Oil from offshore cranes is frequently contaminated with micro-organisms (fungus, yeast and/or bacteria), and it is common knowledge that such organisms may cause malfunction and breakdown of offshore cranes. Less well known is that some of these bacteria may constitute a hazard to human health. That is why it is important to establish not only the presence of bacteria, but also to determine the type.
Having analysed 250 DNA samples, Fras has discovered around 85 different types of bacteria, both in lubricating oil and hydraulic oil. Research from the Agricultural University of Norway confirms the existence of other types of fungus and yeast in oil from the same installations.
Micro-organisms cause a range of problems to machinery. They produce bio film that sticks to the surface as slime. Jets and clearances performing vital hydraulic functions are clogged and the hydrocarbons in the oil are broken down, causing degradation of lubricating quality and of viscosity. Some bacteria are also acid producers, causing corrosion on metal surfaces.
Bacteria identified in cranesAll of the most commonly known types of bio film producing bacteria have been identified in machine installations in the North Sea such as cranes, thrusters, gas turbines, loading/unloading systems, etc. Among these are Pseudomonas and Sphingomonas, which can cause urinary tract infections, respiratory system infections, septicaemia, dermatitis, soft tissue infections, bone and joint infections, and gastrointestinal infections.
But, to what extent are bacteria the primary cause of malfunctions? We believe that mechanical contamination of oil is playing a less significant role than it used to, and machinery malfunction caused by micro-organisms is increasing. This theory is supported by the fact that there have been malfunctions on machine installations where the oil satisfied a NAS class 4 level (NAS1638 standard) and simultaneously having a moisture level down to 200ppm water.
These readings are equivalent to what one would usually expect to find in advanced aircraft hydraulic systems. However, the very same hydraulic oil was contaminated with Pseudomonas, and in the machinery we found that clearances and pressure balancing grooves on the control jets were clogged by bio film, causing the blocking of vital safety functions.
Even though we frequently identify pathogenic bacteria in oil as posing a potential health hazard to humans, it is difficult to determine the level of risk. This should not, however, lead us to believe that oil contaminated with bacteria can be handled without any risk at all. There are, however, ways to reduce this risk.
Hand protection: Many workers dealing with mechanical maintenance regard oil on their hands as inevitable. We are putting behind us a period where the use of additives in oil was increasing to improve oil properties and to protect against contamination by micro-organisms.
Protective measures should therefore protect against both chemical and microbial influence. Protective cream and /or disposable gloves should always be used. They are thin and elastic and can be used for most kind of mechanical work.
Protection of the alimentary canal: Even though oil has become more environmentally friendly over the years it is still potentially poisonous, so it is important to follow basic hygiene practice. For example, never use toothpicks, or eat food unless hands have been thoroughly washed after being in contact with oil or oily objects/tools.
Handling a cigarette with oily fingers is another way of being exposed to micro-organisms, either directly to the lips or small drops of oil being infected by bacteria entering the bronchia or being swallowed.
Eye protection: It is important to protect the eyes from oil squirts, not only because of the harmful consequences caused by a pressurised beam, but also against the chemical contents and possible bacteria. Special protection glasses should therefore always be worn.
Build-up of aerosols: When samples are retrieved from a pressurised system by means of ‘open sampling’ (samples being bottled directly from an in-line crane or valve), a considerable pressure drop will occur over the valve seat as the oil is flowing into the bottle having an atmospheric pressure. The larger the drop in pressure, the larger the vaporisation or building of aerosols out of the (open) bottle.
Aerosols are divided into three classes according to size, as follows:
* Ultra fine particles – aerosols having a diameter <0.1mml PM 2.5, which includes aerosols with a diameter from 0.1mm to 2.5mml PM 10, aerosols with a diameter from 2.5mm to 10mm. PM 2.5 and PM10 may be inhaled further down into the respiratory system than the mouth or nose region. Bacteria and viruses fall under aerosol class PM2.5, so they may be inhaled into the lungs, while fungus spores and yeast cells belong to class PM10, and may be inhaled into the tracheobronchical area.
This is why it is important to ensure that oil tanks are fitted with a breathing filter, preferably of the oil-bath type. Systems with large pendulums – for example, crane installations with large cylinders – should be equipped with breathing filters capable of managing the large volume of air/pendulum volume that is passing through the filter (see also CT, November, pages 37 and 39).
Over pressurise the tankIf possible, the tank should be over pressurised with instrument air. The use of a rubber expansion bladder or a dividing membrane between air and oil in the tank could protect the system from intrusion by air and reduce foaming and emission of oil vapour to the surroundings.
Space with a lot of oil vapour or atomised oil should be thoroughly ventilated and human presence in such facilities should be reduced to a absolute minimum. Respiratory protective equipment should be used if necessary.Removing free and dissolved water from hydraulic or lube oil systems requires vaporisers, vacuum or absorption filters. An absorption filter is made up of materials that absorb the water until saturated, and then it must be replaced. This is an expensive method if the quantity of water to be removed is large.
Additionally, this kind of filter method is not as effective as the use of vacuum purifying systems. On the other hand, filtering methods are not generating oil mist, as are (usually) vacuum purifiers. The latter systems should therefore not be used in an enclosed space such as inside machine rooms, and offshore platform legs. If used, proper ventilation must be provided for and the drying unit should be shielded off to prevent inhalation of vapour/aerosols that will be found dispersed in the air.
Respiratory protection equipment (RPE) should used whenever working in an environment where the air contains amounts of oil vapour/atomised oil. If the working environment entails regular exposure to oil mist, RPE should always be used.
The same rule should apply if breakage of pipelines or leakage from hoses inside an enclosed space occur. If possible such space should not be entered before the mist has settled. Even then, RPE should be used. If an accident occurs, it is useful to have advance knowledge of whether the oil involved may contain any pathogen bacteria. Special attention should be paid to systems/installations with a large number of hoses or potential leakage points. Oil sampling and analyses should be carried out regularly, to include DNA-analyses to establish if pathogen micro-organisms are present or not.
Microbial growth in tanks, pipelines, or in an enclosed space may create poisonous gases, some of which are lethal. Before entering such a space, or opening inspection hatches or machinery, a gas detector should be employed to establish the presence or otherwise of dangerous gases. Not all of these gases can be seen or smelled.The use of inspection equipment like a video scope and other remotely controlled remedies that reduce the need for physical access to a system lead to increased safety to personnel directly involved in such operations.
