Tuesday, 8 November 2016

Why Equipment Maintainability Should Not be an Afterthought

Article extract from ReliablePlant newsletter:

Most organizations have a large installed base of equipment that is the target of their various initiatives such as six sigma, lean, equipment maintainability etc. In most cases these initiatives require training of personnel as well as retrofitting equipment to improve the probability of success in these endeavors. We are generally are not surprised by the need to make these changes as the equipment was often designed and procured before we determined that these types of changes would be beneficial. The purpose of this paper is to raise the awareness that these items should now be incorporated into the design, procurement and installations phases of new equipment. Equipment maintainability should no longer be an afterthought.


The intent of this article is to raise the awareness and expectations of the entire organization so that we ultimately have equipment installed that gives our maintenance organization the best opportunity to meet or exceed our expectations for the operation of our assets. Our designs should incorporate maintainability concepts, our procurement specifications should detail maintainability requirements and our installation process should incorporate equipment maintainability guidelines and principals.

It’s not that our designers and procurement personnel don’t care, it is simply a function of not realizing the potential and often being somewhat disconnected form the environment in which the equipment will operate. Often the focus of these individuals is to ensure basic functionality, deliver equipment on time and within budgetary guidelines. As many of these very capability people have not worked in the maintenance environment, many of the concepts we will talk about, are not in their knowledge base. I was fortunate to have worked specifically in the design, procurement, installation, operation and maintenance functions for my employer of 38 years, Goodyear. In each of those functions I performed to the best of my ability, but honestly was amazed at how many equipment maintainability fundamentals I missed, until I had the opportunity to walk in the shoes of the maintenance organization. If I had my way, every designer would be assigned to maintain their design for a period of time after it is installed. I can say from personal certainty, that if designers had to maintain some of their work, their next effort would reflect a different respect for the maintainers.


Maintainability refers to the ease with which maintenance work can be done. It involves the process of ensuring that equipment can be easily and safely maintained, and the maintenance support required can be minimized.

Potential Benefits of Equipment Maintainability

We need to design maintenance into our systems. Great maintenance procedures and skilled craftsmen can be hampered by not following some basic concepts. Properly done we should expect:

  • Reduced time to complete scheduled and unscheduled maintenance
  • Reduced maintenance errors
  • Reduced maintenance related injuries
  • Minimize personnel training requirements
  • Improve trouble shooting performance
  • Lower Maintenance cost

Suggested Guidelines

  • Design replacement tasks to be as modular as possible.
    • Especially for drive systems, this applies to ball screws, drive belts, conveyor belts, and gearboxes. All of these parts will fail during the machine life.

  • All pressure and vacuum gauges should be marked with a green zone that represents the normal operating range of the system to which it is attached
  • Inspection points (gauges, meters, sight glasses, chains, pulleys, belts…etc.) should be:
    • Clearly identified
    • Easily readable from location of inspector
    • Located such that no guards or obstructions need to be moved to do routine visual inspections.

  • When considering the ergonomics of a repair or inspection activity, design for the 5th and 95th percentile people in accordance with EDGE (Ergonomic Design Guidelines for Engineers) principles.
  • Clearly mark lifting points and weight of lift.
  • Most machines should have an air fitting hook up.
  • Most machines should have a 30 Amp – 120VAC outlet or equivalent to support maintenance power tools.
  • If possible design connection points so that they can only fit together in the intended way
  • Identify flow direction and type of all fluid lines. (including pneumatic, hydraulic, water, lubrication and steam lines)
  • Provide properly designed access stairs, platforms etc to facilitate access to hard to reach maintenance and inspection areas.
    • If not, equipment may be damaged by using unintended devices as steps etc

  • Coupling Guards shall allow Coupling Greasing to be performed without removal of the guard.
  • Laminated sheet detailing Lock Out Tag Out procedure should be affixed to the machine.
  • Special lock out devices required to complete lock out should be designed into the machine or installed on a cabinet near the lock out point for ready access.
  • Machine guarding should be made of materials that adequately protect the hazard but still allow for visual and infrared inspection of the apparatus being guarded. If expanded metal or fencing is used paint the fencing black to facilitate visual inspection.
  • All chain sizes shall be clearly labeled on equipment near point of use.
    • Tags should be grease resistant ie Plastic, brass tags/labels

  • Daily and weekly running inspection routine/instructions should be posted on machine.
    • All inspection points should be clearly labeled

  • Use common components, such as pumps, reservoirs, accumulators, motors, gearboxes, VF drives, sensors etc as much as possible.
    • This should be considered at the plant level as well as at the individual machine level

  • Direction of rotation to be clearly noted for Motors, pumps, fans, blowers, conveyor drives, gearboxes etc.
  • Indicate a place where an identification code could be marked on manufactured parts (or mark at manufacture).
    • This will aide in identifying replacement part. Identify method of identifying part (stamp, indelible ink)

  • Any guards or covers on the machine should be attached by the fewest number of screws or other fasteners necessary. This will facilitate speed if these guards or covers must be removed or replaced. Same type screws.  (Codes may require at least one fastener that must be removed with a tool)
  • Ability to clean the machine should be considered during design and installation. This would include a cleaning plan and how services are routed to the machine.
    • If plan calls for wash down, machine should have water fittings and floor sloped to drain.
    • Where possible all concrete surfaces and piers should be sloped to the nearest drain (environmental review needed)
    • Pipes, wires, tubing that are providing services to the machine should be routed so that they have enough ground clearance to allow for sweeping or mopping of the floor below

  • All pressurized systems must include a method for reducing system pressure to 0 psig and a means to verify this.
  • Avoid castings for moving parts, or parts that may be hit by other parts of the machine
    • Castings are very difficult to repair, particularly emergency breakdown

  • Maintenance tasks on the machine must be considered with regard to how the maintenance techs will access the area of the machine to be maintained.
    • This should include assessment of clearances for access, height from floor, provisions made for access to machine areas elevated from floor (steps, platforms, ladder), and disassembly required to perform maintenance
    • Fall Protection tie offs shall be provided for access to components which if accessed would expose the technician to a fall hazard of greater than 6’.

  • Do not locate inspections points more than 1 meter from the inspectors eyes
  • Do not install inspection points behind components, under protection covers or other points that require work to reach them
  • Design interfaces so that the connection can only go together correctly
  • Design interfaces so you can only install the correct component, employing unique bolting patterns, guide pins etc.
  • Make every routine maintenance point clearly visible
  • Minimize disassembly and special tools needed to repair items that are wear parts, parts that are expected to fail frequently, or will need to be adjusted frequently
    • Access to wear or commonly adjusted parts should also be considered and steps/maintenance platforms added if necessary
    • If non-commercial special tools, jigs, or fixtures are needed they should be provided by the equipment manufacturer at installation. Also these special tools should be given manufacturer part numbers and those part numbers be clearly communicated and documented in the maintenance manual to the plant so that they can be included in the store room system
    • All tools for routine jobs should be integrated on the machine in a lockable shadow board.

  • Drive belts should be removable without removing other machine parts (this does not include guards)
    • Other parts should not trap the belt
    • Drive Belt Guards shall use expanded metal to allow IR Inspection for misalignment.

  • Vendor should align all coupled shafts to stated tolerances
    • Vendor shall supply as installed alignment measurements for all coupled shafts.
    • In cases where thermal expansion is significant and will affect the alignment “cold” alignment specifications and tolerances must be supplied by the manufacturer

  • Alignment tolerance shall be clearly marked on a label near the coupling.
  • Belt type and tension shall be labeled and affixed at or near the belt point of use.
  • Provide jack screws with lock nuts for all axes to be aligned
    • Ensure that jack screws and lock nuts are accessible.
    • Ensure that if base bolts with nuts are used, that a full sized wrench can access the base bolt nuts and allows for tightening

  • Where possible, electrical components should be arranged/segregated to permit access to low voltage controls without exposure to higher voltages (Reduce need for specialized PPE for arc flash protection)
  • Test points, key pads etc should be made accessible without exposure to energized conductors
  • Panels should be designed to be finger/palm safe (protect from shock hazard)
  • Utilize proximity switches with indicator lights to determine if it is working
  • 110v coils for solenoid valves should have indicator lights to determine if they are energized
  • Control wiring must be separated from power wiring to avoid transient noise feeding in to the control system
  • Active cooling devices on electrical panels should have a provision to visually be able to tell that the cooling devices are working.
  • Label, and where possible color code, each wire in a harness or cable to facilitate tracking from origin to termination. Each wire, cable, and coax-to-connector interface should be provided with a source of identification to aiding trouble shooting, repair, or modification.
  • Clearly labeled components make troubleshooting more effective.
  • Do not manufacture or dress connectors containing more than 25 wires or cables as a single integrated harness. Group the wires or cables into runs of no more than 25 wires or cables each. In addition to making trouble shooting and repair easier, this approach helps avoid large bend radii, thereby simplifying routing, packaging, and stowage.
  • Route cables so that 100 percent of a cable will be viewable for inspection without using any special tools such as a borescope.
  • Use positive locking, quick disconnect electrical connectors and identify all pins on each connector to save man-hours, prevent foreign object damage (FOD) and decrease the chance of personal injury.
  • Select connectors so that contacts on the “live” or “hot” side of the connection are socket type rather than pin type to minimize personnel hazard and to prevent accidental shorting of live circuits.
  • Where multiple connectors are located in close proximity, ensure:
    • a minimum hand tool arc of 120 degrees can be maintained
    • stagger fittings to ensure firm coupling interface/hand tool interface can be accomplished without inducing damage to adjacent lines.

  • If possible avoid fasteners smaller than ¼” in diameter. Fasteners smaller than this are easy to damage by hand. They shear, and the socket fails frequently.
  • Avoid reliance on mechanical fasteners solely to facilitate manufacturing.
  • Standardize fasteners where practical to avoid multiple tools and possibility of wrong grade usage
  • When high strength fastener needed, label to avoid use of inadequate material
  • Chemical thread lockers should be avoided on fasteners that must be adjusted often.
  • Match marks shall be painted by the vendor on all fasteners at time of final acceptance, except for items requiring disassembly for transport.
  • All fasteners shall be match marked at final acceptance.
  • Fastener re-installation torque and socket size shall be labeled for all fastener’s that must be disassembled to perform manufacture recommended maintenance by a small label affixed near the fastener(s).
  • All oil filters should have differential pressure gauges or sensors that indicate when replacement is necessary
  • Oil filters should be in a duplex arrangement that allows changing a filter while the machine is running
  • Replacement filter part number shall be labeled and affixed near the filter
  • Evaluate each lubrication point to determine:
    • The proper fitting style
    • Ability to plumb grease ports out where necessary
    • Potential application of automatic lube systems.

  • Grease points must be safely accessible. (Preferable that they are assessable with the machine running)
  • All lube points should be easily identifiable on the machine and frequency, type and amount of lubricant information easily accessible.
  • A laminated lube chart with diagram of lube points, frequency, quantity, and type of lubricant shall be posted on machine.
  • Lubrication points on machine shall be labeled to match lube chart.
    • Type
    • frequency
    • Quantity

  • All hydraulic units and gearboxes that hold greater than 10 gallons of oil should be equipped with proper sampling points
  • Max and Min levels for all fluid reservoirs shall be clearly marked on all reservoirs. This should typically be done by including a sight glass on the reservoir with min/max levels marked.
    • Both running and shutdown levels should be indicated so that filling a machine while running does not result in an overflow when the system shuts down, and oil drains back to tank.

  • All systems shall have provisions for the adding of oil through a filter such as a 3 micron, Beta>100  line filter


In an ideal world, the majority of the suggestions covered in this article will be addressed during design and installation. If not, there is still much to be gained in reviewing existing equipment and making modifications that improve the maintainability of our assets.

This article was previously published in the Reliable Plant 2013 Conference Proceedings.
By Jerry Putt, Noria Corporation

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