Quality sampling is the basis for any decisions based on oil analysis. Taking a sample is not difficult, but don’t make these mistakes. Following this process will ensure you draw a representative sample from the compartment.
How to use vacuum extraction to take a sample
This sampling method requires a Vacuum Pump. These are widely available from equipment suppliers, aftermarket equipment retailers and online. Use the vacuum pump method for pressurized systems not equipped with sampling valves, or where local safety requirements result in the machine being isolated prior to boarding.
It is important to use a new piece of tubing after each sample is drawn. Oil and contamination may remain in the tubing and contaminate following samples. Ask your sample bottle vendor or laboratory to supply pre-cut lengths of tube sealed in bags with each bottle. Alternatively, stock bulk rolls of vacuum tubing in your workshop or store in a clean area.
Step 1 – Preparing equipment
Shut down the engine. Mark some clean tubing to the length of the dipstick. Add sufficient tube to allow safe access and sampling as both hands will be on the vacuum pump. Check the pump head is clean and dry.
Step 2 – Preparing the tube
Insert the tubing through the head of the vacuum pump and tighten the retaining nut. The tubing should extend about 2.5 cm (1 in) beyond the base of the vacuum pump head.
Step 3 – Installing the bottle
Screw a new sampling bottle onto the vacuum pump and insert the end of the tubing into the oil. Do not allow the tubing to touch the bottom of the compartment. If this happens, the end of the tube could be contaminated with sediment on the base of the compartment. Remove the tube and discard it and repeat Step 2 with some new, clean tube.
Step 4 – Drawing the sample
Pump the vacuum pump handle to create a vacuum. Hold the pump upright. If you turn it over, oil may contaminate the pump. If oil enters the pump, disassemble and clean it after taking the sample and ensure the pump head is clean and dry before taking the next sample.
Step 5 – Sealing the sample
Fill the bottle around three-quarters full. Remove the bottle from the vacuum pump and secure the cap on the bottle. Withdraw the tubing from the compartment. Loosen the nut on the pump head and push another the tube 10 cm (4 in) in the direction of the bottle. Cut a clean area of tube under the vacuum head to discard the wet tube and then withdraw the clean tube from the vacuum head. This process minimises the chance of contaminating the head when withdrawing the tube. Place the bottle with the completed label into the shipping cylinder.
Do not use the vacuum pump used for oil samples to draw coolant samples. Although the fluid should not enter the barrel of the pump, glycol residue from a coolant sample can cause a false positive” in oil samples taken later with the same pump. Using a separate dedicated pump for coolant samples.
How to use live sampling to take a sample
This sampling method requires a probe and approximately 15 cm (6 in) of new, clean tubing. Use a new piece of tubing for each compartment.
Step 1 – Preparing the equipment
Set the engine at low idle and secure the machine against unintended movement. Remove the dust cap from the valve of the compartment being sampling.
Step 2 – Flushing the valve
Insert the probe into the valve and collect about 100 ml (4 fl oz) of oil into a waste container. If the oil flow is slow at low idle, it may be necessary to have someone accelerate the engine to high idle while extracting the sample. Dispose of the waste oil properly. This process flushes any contamination from the sampling valve.
Step 3 – Drawing the sample
Insert the probe into the valve again and fill the sample bottle around three-quarters full.
Step 4 – Sealing the sample
Withdraw the probe from the valve and secure the bottle cap. Place the bottle with the completed label into the shipping cylinder. Discard the plastic tube.
Filling out the sample label
To ensure accurate sample results, supply all the information requested for each machine compartment. Model, serial number, and service meter units on both equipment and oil are important.
Fill out the sample label information before you begin taking samples to keep the label oil-free and easy to read.