After engineers at Puget Sound Naval Shipyard placed their third order for replacement parts, they knew they had to find a better solution.
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?
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:
• Submersible (at 15 ft for 30 min).
• Explosion-proof (Class I, Group D).
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For a watertight or waterproof enclosure, the NEMA hose test is the most common test method. It is conducted by playing a stream of water from a hose with a 1-in.-diameter nozzle delivering at least 65 gpm from 10 ft away, in any direction, for not less than 5 min. An alternative test involves submerging the equipment to a 3-ft depth for 5 min. Water must not enter the brake enclosure because of either procedure.
Typical uses of naval service brakes are in U.S. Navy applications. If the ship is used for combat, or if the brake’s function is vital to the vessel’s mission, then a naval service model will be specified. In other applications, such as capstans at submarine bases, dry docks, and navy yards, maritime or washdown brakes may often be specified.
Maritime service brakes
These brakes have the same corrosionresistant painting and plating as specified in MIL-B-16392, but do not have the other special features listed under naval service requirements. They have the same design and construction as standard brakes, with the addition of the special marine finish. Normally, marine finish is applied to waterproof and dust-tight models. However, it can be furnished on dripproof models for use in specific applications.
Maritime service brakes are designed with the intent to comply with IEEE 45 and U.S. Coast Guard specifications CG- 259 and 46CFR 110.10-1. Coast Guard specs certify entire systems such as winches, hoists, and conveyors; they don’t cover individual components such as brakes.
Space heaters that reduce internal condensation can be supplied as an option for both naval service and marine finish brakes. Other options include moisture and fungus protection for the brake coil.
Brakes with marine finish serve a variety of applications, including anchor chain windlasses, winches on docks and piers, capstans, mooring winches on tugand- barge combinations, cargo hoists, and other deck and dock machinery.
Other inland applications can also benefit from protective finishes supplied on maritime brakes. The U.S. Army Corps of Engineers, for example, is currently retrofitting flood gates throughout the country, which were originally installed in the 1950s. As part of this program, Dings marine-finish brakes are used on hoists that run the winches that operate the flood gates.
These brakes meet NEMA standard MG1-1.26.5 for waterproof machines and are certified to CSA Enclosure 4. Manufacturers may supply washdown brakes with special design features that make them more durable and more watertight than regular waterproof brakes.
Unlike standard enclosed models, washdown brakes are designed to resist high-pressure hosedowns and caustic solutions. Commonly specified by the foodprocessing industry, they also improve life in other harsh applications where equipment must survive extremely wet conditions.
Wayne Hendricks is Senior Product Engineer, Dings Co., Dynamics Group, Milwaukee.