Katie Woodward, March 14th, 2014
As maintenance personnel from many industries will attest, an unexpected equipment failure that compromises production and cash flow is one of the worst nightmares a company must deal with.
Typically, preventative and predictive maintenance programs are designed, and evolve over time to accommodate failures that are experienced through the normal operation of a given site. In some cases, usually where there are several rotating pieces of equipment, operators spend a great deal of time monitoring vibrations, checking alignments and making sure that the high friction points are adequately lubricated.
The lubrication of bearings, shafts and other components is an essential component to manage friction-related losses and failures. Operators of rolling equipment in plants must apply lubricants to all high-wear areas on a regular basis as part of their maintenance programs.
But what about equipment that requires ongoing lubrication but is inaccessible because it is under several hundred feet of water or is in a hostile environment?
Some pumps, such as those found in underground mining operations or submerged in tailings ponds, may require different types of lubrication due to the fact that they are located in extremely brutal conditions; but they are still subject to friction-related failures.
In these instances, a reliable solution is needed.
Recently, a producer in Western Canada’s Oil Sands faced this very problem. The company needed to inject precise amounts of grease - 0.2 cc’s at a time - into the skirt seal of a centrifugal tailings pump located in 250 ft of water in order to meet the manufacturer’s operating specifications and warranty requirements.
A simple mathematical calculation shows that the pump in question could be subjected to a static head of more than 8 atmospheres; in order to deliver grease to the seal on the shaft, the lubrication systems must overcome both the static head and the frictional losses associated with pumping grease through about 100 m of delivery line.
In addition, after the delivery pressures are managed in a repeatable manner, the lubrication system must be able to deliver the manufacturer’s specified 0.2 cc of grease into the skirt seal on a scheduled basis. This is a challenge on dry land, and is even more challenging when one cannot see the pump or how the grease is going into the skirt seal.
Once these peripheral issues have been addressed, it is now a matter of developing the control software so that the operator can rely on repeatable performance for many years of reliable service. By removing the human element from this maintenance cycle, the user of an automated grease-dispensing system (AGS) does not have to be overly concerned with having to rely on the operator to do more than ensure that the lubricant reservoirs in the AGS are kept full - and even this is monitored and prompted.
Although the above steps are very complicated (you would be surprised how difficult it is to consistently deliver 0.2 cc’s of grease through a 100-m line) the end result inspires a great deal of confidence in the AGS because once it is programmed, it performs the same tasks repeatedly and reliably.
Further preventative maintenance measures designed into the AGS focus on predicting when its components need servicing or replacement. A Health Monitoring System continuously checks the pumps, computers and even the reservoir grease levels; it even goes so far as to warn the operator immediately about any deviation from the norm, which might signal a pumping problem, or an expensive failure. Nobody wants that - ever.
Failures can be costly, inconvenient and potentially hazardous to the health of a worker who happens to be in the wrong place, at the wrong time. Rotating equipment failures are typically progressive and there is usually a deviation from the normal operating conditions that precedes a failure. The sensing systems association with an AGS can detect these and raise alarms.
As an example, consider a slurry pump running in series with a number of other 5000 horsepower tailings transport system pumps. Now envisage a lubrication related bearing failure and consider what happens: the water hammer effect is nothing short of spectacular as the remaining pumps try to force slurry through a seized unit.
Something has to give as the pressure behind the sized pump spikes, and it does. The pump casing shatters or its flanges fail and an uncomfortable flow of slurry fills the 1500 m2 pump house to a depth of 2 m. All of this happens in less than 30 seconds, prior to emergency shut downs coming into play.
The result is a colossal mess. Production stops dead on the line, and not only does ops have to replace a very expensive casing, but a number of man hours are now dedicated to cleaning up a huge, localized slurry spill. All of this could have been avoided had proper care been taken to lubricate bearings in a more consistent manner.
Fortunately today, as technology rapidly develops, these types of problems can be mitigated in a manner which reduces stress on operators and on equipment. The need to monitor pumps, bearings and lubrication programs the ‘old fashioned way’ can be greatly reduced by automating the activity. This automation in fact increases the operators’ ability to watch more pumps, bearings and other components by removing the amount of time workers must spend at lubricating multiple locations.
Further benefit is derived to the owner because the operator can immediately identify any type of problem regarding lubrication delivery by simply interrogating the AGS, and if necessary, shutting down the piece of equipment prior to catastrophic failure.
As a company, we embrace technology and the new ways it enables us to provide creative, and reliable, solutions to our clients. For all we know, there could be other benefits to systems such as the AGS that we have yet to discover.
Andrew Weir-Jones is the Operations Manager for Weir-Jones Engineering Consultants, a Vancouver, Canada company that has been providing unique solutions for Oil Sands producers, and around the world, for more than 42 years.