A fully loaded bulk carrier was downbound on the Mississippi River, outbound for sea. During the transit, she suffered a steering gear failure that resulted in her collision/allision with a moored oil tanker, pier, and tank barge at Louisiana. The damage to all vessels and the oil terminal came close to $17.5 million, as per the NTSB reports. It did not stop there. There was an environmental damage where about 1,200 gallons of oil spilled onto vessel decks and into the river.
Extent of Actual Damage:
Damage amounts were reported as $16 million for the terminal, more than $500,000 each for the Bulk Carrier and the other ship involved in the collision, and about $418,000 for the fuel barge.
The vessel was delivered at Guangdong, China a year before the accident happened. It was noted that the vessel had been experiencing repeated steering gear alarm for filters getting clogged. Since the vessel was a new delivery, the filters were cleaned repeatedly suspecting oil contamination. It was reported that the filter clogging alarm sounded at least 48 times a month. Finally, it was decided to upgrade to a larger filter, assuming that the filter size is too small and little was done to identify the root cause.
As the first step in Investigation, the lube oil samples from the steering gear system was tested. The analysis revealed that the oil was at a “CRITICAL” level with high Iron, Sand and dust/dirt. Further investigation revealed that routine lubricant testing was not adhered to as per maker’s instructions.
This case is a perfect example of Domino’s theory leading to a complete failure. The defenses were not in place and the safety system was not working.
The below defenses, if had worked properly – could have saved such accidents:
- Proper Sampling of lubricants and testing at a reputed lab (Viswa Lab) – a must do action in situations of this sort.
- Failure to address a larger issue i.e, root cause of the filters frequently getting clogged was not looked at.
- The symptoms of the cause was addressed by increasing the filter size whereas the root cause for the filter clogging got overlooked.
Why did the steering gear fail?
The actual reason for the steering gear failure was that a hydraulic valve clogged with debris, preventing it from normal actuation.
Was the Steering Gear tested before Departure Port?
Before the bulk carrier left the berth, the pilot requested that the steering system be tested by moving the rudder between hard (about 35 degrees) port and hard starboard. The full rudder movement took about 13 seconds, and the pilot was satisfied with the rudder’s responsiveness.
During the Incident:
About 2212, when the Bulk Carrier was near mile marker 98 with the city of New Orleans on the left descending bank of the river, the pilot ordered a 2-degree heading change to starboard (from a course of 058 degrees to 060 degrees). To effect this change, the helmsman applied 15 degrees of starboard rudder, and the rudder responded correctly. However, when the helmsman turned the wheel to port to ease the rudder input, the rudder did not respond, which the pilot saw on the rudder angle indicator (an instrument on the bridge panel). The pilot immediately noticed that the ship’s heading continued to swing to starboard, and he asked the helmsman, “Where are you going, man?” The pilot then ordered 20 degrees to port to correct the heading. The helmsman turned the wheel accordingly, but again the rudder did not respond. The pilot promptly told the bridge team, “We’ve got a steering problem. Stop the engine, switch your steering pumps, and stand by the anchor.” He also notified the US Coast Guard’s vessel traffic service about the ship’s loss of steering.
The pilot ordered the main engine full astern and then emergency full astern, to which the chief engineer responded by performing several astern starts of the engine. Doing so made the engine act as a brake, using the propeller to slow the forward movement of the vessel. The pilot then ordered the crew to drop the portside anchor and hold the brake on the anchor. (Holding the brake on the anchor prevents the chain from “running” after the dropped anchor has hit bottom, and thus increases the likelihood of arresting the ship’s forward movement.) At this time, the vessel’s speed was about 8.8 knots and the heading was about 092 degrees, more than 30 degrees to the right of the intended course of 060. The pilot repeated his command to hold the brake on the anchor.
The Bulk Carrier continued turning to starboard until the ship was nearly sideways in the river and almost perpendicular to its intended course. As a result of the astern engine starting and dropping the portside anchor, the bulk carrier’s speed was reduced to about 2 knots; however, these efforts could not stop the ship in time. At 2215, the bow of the bulk carrier struck the starboard quarter of the other tanker. The bulk carrier then allided with the floating pier before coming to a stop,and the floating pier subsequently made contact with the fuel barge. The 1.5-knot downriver current, which was pushing on the bulk carrier’s starboard side, began turning the bulk carrier in the waterway. The pilot ordered the starboard anchor dropped to counteract the effect of the current, and three nearby tugboats assisted with holding the ship.
Engineering Details:
Steering Type: Rotary Vane
Trouble: Solenoid operated Hydraulic Valve
Steering Gear Maker’s Service Letter:
It has become apparent that solenoids installed on some of our steering gears may fail prematurely which can impact the steering gear’s performance. In order to resolve the reliability issue, Rolls-Royce will modify the hydraulic isolation drive circuit for Rolls-Royce frequency controlled steering gears with 230V AC solenoid coils, type: EatonVickers 230V.
Oil Analysis and Investigation:
This oil, which should be clear and light yellow in color, was dark yellow and turbid with visible debris. Microscopic examination showed ferrous particles, oxides, sand, and silt. The results from the portside filter were also “critical,” with very high levels of ferrous particles, sand, plastic particles, and dust.
The oil analysis from the starboard side revealed clear oil without visual foreign matter; nevertheless, the oil was dark yellow in color and the overall diagnosis was “caution.” The oil from the starboard-side filter was also diagnosed “caution”; it contained ferrous particles, sand, dust, silt and lube degradation products.
It was unclear how the debris entered the steering system oil. The contaminated oil was replaced after the accident.
What Can be Done to Prevent it?
- Regular lubricant analysis at reputed laboratory like Viswa Lab.
- Stringent Safety Management System or ISM compliance – reporting, verification and evaluation.
- Risk Assessment or strict compliance with the Management of Change.
- Adherence to Maker’s service recommendation.
- Giving importance to “critical” machinery should be high on agenda and connecting spare parts should always be a priority.
Note: Clean/New lubricating oils are not clean. It is for this reason, Viswa Lab recommends to test/send a fresh/new oil sample along with used oil sample for analysis. By this, fresh oil sample contamination or quality can be verified.
“We test Fresh/New oil samples at no extra cost when sent along with used oil samples. The tested fresh oil results would form a base-line for comparing the test results of an used oil sample. By this, we arrive at an actual trend analysis than mere testing an oil” says Mr. Ganesh, CIO, Viswa Lab.
Disclaimer: This article is based from the NTSB reports published and the intention is to create awareness about the hydraulic oil sample testing and possible failures. The actual report is attached with this write-up for reference.
Source/Full Report: National Transportation Safety Board
