Algas SDI Direct Fired F6-ASME, Руководство по эксплуатации и техническому обслуживанию

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Introduction
Algas-SDI Operation and Maintenance Manual – P/N – 54000 2
HOW THE VAPORIZER WORKS
When the shut-off valve in the liquid supply line is opened, liquid is forced into the
heat exchanger by the pressure in the storage tank. As the liquid level rises,
some of the liquid boils off until it matches the pressure coming from the tank.
The flow of liquid into the heat exchanger will stop when the rising liquid forces
the float upward, closing the liquid inlet valve, or when the pressure in the heat
exchanger is the same as the pressure coming from the storage tank.
When the burner(s) is lit, the heat will boil off the liquid in the heat exchanger.
During periods of low or no demand, the pressure will build up to the storage tank
pressure. Whenever pressure in the heat exchanger starts to increase above the
tank pressure, the pressure differential will cause the LP gas to flow back through
the inlet valve to the tank.
Due to the boiling action and the flow back to the tank, the liquid level in the
exchanger will drop. When the liquid level drops, the temperature sensor will
sense the warmer vapor and cycle off the main burner(s).
As the demand increases, the pressure in the heat exchanger will drop. As a
result, liquid will flow into the exchanger, and the temperature sensor will sense
the cool liquid, and cycle the main burner(s) on.
During continuous operation, the burner(s) will cycle on and off to maintain the
required supply of vapor. As long as the rate of vaporization exceeds the
demand, the exchanger will contain a very small amount of liquid. The only time
the exchanger will contain a large amount of liquid is when the demand is equal
to or above the capacity of the vaporizer.
Whenever the demand exceeds the capacity of the vaporizer, the capacity
control valve is engaged, which limits the withdraw rate from the exchanger to
the maximum capacity of the vaporizer.
The capacity control valve is a spring loaded valve mounted on the outlet of the
exchanger. Liquid LP gas is supplied to the top of the valve and vapor from the
exchanger to the bottom of the valve. During normal operation, the valve is held
open by the force of the spring.
When the liquid/vapor pressure differential exceeds the spring force, the liquid
pressure will begin to close the valve. This restricts the flow out of the vaporizer.
Any increase in demand will create greater pressure drop. In turn, the valve will
further restrict the flow of vapor from the unit. This throttling action will cause the
gas outlet pressure to drop, allowing the pressure in the heat exchanger to build
back up and maintain proper gas supply to the vaporizer’s burner(s) and keep
the vaporizer in operation.