19 replies to this topic

[kaidlut]

Dear all,

 

Our factory has added a pipeline for the recovery of steam condensate. Prior to this, the condensate was discharged into the waste water sump on site through the drain valve behind the steam trap.

 

But about 8 days after the pipeline was put into use, there was a water hammer，could you please help me analyze the causes of water hammer and propose solutions？Thanks！

 

The process is shown as below： 

 

Here are some more information：

 

1. Steam condition：0.43Mpa-G，190℃，500kg/h；The condensate is cold and there is no possibility of secondary flash evaporation；

 

2. The new steam condensate pipeline（red color） size DN50, length 150m, including 17  90° elbows, highest point 8m above ground, T361 water tank height 5m；T361 is an atmospheric pressure tank that vent to the atmosphere；

 

3. Check the discharged steam condensate, no steam drifting, showing the steam trap can close tight on steam；

 

4. Inquire with the operator that the water hammer occurred in the pipeline in front of the steam trap。

 

 

Attached Files

•  流程图.jpg   28.21KB   0 downloads

[breizh]

Hi,

Consider this link to support your query.

Water Hammer in Condensate Transport Piping | TLV

Breizh

[katmar]

What does "the condensate is cold" mean?  If the process in E802 is cold enough to ensure that the condensate is discharged "cold" then the hammering (cavitation) may be happening on the steam side of E802.

 

If you are measuring the condensate as "cold" only when it reaches T361 it might be because the condensate line is so oversized. It will take nearly an hour to travel from the steam trap to the tank and the temperature in the tank is no indication of what is happening at the trap.

 

Please don't take my questions as criticism of your post. The detail you have provided and the excellent flowsheet make it way above the average standard we see here.

[breizh]

Hi,

In addition to my previous reply, a document to support your investigation. You will find comments similar to those done by Katmar.

Definitely condensate line size is a question. V< 0.1 m/s should be (1.5 to 2 m/s).

10 mm should be the right ID .

If you change the pipe DN , you will have to calculate the head loss and check the impact on the quality of the condensate. 

Do you have a way to measure the pressure/temperature along the piping? 

Is your condensate line insulated?

Note : Your steam is overheated , saturated temp is 146 C at 0.43 MPa.

Good luck

Breizh 

Attached Files

•  A-Practical-Guide-to-Steam-and-Condensate-Enginnering_Bermo_Ari-Armaturen.pdf   5.96MB   10 downloads

[shvet1]

What exactly do you mean "there was a water hammer"?

 

no steam drifting

 

Do you understand the concept of flash steam? Do you understand that "condensate" coming into this tank is 2-phase flow?

https://toolbox.tlv....generation.html

 

steam trap can close tight on steam

 

Why do you believe so?

Edited by shvet1, 08 September 2024 - 11:36 PM.

[kaidlut]

Sir，thanks to your reply。

when i said  "the condensate is cold"，I mean the condensate came out of drain valve behind the steam trap is at room temperature。We do not reclaim the heat of the condensate. We reclaim this condensate because the cost of wastewater treatment is high。

What does "the condensate is cold" mean?  If the process in E802 is cold enough to ensure that the condensate is discharged "cold" then the hammering (cavitation) may be happening on the steam side of E802.

 

If you are measuring the condensate as "cold" only when it reaches T361 it might be because the condensate line is so oversized. It will take nearly an hour to travel from the steam trap to the tank and the temperature in the tank is no indication of what is happening at the trap.

 

Please don't take my questions as criticism of your post. The detail you have provided and the excellent flowsheet make it way above the average standard we see here.

[kaidlut]

Sir，thanks to your reply。in order to solve the problem of water hammer，DO I need to reduce the diameter of the pipe to 10mm？

Hi,

In addition to my previous reply, a document to support your investigation. You will find comments similar to those done by Katmar.

Definitely condensate line size is a question. V< 0.1 m/s should be (1.5 to 2 m/s).

10 mm should be the right ID .

If you change the pipe DN , you will have to calculate the head loss and check the impact on the quality of the condensate. 

Do you have a way to measure the pressure/temperature along the piping? 

Is your condensate line insulated?

Note : Your steam is overheated , saturated temp is 146 C at 0.43 MPa.

Good luck

Breizh 

[breizh]

Hi,

No other option to recycle the steam condensate? I do understand the issue of WWT cost. 10 years' experience in China.

My experience has been to flash the condensate to atm and recycle to cooling water as make up water .Of course, you need to control the quality of the water prior to recycle to CT. 

Consider the technology in the link attached :

https://content.spir...e89ff13b118bcd 

 

Breizh 

[shvet1]

@kaidlut

You do not know the actual point of water hammer, correct? You know nothing other that the system makes some "knocking sound", correct?

 

You problem is TV8004.

HE is oversized, that causes flooding of hot side by condensate and overcooling condensate, TV8004 closes and creates stall conditions in HE, stall causes "hunting" (cycling oscillation of steam/condensate flowrate and flooding level) and water hammer in HE and condensate 

 

See some explanation

https://www.tlv.com/...-phenomenon-pt1

 

Note that TV8002 has a potential to create vacuum in HE. You have no check valve downstream ov steam trap so condensate is able to backflow through trap from recovery line to HE. That can cause situation when cold water from tanks goes upward to pockets in recovery line and implodes when come in contact with 2-phase condensate.

 

Note that "knocking sound" is not a waterhammer. Waterhammer is when piping are poping several inches up and are thrown from supports.

Edited by shvet1, 09 September 2024 - 11:45 PM.

[kaidlut]

Thank you sir！

 

Actually，I do not know the actual point of water hammer，the operator told me it  occurred in the pipeline in front of the steam trap。it took place in the night，and when it  occurres，the operator opened the vavle after the steam trap，discharged the condensate to the ground，then the sound disappear。

 

Steam control valve TV8004 do shut off for 30 minutes every 12 hours，for some process reason. What confuses me is that the water hammer occurred 8 days after the pipeline was put into use。

 

I do want to adjust the steam trap，I have reviewed the manual of  steam trap.  “steam Traps will operate against very high back pressures, but the discharge temperature and capacity will be correspondingly affected. For effective operation when the back pressure exceeds 30%, the clearance should be increased progressively as described below.”，so  I guess the recycling pipeline has increased back pressure.

 

SO next step，i am going to turn the adjusting ring anti-clockwise, which will increase the valve clearance to Increase temperature / quantity of condensate discharge and  prevent backing up of condensate。

 

would this be help? thanks!

 

 

 

 

 

@kaidlut

You do not know the actual point of water hammer, correct? You know nothing other that the system makes some "knocking sound", correct?

 

You problem is TV8004.

HE is oversized, that causes flooding of hot side by condensate and overcooling condensate, TV8004 closes and creates stall conditions in HE, stall causes "hunting" (cycling oscillation of steam/condensate flowrate and flooding level) and water hammer in HE and condensate 

 

See some explanation

https://www.tlv.com/...-phenomenon-pt1

 

Note that TV8002 has a potential to create vacuum in HE. You have no check valve downstream ov steam trap so condensate is able to backflow through trap from recovery line to HE. That can cause situation when cold water from tanks goes upward to pockets in recovery line and implodes when come in contact with 2-phase condensate.

 

Note that "knocking sound" is not a waterhammer. Waterhammer is when piping are poping several inches up and are thrown from supports.

Edited by kaidlut, 10 September 2024 - 01:08 AM.

[shvet1]

would this be help?

Wouldn't as at deals nothing with stall

 

You should start with studying how steam&condensate systems work, how those should be designed, and what yours looks like. You are seeking for an "shortcut" for a "congential desease" of this system, if the real life does work such way then engineers would be not needed.

 

Open the links above and spent couple days studying material in those.

Edited by shvet1, 10 September 2024 - 01:22 AM.

[katmar]

The conclusions drawn by shvet1 and myself are basically the same, and are reinforced by your confirmation that the condensate immediately after the steam trap is at room temperature. This tells us that either the HE E802 is oversized or the process is too cold - basically the same thing and meaning that the rate of heat removal from the steam is too high and cold condensate is coming in contact with the steam and causing cavitation - which your operator is reporting as water hammer (and that is a perfectly reasonable conclusion for them to come to).

You can confirm this conclusion by installing a pressure gauge between the valve TV8004 and the HE E802.

Installing a smaller line to the water tank will not help. If you are not recovering the heat from the condensate then it does not matter how long it takes for the condensate to reach the tank. In fact making the line smaller would make the problem worse because it would increase the back pressure.

When problems like this arise at the same time as changes in the system then you can fairly confidently suspect that the changes are the cause of the problem. The increased static head that the condensate leaving the steam trap has to overcome will make it more likely that the cold condensate is pooling in the HE and causing the problem. Can the line be re-routed at a lower level?

I support your idea of adjusting the trap to increase the condensate removal rate, or maybe call in the steam trap representative for them to look at the physical installation and recommend the correct trap. My experience has been that the steam trap suppliers train their people well and they are able to help with these seemingly mysterious problems.

[breizh]

HI,

Before jumping to conclusions, share with us a material and heat balance of your system (HX, Condensate). Thanks also to provide a cartography (P, T) of your condensate line as requested in my earlier reply. 

Probably good also to perform this analysis on the old system (drain to WWTP) and after modification (transfer to water storage). 

In any project, it's always good to issue MOC (modification of change) .

Good luck

Breizh 

[Dacs]

With the information at hand, I care to guess that you're sending partially condensed steam at the main condensate pipeline.

[Dacs]

 

 

Waterhammer is when piping are poping several inches up and are thrown from supports.

 

While water hammer certainly causes that, it does not define what hammering is. That can also be caused by slug/churn flow, especially at elbows.

 

Hammering is a sudden change in velocity of fluid (mostly due to sudden closure of valves) and this sudden change results in sudden increase in pressure at the point of change. A related (but not technically "hammering") phenomenon is what we call "column separation" where vapor forms on an otherwise liquid-filled pipe, due to pressure dropping below its vapor pressure. This is the opposite of hammering, as it happens downstream of the closing valve. This happens because the fluid has momentum as it travels the pipe and the valve closure prevents it from getting replaced.

[kaidlut]

I learned a lot  about "stall" by reading your link. thanks.

By the way,the steam trap is MODELS SPF from Velan Valves Ltd I checked the manual of  steam trap, it describe as“For traps installed In a closed return line; any excess back pressure, or reverse flow will act under the piston, working as a temporary check valve, closing the main valve preventing back flow.” 

Can it be understood that there is no possibility of backflow here？

would this be help?

Wouldn't as at deals nothing with stall

 

You should start with studying how steam&condensate systems work, how those should be designed, and what yours looks like. You are seeking for an "shortcut" for a "congential desease" of this system, if the real life does work such way then engineers would be not needed.

 

Open the links above and spent couple days studying material in those.

[kaidlut]

Yes, HE E802 is oversized . process feed is heated from 8℃ to 30℃ according to PROCESS DATA SHEET，but actually it is heated from 24℃ to 27℃.

 

By the way,the steam trap is MODELS SPF from Velan Valves Ltd I checked the manual of  steam trap, it describe as“For traps installed In a closed return line; any excess back pressure, or reverse flow will act under the piston, working as a temporary check valve, closing the main valve preventing back flow.” 

Can it be understood that there is no possibility of backflow here？

 

I will adjust the trap and see what will happen ? thanks.

The conclusions drawn by shvet1 and myself are basically the same, and are reinforced by your confirmation that the condensate immediately after the steam trap is at room temperature. This tells us that either the HE E802 is oversized or the process is too cold - basically the same thing and meaning that the rate of heat removal from the steam is too high and cold condensate is coming in contact with the steam and causing cavitation - which your operator is reporting as water hammer (and that is a perfectly reasonable conclusion for them to come to).

You can confirm this conclusion by installing a pressure gauge between the valve TV8004 and the HE E802.

Installing a smaller line to the water tank will not help. If you are not recovering the heat from the condensate then it does not matter how long it takes for the condensate to reach the tank. In fact making the line smaller would make the problem worse because it would increase the back pressure.

When problems like this arise at the same time as changes in the system then you can fairly confidently suspect that the changes are the cause of the problem. The increased static head that the condensate leaving the steam trap has to overcome will make it more likely that the cold condensate is pooling in the HE and causing the problem. Can the line be re-routed at a lower level?

I support your idea of adjusting the trap to increase the condensate removal rate, or maybe call in the steam trap representative for them to look at the physical installation and recommend the correct trap. My experience has been that the steam trap suppliers train their people well and they are able to help with these seemingly mysterious problems.

[Pilesar]

As I understand it, this stream trap opens and closes based on temperature. I suspect reverse condensate flow into the exchanger might be possible since the steam pressure inside the exchanger is often lower than the pressure in the condensate line. Water hammer is tough to troubleshoot since the noise is not always in the location where the problem starts. Check whether the steam trap downstream piping incorrectly allows the condensate header to flow in reverse -- the steam trap discharge piping should enter the top of the condensate header, not the bottom.

Consider using a pressure powered condensate pump. These act as a steam trap that pushes the condensate forward using steam pressure. See an example here: https://www.control-...ered-pump.html 

[breizh]

Hi,

The ultimate option could be an underground sump, let say 1m 3, where the condensate is discharged, from which a submersible pump or self-priming pump will transfer the condensate to the storage tank using the new pipeline DN 50. The pump will be started and stopped using level switches High and low.

The other option was to use a condensate pump as stated in my answer yesterday.

Breizh

[shvet1]

 

By the way,the steam trap is MODELS SPF from Velan Valves Ltd I checked the manual of  steam trap, it describe as“For traps installed In a closed return line; any excess back pressure, or reverse flow will act under the piston, working as a temporary check valve, closing the main valve preventing back flow.” 

Can it be understood that there is no possibility of backflow here？

 

Yes, it can

 

Note that SPF model is actually bimetallic type. Bimetallics let pass through a fluid under certan temperature, in your case adjusted manually by pilot piston. This point is critical as other types ensure passing through a liquid regarding temperature. Bimetallics are much more sensitive to incorrect HE operation than other types are.

 

Seems like this HE needs some an attention of an experienced engineer or technician.

Edited by shvet1, 10 September 2024 - 11:09 PM.