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EFFICIENT PREDICTIVE MAINTENANCE TECHNIQUE Making machines safe and reliable

Jul 29, 2022

Predictive, or condition-based maintenance is replacing preventative maintenance, thanks to the recent technological advancements. The article highlights one of the most efficient maintenance techniques. Look, Listen and Feel (LLF) approach that is a monitoring activity, which that increases the dependability of equipment and machinery multi-fold.

The basics of safety come from good maintenance. The first step in maintenance comes from the careful, systematic, periodic inspection of equipment and system elements. Recording of observations is the second step. Analysis of the observations by a maintenance team leader would be the third step. It is not cost-effective to implement online condition monitoring solutions for every piece of equipment. Look, Listen and Feel (LLF) is an effective condition monitoring technology that detects important signs of machine faults and maintenance requirements just in time, even if an organisation’s offline condition monitoring programme is in place. The idea is to examine, listen to, and feel the machines to determine what they are capable of.

Necessary safety precautions for performing LLF

All employees working in the factory are required to wear personal protection equipment as advised for each installation. Examples – for high noise areas, ear defenders are a must; while eye protection is required in areas where there is a lot of dust, gases, vapours, flying sparks, and so on. In all circumstances, safety shoes must be worn. When working on electrical panels and equipment, wear rubber-soled shoes with fibre-reinforced toes. Individuals must only be deployed for such duties after passing certification tests in safety and equipment capabilities.

Visual inspection (Look)

Users and maintainers must be encouraged to conduct a thorough visual check of equipment and systems before putting them into service each and every time. Such a visual check might show signs of oil or lubricant leaks, overheating related decolouration of protective paint, corrosion spots, broken components, missing items such as belt/chain protectors, dust and debris accumulation, physical blockage, and so on. The equipment or systems will be more reliable if all irregularities are removed before they are used.

Auditory inspection (Listen)

This is mostly true for machinery that has moving parts (motor driven pumps, fans, compressors, etc). The equipment may make an audible rattling noise due to lose components or sub-elements. These might result in serious harm if left neglected. This inspection necessitates considerable competence on the part of the operator or maintainer, as well as a long period of interaction with the equipment. The operator or maintainer must learn ‘what to listen for’ and how to recognise ‘wrong sounds’. This is based on personal experience. In the long run, an operator will be able to detect a change in noise caused by blade wear at a motor bearing or a fan air cutting noise, for instance. It may be subjective at this stage, but before severe harm occurs, examination for more precise data may be conducted.

Inspection through touch and smell (Feel)

Safety is very important as the ‘feel’ actions are generally done on running equipment. It’s important to avoid putting your palm too close to moving parts. The feel gives some idea on the difference in temperature, non-visual vibration level changes, flow quality, etc. Presence or absence of flow, presence or absence of liquid in containers and pipes, weight and lightness of objects, rigidity and flexibility of objects, changes in velocity, etc. The human nose can discriminate different smells. For example, the smell of burning oil in a diesel engine has a very different odour. So, the nose can act as a reliable sensory organ in equipment / system condition monitoring.

LLF comes under the element ‘mechanical integrity of process safety management’.

Implementation of Look, Listen and Feel (LLF)

First, we must identify the unit’s important PSM equipment. PSM critical equipment is any piece of equipment that, if it fails, might result in a loss of containment or a process safety event. Safety, regulatory compliance, cost, and operational throughput are all impacted by critical equipment. Vessels, machinery, pipes, blowout preventers, crucial valves, flares, alarms, interlocks, fire protection equipment, and other monitoring, control, and response systems are examples of this type of equipment.

Depending on the industry or equipment, LLF observations may change. Plant reliability will always be related to the efficacy of the care provided by the operators and maintenance employees who operate on the plant, regardless of the policies and programmes put forth by the management. We can save lives (by preventing accidents), money (by reducing maintenance costs), quality and productivity (with on-time maintenance).

LLF in a solar manufacturing plant

LLF is especially important for a solar manufacturing plant
like Goldi Solar.

  • Look: Stains in the cell cutting, lamination machine, pre-lamination machines indicate an underlying problem; it will also help us check if we are getting the required output. At the pre- and post-lamination stages, visual inspection is required to check if there are gaps or cracks in the module. The stringers connect several cells together. Soldering flux is a chemical component that is used in the making of string, and is also highly flammable chemical. The drum and the place where the soldering flux is stored need to be checked for any abnormal smell, as the vapour in the atmosphere can catch a spark causing fire explosion.

  • Listen: Machine operators should know about look, listen and feel. Those who are in the routine shift engage with the machines for eight hours every day. Any noise abnormal sounds, activities or movement can be discerned by the operators by playing close attention to sounds.

  • Feel: If the temperature or vibration of the machinery is too high, machine needs to be checked for optimum functioning. In case of chemical leakage during transportation of the flux, it needs to be addressed immediately.

The LLF inspection might be made more systematic with the use of appropriate signs put in important spots. Place images of eyes in areas where visual examination is required. The listen and feel activities would be represented by images of ears and palms. In addition, station markings arrows might be painted on the ground to indicate which positions the operator or maintainer should take and which way they should face the equipment to observe it. Arrow marks might be added to indicate the direction to be taken while making the observations.

Courtesy: Goldi Solar

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