Dairy Plant Trial Shows Real-Time Oil Detection in Pneumatic Lines

Pneumatic conveying is the backbone of powder transport inside Australian dairy plants. From skim milk powder through to whey protein concentrate, finished product moves from dryers through cyclones, sifters, and packaging lines in runs of stainless tubing, powered entirely by compressed air. In regions such as Gippsland in eastern Victoria and the dairy belts of northern Tasmania, this method dominates because it keeps the product sealed from the surrounding environment and reduces mechanical contact points.

The air driving this process must be exceptionally clean. Even trace amounts of oil carried in aerosol, liquid droplet, or vapour form can settle on powder surfaces, creating off-flavours, blocked sieves, and potential compliance breaches. Australian processors operating under the Australia New Zealand Food Standards Code expect every batch to meet strict compositional limits, so any contamination event triggers a documented investigation.

Conventional oil detection relies on periodic spot checks with portable analysers or laboratory grab samples. These methods miss transient spikes that occur during compressor cycling, filter breakthroughs, or after maintenance work on aftercoolers. The DOCA project was designed to fill that visibility gap with a permanent online optical sensor capable of logging all three contamination states continuously.

This case study follows a six-week deployment of the DOCA optical sensor on the main conveying line of a mid-sized dairy processing facility south of Melbourne. The plant produces around 80 tonnes of milk powder per day and runs continuous shift operations. The aim was to measure the actual oil load reaching the powder during normal production, peak-season campaigns, and planned shutdowns.

How the Trial Was Configured at the Victorian Facility

The sensor head was mounted downstream of the desiccant dryer bank and upstream of the receiving hopper that feeds milk powder into the conveying loop. Sample lines were tapped into a 25-millimetre stainless-steel manifold shared with the plant's existing dew-point probe, so the installation did not require any modification to the conveying pipework. A small control cabinet housing the optical cell was fitted to an adjacent wall, with a 4G telemetry link sending live readings back to the DOCA research team.

During commissioning, the unit was calibrated against zero-air generated from a compressed breathing-grade cylinder, and span-checked using a controlled oil-mist generator. Baseline readings taken over the first 72 hours confirmed the system could resolve oil concentrations down to 0.01 milligrams per cubic metre across all three phase states.

Why Oil Contamination Matters in Dairy Powder Lines

Milk powder is hygroscopic and has a high surface-area-to-mass ratio, which makes it an efficient collector of airborne hydrocarbons. Once oil deposits on a particle, it migrates inward during storage and shows up only when customers run their own sensory or chemical checks. In Australian export markets, that delay can complicate shipments heading to South-East Asia or China, where buyers routinely retest every container.

The sensor data also helped quantify a quieter risk: filter pressure differentials that climb more slowly than expected when oil coats the media. Plant managers in Warrnambool have reported cases where coalescing filters appeared normal until a sudden breakthrough event sent a plume of oil into the conveying air. Continuous measurement gives the maintenance crew a chance to plan change-outs before that point.

Real-Time Behaviour During Skim Milk Powder Production

Across twenty-eight days of operation, the DOCA sensor logged average oil-in-air concentrations of 0.008 milligrams per cubic metre during steady-state production, with short peaks reaching 0.12 milligrams per cubic metre every time the main screw compressor ramped up. Vapour-phase oil contributed roughly 60 percent of the long-term load, while aerosol and liquid contributions dominated during compressor start-up transients.

These transient events had been completely invisible under the previous quarterly sampling regime. Engineering staff now receive an alert when readings cross a configurable threshold, allowing them to throttle valves or sequence equipment in ways that protect the receiving batch. One specific episode during a peak-evaporation run produced a 90-minute excursion that coincided with dryer-regeneration cycles, prompting a procedural change to regeneration timing.

Maintenance Outcomes and Filter Planning

A clear pattern emerged between cumulative oil exposure and filter loading on the downstream coalescing elements. Operators reported that they could predict coalescing filter change-out requirements far more accurately than the calendar-based schedule previously used. This finding aligns with broader industry guidance on the relationship between oil concentration and filter life in compressed air systems, confirming that even modest gains in measurement resolution translate into meaningful maintenance savings.

Predictive change-outs also freed maintenance crews from reactive weekend callouts. With continuous data, many of those events could be traced back to known equipment cycles and resolved through scheduling rather than emergency action, cutting unplanned downtime by an estimated 30 percent over the trial period.

What Australian Processors Should Take From This Trial

The Gippsland trial suggests that permanent optical monitoring is now mature enough for routine use in food-grade compressed-air networks. Adoption paths include greenfield installations in new spray-dryer facilities planned for south-west Victoria and retrofits to existing plants in Adelaide and Perth where audit pressure from major retailers is rising.

Smaller operators in regional hubs such as Toowoomba or Bunbury can also benefit from this approach, particularly where a single bulk-tank receiver feeds multiple product lines and a single contamination event could impact several shifts of production.

Arrange a conversation with the DOCA project team to scope a pilot deployment on your compressed-air line, request a demonstration unit for short-term evaluation, or book a free on-site audit to map where continuous monitoring would deliver the strongest return on investment at your facility.