Dockside Service Unit for Installation in Subway with Restricted Access

Overview

Dockside Service Units (DSUs) are permanent distribution assemblies that are usually installed above ground on quaysides and in other exposed locations, to provide temporary power for vessels undergoing repair or refit. Low current supplies (up to 125A) are usually provided via RCD protected plug-in outlets and high current supplies are hard wired to MCCBs with variable RCD and Monitored Earth protection. Each outgoing MCCB is housed in its own compartment with segregation to Form 4b Type 7. Due to the harsh installation conditions, DSUs have a high IP rating (typically IP56) and enclosures are fabricated from heavy gauges of grade 316L stainless steel with a painted finish. Assemblies to this specification have a design life of 25 years.

On a recent project undertaken by the Blakley Team, as well as the usual DSU requirements, because the assemblies are to be installed in subways, there were the additional requirements for the assemblies to have outgoing circuits exit from the topside of the enclosure (cable entry and exit is usually through the underside) and for the units to be supplied in two halves due to the restricted access in the subways. Once positioned on site the two halves are to be joined.

As can be seen from the top image, cable entry is via a brass gland plate located beneath the main incoming compartment. The bus bar chamber is located across the base of the assembly with the main switchgear compartments mounted above. The outgoing sockets are located towards the top of the assembly and hard wired outgoing ways exit the enclosure via brass gland plates located in the top of the enclosure. The enclosure splits in two equal halves, as identified in the bottom image.

To assist users on site, the switchgear supplying socket outlets is located in compartments with red doors whilst the switchgear serving hard wired circuits is located in compartments with yellow doors.