Saving money on HVAC in a classified medical devices facility
An international Medical Devices manufacturer wanted to reduce their energy costs and carbon emissions to ensure their UK operations remained competitive in the global market. It is well known that HVAC typically accounts for 50-75% of a clean-rooms electrical energy use. Energy & Carbon (E&C) energy reduction expert investigation of actual v required classification showed the existing HVAC serving the clean-rooms was over-performing, which suggested the extent of air supplied to the facility could be reduced. Room pressures and airflow cascade were also excessive which provided the opportunity to consider reducing the fresh air demand by reducing leakage.
The primary objectives of this project, defined by the QA & Engineering stakeholders were;
- Ensure required particulate and microbial classification was achieved
- Ensure room pressure differentials were compliant
- Ensure comfort levels for operatives remained unchanged
- Ensure implementation works could be undertaken over a weekend, without impacting production plans and avoided the need for a deep clean
- Ensure payback for works were < 12 months
In order to ensure airflow reduction opportunities where valid, a detailed FOA (facility operational assessment) was carried out with the QA and Microbiology departments to ensure critical process, production and people issues were fully understood and sanity checked. Once this had been done, HVAC performance assessments were undertaken to identify the gap between required and actual airflow rates and corresponding room air-change rate and critical room classification and operating requirements.
- Existing air-change rates were between 30 – 50 ac/hr
- Room classification “at-rest” were in some cases, 10 – 100 times cleaner than required.
- Operational cleanliness levels were cleaner than required
- Clean-up times were seconds rather than minutes
- Heat gains from people and equipment were lower than original design allowances
- Production processes were manual in nature
This initial works identified significant energy reduction opportunities could be achieved at very low cost without affecting critical process, people or production requirements.
Risk v Benefit
Before any works were undertaken, key stakeholders from QA, Production, Engineering facilitated by E&C undertook a detailed business risk assessment of the detailed implementation plans for airflow and room pressure reduction. The outcome of this was negligible risks to business continuity, however, as a safe guard, no works would be done which were irreversible and the time plan for the implementation works included a day for reinstating original operating settings. Also before any works were done, airflow, differential pressure, temperature, humidity, particulate and microbial data was collected two weeks before the work was undertaken by E&C engineers and validation specialists. This data collection would be continued for up to two weeks after to ensure key requirements were achieved. Upon completion, the rooms would be revalidated and signed off and then a deviation would then be written by QA to reflect the agreed changes.
- Airflow reduction
- Differential pressure reduction
- Cascade airflow reduction
- Small reduction in airflow equates to large reduction in fan power hence energy savings,
meaning airflow reduction can be optimised rather than maximised whilst still delivering
target cost and carbon reduction.
- Room classifications remained virtually unchanged
- Fresh air reduction was achieved which resulted in further savings in heating and cooling energy use
Other factors to consider
- Ensure fan motor speed is above the minimum to avoid stalling / over-heating
- Limit inverter turn-down to within manufacturers recommendations
- Limit airflow reduction to ensure repeatable duct traverse measurement
- Check BMS and controls hardware operating range settings to avoid operating too close to limits
- Ensure DX cooling system capacity steps are controlled to prevent icing due to reduced airflows across coils
Running costs can be reduced without excess risk or compromising critical process, people and product issues. This is possible because clean-rooms have been over-performing for years due to belt and braces design and operations. Success cannot be achieved without collaboration between internal stakeholders in QA, Engineering, Finance and Safety working hand-in-hand with experts in
HVAC energy reduction, commissioning and validation.
With E&C at your side success is just a step away
Nigel D Lenegan – MD