長賜輪在蘇伊士運河擱淺後,綜合外電報導的省思:極限邊緣的船舶操縱,科學與安全之間給”人的反應”留下多少”餘裕空間?
航行員都知道:在有限水域中的船舶操縱與大洋中的船舶操縱有極大的差別,也因此而產生一些”異常反應”的專有名詞,譬如:淺水效應,岸吸/岸推,船體下坐(Squat),狗頭嗅地(Dog smelling),單俥右旋船在淺水區倒俥時之船頭可能向左,主要的原因都是來自船舶四周的海水,來不及湧入去填補船艉所造成之空穴.
也因為這個緣故,Suez Canal當局對過河船隻有一些船寬,吃水,速度上的限制.基於經濟上的考慮,可以想像這些限制都是在”水工模型”下最大化的尺度界線.(越大的船過河費越貴),然而這些都是理想環境下的科學論證,實際上船舶操縱者的精神狀態,駕駛台的氣氛環境,外界視線,無線電之干擾,Marlboro菸未如預期,住艙走廊上”波斯市場”的氛圍….都在影響著”駕駛台資源管理(BRM)”,而使得船舶之實際Performance遊走在”紅線”邊緣,更糟的是一但越過紅線(Point of non-return),情況就越來越糟,猶如在山脊上騎腳踏車.
這次的重大意外,在檢討”船舶因素”之外,蘇伊士運河當局也應該重新考慮”紅線邊緣的緩衝區”是否應適度放寬,以因應船舶無止境的大型化,因應極端氣候下的異常天氣,因應新世代船員之特性,另外也可考慮在駕駛台放一箱Marlboro,讓有需要的人看自己包包大小量力自取,畢竟比起全球供應鏈上的損失,這都是微不足道的”潤滑油”.不是嗎?
The Suez Canal Authority occasionally brings out updated tables of width and acceptable draft for ships. Currently the permissible limits for suezmax ships are 20.1 m (66 ft) of draught with the beam no wider than 50 m (164.0 ft), or 12.2 m (40 ft) of draught with maximum allowed beam of 77.5 m (254 ft). Due to their design and size, a large number of ports around the world can accommodate suezmax vessels.
17,65 56,96
, a new set is being built for vessels as large as 366 meters in length, 49 meters in beam and 15.2 meters in draft at tropical frvessel.
That would have surpassed the speed limit of about 7.6 knots (8.7 miles an hour) to 8.6 knots that is listed as the maximum speed vessels are “allowed to transit” through the canal, according to the Suez authority’s rules of navigation handbook posted on its website. Captains interviewed for this story said it can pay to increase the speed in the face of a strong wind to maneuver the ship better.
“Speeding up to a certain point is effective,” said Chris Gillard, who was captain of a 300-meter container ship that crossed the Suez monthly for nearly a decade until 2019. “More than that and it becomes counter effective because the bow will get sucked down deep into the water. Then, adding too much power does nothing but exacerbate the problem.”
“You might find yourself positioning the ship in one direction, and you’re actually moving in another direction,” said Kinsey. “There’s a very fine line between having enough speed to maneuver and not having too much speed that the air and hydrodynamics become unstable. Any deviation can get real bad real quick because it’s so tight.”
The accident will be a missed opportunity if the industry doesn’t adapt, he said. “There will be vessels larger than this one that will be going through the Suez,” he said. “The next incident will be worse.”
• The Ever Given's speed was 13.5 knots before it ran aground, The Japan Times reported.
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• Bloomberg reported the Suez Canal speed limit was between 7.6 knots and 8.6 knots.
The Ever Given didn't have a tugboat escort through the canal, according to Bloomberg. The two ships immediately ahead of it reportedly had escorts, although such escorts were not required.
右旋單俥船 在 海洋首都中的航海家 Facebook 的最讚貼文
流體力學的功用,不僅僅是讓學生”傷腦筋”,而是實實在在的”省錢”
省錢,也就是節能減碳,來看看近年來幾種”流行”的船艉設計吧,小小的一些改變,省下的除了白花花的銀子之外,更增加了船舶在進出港時低速運轉中的”操控性”.學術上稱之為”安全”.
(1) 在俥葉後方的舵板上加裝了一個”小型的球形船艏”(Rudder Bulb) ,拉長了俥葉排出流對舵軸間之力臂,可以提高船舶推進效率達5%,使船東可以在短期內收回投入成本,並在船舶的整個使用壽命中為船東源源不斷的帶來收益
(2)在上述”舵球”的後方,增加了左右兩小片”鰭片”(Wake fin),可將舵球之後發散的水流改變為”集中”的水流,直接衝擊在舵板後方的中心上. 減少了螺旋槳後面的旋轉流引起的能量損失,提高了推進效率。 這種鰭狀舵,將燃油消耗量減少了約2%。
(3)針對多數單俥右旋俥葉,在車葉前方加裝了四片靜葉片(固定在船殼尾端) ,通常在左舷安裝三個靜葉片,在右舷安裝一個靜葉片(Pre-Swirl)。三個葉片負責減少滑移損耗,而單個葉片則負責增加尾流分數。 這增加了船體效率,同時最小化了空化效應(艉軸之震動).
這些船艉推進器附近的改進,可以在船舶25年的生命週期中,為船東或租方省下油耗成本,為地球之減碳做出貢獻,對船員來說,有一個相對安靜的工作環境.
右旋單俥船 在 海洋首都中的航海家 Facebook 的最佳貼文
2015年12月,在英國亨伯河河口,一艘巴拿馬籍的汽車船"City of Rotterdam" 與一艘渡輪"Primula Seaway"發生了罕見的"迎艏正遇"碰撞事件.經過兩年的調查,英國 海事調查局MAIB與法院終於在前天宣判,法官 Jeremy Richardson說:
"雖然本案中船長及領港因違反公共利益遭刑事入監之判決,但沒有立刻執行之必要",因此四個月的入監刑期獲緩刑18個月.
"Pilot, Captain Sentenced for ‘Motion Illusion’ Collision"
這Motion Illusion又是什麼? "運動錯覺"?那是什麼東東?
一般人開汽車時,有前方"車廠標誌"作為轉彎或直行時之參考目標;然而當你駕駛大卡車,遊覽車,聯結車時司機座位在最前方,頓時失去"小自客"上的參考目標.這也是為何要另考執照的原因之一.
船舶操縱也是一樣,一般人多習慣於"駕駛台在後方"的"小自客型"船舶,開了數十年小自客的司機,第一次被派去為"遊覽車"代客停車時,會發生什麼事?
我記得第一次被派任做汽車船船長(該輪繞地球一周要過29個窄口)時,在比利時的安特衛普的船閘中,上來一位領港問我:船長等一下出閘口時右轉90度,你認為是進俥轉彎好?還是倒俥(單俥右旋船)右轉好?嚇得我一口咖啡幾乎噴了出來!船一解纜往前出閘時右轉,過橋口,大轉彎去靠碼頭,全部我自己來.也見識到比利時人的威力.
領港的執照,並不像汽車執照分得那麼細,尤其在大港口,人多又大車輪的情況下,要累積"遊覽車","聯結車"的經驗並不是那麼容易. 數十年前有船東提出要求"指定領港",但是一提到要加10%的指定費用時,則雙手急搖No!No!No!港區安全遇到市場經濟時,勝負立見!所以說"安全第一"聽聽就好!
#BridgeForward #MotionIllusion #PCTC