Tek-Tips is the largest IT community on the Internet today!

Members share and learn making Tek-Tips Forums the best source of peer-reviewed technical information on the Internet!

Register Log in
  • Congratulations cowski on being selected by the Eng-Tips community for having the most helpful posts in the forums last week. Way to Go!

Pressure dropped during hydrotest

Status
Not open for further replies.
Sam Low

Sam Low

Mechanical
Joined
Oct 30, 2019
Messages
31
Location
MY
Hi All,

As you all know, during hydrotest, the pressure might drop dramatically in the pressure vessel when the ambient temperature reduced (eg. in a rainy day) accordingly. Do you guys know the theoretical reason behind?

This is my understanding..

According to the thermodynamic first law, assumed the expansion workdone is zero since the pressure vessel is a closed system, the heat released from the system is completely converted from the internal energy of the water molecules. Therefore, the pressure of the water (system) dropped.


In another point of view, the ambient temperature reduced resulted in the contraction of the volume of water and steel. The contraction of water is more than the contraction of steel and caused the water inside the pressure vessel dropped. The pressure dropped could be calculated by referring to the bulk modulus of water.


Sorry for my poor explanation.. Hope somebody is on the same page with me and can understand what I am trying to explain.
Thanks in advance.
 
Sort by date Sort by votes
Was it a real case to see the temperature changed during the hydro of the pressure vessel?

Normally, the hydro of the vessel is conducted above a minimum temperature and held for about one hour. The temperature of the testing medium may need to be maintained during the hydro duration
 
Upvote 0 Downvote
HI mk3223,

Yup, It did happen in real case.. I agreed that the temperature shall be maintained.
However, there might be raining while the hydrotest is conducted halfway, which we have encountered this situation before.
 
Upvote 0 Downvote
The water is contracting faster than the steel, and reducing pressure accordingly.
 
Upvote 0 Downvote
See faq391-224. However your vessel must be a very small one, to see a significnt change in temperature in an hour or two. Moreover the rain could cause first the cooling of the wall, thus causing initially a pressure rise. Are you trying to explain something you don't want to admit?[wink]

prex
[URL unfurl="true"]http://www.xcalcs.com[/url] : Online engineering calculations
[URL unfurl="true"]https://www.megamag.it[/url] : Magnetic brakes and launchers for fun rides
[URL unfurl="true"]https://www.levitans.com[/url] : Air bearing pads
 
Upvote 0 Downvote
Prex, typically if a hydrotest fails pressure goes to 0 fairly rapidly, it doesn’t just drop slightly.
 
Upvote 0 Downvote
Status
Not open for further replies.

Similar threads

Samingme755
  • Locked
  • Question Question
Pressure drop for heat exchangers
Replies
5
Views
4K
MJCronin
MJCronin
Mechinspqoal
  • Locked
  • Question Question
Cooling Water Service Heat Exchanger Hydrotest Tube Leaks
Replies
8
Views
1K
georgeverghese
georgeverghese
Diulf
  • Locked
  • Question Question
Pressure in closed condensate tank
Replies
5
Views
982
EdStainless
EdStainless
PeterJAM
  • Locked
  • Question Question
Calculating pressure after steam is condensed
Replies
6
Views
1K
georgeverghese
georgeverghese
Ameen1985
  • Locked
  • Question Question
Can the air pressure in tank be higher than the compressor outlet pressure?
Replies
11
Views
2K
TugboatEng
TugboatEng

Part and Inventory Search

Sponsor

Back
Top