| 摘要 |
<p>A steam heated web processing roll includes a fully enclosed steam and condensate flow-through system which maintains the roll end walls at approximately the same operating temperature as the functional cylindrical outer roll shell at normal rotational speeds. The closed loop system also assists in purging non-condensible gases from the steam path. At low roll speeds or when the roll is stopped, a valving system closes all of the condensate return paths except one or more of the lowermost paths from which condensate pooling in a sump at the bottom of the roll is withdrawn. This prevents undesirable cooling of the lower portion of the roll as compared to the remaining portion, thereby reducing the possibility of bowing of the roll by thermal distortion. <IMAGE></p> |
