What are the dangers of shipping LNG?
The ships can be as large as 1,000 feet long and carry 33 million gallons of liquefied natural gas.
But, according to a renowned expert regarding LNG tankers and safety, these are some of the newest
and safest ships on the water today.
Michael Hightower, of Sandia Laboratories Energy Systems and Analysis Department, has written
reports for the federal government regarding the safety of LNG shipping and he has several conclusions.
He says, based on Sandia’s database, there have been virtually no spills from an LNG tanker. He added
there absolutely have been no major spills.
“There have been some LNG handling spills, but as far as a ship hitting another ship and having a spill,
there has not been one since the 1970s,” he said in a recent phone interview. “Their safety record is
impeccable, extremely good. It is the best of any of the large transportation and shipping materials.”
Susan Sakmar, another LNG expert who has researched the industry for her book “Energy for the 21st
Century” said there’s not quite enough data to study when it comes to LNG plants and its shipping.
“But, there aren’t a body of accidents to study,” she said. “So, that tells you something.”
A longtime maritime pilot who spent years on tugboats in Corpus Christi, Houston and as a support pilot
for the Port of Brownsville, agrees with Hightower’s assessment of the ships.
“The vessels that will move this haven’t even been built yet,” said Mike Kershaw of Corpus Christi.
“These ships are the finest in the world. The pilot standards for the movement of these vessels is some
of the most critical I have ever seen.”
LNG is shipped commercially in a fully refrigerated liquid state. The fundamental difference between
LNG carriers and other tankers is the cargo containment and handling system. The combination of the
metallic-tank containment and insulation needed to store LNG is called a “containment system.”
Current LNG vessels can cost approximately $160 million, according to PetroWiki.
However, while the risks seem minimal due to the double-hulled nature of the ships, Hightower
understands what those in the area want to know regarding the movement of these tankers and the
cryogenic liquid inside them.
“The public wants to know what is the likelihood, what is the most common distance,” he said. “If they
are 10 miles away, are they at risk? That is what the public wants to know. What is the average hazard
and the other thing we find is how will emergency responders handle this?”
He answered those questions in depth, including the possible impact to close-by Isla Blanca Park, Port
Isabel and Long Island Village as the tankers make their way through the jetties, Brazos Santiago Pass
and into the 17-mile long Port of Brownsville ship channel.
The LNG vessels, like others going into and out of the Port of Brownsville, will have to navigate the
jetties and through the basin to the ship channel. During that process, the ship will move past people
fishing and swimming in Isla Blanca Park and the other nearby beaches as well as marinas filled with
boats of all sizes.
Hightower talked about the most significant worry — an LNG spill that ignites into a fire on the water.
With that comes what Hightower calls hazard distances.
“If bringing a ship into an area that is more than a mile away, you are pretty safe,” he said. “Half mile to
a mile, there needs to be some provisions.”
Hightower said a spill with a small fire could be a scenario impacting public safety.
A spill, big or small, could disperse as a vapor cloud and then move in a direction depending on the wind.
If there is an ignition source, it could burn.
A hazard distance in that case may be as much as 2 to 2.5 miles from the ship. It may be less if it hits an
ignition source and burns off.
“We have told people if there was a spill in the channel, you are likely to get a fire,” he said. “Consider
the fire hazard half a mile to a mile.”
The vapor from the LNG turning to gas when reaching the warmer water could create the longer hazard
distance. With the wind direction variable on a given day or time of day, the cloud could go anywhere.
Hightower said the safety issues to public open areas aren’t as critical as they are to higher populated
areas.
“State parks and parklands are important, but generally by the time a fire starts and people see it, they
decide to move away and drive off,” he said. “What the bigger issues is when you have populated areas,
they can’t go anywhere quickly. That is where you find the most interest in risk management —
populated areas. People can’t move. You have elderly people and young people.”
The U.S. Coast Guard assesses these hazards and determines critical areas and waterway suitability,
Hightower said.
Speed limit is one way to minimize the severity of an accident.
“There are a lot of things the Coast Guard can draw on to reduce the likelihood of a breach and thus the
hazard distances to the public,” Hightower said. “It changes depending on the waterway, what
industries, community center and residential areas.”
But, it’s still best to be as far away from populated areas as possible, like the Cheniere facility in Sabine
Pass, Louisiana.
“That, from my standpoint, is good. It is not impacting people,” he said about that remote LNG plant
location. “Selecting locations of transits that impact people the least. If you can’t get far enough away,
then you can do the management and mitigation to try to reduce the likelihood and severity of the spill.
Make sure in case it does happen, the fewest number of people are impacted.”
Ship accidents or incidents aren’t the only concerns.
Accidents while LNG is being transferred to the ship at the site of LNG storage tanks and liquefaction
process is where Hightower has seen some of the biggest spills. That still happens in small amounts.
Hightower said, maybe 4,000 to 5,000 gallons.
It takes about 15 hours to fill an LNG ship.
“They transfer the liquid very fast and using multiple hoses,” he said. “So, if you do get something that
causes the hose to break or the ship moves, there is an emergency shut down device. But, you can have
gallons spill out.”
If there is no ignition source, the LNG will evaporate and disperse. In some cases, if there is a spark,
there can be a short duration fire about 10 to 20 feet in diameter.
“LNG hazards are different than crude oil, propane, etc., and they burn differently,” he said. “LNG has to
be looked at separately. Most of the shipping has risk management on it. LNG is just another one that is
hazardous.”
https://www.themonitor.com/news/local/what-are- the-dangers- of-shipping- lng/article_9197301a-3c18-
