How to establish a baseline oil level in a new compressed air system

Establishing a baseline oil level in a new compressed air system using the DOCA sensor creates a defensible reference for oil carryover and background contamination. It shows what the installed system produces under defined conditions; it does not replace the customer’s air-quality specification or a validated safety limit.

Start after pressure testing, condensate removal and the manufacturer’s prescribed flushing have finished. DOCA is intended to reveal oil carried in liquid, aerosol and vapour forms, helping identify contamination that a routine compressed-air quality certificate may miss.

For Australian sites, compare the baseline with the specification for the air at the point of use and, where relevant, classes referenced by AS/NZS 4259. Melbourne pharmaceutical and automotive plants, Sydney hospitals, Pilbara mines and regional food processors all have different contamination sources and operating patterns, so one universal threshold is rarely suitable.

Define the reference and its limits

A useful baseline should cover both background conditions and operating peaks. Record no-load, normal production and maximum-demand states because receiver pressure, compressor loading and condensation can change the amount of oil detected. Use the same operating definition whenever the baseline is checked.

Set acceptance criteria before testing, with input from quality assurance, EHS and maintenance teams. If the DOCA output is below its validated detection limit, record it as such rather than inventing a numerical zero. A baseline should identify an unexpected increase against the reference; it should not quietly become a substitute for an established oil-content limit.

Prepare the installation for fair comparison

Complete pressure and leak checks, drain condensate and confirm that filters and dryers are correctly installed and operating. Allow hot compressed air to cool and the system to stabilise at working pressure. Otherwise, changing line temperature and moisture can distort the optical response and make early readings appear worse than steady-state conditions.

Australian installations may combine imported compressor packages with locally supplied dryers, filters and specialist commissioning contractors. This mixed service market makes a joint commissioning record valuable. Ask the fitter who commissioned the equipment, the maintenance supervisor and the process-quality representative to confirm the lubricant type, filter specifications, dryer controls and operating pressure before measurements begin.

Place the sensor where oil can be seen

Map the compressor discharge, dryer outlet, final filter, main header and the most sensitive point of use. Contamination introduced by a flexible hose, fitting or downstream process line will not necessarily be visible at the main header. Position DOCA units at locations that represent both equipment carryover and the air used in production.

The DOCA project’s guidance on aerosol particle size is important here: fine mist and larger droplets can produce different optical responses, while condensation can alter the sample further. Compare the sensor trend with a gravimetric or laboratory oil result rather than assuming that every reading equals total oil mass.

For hospitals, clean rooms and pharmaceutical facilities, include critical outlets rather than relying only on the central supply. For automotive and mining equipment, also examine areas exposed to heat, vibration or maintenance practices that can introduce oil aerosols. The selected location should answer a defined operational question.

Capture repeatable operating data

Each baseline run should record the sampling point, DOCA output, time, pressure, flow, compressor load, temperature and relevant dryer or filter status. Note the instrument identifier and calibration status. Retain raw readings alongside calculated summaries so a later investigator can distinguish a real change from a different test condition.

Repeat each operating state enough times to expose variation, then report the median, range and any isolated excursions. For consequential decisions, seek comparison testing through a NATA-accredited laboratory. In remote Pilbara operations and regional factories, arrange collection logistics early where required, but do not use the distance or delay to accept an unexplained result without further investigation.

Build controls around the baseline

For a new system, the baseline becomes useful when it is tied to routine work:

• Agree the point-of-use oil requirement with quality, EHS and maintenance teams before testing.
• Map the compressor, dryer, final filter, main header and worst-case outlet before choosing sensor positions.
• Run each defined operating state at least three times after the system has stabilised.
• Keep DOCA readings, calibration details, operating logs and laboratory comparisons in one baseline register.
• Rebaseline after changes to lubricants, filters, dryers, controls or pipework, and following abnormal oil events.

Treat an alarm as the start of an investigation rather than automatic proof of equipment failure. Check whether the increase is confined to one outlet, appears across the header or follows a compressor or filter change. When a fitter says the plant air is back to normal, the baseline gives that statement a measurable reference and helps prevent unnecessary shutdowns.

Schedule a joint walkdown with the commissioning contractor, maintenance crew and DOCA technical team. Map the sampling points, define the operating states and establish the baseline register before handover or full production. That shared record gives the site a clear starting point for detecting oil carryover, maintaining compressed-air quality and responding to changes quickly.