CHAPTER 1 : Introduction to maintenance management
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Mechanical drives
mechanical drives are used to provide a variable output speed from constant speed power source or to provide torque increase for a variable speed power source as in an automobile
Types Of Mechanical Drive
a) Geared Transmission - Provides specific fixed type ratios.
b) Belt drives - Provide flexibility in the positioning of the motor .
c) Chain Drives - Provide infinitely variable speeds.
d) Traction Drives - Provides adjustabe speed with relatively high speed.
Advantages
a) Mechanical drives are less costly than competing electrical drives and their control is much simpler.
b) They are used in industries ranging from aerospace to mining and heavy industry.
c) With the advanced technology, the working of mechanical drive has become more efficient.
Disadvantages
The disadvantage of these drives is that they are not durable and cannot be controlled as precisely as electrical drives. They cannot transmit as much power as electrical drives when variable speed is essential.
Maintenance
Mechanical drives have internal spaces that have void spaces where residues can be deposited. The system should be cleaned at regular intervals. Clean-in place (CIP) is a method designed automatically to clean pipes and drives. This method is used to clean the void spaces in the drives.
Pump
Most common pumps
a) external gear pump
b) internal gear pump
c) lobe pump
d) vane pump
Two identical gears rotating against each other. One driving gear and one driven gear
Advantages
High Speed
High Pressure
Relatively quiet operation
Can use variety of materials
Disadvantages
No solids allowed
Fixed End Clearances
Applications
Low volume transfer or application
Acids and caustic (stainless steel or composite construction)
Industrial and mobile hydraulic
Various fuel oils and lube oils
Chemical mixing and blending (double pump)
Chemical additive and polymer metering
One interior gear and one exterior gear. Interior gear drives the Interior gear drives the
Advantages
Disadvantages
Applications
Excellent for high-viscosity liquids
Operates well in either direction
Single adjustable end clearance
Easy to maintain
Requires moderate speeds
Medium pressure limitations
All varieties of fuel oil and lube oil
Resins and Polymers
Alcohols and solvents
Asphalt, Bitumen, and Tar
Polyurethane foam (Isocyanate and polyol)
Food products such as corn syrup,chocolate, and peanut butter
Paint, inks, and pigments
Soaps and surfactants
Glycol
Similar with external gear pump, but the lobes do not make contact.
Timing gears drive both lobes.
Advantages
Disadvantages
Applications
No metal-to-metal contact
Non-pulsating discharge
Pass medium solids
Long term dry run
Requires timing gears
Reduced lift with thin liquids
Polymers
Paper coatings
Soaps and surfactants
Paints and dyes
Rubber and adhesives
Pharmaceuticals
Food applications
Rotor with spring-equipped vanes. Single motor drives rotor.
Advantages
Disadvantages
Applications
Handles thin liquids at relatively higher pressures
Develops good vacuum
Compensates for wear through vane extension
Can run dry for short periods
Complex housing and many parts
Not suitable for high pressures
Aerosol and Propellants
Aviation Service - Fuel Transfer, Deicing
Auto Industry - Fuels, Lubes,
Refrigeration Coolants
Bulk Transfer of LPG and NH3
LPG Cylinder Filling
Alcohols
Refrigeration - Freons, Ammonia
Solvents
Aqueous solutions
Common Failure
Cavitations
Air in Fluid
Coupling Misaligned
Pump worn or damaged
Excessive load
Damage caused by metal object
Excessive heat
Overpressure
Incorrect Installation
Pump Failures
Pumping machinery and pumping station are
very important components in a water supply system.
Pumping machinery is subjected to wear, tear, erosion and corrosion due to their nature of functioning and therefore are vulnerable for failures.
Sudden failures can be avoided by timely inspection, follow up actions on observations of inspection and planned periodical maintenance.