UFC 4-213-10
15 August 2002
7-4.8.1
Main Dewatering Pumps. At least two main dewatering pumps are
required to meet the dewatering time requirement and to have redundancy. Limit the
size to 1.37 m (54 in.)
7-4.8.1.1
Classes of Pumps. The three general classes of pumps suitable for
moving large volumes of water at relatively low heads are as follows:
Axial flow. For static head pumping up to 7.62 m (25 ft), axial flow units
(propeller) may be the most desirable.
Mixed flow. Mixed flow units give good results on heads up to
approximately 22.86 m (75 ft.)
Centrifugal. Centrifugal pumps are more suitable for the higher heads.
7-4.8.1.2
Design Problems. Drydock dewatering presents unusual water pumping
problems because of the extreme variations in both suction and discharge heads. See
Figure 7-1 for typical operating characteristics of a 1.3 m (54-in) mixed flow impeller
pump operating under graving dock hydraulic conditions. For the proper positioning in
the pumpwell or various types of pumps and for typical arrangements of intake and
discharge, refer to American Civil Engineering Practice, Volume II.
7-4.8.2
Drainage Pumps. Provide drainage pumps to remove seepage,
precipitation, caisson and valve leakage, and wash water, and to clear the dewatering
pump suction chamber and drainage system. Because of sandblasting operations, the
drainage pumps (and sump pumps discussed below) must be capable of handling a
certain amount of sand and sandblasting products in suspension without excessive
wear on casings of impellers. Also, ready access should be provided to pump suction
chambers through manholes or other openings located so as to facilitate easy cleanout
of these chambers.
7-4.8.2.1
Number of Pumps. The number of pumps should never be less than
three on the basis that drainage system redundancy is maintained by two operational
pumps when the third is out of commission.
7-4.8.2.2
Pump Capacity. Estimate the total capacity required for relieved docks
from an evaluation of the foundation permeability. For gravity docks, where only two
units are required, the capacity of each unit should be:
Submarine or destroyer docks, 9462.5 L/min (2,500 gpm.)
Cruiser docks, 18925 L/min (5,000 gpm.)
Carrier and Auxiliary docks, 28387.5 L/min (7,500 gpm.)
7-4.8.2.3
Types. Drainage pumps should be vertical shaft, direct connected, motor
driven; they may be of the wet or dry pit type:
7-9
Previous Page
