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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…]
This article explains the metal corrosion process including the basic chemistry of how metal loss occurs. Methods to control corrosion are also listed and explained. [Read more…]
When a control valve or manual valve is shut fast in a full pipeline of moving liquid, the liquid comes to a sudden stop. If the pipe suddenly starts banging and thrashing about you can be sure a water hammer was created. [Read more…]
This true story could have been a lot worse. A NB100 (4”) flanged plug valve was removed from a 98% sulphuric acid tank nozzle and returned to the supplier. When the valve was opened for inspection at the supplier’s workshop acid was sprayed over the repairman’s legs.
If 98% sulphuric acid lands on skin it immediately boils out the moisture in the skin and burns it. A review of the incident was conducted to learn from the accident and to put corrective measures into place. [Read more…]
This article explains the operation of peristaltic (hose) pumps and gives twelve points to be aware of when using them. [Read more…]
This article presents a basic explanation of electric motor construction and operation along with eleven problems that can be encountered with their use.
Most electric motors in industrial equipment are three phase alternating current induction motors. Induction is the creation of an electric current across a gap. Two types of induction motors are commonly used: squirrel-cage and wound-rotor. The names come from the way they are built. [Read more…]
In this article on pulse jet bag house dust collectors we cover twelve factors spanning their design and operation.
A bag house dust collector is used to separate dust from a dust-contaminated gas stream. The gas is filtered through bags made of fabric. The fabric traps and filters out the dust while the cleaned gas passes through. The fabric consists of either woven or intertwined (felted) fibres. The bag fibre is selected for its ability to give a long working life within the internal environment of the dust collector. [Read more…]