PVI Industries PV500-34 manual 4

QuickDraw®

STEAM WITH SINGLE-WALL / DOUBLE-WALL (con't)

STEAM VALVES

1.One or more two-position, on-off, electric valves are used to control the flow of steam. The valves will return to the closed position when power is off. This feature will prevent an excessive temperature buildup in the event of a power failure. The valve manufacturer’s operation and maintenance instructions are shipped with the unit. Refer to these instructions during start-up and file for future referencing on maintenance.

CAUTION

Most valve problems are caused by dirt or trash in the steam line. This is most likely to occur during installation. Teflon pipe tape, pipe joint compounds, metal particles and dirt will clog up strainers and orifices and prevent valve seats from closing. Clean all pipe line strainers at start-up and check the valves again after a few days operation as recommended by the valve manufacturer. Inspection of strainers and blowdown piping should be part of the normal maintenance routine on this equipment.

OPTIONAL SAFETY SYSTEMS

1.This heater may be supplied with a pressure gradient monitoring (PGM) system, consisting of a differential pressure switch, a delay timer and a steam purge valve. It serves as a safety system to prevent the contamination of potable water with steam. The pressure switch monitors both steam and potable water system pressure. If the potable water pressure falls to a point slightly above the steam pressure and stays there for a short period of time, then the heater shuts down, closes the steam valve and opens a steam purge valve to quickly reduce the steam pressure in the heat ex-

changer. The system requires a manual reset to begin operation again. Note that the system does not necessarily detect a leak, but it prevents steam from entering the potable water if there is a leak.

2.Another safety option is the tank purge system (sometimes called a double solenoid safety system). The tank temperature is monitored and if it exceeds an adjustable limit, the heater is shut down and a valve opens to dump the overheated water. This allows cold make-up water to enter the tank and quickly reduce the tank temperature.

START-UP OPERATION

1.After all the steam, condensate and water lines are installed and inspected, the steam supply source and the condensate receiver should be checked for correct operation. Steam supply pressure to the heater must be equal to or less than the supply pressure on the heater decal. A pressure reducing valve can be installed in the supply line to meet this requirement.

2.Steam is directed to the heat exchanger through a header and steam control valves. The steam control valves are normally closed, on-off, electric valves and solenoid-operated.

Should an electrical power failure occur, steam valves will close and stop steam flow to the unit.

WARNING!

Excessive steam pressure can cause the steam valve(s) and condensate trap to malfunction and can cause the heat transfer rate to exceed the relief valve capacity which can result in an explosion causing damage, injury or death.

PV500-34 05/03 4 Section 34