R016600x

SECTION VII - OPTIONAL EQUIPMENT

7.1 BOOSTER PUMP(S) Booster pumps are required on an open system when the required NPSH to the feedwater pump cannot be achieved from an elevated hot-well. In a deaerator (D/A) system, booster pumps are required for most installations. Due to the low NPSH characteristics of these pumps, they are less sensitive to feedwater delivery problems caused by fluctuating pressure in the D/A than the Clayton feedwater pump(s). Booster pumps must be sized to provide 150 percent of the total system water flow at 150 percent of the total system head pressure. Total system head pressure includes the Clayton feedwater pump NPSH R , plus calculated pipe losses, and plus acceleration head loss. Most systems use two pumps. One of the two pumps is a standby pump, or the usage of the two pumps are alternated to balance operating hours. Only booster pumps with mechanical seals rated at a minimum of 250° F (121° C) should be used. The booster pumps cannot be rated at a discharge pressure that is lower than the system operating pressure

NOTE Each booster pump must have a 1/4 inch (6 mm) recirculation line, with a check-valve, piped from the discharge side of the pump back to the conden- sate receiver. This prevents overheating during “dead head” conditions. Clayton recommends using this return line to facilitate chemical injection at a common manifold on the condensate receiver.

7.2 BLOWDOWN SYSTEM 7.2.1 Blowdown Tank

The Occupational Safety and Health Administration (OSHA) requires that high temperature dis- charges be cooled to a temperature below 140° F (60° C) prior to entering a drainage system. A blow- down tank is performs this function. All blowdown and high temperature drain lines are to be piped to the blowdown tank. A capillary tube-type temperature sensor, mounted in the blowdown tank discharge line, actuates a temperature control valve, also mounted in the discharge line, to inject cooling water into the hot fluid. The temperature control valve can be adjusted to achieve the desired discharge fluid tempera- ture. The blowdown tank vent should be a straight run of full size iron or steel pipe.

7-1

10/06/2016

Sect07_f_102016.fm