On deck or dock, in salt-water or fresh-water atmosphers, there are many applications for special electric brakes, and several style categories for degree of protection needed. And there are inland uses, too, to benefit from these special protection systems.

The Navy shipyard in Bremerton, Wash. had been using standard double C face brakes at a refueling containment site. Because they were not in direct contact with water, neither marine finish nor naval service brakes had been specified in the original purchase. The heavy salt air, however, created a severe- duty environment that drastically shortened brake life. The solution: washdown brakes that meet NEMA standard MG1-1.26.5 for waterproof machines.

But what levels of protection are available in such situations, and when do you need what?

Harsh environments

Brakes for such severe-duty applications, whether aboard ship or at dockside, call for marine finishes, special construction, or both, to withstand corrosive influences in the natural environment.

Several types of brakes are used for these severe-duty applications:
• Naval service brakes, which are built to exacting military specifications. In addition to corrosion-resistant painting and plating used for maritime brakes, naval service brakes undergo special testing and meet other requirements as well.
• Maritime service brakes, which have special marine finishes. They are used for less severe duty and when compliance to a military specification is not required.
• Washdown brakes, which have waterproof enclosures. They are watertight and dust-tight, and certified to Canadian Standards Association Enclosure 4.

Naval service brakes

Naval service brakes are built to military specifications MIL-B-16392 (ships) titled, “Brakes, magnet, naval shipboard.” Brakes furnished under this spec must have passed qualification tests listed in Table 1.

Naval service brakes must be listed or approved for listing on the applicable qualified products list (QPL) issued by the Naval Ship Engineering Center. Dings naval service brakes, for example, are listed on QPL-16392. Each brake manufactured is inspected for quality conformance as outlined in the basic spec. The data are recorded and remain on file.

Besides the qualifications in Table 1, naval service brakes must also fulfill these requirements:

Ductile (or nodular) iron housings. This is per MIL-I-17166. Although this is the material required in the specs, a common modification that brake manufacturers offer is a nonmagnetic housing. Cover, bracket, and other parts are aluminum or nonmagnetic stainless steel, except for the magnet itself. A typical application for the nonmagnetic model is aboard wooden-hulled mine sweepers. A brake that is qualified may be modified for special applications such as this when the following statement is conveyed to the purchaser: "This brake meets spec MIL-B-16392 with the following exceptions...." (which are then listed).

Special finishes. Applied to internal and external parts, this corrosion-resistant painting and plating ensures that the brakes do not rust or otherwise corrode from salt-water environments. Encapsulated coils. Protects against water damage and corrosion.

Manually operated external release. Commonly called a “deadman release,” this mechanism requires the operator to hold the brake in the release position. Should the operator become disabled, the brake will engage when the operator releases the handle.

Enclosure effectiveness. Five types of enclosures are recognized, each with its own testing method:
• Open.
• Dripproof.
• Watertight.
• Submersible (at 15 ft for 30 min).
• Explosion-proof (Class I, Group D).

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