PADI Divemaster and Instructor exams, Scuba Equipment, How it works

hi this is a video to help you prepare for the dive master and instructor level dye theory exam specifically dive equipment in this one of a few videos I'm going to be making based on dive equipment I'm going to be looking at regulator first stages there's just a few things you'll want to know about regulator first stages in order to be able to answer the questions that may come up in your exams the key things that we're going to be looking at is the way a first stage actually works we're then going to look at the difference between din and yoke first stages balanced and unbalanced first stages and piston and diaphragm first stages so what are the different types of first stage well the first thing to realize is that all first stages are designed to do approximately the same thing they do differ in a few subtle ways they differ based on the type of valve that they're designed to connect to you've got the din and the yoke valves and regulators you've then got differing performance you've got balanced and unbalanced regulators and then you've also got subtle differences in the actual design of the first stage diaphragm and piston first stages we're going to be looking at all of those things in this presentation so how does a first stage work well a scuba first stage is designed to reduce high pressure air from the tank to an intermediate pressure above ambient it's critical to understand the importance of ambience and ambient pressure basically the human body cannot actually breathe air supplied to it that is at a significantly different pressure from the pressure surrounding it so what was tricky in inventing and designing a first stage for use when scuba diving was the fact that this regulator had to be capable of changing the pressure at which it was supplying air to a diver based on the surrounding the diver as you probably hopefully know the deeper you go the more pressure you're under therefore the deeper you go the higher the pressure that the regulator has to provide air to you at so somehow a regulator first-stage had to be designed so that it knew what pressure was surrounding you the diver and was able to adjust the pressure it was providing air to you at according to that ambient pressure surrounding it so let's have a look at basically a cutaway of an unbalanced piston first stage to understand a little bit more about it so I've been talking about the importance of ambience and the first stage delivering air to you at ambient pressure well here we can see how a regulator does that we've actually got holes in the side of this regulator that allow the water to enter this middle chamber of the regulator and the water entering this middle chamber will of course exerts pressure downwards on this piston the chamber is split off from the other two chambers that you can see here you can see an o-ring here as you can see an o-ring here which means that no air or pressure can be transmitted through this way the only way the pressure can be transmitted is by pushing this entire piston downwards the other thing that is exerting downward pressure on this piston in this diagram is the spring here the spring is trying to push this piston down and because the tank the regulator in this picture is not connected to a tank or anything it is successfully pushing that piston down to the limit of the springs travel so there are basically two things that are pushing this piston down the pressure it's under right now if it wasn't connected to a tank and it was on the surface in air there would be one atmosphere of working pushing this piston downwards in addition to that you've got the pressure of the spring that is also working to push this piston downwards the pressure of the spring would be something that would be designed in the factory there are various ways that the force that the spring pushes down on can be adjusted but basically we actually refer to the force or pressure that this spring is exerting as the intermediate pressure so what else have we got here well if we look at this this is the orifice that the air would enter the regulator through from a scuba tank and this is the orifice that the air could leave the first stage to travel to the second stage so we have high pressure air coming in from the tank into this top chamber here and it can actually travel down through the tube in the middle of the piston shaft here and it would also fill the bottom chamber here so these two chambers are connected here and both of them would become pressurized when attached to a tank and turned on so let's have a look at that like this so now we have got the area of the first stage which becomes pressurized by the tank highlighted in red and that's pretty important to understand this diagram again we can see that the valve is in the open position it's not pushing closed the the hole the orifice that the air would be coming into the first stage through so now let's imagine ourselves turning on the tank we hear that hiss of pressure going into the first stage we see the hoses getting a little bit stiffer as the air travels down to our second stages etc and then it stops so what happens is this pressure has poured into the first stage it's pore filled the hoses it's it's in the second stages and it's poured down into this second chamber here and now there is pressure trying to push upwards on this piston when the pressure trying to push upwards on this piston is greater than the pressure of the spring the intermediate pressure plus the ambient pressure then the piston will be pushed up the pressure below it exceeds the pressure above it it will travel in an upwards direction when it does that the valve seat here closes off the orifice that is the air coming in from the scuba cylinder and no more air can enter this first stage from the scuba cylinder and we have a pressurized system so that is basically how a first stage works let's now think about what happens when we inhale well when we inhale what will happen is that the pressure here will drop and remember the pressure here is the pressure in all these areas filled with red and when that pressure drops the first stage will the piston in the first stage will open again air will once again flow from the cylinder it'll flow down the hose to the second stage it'll flow down the center of the piston shaft here and and keep flowing into this chamber but as long as the diver is inhaling or you're perhaps pushing the purge button air will just flow and the pressure in this chamber will be lower than the pressure exerted by the spring and the intermediate pressure working together and air flows the moment we stop inhaling the pressure will very rapidly increase in this area and close off the the valve again the piston is now been pushed into the upward position the valve is closed the pressure in this red area exceeds the pressure exerted by spring and ambient pressure and we have a system where the regulator is closed there is no air flowing down to the second stage now and is basically how a first stage works so the key thing to realize is that regardless of what type of regulator we're talking about any scuba first stage is designed to reduce high pressure air from the cylinder to an intermediate pressure above ambient this is the cutaway of an unbalanced piston first stage regulator in the closed position when the diver is not inhaling the air inside the intermediate pressure chamber applies a force to the piston that is equal to the force of the bias spring plus ambient pressure the piston does not move and the valve stays closed when the diver inhales air pressure in the intermediate pressure chamber drops the valve opens and air flows when the cylinder is full opening force on the valve seat is greatest and breathing effort at its lowest as cylinder pressure drops breathing resistance will increase that video is from the multimedia version of Paddy's encyclopedia over recreational diving so what we now need to do is have a look at the other things to start with din versus yoke regulators so there are some subtle differences in din and yoke regulators they're definitely popular more popular in some areas of the world than others North America tends to have a lot of yoke regulators Europe tends to have a lot of denne regulators what are the differences well the yoke regulator and the din regulator one of the key differences are the way they're attached to the tank and the positioning of the o-ring so when we look at this yoke valve tank valve on the right over here what we can see is that the o-ring actually is seated in this little groove here this is a picture of a tank that knowing and it would be seated in there before placing the regulator onto the tank when the regulator is put on the tank this flat bit of the regulator here would be what would push against the o-ring creating a good seal between tank and a ring and also making sure that the o-ring is held firmly in place so I stuck at the yoke regulator as almost a kind of clamp obviously screwing down on this handle here pushes closed the screw and clamps the regulator to the valve now this is where I feel that the yoke regulator has a slight weakness if we look at these two divers here and focus in on their their yoke screws here they're pretty high up above their heads now if you were to go into an overhead environment go through a swim through and misjudge slightly you could potentially smack this yoke handle against the overhead environment that would be pushing the the yoke handle in this direction and therefore it would be actually putting pressure on the top of the o-ring that be greater pressure exerted on the top of the o-ring and pressure on the bottom of the o-ring might be reduced now if this was a hard enough knock it is just possible that that could actually dislodge the bottom piece of o-ring here and the now the the tank air would be just pouring out the gap made in the bottom of the o-ring here and you would be losing the air from your tank very very quickly so definitely one of the weaknesses of a yoke regulator system is the way that the o-ring is held in place and the greater probability of a out of air situation as a result of a dislodged oring so when we look at the din system what you've got is you've got a regulator that is actually threaded and it screws in to a threaded tank valve the o-ring on the regulator is actually attached to the regulator rather than the tank valve and it's in this position here so when the regulator is screwed into the tank valve the the o-ring will actually be be pushing deep pushing against this this part of the valve deep inside the valve so that makes it a much more encased o-ring much more difficult to dislodge so a yoke regulator and valve is more like a clamp the earrings on the tank valve impressed by the regulator on tightening a din regulator is screwed actually into the din valve which is a threaded valve the o-ring is on the regulator and encased deep inside the valve now the sort of question you might face in an exam might be to somehow describe the differences between the system it shouldn't be too difficult to remember which type of regulator is screwed in so now we are looking at the differences between a balanced and an unbalanced first stage the basic difference is a difference in performance but why does a balanced first stage perform better than an unbalanced first stage well it all comes down to this area here when we look at this area here what we can see is that high pressure air from the cylinder is just coming down through this orifice and trying to push push its way past this valve see now the only thing that is stopping this high-pressure air from pushing its way past the valve seat and into the first stage and therefore on the second stage etc is the pressure in this chamber which is working in the opposite direction trying to push the piston up this way and close this hole so basically the fact that this area here is a much larger surface area than this area here is what allows a reasonably small amount of pressure here to be able to close this valve here against a fairly high tank pressure coming in here it is simply the mechanics of pressure exerted over a small area versus pressure exerted over a larger area so basically in an unbalanced first stage this orifice is made very very small to mean that the high pressure air coming from the tank has a very very small surface area to work on meaning that air are the pressure that is only ambient plus intermediate is able to work on the piston at the bottom here and and actually close off the supply of our when we don't want air to flow so on the balanced first stage again the this is in the closed position what you can see here is air is coming in and it's filling this entire chamber it is not working directly against the valve stem in the way that the air is working directly against the valve stem over on this unbalanced first stage so what happens is the air comes in it fills this area and in the open position let's have a look at it in the open position right now in the open position this this air is coming in it's able to force its way down down this tube it can flow to the second stages the low pressure inflator hose etc and it can fill up this chamber area here Media pressure chamber the moment air stops flowing you stop pushing the purge button or you stop inhaling or you stop hitting your BCD inflator button the pressure will very quickly rise in this area pushing the piston in this direction pushing the piston stem against the valve seat here but since the high pressure air from the tank isn't working directly against it it's easier for the pressure in this intermediate chamber to actually push closed the valve stem against the valve seat so this subtle change in design that we can see here basically means that we can have a larger orifice on a balanced first stage then you would be able to have on an unbalanced first stage simply because high pressure air from the tank is not working directly against the valve valve stem so that is basically what makes a balanced piston first stage perform better is the fact that in a balanced piston first stage we can have a larger orifice that the air enters from the tank here's a video from Patty's multimedia encyclopedia of recreational diving explaining the same thing in a different way this is a cutaway of a balanced piston first stage regulator in the closed position when the diver is not inhaling the air inside the intermediate pressure chamber applies a force to the piston and as equal to the force of the bias spring plus ambient pressure the piston does not move and the valve stays closed when the diver inhales air pressure in the intermediate pressure chamber drops the valve opens and air flows because air from the cylinder never exerts pressure on the piston stem base cylinder pressure has little bearing on breathing resistance so the key points to understand that cylinder pressure has less influence on the operation of the valve since acts all around the valve stem when we're talking about a balanced regulator this means the falling tank pressure actually has less effect on the amount of breathing effort required to open the valve it means that in a balanced regulator as tank pressure Falls you the diver won't notice a significant difference in the amount of breathing effort required to take a breath now the balanced regulator also has a larger orifice to allow the air to flow from the tank it's able to have that larger orifice for reasons explained earlier and this larger orifice allows for a greater airflow it makes a balanced regulator more capable of supplying air to accessories than an unbalanced regulator it also makes a balanced regulator more capable of supplying the needs of two divers if you had a buddy hood run out of air and was using your alternate air source a balanced regulator would better provide your needs so a good thing to basically remember that is that a balanced regulator is generally better in in every way and if you remember that when you're trying to answer questions on the differences between balanced and unbalanced regulators that should significantly help you in your exams so the final thing that we need to look at is the difference between a diaphragm and a piston first the differences are pretty subtle and they're all about the area that the water enters the first stage now in the first part of this video we understood the importance of why the water needs to be able to enter the first stage the water entering the first stage is what effectively tells the regulator what the ambient pressure surrounding the diver is that water exerting pressure on the moving parts of the first stage allows the first stage to deliver air to the diver at an ambient pressure above that an intermediate pressure excuse me above ambient pressure so in a diaphragm first stage the water would enter through a hole here and the only areas parts of the first stage that it is exerting that is is coming in contact with is the spring here the walls of the first stage here and a rubber diaphragm so there aren't many of the moving parts of the regulator coming in contact with water whereas on a piston first stage the water is coming in here not only is it in contact with the spring the buyer spring and some of the walls of the first stage it is also coming in contact with an o-ring here and o-ring here and the whole top half of the the piston and a large amount of the piston stem so far more of the moving parts of the regulator come in contact with water in a piston first stage than they do in a diaphragm first stage and when we think about water ingressing into a first stage that water could potentially carry tiny particles of sediment which over time could build up and of course the other big problem with water especially saltwater is its ability to corrode so corrosion in a diaphragm first-stage can really only build up around the the bias spring and on the walls of the first stage here this would be made of rubber and not susceptible to corrosion whereas on a piston first stage corrosion could not only build up on the spring and the walls of it they could also build up on the piston itself and the piston stem which is moving back and forth between this o-ring potentially causing bigger problems more quickly with piston first stages than diaphragm first stages this is a cutaway of a bound diaphragm first stage the first stage of a regulator is the assembly that attaches to the tank valve it reduces high-pressure air from the tank to an intermediate pressure and delivers it to the second stage through the regulator hose the diaphragm is a flexible rubber disc with water on one side and intermediate pressure air on the other the first stage is in a closed position until a diver begins to inhale when a diver begins to inhale pressure within the intermediate pressure chamber instantaneously drops causing the bias spring and ambient water pressure to push inward on the diaphragm this opens the valve seat on the poppet assembly the first stage is now open with the poppet assembly open high-pressure air from the scuba cylinder flows into the high-pressure chamber then into the intermediate pressure chamber then through the regulator hose and finally to the mouthpiece on the second stage this flow continues as long as the diver inhales when the diver stops inhaling air pressure instantaneously built within the intermediate pressure chamber until it equals the ambient water pressure plus by a spring when the pressure is equal the poppet assembly closes sealing the valve orifice air flow into the second stage from the first stage is always at an intermediate pressure of seven to ten bar or 100 to 150 psi above the surrounding water pressure the bias spring strengths determines this elevated air pressure so the main difference between the piston and the diaphragm first stage design is what parts of the regulator the water comes in contact with water comes in contact with significantly more moving parts in a piston regulator than in a diaphragm regulator this increases the chances of sediment or corrosion buildup in a piston regulator there's more chance of that causing problems in a piston regulator than there is in a diaphragm regulator however of course if you get your regulator serviced as often as you should once a year it shouldn't really be a problem in either type of regulator so what have we looked at in this video we've looked at the basic way a first stage works we've looked at the differences between din and yoke first stages we've looked at the differences between balanced and unbalanced first stages and we've looked at the difference between piston and diaphragm first stages the next video we'll discuss second stages but before we do that I think we owe a big thanks to a particular person merci Jacques he's the guy who invented the first stage

Channel: PADI IDC Roatan, Bay Islands, Honduras

Views: 17,795

Rating: 4.9024391 out of 5

Keywords: Divemaster Internship, PADI, PADI Instructor, Scuba Instructor training, IDC, Divemaster Course, PADI Instructor course, Roatan, Bay Islands, Utila

Id: r4_dFkZBrQQ

Length: 28min 13sec (1693 seconds)

Published: Thu Feb 22 2018