3 replies to this topic

[Rahul Jha]

Hello,

I am a fresh gard from university and have been working on a Plant Start Up. I have been asked following questions.

1.) A line will be flushed with water and dried using air. The end will be closed but not air seal. The line will be commission after a year, Do we have to worry about corrosion.
2.) How long one needs to dry with air to avoid corrosion in the line?
3.) A CS line is been steam blown, what is the accpetable temperature rise rate to avoid any kind of termal stress on the line.

I have been trying to find some kind of spec which might helps me to answer these question. To my dissappointment I failed to find one. Please help me.

Thanking you.

Regards,
Rahul Jha

Edited by Rahul Jha, 26 April 2010 - 10:33 PM.

[Zauberberg]

1.) A line will be flushed with water and dried using air. The end will be closed but not air seal. The line will be commission after a year, Do we have to worry about corrosion.
2.) How long one needs to dry with air to avoid corrosion in the line?
3.) A CS line is been steam blown, what is the accpetable temperature rise rate to avoid any kind of termal stress on the line.

1. Yes. Unless you perfectly dryout the system and apply conservation under inert atmosphere, the general corrosion will occur. You would be surprised to see how much rust we found inside the system during commissioning of Amine Plant. The lines were blown a couple of months before the pre-mechanical completion.

2. It depends what do you plan to do with this line, and also on how big is the line. Normally you would flush all the water out by using Nitrogen or Instrument Air and keep it preserved. After certain time, you may wish to check the dew point of Nitrogen/Air from the line.

3. No concerns regarding "temperature rise" - at least not known to me.

[Rahul Jha]

1.) A line will be flushed with water and dried using air. The end will be closed but not air seal. The line will be commission after a year, Do we have to worry about corrosion.
2.) How long one needs to dry with air to avoid corrosion in the line?
3.) A CS line is been steam blown, what is the accpetable temperature rise rate to avoid any kind of termal stress on the line.

1. Yes. Unless you perfectly dryout the system and apply conservation under inert atmosphere, the general corrosion will occur. You would be surprised to see how much rust we found inside the system during commissioning of Amine Plant. The lines were blown a couple of months before the pre-mechanical completion.

2. It depends what do you plan to do with this line, and also on how big is the line. Normally you would flush all the water out by using Nitrogen or Instrument Air and keep it preserved. After certain time, you may wish to check the dew point of Nitrogen/Air from the line.

3. No concerns regarding "temperature rise" - at least not known to me.

Thanks for your answer:

Regarding Ans 2: The line will be used to transport the RCW. While flushing a film of water will stay in the pipe line. How long do I need to blow with instrument air to make the pipe fully dry? What do mean by afer certain time ( how long, months, year etc.) Or do you mean keep blowing for hours and then check the dew point of the air? Then question is how do I determine the dew point of the air? Is there any instrument available to check the dew point.

Thanks again.

[AZIZ_MN]

[quote name='Rahul Jha' date='27 April 2010 - 05:30 PM' timestamp='1272370239' post='38531']
[quote name='Zauberberg' date='27 April 2010 - 12:32 AM' timestamp='1272343341' post='38514']
[quote name='Rahul Jha' date='27 April 2010 - 03:29 AM' timestamp='1272339579' post='38513']
1.) A line will be flushed with water and dried using air. The end will be closed but not air seal. The line will be commission after a year, Do we have to worry about corrosion.
2.) How long one needs to dry with air to avoid corrosion in the line?
3.) A CS line is been steam blown, what is the accpetable temperature rise rate to avoid any kind of termal stress on the line.[/quote]

1. Yes. Unless you perfectly dryout the system and apply conservation under inert atmosphere, the general corrosion will occur. You would be surprised to see how much rust we found inside the system during commissioning of Amine Plant. The lines were blown a couple of months before the pre-mechanical completion.

2. It depends what do you plan to do with this line, and also on how big is the line. Normally you would flush all the water out by using Nitrogen or Instrument Air and keep it preserved. After certain time, you may wish to check the dew point of Nitrogen/Air from the line.

3. No concerns regarding "temperature rise" - at least not known to me.
[/quote]

Thanks for your answer:

Regarding Ans 2: The line will be used to transport the RCW. While flushing a film of water will stay in the pipe line. How long do I need to blow with instrument air to make the pipe fully dry? What do mean by afer certain time ( how long, months, year etc.) Or do you mean keep blowing for hours and then check the dew point of the air? Then question is how do I determine the dew point of the air? Is there any instrument available to check the dew point.

Thanks again.
[How long do I need to blow with instrument air to make the pipe fully dry?]
Hi Rahul,
As Zuaberberg stated in point-2 you have to do nitrogen purging from each and every drain points which are provided on line,if line is too long then care to be taken of no stagnant water got trapped within 'U' loops, and nitrogen purging time is depends how fast you succeed to get dew point of line.
Best method is to remove rust from the line is gasket blasting, in this method we have to connect nitrogen or instrumentair on one end of the pipeline and other end we have to install 150'pound rating gasket with ring flange instead of puting endblind,pressurise the line untill gasket blast, this we have to repeat till no rust observed from other end of the line, then you can remove ring flange and provide endblind to other end.
Once you get dewpoint within limit on each drain point pressurise the line to certain pressure till the commissioning of the line.
best luck and regards