OT Steam Hammering

Hi I have a heat exchanger supplied by steam at 6.5 bar

The steam goes into a automated ball valve and then a modulating valve, and into the HX. The condense line has a trap and a non return valve which goes into the condense header

The control scheme is to open the ball valve when the temperature is below the setpoint and close it when it is at setpoint +5

The modulating valve has a PID loop which is limited to 10% manual mode for 2 minutes before the PID kicks into auto and the valve opens to approx 80% and settles to around 25% and maintains the setpoint

The issue is that the ball valve has stainles steel ball and steam eats it in 8-10 weeks and the modulating valve lets by

On start up the steam hammers for for 2 mins at 10% but i am being told that increasing the 10% opeing may damage the piepework etc

Any suggestions welcome .. I am thinking of a automated condense drain line



system where the plant steam comes from a header and is reduced to 6.5 bar. This 6.5 Baris 6.5 bar. This is

The systems I have worked on were much higher pressure, 15-18 bar we were trying to keep the hot steam from turning to steam and staying water

We use butterfly valves for control, the damage will be done to your welds on the system... that said, I have hammered systems so hard it set off alarms in the parking lot by heating to fast, your hammering is coming from heating to fast, the worst hammering I have ever seen was from a oil/water heat exchange got a leak internally, that was bad news

Oil is much better to work with but a pain in the *** to clean up when you have a leak

Hi thanks for the reply.
The valve is opened from 0 to 10% over 2 minutes (the timer acc is divided over 10% and mapped to the output). I tried changing 2 mins to 10 mins as a test and simply had 8 more minutes of hammer

Based on you saying the hammer is too much steam I would be better off experimenting with making that say 5% or less

And as for oil i used to work in an rubber injection moulding place and witnessed a hose break and the hot hydraulic oil spray everywhere. Luckily no one was injured

Can you also change the flow? sounds like you can increase your PV side a lot, is your heat ex steam to steam or oil to steam?

If oil to steam try slowing down the oil or speeding up the flow on the steam side, if you can speed up the steam you can increase the system temp without flashing/hammering they system, the issue you are having is heating a small sample of your system and not the whole system so buy increasing the flow you can put the same BTU or more to the system and not flash

Hi . No the medium being heated is circulating with a DOL pump so no speed control. The medium is dowcal. It will be at approx 22C when the heating starts.

Thanks

Is it possible for you to fire up the boiler with ball and control valve opened, as to slowly heat up your entire steam system?

How often do you start your HX from "cold"?

The system is only used maybe once a fortnight for 4 to 5 hours. It is a slow process. I suggested hand valves but that was dismissed as an idea.
I am told if I open the valves 100% been for a short duration it may risk the pipework and flanges due to the steam hammering and thermal shocks. I was thinking of a short blast at say 50% to clear the condense but have been told it would be dangerous. I am thinking of passing it to a process company to review the mechanical design

Thanks

Quote:"The issue is that the ball valve has stainless steel ball and steam eats it in 8-10 weeks and the modulating valve lets by".

I have used these valves on steam heat exchanger applications: http://www.setpointis.com/Portals/0...s/ControlValve-Masoneilan_Rotary-Setpoint.pdf.

Make sure you order Stellite Plug and seat. The valve will last for years.

Thanks for the valve idea. I do prefer a proper solution like that rather than programming a fix. I will see what's available over here

Have a good weekend

This may help as well: http://www.boydeng.com/WaterHammer.htm.
See figure 1.