Your Reliability Engineering Professional Development Site
Historically numbers have been used to represent the work type.
As numbers are not a universal human method of description, the work type is also described using words.
The proper choice of words is critical if classification errors are to be minimized.
Keywords: CMMS, computerized maintenance system, breakdown, corrective, work order, implementation. [Read more…]
When spares cannot be purchased easily it becomes necessary to manufacture your own.
Local fabricators, foundries and machine shops can often make the item if you provide them with a design and specification.
Keywords: casting, reverse engineering, metallurgy, original equipment manufacturer, second hand. [Read more…]
When equipment breaks unexpectedly it is good practice to investigate why it happened so that the root cause can be rectified and the problem prevented from again happening.
There are no mysterious causes, only poor systems or system failures. It is not often that people intentionally sabotage plant and equipment.
By analyzing why a thing happened the lesson can be absorbed and changes made to business systems to reduce its probability of reoccurrence.
In this article, four equipment failures are reviewed and investigated to determine their cause and the resulting necessary changes.
Keywords: root cause failure analysis, failure mode. [Read more…]
The efficient use of men, materials and external resources requires coordination and preparation.
When a job starts everything needed to do the job must be at hand and must be right to use. The maintenance planner does the preparation required prior to the start of a job.
The planner’s focus is to prepare everything needed to execute a job through to its successful completion and have it ready and on-hand before the job starts.
How well the planning job is done directly affects how efficiently the men do the work and how long it takes for it to be done.
Keywords: job scheduling, breakdown work. [Read more…]
The very best asset managers have maintenance under control.
Their entire organization’s systems and methods are tuned to preventing unplanned stoppages. They only do that which has first been thought through and prepared for.
But most importantly they understand the key factor to excellent asset care and work toward it continuously and energetically.
Keywords: preventative maintenance, reliability-centered maintenance, RCM, total productive maintenance, TPM. [Read more…]
Weld preheating is the purposeful application of heat to warm metal to a desired temperature prior to welding.
Preheating slows down the cooling rate of the weld and gives the metal more time to form a good microstructure, release internal stresses and dissipate hydrogen from the weld.
Keywords: thickness, weld puddle, cooling rate, temperature. [Read more…]
When a bolt and nut is tightened to draw the bolt head and nut together it stretches the shank, deforms the threads and loads the object trapped between the bolt head and nut.
The bolt shank acts like a spring being pulled apart and it tries to return to its unloaded condition.
The amount of tension developed in the shank is dependent on the number of turns of the nut.
The size of the torque required to turn the nut has little to do with the tension applied to the bolt shank.
Rather the amount of torque needed to turn the nut reflects the slipperiness of the threads.
Keywords: bolt tension, yield stress, the coefficient of friction.
This article covers some of the problems that can occur with bucket elevators and provides possible remedies.
Bucket elevators lift bulk materials from one level to another.
They are used on powders, granules, grain, chip shaped products and lumpy materials.
They function well when designed properly for the duty, and used as designed. [Read more…]
Many equipment breakdowns and stoppages occur because of improper clearance between holes and shafts.
The shaft is too tight in the hole; the center of the hole is not at the center of the shaft making it off-center; one part is loose on another and slips out of place or does not seal as it should. [Read more…]
A gearbox is used to control the operating speed of industrial equipment.
It converts a high input speed to a lower output speed and so permits one driver element, such as an electric motor, to do numerous duties.
Failure of the gearbox causes the equipment and associated plant to stop.
Proper selection, care, and maintenance of gearboxes is critical to your company’s continued profitability. [Read more…]
Chemical corrosion occurs at increased rates in agitated conditions.
Typical iso-corrosion curves for alloy metals no longer apply. These curves only show corrosion rates at various chemical concentrations and temperatures in stagnant conditions.
A typical curve is shown below. The curves are available from alloy metal suppliers on request.
When metals are selected for agitated corrosive conditions the curves can only be used in a relative sense.
They help grade the metal selection but they cannot provide absolute corrosion rates. [Read more…]
A benchmark is the end distance point from the start.
In the world of maintenance, it is the name for the targets that an organization sets for itself in an improvement program.
Benchmarking is often against world-best practice and it is used to provide direction and focus in an organization’s efforts to improve.
When RAV is chosen as the benchmark it means that the annual cost of maintaining the plant will be measured against the value of the plant.
RAV is a percentage of the cost to replace the plant. The lower the RAV the more effective the maintenance effort. [Read more…]
Vibration in equipment is the result of unbalanced forces.
Out-of-balance is corrected by adding or removing material so that when the equipment is operating the unbalance is controlled to an acceptable level.
Keywords: spring stiffness, damping, center of rotation, center of mass, natural frequency, isolation mount, counterbalance, out-of-phase. [Read more…]
Coatings provide industry with low-cost solutions to difficult chemical corrosion problems.
This article covers the use of rubber, fiberglass, and epoxy linings.
Keywords: rubber lining, resin, composite glass fibers, overlap joints, adhesive, primer, corrosion barrier, repair. [Read more…]
Bridging is the name given to the self- created arch that develops just above the outlet of a bulk material silo or hopper as it empties.
A bridge forms when wall friction holds up the ends of the arch.
To overcome bridging the wall friction must be reduced or prevented from occurring. [Read more…]