The 7x11” cut out in the vent piping is wild. I can’t think of a reason for that to exist. I wish there was a little more investigation into why it was there, especially after being discovered on four of eight ships in the fleet.
Is it common on smaller vessels to have a common vent pipe for all fuel tanks? I’ve not really seen that.
On the fire response side, anyone have any opinions on the CG requesting CO2 release three and half hours after a team entering the space found the fire to be out? It doesn’t mention whether they had any reason to believe the fire may have relit or still been burning, but just as a precaution.
At some unknown time in the vessel’s 26-year history, a 7-inch-by-11-inch section of pipe had been cut into the top of a horizontal section of the 12-inch vent pipe on the D deck (see figure 9 and figure 10). The vent pipe ran from the lower engine room up to the compass deck. There were no records of this alteration and no records of approvals, nor were there any records of inspections of this unauthorized alteration. The cut out section of pipe had been replaced with a flexible sealant and then wrapped in tape
Essentially no issues with their conclusion. I’m aware of at least one ship that combined vent and overflow into a single system and some tanks are grouped so multiple main deck vents but the vent line where manifolded is self draining to the overflow tank.
Agree with you @tengineer1 but with a twist. Corrosion yes but the photos look like the opening is on the top of the pipe (page 18 shows looking down at the remaining accumulated diesel oil at the bottom of the pipe). So instead of it simply rotting through being the cause of the cut it could be that (since those photos also show the position of the window near a 90 elbow up) cutting the window may have been an effort to allow clearing scale from the vent line. Not unheard of but the repair plan is turned out to be a foolish act.
Also on my mind is not so much grouping the tank vents - provided the flow areas complied with class or flag rules and that an overflow tank was incorporated in the design of the vent/overflow line to prevent inadvertent transfers - but how about having the atmospheric vent terminus at 125 feet above the tank top? These are usually what 30” above the freeboard deck. 125 feet would be a head pressure of about 46 psi in the tank if it ever did overflow out the vent terminal of course and it would be less differential in the water. Hard to imagine that was the tank design pressure. Sure wouldn’t hydro the tank to that. Just makes this arrangement strange from yet another perspective. But back to the location of the vent terminus - what’s the thought process there? Better to give the superstructure a shower and out multiple deck suppers over the side than into a single vent containment on main deck?
The small section of the FO Diagram suggests what to me appears top be a really cheapo way to approach FO filling and transfer system design. Yes a single line to/from the tank but usually a manifold approach to provide fill valves (stop) and suction valves (stop-check). Old timey cast manifolds too expensive these days?Would be nice to see the complete diagram if we might learn something more.
Since the guy who ordered the valve was not the guy aboard another lesson might be better check the work orders in progress and look over the job/materials before assigning the work. Even though we all assume our reliefs do it right too. Apparently the assistants who installed the valve were not looking too deeply at the work/materials in hand either. Guy paid with his life, then again absence of alarms and level indication monitoring was all on the crew aboard. Pretty sad and so unnecessary.
Makes sense that they wanted to clean scale but for what reason? Was there a scale blockage? That seems unreasonable with that size vent pipe. Regardless it is evident that the repairs done were not properly documented and reported to class. Another example of a seemingly minor repair causing a major problem.
Another disaster with loss of life. Some thoughts. I think the NTSB report does not go deep enough.
Hydrocarbon tanks arrangements in the engine room.
Not uncommon to have all the fuel DB tanks tied to a common vent. This vent is NOT an overflow. There is a distinction between the two. Typically, the vent will originate from the overflow tank and other vents will be tied or manifolded to this line. The overflow tank will have a separate overflow line terminating on the main deck (or A deck) with the required spill containment with a capacity of 1 bbl. So, the max hydro pressure that any of the other tanks would experience is the hydro head from the main deck (or maybe the A deck).
Any overflow from the DB hydrocarbon tanks will first overflow to the overflow tank. Overflow tank level alarm is generally set at 10% and HH at 25%. No mention of the levels in this tank in the report. Really strange in that the diesel went up the vent line all the way to the D deck. So, is this 12” vent line from the overflow tank blocked (not likely) or valved in an unauthorized mod (also not likely). Possible there is a spade blank on a flange close to the overflow tank (upstream of the tie-ins from the other tanks) – possibly inserted for tank testing or left over from the yard.
Semantics
In spite of English being the ‘unofficial’ medium of communication, some terms are unique to US. In this case ‘Check valve’. This is called a non-return valve rest of world. This term is understood in the US – but I think ‘check valve’ is not well understood in most places. Maybe the reason for the error in the order for the spare valve. Not intercepted by the technical staff and straight to procurement.
Another one – although no bearing on this incident. Cast iron. Valve ordered is cast iron. The valve standard referred to and in the rest of the world it actually means ductile cast iron. In the US cast iron is exactly what is says – not allowed on vessels for valves. (had an incident with a CI butterfly skin valve installed in the pump room – spec was from American water works (AWWS) - almost flooded the space.
CO2 total flooding – as info.
Fire fighters requesting CO2 discharge comes from NFPA. Thought process is fires could be ‘deep seated’ such as electrical switchboard fires and flooding/blanketing the space with CO2 for an extended period is from NFPA. Also the rate of discharge and required concentrations of CO2 in NFPA is different than the IMO requirements.
7x11 window
Pure conjecture. I think the crew might have placed some rags to absorb any moisture/water coming down from the goose neck and running down to the fuel tanks.
