Optimising Process Cooling During Warm Weather

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Chris Smith, Head of Temperature Control for Aggreko Northern Europe offers advice to managers seeking to optimise process cooling performance and avoid system breakdowns this summer.

Four steps to help ensure optimal process cooling during the summer

By Chris Smith, Head of Temperature Control for Aggreko Northern Europe

Summer is here, putting pressure on the process sector as managers face the challenge of ensuring reliable cooling plant for their production facilities.

Hotter weather can overburden cooling plant at manufacturing and processing sites. For every extra degree in ambient temperature over a designed specification, the cooling kW output of refrigeration equipment reduces. This can make it difficult to maintain required temperatures and kW cooling capacity during warmer weather.

As a result, cooling plant, such as chillers, heat exchangers or cooling towers can be prone to breakdowns. This is a particular risk for sites with older equipment and where servicing and maintenance is not as robust as it should be. System failures can lead to a halt in production, damaged supplier relationships and consequential financial losses.

1. Keep up service and maintenance regimes

In Europe, new chillers are generally rated to handle ambient temperatures at 30/35°C, but their efficiency can swiftly decline if you fail to keep on top of service and maintenance regimes. These should be more than merely changing the oil – it’s important to pay particular attention to refrigerant, circuits and condensers too, or there could be problems ahead.

Maintenance should include thorough cleaning and regular maintenance of condensers to ensure that they continue to operate efficiently. Higher ambient temperatures will put a strain on condensers as they work harder to reject excess heat.

They will also need special attention if, over the year, attempts have been made to increase cooling by spraying them with water. Over time this destroys the fins, resulting in major capacity loss, even during the cooler winter months.

Heat exchangers are also prone to fouling or corrosion problems. These are difficult to spot and can develop gradually, or appear without warning. This is more likely when production is pushed to its maximum, such as in summer peak seasons.

During the hot summer months fouled heat exchangers can also limit a process unit’s operation and cut down on efficiency. This is because process units experience cooling limitations due to warmer cooling tower water, or because dry coolers using the warmer ambient air become less effective.

If a plant isn’t maintained to work to its full capacity and fails, it can mean shutting down a production line, resulting in capital expenditure running into the tens of thousands.

Complete replacement of a chiller system or heat exchanger can take months. Regular, general equipment maintenance schedules should also include preventing system leakage, e.g. the plant refrigerants, control calibration, electrical checks and water treatment.

Rental equipment can support production and cooling during maintenance and servicing, thereby minimising downtime and ensuring production quotas are met.

This is the approach taken recently by a leading food manufacturer, which needed to refurbish its chiller system. Aggreko installed a complete cooling rental package, including 800 kW chiller, 750 kW heat exchanger, 3-way valve, process pumps and generators for power.

Once up and running the customer took their existing cooling process offline, enabling them to carry out the repairs with peace of mind that their produce would remain in optimum condition at the required temperature.

2. Check past efficiency data

It's important to learn lessons from previous summers by reflecting on past experience. If there were any minor issues last summer, there’s a likelihood that these will reappear as major issues this year. Examine historical system efficiency data and trends to check how your refrigeration equipment coped with higher ambient temperatures.

If you saw dips in performance then you may need to act soon to ensure the system hasn’t deteriorated over the past 12 months. Use this to analyse risk and build a robust risk management strategy.

3. Make sure you have sufficient capacity

You may have expanded your production lines, manufacturing facilities or cold storage areas without increasing your refrigeration capacity. Your current plant may also be starting to deteriorate in performance. During winter months the existing cooling infrastructure might suffice, but higher ambient temperatures over the summer may highlight the insufficiency of your cooling capacity.

This indicates that it might be time to think about upgrading or increasing your cooling infrastructure. However, it might be difficult to justify this capital expenditure to cover annual peaks in demand that occur for only approximately 20% of any given year.

A more cost effective alternative, therefore, may be to supplement your existing plant with hired-in cooling equipment to manage exceptional summer demands. This will avoid capital expense and has the flexibility to be scaled up or down depending on the site’s demand.

An initial site survey to understand your potential requirements will ensure additional cooling plant can be onsite quickly when required.

If additional temperature-controlled storage is needed during times of peak demand over the summer period, this can also be achieved with rental equipment.

For example, using very low temperature chillers that can achieve temperatures as low as -45ºC, (when combined with air-cooled chillers or cooling towers) allows temporary chilled storage facilities to be created from a standard warehouse.

For example when Five Star Fish, part of the 2 Sisters Food Group, underwent a cold store refurbishment at its Grimsby production site, we installed a complete temporary cooling scheme that enabled a total shutdown of the permanent cooling plant for upgrade and maintenance.

The 150kW @ -18°C scheme used Very Low Temperature Fluid Chillers, combined with air handling units and ancillary equipment to maintain a consistent temperature and ensure the preservation of stock.

4. Have a well-rehearsed contingency plan in case disaster strikes

If your refrigeration equipment breaks down and stops production, every minute counts before you might be faced with discarding valuable stock, letting customers down and sending employees home.

It's critical to have a robust, well-rehearsed emergency plan in place. This will include reactive maintenance and repair procedures to cover every eventuality and a 24/7 on-call process for engineers.

It is also essential to have considered what back-up equipment you may need so you can continue production while your equipment is out of action.

Discussing your needs with a rental temperature control equipment supplier will help build a contingency plan should the ‘worst case scenario’ occur. A reputable supplier will spend time with you on-site, understanding your needs, identifying the most suitable equipment to meet them and producing a detailed site plan.

This should take into account specific technical, logistical, safety and training issues, so everything is considered and planned for in advance. In this way you can ensure fast and effective installation and commissioning to get the process back up and running as quickly as possible.

You should also agree appropriate lead times and costs for installation and delivery, maintenance and refuelling requirements, as well as decommissioning.

Disaster recovery planning enables sites to implement a transitionary fix quickly, while a long-term solution is found. This level of proactive planning can also reduce insurance premiums over time as it demonstrates your business is doing everything it can to avoid a production shutdown.