A surge tank is an attachment to a pressurized system designed to accommodate pressure changes. Its purpose is to neutralize rises and falls in pressure to prevent system failures, blowouts, and other problems. These devices can be used with a number of different types of systems ranging from the fuel lines in vehicles to the systems used to regulate water levels in swimming pools.
The surge tank is attached at the highest point of the system. When pressure rises, forcing fluids upward, they shift into the tank rather than blowing out the system. In the swimming pool example, if several people jump into a swimming pool at once, the water flows into gutters and rises into the tank instead of slopping out of the pool. The ability to accommodate a sudden increase in pressure is critical with closed systems like radiators, where the increased pressure cannot be vented and could cause a rupture.
If the pressure drops suddenly, the surge tank can fill in with a reserve of fluid until the pressure is equalized again. Tanks attached to fuel lines in vehicles, for example, will step in and deliver fuel to the engine if there is an interruption in the fuel line. While the tank cannot keep the system going forever, it can stabilize it long enough to fix a problem or bring the system to a safe stop for inspection and repair.
Surge tank design is dependent on the system is attached to. The device usually has a set of valves to control movements of fluids and gases from the tank, and it may have an emergency relief valve designed to release pressure in the event of an emergency. These tanks can also be used to bleed air out of a system, as air will rise to the top, and it can be vented while a valve keeps fluids safely inside the system.
When installing a surge tank, it is important to use one designed and rated for the system. If the tank is not fitted properly or it is not strong enough, a catastrophic failure can occur. Many companies make tanks designed for various applications, and it is possible to order custom models for particular settings, in the event that there is a special need. People fitting them to vehicles that do not come with a stock tank should be aware that such modifications can void a warranty.
By Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.