Cargo overflow

Our vessel arrived at the discharge port with a cargo of Methyl Tertiary Butyl Ether (MTBE) with most of the cargo tanks loaded to 98% capacity. The cargo was split in two parcels and was to be discharged separately at same berth, using same manifold connection. On arrival cargo sampling was carried out. During cargo sampling the manual drop valves were opened and pump was started from the cargo control room at slow speed. After completion of sampling, deck crew shut the valves. On board this ship, all manual valves are tied with rope to indicate they are shut. The duty officer was instructed to carry out independent checks of all valves and lines on deck in order to confirm they were correctly set- up for discharge. Discharging commenced from No 7 port and starboard centre tanks with the chief officer and duty officer present in the cargo control room.

 The cargo monitoring system indicated No 7 port centre tank low pressure alarm and the chief officer confirmed with deck crew that the vacuum side of the pressure vacuum (PV) valve for that tank was activated. Following this, another audible alarm sounded and the chief officer assumed it to be the low pressure alarm of No 7 starboard centre tank. However, he failed to check the source of the second audible alarm.
      Shortly afterwards the staff on deck informed the cargo control room that one of the PV valves on the forward group of PV stands was lifting. On hearing this, the chief officer immediately checked the status of pressure in forward cargo tanks. Simultaneously, those on deck informed the control room about an escape of cargo from the PV valve of No 1 stbd tank and immediately activated the emergency trip of the cargo pumps from the manifold position. Contingency procedures as listed in the Shipboard Marine Pollution Emergency Plan (SMPEP) were implemented; using company approved PPE, ship staff collected the minor cargo leakage (about 400 litres) from the deck into anti-pollution drums. The cargo spillage was contained on board the vessel.
      On completion of the clean-up operations, the chief officer and Master investigated the status of all lines and valves on deck. They noted that No 1 stbd tank drop valve was not fully shut, although a rope was tied to the valve wheel, indicating that it was fully shut.
      Observations:

  1 Prior to commencement of discharge operations, ship staff had opened all manifold valves on the cargo line of the MTBE cargo. This led to undue pressurising of cargo lines for all cargo tanks loaded with MTBE cargo and No 1 stbd tank filling up causing escape of cargo onto the deck through the PV Valve.
    2 As No 1 stbd tank was at 98% full and at alarm level, no further alarm was generated in the control room indicating the filling of the tank.
    3 The high pressure alarm from No 1 tank was overlooked by chief officer in the control room, assuming it to be the low pressure alarm from No 7 stbd.
    4 The action of deck team at the manifold was correct; immediately activating the emergency stop.
    5 After re-checking the complete cargo system, discharge operations were resumed with all standard Company and Industry procedures in place.
   Root cause/contributory actions:

 1 Human error: Crew member failed to close the drop valve of No 1 stbd tank correctly after completion of sampling.
    2 Human error: Chief officer failed to correctly identify the source of audible alarm in cargo control room.
    3 Incorrect Tanker Practice: Additional valves were opened up which were not required.
    4 Incorrect Tanker Practice: failure to check physically the status of manual valves on deck.
   Corrective actions taken:

 1 On board in-depth investigations and analysis of incident. Incorrect shipboard cargo operations processes were identified and preventive actions implemented.
    2 Training workshop in basic tanker safety held onboard with the deck staff.
   3 Master has been advised to carry out in-depth tanker operation training using safety DVDs.
   4 Ship staff advised to stop the incorrect practice of using ropes to ‘visually’ verify the status of manual valves on deck. They should always physically verify status (open/close) of manual valves and sight the valve indicators to double check the status.
   5 Initial cargo line and valve set-up should be verified by chief officer independent of previous checks, as per company Chemical Tanker Manual.
  （译文参考：船舶管理部机务培训分析师  傅恒星译）

货物溢出

我轮满载MTBE(甲基叔丁基醚 译者注：MTBE是一种新型的汽油添加剂，被用来提高汽油辛烷值和减少汽车尾气中有害物质的排放。)抵达卸货港，此时多数货舱装载量均达到98%舱容。该载货物分为两票，要求在同一泊位，使用同一套管线及通岸接头分别卸载。抵港后按要求进行取样化验，取样期间，从货控室启动货泵低速运转，手动下舱阀开启。取样结束后，甲板人员关闭相关阀门，甲板上所有手动阀门均用绳索绑扎表明已处于关闭状态。值班驾驶员受命独自到甲板上确认所有的阀门开关状态是否已正确设置，并满足卸货要求。之后大副和值班驾驶员在货控室从左右7中舱开始卸货作业。
  货油监控系统显示，左7中舱低压报警，大副要求甲板值班人员验证并确认左7舱压力真空阀（P/V阀）动作，接着报警声再次响起，大副想当然的认为是右7舱低压报警，没有验证第二个报警具体原因。

  没过多久，甲板值班人员报告货控室，前排透气阀组中一P/V阀动作，听到这个消息大副立即检查前排货舱的压力状态，与此同时，甲板值班通知货控，有货油从右1舱PV阀溢出，并立即从喉管处按下应急停止泵按钮。船舶立即按照防油污应急计划（SMPEP）布署，执行应变程序，借助公司规定的个人防护用品（PPE）保护，船员从甲板收集溢出的少量货油，总计约400升入防污桶内，船舶的溢油被有效控制。

  完成溢油清洁工作后，大副和船长调查甲板上所有管线和阀门状态。他们注意到，虽然右1下舱手轮上系着绳子显示阀门已关闭，其实该阀并未完全关闭。

观察结果：

1.卸货前（取样时），船员已开启过货管线上所有阀门，这使来自货油管舱的所有货油管线充满货油并处于过压状态（译者注：货泵低速运转产生泵压），同样充满货油的右1舱管线内货油从P/V阀溢出；
    2.因为右1舱是98%的舱容，已处于报警状态，所以即使再往舱内注入货油也不会在货控室再次触发报警；
    3.No1舱的高压报警被身处货控室的大副忽视，此报警被大副想当然的认为是右7舱的低压报警；
    4.甲板喉管处值班人员反应迅速，立即按下喉管处的应急停泵按钮；
    5.再次检查所有货油系统后，卸货作业重新安装公司的程序及行业规范进行。

根本原因/后续行动：

1.人为失误：船员在对右1舱取样后未能正确关闭该舱的下舱阀；
    2.人为失误：大副没有正确识别/确认货控室的第二个报警具体原因；
    3. 油轮错误的做法：没要求打开其他阀门；
    4. 油轮错误的做法：没有亲自验证甲板上阀门开关状态（仅凭系绳状态是不够的）。

采取的纠正措施：

1.船上针对事故展开深入调查和分析，识别船上错误的货物操作程序，采取相应的预防措施；
    2.组织船员开展油轮安全研讨会进行学习、培训；
    3.建议船长利用DVD视频教学等形式深入开展油轮操作安全培训；
    4.建议船员不应利用绳索绑扎的方式来判定阀门开关状态，应该采用手动检查结合阀位指针所指位置，双重手段来验证阀门具体状态；
    5.按照公司化学品船操作手册要求，甲板货油管线阀门初始状态应该由大副亲自确认核实。