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What readers will learn in this article.
Cavitation is the occurrence of vapour bubbles in a liquid. A vapour bubble will form when the pressure in a liquid falls so low it boils or the temperature rises so high it boils. [Read more…]
What readers will learn in this article.
Too much stress in metal will cause it to fail. Failure can occur by putting the metal under a once-only load greater than it can take or by continually loading the metal cyclically with a high load less than the breaking load (metal fatigue). [Read more…]
What readers will learn in this article.
Written instructions make it clear.
Written directions given to maintenance tradesmen to reduce the chance of making an error and to reduce time spent looking for information are called job procedures or job instructions. [Read more…]
What readers will learn in this article.
Couplings are used between shafts to connect them so power can be transmitted and to allow for axial expansion. Shafts can either be aligned or intentionally inclined at an angle to each other. When at an angle a universal joint is used to connect the shafts. When aligned a shaft coupling is fitted. [Read more…]
Shaft alignment on pumps. Shaft misalignment is one of the most common reasons for bearing and mechanical seal failures. Rotating misaligned shafts produce vibration and complex fluctuating radial and axial loads that lead to breakdowns. Shaft alignment is a precision maintenance requirement that requires exacting care and detail and if not performed will cause much production down time.
Keywords: axial alignment, laser alignment, dial indicator, soft foot, shaft coupling. [Read more…]
Fibreglass construction and repair. Fibreglass is a glass fibre reinforced plastic composite with excellent chemical resistance properties. Its physical properties, selection of resins and glass, method of construction and fabrication and peculiar repair requirements must be appreciated when using this material.
Keywords: laminate, backing layer, structural layer, corrosion barrier, crack repair, winding angle. [Read more…]
What readers will learn in this article.
Preventative maintenance stops breakdowns. Preventative Maintenance requires people to regularly walk around looking, feeling, listening, smelling (sometimes even tasting) and thinking about their equipment’s operating condition. The three foundations of classical Preventative Maintenance are regular lubrication checks, drive train monitoring and equipment mounting inspections.
Keywords: work order, inspection, watchkeeping, CMMS, computerised maintenance management system. [Read more…]
They are used on shafts that encounter axial forces or combined loads (both axial and radial forces). Examples are centrifugal and helical rotor pump shafts and helical and worm gear shafts in gearboxes. Their design only permits axial forces in one direction. For alternating axial loads they must be installed as a bearing set to accommodated the forces from both directions. When set back to back, and less so when set face to face, they act to stiffen the shaft and handle larger bending moments such as overhung components or high midpoint shaft loading.
Keywords: floating bearing, preload, clearance, tolerance. [Read more…]
A confined space is anywhere not normally meant for human habitation in which access maybe restricted and the conditions in the confinement may be inadequate to support life or could cause engulfment. Obvious places are tanks, vessels, silos and below ground pits. The less obvious ones are cold rooms, areas of plant sandwiched between machinery and equipment, tip truck trays and open pit mines.
Keywords: risk assessment, hazard identification, job safety analysis, safe atmosphere. [Read more…]
Sizing liquid flow pipelines easily. Designing pipe work for liquid flow requires calculating the pressure losses along the pipe due to pipe friction. Once the losses are known the right pipe diameter can be selected. If full engineering calculations are not possible the conservative approach is to select pipe sizes that produce a velocity of less than 3 m/sec.
Keywords: pressure loss, viscosity, friction factor. [Read more…]
Mag-flow meters are used to measure the flow velocity of conductive liquids. In a magnetic flow meter an electromagnet placed either side of the bore creates a magnetic field when the power is turned on. As the conducting liquid flows through the magnetic field a voltage is developed across the liquid. Insulated electrodes flush mounted in the wall of the meter detect the voltage. The magnitude of the induced voltage is proportional to the liquid velocity, the length of the meter and the strength of the magnetic field.
Keywords: electric current, isolation flanges, calibration. [Read more…]
Equipment Identification tags save time. Identifying equipment for operators and tradesmen will save time, reduce errors and promote accurate record keeping. Equipment identification involves putting a unique number and a unique written description onto a machine.
Keywords: CMMS, computerised maintenance management system, planning, breakdown repair, reporting faults, equipment tags, catalogue. [Read more…]
Experiences with magnetic (magdrive) pumps. Magnetic drive pumps come in three varieties – canned motor pumps, all metal pumps and plastic lined metal pumps. They are sealless and cannot leak into the environment. Long, repair- free service life depends on recognising the limitations of these pumps. This article covers issues with using direct mounted, lined magdrive pumps experienced ‘in the field’.
Keyword: separation liners, chemical compatibility, sediment, particulate. [Read more…]