What are 6351 cylinders?

Aluminum 6351-T6 is an alloy that was previously used for SCUBA and SCBA cylinders. There is a problem specific to that alloy that makes them potentially very dangerous,so most fill station operators will not fill them. This is an old problem, but there are some of these cylinders still around and many divers are unaware of the dangers.

Several companies produced and distributed these, including Walter Kidde, Luxfer, and Cliff Impact.  Many millions of these high-pressure cylinders were produced from this alloy. It was discontinued for these by 1990, due to a metallurgical anomaly which can cause sustained load cracking (SLC) along the neck and shoulder areas.

SLC: an explosive problem

SLC cracks tend to develop slowly over several years, most frequently in tanks that have been stored full of air. SLC has caused the explosive rupture of many of these cylinders and multiple losses of life and limb.

Before the technology to electronically detect this problem was invented, we had one of these cylinders explode in our store during a fill. The force of the explosion tore a hole through the roof and knocked a chunk from the concrete slab floor. Damage to the steel frame of the basketball hoop hanging over our pool is still visible today. It was caused by just a small piece of the cylinder hitting the heavy gauge steel and shredding it apart. Luckily, no one was hurt.

This happened with many of these tanks, both in the US and abroad. In some cases, such as the incident in our store, the explosions caused damage but did not result in injury. In other cases, they caused serious injuries and even death.

The explosive problem occurred often enough to warrant a DOT investigation, which resulted in advisories and warnings but no recall. However, we know the problem has been understated. For example, the explosion at GCD has not been included in the known SLC explosion data reported by Luxfer, though we reported it when it occurred and then again later brought it to their attention that it was not included.

Luxfer, who produced most of these cylinders, switched to a proprietary 6061 alloy and phased out the use of 6351 completely in June 1988. They issued several bulletins regarding the SLC problems and offered replacement incentives for many years in an effort to get these older cylinders out of use.

Eddy Current Testing

Because of this significant issue, a new method of tank inspection, eddy current testing, was developed. You may have heard this referred to as VIP Plus, which is a specific brand name. The visual only method previously employed for tank inspection is no longer sufficient for testing, thanks to the metallurgical anomaly associated with the 6351 alloy. Eddy current machines use electronic waves and can detect cracks that are invisible to the eye.  DOT rules now require electronic eddy testing at the same time as hydrostatic requalification, but manufacturers recommend eddy current more often.

Dive Stores and fill stations are well aware of all this and have been for many years. Both the US DOT and NIOSH released multiple detailed safety advisories. Luxfer addressed the topic in several ways, including a seminar at DEMA, the largest annual diving industry trade show, and this may have been the most attended meeting in DEMA history. The room was packed full to standing-room only, and attendees overflowed into the hallway as well.

Do you have 6351 cylinders? Here’s what to do

Many individual divers, however, were not, and some still are not, aware of this significant problem. If you have aluminum SCUBA cylinders manufactured by Luxfer prior to July 1988, or any Walter Kidde tanks, they are likely 6351 cylinders. There are almost no fill stations who will agree to refill these now. While GCD does not have a store policy against this, we will not force our employees to do so. Due to their advanced age and the well known issue of SLC, we prefer not to fill them. As stated above, we have already had one of these tanks rupture and explode in our store.

In an effort to get these bottles out of use, we will issue a $40 credit toward the purchase of a new tank for each 6351 cylinder trade out.

*Image courtesy Extreme Watersports



The fish, a spectacularly colored grouper, paused and opened its mouth. Finning only slightly to maintain its position just a foot (30 cm) or so above the reef, this brightly colored red and blue-spotted grouper waited patiently for another fish, a cleaner wrasse, to provide its services. Within only a few seconds the cleaner approached and went to work, moving from the tail toward the head along the grouper’s body. The cleaner paused every few seconds to pick at the skin of the grouper.

Like other cleaner species, cleaner wrasses help rid groupers and other host animals of irritating ectoparasites that can be found on the skin of the hosts. In doing so the cleaners gain a meal while the host benefits by getting cleaned.
My dive buddy and I followed the grouper as it slowly moved down the reef. We watched as another fish, the same general size and shape as the cleaner wrasse, appeared. Looking quite confident that additional cleaning services were about to be rendered, the grouper paused and opened its mouth. In the blink of an eye, the fish I thought was a second cleaner wrasse swam up and bit a chunk of skin out of the side of the obviously startled grouper.
Clearly, the attacker was a mimic, a species that does a good enough job of imitating a cleaner species to fool groupers and other fishes into thinking the mimic is the real deal. It’s a risky business to try to fool well-equipped predators, but if well-done, the act of deceit can provide a mimic with a meal. If done badly, no more meals will be necessary. This mimic was a tiger blenny, a fact that, like the grouper, I realized only after the daring blenny had enjoyed its success.
After the dive I excitedly asked my diving buddy what she thought of the scene we had just witnessed, and much to my surprise, her only comment was, “that big fish sure is pretty.” At first I thought she was putting me on, but I soon realized that she had missed both the cleaning and the attack. She had noticed that the grouper had its mouth open rather wide, but she wasn’t sure why. She thought the fish might have been injured.
Observing marine life is like putting puzzle pieces together. When you look at one fish, you see only one piece of the puzzle. Yet when you connect the pieces — say a fish to its habitat and to other creatures within that habitat — you begin to see the inner workings of a marine ecosystem.
But how does one go from fish watcher to underwater naturalist? First, the more you dive, the more you will begin to see various subtleties, and the better observer you will become. You’ll find that your awareness of the underwater world increases with time, the number of dives and the variety of habitats you get to explore and enjoy. Second, it helps to learn about what’s going on under the waves so you are more likely to recognize the happenings that you encounter during your dives.

Find Out Who Lives Where, and Why

When looking for a particular marine animal, it helps to know where to find it. Marine life identification books and regional dive guides are excellent resources for learning what types of animals you’d expect to see in a given area. Water temperature and geographical distribution are key factors in determining which species live where. For example, you aren’t likely to see a blue shark on a tropical reef. Blue sharks tend to inhabit the cooler waters of the open ocean in temperate, not tropical, seas. Conversely, you aren’t likely to see an angelfish in a California kelp forest. Angelfishes require warmer water.
Those examples might sound obvious, but being aware that within the same geographical area there are a variety of habitats, and that different groups of animals typically occur in different marine ecosystems isn’t as readily apparent to beginning divers. Keeping these facts in the forefront of your diving mind can be very helpful when it comes to becoming a better observer of marine life.
After all, it makes sense that fishes and other animals that inhabit the sand possess a different set of adaptations than do animals that inhabit reefs or live in mid-water. But because most of us haven’t had a ton of ocean experience when we first take up diving, it can be helpful to have this type of information pointed out to us.
For example, many sand dwellers have extremely low profiles. With few structures that offer hiding places in the sand biome, it should not be surprising to learn that most animals that live in the sand are excellent burrowers, able to rebury themselves rapidly if they get exposed, able to stabilize the substrate around them so they can remain in one place, or they are masters of camouflage. The behavior of creatures such as sea pens, tube anemones, clams, sea stars, sand dollars, stingrays, angel sharks, razorfishes and flatfishes illustrate these points.
In contrast, most reef inhabitants are better equipped to maneuver in the tight confines of a reef, grip the substrate, or blend into backgrounds of varied patterns and hues. Thin-bodied butterflyfishes, angelfishes, sea fans, crinoids, sculpin and other multicolored striped, spotted and mottled fishes provide classic examples that illustrate these adaptations.
Animals ranging from jellyfishes to sharks, whales, dolphins, manta rays, billfishes and tunas are better equipped to inhabit the open sea. Most fishes that live in the open ocean are designed to be superb cruisers but they lack the maneuverability of many reef fishes, and creatures such as jellyfishes would certainly be injured if they were constantly bumping into hard reefs.
On a tropical reef, the creatures encountered on the reef flat, top of a wall, shallow wall and deep wall are often different. This fact might not be so obvious the first few times you explore tropical reefs. If you are like most divers, it takes a while to get your bearings and know where you are in a reef ecosystem, much less to begin to positively identify and distinguish various species and to recognize behaviors.
In fact, I think it’s fair to say that to new divers, many marine creatures look alike. And just as a lot of marine creatures seem to look alike when you first begin to dive, it is not always immediately that different niches exist. In other words, the various niches in a coral reef kingdom or kelp forest can look the same to divers when we lay eyes on coral reefs and kelp beds for the first time. The good news is that it doesn’t take long to begin to get oriented and to recognize that different species occupy different niches within a larger ecosystem.
If you pay attention, as you gain experience you will quickly realize that the animals that occupy one niche are often different from those that occupy another niche only a few yards away.
For example, in many tropical reef systems you are likely to see schools of tangs and surgeonfishes along the tops of reefs, but you aren’t likely to find them in deeper areas. At the same time you are likely to find creatures such as lobsters, crabs, shrimps and octopods close to areas that are filled with cracks, crevices, ledges and other hiding places.
While there are way too many species to mention, you want to realize that the ocean, and even a single reef area, is not just one generic place. There are many different habitats, and different species tend to occupy the various habitats.
Of course, as soon as I make that point, I must point out that there are plenty of exceptions to that general rule. For example, you might see a school of feeding jacks, eagle rays or a reef shark cruising various niches in a reef system.
Divers that explore temperate seas will find that a variety of habitats exist in kelp forests as well as in the rocky reefs. Close to 800 species inhabit Southern California kelp forests, but different creatures live in the floating canopy near the surface, on the fronds, on and around the holdfasts, in and on the surrounding reef, in mid-water and on the nearby sand flats.
While you might encounter creatures that range in size from inch-long, rainbow-colored nudibranchs to lobsters to giant seabass on a single dive in a California kelp forest, the odds are high that you will find various species in different parts of the forest and surrounding habitats.

Consider Form and Function

The body shape of marine creatures plays a very important role in how and where various species live.
As examples, most torpedo-shaped, or fusiform, animals such as dolphins, barracudas, tunas and open-ocean sharks are built for speed. These creatures live in the water column, not on the sea floor or in the tight quarters of reef communities. Laterally compressed fishes such as triggerfishes, angelfishes and butterflyfishes are built to efficiently slip into and out of the latticework of reef formations, but on the whole they are less capable of generating the speeds attained by more torpedo-shaped animals.
Animals such as rays and angel sharks are flattened from top to bottom. These creatures are well-equipped to maintain low profiles and are typically found along the sea floor in areas where they can go generally unnoticed. These animals often bury themselves in the sand, a great way to go unnoticed by potential predators and prey alike. Armed with this knowledge, you can often discover rays and other sand-dwelling animals by noting the outline of their buried bodies.
Sea snakes and eels have a long, more attenuated shape that is ideal for slinking around in the crevices of reef communities, and that is where you are likely to find them.
By noting and considering the shapes of animals you find in very specific areas, you can begin to acquire valuable insight that will help you put together the marine puzzle. And once you begin to put part of the puzzle together, so many other pieces begin to fall into place, and that is the real payoff in being a good observer. By knowing about behaviors, lifestyle and shape, you begin to anticipate where to find various species. At that point you can pat yourself on the back a time or two, because you will be on your way to becoming a good observer.

Become Aware of Adaptations

To survive, marine animals must adapt — both to their environment and to overcome their limitations. After all, not every species can be the biggest, fiercest, fastest, most superbly camouflaged and most clever. One of the most fascinating aspects of nature and the underwater world is that there seems to be such an endless variety of adaptations that are accomplished in countless ways. Shape, as just discussed, is one of those adaptations. I’d like to point out a few more just for the sake of providing examples, but keep in mind that every animal, or closely related group of animals, possesses some adaptation, or adaptations, that make them unique. Being aware of those adaptations can be the key to enabling you to become a good observer of marine creatures.
Here are some examples. Many brightly colored animals are venomous or repulsive in some way. It’s true of lionfishes, stonefishes and sculpin. These fishes are not among the fastest swimmers. They don’t have to be. Nor are they quick to give ground when approached, because nature has equipped them with other means of defense analogous to the way that snakes and porcupines are created. When on the hunt these animals must be able to strike quickly and overpower their prey. This is equally true for other relatively slow swimmers such as frogfishes and toadfishes.
Using bright color as a warning is not unique to fishes. Many nudibranchs, shell-less mollusks that are closely related to garden slugs, have soft bodies and they are rather slow crawlers. And many species stand out prominently because of their bright colors. These nudibranchs steal the protective stinging cells of corals. Then they place them in the tissue of their own back where those cells serve to repel animals that do not pay heed to the warnings of their bright colors. In this case the colors are intended to say “leave me alone.”
In the case of other invertebrates, you will want to consider the very basic question of whether an invertebrate is permanently attached to the substrate or whether it is mobile.
If an invertebrate is mobile, can it swim like squid and octopods, does it crawl or does it simply go where wind and current take it as is the general case with jellyfishes? Because jellyfishes are at the mercy of the prevailing conditions, their stings can be quite potent. The same is true of anemones and corals. If an animal cannot pursue its prey, it better get it while the getting is possible.
Consider whether an invertebrate has a shell or hard skin. If it has a shell, what does it do when it needs to grow? Does it swap shells, as is the case with hermit crabs, or molt, as is the case with lobsters, crabs and shrimps? Some shelled animals such as snails keep their shells for life, so they need to maintain it. That is the job of their colorful organs known as mantles. Shell-swapping crabs often attach other organisms to their shells so that a host animal is less obvious.
By considering these adaptations and the challenges that each animal faces, you will gain much better insight into how different species live, who eats whom and when, where and how to find various creatures.

Hone Your Fish-watching Skills

Next time you dive, instead of simply looking at a fish, challenge yourself a little by trying to put the fish in context with its surroundings. Consider its shape and other adaptations it possesses as well as what you know about its lifestyle. See if you can determine whether the animal appears to inhabit a relatively small territory or whether it is in transit. If the fish tends to stay close to one area or repeatedly swims over the same patch of reef, look for a nest site or mate. You won’t always find them because they are not always present, but in many instances by applying a little common sense you will discover a nest, mate or perhaps a food source.
As examples, with the damselfish known as the sergeant majors that occur in tropical seas and California’s state marine fish, the garibaldi, you will often discover a male that is manicuring or protecting a nest, or trying to woo a female. It’s great fun to watch a protective damselfish attempt to ward off other egg-stealing fishes and invertebrates such as sea stars, snails and sea urchins.
If a fish is a member of a school, try to determine if the fish in the school are feeding. If they are, ask yourself if they are feeding in mid-water or along the sea floor. If they are feeding on the sea floor, as is often the case with tangs and surgeonfishes, look to see if any smaller fishes such as territorial damselfishes are trying to push them out of their territory. On the whole, damselfishes are relatively small, but they seem to have no idea that this is true. They will defend their realm against almost all intruders.
Schooling is a good way for fishes to gain access to a mate, and often in schools of hundreds, or even thousands, of jacks you will see male and female pairs, or you will see spawning activity. Next time you see a school of fish, look to see if perhaps they are feeding or if you can locate a male/female pair.
One of my favorite ways of getting oriented in any tropical reef I have not dived is to look for cleaning stations. Cleaning of some kind can be found on the majority of reef dives, and the cleaning stations are often a great place to find interesting activity that centers on fishes and some other animals. Cleaning stations are often found around prominent outcroppings such as a big coral head or sponge that is on a point. If you find cleaning activity in a given place on one dive, you will often see cleaning there again on subsequent dives.
Of course, you can conduct a similar exercise with any group of animals, but fishes are present almost every time you make a dive, and if you are a good observer, watching them closely will help you learn a great deal about the animal you are watching and about life in the sea.
Learning to be a good observer of marine life is more of an art form than an exact science. Everyone brings a different background to their diving experiences and as a group, we learn to dive in a lot of different places. After learning we travel to different places and experience different phenomena.
When you are new to diving and when diving in an area that is new to you, my suggestion is to first learn about the bigger ecosystem. Getting a grip on the big picture provides you with a frame of reference so you “have a place to put” the smaller pieces of the puzzle. By understanding the big picture you can begin to understand where, when and why you are likely to find the creatures that live in a particular ecosystem. And once you start to understand that information, it will be far easier to understand and anticipate their behaviors.

You’re Watching Them, They’re Watching You

In almost every encounter with fishes, turtles and other big creatures, it has served me well to do whatever I can to make myself appear nonthreatening and unobtrusive. For example, when I first encounter a turtle, instead of trying to get as close as I can as fast as I can, I often avoid eye contact and try to appear interested in something else. In this way I think I appear to be nonthreatening and my behavior often seems to encourage the turtle to acclimate to my presence instead of speeding off into the distance.
When observing marine life, move slowly and be patient.  Avoid chasing subjects and barging into territories like the proverbial bull in a china cabinet.  As a rule, animals will flee or hide, and even if you get close to the animal, you often fail to get the most out of the opportunity, because you have disrupted the animal’s natural behaviors.

from Dive Training Magazine



What is mask squeeze?

Like the air spaces in your sinuses and ears, you must also equalize the air space in your mask as you descend. When you descend, failure to equalize, or add air to the air space in the mask, by exhaling through your nose can create unequal pressure between the mask air space and the vascular pressure within the blood vessels of the face. This can result in various degrees of facial barotrauma, or injury to the soft tissues of your face contained within the mask. Imagine your face in a suction cup. The soft tissues beneath the mask and especially around the eye swell (periorbital edema) and discolor, such as redness or bruising (ecchymosis).

What treatment do I need?

Unless you are experiencing eye pain or visual problems, there is no treatment for facial barotrauma except time. Because it is a bruise, your body will eventually reabsorb the effect of your mask squeeze. Your physician or an eye specialist should address eye pain or visual disturbances such as blurred vision or loss of part of the visual field immediately. These symptoms would be extremely rare in mask squeeze, however. The signs and symptoms of mask squeeze can take up to two weeks or more to resolve. Unfortunately, it is one of those conditions where you will probably look worse than you’d like before it gets better. Not only will blood and edema need to be reabsorbed, but it tends to be gravity-dependent – which means it will spread downward on your face. Before you heal, you may look like a red-eyed black-and-blue marked creature in a B-grade horror flick or a boxer that took at least two too many punches.

Who gets mask squeeze?

Mostly new divers get squeezed – they tend to be overwhelmed by all the skills they need to remember, such as buoyancy control and equalizing their ears and sinuses, all while being mesmerized by the mysteries of the sea. More experienced divers, however, are not immune to mask squeeze. They tend to have mask squeeze when they are concentrating on some new activity or focused in on a task which diverts their attention from clearing their mask. Changing to a new mask or to a low-volume mask may also lead to mask squeeze, because the diver may not be accustomed to when to add air. Finally, poor-fitting masks or other issues such as facial hair may lead to problems with equalizing.

How do you prevent mask squeeze from happening again?

The solution to preventing mask squeeze is to remember to keep your nasal passageways open during descent. By exhaling through your nose and using a properly fitted mask, you will minimize the risk of facial barotrauma. A mask should fit comfortably against your face and you should be able to achieve an appropriate seal by gently placing the mask on your face and inhaling through your nose. The mask should seal to your face and not fall off even without the mask strap in place. It is not unusual for a small amount of leakage to occur while diving, especially if you have facial hair. Exhaling through your nose and tilting your face towards the surface while cracking the lower seal of the mask will generally remove any unwanted water from your mask.

reprinted from www.diversalertnetwork.org



You know, when I was asked to write a short bit about divers staying hydrated, I said, sure I’d be glad to. Should be pretty straightforward, given that we, from the time we first took a dive course, are reminded to stay hydrated as a preventive measure, not the least of which is to not contribute to DCS. Then I dug out a few textbooks from my days as a firefighter/EMT. My next immediate thought was “how do I keep this under a page or two?”

Let’s set aside for the moment the fact that we are divers, and being hydrated is important. First, let’s look at some very basic facts that will help to understand the how and why we need to stay hydrated and what comprises Dehydration. Simply put, dehydration is a condition in which we lose body fluid, mostly water, and that loss exceeds the amount of water we take in.

How do we lose water? Merely by living, we lose water through exhalation, urinating and sweating. Then add to this exercise or activity (diving), and we lose even more. Should we be ill with fever or diarrhea (as in “don’t drink the water”), the deficit grows substantially. How can we recognize dehydration? Some of the signs and symptoms of mild dehydration include, obviously, being thirsty (more on this in a bit), perhaps feeling tired and darker yellow tinted urine would be an indicator as well. It’s estimated that these signs and symptoms occur with only around a 1-1 ½ % loss. That isn’t much. While it really is outside the scope of our discussion here, losses that approach 4-5% become very serious and require immediate attention.

One of the negative aspects of being dehydrated, especially as divers, is that it can be a contributing factor to decompression sickness. When we consider that traveling divers spend time on airplanes, which is an extremely dry environment and the possibility of increased alcohol intake, which leads to dehydration, it doesn’t take too much thought to realize that one must increase the fluid intake to compensate for fluid loss. Keep in mind that improper fluids, such as alcoholic beverages, do not hydrate the body very well. It has been often said in the past that coffee and tea….or caffeinated beverages were considered diuretics and contributed to fluid loss. The debate is still ongoing in regards to this.

Signs and symptoms of mild dehydration include:

  • Dry mouth
  • Sleepy or tired during daytime
  • Decreased urination

And of course, being thirsty. If you find yourself at this point, being extremely thirsty, you’ve waited too long for that drink of water.

How do we become dehydrated? In addition to not drinking enough water, other contributing factors include increased activity, climate change, such as traveling to warm water diving locations, increased alcohol intake and illness such as vomiting or diarrhea, perhaps from food or water while traveling.

So, how do we hydrate? Well, yeah… drink some water. How much? As mentioned previously, if you’re extremely thirsty, you’ve waited too long to rehydrate. The best water intake is gradual over time, sustaining a nice balance with an increase of water intake with increased activity (diving). We’ve often heard of the “8 by 8” rule which suggests the average adult drink 8 eight ounce glasses of water per day, for a total of 64 ounces of water intake. Recently however, the Mayo Clinic is advocating an intake of 3 liters/101 ounces for men and 2.2 liters/74 ounces for women. Environment, as well as activity, will also impact how much water you should be drinking.

Another source of fluids can be so-called sports drinks, keeping in mind that we should take notice of the nutritional information label to avoid excessive sugar and sodium. In addition to liquids, we also derive hydration from the foods we eat. Fruits and vegetables can contribute up to 35% of daily fluid intake.

Staying hydrated as we enjoy diving is easy, makes sense and will contribute to having a great experience. In fact, why not throw your drinking bottle in your gear bag and make it part of your equipment check list as you prepare for the next dive or dive trip?

reprinted from  www.tdisdi.com from January 7th, 2013



All are invited to join the Gulf Coast Diving Society for dinner at Ed’s Seafood Shack, 3382 Battleship Parkway, Spanish Fort on Monday, October 3rd, 2011 @ 6:30 pm. Monday nights are all-you can-eat mullet so come and enjoy. This is a great way to meet new dive buddies, reaquaint with old buddies, introduce someone to the social aspect of being a diver on the beautiful gulf coast. Get the latest news on local trips, international excursions, new equipment or just hang out. Bring your laptop and share some of your pics and videos. This event is FREE, just pay for whatever you eat and drink. Most folks will be bringing the whole family and ordering dinner. For more info. call (251) 342-2970. Please rsvp to the same number, we need to let the restaurant know how many hungry divers to expect.



All are invited to join the Gulf Coast Diving Society for dinner at The Mariner Restaurant on Dog River, 6036 Rock Point Road, on thursday, April 28, 2011 @ 6:30 pm. This is a great way to meet new dive buddies, reaquaint with old buddies, introduce someone to the social aspect of being a diver on the beautiful gulf coast. Get the latest news on local trips, international excursions, new equipment or just hang out. Bring your laptop and share some of your pics and videos. This event is FREE, just pay for whatever you eat and drink. Most folks will be bringing the whole family and ordering dinner. For more info. call (251) 342-2970. Please rsvp to the same number, we need to let the restaurant know how many hungry divers to expect.