Measure your maintenance

Audits offer a clear picture of your strengths and weaknesses

04/11/2011


In recent decades your company has likely progressed from run-to-failure maintenance practices to enterprise-wide predictive and preventive maintenance, complete with advanced systems for everything from monitoring equipment condition to analyzing and sharing collected knowledge. So what’s next?

One emerging process is the maintenance audit.

Briefly, a maintenance audit consists of a consulting firm or technology company evaluating existing maintenance practices and then producing a recommendation for upgrading its customer’s technology and tools, and providing training. It’s a way to refine a plant’s maintenance program for purposes of efficiency and increased productivity.

Maintenance audits for rotating equipment and components, for example, concentrate on areas such as energy consumption, lubrication, component mounting and dismounting, the use of the right tools and safety. At nearly any industrial plant, each area will offer potential for improvement.

Typically, an audit will begin with a series of questions directed to the plant manager, process engineers and other appropriate parties who are familiar with plant operations. The questions are designed to uncover overlooked opportunities.

Consider energy consumption. Prospects for reducing energy consumption abound but often go unaddressed until they are specifically targeted for improvement. For example, reminders to “turn the lights out” when vacating an empty room are standard fare. But how much attention is given to wasted energy within the operation of your air conditioning system’s compressor? An audit will likely pose that question.

A plant audit might also ask about the operating efficiency of industrial fans, blowers and virtually every piece of equipment with moving parts. Are bearings lubricated properly, with the optimum amount and the right type of grease? Are bearings, seals and shafts properly aligned? Are energy efficient means being employed to heat large components for mounting onto a shaft?

Such questions lead to solutions. Take bearing lubrication in fans, blowers and compressors, which are typically lubed with grease. Too much grease causes a phenomenon called churning, where a bearing’s rolling elements must work harder for each revolution. That extra work translates to wasted energy.

An audit’s energy consumption recommendation might suggest the use of grease meters for companies that employ manual re-lubrication. Grease meters, which can be connected either to electrically driven or hand-operated grease guns, will help prevent over- or under-greasing by accurately measuring refill amounts.  

For larger operations and lube locations that are not readily accessible, single and multi-point automatic lubricators exist that keep bearings filled with precise amounts of lubricant. More on automatic lubricators later.

Shafts and bearings

Shaft and belt misalignment are conditions that can increase manufacturing equipment energy usage as much as three percent. Industry estimates report that perhaps 90% of machines are running beyond their recommended alignment tolerances. Fortunately, shaft and belt alignment technology has reached the stage where alignment is fast, precise and requires little operator training.

Shaft alignment laser-guided tools, for example, consist of two units, each of which emits a precise laser beam and detects a laser beam from its opposite number, plus a hand-held control device. The units mount to a shaft via magnetic brackets or chain. New laser-guided belt-alignment tools consist of a laser emitting unit and a 3D receiver, which also attach magnetically.

Other valuable alignment tools include hand-held instruments that deliver an overall velocity vibration reading and a new generation of stroboscopes. The hand-held instrument’s reading measures vibration signals and compares them with pre-programmed ISO guidelines. Alerts activate when measurements exceed the guidelines.

The stroboscopes enable users to gauge rotational speed and examine moving parts, such as belts and pulleys, as though they were stationary. Signs of misalignment include worn belts and operating speeds that are slower than previously recorded speeds.

Both shaft and belt alignment checks are recommended in conditions of high vibration, high operating temperature or excessive noise, which are primary misalignment symptoms.

Lubrication

Lubrication practices affect equipment reliability, productivity and employee safety. A lubrication audit examines the type and amount of lubricant, as well as the current re-lubrication method, at each lubricant position in a plant.

More than 80% of industrial equipment is lubricated with grease. Often, smaller plants will use a single, all-purpose grease for nearly every application. While this practice is generally acceptable, certain applications, such as those with high operating temperatures or high pressure conditions, call for specialized greases. Greases produced to meet specific requirements often prolong re-lubrication intervals and can greatly reduce grease consumption.

Such savings affect not only lubricant purchase costs, but also reduce lubricant disposal expenses. For every one dollar spent on lubricant purchase, three dollars are spent on its disposal. Conservation therefore can yield significant savings.

 Automatic lubricators can help dramatically control lubricant usage. One Midwest food producer reports lubricant usage savings exceeding $120,000 per year by having changed from manual to single-point automatic lubrication devices. The lubricators consist of electro-mechanically-driven canisters capable of holding 250 milliliters of grease. They deliver precise amounts of the lubricant directly to a machine point.

Multi-point automatic lubricators consist of up to eight feed lines, each up to 16 ft. long. The systems are recommended for applications such as hot gas fans and calendar rolls in paper mills, where manual lubrication could present safety challenges. The lubricators can dispense from 0.1 to 10 cubic centimeters of lubricant to each machine point daily.

Safety

Rotating machinery safety audits look at a plant’s monitoring, inspection and installation practices.  Recent advancements in maintenance tool technology include safer devices for detecting signs of impending equipment failure and for installing and removing rotating components. An audit will help determine when and where the new technology can best support your maintenance program.

Detecting electrical erosion in motors is one likely example. Until recently, detecting electrical erosion called for direct contact probes handled by experienced technicians. New generation electrical erosion detectors allow users to hold the detector roughly 12 inches from an operating motor. The device safely monitors electrical pulses and then displays the count on an integrated screen. The motor can be replaced prior to failure when the detector identifies excessive electrical erosion.

Advancements in stroboscopes and thermography can further contribute to workplace safety. Thermography, which has become more affordable in recent years, detects radiated energy in a spectrum’s thermal band. Thermal cameras allow users to monitor equipment that is positioned in unreachable or dangerous locations. Images of “hot spots” can be uploaded to a computer for detailed analysis.

Stroboscopes allow users to observe belts, pulleys, fans and gears in motion from a safe distance. In operation, they “freeze” a component’s movement, allowing for visual inspection without shutting down the machine.

Installation, removal and tools

Improper bearing installation can lead to premature equipment failure. A case in point: A major manufacturer of high quality gearboxes was experiencing excessive returns under warranty due to bearing failure. The gearbox producer called for the technical services of the bearing manufacturer, which soon identified the root cause of the problem as improper bearing installation.

The bearings company assigned a training specialist to prepare and conduct a bearing installation course for assembly workers. The program included equipping the facility with appropriate installation tools. The result: warranty claims for gearboxes returned to their previous low level.

The scenario illustrates the type of process, in this case bearing installation, that an audit can identify and then correct via training and new tools.

Worth noting are some important developments in bearing installation and removal technology. Among them are large energy efficient and safe induction hearers. The heaters replace oil baths, which have the potential for oil spill-related safety hazards. More, the energy efficient heaters reduce energy consumption associated with oil baths.

Bearing removal technology includes hydraulic systems that force oil between a bearing and its shaft to break an interference fit. When the bearing breaks free, a stopper keeps the bearing safely on the shaft for removal.

The audit report

One aspect of a plant audit that is sure to catch the attention of upper management is the audit report.

Typically, an audit report, prepared by the consultant or technology firm that conducted the audit, will include a list of items that can be prioritized based on their potential for return on investment. It should also include goals for improvement that match up against established industry standards.

A paper mill, for example, might see that it currently ranks in the bottom tenth percentile of energy efficiency among all North American paper producers. A goal, then, might be to reach the 50th percentile mark after one year of implementing an energy consumption improvement program.

The audit report will go on to explain how to improve each specific area that has been audited through the use of revised procedures, proper tooling and training. Corresponding ROI figures in terms of dollars expected to be saved will accompany each targeted area.