One of the "solutions" sometimes applied in an attempt to solve the problem of leaking heat exchangers is the use of Belleville washers. Belleville washers look like heavy-duty flat washers -- except they have been slightly deformed, or "coned," so that there is a small taper from the inner diameter to the outer diameter. This taper is very gradual.
This very slight taper turns the washer into a spring -- a spring that has been designed to flatten under a specified load. So are Belleville washers the answer to offsetting the relaxation inherent in heat exchanger gaskets? Should they be routinely used to improve reliability and prevent leakage in heat exchanger joints?
Like most springs, Belleville washers are linear devices; that is, the compression of the spring is directly proportional to the load applied. Dividing the force to deflect by the total deflection gives 47,400 pounds per 0.018 inches, or 2,633,000 pounds per inch, which is the spring constant (or K value) of the washer. This means that for every 2,633 pounds of force applied, the spring will compress by 0.001 inches.
The use of Belleville washers on heat exchanger flanges is based on this spring deflection, as it is reasoned that the spring in the washer will keep the flanges tight if the gasket should relax or lose thickness. So are Belleville washers the answer to offsetting the relaxation inherent in heat exchanger gaskets? Should they be routinely used to improve reliability and prevent leakage in heat exchanger joints? The short answer is "no." The limited amount of good they do is more than offset by added cost, increased complexity and added failure modes. To read the full study, download the complete technical notes, and learn how a proper tightening program can provide a better long-term solution, visit http://info.lewis-goetz.com/heat-exchanger-leak-solutions.
For more information, call Advanced Sealing at (562) 802-7782.
