Munters help RAF beat long-term threat of corrosion

Citation

(1998), "Munters help RAF beat long-term threat of corrosion", Aircraft Engineering and Aerospace Technology, Vol. 70 No. 1. https://doi.org/10.1108/aeat.1998.12770aaf.005

Munters help RAF beat long-term threat of corrosion

Munters help RAF beat long-term threat of corrosion

In its 79 year history the RAF has achieved a reputation unparalleled by any airforce in the world. Indeed, if it wasn't for its skill and composure, the course of world history over the last 60 years may well have taken a different route.

The Lufiwaffe was one thing, but there are some enemies that even the RAF cannot defeat alone. That's why when high humidities threatened to cause corrosion damage to stock in its storage facilities, the RAF called for humidity control specialists Munters UK, a leading supplier of desiccant dehumidifiers.

With over 90 bases and airfields in the UK alone, The RAF manages a massive logistics network, and one of the major links in this chain is RAF Stafford, a storage depot situated in Staffordshire. The base dates back to the wartime days of 1940. It is now used to store spare parts for the RAF's 1,000 plus fleet of aircraft, and is the home of the Freight Distribution Squadron that supplies British Armed Forces bases around the world.

As the RAF's main spares depot, RAF Stafford also stores bulk metal for use in aircraft refurbishment. The metal is predominantly ferrous in nature but there is also an important selection of high value alloys that are prone to corrosion at relative humidities greater than 50 per cent. As large quantities of metals are likely to be stored for long periods of time, it was imperative that a long term solution to moisture damage was found.

Munters' previous experience with the Naval Aircraft Materials Laboratory (NAML) has shown that the rate of corrosion of metals and alloys used in aircraft is significantly reduced when they are held at less that 50 per cent relative humidity (RH). RH is the amount of moisture present in the atmosphere at any one time; 100 per cent RH means that it is raining and with a UK average of 80 per cent, conditions within the storage units at RAF Stafford have to be tightly controlled.

To control the RH, a Munters MX5000 desiccant dehumidifier was installed in each unit and, since then, daily readings have revealed that RH levels are well within the 43 per cent to 50 per cent target zone. Desiccant dehumidification works by drawing air through a rotor impregnated with either silica gel or lithium chloride, the rotor removes all moisture and the resulting dry air is recirculated into the affected building.

Both dehumidifiers are controlled by humidistats and are able to react promptly to any changes in the ambient conditions. With lower capital installation and running costs, desiccant dehumidification is significantly cheaper than alternative methods such as heating and refrigeration. Also installed in each storage unit is an infra-red heating system controlled by proximity sensors, ensuring cost-efficient heating in the manned areas of both units.

This combination of background humidity control and localised radiant heating was reported to be less expensive to install and has lower running costs compared to the heating scheme with which it was competing at the design stage.

RAF Stafford is believed to be the first such storage facility of its kind within the Royal Air Force which already has a policy of using dry air for the protection of all operational and stored aircraft.

Details from Munters Ltd, Blackstone Road, Huntingdon, Cambridgeshire PE18 6EF. Tel: 01480 432243; Fax: 01480 413147.