By Garry Sands
Most companies rely on outside laboratories to analyze there time-based oil samples. Every six months, or perhaps once per year, oil samples are gathered and sent out for routine time-based analysis. So, for instance, we will be able to say a certain hydraulic reservoir has been sampled every six months, or once yearly, and then we at least know the condition of the oil at that point in time.
But is this enough? Can we really feel comfortable about knowing what condition our oil is in only once or twice a year? Let’s not forget, this sample also reflects the condition of our equipment. A false sense of security or feeling comfortable about the condition of our oil and equipment may exist when using only this method of testing. We have a feeling of everything being under control, but is it?
For the most part, barring any changes to the environment, the operation of the equipment, or any changes to the oil in general, this might be sufficient. In an ideal world, it may seem like nothing is wrong with scheduled oil sampling of this nature.
However, it is not an ideal world that our equipment runs in, now, is it? In the real world there is what I call “accelerants.” What are accelerants? Accelerants are anything that can enter your lubrication system and stop the lubricant from doing its job prematurely. This may happen over a long period of time, allowing us to react, but usually not. Accelerants can take over in a fairly short period of time. Now we only have a short period of time to react.
When considering all the contaminants that are seemingly just waiting in line to enter our lubrication systems, we need to be ready to react. Even at six-month sampling,we are putting ourselves at a disadvantage.
Water can cause catastrophic failure in a matter of only hours. Failed seal, failed heat exchanger, or even an overzealous hose down can cause nightmares for a PM department.
Heat is another accelerant. Lower viscosity can lead to a lack-of-lubrication failure. Rapid oxidation caused by high heat can break down the additive package. The additives such as extreme pressure, antiwear, demulsifiers, antifoaming agents, and others can no longer protect. If unchecked, three-body wear begins, rapid wear starts and this can speed the process of failure exponentially.
Ingression of dirt through a failed breather is a common occurrence. Soot, fine windblown sand, or anything else usually transported through the air qualifies as dirt. It is the abrasiveness of this dirt that continually wears on all parts and clogs filters.
So, we can see all that is waiting to enter a hydraulic system, gearbox or bearing unit. It can be challenging to know at all times, the condition our oil is in. Is it clean? Is it dry? Is there any reason at all I should be concerned about premature failure? We need to be able to say yes or no to these questions as often as possible.
Of course, there needs to be a balance in the amount of effort and expense we put forth to stay on top of things. For instance we would not require a sample taken from a power end containing one gallon of oil be sent for analysis every month. Conversely, we would not allow a complicated, high-cost, money-saving, critical hydraulic lubrication system to go unchecked for an entire year.
So let us focus on what we need to know and when we need to know this valuable information.
First of all, one of the main reasons to have a daily lubrication inspection route is to spot, identify, report, and correct any changes developing on our equipment. The oil level and condition of that oil should be one of the first things we look for. Pumps make up much of the equipment on our daily route. Today, many if not all of these power ends are fitted with BS&W sight glasses. Most contaminants sink to the bottom of oil reservoirs rather fast when able to get out of the agitation zone. These sight glasses are in fact an oil sample bottle and can be checked for contamination at a glance. Side level sight glasses can provide a window into the condition of the oil as well, but it may take more time to determine the severity. This type of sampling is visual only, but very effective, taking no more time than checking levels.
The cost of replacing equipment goes up when we move on to gearboxes, both small and large. They are a bit more complicated than housings containing a shaft and two bearings. With a lot more going on in these housings, the condition of the lubricant can either maintain reliability or shorten it in a hurry.
Small gearboxes make it difficult to monitor the condition of oil due to the lack of room available for mounting accessories. A small gearbox containing less than eight gallons of oil could be put on a time-based oil change. Caution needs to be taken when trying to determine the correct length of time permitted between oil changes. The equipment’s environment plays a big part in this decision, and environments can change daily. Now here is where the experienced lubrication technician earns his or her money. Knowing what is going on around a specific piece of equipment can give a good idea as to what is going on inside that equipment. Checking a dipstick or fill plug can shed some light on the condition of the oil. The lube tech can then plan for and execute a condition-based oil change while referring to a time-based oil change as a backup system and reminder.
It can actually be easier to monitor the oil condition in large gearboxes because accessories can be installed as tools for monitoring. More space is usually found around these units to accommodate valves, bottom sediment, and water sight glasses. Sample tubes or ports to pull oil from the unit for in-house or outside analysis to be performed are a must.
Hydraulic units require very clean lubricating oil. Sample ports can easily be used at various locations. Standard practice for oil sampling with outside laboratories once or twice per year may be good enough. But does it give us enough time to react? This is where in-house oil sample analysis can fill in the gaps.
With an inexpensive microscope, having 40 to 60 power magnification is all that is needed to identify or at least give us a good idea as to what is in our oil. A patch test kit with a vacuum pump that can double as a sample extraction pump completes the kit for particle identification. Monthly oil sampling with the ability to correct any anomalies with off-line filtration is a winning combination. Filter carts are considered a must-have to maintain cleanliness levels of your choice and can also absorb a modest amount of dissolved water with the use of desiccant filters.
Water saturation testing is a test needed to be sure our oil is and remains dry. Portable water sensors are certainly more expensive but the cost is easily justified in a very short period of time. Changing oil need not be the only solution. Consider the cost of new oil, added to the cost associated with the disposal of used oil, only to find out in two weeks your back to square one. Vacuum dehydrators, air strippers, or centrifuges can be purchased or rented and in a very short period of time can pay for themselves.
Outside oil analysis performed annually is, of course, better than no analysis at all. Today our equipment is running faster with closer tolerances, so it stands to reason we need to know, not guess, at what is in our lubricating systems. In-house oil analysis performed often with outside laboratories confirming or eliminating our suspicions seems, to me, to be the best way to go.