16 April 2020
How Resource Data Management (RDM) helped a HT cold storage expansion for a leading cheese manufacturer
Quality and consistency are a priority for foodservice supplier and cheese manufacturer J.S. Bailey. Committed to creating a facility that meets the highest standards, increases production and drives business growth, in 2019 it invested £3m to expand the production facility and create a 1000-tonnes capacity, purpose-built storage unit.
Robust controls are embedded at each stage of production at J.S. Bailey. The expansion project delivered by Personal Refrigeration mirrors this with the installation of a high-tech refrigeration plant complete with custom control algorithms to serve multiple high temperature (HT) areas.
The design focuses on precision control, reduced operating costs, increased system longevity and user-friendly functionality to ensure the greatest possible payback. Personal Refrigeration wrote the control strategy using RDM’s PLC software, TDB. New features and technologies were integrated into the design to provide energy-efficient, cost-effective and environmentally-friendly installations. HVAC controllers with PLC software – the Intuitive TDB range – were used to control pack, HT evaporators, HT steppers, heat recovery and frost prediction.
Two identical HT refrigeration packs, each utilising three Frascold semi-hermetic compressors, serve several evaporators within the storage, holding and production areas. The high-efficiency evaporator coils reduce the refrigerant charge by 15%, minimising the system’s environmental impact. Sharing the load between two packs provides contingency, eliminating costly downtime and product spoilage due to a single point failure.
A quad circuit heat recovery tank supplies hot water to various factory processes using an anti-legionella flush program as necessary. The installation benefits from inverter-driven compressor PLC algorithms, with fully independent compressor modulation for step-less and seamless loading from 11–77 kW per pack. The refrigeration plant precisely matches the ever-changing real-time load conditions, which ensures that only minimal energy is consumed. System head-end DMTouch monitors all control devices on-site, analyses energy consumption, and predicts running costs.
Custom software programme
Dual adaptive PID loading/unloading algorithms measure real-time load demand and react accordingly to the current suction pressure set point. Initiation of the refrigeration pack loading ensures that the compressor with lowest run hours is always selected to start first via the primary PID loader. The secondary loader then allows the compressor modulation algorithm to run, modulating through its range to satisfy the setpoint suction pressure. In turn, the primary loader will continue to run in the background, monitoring the load and starting another compressor when the full modulation of the running compressor is reached.
An additional compressor will only be allowed to start if the set point suction pressure cannot be satisfied utilising the running compressor whilst modulating through its range. The compressor modulation algorithm will then consider the independent compressors that are operational. This is performed over a cyclic period.
- If load increase is required, the compressor with the lowest frequency will be increased in speed, providing more refrigeration capacity.
- If load decrease is required, the compressor with the highest frequency will be decreased in speed, reducing refrigeration capacity.
The dual adaptive PID loading system also ensures that compressor wear and tear remains even whilst running in reverse. Compressor stop will be initiated only when modulation of running compressor(s) is below a set threshold, the compressor with the highest run hours will be turned off first. Constant adjustment of compressor modulation also balances the operating compressors’ running frequency and running hours via the primary loader.
The dual adaptive loading system ensures both step-less and seamless load matching, and more importantly, provides the end-user with energy savings during plant operation. Energy savings for this site as a whole have been estimated at 30%, by analysing compressor running times, reduced system load and defrost costs.