Operation mothball

The World Wars were instrumental in focusing attention on the fact that materials which deteriorate from the ravages of natural atmosphere could be preserved indefinitely in a controlled humidity environment.

Between the two World Wars, the U.S. Navy carried out experiments in preserving ships through surface coatings. These proved totally unsuccessful. Before the close of World War II, the U.S. Navy embarked on an intensive research programme for a practical solution to preserve many ships and military equipment. From this research came the dehumidification programme for providing long-term preservation solutions.

The lessons learned then have been successfully applied over the years and is applicable to this day.

Due to fluctuating economic trends, more and more ships are being put in temporary lay-up status.

If the vessel is not dehumidified during lay-up, in about a year's time, much of the machinery would be inoperable. Paint would peel off bulkheads, electrical equipment would not function properly and circuit breakers would pop on many of the vessel's systems once full power is restored. In fact equipment covered with the best known preservatives and exposed to uncontrolled humidities have been known to deteriorate beyond practical repair under exposures as short as 90 days.

Bry-Air has supplied dehumidifiers to the Marine Industry since 1939 for ship mothballing and other applications such as gear casing lay-up, sandblasting, coating and cargo hold drying.

The areas that need dehumidification are mainly:

a.    Machinery/engine room
b.    Living quarters
c.    Midship dock housed pump room
d.    Steering room

The cool sea water in which the vessel floats leads to temperatures inside the ship which are only 5 F to 10 F higher than the sea water, whereas weather conditions with 90% humidities are probable.

This leads to condensation on all exposed surfaces.

Hence a design condition of 40% RH is chosen as a safe condition at which the main elements of destruction:- corrosion, rot and mildew would be inhibited.

Upon lay-up, a dehumidifier takes about three weeks to dry the ship to design conditions and then needs to run 2-3 hours per day to maintain conditions.

The dehumidifier is controlled by a humidistat which is adjusted according to the relative humidity to be maintained.

Bry-Air has hundreds of dehumidifiers aboard ships, preserving them for years until they are restored to service. The interiors of the ships will look as clean and fresh as on the day the ship was mothballed.
(Reproduced from Bry-World, Issue...)