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Cutting edge designs and technology for flagship facility

© RACA Journal | Benjamin Brits

Image credit: © RACA Journal | Benjamin Brits

By Ricardo da Silva, mechanical engineer at Spoormaker and Partners

The greenfield 427-bed Alberton Netcare Hospital will add capacity in multi-discipline and specialist medical services for the local and surrounding communities.

The original inception and concept phase of this project began in 2011 when Netcare started exploring options in refurbishing the Union Hospital located in Alberton, Gauteng. After various design and feasibility iterations it was decided that a new greenfield facility would be needed in order to reduce the operational impact of the current facility while providing a blank new canvas for which Netcare could roll out their newest design philosophy.

The original premise of the project was to combine the Union and Mulbarton Hospitals into the new facility, while also incorporating a few beds from Clinton Hospital. All three hospitals serve the Alberton area and are critical to Netcare’s operational focus.

Images: © RACA Journal | Benjamin Brits

Concepts on the revised scheme began in earnest in the beginning of 2016. Considering the need by Netcare to create a flagship facility, there were numerous engineering workshops that refined the proposed design.

Earthworks began in late 2019 with the mechanical sub-contract tenders (HVAC and Medical Gas) awarded in June and Sep 2020 respectively.

Practical completion of the facility was achieved in February 2022. This included the project being severely affected by the COVID-19 pandemic, and associated nationwide shutdowns.

The hospital officially opened its doors to the public on 11 April 2022.

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Design specifications/client brief

As mentioned in the preceding section, the client wanted to create a flagship facility that showcases their design philosophy and the efforts they have made in furthering their sustainability initiatives.

Netcare have focused heavily on optimising the energy usage of their facilities and look to an average of 35 VA/m2 of total energy usage on gross lettable area. On the HVAC scope, heat recovery systems would play a major role in obtaining an energy efficient building.

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During the course of the project the client brief changed due to the global impact of the COVID-19 virus. The HVAC system in all hospitals plays a major role as a first-line defence in the containment of airborne pathogens of this nature. As such, various design changes were implemented in order to prepare the hospital for future outbreaks.

The HVAC system and installation

During the concept design phase, two options were presented to the client for review. This included the use of a 4-pipe chilled water plant and a de-centralised variable refrigerant flow (VRF) system. The 4-pipe chilled water solution made use of hot water instead of electrical elements to provide terminal level heating for all variable air volume (VAV) ducted systems.

The client opted for the de-centralised VRF system due to the familiarity and success they have encountered with similar installations at their other facilities.

This facility was effectively divided into two sections. The clinical areas (which included general wards, ICU/HCU’s, emergency department and radiology) that are served by ducted VAV air handling units (AHU). These AHU’s provide primary and secondary filtration to the area whilst also optimising the opportunity for free cooling by engaging economy dampers which increase the fresh air flow rate. The AHU’s are coupled to a heat recovery VRF condenser located on the roof. Each clinical area is served by one AHU-VRF condenser combination in order to improve redundancy across the facility.

The other areas of the facility (which included doctors suites, back of house/technical departments and administration offices) are served by a conditioned fresh air unit with VRF cassette units for each space. Each refrigerant control box has been selected to have 20% spare ports available in order to expand on the system if required. All refrigerant lines have been equipped with high quality shut off valves (tested to 45-Bar) to enable separate branches to be isolated without shutting off the rest of the system. As with the clinical areas, the unitary system has been sub-divided into block and floor-specific zones in order to improve redundancy.

There are 11-of ISO Class 7 and 4-of ISO Class 5 operating theatres within the hospital. These are also individually served by air handling units with humidity control that are equipped with high efficiency particulate absorbing (HEPA) filters.

Images: © RACA Journal | Benjamin Brits

The HVAC infrastructure is also utilised to provide hot water generation on site. This is achieved by integrating the hot water plants located around the facility into the VRF heat recovery infrastructure. As hospitals are predominately in a cooling only mode this provides tremendous amount of opportunity to utilise heat recovery technology. There are five de-centralised hot water plants across the facility and each plant is made up of two heat accumulator tanks. Each tank is coupled to 2-of booster units and 1-of heat exchange (HEX) units that are connected to the closest VRF system. Each tank and its sub-components can act independently if maintenance is required on the other set.

There are also numerous isolation rooms located within the facility which are served by standalone extraction systems that ensure correct air pressure cascading at all times in order to protect both the patient and the staff. In addition, all isolation rooms are monitored by a separate control system which continuously measures the air flow within the treatment room and provides both a visual and audible alarm should the correct conditions not be maintained.

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The basement ventilation system comprises of large axial extract fans and numerous centrifugal jet movement fans. These movement fans push the air into these large extraction zones that are then vented to atmosphere on the ground floor. The fans are linked to carbon monoxide (CO) monitors and are controlled by the average reading across a number of de-centralised zones. The entire basement ventilation fan system is also fire rated as they provide a secondary function as a smoke extraction system in the event of a fire within the space.

As the COVID-19 pandemic unfolded across the world more facilities are looking at being prepared for future outbreaks. Netcare requested that Spoormaker and Partners as the mechanical consultants, investigate design interventions that can be implemented during the construction of the hospital that will enable the facility to be better equipped to handle the different operating parameters that are required in these instances.

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The following HVAC design interventions were implemented:

Figure 1: normal mode. Image credit: © Spoormaker and Partners

Figure 1: normal mode. Image credit: © Spoormaker and Partners

Figure 2: pandemic mode. Image credit: © Spoormaker and Partners

Figure 2: pandemic mode. Image credit: © Spoormaker and Partners

Wards

  • Wards and other clinical areas served by a ducted system (except the ICU’s and theatres) are designed to go into full fresh air mode during a pandemic period.
  • A minimum of 6 air changes per hour (ACH) is provided into the spaces.
  • Standalone extract system will serve each area enabling the ward/department to be under negative pressure.
    • Extract grilles will be placed at the furthest point from the entrance door in order to create the required pressure cascading/air flow direction.

Typical schematic of airflow during Normal and Pandemic modes is shown below:

ICUs

HEPA filters have been shown to be effective in reducing the viral load of airborne contaminants with multiple passes. This coupled with an already high total air change within the ICU/HCU provides an efficient alternative to running the AHU on full fresh air. The following was implemented in these areas:

  • All AHUs fitted with HEPA filtration.
  • All isolation room fans will be switchable enabling protective and infectious isolation protocols.
The HEPA filtration housing on air handling units. Image credit: © Spoormaker and Partners

The HEPA filtration housing on air handling units. Image credit: © Spoormaker and Partners

Difficulty in meeting design specification/Solutions

The only element that provided some challenges in this project was the implementation of the COVID-19 design interventions. The technical solution was relatively straightforward, however arriving at the correct result took considerable research given that the information around COVID-19 and HVAC infrastructure was continuously evolving and insignificant research was present at the time.

In the end, the solution that was implemented is still regarded by ASHRAE, and other international bodies, as one of the best design interventions that can assist a facility with providing increased levels of safety for air borne virus similar to the coronavirus family.

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Products used in the project

As with all product selections, a reputable and well known product is always sought out for a project of this magnitude. The client cannot afford the risk in implementing untried and untested products on such a scale across a flagship facility.

The two largest HVAC products implemented were the air handling units (46-of) and VRF system (566 indoor units, 104 condensers). These two products were individually tendered to the industry with TROX SA and Mitsubishi Electric Airconditioning winning the tenders respectively. The total VRF cooling capacity is 2.2MW.

The combination of feasible capital costs, a quality product, and intensive local technical support meant that the client had no reservations in appointing each supplier.

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Impact of the HVAC system on electrical usage

The electrical efficiency of the facility was one of the leading priorities for the client in order for them to achieve their sustainability benchmarks. As noted, heat recovery was extensively used (where possible) and forms the backbone of achieving the lofting goals as required for this facility.

The simulated heat load model for this hospital (annualised) is 10.5 W/m2 for HVAC energy usage across the entire site. Currently, the hospital is operating within 10% of this which bodes well in that the implemented design closely follows the simulated model.

Special/unique elements of the project

The hospital has unique structural design elements in order to operate as a post-disaster function facility. The site is built under a special structural classification – both in reliability and in consequence. The facility design as such effectively means that in the event of a 1 in a 100 year natural disaster occurrence such as flooding the facility will still be able to function and provide service to the population.

The structure is also designed and classified as a high risk category. This means that the structure is able to withstand seismic loads (which can be present in the East Rand of Gauteng) and remain standing even if a column is damaged or fails.

The are 24 vertical shear walls dotted around the facility. These are 10-meter-wide reinforced structural concrete walls that run uninterrupted from 5 meters below ground to the roof level. The ground beams are tied to the shear walls to create a rigid structural matrix.

Figure 3-6: Extracted from Federal Emergency Management Agency America
Figure 3
Installation of additional transverse bracing as necessary to stay within maximum transverse spacing limitations.
« of 4 »

This obviously has an effect on the in-ceiling services which also need to be secured in the case of a seismic event. South Africa does not have prescriptive guidelines for seismic restraints so the professional team used guidelines developed by the Federal Emergency Management Agency in America. These guidelines provided information on support details for various HVAC equipment as highlighted in the schematics Figure 3 and Figure 4:

Other interesting features – digital hospital:

  • Alberton Netcare Hospital is the first facility in the Netcare Group to be fully digitised.
  • There are 24 de-centralised server rooms within the hospital with a disaster recovery installation off-site.
  • The site has a N+N cooling configuration.
  • All clinical areas are access controlled via personalised access keys – the movement of all personnel can be tracked in real time. This is helpful to check rotations and time of care metrics that are important to Netcare.

List of professionals

Project name Netcare Alberton Hospital
Owner Netcare Limited
Architect/Designer A3 Architects
Project manager Profica
Consulting engineer Electrical BFBA
HVAC & BMS Spoormaker and Partners
Medical Gas Spoormaker and Partners
Wet services IX Engineers
Civil WSP
Contractors Main building Trencon
HVAC & R Airgro
Medical gas Drager
BMS Satchtech
Wet services Thermowise
Electrical Presto
HVAC and associated product suppliers AHU/FAU Trox
VRF Equipment Mitsubishi Electric Airconditioning
DX Equipment Mitsubishi Electric Airconditioning
Diffusers Rickard
MCC Merlin Engineering
Humidifyers Condair/Humidair
Jet Fans Systemair
HEPA Guages Dwyer
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