Water Bath Heater Shell side # Design Pressure & Hydrotest presure

[adsharma]

I m currently executing a water bath heater(WBH) for one of our client.
WBH shell is an atmospheric vessel(3200 ID X 6500mm long).
It contains a coil bundle at top which has crude oil flowing inside (Operating Pressure 3 to 5barg @ 25 to 45degC).
This crude oil will be heated by the water bath in the WBH shell.
Water will receive the heat input from fire tube placed at the bottom of the WBH shell.
Coil is designed for 25barg @ 100degC & will be hydrotested for 1.5 times the design pressure.
it is ok till now.
But the problem is that client is also asking us to design the WBH shell for 5barg @100 degC & hydrotest it @1.5 times the D.P.
Which we feel is neither the good engineering practice nor economical also.
WBH shell is an atmospheric vessel and in general practice it is designed for FULL of water & also hydrotested @ full of water.
Client told us that although the WBH shell will never ever be subjected to pressure in its entire life period but they are considering 5 barg design pressure for WBH shell because of tube/coil rupture case.
I request to all of you please give your view on this ( WBH Design pressure & hydrotest pressure).
We don’t want to go with so much high design & hydrotest pressures because it is not economical for us.
How can we convey our end client?
Thanks for giving your valuable time in reading this long post.
Appreciate if any one can revert with your vies on this. please!
Coil is designed for 25 barg with corrosion allowance & it has MAWP=32barg. How could rupture occurred? When operating is just 3 to 5 barg.
Also there is PSV( Set pressure @ 25barg) on crude oil line.

[khalid655]

I m currently executing a water bath heater(WBH) for one of our client.
WBH shell is an atmospheric vessel(3200 ID X 6500mm long).
It contains a coil bundle at top which has crude oil flowing inside (Operating Pressure 3 to 5barg @ 25 to 45degC).
This crude oil will be heated by the water bath in the WBH shell.
Water will receive the heat input from fire tube placed at the bottom of the WBH shell.
Coil is designed for 25barg @ 100degC & will be hydrotested for 1.5 times the design pressure.
it is ok till now.
But the problem is that client is also asking us to design the WBH shell for 5barg @100 degC & hydrotest it @1.5 times the D.P.
Which we feel is neither the good engineering practice nor economical also.
WBH shell is an atmospheric vessel and in general practice it is designed for FULL of water & also hydrotested @ full of water.
Client told us that although the WBH shell will never ever be subjected to pressure in its entire life period but they are considering 5 barg design pressure for WBH shell because of tube/coil rupture case.
I request to all of you please give your view on this ( WBH Design pressure & hydrotest pressure).
We don’t want to go with so much high design & hydrotest pressures because it is not economical for us.
How can we convey our end client?
Thanks for giving your valuable time in reading this long post.
Appreciate if any one can revert with your vies on this. please!
Coil is designed for 25 barg with corrosion allowance & it has MAWP=32barg. How could rupture occurred? When operating is just 3 to 5 barg.
Also there is PSV( Set pressure @ 25barg) on crude oil line.

Thank you for posting the question,

1) If there is no tube rupture scenario exists then there is no PSV on crude line.Hence tube rupture scenario exists.
2) What is the max temperature of heating water in the bath.
3) Please follow the rule of 1/3 pressure for tube rupture case.
4) As you told MAWP is 32 barg then why not shell subjected to never ever 5 barg pressure???????.

[khalid655]

I m currently executing a water bath heater(WBH) for one of our client.
WBH shell is an atmospheric vessel(3200 ID X 6500mm long).
It contains a coil bundle at top which has crude oil flowing inside (Operating Pressure 3 to 5barg @ 25 to 45degC).
This crude oil will be heated by the water bath in the WBH shell.
Water will receive the heat input from fire tube placed at the bottom of the WBH shell.
Coil is designed for 25barg @ 100degC & will be hydrotested for 1.5 times the design pressure.
it is ok till now.
But the problem is that client is also asking us to design the WBH shell for 5barg @100 degC & hydrotest it @1.5 times the D.P.
Which we feel is neither the good engineering practice nor economical also.
WBH shell is an atmospheric vessel and in general practice it is designed for FULL of water & also hydrotested @ full of water.
Client told us that although the WBH shell will never ever be subjected to pressure in its entire life period but they are considering 5 barg design pressure for WBH shell because of tube/coil rupture case.
I request to all of you please give your view on this ( WBH Design pressure & hydrotest pressure).
We don’t want to go with so much high design & hydrotest pressures because it is not economical for us.
How can we convey our end client?
Thanks for giving your valuable time in reading this long post.
Appreciate if any one can revert with your vies on this. please!
Coil is designed for 25 barg with corrosion allowance & it has MAWP=32barg. How could rupture occurred? When operating is just 3 to 5 barg.
Also there is PSV( Set pressure @ 25barg) on crude oil line.

Thank you for posting the question,

1) If there is no tube rupture scenario exists then there is no PSV on crude line.Hence tube rupture scenario exists.
2) What is the max temperature of heating water in the bath.
3) Please follow the rule of 1/3 pressure for tube rupture case.
4) As you told MAWP is 32 barg then why not shell subjected to never ever 5 barg pressure???????.

[adsharma]

thanks khalid655 for your reply.
1. Noted. PSV is to prevent the over-pressurization. Set pressure = design pressure of coil i.e 25 barg.
2. Maximum temperature of heating water is 90degC.
3. 32 barg MAWP is for the coil & is the calculated value as per Clause UG-98 of ASME Section VIII Div.1, it is> design pressure of coil ( 25 barg). So in case there is any upset & pressure is >25barg PSV shall open to prevent the overpressure in coil. So tube rupture shall not happen. Hence WBH shell shall not be subjected to pressure.
Also i thing comes into my mind is that if coil rupture would be because of over-pressurization than WBH shell side should be designed for 25 barg instead of 5 barg.
Can u suggest how could one proceed?

[adsharma]

thanks khalid655 for your reply.
1. Noted. PSV is to prevent the over-pressurization. Set pressure = design pressure of coil i.e 25 barg.
2. Maximum temperature of heating water is 90degC.
3. 32 barg MAWP is for the coil & is the calculated value as per Clause UG-98 of ASME Section VIII Div.1, it is> design pressure of coil ( 25 barg). So in case there is any upset & pressure is >25barg PSV shall open to prevent the overpressure in coil. So tube rupture shall not happen. Hence WBH shell shall not be subjected to pressure.
Also i thing comes into my mind is that if coil rupture would be because of over-pressurization than WBH shell side should be designed for 25 barg instead of 5 barg.
Can u suggest how could one proceed?

[scipion]

hello,
it is not a commun practice
this kind of vessel require just hydotest pleinty of water
but if the owner or user require more ,you have to do it and he must pay more

regards

[khalid655]

Thank you for the reply , if tube rupture occurs just before the psv opening i.e. 24.5 what happens to the shell?????????