Pressure Reducing & Desuperheating (PRDS) Station

Modular Ready-to-Fit Steam Conditioning Solution!!!

Most modern boilers generate steam at high pressures & temperatures. High pressure steam has lesser volume than steam at atmospheric pressure, thereby translating into smaller boiler size & lower diameter of steam piping. Also, high temperature (superheated) steam has more energy, which translates into higher efficiency for power generating steam turbines.

On the other hand, all process industries use low pressure low temperature saturated steam, primarily due to the following reasons:

  • Saturated steam has the highest heat transfer efficiency.
  • Lower pressures & temperatures translate into thinner pipes, lighter flanges & less expensive materials thereby significantly reducing initial plant cost.

In any industry, steam is required at different locations, but the required steam pressure & temperature at each location varies according to the application. Therefore, high pressure superheated steam is generated at a central location (boiler), distributed to various locations in the plant through a steam piping network, and then reduced to the operating pressure & temperature just upstream of the usage points.

IndiTech PRDS station is a modular steam conditioning unit to reduce the steam pressure & temperature at the point of usage, and it can be directly installed into your existing steam network.

Some applications of PRDS stations are enumerated below:

  1. PRDS for process heating / cooling applications in sugar, food, textile, paper etc. plants
  2. Deaerator, Ejector PRDS for boiler
  3. Turbine bypass PRDS

Technical Data

Inlet Pipe Size

½" to 20" NB

Outlet Pipe Size

½" NB and above

Pressure Rating

ANSI #150, #300, #600, #900, #1500, #2500

Design Standard

ASME B31.1, ASME B31.3

PRDS Station Configurations

Separate Steam Control Valve, Water Control Valve & Desuperheater Combined Steam Control Valve + Desuperheater, Separate Water Control Valve Combined Water Control Valve + Desuperheater, Separate Steam Control Valve

End Connections

Flanged, Socket Weld, Butt Weld

Valve Body MOC

A216 WCB / WCC, A105, A217 WC6 / WC9, A182 F11 / F22 / F91

Piping MOC

A106 Gr. B, A335 P11 / P22 / P91

Instrument Options

Pressure Transmitter, Temperature Transmitter, Pressure Gauge, Temperature Gauge, Flow Meter, PID Controller, Control Panel, Junction Box

PRDS Station Operation Principle

The high pressure high temperature steam enters the PRDS station as shown in the figure. The steam inlet pressure gauge and dial thermometer indicate the pressure and temperature respectively of the inlet steam. The steam pressure control valve reduces the pressure of the steam. The steam inlet isolation valve along with the outlet isolation valve is used to isolate the steam pressure control valve, whenever maintenance of the control valve is to be carried out. The steam bypass valve allows steam flow at reduced pressure to continue when the steam pressure control valve is under maintenance or becomes inoperable. The spray water enters the water line as shown in the figure. The water strainer at the inlet prevents entry of foreign particles into the water control valve & desuperheater spray nozzles.

The water inlet pressure gauge indicates the pressure of the spray water. The water flow control valve regulates the quantity of the spray water going into the spray nozzles depending on the steam load. The water inlet / outlet isolation valves are used to isolate the water control valve, whenever maintenance of the control valve is to be carried out. The water bypass valve allows spray water flow to continue whenever the water flow control valve is under maintenance or becomes inoperable. The non-return valve prevents back flow of steam into the water pipe line. The desuperheater lowers the temperature of the steam to the required outlet temperature by injecting atomized water in the form of a very fine mist into the steam flow. The pressure transmitter and temperature transmitter sense the outlet steam pressure and temperature respectively and give a proportional current signal as output to the PID controller. The PID controller then compares the measured value with a set point, and generates an error signal, which is then given to the positioner of the steam pressure control valve and water flow control valve.

PRS Station Operation Principle

The high pressure steam enters the PRS station as shown in the figure. The steam inlet pressure gauge and dial thermometer indicate the pressure and temperature respectively of the inlet steam. The steam pressure control valve reduces the pressure of the steam. The steam inlet isolation valve along with the outlet isolation valve is used to isolate the steam pressure control valve, whenever maintenance of the control valve is to be carried out. The steam bypass valve allows steam flow at reduced pressure to continue when the steam pressure control valve is under maintenance or becomes inoperable. The pressure transmitter senses the outlet steam pressure and gives a proportional current signal as output to the PID controller.

The PID controller then compares the measured value with a set point, and generates an error signal, which is then given to the positioner of the steam pressure control valve. The safety valve opens and relieves excess pressure when steam pressure goes above set value, and re-closes and prevents the further release of fluid after normal conditions have been restored.

DSH Station Operation Principle

The spray water enters the DSH station as shown in the figure. The water strainer at the inlet prevents entry of foreign particles into the water control valve & desuperheater spray nozzles. The water inlet pressure gauge indicates the pressure of the spray water. The water flow control valve regulates the quantity of the spray water going into the spray nozzles, depending on the steam load. The water inlet / outlet isolation valves are used to isolate the water control valve, whenever maintenance of the control valve is to be carried out. The water bypass valve allows spray water flow to continue whenever the water flow control valve is under maintenance or becomes inoperable. The non-return valve prevents back flow of steam into the water pipe line.

The desuperheater lowers the temperature of inlet high temperature steam to the required outlet temperature by injecting atomized water into the steam flow. This is achieved by means of spray nozzles that atomize water into a very fine mist. The temperature transmitter senses the outlet steam temperature and gives a proportional current signal as output to the PID controller. The PID controller then compares the measured value with a set point, and generates an error signal, which is then given to the positioner of the water flow control valve.