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Moving towards predictive maintenance strategies

03 June 2019

Food Processing gets advice on how to move pump systems from preventative to predictive maintenance strategies and what benefits this can offer. 

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The costly and wasteful practices surrounding preventative maintenance could be numbered as industry moves towards predictive maintenance strategies enabled by the analysis of data provided by smart sensors which can be fitted to pump systems.

However, according to Hydrostal, industry first needs to eradicate the complexity that arises from each pump manufacturer having their own bespoke ‘black box’ solution for condition-based monitoring. Each system offers a different set of guidance and instructions to achieve the same goals and this has resulted in confusion and procrastination, in some instances resulting in ‘maintenance paralysis’.

It should be understood that all of these ‘black boxes’ are fed from the same or similar sensor inputs that generate or transmit either a digital (on/off) or scaled analogue signal. An example is run/failed signal from a thermal bimetal strip opening and closing at a preset temperature. Alternatively, a scaled analogue signal that allows bearing temperature to be monitored through a variable resistor or vibration level using an accelerometer, then setup alarm and trip levels.

As long as a pump is fitted with the relevant sensors and the manufacturer provides their range, there are many receivers that can relay the values to a central PLC. This PLC becomes the single data collection hub or your own ‘black box’. From here it is possible to monitor and measure all the pump performance across a site to the required level. Yes, there will need to be interfaces and software, but the advantage is a common platform that can command and control all of your pumps and other machinery, such as compressors etc.

According to Hidrostal the benefit of such an open platform is that there is just one learning curve for operatives and there is no dependence on bespoke pump controls for each pump type, requiring individual training to operate and integrate. Not to mention the built-in-obsolescence of many bespoke controllers. Future proof your command and control system by keeping it on an open and simple platform, advises Hidrostal.

Pumps are not rocket science. You don’t need to be dependent on them, you can control them in the way that best suits your application or process. Pumps should be your assistant, not your master.

A centrifugal pump is fundamentally at an agricultural level of engineering – an impeller that spins on a shaft driven by a prime mover with bearings and housings to secure it. The majority of its maintenance is much the same today as it was 50 years ago. Issues that affect its performance will include vibration and heat. Heat often comes from friction and friction can occur due to wear and a lack of lubrication. Vibration can be born from these same fundamentals. Never underestimate the value of simply lubricating and replacing worn parts at the right time. Taking pump wear as a measure or trigger for maintenance is good practise.

The simplest way to measure pump wear is to monitor the Specific Energy or Espec = kWh/m3.  Alternatively calculate the amount of power it takes to pump each cubic metre of water.  This value increases as the pump wears. The measurement and monitoring of flow and power in a bench mark system condition, such as pump start, will enable this powerful bit of data to indicate the level of wear.

Over thinking maintenance and striving for perfection loses the benefits from good, simple and future proof maintenance strategies. Data not acted on has no value so do not overload yourself. Select just the relevant data that matters to the pump in a given application. Most important of all make sure there is someone to apply grease, change oil and replace fast wearing parts to enable the benefits of maintenance.

Digital benefits
In food processing applications pumps are by far the biggest motor-driven application and ensuring their uptime is critical to avoid lost production. According to Luciano Santos, UK food and beverage manager for ABB low voltage motors, there is a always demand for solutions to increase production reliability “There is a demand for any technology that keeps production running smoothly. If you stop a dairy or poultry production line, the fast spoilage rate means that amount of waste generated can quickly become catastrophic.”

There are several events that can cause a pump to malfunction. Cavitation, for example, causes changes in liquid pressure which threaten the reliability of pump impeller and seals. Furthermore, in the dairy industry cavitation can damage milk-fat globules. Technology is now available to help eliminate this risk. For example, anti-cavitation software built into the current generation of ABB variable speed drives looks for specific patterns in the drive parameters, reducing the speed to limit the risk of cavitation. Among the benefits are improved product quality and impeller lifetime. Potential flow issues are picked up immediately by changes in torque on the shaft. No extra components are needed for the drive and no additional installation work is required.

Many food processors are looking to minimise their water usage during process equipment and pipe cleaning. A variable speed drive can offer Clean-In-Place (CIP) solutions with easy to use pump control software that maintains the correct pressure and flow rate to pipe clean and fill functions. This can help reduce cleaning times and can involve the need for less water and cleaning materials.

Food industry pumps are often located in areas where hygiene is a vital consideration and their shrouded motors can be difficult to clean and may not fulfil these hygiene requirements. Using stainless steel motors, protected to IP69, makes it easier to conform to demanding hygiene requirements. Also for less demanding environments, consider the use of range of paint-free motors.

What cannot be overlooked by the food industry is the fast-moving world of digitalisation. Pumps are a prime candidate for inclusion. ABB Ability Smart Sensor for pumps, for example, can be attached wirelessly to pumps to monitor key parameters such as temperature, vibration and bearing condition – using data analytics – to prevent clogging and other issues. This smart sensor technology for pumps was developed in collaboration with Swiss pump manufacturer, Egger Pumps, primarily for use in wastewater applications, but it is suitable for use with all brands of centrifugal pumps that pump water-based liquids. 

The smart sensor is part of a suite of hardware, software and services – called ABB Ability Digital Powertrain – that targets remote assistance, condition monitoring and predictive maintenance of an installed pump base, leading to higher productivity and lower total cost of ownership. “Predictive maintenance helps our customers avoid unplanned downtime,” said Andrew Bould, UK food and beverage manager for ABB drives. “Real-time performance and efficiency data reassures them that their machinery is running properly and can also save costs by taking the guesswork out of planned maintenance, and ensuring that servicing is carried out where it is needed.”

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