A new generation
Process 04
Dave Bird explains how packaged plate heat exchange technology can support clean in place and washdown processes by providing increased energy efficiency, carbon reduction and a reduced risk of legionella.
Steam is essential in the food industry but it must be delivered safely, reliably and efficiently. With increasing pressure to reduce energy consumption and improve safety, operators must evaluate the costs impacting their processes and determine new ways to offset them.
Food manufacturers are large consumers of energy, meaning energy costs will always represent a high proportion of their overheads. Hot water must be generated on a daily basis for washdown and clean in place (CIP) processes, but if not delivered in a safe and efficient way, this can have a significant impact on costs – making it an area worth exploring when it comes to maximising energy savings.
Traditionally, the food industry has relied on large shell and tube calorifiers that use steam to heat water. These are inherently inefficient, however, and can increase the risk of legionella. Conventional shell and tube heat exchange systems have been a source of frustration, with many energy managers, maintenance engineers and health and safety officers unaware of the full extent of these inefficiencies, or how they can be remedied. So how is it possible to minimise these risks, while improving energy performance?
The legionella risk
Those that rely on calorifiers to provide hot water for CIP and washdown processes could be at risk of legionella.
As a water borne bacteria that can grow in engineered water systems such as cooling towers, condensers, as well as hot and cold water systems, legionella poses a degree of risk which needs to be mitigated. Protecting against a legionella outbreak is a legal requirement for any organisation, which must also be responsible for maintaining the health and wellbeing of its staff, as well as those customers it may come into contact with.
Legionella itself is always present in a water supply, so eliminating it completely isn’t the aim. Controlling the risk, however, is a fundamental objective for any food manufacturer – particularly those with a reliance on hot water for CIP and washdown.
As a calorifier is, in simple terms, a large storage tank capable of generating heat within a mass of water, it not only poses a legionella risk, but also radiates heat which therefore limits efficiency levels.
A new approach
Rather than remaining loyal to a storage-based system which has a number of logistical weaknesses and cost inefficiencies, manufacturers should view the use of packaged plate heat exchangers as a potential way to lessen these concerns. A packaged plate heat exchanger is essentially a plate heat exchanger within a very compact housing – generally around a third of the size of an average calorifier. This not only saves space, but also boasts the ability to deliver hot water instantaneously, eliminating the need for large quantities to be stored in calorifiers. They offer increased energy efficiency, carbon reduction and health and safety benefits, when compared with traditional calorifier systems.
Systems like these can be easily implemented, helping plant operators improve overall plant safety, reduce energy costs and usage, increase efficiency and remain competitive in this demanding market. Furthermore, plate heat exchangers are easier to maintain and simpler to control, which helps keep the system running at optimum efficiency.
Waste not, want not
By replacing these storage tanks with instantaneous systems that use compact heat exchangers, plants can achieve energy savings of up to 20 per cent. These systems work by capturing and reusing heat, which may otherwise be wasted, to deliver a constant supply of instantaneous hot water at a stable temperature. This reduces the amount of steam required, which in turn cuts fuel demand and the associated CO2 emissions. Given that a reliable and safe supply of hot water is crucial for washdown and CIP processes, optimising the generation of hot water could be the best way to save money.
At your service
When relying on storage vessels for hot water, annual insurance inspections are required to ensure each vessel’s condition is compliant, its welds are secure and pressure levels are acceptable. While this is a perfectly reasonable requirement from a safety point of view, the fact that an inspection requires the vessel to be drained with the heat transfer coil removed, means the calorifier is out of use for a set period of time. The plant also needs to have the space available for this procedure to take place, which generally requires double the length of the coil itself as available space. This is a requirement that the prepackaged alternative simply doesn’t have.
While the packaged plate heat exchanger certainly doesn’t eliminate the need for annual servicing, its requirements are much simpler to manage. As with any water heater, a certain level of scaling can occur depending on the given site’s water treatment regime, which makes it vital that an annual service is carried out on site.
The servicing procedure itself, however, is a lot simpler than servicing a calorifier in that it generally involves a check of the plates, which can be done by sliding them along the frame of the unit. For those more eager to take a ‘fit and forget’ approach, the investment in a manufacturer’s service contract will make annual servicing a simple enough routine to maintain.
Knowledge is power
Understanding exactly what can be gained through the replacement of a calorifier with a packaged plate heat exchanger is important. That said, the benefits will only be realised fully if staff on site have an in depth knowledge of how they need to manage the risk of legionella and apply relevant legislation within their day to day duties.
The first step before any investment in equipment is made should be ensuring that anyone tasked with operating a boiler plant or plant room has attended a legionella awareness course. Offered by specialists such as Spirax Sarco, a one-day training course can be a simple way to ensure plant operators all have the same level of knowledge to call upon when it comes to identifying roles and responsibilities and, ultimately, applying measures to control the legionella risk. From there, ensuring the heating and hot water systems on site do the same job should be the next logical step.
By avoiding such a heavy reliance on stored hot water, the producers are able to improve energy efficiency and dramatically cut their costs, all the while improving safety across the board.
Author
Dave Bird is food and beverage sales manager at steam management systems manufacturer Spirax Sarco, which works alongside global steam using organisations to help them improve productivity, save energy and reduce waste.
