Steam/condensate hammer at low steam load

[mjpetrag]

Hi everyone

I have a question regarding hammering that occurs at low steam flow rates. So some background

There are 6 distillation column reboilers that run on 250# steam controlled with a steam control valve. The condensate outlet of each of these reboilers go to float traps on each respective reboiler condensate outlet pipe. The discharge piping of each of these traps tie into a common header and then dump into a flash tank set at 50#. Here's the issue

At low steam flow rates - specifically when we shut down the distillation train to boil the columns out, we experience hammering in the condensate return header to the flash tank, eventually leading to gasket failures.

I have to note that the condensate return header does not have a dip pipe down into the liquid level of the flash tank. Also, 4 of the 6 reboiler traps do not have check valves downstream of them. As soon as a gasket fails, and we get a large condensate leak, the hammering subsides.

I have a few theories on why this occurs, but I wanted to hear others' input and experience with this type of issue. Also I would like to know if anyone can point me in the right direction as far as a redesign of the system or things we can do to mitigate the issue.

-Mike

 

[katmar]

Hammering of this nature occurs when live steam comes in contact with cold (below saturation temperature) condensate. You need to look at high and low points in the condensate line and also what other lines (other than the 6 columns' reboilers) could be bringing either live steam or cold condensate into the header.

The lack of a dip pipe into the condensate tank is definitely a point of concern.

Why is the steam load low when boiling out the columns? Is the steam not fed to the reboilers for this operation?

A sketch of the piping, roughly to scale, would allow more specific comments.

Katmar Software - AioFlo Pipe Hydraulics

http://katmarsoftware.com

"An undefined problem has an infinite number of solutions"

 

[ione]

Have you the possibility of checking the differential pressure over the steam traps (upstream/downstream)? A reduced steam trap capacity due to poor differential pressure that deviates from that required for proper working might lead to condensate build-up and consequent hammering. As the flash tank works at a set pressure, a reduced upstream pressure at low flows could deprive the steam traps of the necessary driving force for an adequate discharge capacity.