Steering Gear : Curing the Root Cause, Not Just the Symptoms….

 

Flag Gangos Collision

On August 12, 2014, the bulk carrier Flag Gangos was downbound on the Mississippi River, outbound for sea with a full load of grain and corn.  During the outbound transit she suffered a steering gear casualty that resulted in her collision/allision with a moored oil tanker, pier and tank barge at IMTT Gretna, Louisiana.  Total damages to all vessels and the oil terminal totaled close to $17.5 million.

Why did this happen?

The short answer was that a hydraulic valve became clogged with debris, preventing it from actuating normally.  The long answer starts almost a year prior, shortly after the vessel was launched in Guangdong, China.  For the first seven months of operation, the “clogged steering system filters” alarm sounded up to 48 times per month.  While the filters were repeatedly checked, cleaned and ultimately upgraded to a larger size in June 2014, little else was done to identify a root cause.

During post-accident investigation, samples of the hydraulic fluid were taken from both the port and starboard steering hydraulic systems.  The analysis of these samples indicated that the oil was at a “critical” level with very high levels of ferrous particles, sand, plastic particles, and dust.

Ultimately, the U.S. National Transportation Safety Board identified two root causes.  The first was a delay in upgrading a steering gear component previously identified by the manufacturer as requiring replacement.  The second was the failure to routinely test the steering gear hydraulic fluid.

As mariners, whether on the deck or engine side of the house, we need to be cognizant of best practices in the industry. If there is a standard procedure, such as sampling lubrication or the determination of a root cause when an alarm or incident occurs, we must ensure the proper procedures are followed. Not delving down to the root cause of why the filters were clogging or indicating clogged on Flag Gangos allowed an unsafe condition to persist. Curing the symptom (much like a medical doctor) does not necessarily cure the real issue.

How could the root cause of these alarms have been determined?

While there are numerous systems out there for determining the root cause(s) of incidents, one of the simplest is the 5-Why method.  To boil it down to the very basics, identify the incident (i.e. alarm sounds for clogged filters) and ask “Why?”  Repeat this process with the answer (or answers) you have generated and by the 5th “Why,” you should have your root cause.

In the case of Flag Gangos, the answer might be because the filter became clogged.  The next step would be to ask, “Why did the filters become clogged?”  The answer in this case could be that either the filters installed were too small for the job or that the hydraulic fluid was contaminated.

Following this causality chain further, we ask, “Why was the hydraulic fluid contaminated?”  Note, we are now at 3-whys and starting to zero in on the real problem.  The answer might be (and entirely hypothesizing now) that the hydraulic fluid had to be removed at some point for maintenance and was stored in dirty drums before being pumped back into the system.

It can be seen that there are multiple answers possible for each level of why.  At the second level, we had two branches.  The first, that the filters were too small and the second that the hydraulic fluid was contaminated.  For whatever the reason, the first branch – that of filters being too small – was followed, with the result that only a symptom of the root cause was cured.

It is crucial that all possible root causes developed by the 5-Why analysis be investigated.  Simply resolving the simplest and most expedient (and sometimes least expensive) possible root cause is usually the most attractive.  Unfortunately, that leaves the actual root cause hanging out there, ready to strike at the most inopportune time – like when you are passing an oil terminal outbound.

Additional Reading and Links

The Maritime Executive – MSC Ship Aground in St. Lawrence Seaway – January 24, 2016

NTSB – Flag Gangos Collision/Allision – August 2014

Swedish Club Monthly Safety Scenario – February 2014 – Steering Gear Failure

Safe Transit Program : A Guide for Preventing Engine and Steering Failures

Marine Insight : 8 Common Problems Found In Steering Gear Systems of Ships

Marine Insight : Procedure of Testing Steering Gears on Ships

Understanding How to Use The 5-Whys for Root Cause Analysis

Advertisements

One thought on “Steering Gear : Curing the Root Cause, Not Just the Symptoms….

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s