Ideal Environmental Conditions for Food Production Facility

Foreword

A food manufacturing facility required an HVAC upgrade in two production areas due to an inefficient system in place. Supplying dehumidified air and ensuring accurate food safety conditions were the main drivers of the project. For food safety reasons, the two production areas each have different temperature and humidity requirements but both were to be supplied by one air handling unit (AHU) as part of the upgrade.

Space Engineering Services developed a comprehensive, efficient solution that went above and beyond the scope of supplying the correct environmental conditions. The new system not only ensures food safety standards are met, but also includes additional safety features, facilitates efficient maintenance, and delivers additional data for food safety audits.

The Project

A UK food manufacturing business, accredited to BRC food safety standards, decided to upgrade their HVAC system, specifically the dehumidification process, in two production areas. The existing system created challenging conditions, because the heating coils that were used to dehumidify the air often iced up which led to high energy use.

Ensuring that food safety standards are met remained priority number one for the new system. But it was also essential to find a way to supply the correct environmental conditions more efficiently to lower energy use.

For the new HAVC system, the business specified one new air handling unit (AHU) to supply chilled, dehumidified air at a positive pressure to the two production areas. At first glance, this seems like a straightforward request, but there was a catch: the two areas operate at different temperature and humidity setpoints which means that one AHU would need to fulfil different criteria for each area. In addition, the areas are in use according to different schedules. Sometimes those schedules overlap and both areas are in use at the same time, while at other times, only one area is in use while the other is closed for cleaning.

Space Engineering Services (Space Engineering) were chosen by the food manufacturer to deliver the project. Their solution meets the food safety requirements in both production areas, operates more efficiently, supports food safety audits, and offers enhanced maintenance and safety features.

The Solution

Designing a single AHU to supply two areas

Space Engineering designed a single dehumidifying AHU with a heat recovery circuit for external mounting. The AHU supplies filtered dry air, at a fixed temperature from a water chiller and two cooling coils, via external mounted duct work to the two areas of the factory. Each area is supplied via separate duct work so that the different conditions in each area can be met.

The system is controlled and balanced using duct pressure sensors and flow grids to the areas controlled with dampers regulating the direction of air and rate.

Three port valves were installed for the two cooling coils to maintain the air temperature due to the LPG drying circuit built into the AHU.

A desiccant drying wheel is heated to 110°C to remove the moisture from the air flowing through the AHU from a natural gas burner. The temperature is controlled via signals from the sensors in the duct work. The correct air temperature allows the drying wheel to absorb as much moisture as needed to create the desired humidity for each production area.

Humid air from inside the production areas is diverted outside and replaced with correctly humidified air from the AHU. In the previous system, coils were used to dehumidify the air but they often iced up, leading to inefficiencies and high energy use. The new system delivers correct humidity levels using less energy.

The system ensures that the most important criteria – meeting food safety requirements – is met. It supplies the two production areas with temperatures of 6°C or 8°C, depending on which product is produced. In addition, the new system lowers the entry temperature of the product before it is placed in the blast freezer which increases the efficiency of the blast freezer and reduces energy use.

The new system also takes into account two manufacturing seasons: high and low demand. The system changes the cooling and recirculation settings accordingly.

Intelligent controls & PLC strategies create optimal conditions

Space Engineering selected Resource Data Management’s (RDM’s) HVACR PLC controllers – Intuitive TDB – and three expansion boards due to their flexible nature. The Intuitive TDB controls all end of travel switches for the dampers and receives signals from the sensors in the AHU. The sensors feed back information on humidity, temperature, and duct pressure. A third-party device controls the operation of the drying system.

RDM’s front end control and monitoring system DMTouch was selected to ensure that all parts in the entire system, including RDM controllers and third-party controllers, work together so that the AHU creates optimal environmental conditions in the production areas.

Controlling devices from two manufacturers is made possible by DMTouch’s third-party integration capabilities. Both, RDM’s Intuitive TDB controller and the third-party controller are networked to the DMTouch.

In order for the DMTouch to communicate with the third-party device, Space Engineering created a Modbus template. DMTouch can receive and run commands between both devices. Space Engineering have allowed for a difference in polling rate when communicating between the different devices to ensure that the command and return value result in the correct setting.

Additional safety features for peace of mind

Multiple safety features were included in the design.

The duct work pressure is monitored for safety reasons and efficiency. Sensors inside the duct work send signals to the DMTouch front-end. If the pressure increases past a set threshold, DMTouch will send a signal to the Intuitive TDB to stop the fan.

The same logic is in place to prevent an over-temperature of the burner. A sensor measures the temperature of the burner and sends the data to the DMTouch. If an over-temperature threshold is met, the DMTouch will send a signal to turn off the burner.

Frost protection on glycol will turn off the cooling. Fire and CO sensors, separate to the fire system of the building, are installed in the AHU. Should any fires be detected, a fire suppression system will be activated.

In the case of a power cut, the AHU cycle will restart after a 12-minute time lapse. This is to ensure a safe restart of the system.

Efficient Maintenance Procedures for Smooth Operations

Prompt maintenance is key to ensure that HVACR systems are operating efficiently. Space Engineering included a series of maintenance features in the control and monitoring system that help maintenance staff locate issues quickly and access information to fix them. Automated alarms alert staff if any part of the system is not working properly so that issues can be addressed quickly.

Space Engineering introduced closed network Wi-Fi to allow maintenance staff to see all devices when on site. Alarms will flash red on the touchscreen of the DMTouch. The maintenance team can click on it and instructions will show up that advise them how to solve this issue. This can be accessed  on site and remotely so that maintenance teams can see if it’s necessary to send staff to site or if it is a fix that can be carried out remotely.

In addition, a full test cycle will run every week to ensure that dampers are still operating correctly. If they are not open when they need to be, an automated alarm system will alert staff so that maintenance can be carried out.

Supporting Food Safety Audits

Ensuring food safety criteria are met in the production areas is the first priority of this system. In addition to supplying air at the equired temperature and humidity to meet food safety standards, the system can also support the business during food safety audits. All air temperature data sent from the sensors to the DMTouch is stored on the DMTouch. The data can be downloaded to show compliance for food safety audits. Calibration certificates for sensors can also be stored on the DMTouch and then downloaded for the audit.

Final Results

The single AHU supplying two food production areas with differing temperature and humidity criteria delivers the required conditions more efficiently than the previous system. Additional safety features, maintenance aids, and food safety audit support turn this system into a comprehensive solution.