Continuous Steam Heater Figure 320

Figure 320 Continuous Heater

Figure 320 Continuous Heater

The continuous steam heater figure 320 is made for direct connection to water and steam lines and has a spindle for regulating water flow. The figure 320 heater can also be supplied as an “instantaneous heater” with special level and cock arrangement for producing immediate supply of hot water.

The liquid under pressure attains a high velocity passing through the nozzle. Steam enters through a series of nozzles in the combining tube and an intimate mixing of the liquid and steam occurs in the throat region. The liquid absorbs all of the heat of the steam. Under normal conditions no loss in water pressure occurs. In certain cases, this water can be operated against back pressures higher than either the supply water pressure or steam pressure.

Continuous Heaters are designed for direct connection to water and steam lines. Heaters of this type mix steam with cold water and discharge hot water under pressure. Many plants use these heaters to supply hot water for washing floors and equipment, “Instantaneous Heaters” are particularly useful as warm water emergency washing units in laboratories and plant areas where safety showers are required.

These heaters can eliminate mechanical pumps, resistance or bayonet heaters and containment vessels. These units have a low initial cost, limited moving parts and are easy to install and require little or no maintenance.


The Figs. 320, 321, and 324 Heaters are equipped with a non-seating screw spindle and handwheel. By turning the handwheel, the spindle can be adjusted to regulate water flow. The tapered end of the spindle is designed to provide correct proportions of steam and liquid. Flow rates can be duplicated by means of an indicator arrangement which indicates the position of the spindle.

The Fig. 324 “Instantaneous Heater” is equipped with a lever and cock assembly which turns the water on first, then the steam. Thus, this assembly is both an “on-off” control and a safety device. Temperature control can be made automatic by using a thermostatically controlled valve in the steam line. Also, a special device is available to shut off steam should water pressure fail.

These heaters can be made of a variety of materials if corrosive conditions so require. Fig. 320 Heaters are normally made from bronze in sizes up to 3 inches. Many sizes are available from stock. The Fig. 321 Heater with flanged connections is made in a 4 inch size. Fig. 324 “Instantaneous Heaters” are made in bronze with semi-steel plug cocks in sizes from 3/4 inch to and including 4 inch pipe connection sizes. These units are assembled with lever and cock arrangement on order.

Figure 320 Operation Example

Operation Example


In heaters of this type, the liquid under pressure attains a high velocity passing through a nozzle. Steam enters through a series of slanting nozzles in the combining tube and an intimate mixing of liquid and steam occurs in the venturi throat. There, the liquid absorbs all of the heat of the steam. The hot liquid is then discharged into a tank or through a piping system. Water discharge pressure can vary from a slight decrease to an actual increase depending on the specific operating conditions.

Regulation of water flow is obtained by adjustment of the spindle in the water nozzle as noted under Construction.

The pressure of the operating liquid must be at least 5 psig, while the steam pressure may be from 20 inch vacuum to 225 psig. The back pressure against which these heaters will discharge varies with the injection water and steam pressures. It is desirable to have as little back pressure as operating conditions will permit. For operation against back pressures higher than the inlet water pressure, special provisions must be made for starting.


Figure 320 Heater Dimensions




A B C D E F *
1/2 10-5/8 4-5/8 5-1/4 3/4 1-9/16 1/2 3-1/2
3/4 14-1/16 6-5/8 6-7/16 1 1-7/8 3/4 5-1/2
1 17-1/14 8-5/8 7-5/8 1 1/4 2-3/16 1 9
1-1/4 20-7/16 10-1/4 8-11/16 1 1/2 2-1/2 1-1/4 13
1-1/2 23-7/8 12-3/16 9-15/16 1 3/4 2-13/16 1-1/2 18
2 29-5/8 15-3/4 11-5/8 2 1/4 3-1/2 2 34
2-1/2 37-1/8 19-5/8 14-1/2 3 4-1/8 2-1/2 52
3 42-3/4 23-3/16 16-5/16 3 1/4 4-3/4 3 75