Heat exchanger help needed

David Van Wickler

THIS is what the Wall is all about. In 1-day I have 4 things to look at and think about. I'm not the greatest steam guy. I am the greatest water guy.........ouch my arm hurts from patting my back!! But seriously, this is the first time I have a shell and tube problem. It is easier than a brand new install problem. The original HX ran for years, then mysteriously popped. Then the relacement popped and then the second replacement popped. It's not hard to figure out that 3 heat exchangers bundles pop in six months would be the bundles fault.

I have sent in my security clearance info. We'll find out if I'm allowed into the prison.

I'll be sure to tape my a-- wth duct tape!!!!!!!!

TY

DVW

David Van Wickler_3

2nd failed heat exchanger - help needed

Going in blind - 8" shell and tube, 2 pass 7 feet long. Claim is that first one leaked where the tubes are pressed into the header. The factory claims that it's caused by steam hammer (I'm assuming water or condensate hammer). The new bundle was installed and it to has failed (hmmmmm I wonder why).

Now I am the luck chap that has to go into the metropolitan correctional facility to look at the stinkin thing and say something intelligent.

Maybe Blooberg will meet me there, since they don't have the money to pay for a third!

The question is; Is the hammer from a slug of condensate impinging on the tube bundle? What should I look for?

Art Pittaway

Hammer

is usually a system problem. Is it a new install or has it worked for years and then had problems after_______was changed. Is the return overhead or does it drain down into a vented reciever? Look for the control valve, is it modulating? If it's overhead return and modulating valve the shell is sometimes partly full of condensate. What kind of trap does it have, it should be an F&T, the others don't vent air well enough. Does it have a vaccuum breaker on the shell, it should. When the steam shuts off a vacuum forms that will amaze you! The trap usually has a check valve so nothing gets out with a vacuum and the water just backs up.Well drained S&T HX's don't hammer. Saw one where the guy claimed that he never heard it hammer. Asked one of the girls on the assembly floor and she said the room sounded like someone was trying to come through the wall. Ooops.
Art

Tony Conner

Look At...

...the temp control valve arrangement. Is it a proper, modulating TCV, or is it the cheap-out solenoid valve slamming on and off? Either way, is the steam line ahead of the TCV properly trapped so condensate doens't accumulate ahead of it while it's closed on low loads? Slamming condenste into the HX in this arrangement will show up as dents on the tube bundle just under the steam inlet to the shell. It'll look just like someone has pounded on the outside of the bundle with a hammer.

Solenoid valves in steam service just give me the willys. They're not modulating, and, to amplify that shortcoming, almost always grossly oversized, so (especially at partial loads) they slam off-on-off-on over and over. They just beat the snot out of everything.

On the other end, does it have the right type and size of steam trap? Does the trap discharge piping gravity drain, or is it the usual "install it waist high, and run the condensate piping up 15 feet to the ceiling? If the condensate drains properly by gravity, is there a vacuum breaker?

Is there a liquid side relief valve? The boys aren't bottling-up the liquid side while the steam can still get in through a valve that passing, are they? There can be some pretty impressive hydraulic pressures show up, but usually, you leak at a gasket or valve packing before anything else gives.

On the other hand, it has been known to happen that a bundle gets installed without all of the tubes being properly rolled into the tube sheet. I know of one instance where NONE of the tubes were rolled AT ALL. So much for that manufacturer's greatly ballyhoo-ed quality assurance program.

Art Pittaway

Hey Dave, How did it go??

Did the 2 minute HX seminar help you get it all figured out or are you still in the can because you couldn't give them an answer right away.??
Just wondering,
Art