Level Control

LEVEL MEASUREMENT IN STEAM BOILERS

The use of steam as an energy carrier is particularly common in most of plants such as power stations, refineries and chemical plants. Steam boilers are also vital to the food industry, textile industry and many other industry sectors.

Steam boilers are used to create steam that has a higher steam pressure than at atmospheric conditions. The boiling temperature and energy content of the steam also increase in addition to the pressure.

Steam boilers are found in nearly all areas of industry and there are primarily two types of steam boiler:

  • Water-tube boilers,
  • Shell boilers,

Level Measurement – Control and Safety

Maintaining a stable interface level is critical to the safe and efficient operation of the boiler.

Safety

Most of the boiler failures can be attributed to low water conditions. For safe boiler operations this must be kept under check. Low-water level conditions in the boiler occur when the water in the boiler drum falls below the low water level mark.

With low water level conditions, severel boiler damage can be happen. If the boiler keeps runnig with low water levelconditions, boiler ‘s furnace and the steel tubes can melt. If the boiler is feet with wateri n this conditions, boiler explotion can happen.

High water levels raise steam exit velocities and result in priming or boiler water carryover in to the distribution system. Priming results in wet dirty steam while carry-over can result in dangerous water hammer and pipe or equipment damage.

 

deformed boiler

 

On/Off Control

In on/off control the feed pump is switched on/off via a level sensor. When the water level falls to thethe “Pump on” level, the pump starts pumping a large quantity of relatively cold water into the boiler.
This will reduce the quantity of steam and cause the steam pressure to fall.

Modulating Control

In this type of system the water level in the boiler is controlled by a feed water valve, which is controlled by a level controllerand a level probe positioned on the boiler. The feed water valve controls the water intake, which is adjusted according to steam consumption.

 

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