Keep Thermal Fluid Safety you need know(1)
The potential for fire should be considered in the design and operation of the thermal fluid system.
Thermal Fluid Boiler
Flashpoint and Fire Point. The flashpoint and fire point of a thermal fluid are determined through laboratory testing of unused fluid. The most common test method is the ASTM D92 Cleveland Open Cup (COC). The lowest temperature at which the vapor ignites is called the flashpoint. The temperature at which sufficient vapor is generated to support a continuous flame is the fire point.
While these test results provide data for comparing different fluids, any extrapolation of these results into real-life situations must recognize the three basic conditions required for a vapor ignition to occur:
- The fluid must be at or above the flashpoint or fire point while in contact with air for any vapor combustion to occur. This situation may not exist around leaks because the leaking fluid will cool rapidly on exposure to air.
- Enough vapor must be present to support combustion. Any dissipation of the vapor may reduce the concentration below the level required for ignition.
- The source of ignition must be located within the vapor cloud. Good electrical installation practice dictates that potential ignition sources are located a distance from piping or are enclosed properly.
If any one of these three conditions is not met, vapor ignition cannot occur.
Leaks. Normal thermal fluid system leaks consist of fluid seeping from threaded fittings, flange gaskets, mechanical seals and valve-stem and pump-shaft-packing glands. Any droplets formed will cool rapidly on exposure to air. Extremely low volume leaks may produce a light gray smoke. This is an indication that the fluid is oxidizing immediately on exposure to air.
There are several conditions under which “normal” leaks can present a risk of fire:
- Certain types of insulation such as mineral wool, fiberglass or calcium silicate have an open or porous structure that allows fluid to wick away from the source of a leak. As the fluid disperses within the insulation, its surface area increases dramatically while its temperature remains at or near the system operating temperature. The danger is that a substantial percentage of the leaked fluid will remain unreacted within the insulation due to the limited amount of oxygen available. If the supply of oxygen suddenly increases, the remaining fluid in the insulation will burst into flames. Prevent insulation fires by using nonporous insulation within several feet of areas prone to leaks such as valves and flanges.
- If a low volume leak occurs within a tightly enclosed area such as a cabinet, the available oxygen may be consumed, allowing unreacted vapor to accumulate. Prevent this by ensuring that all portions of a thermal fluid system are located in areas with adequate ventilation.
I will tell some safety of thermal fluid boiler you need know in next news.