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Fan array keeps Mary Rose project ship shape

It’s not often you get to see something completey different, but when you go behind the scenes of the conservation site of the 16th Century Mary Rose in Portsmouth’s historic dockyard that’s exactly what you get. The purpose-built museum housing the Mary Rose is relying on the latest in fan array technology and humidification to provide a controlled environment to help preserve the vessel and its artefacts for future generations

Three air handling systems using Fanwall Technology, four further Moducel LKP air handling units and three Vapac humidifiers are being used to provide comfort cooling for the galleries. The air handlers using patented array technology are specifically being used to continue the drying out process for the Mary Rose and its continued conservation.

For the past 10 years the ship’s timbers have been protected by polyethylene glycol spraying. The ship hall was closed to the public in 2009 whilst the new museum was constructed around the ship. It has now entered its final phase of conservation which will take a further four to five years.

During this time almost 100 tonnes of water will be extracted from the timbers, while the hull is contained in a purpose-built ‘Hot Box’ within a new elliptical shaped museum.

Windows have been installed in the Hot Box with viewing galleries running the length of the ship aligned with each deck level. Many of the 19,000 artefacts recovered with the ship are on display. Once the drying process is completed the hull will contain approximately 12 per cent of moisture. The glass will be removed and visitors will enjoy open views of the hull.

Specifying an effective air handling and humidifier solution was not without its difficulties. Space constraints dictated that any solution would need to be situated in the west dock plant room of the museum with the bulk of equipment in the dry dock, where access was limited.

The critical nature of the museum required 24/7 operation, built in redundancy, low noise levels and crucially a small footprint and modular construction.

The Mary Rose Trust looked at several options including an N+2 solution, but this proved costly and unworkable because of the location and restricted space.

“Access, limited space, size constraints and 24/7 reliability were key considerations,” comments Professor Mark Jones, head of collections at the Trust. “The museum cannot be disrupted. We required a robust solution that could offer N+1 redundancy, facilitated ease of maintenance as well as Part L compliance.”

“Any plant failure would be detrimental and put undue stress on the timbers. We adopted a ‘what-if’ approach with Eaton-Williams. It was essential any solution could not be compromised.”

“Fanwall’s unique technology, using small diameter fans in an array (six in each unit) instead of a single fan used by traditional air handlers, ensures that when a fan fails the others will compensate and if any of the other AHUs fail the remaining systems can operate at a greater capacity to ensure that the preservation process continues uninterrupted.”

The units were constructed at Eaton-Williams plant in Stoke-on-Trent and rigorously tested for air leakages and volume testing.

The systems were then dismantled and delivered to the site where they were constructed in the dry dock. The fragile nature of archaeological wood requires a stable climate. The hull is subjected to 54 per cent RH with a temperature of 19ºC. The Fanwall systems will be used to provide a close controlled environment throughout the museum once the drying process is complete.

The Eaton-Williams Fanwall systems used to facilitate the drying process provided an initial drying duty of 8.33m3/s with an expected final duty of 7.5m3/s and a standby duty of 12.5m3/s. There are heating and cooling coils in three sections and even at peak duty only two out of three coils are required to meet the load

There are also four LKP units which provide the galleries with comfort cooling at 18-24°C with ambient RH, with duties ranging from 1.92m3/s in the east gallery, to 2.16m3/s in the west gallery.

The three Vapac units installed in the ‘Hot Box’ provide ultra close control humidification. These systems along with the Fanwall provide a conditioned environment with a design criteria of19°C+/- 0.75°C with 54 per cent RH +/- 4 per cent. All systems are tightly controlled by a sophisticated demand-led building management system.

“The temperature and humidity will continue to be very carefully controlled using Fanwall and Vapac humidifiers, even when The Mary Rose is fully dried out, to ensure that all the artefacts are preserved in perpetuity,” says Professor Jones.

The Mary Rose: A work in progress

The Mary Rose was built between 1509 and 1511. She was one of the first ships able to fire a broadside, and was a favourite of King Henry VIII.

The 17 years’ treatment to conserve the ship’s timbers by spraying with polyethylene glycol was completed in 2013. It will take a further three years for the ship to dry out.

The new museum building was conceived as a finely crafted, wooden jewellery box, clad in timber planks in response to both the structure of the original ship and HMS Victory. A balcony to the west offers a vantage point over the Royal Navy dockyard and its many 18th and 19th Century Grade 1 and 2 listed buildings.

The Mary Rose Museum is a time capsule through which visitors can take a unique journey through a slice of Tudor England. Journeying through the 1,700m² of gallery space across three floors, visitors can learn the history of Henry VIII’s favourite ship, experiencing her tragic sinking in 1545 (after 34 years of successful service) and the lives of the seamen and officers who served on the Mary Rose. Real artefacts combined with the exhibits enable the treasures to be placed in context within the ship.

8 July 2014

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