What is the difference between bed limiters and bed hold-downs?
Bed limiters are used with metal or plastic tower packings to prevent expansion of the bed at high flow rates. They are designed with openings small enough to prevent the passage of individual pieces of packing. Bed limiters are always attached to the tower wall by means of a support ring or bolting to clips. Bed hold-downs are used with ceramic packings to prevent the upper portion of the bed from fluidizing and breaking up at high flow rates. The hold-down rests directly on the packed bed and relies solely on its weight to restrict bed movement. In the event of a surge or upset condition, the bed hold-down does not have sufficient weight to prevent damage.
