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CTP-S-012 · Vacuum extraction

Drop-tube vacuum sampling

Lowers new tubing through a fill or dipstick opening to a controlled depth and draws oil with a vacuum pump.

Suitable applications

Use this method when the access point supports the evidence required.

  • Engines
  • Gear systems
  • Hydraulic reservoirs
  • Compressors and large circulating sumps without ports
Limitations to control

Recognise what can bias the result.

  • Tube depth is operator-dependent
  • Bottom contact collects sludge
  • Open access increases environmental contamination risk
Before approaching the asset

Materials and preparation.

Use laboratory-specified containers and clean dedicated accessories. Keep the cap, bottle mouth and tubing ends protected throughout the collection.

  • 01Vacuum sampling pump
  • 02New clean tubing long enough for the defined depth
  • 03Flush and sample bottles
  • 04Clean cutting tool, labels and PPE
Controlled method

Field procedure and evidence protected.

Perform the sequence consistently. If a step cannot be followed, record the deviation because it may explain an apparent trend change.

  1. 01

    Stabilise the operating condition

    Collect during normal representative operation or, where the approved procedure requires shutdown, within 10 minutes. Record cold or non-standard sampling conditions.

  2. 02

    Verify the asset and decision point

    Confirm machine, compartment, lubricant, sample-point identity and the maintenance question before opening the kit.

  3. 03

    Prepare clean equipment and records

    Use the laboratory-specified bottle, labels, clean adapters or new tubing, a separate flushing container and the required PPE. Keep caps and bottle mouths protected.

  4. 04

    Inspect and clean the sampling point

    Remove the dust cover, check for blockage or damage and clean the external point without pushing dirt into the system.

  5. 05

    Set and mark the tube depth

    Use equipment dimensions to reach a consistent mid-zone, commonly about half the fluid depth, without touching the bottom or walls.

  6. 06

    Cut a clean pump end

    Keep tubing bagged until use, cut the pump end at approximately 45 degrees and do not touch either wetted end.

  7. 07

    Insert into the active zone

    Clean the access opening and lower the tube to the marked depth without scraping dirty surfaces.

  8. 08

    Flush the new tube

    Draw approximately 100 mL or the approved tube-volume multiple into the flushing bottle.

  9. 09

    Fill, withdraw and discard

    Change to the sample bottle, draw upright, remove the tube after capping and discard the used tube. Never return it to the clean supply.

  10. 10

    Fill without contaminating the bottle

    Keep the bottle upright and avoid contact with the bottle mouth. Leave suitable headspace; the source guide uses approximately one-half full above 150 cSt, two-thirds for 68-150 cSt and three-fourths below 68 cSt at 40 C unless the laboratory specifies otherwise.

  11. 11

    Cap, clean and restore

    Seal the bottle immediately, wipe the exterior, replace the port cover and return valves, bypasses and filtration equipment to the approved operating state.

  12. 12

    Document and dispatch

    Record asset and oil hours, top-up, filter or maintenance events, operating abnormalities, point, date and sampler. Package securely and send to the laboratory promptly.

Diagnostic quality control

Interferences, effects and controls.

A result may be analytically correct and still misrepresent the machine. Review these controls before escalating maintenance.

Drop-tube vacuum sampling sampling interferences
Interference sourcePossible effect on resultField control
Inadequate flushingOld fluid, settled debris or contamination in the adapter and dead volume can dominate the bottle.Calculate dead volume and flush the required multiple into a separate container before filling the sample bottle.
Changing sample locationA clean downstream point, reservoir surface and active return line represent different particle populations.Use the same labelled point and operating state for each trend sample.
Dirty bottle, cap, tubing or adapterAdded particles, water or residue can create false contamination alarms.Use laboratory-specified containers, protect openings and use new or verified-clean wetted parts.
Settling or particle fly-byLow-velocity zones can under-report settled material while poorly located high-velocity ports can miss the target population.Select a turbulent, representative zone and document whether the objective is machine, filter or reservoir condition.
Safety controls

Complete the task without creating a new hazard.

  • Follow plant, OEM and permit-to-work requirements; the website does not authorise a sampling point or override site procedures.
  • Confirm lubricant temperature and pressure before sampling. Use engineered pressure reduction and thermal protection where required.
  • Wear eye and hand protection compatible with the lubricant and process hazards.
  • Declare hazardous, toxic, flammable, biologically active or process-contaminated samples to the laboratory before shipment.
  • Clean skin exposure promptly and follow site medical procedures for eye contact, ingestion or injection injury.
Source download

Retain the original field reference.

Complete manual, pages 38-42

Download source PDFReturn to all sampling procedures →