Surface Blowoff

Definition - What does Surface Blowoff mean?

Surface blowoff is the process of removing foam, water and other matter from a particular surface or water level, such as in a boiler. It can also refer to the equipment used in the removal, such as surface blowoff valves.

Through this process, it is possible to eradicate all contaminants that could result in damage, hazards or corrosion in boilers.

Corrosionpedia explains Surface Blowoff

In the surface blowoff process, water is intentionally removed from boilers in order to prevent concentration of impurities while the steam is constantly evaporating. Water is blown off the boiler through steam pressure inside the boiler.

Steam boilers typically need regular replenishment, as their supply of water is constantly evaporating due to the constant steam production needed by almost all boilers. Water is capable of dissolving tiny particles of solids from containers such as boilers. Continuous steam evaporation can dissolve impurities which could damage the production of steam inside the boiler.

Without surface blowoff, such impurities could reach levels of saturation and undergo precipitation inside boilers. Impurity concentrations can be highly evident when steam is nearby surfaces of heat exchanges. Precipitation could take place in forms like scale deposits on the surfaces. Such forms of corrosion damage could initially reduce steam generation, and can put the boiler metals at risk of reaching inappropriate temperatures.

Surface blowoff constantly takes off small amounts of water inside the boiler as a way of eliminating impurities. It is highly effective to eliminate water with impurity levels at its peak, and this water can be seen in areas where steam undergoes separation in a component called a steam drum found on top of boilers.

There are two kinds of surface blowoff fittings:

  • Simple - a pipe that enters the steam drum at the regular water level
  • Sophisticated - connects swivel joint to pipe for short pipes that are suspended, and is more effective in terms of eliminating floating oil that could lead to foaming

With the use of surface blowoff, more steady operation can be achieved.

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