downstream of the component or filter of interest, and its data feeds condition-based maintenance decisions rather than a calendar. The recommended configuration below is the ISO 4406 particle counter on a Thiamis. Use the configurator to add pressure, flow, or extra measurement points for your system. [Customize this configuration](https://aethair.io/build/?params=particle_count_fluid\&solution=industrial-fluids) Which monitor ## The Instruments in This Configuration A [Thiamis](https://aethair.io/products/thiamis/) gateway logs these instruments continuously and sends their readings to Environet over 4G LTE (cellular data included) or the site's Wi-Fi. There they get the same alerts, reports, dashboards, and API as any Aethair monitor, in one account with every other device on the site, instead of a separate vendor app for each instrument. Thiamis runs on mains power, a solar panel, or an external battery. ### [Parker Fluid & Fuel Quality](https://aethair.io/sensors/parker-fluid-fuel-quality/) Parker icountPD inline/online laser particle detector for hydraulic, lube-oil, and fuel systems; laser-diode optical particle counting reports fluid cleanliness as ISO 4406 codes (also NAS 1638 / AS4059) across four size channels >4/>6/>14/>30 µm(c), to ±1 ISO code, over RS-232. [How Thiamis connects them](https://aethair.io/products/thiamis/) What you get ## Readings, Alerts, and the Report That Proves It Every reading goes to the Aethair platform. Here is what a monitoring program gets from it. ### [Live data and alerts](https://aethair.io/platform/environet/) Every reading in Environet as it happens, with alerts by email, SMS, or webhook at the thresholds you set. ### [Compliance reports](https://aethair.io/platform/reports/) Scheduled or on-demand reports against the standards above or your own limits, as PDF or a secure link. ### [Dashboards and AI analysis](https://aethair.io/platform/dashboards/) Live displays for a site or the public, and Noesis answering questions about the data in plain language. ### [Your data, through the API](https://docs.environet.io/) Live and historical readings as JSON or CSV through the Environet API (OpenAPI 3.2), for a building management system, an ERP, or your own applications. The data is yours. [See a sample report](https://aethair.io/docs/aethair-hq-first-floor-report-example.pdf) Related solutions ## Related Solutions ### [Hydrology, Level & Flow](https://aethair.io/solutions/hydrology/) Flood warning, stream gauging, and groundwater [All solutions](https://aethair.io/solutions/) Questions ## Hydraulic & Fuel Cleanliness FAQ What is the ISO 4406 cleanliness code? ISO 4406 expresses the cleanliness of a hydraulic or lubricating fluid as a code derived from the number of particles above defined size thresholds. It condenses a particle count into a single, comparable rating, so it is the standard way to specify a required cleanliness level and to verify that a fluid meets it. Why monitor filter differential pressure? The pressure drop across a filter rises as it captures contaminant, so differential pressure directly indicates how loaded an element is and when it needs changing. Watching it prevents both premature changes of a serviceable filter and the bypass or damage that a blinded filter causes. In jet-fuel handling it underpins the ATA 103 clean-delivery checks. How does cleanliness monitoring support condition-based maintenance? A continuously logged particle count reveals contamination trends early, so components and filters are serviced when the fluid actually calls for it rather than on a fixed interval. That catches ingress and wear before they cascade into failure, which extends equipment life and avoids unplanned downtime. What is the best setup for fluid cleanliness monitoring? A Thiamis gateway with an inline particle counter reporting the ISO 4406 code, paired with filter differential-pressure sensing and, where relevant, a water sensor, sampling representative fluid downstream of the component of interest. Use the configurator to set up the counter and pressure points for your hydraulic or fuel system.