This article covers the conversion of the shaft bearings on a basket centrifuge from oil-bath to grease lubrication. [Read more…]
Converting from Oiled to Greased Shaft Roller Bearings
Temperature Sensing Elements
A Brief Introduction to Temperature Sensing Elements
The temperature of a process is an important measure to know as it indicates whether or not the process is in control.
The selection of the temperature sensing method depends on
- the required temperature range
- the measuring accuracy required
- the speed of response needed from the control system
- the process chemicals and conditions
The Watch Keeper
Equipment Operators as Watch Keepers
The watch keeper of old guarded their people and possessions. They were found walking about looking, listening, and watching for changes that signaled danger. Their job was to look for hazards and quickly raise the alarm before all of them were invaded and killed or captured into slavery. With sufficient warning the home group could rally to the defence and counter-attack the enemy.
Times haven’t changed that much. Instead of being invaded by the enemy we now get consumed by plant and equipment problems. If only there was an effective way to spot problems coming our way and mount a counter-attack before being overrun. [Read more…]
Spherical Roller Bearings
Understanding the Basics of Spherical Roller Bearings
Spherical roller bearings (SRB) are popular because they can take very heavy loads and are self aligning. Their design allows them to take combined loads in both the radial and axial direction acting together. Each roller is loosely retained in place within a cage that goes full circle between the raceways. Figure 1 shows a simplified drawing of a spherical roller bearing on a shaft under deflection. [Read more…]
Equipment and Plant Layout for Improved Maintenance
7 Consideration for Equipment and Plant Layout for Improved Maintenance
Equipment reliability studies show that the likelihood of failure increases the more often machinery is disturbed. The chance of something being done wrong rises every time an item of plant is worked on. Nothing may go wrong the first time or the second time but with each additional disruption there is an increasing possibility that an error will be made.
Simple, fast and uncomplicated access to individual items of plant and equipment means higher plant availability and longer time between failures. [Read more…]
How Fluid Flows in Pipes
The Basics on How Fluid Flows in Pipes
A fluid is either a liquid or a gas. In industry, they are piped from storage to the point of use. Correct design and installation of the piping system minimises pressure loss and improves the behaviour of equipment and processes.
This article briefly explains what happens to fluids flowing through pipes. [Read more…]
Capacitance Levels Probes
Capacitance level probes consist of a long rod or cable that protrude into a vessel and its contents. The instrument sets up an electric field between the probe and the tank wall using the contents of the tank as a dielectric (a nonconductor that allows an electric field to exist within itself). If the tank is non-metal, such as plastic or brick lined, two parallel rods are mounted in the level probe or a metal strip can be run on the outside of the tank. The electric field is set-up between the two probes or the probe and the metal strip. Figure 1 shows a simplified layout for a capacitance level probe. [Read more…]
Use Words Instead of Code Numbers
in your CMMS System
A work order full of code numbers confuses people. When work order type (breakdown, corrective, modification, etc) is described as Work Order Type ‘04’ you can guarantee that no one knows what ‘04’ is without looking it up on a list.
If a Trade Type is a ‘02’ and it means a fitter, you can be sure that a lot of work order requests from operators will be wrong and they will take the planner’s time to correct. Even more confusing is when the Work Order Type and the Trade Type are both an ‘04’! [Read more…]
Locating Pressure Relief Valves
What readers will learn from this article.
- The purpose of pressure relief valves.
- How pressure relief valves work.
- The correct way to install relief valves.
- Selection and testing issues for pressure relief valves.
Centrifugal Pump Cavitation
What readers will learn in this article.
- How pressure and temperature changes cause cavitation.
- How cavitation causes damage to equipment.
- Gas entrainment compounds the problem.
- Methods to reduce the occurrence of cavitation.
What is Cavitation?
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…]
Stress in Metals
What readers will learn in this article.
- Explanation of stress and strain.
- How metals yield and deform under stress.
- What happens at the molecular level in metals under stress.
- Methods to minimise stress concentrations.
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…]
Experiences with Pneumatic Actuators
What readers will learn in this article.
- How pneumatic actuators work.
- Air pressure requirements for proper operation.
- Air supply piping installation requirements.
- Air quality requirements for long life operation.
The CMMS* User
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…]
Shaft Coupling Selection Issues
What readers will learn in this article.
- The purpose of shaft couplings and how they work.
- What to consider when selecting shaft couplings.
- Maintenance issues with using couplings.
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 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…]
