Steam & Excursion > Question about Superheaters

I know there were various types of superheaters, e.g.Type A, Type E, etc., used during the steam era. What factored into the use of a certain type of superheater (boiler size, number of flues,superheater design, etc.)? I think that I read recently of Type E superheaters being troublesome and being swapped out for Type A replacements. What's up with that? Help from those of you in the know is appreciated.

rcall31060

Type E superheaters usually had more superheat heating surface than a Type A , resulting in higher final steam temperatures. This can lead to problems with valve lubrication if quality valve oil cannot be obtained.

All of my experience with Superheat (in a railroad application) is with the type A...each element makes 4 passes through the same tube. I think somewhere around 750 degrees F was about the limit on temp. I have personally witnessed 4960 at just over 700 degrees which is damned good. The higher the degree of Superheat, the more volume and heat content per unit of steam (usually measured in lbs. steam/hour).
Coincidentally, 750 degrees F was our operating limit in #1 Power Plant at Chevron & also in our newer Cogen...and this was at 800 and 850 lbs. pressure. Most of that steam went to 4 turbine generators so lubrication was not in issue.

Tom

PS Sam, good to see you on this board.

Weren't the Type-E's more prone to cinder-plugging?