Featured Application: Temperature and Pressure Switches in Industrial Boilers
A boiler is a closed vessel in which a liquid, typically water, has heat energy applied to create steam. Old boilers of the nineteenth century were typically made of very expensive, high-quality wrought-iron, but most modern boilers are made of steel or steel alloys due to higher-temperature characteristics and better strength-to-weight ratios. Heat energy is provided to the boiler chamber by burners fueled by natural gas, oil, coal or by electric heaters. While boilers are widely used in many industries, some typical applications for industrial boilers are:
- Steam power generators
- Hot water applications
- Food preparation
- And water sanitation purposes
When discussing boiler design, safety is absolutely paramount. Even though modern industrial steam boilers must adhere to strict regulatory standards, catastrophic explosions still occur. This is one application where pressure switches absolutely must work, and is a reason why CCS has focused on making sure our switches absolutely DO work.
Two Main Types: Fire-tube and Water-tube
There are two main types of Industrial Boilers, Fire-Tube and Water-Tube Boilers. Fire-Tube boilers consist of a series of straight tubes that are housed inside a water-filled outer shell.
The tubes are arranged so that hot combustion gases pass through inside the tubes so they heat the water that surrounds the tubes causing steam. This is a simpler construction with less rigid water treatment requirements for the water used in the outer shell This design is well suited for space heating and low pressure hot-water industrial applications, not for high power steam generation.
The second design, water-tube boilers, are directly opposite from the fire-tube boiler in that the boilers are designed to circulate hot combustion gases around the outside of a large number of water-filled tubes. The tubes extend between an upper header, called a steam drum, and one or more lower headers or drums. This application allows for a lower weight-per-pound of steam to be generated, and for a much shorter time to generate steam. Generally, these boilers can handle up to 5,000 PSI pressure and the steam generated can reach very high temperatures. Proper controls of these high pressures and temperatures are necessary to prevent catastrophic events from happening. Because two drums are needed for water containment, water-tube boilers are extremely large and heavy and typically have a much higher initial capital cost.
Pressure and Temperature Switches in Industrial Boilers
Every boiler requires proper control of the pressures and temperatures during the steam generation process.
Here are some of the common ones:
High Steam Pressure Switch: This switch triggers when the steam pressure inside the vessel reaches too high a point and triggers the burner to stop firing. If the switch did not work properly and the burner continued firing, pressure would build higher and higher and the vessel could explode. Common CCS switches that are used for this type of steam application would be a 604G or 6900G model. These are standard non-hazardous CCS diaphragm models which can easily handle the pressure levels seen in boilers and are suitable for steam conditions.
High Gas Pressure Switch: This switch concerns industrial boilers where the heat is powered by natural gas combustion. If too much natural gas flows to a combustor, the burner could go out due to improper fuel mixture or the flame could be too large and could cause boiler overheating. If the flame goes out then a combustible mixture could fill the boiler combustion chamber so that when the flame turns back on again, an explosion could occur. Common CCS Models used for natural gas combustion are: 646GE, 6900GE. These are standard switches to be used in hazardous areas and are compatible for applications using natural gas.
Low Gas Pressure Switch: Like the High Gas Pressure Switch, this switch is triggered when the natural gas inlet pressure is too low. This is still likely to be considered a hazardous environment so 646GE or 6900GE switches are commonly used here.
Oil Low Temperature Switch: To burn oil properly, the oil needs to be heated to a proper degree to ensure the proper vaporization for the fuel/air mix. A temperature switch is used here to monitor if the oil is falling below the needed level. This temperature switch can be considered to be located in hazardous areas, therefore a CCS 646TE or 6900TE temperature switch would be used for these applications.
Oil High Temperature Switch: Likewise, a temperature switch is used for the same purpose, but this time if the oil reaches too high of a temperature then the proper oil/air mixture will be incorrect. Again, a 646TE or 6900TE temperature switch makes sense here.