Matematicas

Water Technologies

Wallace and Tiernan®

Gas Feed System

Series 50-200 Evaporator

for Liquid Cl2, NH3, or SO2

Key Benefits:

Reliable Automatic operation

Easy to install-shipped completely

assembled

Accurate, reliable monitoring of

operating conditions

Meets ASME and Chlorine Institute

code requirements

Automatic pressure relief of gas

outlet and liquid inlet standard

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The Wallace and Tiernan® Series 50-200 Evaporator

(sometimes called a “vaporizer”) is an electrically

heated, immersed tank-type heat exchanger. It is

necessary wherever the required rate of gas withdrawal

cannot be satisfied by direct connection to multiple

containers. Such high capacity installations include:

Disinfection in large municipal or industrial water

plants

Chlorination of municipal sewage

Disinfection of municipal and industrial

wastewater

Bleaching and waste treatment in pulp and paper

mills

Aluminum fluxing (removal of magnesium)

Treatment of cooling water in power plants

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Features

Reliable, Automatic Operation

To help prevent overfilling, the liquid

level in the pressure cylinder is selfadjusting.

Level in the water-bath tank

is maintained by a solenoid that controls

make-up water flow. A thermostat

maintains hot water temperature.

Alarms and readout monitor operation

of the liquid-evaporation and hot water

systems.

External Heater

The electric water heater is external to

the water-bath tank, assuring uniform

heat distribution. This prevents “hot

spots” and minimizes the possibility of

liquid being heated in excess of 100° C

(212° F), causing pressure build-up that

could trigger gas relief.

Alarms and Monitors

A sight glass for water-bath level and a

water temperature gauge help monitor

water-bath conditions. Electronic

switches provide accurate and reliable

water-temperature regulation. Gas

pressure and temperature gauges are

included. There are high- and low-alarm

switches for water-bath temperature and

low-water level. An automatic pressurerelief

system in the gas outlet is standard.

A similar relief system in the liquid-inlet

line is also standard. Both systems have

high-pressure alarm switches.

Weather-Resistant

The evaporator enclosure is made of

rugged, pressure-formed ABS panels.

An optional, gasketed ABS rear cover

added to the enclosure makes it weather

resistant. This arrangement is ideal for

outdoor service, especially at power

plants.

Meets Code Requirements

The Wallace & Tiernan® Series 50-200

Evaporator conforms to ASME standards

and meets recommendations of the

Chlorine Institute. The pressure cylinder

and water-bath tank are cathodically

protected against corrosion. The tank

is heavily galvanized inside and out.

The pressure cylinder and gas pressure-

Water-level sight glass is at left of panel.

Left side of panel has indicator lights

for high-water temperature (red), lowwater

temperature (amber), and at

bottom, low-water level (red). At top are

gas temperature and pressure gauges.

Meters in center of panel are for water

temperature and cathodic protection

control, and the power-disconnect

switch is at the right of the panel.

relief valve comply with ASME Boiler

and Pressure Vessel Code, Section VIII,

Division I.

Pre-Wiring and Other Installation

Economies

Pre-wiring of all evaporator controls and

components is completed at the factory

and included as standard. Electrical

installation requires only connecting

external power to a coded terminal

strip. Only one 3-phase power supply

is required; a transformer in the panel

supplies 115-volt power for control

functions. There are seven nominal

voltages available for the heat exchanger.

Three sets of unpowered customer

alarm contacts are standard: high water

temperature, low water temperature,

and low water level.

Easy to Clean

The top of the pressure cylinder is a

bolted flange removable for access to the

interior. A bottom connection allows the

cylinder to be flushed in place. An access

hole in the water-bath tank permits

inspection of the cylinder exterior and

the tank interior. The enclosure is easily

removed for access to the evaporator

interior.

Easy to Install

The evaporator is shipped completely

assembled. The vapor vent and overflow

drain are piped separately to ensure

adequate water-bath overflow. The

electric heating elements are mounted

from the top of the water heater. Liquidinlet

connections can be made at the

top or bottom; bottom connections are

required for evaporators connected to a

common liquid supply. Using the bottom

connection helps maintain liquid levels

in all evaporators.

NEMA 4 Control Panel

The NEMA 4 panel contains a single

printed circuit board incorporating all

control functions and unpowered alarm

contacts. Control switches, alarm lights,

and readouts are also on the panel. As

a precaution, a fused disconnect switch

for the incoming power interlocks with

the panel door.

Design and Operation

Liquid enters at the top of the pressure

cylinder, but a drop pipe carries it almost

to the bottom. An alternate liquid inlet

at the bottom has a riser that terminates

near the bottom of the drop pipe. A

vaporized gas outlet at the top has a short

drop pipe. This design limits pressure

in the cylinder to that of the supply

containers and prevents complete filling

of the cylinder with liquid. The pressure

cylinder is immersed in a temperaturecontrolled,

hot-water bath. Heat transfer

from the water bath heats the liquid and

superheats the gas. A vacuum-regulating

valve at the gas outlet reduces pressure

to increase superheat and prevent

reliquification beyond the valve.

Liquid level in the pressure cylinder

adjusts

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