Discussion in 'Boat Design' started by saeedfa, Jul 15, 2020.

1. Joined: Aug 2013
Posts: 21
Likes: 1, Points: 3, Legacy Rep: 10
Location: iran

### saeedfaJunior Member

Ad Hoc you say as a general regulation we can use the pressure at 1/3rd from the base of any vertical girder ?
this is my important question.

if i do the calculation for a tank, so TANSL said right, we must consider the height of ventilation pipe on deck, so the hydro static pressure on the top of the bulkhead were not zero, but in my case this is a bulkhead that separate the engine room from steering room so in this case ad Hoc say correct there is no need to consider the height of ventilation air above deck so the pressure at the top of the bulkhead may be zero.

2. Joined: Sep 2011
Posts: 6,117
Likes: 270, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

If it is a watertight bulkhead, even if you are not a tank bulkhead, you must consider a certain loading height determined by regulations.

3. Joined: Aug 2013
Posts: 21
Likes: 1, Points: 3, Legacy Rep: 10
Location: iran

### saeedfaJunior Member

But the attached file is DNVGL-HSLC-Pt3-CH3, and that say vertical distance in m from the load point to the top of bulkhead

#### Attached Files:

• ###### 11111111.PNG
File size:
48.1 KB
Views:
11
4. Joined: Aug 2013
Posts: 21
Likes: 1, Points: 3, Legacy Rep: 10
Location: iran

### saeedfaJunior Member

this is the reference in DNVGL-HSLC-Pt3-Ch3, for tank bulkhead
and that say vertical distance in m from the load point to the top of air pipe or filling station.

#### Attached Files:

• ###### 22.PNG
File size:
74.1 KB
Views:
13
5. Joined: Sep 2011
Posts: 6,117
Likes: 270, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

... or flooded waterline,....

saeedfa likes this.
6. Joined: Aug 2013
Posts: 21
Likes: 1, Points: 3, Legacy Rep: 10
Location: iran

### saeedfaJunior Member

yes you right
the flooded waterline must be check in stability booklet and then if the flooded waterline upper than the top of bulkhead the pressure must be calculated according to the flooded waterline

TANSL likes this.
7. Joined: Jan 2005
Posts: 2,092
Likes: 226, Points: 63, Legacy Rep: 1110
Location: Philippines

### rxcompositeSenior Member

If this is a watertight bulkhead, I would treat it the way of AH as I do not have to worry about the deck opening except possibly a manhole.

Now if it this is is a tank bulkhead, there is a filling pipe, a breather and a sounding pipe. The appropriate rules must then be used for the height/location, which is in agreement with International Load Line and SOLAS rule for downflooding.

There are many types of bulkheads and the construction and test procedures for them are very distinct from each other.

hoytedow and Ad Hoc like this.
8. Joined: Oct 2008
Posts: 6,509
Likes: 560, Points: 113, Legacy Rep: 2488
Location: Japan

Exactly.
Thus one needs to understand the theory how the pressure is calculated from theory, thus provides an understanding of the mechanism at play, which has nothing to do with rules/regulations.
Once that is understood, one can then progress to how the pressure is calculated for a WTB (theory) v how regulations interpret that structural member (theory + Class requirement).
And the location of the bulkhead (being reviewed by Class regulation) is an import feature of that...no magic to it.. despite what others appear to be suggesting..

9. Joined: Sep 2011
Posts: 6,117
Likes: 270, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

No one is suggesting anything. It is about understanding what the DNVGL rules say. You have said something that suggests that you have not understood what that regulation says.
Simple

10. Joined: Sep 2011
Posts: 6,117
Likes: 270, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

Precisely for this reason, because there are many types of watertight bulkheads, the design pressure at the top of a bulkhead may not be zero.

11. Joined: Aug 2013
Posts: 21
Likes: 1, Points: 3, Legacy Rep: 10
Location: iran

### saeedfaJunior Member

please see the picture i attached above from DNVGL rule. according to the rule, if you calculate the simple watertight bulkhead, you must consider the "h" as vertical height from load point to the top of bulkhead or flooded water line if deeper.
if you calculate the tank watertight bulkhead, you must consider the "h" as vertical height from load point to the top of filling or air pipe.

12. Joined: Sep 2011
Posts: 6,117
Likes: 270, Points: 93, Legacy Rep: 300
Location: Spain

### TANSLSenior Member

You can have a watertight bulkhead that does not reach the main deck. What would be the height h in that case?

Last edited: Jul 20, 2020
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.