DOCA sensor integration in a textile mill air knife system

A textile mill relies on compressed air for fast, even fabric drying after washing, dyeing or coating. In this case study, the DOCA sensor is integrated into an air knife system to monitor oil contamination before it can mark fabric, affect colour consistency or compromise downstream finishing.

The example reflects conditions relevant to Australian manufacturers, including mills operating around Melbourne, Sydney and Brisbane. It considers the practical demands of an industrial compressed-air network, the need to reduce production waste, and the importance of maintaining documented controls under Australian workplace health and safety expectations.

The mill’s drying challenge

The mill receives fabric from a wet processing line and passes it through an air knife chamber. High-velocity compressed air removes surface moisture and helps prepare the material for stentering, calendaring or final inspection. Even a small amount of compressor oil can create visible spots, uneven absorbency or odour on sensitive fabric.

The site uses an oil-injected compressor because it provides reliable capacity at a competitive operating cost. Filtration and a refrigerated dryer are already installed, but filter performance can change with load, temperature and maintenance condition. In a warm Queensland summer or a dusty industrial setting, these variables can place additional pressure on the air treatment system.

How contamination can reach the fabric

Oil contamination may travel through compressed air as liquid droplets, aerosols or vapour. Conventional checks often rely on periodic sampling, laboratory analysis or filter replacement schedules. These methods can identify a problem after it has developed, but they may not show when contamination first begins to rise during normal production.

The air knife is particularly sensitive because it distributes air directly across a broad fabric surface. A fault upstream can therefore affect hundreds of metres of material before operators recognise the pattern. A continuous optical measurement provides an opportunity to identify changes in oil concentration while the line is operating.

Positioning the DOCA sensor

For the integration, the sensor is installed on a representative branch of the treated-air line supplying the air knife. The sample point is selected downstream of the main filtration stages and close enough to the application point to reflect the air actually reaching the fabric. Proper isolation, drainage and flow control allow the sensor to be serviced without shutting down the entire mill.

The DOCA technology is designed for online detection of oil contaminants in high-purity compressed air. Its optical approach supports monitoring across liquid, aerosol and vapour forms, helping the mill create a more complete picture than a single visual inspection or filter differential-pressure reading can provide.

Commissioning the monitoring system

Commissioning begins with a clean-air baseline under normal air knife pressure and flow. Operators record compressor status, dryer operation, filter differential pressure, line temperature and production speed. The baseline is then compared with readings taken during start-up, peak demand and planned filter loading.

Alarm limits are set in consultation with the mill’s quality and engineering teams. A warning can prompt an inspection of the compressor, coalescing filters or condensate drains, while a higher-level alarm can hold affected fabric for investigation. Integrating the sensor signal with the plant’s control or supervisory system gives operators a visible trend rather than an isolated test result.

Using data during production

The value of the installation comes from linking contamination readings with production events. A gradual increase after a filter change may indicate incorrect installation or premature loading. A short spike during compressor changeover may point to carryover, while a stable reading during a difficult production run can confirm that the treatment train is performing as intended.

The mill can also correlate sensor data with fabric inspection records, rework, rejected rolls and customer complaints. This supports a more precise root-cause investigation. Instead of treating every mark as a textile-process fault, the team can distinguish between dye chemistry, mechanical contact, moisture imbalance and compressed-air quality.

Benefits for an Australian textile operation

For an Australian mill, reducing one contaminated batch can have a meaningful commercial effect. Imported fibres, specialised finishes and long customer supply chains can make replacement material expensive and slow to obtain. Reliable online monitoring helps protect production schedules while reducing unnecessary disposal, reprocessing and emergency maintenance.

The system also supports a documented risk-management approach. Australian workplaces must manage risks under applicable state or territory work health and safety legislation, while air quality specifications can be referenced against ISO 8573-1. The sensor does not replace formal validation or laboratory testing, but it strengthens routine control and provides evidence for internal audits and customer assurance.

Practical deployment recommendations

The integration works best when the sensor is treated as part of the mill’s quality system rather than as a stand-alone instrument. Clear ownership should be assigned for alarm response, calibration, data review and maintenance of upstream air treatment equipment.

A practical operating model includes:

• Select a sample point that represents air delivered to the air knife, not merely air leaving the compressor.
• Record compressor, dryer, filter and production conditions beside every significant sensor event.
• Set staged alarms so operators can investigate rising contamination before fabric is affected.
• Use isolation valves, drainage and safe access to support maintenance without disrupting the whole line.
• Compare online trends with periodic verification testing and finished-fabric inspection.
• Train production, maintenance and quality teams to follow the same response procedure.

From pilot installation to wider adoption

After the initial air knife trial, the mill can assess whether similar monitoring is useful on coating, spraying, instrumentation or clean finishing lines. Results from the pilot can support a business case based on avoided waste, fewer customer claims, better maintenance planning and improved confidence in compressed-air quality.

The project also illustrates how European research and development can translate into practical industrial protection. By combining optical sensing, process data and disciplined operating procedures, textile manufacturers can gain earlier visibility of contamination risks without relying solely on occasional sampling.

Contact the DOCA Project to discuss sensor integration, application requirements and the role of online oil monitoring in high-purity compressed-air systems.