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Steam boilers

Feed water regulation

Measurement of the boiler water level along with a nominal-actual value comparison via the level switch, the feed water control valve supplies the boiler with at least the same amount of water discharged in form of steam.

RTK offers equipment suitable for this purpose:

  • Boiler fill level measurement based on displacer weight measurement
  • Feed water regulator with HW/NW switchgear and optional steam- and water quantity regulation
  • Feed water control valve electric / pneumatic
  • Feed water control/motor stop valves with emergency control function for multi-boiler systems
  • Feed water control valves with feed pump minimum function
  • Feed water control valves with feed pump and economizer minimum function

Desalting regulation

The continuous steam output leaves soluble salts in the boiler water which concentrate on the surface of the water. To prevent boiler damage boiler damage the conductivity must not exceed certain limits.

Using conductivity measurement of the boiler waters and nominal-actual value comparison in the desalting regulator, the desalting valve continuously removes the amount of water from the boiler required to maintain steady boiler water conductivity regardless of the steam output.

RTK offers equipment suitable for this purpose:

  • Process controller as the desalting regulator
  • Desalting valve with and without sampling valve

Blowdown

Continuous steam output leaves insoluble salts in the boiler water which deposit at the bottom of the boiler. To prevent boiler damage, these deposits must regularly be removed from the boiler. This can be done by abruptly opening a blowdown valve for about two seconds at 240 - 480 minute intervals, depending on the steam space rating and water quality.

RTK offers equipment suitable for this purpose:

  • Bottom blowdown valve with lever
  • Bottom blowdown valve with pneum. actuator, lever and solenoid valve
  • Bottom blowdown program controller for solenoid valve

Master steam valve

This valve, typically installed directly on the steam output fitting on the boiler, has several functions. It is primarily used to close the steam boiler from the downstream system when needed. However, it can also be used to slowly preheat the system following stoppages, e.g. on weekends. However, this valve is also used to ensure a minimum boiler pressure in the event of excess steam demand.

RTK offers equipment suitable for this purpose:

  • Motor- or pneumatic control valves
  • Automatic start-up circuitry
  • Holding pressure controlled pressure reduction with superimposed primary pressure protection

Economizer regulation

Economizers on steam boilers increase their efficiency immensely by utilising residual heat from the flue gases to significantly raise the temperature of the relatively cold feed water. This is achieved by preventing the flue gas from dropping below the dew point through stable control of the flue gas temperature irrespective of the load by supplying more or less feed water through the economizer.

Preventing evaporation in the economizer typically requires a minimum flow through it.

RTK offers equipment suitable for this purpose:

  • Flue gas temperature sensor
  • Process controller for the flue gas temperature
  • Electric / pneumatic 3-way mixing or diverting valves

Superheater

Operating turbines often requires superheated steam. Further thermal energy is typically added to the saturated steam inside a heat exchanger on the boiler bathed in flue gas for this purpose. Increasing the volume by superheating steam is the condition which, when operating turbines with superheated steam among other things significantly improves efficiency by converting the superheating energy in mechanical work, so by increasing the heat gradient in addition to the inlet and discharge pressure than those values specified. Mixing valves or desuperheaters are typically used to maintain the precise superheated steam temperature.

RTK offers equipment suitable for this purpose:

  • Steam temperature sensors
  • Process controllers as steam temperature controllers
  • Electric / pneumatic 3-way mixing or diverting valves
  • Injection coolers for two/multi-stage superheaters

Drum emergency drain

In the event of feed water regulation failure/overload this valve protects the water tube boiler or the (first) superheater from overflowing by controlling/regulating this valve, quickly activating it and immediately draining the portion of the water inside the drum to restore the normal water level. Without emergency drain valve there would be a very high risk of overly wet steam or even feed water entering the superheater, posing an immense risk of boiler damage.

RTK offers equipment suitable for this purpose:

  • Globe control valves are typically pneumatic with multi-stage controlled cone fittings with suitable resistance to cavitation and evaporation

Our affiliate Schroedahl offers suitable valves for boiler systems with pressure stages up to PN600, available in a variety of forged steel materials with special cone fittings for cavitation-free operation, multi-stage controlled reducers, etc. If interested, please contact us directly or click this link to be redirected to Schroedahl to obtain initial information.

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