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Threaded connections on process chemicals and utilities piping can be difficult to seal. Leaks from threads in steam and compressed air service are common. This article looks at pipe thread design and the proper sealing of threads. [Read more…]
Many explosions in the processing, manufacturing and bulk materials handling industries involve flammable gases or vapours and explosive dusts or fibres. Such chemicals are known as hazardous materials. This article provides a basic overview of the design requirements for hazardous areas.
This article covers the operation of steam traps and how they work. Steam is a greatly used medium. Its use ranges from heating process and domestic fluids through to driving turbines by the expansion of the vapour. Yet the steam trap at the bottom of a drop leg is easily forgotten. [Read more…]
When in solution (dissolved in water) the molecules of an acid or a base dissociate (disunite) into a mix of component parts and the full molecule. The components are electrically charged + or – ions. Ions are unstable and ‘want’ to bond chemically to become stable. In strong acids and bases many ions are present, making them reactive and dangerous. [Read more…]
Life cycle costing (LCC) is a way of analysing equipment purchase choices. If the analysis is done right and all factors are addressed, and the information is good, you would select the item that cost the least amount to own (buy and use) over its working life. This piece of equipment when compared to other suitable items would perform its lifetime service at least total cost to the organisation. [Read more…]
Properly designed o-ring grooves and properly installed o-rings stop the passage of pressurised liquids or gasses. Flexibility while being deformed under pressure is their greatest sealing advantage. O-Ring Design and Materials O-rings are made of elastomeric materials such as rubbers and plastics. They deform under pressure and then return back to their original shape once the pressure is removed. They also accept the movement of mirror-finish shafts while deformed by pressure. Usually they are shaped like a rubber elastic band of round cross section, but they can have rectangular, trapezoid and even ‘+’ shapes depending on the application. The material, internal diameter (ID) and cross section diameter specify o-rings of round cross section. [Read more…]
A cooling water tower (CWT) is used to remove heat from incoming hot water and reduce it to a lower temperature. It does that by evaporating off some of the hot water. The evaporated water takes away the heat. Exactly the same process occurs when your body sweets to keep you cool. You cool off even faster if there is a breeze blowing. [Read more…]
Safety showers and eyewash stations are installed when dangerous goods are present. The shower installation has to meet recognised standards like American National Standard Z385.1. This article notes the key requirements for safety shower installations and discusses some practical issues. [Read more…]
Static electricity is the build-up of opposite polarity (positive and negative) electrical charges on two different substances in contact by the movement of one surface across the other. The spark that can occur from static build-up is the result of the opposite charges neutralising themselves when the electrical field between them becomes strong enough to overcome the gap resistance. [Read more…]
Accounting decisions can greatly affect maintenance costs. Two examples are the decision to purchase items as maintenance or capital and plant item asset numbering.
Maintenance costs are expensed in the financial year incurred and are claimed as a tax deduction at the company tax rate (soon 30% in Australia) in the year they are spent. Capital expenditure, on the other hand, is depreciated and can only be claimed as a tax deduction over the usable life of the equipment. Depending on the industry, the depreciation rate for industrial equipment is 20% per year. It can be as little as 2.5% per year for office buildings. There is a clear tax advantage to claim as much expenditure as possible as a maintenance cost and not a capital cost. [Read more…]
This article is a basic introduction to the mechanism of metal fatigue failure where parts break after a period of time in service. Explanations of accepted theories are provided and relevant design practices to reduce metal fatigue are presented and explained. [Read more…]
This article reviews the requirements for building and maintaining vertical, bulk liquid storage tanks. Issues, which affect the care of large storage tanks as well as common problems, are reviewed.
Bulk liquid tanks can be round, horizontal cylinders, vertical, cylindrical tanks and occasionally spherical vessels. We are concerned here with vertical tanks and vessels whose internal volumes are measured in tens of cubic meters through to hundreds of cubic meters. Examples are oil refinery storage tanks and process chemical storage tanks.
A proximity switch is the common name for a range of detectors that generate an electrical signal when a physical mass cuts through their sensor field. Upon detection of an object, the electrical signal is sent to a controlling device and is used to monitor and control the operation of the equipment.
The practice of maintenance has been developing for the past 300 years. Since the start of the Industrial Revolution machinery and their control systems have played a critical part in our ability to produce consumer and industrial goods. Over that time different maintenance philosophies have developed in response to changing technology and increasing costs.
The progression in philosophies started with breakdown maintenance (BM), then to time-based maintenance such as preventative maintenance (PM) and shutdown maintenance. More recently condition-based maintenance (CM) has become significant. The next step is predictive maintenance. [Read more…]
This article discusses the use of vee-belt drives. It covers some basic theory of friction drives and lists 11 factors to be considered when using vee-belt drives. [Read more…]
