Plant Maintenance

A U-tube manometer is the simplest of the pressure measurement devices. Its name comes from the U-shape formed when the two ends of a flexible tube full of liquid are raised to keep the liquid from coming out the ends. A U-tube manometer is a ‘liquid’ balance. 

A spring balance used in the kitchen weighs a load by matching the force produced by the weight of the load with the force produced from the tension of the balance spring. The change in length of the spring is a measure of the load’s weight and is shown on a graduated scale by a pointer attached to the spring. Similarly, a U- tube manometer is used to balance the weight of the liquid in one leg of the ‘U’ against the pressure introduced into the other leg. The difference in height between the two legs of liquid represents the pressure pushing the liquid down one leg and up the other. The height difference is measured on a graduated scale. [Read more…]

A gear pump uses two meshing, toothed cogs to force water from the inlet of the pump through to the outlet. Figure No. 1 shows a simplified drawing of an external teeth gear pump on the left along with the alternate arrangement of internally pointing teeth. [Read more…]

The focus of maintenance has changed from repairing equipment to keeping it running for longer between breakdowns. This requires more consideration of how to get longer running life between repairs, i.e. higher reliability, on a machine. To accomplish this a number of ‘tools’ have been invented and developed to allow maintainers to pinpoint problems and fix them. In this article three of the most effective ‘tools’ will be introduced. Root cause analysis, Weibull analysis and lifecycle simulation can be used to help organisations achieve proactive approaches to maintenance or adopt a “reliability based approach” to maintenance.  [Read more…]

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Doing a job safely is no accident! Like all good outcomes safety is a result of good planning. As the Chinese philosopher Confucius said, “In all things success depends on previous preparation and without such preparation there is sure to be failure.” If you want safe work it needs to be planned as part of the job.

The other important fact about safety is that it is a personal responsibility. It is up to you to do the job safely. There is not a manager or supervisor in the world that wants to go to prison or be fined for a death or maiming because of his negligence. That means people in-charge want jobs done safely too. All they ask is that the safety procedures and practices used on the job be the least that are adequate while still meeting all the safety issues.  [Read more…]

Centrifugal Pump Life Extension – The Volute

What readers will learn from this article.

• Pump volute problems and fixes.
• Pump set-up and piping connection issues to get right.
• Process conditions that will cause problems.
• What to watch for with pump shaft designs.

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What readers will learn from this article.

• Basic theory of heat exchange across walls.
• Necessary properties of fluids to make heat exchangers work.
• Protecting and checking heat exchangers against corrosion.
• Issues with using shell and tube heat exchangers.
• Issues with using plate heat exchangers.

This article introduces readers to heat transfer in heat exchangers. It explains the concepts of temperature gradients across walls and parallel- current and counter-current flows. Both shell-and-tube and plate heat exchanges are discussed along with their common operational problems and remedies.

Shell-and-tube and plate heat exchangers (HXCH’s) are recuperative type devices, meaning that flowing fluids exchange heat through a dividing wall. The exchange of heat occurs from the hotter liquid to the cooler one. The hotter liquid is at a higher energy level than the colder liquid and the energy flows from hot to cold in an attempt to reach a steady equilibrium state at an intermediate temperature. [Read more…]

What readers will learn from this article.

• Basic theory of reciprocating compressor operation.
• Introduction into work and power calculations for a compressor.
• Explanation of Free Air Deliver (FAD).
• Issues with using rotary screw compressors.
• Issues with using reciprocating compressors.

Compressed air is one of the most used service fluids in industry. This article introduces the basic design concepts of an air compressor and discusses some of the common problems and solutions found in both reciprocating (piston goes up and down) and rotary screw (twin, meshed, rotating, helix) air compressors. [Read more…]

What readers will learn from this article.

• Overview of how a programmable logic controller (PLC) operates.
• Communication methods used to connect the PLC to equipment.
• Dangerous practices that will lead to trouble if not corrected.

A process logic controller is a computer designed for monitoring and controlling equipment. The personal computer that many people have at home is designed to accept signals from the keyboard or mouse and use instructions (software) to display the resulting effects on a screen (monitor). A PLC accepts signals (inputs) from sensors located throughout a piece of equipment or process plant. It then follows the instructions (program) within its memory and sends out commands (output) to operate equipment. [Read more…]

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.

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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…]