View all text of Subpart 56.50 [§ 56.50-1 - § 56.50-110]
§ 56.50-30 - Boiler feed piping.
(a) General requirements. (1) Steam vessels, and motor vessels fitted with steam driven electrical generators must have at least two separate means of supplying feed water for the boilers. All feed pumps must be fitted with the necessary connections for this purpose. The arrangement of feed pumps must be in accordance with paragraph (d) or (e) of this section.
(2) Feed pump supply to power boilers may utilize the group feed system or the unit feed system.
(3) Feed discharge piping from the pump up to, but not including the required stop and stop-check valves, must be designed for either the feed pump relief valve setting or the shutoff head of the pump if a relief valve is not fitted. (Refer to § 56.07-10(b) for specific requirements.) Feed piping from the boiler, to and including the required stop and stop-check valves (see paragraph (b) of this section), must have a design pressure which exceeds the maximum allowable working pressure of the boiler by either 25 percent or 225 psig, whichever is less. The value of allowable stress for design purposes must be selected as described in § 56.07-10(e) at a temperature not below that for saturated steam at the maximum allowable working pressure of the boiler.
(4) Feed pumps for water tube boilers must have freshwater connections only.
(b) Feed valves. (1) Stop and stop-check valves must be fitted in the main feed line and must be attached as closely as possible to drum inlets or to the economizer inlet.
(2) Auxiliary feed lines must be fitted with stop valves and stop-check valves.
(3) Boilers fitted with economizers must have a check valve fitted in the economizer discharge and located as close as possible to the drum feed inlet nozzle.
(c) Feed water regulators and heaters. (1) Where feed water regulators or feed water heaters are installed, an alternate means of operation with these devices bypassed must be provided.
(2) All feed water regulators installed in a unit feed system must be fitted with an external bypass.
(3) A feed water regulator may be interposed between the stop and stop-check valves in the feed lines.
(d) Group feed system. Group feed systems must be provided with pumps and piping as follows:
(1) Vessels having a feed pump attached to the main propulsion unit must be provided with at least one independently driven feed pump. Each of these pumps must be used exclusively for feed purposes and must be capable of supplying the operating boilers at their normal capacity. In addition, a second independently driven pump, capable of supplying such boilers at 75 percent of their normal capacity, must be provided.
(2) If two independently driven pumps are provided, each capable of supplying the boilers at their normal required operating capacity, and neither pump is used for other purposes, the third or emergency feed pump is not required.
(3) River or harbor steam vessels must have at least two means for feeding the boilers; one of which must be an independently driven pump, the other may be an attached pump, an additional independently driven pump, or an injector.
(e) Unit feed system. Unit feed systems must be provided with pumps and piping as follows:
(1) The unit feed system may be used on vessels having two or more boilers. When the unit feed system is employed, each boiler must have its own independently driven main feed pump capable of supplying the boiler at its normal operating capacity. In addition, there must be an auxiliary independent feed pump of the same capacity that can be operated in place of and in conjunction with the main feed pump. In vessels with three or more boilers, not more than two boilers may be served by any one auxiliary pump. The auxiliary pump may be so interconnected that any pump can feed any boiler.
(2) In the unit feed system, a separate feed line must be provided for each boiler from its pumps. A separate auxiliary feed line is not required. The discharge from each pump and the feed supply to each boiler must be automatically controlled by the level of the water in that boiler. In addition to the automatic control, manual control must be provided.
(f) Feedwater. The feedwater must be introduced into a boiler as required by § 52.01-105(d) of this subchapter.