Refrigeration: Keeping a cool head

Refrigeration in a plant can always hide hidden dangers. On June 28, employees of Brakes Chilled Food Distribution were injured after an explosion from a chemical leak in a freezer in Tamworth, Staffordshire. The accident came about during routine maintenance by an engineer from a refrigeration contractor.

Refrigeration can also lead to other dangers that might not be obvious at first glance. The Health and Safety Executive (HSE) recently issued a warning about the deterioration of ceilings of frozen and cold stores. Noise can also be a threat to workers' welfare. A survey by the HSE at a food factory revealed that employees who worked in or near refrigerated trailer containers could be exposed to dangerous levels of noise up to 84dB where the main source of noise was the diesel powered refrigeration units.

With all these possible hazards highlighted this year, processors have to get their refrigeration right in order to avoid pitfalls, be they economical or environmental. But what do they actually look for when approaching refrigeration equipment suppliers?

"Because our business is reducing the energy consumption of refrigeration systems the typical first query from meat and food companies is 'what can you do to reduce our costs?" says Gareth Holden, director of energy management company Excalibur LPA. "For many of these organisations the energy consumption of their refrigeration represents 50-70% of their entire energy consumption, so anything that can be done to improve efficiency has a major impact on overheads."

Holden says that initially he would undertake a survey to assess whether the refrigeration system is suitable to be modified and the potential energy reduction. In most cases an improvement in efficiency of 30% is achievable.

Excalibur LPA specialises in improving the efficiency of refrigeration, liquid chillers, pumps, fans and boilers with past customers such as Sainsbury's, Tesco, 2 Sisters Food Group and Samworth Brothers.

Maintain output

Holden says: "Generally it is the site engineering manager who is responsible for energy management. However, his first concern is production and he must be confident that any changes aren't going to have a detrimental effect. From this perspective the modifications are designed with a number of fall back positions, ensuring that no single point of failure has been introduced to the system. In fact most companies report improved reliability following the modifications."

He adds that in many cases Excalibur LPA is able to identify other areas where refrigeration efficiency can be improved. The most common, apart from door management, are dirty condensers and a shortage of refrigerant. "Although cleaning the condensers is a relatively straight forward task it is both messy and time consuming. The correct cleaning procedure could in many cases improve efficiency by 5-10%.

"It is not unusual for service providers to maintain low refrigerant levels. Generally the argument is that if the system leaks it will be identified quicker and less refrigerant lost. The problem is that during periods of high demand refrigeration capacity is substantially reduced, resulting in more compressors operating to do less work."

Most people would think that a 30% improvement in the energy consumption of their refrigeration system was a major success, but Holden says there are other significant areas where efficiency can be improved.

A moderately sized refrigeration system could be rejecting 1,752,000kw of heat a year. If there is a demand for hot water on site, this energy could be captured, reducing heating costs by potentially 40-50,000 per year.

According to WR Refrigeration, a commercial refrigeration contractor, the most common questions it receives are: 'will the refrigeration system/equipment achieve what I want', 'is it reliable', 'what is the back-up if something should go wrong', 'will it save me money and is there another way to do it cheaper?'

Patrick Mullins, business development and marketing director, says: "WR Refrigeration's experience in the food and meat industry enables us to provide clients with bespoke designs to meet individual requirements. All equipment offered is reliable and efficient, we do not look on an order as being a single project but a long-term partnership.

"There are always cheaper way of doing things. However, this involves compromise with inevitable penalties. You have to understand what these compromises involve, and the related penalties, in order to make sensible decisions about plant and equipment."

COMMON QUERIES

Meanwhile, at Chiltern Cold Storage Group, a firm that specialises in bespoke logistical solutions, MD Paul Jackson adds common queries he hears involve: space availability, temperature range, compatibility with other products; and operating standards. Other areas of interest are quality control procedures, traceability, administration with on-line stock, and distribution arrangements.

Chiltern Cold Storage Group has a capacity of 15,500 pallets of frozen and 3,000 pallets of ambient storage at its 8.5-acre site in Peterborough. A range of added value services are available on site including cross docking, freezing and tempering. The firm also offers distribution using its fleet of specialist courier, rigid and articulated vehicles, all of which have temperature data loggers and satellite tracking.

Jackson says: "At Chiltern we can offer the 'total solution' from container pick-up at the port of entry, handling and multi-temperature storage, detailed order picking and nationwide and European distribution.

"Refrigeration plant must be run efficiently with robust controls to ensure regular evaporator defrosts. This together with sound insulation, strict control over door movements and a recognition by all of the cost of warehouse refrigeration will make considerable savings on electricity.

"Chiltern's service offering of a 'total solution' encompassing both storage and distribution has secured business gains with several high-profile meat organisations. This is largely due to understanding the importance of the meat trade, its business expectations, and working in partnership."

WR Refrigeration adds the best way to save money with refrigeration is to use reputable contractors and satisfy yourself they are capable of delivering the requirements in terms of design, installation and service and maintenance. It also says companies should ensure the contractor is using reputable equipment. "Consider the contractor's proposed design carefully," adds Mullins. "A key issue to home in on is the temperature difference across the plant. A large temperature difference permits the use of smaller heat exchanges, reducing plant capital costs, but significantly increasing operating costs. As the person paying the electricity bill over the lifetime of the equipment, you need to be aware of the implications of this aspect of the design. If in doubt, consult a reputable contractor who can guide you through this."

From the contractor's perspective, ensure calculation and design is properly engineered and ensure the offer is compliant with the end user's processes rather than simply based on the contractors experience and abilities.

On a general level, there is no such thing as "best" technology, Mullins adds. The application areas and processes in which refrigeration is used are so varied, it is about providing the optimum solution for each specific situation, taking into account the needs of the customer. "This is where the contractor's experience comes to the fore in identifying the most appropriate technology to suit individual client requirements and expectations." Major installations by WR at meat processing facilities have been at George Adams/Tulip and Kerry Foods.

Training days

WR Refrigeration has also opened its CO2 training academy this year. The facility builds on the company's previous in-house training centre and now includes working examples of all the main types of carbon dioxide systems likely to be met within the field.

This includes examples of sub-critical, cascade and trans-critical carbon dioxide refrigeration systems, all under one roof.

Based on a mini-supermarket format, it incorporates high and low temperature display cases and a fully functioning walk-in cold room. It is said to provide a realistic working environment for engineers to gain both theoretical and hands-on experience of working with the latest carbon dioxide systems.

The centre won a national award earlier this year in the Cooling Industry Awards 2010 for its pioneering work in the field of environmentally friendlier refrigeration.

WR Refrigeration provides regular maintenance and emergency breakdown support to thousands of companies across the UK whose businesses depend on reliable, efficient refrigeration. These include food retailers, meat and food processors, butchers and restaurants.

The company operates a 24/7 alarm monitoring bureau based in Leicester that monitors refrigeration systems for clients across the UK. Breakdowns or potential faults in refrigeration plant are identified and engineers despatched to investigate and remedy problems before they can result in significant stock loss.

In the latest development, the company has also announced it is opening a new production facility in South Wales to produce state-of-the-art refrigeration systems, based on green refrigerants.

The new plant will make compressor packs, condensing units, blast freezers/chillers, portable cold storage solutions and water chillers specialising in natural refrigerants. The systems are ideally suited for use in the meat processing and retail industry.

"Demand for high quality, sustainable refrigeration systems is rising. Clients are looking for high integrity, high efficiency systems that don't depend on HFC refrigerants. They need to be engineered for reliability and based on environmentally friendly refrigerants," says Mullins.

"The CO2 training academy and new manufacturing plant support our business strategy of developing new and promising areas of technology for the future, with a focus on natural alternative refrigerants. It is an exciting area with great potential."


Refrigeration's MOST common failures

l Air Ingress

l Corrosion

l Design Fault

l External Event

l Fire/Explosion

l Human Error

l Impact

l Impurities

l Maintenance Faults

l Over heating

l Over pressurisation

l Structural Failure

l Vibration

l Wrong/Defective Equipment

Source: HSE


Case Study - 2 Sisters and Excalibur LPA

Like most organisations, 2 Sisters Food Group has come under increasing pressure to reduce its environmental impact and control costs.

With this in mind, engineering staff at the chicken products supplier's Haughley Park facility invited Excalibur LPA to conduct an energy efficiency survey of the site's existing refrigeration systems.

Based on this survey and results from an internet-based refrigeration efficiency monitoring system, Excalibur LPA made a number of recommendations and was contracted to carry out modifications to the site's equipment.

Initially the plant's Roast 95 pack was selected for modification. This installation features four Bitzer OSK 7471 screw compressors and an aircooled seven-fan condenser. The system is used to chill cooked chicken and operates seven days a week.

Excalibur LPA undertook the installation of liquid pressure amplification and installed a variable speed drive system to control the unit's condenser fans. The work was done with no disruption to production, prefabrication being completed during normal working hours and final connections made during a weekend shutdown.

The internet-based refrigeration monitoring system used in the initial survey was left in place and this also allows online access to all refrigeration operating parameters. Following 12 months of monitoring, the engineering staff at Haughley Park are now in a position to assess the improvement in refrigeration efficiency as a result of Excalibur LPA's modifications to the system.

Since the improvements were implemented, energy consumption is said to have been reduced by 38%, giving a return on investment of less than 15 months and an annual reduction in carbon emissions of 177 tonnes.

The introduction of low head pressure operation and inverter control of condenser fans has also reduced the mechanical stress on compressors, which will reduce the risk of potential failures, says the supplier.

The entire project qualified for the Enhanced Capital Tax Allowance. A 2 Sisters testimonial said: "Excalibur installed LPA and inverter control to our Bitzer screw pack, the work was completed to a very high standard with minimum effect to production. Monitoring over the first 12 month period showed a reduction in power consumption of 38%. Several evaporators which had been starved of refrigerant now achieve temperatures where previously they struggled.

There have been no reliability issues and we are benefiting from a system which is not only energy efficient but also provides improved refrigeration performance."

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