OBJECTIVES:
 1.  Students will be able to explain the proper care and maintenance of personal gear, buoyancy compensator, regulator (and gauges), wet suits and tanks.
 2.  Students will be able to list which items of equipment need special consideration for Enriched Air Nitrox Diving.
 3.  Students will be able to explain the general care, maintenance and operations of scuba air compressors.

 List six pieces of equipment (other than BC, regulator, and tank) that are either needed or are personal items that might be used during a dive.  Explain how each of these items are cared for and maintained after each dive.

 Many divers don’t think about maintaining personal items such as mask, fins, snorkel, dive knives, dive lights, underwater camera and wet suits; however with proper care and maintenance these items will last for years to come. To start with lets look at the proper care and maintenance of  mask, fins and snorkels (MFS).  These items don’t typically need to be serviced, but they do need to be cleaned properly after each dive.  As with most dive gear MFS need to be rinsed thoroughly in fresh water, before allowing to dry in a cool place out of direct sunlight.  Freshwater rinses are important no matter what type of environment you have dove in, as different environments pose different types of problems for personal gear.  Gear not rinsed after diving in salt water will leave salt deposits on MFS and may make them uncomfortable to wear.  Fresh water (lake or river water) usually has a high concentration of algae and bacteria and if not rinsed properly these microbes will propagate and begin growing in the nooks and crannies of your MFS.  Chlorinated water will kill the microbes present in fresh water, but it speeds up the dry rotting process associated with silicone products.  After rinsing and thoroughly drying MFS, you should store them in a cool, dark location in a container or area that will not deform or otherwise misshape the silicone.  This is particularly important for the silicone skirt around the mask.  Even the slightest deformation could cause the mask not to seal properly, rendering it utterly useless.
 Dive knives should be rinsed and dry in the same fashion as MFS.  Any rust that appears can be quickly removed with steel wool or some other buffing pad.  Knives should be coated with a silicone produce (grease or spray) or other rust inhibitor prior to each dive to prevent premature rusting.  Knives should also be sharpened periodically and locking devices should be checked prior to each dive to make sure that the knife is secure within its sheath.
 Dive lights and underwater cameras bring with them an additional problem—o-rings.  Besides rinsing, drying and storing as directed with MFS.  O-rings need to be removed, checked and cleaned after each dive.  To accomplish this begin by removing the o-ring from either the light or camera.  Check the o-ring groove and clean it of all grime and debris (never use silicone sprays that use propane as the propellant on plastic housings).  Clean and lube the o-ring using a minimal amount of silicone grease, just to moisten the o-ring.  Place the o-ring into a plastic bag until it is needed again on the next dive.  Storing the o-ring out of the housing will prevent it from deforming under pressure and will prolong its life.  Batteries should also be removed and store in a plastic bag until needed again to prolong their lives.  If it will be a long period of time between dives, such as the last dive of the season, you should mark or diagram the o-rings and light/camera, so as not to forget where each one goes the next time you used them.
 The proper care and maintenance of wet suits should be no different than with other personal gear with the exception that it is imperative that wet suits be thoroughly dried before they are stored.   Anyone who has dove for any length of time can attest to the smelly stench of a wet suit that has not been properly cleaned, dried and stored.  If a smell does exist, the wet suit should be thoroughly scrubbed and cleaned in soap and water.  Commercial cleaner are also available, but be aware of cleaner that only mask the smell and don’t claim to remove it completely

1.  What is the proper order and care of all personal gear?  What extra steps must be taken for dive lights and cameras?
2.  What are the major operating components of your buoyancy compensator (BC)?

 Aside from rinsing, drying and storing your BC in a cool dark place, there are a couple of additional steps that should be taken.  First, the inside of your BC should be rinsed with fresh water.  This is accomplished by depressing the deflation button on the inflator hose while filling the BC with running water (preferably from a hose) through the deflation (or oral inflation) port.  Let the water run inside the BC for 1-2 minutes.  Then, slosh the water around in the BC, dumping it out by turning the BC up-side-down, making the low pressure inflator hose end the lowest point on the BC.  Press the deflation button and allow the water to run out of the BC.  Shaking the BC maybe necessary to get all of the water out.  While dumping the water from the BC, push the power inflator button several times.  This allows fresh water to run through the power inflator mechanism, washing it out as well. Rinsing the inside of the BC keeps microbes like algae and fungus from growing inside the BC. 
 Secondly, buoyancy compensators should be serviced regularly in order to assure that the inflation/deflation mechanism and dump valves are operating properly.  Additionally, the inflator hose and internal dump cord should be checked for cracks and signs of over-use.  To check the internal dump cord, cut the zip ties from the hose at the inflator (or free) end of the inflator hose.  Pull the inflator mechanism from the hose and inspect the general condition of the dump cord (replace the cord if necessary).  Reinstall the inflator mechanism and secure it using two new zip ties.  Make sure the position of the oral inflation port is correct for oral use.  

3. Why is it important to wash out the inside of the BC?
4.  Thinking back to basic scuba class and your own experience, explain what type of maintenance is needed for scuba tanks and why.

 Most divers don’t think that scuba cylinders need much in the way of care or maintenance (other than the normal annual inspection), but tanks are much more complicated than just being a container to hold air.  In 2001 eleven cylinders exploded injuring several people.  Over the last several years more than 20 cylinders have exploded due to improper care and maintenance.  “Proper” annual visual inspections can decrease the incidence of explosion by identifying potential tank hazards before they become a problem.  Proper visual inspection consists of several steps.  A general overview is outlined here.  First, a thorough exterior inspection of the cylinder should be completed.  This inspection should identify gouges, bulges, dents, and other general flaws in the exterior of the tank.  From there inspection proceeds inside.  The visual inspection of the inside of a cylinder looks for corrosion, cracks, pits, and other general imperfections in the alloy material.  If the tank is determined to be too badly corroded or pitted, then the tank may need tumbling.  Tumbling removes any internal corrosion by grinding away a thin layer of the interior surface.  The third step in a visual inspection is to examine the neck (on the inside) of the cylinder.  This is a complicated process that requires a mirror and light to accomplish.  The neck of the cylinder is one of the most critical areas of the tank because it is hard to see and because it is an area of stress.  Next, the visual inspection moves to the thread area, where threads are examined for imperfections and having the required number of threads for a particular pressure rating.  The threads and o-ring seat are also critical areas and must be examined thoroughly.  Some older tanks have developed “Sustained Load Cracks” (SLC) in them from being left filled over long periods of time.  Additionally, the aluminum alloy that Luxfer used from 1977 until 1987 has contributed to SLC.  Check with your local dive facility for specific tank serial numbers and series.  After a thorough visual inspection, scuba cylinders can be safely used for 12 months under normal operating conditions.
 Every five years (or if a cylinder has been tumbled) scuba cylinders need to be hydrostatically tested.  This test tests the structural integrity of the metal.  Because tanks are filled with high pressure air, metal fatigue can happen over several years.  The Department of Transportation, which regulates the transportation of high pressure cylinders, has determined that five years is a sufficient frequency for hydro testing.  To hydrostatically test a cylinder, the tank is filled to 5/3 the working pressure of the tank (to 5000 psi in a 3000 psi cylinder).  Before filling, the tank is measured to determine the original size.  When the pressure is released the tank must shrink back to within ten percent of its original size or the tank will be condemned.  Visual inspection follows a hydrostatic test in order to check for unusual changes in the tanks internal condition.

5a.  Explain how often and why scuba cylinders need to be visually and hydrostatically tested.
5b.  What specific cylinders are subject to SLC.
6.  Locate, draw and label a diagram of a common scuba cylinder valve.

 The two most common valves used in the United States are the “K” valve and the “J” valve, although din valve are also found on occasion and typically requires a special adapter to be filled in the U.S.  Din valves are typical to diving in Europe and are designed for high pressure cylinders (regulators with din fittings screw into the din valve found on the tank, making a more secure union than yolk model regulator/valve pairs found in the U.S.).  Because they provide either a second yolk for an additional regulator or allow for double cylinders to be tied together, “Y” valves and manifolds are also used (respectively) in the U.S. for tech diving.   Tank valves are designed with a safety feature called a burst disc.  This disc is designed to burst if the tank pressure reaches 5/3 the working pressure of the cylinder (5000 psi in a 3000 psi cylinder).  Should the burst disc burst, the disc will need to be replaced before the cylinder can be filled.  Generally, no harm can come from the disc bursting, only the annoyance of not being able to use the tank until repaired.
 
7.  What is the design function of each of the four types of tank valves?
8.  What equipment should be modified for nitrox diving? 

 In the past 10 to 15 years enriched air nitrox (EAN or nitrox) has become increasingly popular.  Our previous discussion on tanks and valves brings us to the point where we need to discuss nitrox diving.  Enriched air nitrox is just as the name suggests—enriching the air we typically breathe.  What the name doesn’t tell us is that the air is enriched with oxygen.  For recreational purposes, nitrox usually contains between 22 and 40 percent oxygen (air contains 21 percent oxygen).  This oxygen boost has several benefits, as well as several problem, one of which is important to this discussion (the others can be studied in the Technical Diving portion of the Master Scuba Diver course).  One method of filling scuba cylinders for nitrox diving is called partial pressure mixing.  This is the most common and simplest way to fill nitrox tanks.  The procedure for partial pressure filling is to put a specific amount of pure oxygen into the scuba tank and then top off the tank with air from your compressor.  This boosts the oxygen content in the tank to a specific level.  The problem exists from the beginning.  First, is that oxygen is a very strong oxidizing agent, in other words, it is absolutely necessary for fire.  Second, petroleum products like silicone and compressor oil are flammable.  When these items are mixed, disaster is the only outcome.  Scuba cylinders for nitrox diving must be O2 cleaned to remove all of the petroleum products from the valve and the interior of the tank.  Additionally, all of the silicone o-rings must be replaced with non petroleum Viton o-rings.  This assures that when oxygen is put into the tank during partial pressure mixing (even at low pressures) the likelihood that the tank will explode is greatly decreased.  For this reason divers diving nitrox need to have nitrox dedicated cylinders, even if the nitrox mix is below 40 percent.

8.  Explain why it is important to have a nitrox dedicated cylinder for nitrox diving.
9.  What does Charles’ Law tell us about the relationship between temperature and pressure?

 Another concern with scuba cylinders deals with Charles’ Law.  If you think back to your basic scuba class you might remember your instructor giving you a general rule for the increase in pressure in a scuba cylinder when it becomes heated.  More specifically, you might remember that for every one degree increase in temperature the pressure inside the cylinder increases 5 psi.  This is a general rule and is by no means accurate at all temperatures and pressures.  In order to more accurately determine the change in pressure do to a change in temperature two conversions are necessary.  First, just like using absolute pressures when figuring pressure changes underwater, you must figure the absolute pressure of the air in the cylinder.  To do this you need to add 14.7 psi to the tank pressure if you are at sea level (obviously, if you are higher than sea level you will need to add less pressure to get the absolute pressure of the tank). For example, if the tank you using has 3000 psi of air in it at sea level, then the absolute pressure of the tank is 3014.7 psi (3000 + 14.7).  Second, when figuring the change in temperature using Fahrenheit, you must convert it to absolute temperature (Degrees Ranken).  Absolute temperature is based on absolute zero which is the temperature at which all molecular motion stops.  In Fahrenheit, absolute zero is -460 degrees.  Therefore, anytime you want to convert Fahrenheit to absolute temperature just add 460 degrees to it.  For example, 72 degrees (room temperature) is 532 Ranken (72 + 460).  Next, if you know the original pressure of the tank (3014.7 psi) and the original temperature of the tank (532 degrees Ranken), all you need to know is the final temperature OR the final pressure of the cylinder.  Either one of these will allow you to determine the other.  For example, if the final temperature is 100 degrees, then the final pressure is 3158.7 psi (3014.7 x 560 ÷ 532 = 3173.4 - 14.7)  Basically, what I’ve done here is to set up two ratios:  1) 532 to 3014.7 and 2) 560 to something.  Then, I solved for something by cross multiplying 3014.7 x 560 and dividing that by 532.  This gave me the absolute pressure of the tank.  I then subtracted the pressure of the atmosphere to get the final answer.  My suggestion is that if you are having trouble with the math in this problem, then refer to the book, or email or call me about it, so that I can explain it more thoroughly.  

10.  If a tank starts out with 2500 psi of air at 50 degrees Fahrenheit, how much did the temperature increase if the final pressure is 3100 psi?

 With so many regulators on the market knowing a little bit about the inner working can help to make purchasing decisions.  To begin with remember that a regulator only consists of the first stage (that which attaches to the tank) and the second stage (that which is put in your mouth).  Everything else is considered an attachment and usually comes separate from the regulator when purchased unless sold as a package.  (We will address submersible pressure gauges and consoles later.)  The first stage has three pressure chambers.  The high pressure chamber takes air directly from the tank.  The intermediate pressure chamber hold reduced pressure transferred from the high pressure chamber and sends it the low pressure ports.  And, water pressure aids the mechanism spring to transfer air from the high pressure chamber to the intermediate pressure chamber.  Keeping that in mind, there are four categories that first stages come in:  diaphragm or piston; balanced or unbalanced.  Detailed explanations of the operations is beyond the scope of this writing.  You should consult your NAUI Master Scuba Diver textbook for detailed drawing and your repair technician for specific mechanical operations.  Most first stages are piston operated, with higher end models often being diaphragm.  As the names suggest, the difference between the two is in the operation of the intermediate pressure chamber.  With piston regulators the environmental pressure pushed directly on a working piston to adjust the intermediate pressure in the regulator.  In a diaphragm regulator the environmental pressure pushes on the diaphragm which adjusts the intermediate pressure in the regulator.  The intermediate pressure is that pressure which is sent to the second stage.  This pressure typically runs between 130 psi to 150 psi., depending on the make and model of the regulator.  The primary consideration for a first stage regulator is whether or not it is balanced or unbalanced.  In a balanced regulator the pressure from the tank exerts no pressure on the working of the intermediate pressure.  This is in contrast to an unbalanced first stage, where the pressure from the tank puts resistance on the opening and closing of the high pressure seat, which creates the intermediate pressure.  The bottom line:  a balanced regulator is not effected by tank pressure or depth and an unbalanced regulator is directly effected by both tank pressure and depth.  Unbalanced regulators are not designed to work well at depth, under low tank pressure or when there is excess demand, such as in an air sharing situation. 
 Second stage regulators also come in four categories:  upstream or downstream and pilot valve or mechanical lever.  The primary consideration is whether or not it is upstream or downstream.  In upstream valves the air pressure coming from the first stage puts pressure on the valve forcing it to close.  While the air pressure coming from the first stage puts pressure on a downstream valve, forcing it open.  (Pilot valves are almost all upstream, while mechanical levers are generally downstream.)  When purchasing a second stage regulator ask yourself the following question, “If the regulator mechanism breaks, do I want it to break open or closed?”  If the answer is open, giving you air while broken, then you want to purchase a downstream valve second stage.  If, on the other hand, the answer is closed, cutting off your air supply when broken, then you want to purchase an upstream valve second stage.  Both unbalanced and upstream regulators are designed to give the diver a regulator set-up that is functional under ideal conditions, but fall short under strenuous or adverse conditions.  No matter which type of regulator is purchased, it is important to consult the manufacturer’s warrantee when using mixed gases like nitrox.  Some manufacturers require that you install a nitrox kit before their regulators can be used with nitrox or the warrantee will be void.  Generally speaking, no modifications should be needed for your regulator as long as the nitrox mix does not exceed 40 percent.

11.  Compare and contrast the following paired terms:  balanced and unbalanced;  piston and diaphragm; upstream and downstream; pilot and mechanism.

 Compressor operations and maintenance can be the defining factor between getting employment in the dive industry or just visiting a dive shop.  Compressors are the backbone of all dive operations.  Think about it.  Without compressed air there would be no scuba diving; therefore, it is extremely important for dive operations to have a well maintained, functional compressor.  There are two main types of compressors:  high-pressure, low volume and low pressure, high volume.  Compressors used to fill scuba cylinders are high-pressure, low volume, similar to those used in industry, but with several modifications.  For instance, oils used in scuba compressors must use non-toxic oils.  Additionally, great strides must be made to prevent air contamination and to remove all of the moisture from the compressed air.  Low-pressure, high-volume compressors are typically used for surface-supplied diving.  With these compressors divers breathe air directly from the compressor or from a small reserve tank on the compressor.  The typical compressor set-up for filling scuba cylinders is to have a main compressor and filter system that is used to fill ballast tanks (also known as banks).  The banks are then used to fill scuba cylinders.  This keeps the compressor from running constantly, unless there is a high demand on the bank system.  A compressor operates on the principle of Boyle’s Law—as volume decreases, pressure increases.  Therefore, a set volume of air is compressed into a continually smaller compressor stage (head) increasing its pressure with each successive stage.  Air is prevented from returning to a previous stage by the use of one-way check valves located between each stage.  The final stage of the compressor sends the air through the filter to remove the last pieces of contaminants and then sends it on to the ballast or scuba tank(s).  Air compressors are rated by how many cubic feet per minute they deliver.  For example, a compressor that delivers 8 cubic feet per minute will take 10 minutes to fill an 80 cubic foot cylinder to 3000 psi.  As you can see delivering clean, non contaminated air is the dive shop’s primary concern.  It is, therefore, important to keep and maintain a regular maintenance schedule.  Changing the oil and filters on a regular basis, not only reduces the shop’s liability, but also increases customer satisfaction, by constantly providing quality air fills.  For additional information on compressor operations and maintenance, consult your Master Scuba Diver text, or your local dive facility.

12.  Draw a diagram of a shop’s compressor system.  Label all of the components and explain the function or operation that takes place at each location.