UFC 4-150-02
12 May 2003
3-8.4.1.2
Single Deck Piers. On a single deck pier the substation can be deck
mounted or at grade level adjacent to the pier. The unit substation illustrated in the
vault system in Figure D-2 could also be utilized in the pier deck mounted or grade level
installation system. In either installation method, the unit substations are outdoor
construction. The deck mounted/grade level substations may include walk-in aisle
features, however they are not recommended when located on the pier due to the
significant increase in size.
3-8.4.1.3
Existing Pier Vaults. Many existing Pier's utilize the electrical vault
system. This system is described in Figure D-2. This type of electrical service,
commonly used on many existing piers, is not authorized for the design of new piers
without approval from NAVFAC EICO or USACE. It was based upon electrical vaults
located below the pier deck that were designed as an integral part of the pier's structural
system. The vaults house secondary unit substations and may also contain primary
switching equipment. The vaults require proper ventilation, pumping systems, and an
access system integrally designed into the pier's deck. This type of electrical system
has four significant disadvantages: (1) the vaults are considered to be a "confined
space"; (2) the vaults are subject to flooding; (3) the vault's environment is excessively
caustic to the electrical equipment, even under normal conditions; and (4) replacement
of a unit substation creates significant interference to pier operations and results in deck
pavement removal and replacement
When a vault system is used, the substation vaults must be ventilated and
flood resistant for protection of the electrical equipment. Prevent flooding with dual
sump pumps that discharge at a point above highest tide. Provide a "float switch and
alarm system" to alert personnel of sump pump failure and high water level. The sump
pump power must be connected to a source other than the vault substation. That
source must remain energized when the pier electrical hotel service power and
permanent / industrial power systems are turned off. Freeze protection must be
provided in climates where any element of the pumping system could freeze.
Ventilation cooling must be provided with air quantity based upon the highest site
temperature and the highest vault temperature that can be tolerated by the electrical
equipment. One approved method of vault ventilation is shown in Figure D-2. Separate
ventilation air intake and exhaust louvers by as much distance as possible. They may
be on opposite sides of the pier if the ventilation ducts are above high tide. Provide an
access system for the electrical vault that includes personnel access and equipment
replacement access. Personnel access usually consists of manhole frame with cover
and vertical ladder. Equipment access systems are a significant structural element that
are required to withstand vehicular traffic and must be designed as an integral part of
the pier deck.
3-8.4.2
Outlet Assemblies. The number of electrical shore service stations, their
location aboard ship, the per station ampacity, and appropriate voltage for each ship are
defined in SCDB. For a general discussion of methods to be used to establish shore
utility station spacing on piers and wharves, refer to Chapter 2. For spacing at
drydocks, refer to UFC 4-213-10.
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