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|  MIL-V-18683A(SHIPS)
be clearly indicated in a list submitted with the master drawings.
3.3 General design.
3.3.1 The principle of reliability is paramount and no compromise of this principle shall be made with
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any other basic requirements of design. Each pump shall be designed to have a service life of 20 years of which
10 percent shall be actual operation: There shall be no limit on the number of starts during the life of the
pumps. Parts subject to wear and deterioration (with the exception of packing and seals) will be replaced at
intervals not shorter than three years. The requirements specified above shall not be construed or interpreted
as a warranty requirement nor otherwise affect the manufacturer's warranty. The design and construction of all
pumps shall be the most compact consistent with the following requirements:
(a)
Reliability.
(b)
Accessibility for repair.
(c)
Resistance to wear or corrosion,
(d)
Economy.
(e)
satisfactory operation when inclined as follows:
(1) For surface ships:
a. Up to 15 degrees to either side (permanently inclined).
b. With the ship rolling up to 45 degrees from the vertical to either side.
c. With the ship pitching 10 degrees up and down from the normal horizontal plane.
(2) For submarines:
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Surface
Snorkel
Submerged
degrees
degrees
degrees
Trim
degrees
Pitching
degrees
degrees
120 seconds
6 seconds
Time of complete pitch cycle
6 seconds
15 degrees
15 degrees
15 degrees
List
Rolling
degrees
degrees
degrees below
10 knots and
degrees
above 10 knots
14 seconds
12 seconds
Time of complete roll cycle
14 seconds
Snap roll
55 degrees
Time of snap roll
20 seconds
Note: Degrees measured from the vertical to either side for list and roll, and from the
normal horizontal plane up or down for trim and pitch.
3,3.2 The priming pump shall be of the centrifugal displacement, wet vacuum type and shall be provided
with all necessary fittings and accessories including vacuum relief valve, check valve and similar items
.
required for the satisfactory priming of one or more centrifugal pumps as required by the contract or order.
3.3.2.1 Each priming pump shall be furnished with an automatic valve to prevent flow of liquid from the
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centrifugal pump or piping system to the primer. The automatic priming valve shall be of a rugged simple
design without levers, clevis pins or parts which would have a tendency to vibrate or wear.
3.3.2.2 The design of the primer shall be such as to keep metal contact to an absolute minimum in order
to reduce wear.
3.3.2.3 Consideration will be given to priming pumps of designs other than the centrifugal displacement
Unit vacuum type providing all other features required herein are retained; the performance is equal to or
better than that of the centrifugal displacement wet vacuum type; and the weight, space, and power requirements
.
do not exceed those of the centrifugal displacement wet vacuum type,
3.3.3 Mounting.
3.3.3.1 Pump units shall be horizontally mounted.
3.3.3.2 When specified (see 6.1), the pump unit shall be mounted on a bedplate which also serves as reser-
voir for the seal water.
3.3.3.3 Special attention shall be given to the design of closed-coupled pump to insure that leakage from
the pump stuffing box glands cannot enter motor frames or bearing brackets.
3.3.4 Bearings.
3.3.4.1 Radial and thrust bearings shall be of the ball type.
3
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