the alternate pump automatically starts running. A gauge board within the pump room contains gauges for pump suction and discharge pressure and for measuring the water pressure at the connectors (elbow pressure). WATER-BRAKE WATER SUPPLY PIPING The  suction  inlets  of  the  pumps  (fig.  4-29)  are submerged    in    the    water-brake    tanks.    The    pump discharges each with appropriate valves and a flow-limiting   orifice   plate,   are   tied   together   and connected  via  flexible  hoses  to  strainer  flanges  at  the bottom  of  the  water  supply  pipes.  Hoses  and  rigid piping  connect  the  pressure  switches  to  the  supply pipes.  A  pump  suction  gauge  and  a  pump  discharge gauge  are  located  on  the  gauge  panel  for  each  pump. These  are  in  addition  to  the  gauges  for  the  pressure sensing switches. The suction side of the pump consists of an inlet with a gate type shutoff valve, a gauge valve, and a Macomb strainer immediately ahead of the pump inlet. A petcock for venting is mounted at the top of the strainer.  The  discharge  side  of  each  pump  includes  a flow  limiting  orifice  plate,  a  check  valve,  and  a  gate type  shutoff  valve.  Two  discharge  lines  merge  into  a single line, which later splits into two lines. High-pressure, flexible hoses lead to and connect to the brake   cylinder   water   supply   connectors,   which   are attached to the water-brake cylinders. A drain valve for the  water-brake  tank  leads  to  an  overboard  discharge. Fresh water from the ship's system is added to the tank via  fill  and  shutoff  valves  in  the  water-brake  pump room. WATER-BRAKE PRESSURE-SENSING SWITCHES Two pressure switches are connected to the piping leading from the pumps to the brake cylinders (see fig. 4-29).   They   usually   are   installed   on   the   bulkhead adjacent to the tank. The switches are electrically tied in with the main control console/ICCS/CCP to prevent operation in case the pressure falls below normal. Water pressure    keeps    the    switch    contacts    closed,    thus completing  a  circuit.  Should  the  pressure  fall  below normal,  either  one  or  both  of  the  switches  will  drop open, breaking the circuit. There are also two pressure gauges  in  the  lines  to  give  a  visual  indication  of  the pressure, commonly referred to as "elbow pressure." 4-21 STRAINER VALVE PRESSURE SENSING HOSES GAUGE PANEL PRESSURE SWITCHES TO CHARGE PANEL GATE VALVE MACOMB STRAINER MACOMB STRAINER CHECK VALVES GATE VALVE PUMP NO. 2 PUMP NO. 1 GATE VALVE DRAIN COCKS THERMOMETER ORIFICE FLANGES MOTOR CONTROLLERS GATE VALVE BAFFLES STRAINERS PLATFORM FLEX HOSES OVERFLOW FUNNEL SKIMMING FUNNEL FLIGHT DECK OVERBOARD DRAIN WATER LEVEL ABEf0430 FILL FUNNEL Figure 4-29.—Water-brake piping and pressure switch installation.