Your Reliability Engineering Professional Development Site
A computerised maintenance management system (CMMS) is the maintenance department’s most important tool. It provides insight into the behaviour of the facility’s individual assets, i.e. the plant and equipment. For a CMMS to be of use it must be used as an information ‘bank’ that can be investigated. There are 9 really good reasons to use a CMMS. And each one of them alone makes a CMMS worth having. [Read more…]
When oil in gearboxes become contaminated there is a rapid loss of bearing operating life. It is critical that metal particles, dirt, sand, oxidisation products, etc be removed from the oil before they gouge and tear-up the finely toleranced machine parts. Oil replacement, contamination prevention and oil filtration are common practices religiously adopted by the best in the equipment reliability management business. This article explains the fine requirements for successful contamination control to insure long trouble- free equipment life. [Read more…]
Steam boilers not used for power generation and of smaller size and energy output are termed packaged boilers. The heat source is usually either electric coils or a burning fuel. When a flame is used to heat the water it is known as a fired packaged boiler. Fired boilers are considered efficient steam generators with about 85% of the available energy converted to steam. They can be of water-tube or fire-tube design. Boilers incorporate many key aspects of heat transfer to create steam from water. This article describes how fired boilers work and their key components. [Read more…]
Heat is energy and its nature is to flow from a state of high excitement to one of low excitement. Heat is transferred from a hot place to a cold place by convection, conduction or radiation. This article explains the three modes of heat transfer and provides simple examples of each. Methods to reduce and increase heat transfer are also presented. [Read more…]
The electrical conductivity (and its opposite, resistivity) of water based solutions indicate its electrical current carrying ability. High conductivity occurs when many charged atoms and ions are in the water. This typically means the presence of dissolved metals, salts, acidic or alkali chemicals. Conductivity probes are used to measure the total level of charged particles present. This article explains how conductivity probes work and their application in boiler water treatment and management. [Read more…]
A spinning pump impeller provides the means to draw incoming product through the pump, energise it, and then force it out under pressure. The impeller coverts the electrical energy from the motor into hydraulic energy of the liquid. It does this by taking the liquid into the center of the impeller and flinging it outward at high speed. To efficiently continue to do this the impeller must remain in the same condition as it was when first installed. If the impeller deteriorates the conversion from electrical to hydraulic energy becomes inefficient. Power is wasted, flow and pressure fall and the pump cannot do its designed duty. [Read more…]
How do you decide what level and type of maintenance to use on an individual item of plant and its sub-assemblies? Not all equipment is equally important to your business. Some are critical to production and without them the process stops. Others are important and will eventually affect production if they cannot be returned to service in time. While other items of plant are not important at all and can fail and not affect production for a very long time. [Read more…]
A belt conveyor is a moving surface used to transport product from one end to the other. In its basic form it consists of a driving head pulley, a tail pulley, the moving belt, support rollers, cleaning devices, tensioning mechanisms and a structural frame. Though simple in concept its many components need to work together as a system to get the best performance and operating life. Critical to that is an understanding of how to care for a belt conveyor and tune it for successful operation. [Read more…]
Moving slurries about. Slurry is solid particles in a liquid. Concentration can vary from mostly liquid to mostly solid. Slurries are usually transported through pipe work using pumps, pressurised gas or steam. Different concentrations and different particulate produce different flow characteristics. Successful slurry transport requires knowledge of the particulate, its transport behaviour in the liquid at different concentrations and speeds, the nature and friction effects of the pipe work system and selection of the right motive method for the application. This article provides information for transporting slurries of up to 60% solids concentration. [Read more…]
Abstract
Effect of process changes on electric motors. This article explains the effect of changing process loads on AC induction electric motor performance. The motor’s behaviour is a response to the load imposed on it by the equipment connected to it. The equipment’s behaviour is itself a response to the duty and service it has to perform. Where the equipment duty and service is adjustable by the operator, or fluctuates as the process changes, the motor will react to those changes. When the changes are so excessive that they are beyond the motor’s ability to handle them the motor stops and the equipment or process stops with it. Keywords: squirrel-cage motor, overload. [Read more…]
The 5 s method of operation – A Five S program focuses on having visual order, organization, cleanliness and standardization throughout the workplace and the operation. It is a structured method to put operators and maintainers in control of what they do. [Read more…]
Grease and oil are the key lubricants used throughout industry to reduce friction between metal parts. Lubricants can only reduce friction if their immediate environment sustains their lubricating properties. Once the operating conditions are known a suitable lubricant with the right properties can be used. When the lubricant is in place it is necessary to maintain the environment and the machine to the specified design standards and protect it from changes to the design conditions. There are six key factors to address for trouble- free life where grease or oil lubrication is used on machinery. [Read more…]
The Big Bang – starting and stopping equipment under load. When a machine starts-up its parts move from zero speed to operating speed in a short time (the reverse when stopping). During this short period the biggest forces that the machine experiences act on its components. If during the start-up or slow-down the product or process loads are added to the machines own self-loads the forces acting on the machine’s parts are horribly magnified. If these impulse forces exceed the machine’s design allowance, or cause gradual fatigue, then the stressed parts will shatter without warning. [Read more…]
Rotating shafts under bending stress. It is common to transmit motion using rotating shafts. The shafts are mounted in bearings and turned by force through a drive arrangement. The shafts usually also carry a load. These loads cause bending and the shaft reacts by producing counter stresses within itself. Provided the reactive stresses are within the shaft’s strength range it will take the load. But if the stresses are greater than what the shaft can take it will bend. Even if the stresses are below the load limit but fluctuate, it is possible that the shaft will break from fatigue. The point of highest stress can be found by looking at the arrangement of the shaft supports and loads and calculating the forces and stresses.
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Orifice plate meter flow measurement. An orifice meter is a circular piece of metal plate placed between flanges in a pipe. In it is a square-edged round hole machined 0.5 to 0.8 pipe diameter in size. Pressure tapping points are placed either side of the plate at specified distances. The orifice causes a flow restriction and produces a pressure drop from one side of the hole to the other. The amount of pressure difference is proportional to the flow of fluid through the hole. The flow is calculated from the pressure difference and flow areas using accurate mathematical formulas. [Read more…]