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Micro Dia-Vac® B-Series Diaphragm Pump Repair Instructions

Hello, everyone. My name is Chris, and welcome to our YouTube channel.

Today we’re going to be going over how to change a diaphragm on one of our Micro Dia-Vac® diaphragm pumps. When changing out a diaphragm, it’s typically done because the pump is starting to get a little bit of low performance and maybe low pressure, low flow. Or some people they just want to service the diaphragm at regular intervals. Whether that’s six months or a year, it really just depends on the application.

In order to change out the diaphragm on the Micro Dia-Vac® pump all we need are a few tools. First of all we need a 3/32nd Allen key, a 5/32nd Allen key, a torque wrench set to 28 inch pounds, a round object such as a bearing or an eccentric, a flat surface, and lastly a medium strength Threadlocker, such as Loctite 242.

The first thing I’m going to do is I’m going to remove these four head bolts on top of the head, and that’s going to be done with a 5/32nd Allen key. I like to leave the heads down in the head assembly just because there are lock washers underneath bolts and those can get lost pretty easily.

Now all four of our head bolts are loose, and now I want to pull up this complete assembly. When I say assembly, I’m including the valve body and the valve gasket that’s sandwiched in between it. We want to keep that altogether. We’re going to set that aside for now.

Then we’ll take a look at the diaphragm. This diaphragm is actually in good condition, but normally that diaphragm will have a tear or have some sort of other wear that will actually be inhibiting the performance. Then what we’ll do is we’ll grab our 3/32nd Allen key, and we’ll go ahead and we’ll remove the diaphragm plate screw. Then we’ll pull off the diaphragm.

This part underneath here is what we call the connecting rod cap. That’s what normally fits right underneath there. What I call this, which is the diaphragm screw, the plate, the Teflon washer, the diaphragm, and the cap I call it the diaphragm assembly. So we’ll go ahead and put that over here.

We want to grab our kit. This is a kit number 11461. It’s an all Teflon micro repair kit, and this is the most common repair kit, but depending on your model number you may require a slightly different one with different materials.

But in any case, we’ll go ahead and we’ll start with the diaphragm assembly. We’ll take the cap off. Then we will slowly remove the used diaphragm, discard those on the side, and then we’ll pull out the diaphragm plate, so we can get to this little Teflon washer seal, which we’ll pull off the back of the screw and discard that. Then we’ll go into our kit, which is going to include a valve gasket, a two-ply all Teflon diaphragm, very important, the two-ply diaphragm is one diaphragm. If it only uses one-ply, it’s not going to get the pressure and flow required. Lastly, real careful not to lose this, this is a small Teflon washer seal.

Grab the diaphragm screw, and we’ll go ahead and just put it right through the eye of the washer and then through the eye of the diaphragm plate. Then we’ll grab our two-ply, put it right through the center hole. Then lastly, we’ll grab our connecting rod cap and we’ll slide that right on the backside.

Now what we want to do to prevent this from backing out is we want to use a medium strength Threadlocker, like a Loctite 242 Blue, put a little dab on the end of the threads there. Then we’re going to line up our connecting rod. I usually like to use my left hand on the backside to line it up right. I just want to get it just kind of started, just like a thread or two so I don’t lose it.

Then without getting too tight, I’ll go ahead and make sure everything is lined up. Now, what I’m going to do is back to my head assembly I’m going to borrow two head bolts. I’m going to install one diagonally here and one diagonally here. Just make sure my diaphragm is clean of any sort of contaminates or debris. Got those on a few turns, and then I’m going to grab my 3/32nd Allen wrench and I’m going to start to tighten down the diaphragm screw.

The bolts are on there. They’re going to keep it nice and centered, and just want to get that hand tight. Remove our head bolts, and we’ll place those back in there.

Now, our diaphragm is on. Now, we want to focus on the head. Here we have our head assembly. We’ve got an inlet port here, outlet port there, four head bolts. We need to change out the valve gasket. What we’ll do is we’ll pull this apart, put the valve body down over here, and we’ll pop these screws.

I like to be careful with these screws and not pull out the lock washers because they’re small and can get lost easily. If we just pull those bolts out without losing the lock washers, we can take that head and just set it down right here. This is our old gasket. We’ll go ahead and discard that. Take our new gasket. What I like to do because sometimes in shipping it can get a little bit of a wave in the diaphragm, it’s really important that these seals right here are really nice and flat relative to this round edge right here. What I’ll do is I’ll grab a flat surface and place it down. Then I’ll take the diaphragm and I’ll put it down. Then I’ll take the round object, such as a bearing, like I said, or an eccentric or a bushing, and I’ll get this and I’ll just rub away from me on the flapper valve, just to get a nice flat surface on them, a couple of times.

Really important, you don’t want to go back and forth on it because that can stretch the gasket in the wrong way. So just right away from us, just press down, real nice and smooth. We’ll flip it over and get the other side. Now, we’ve got a nice flattened gasket, and we’ll take our valve body which has a small little slot right here in the side which, of course, also the gasket has.

What we want to do is we’re going to line up those slots, so that they’re in alignment. Then we want to grab our head, keeping it upright so we don’t lose our four lock washers. It’s also got a slot right there on the side. We’ll go ahead and we will find the slot and we’ll align it right on top of the valve body on the slot, like so, making sure that we don’t press or pinch any of the valves. Then keeping that upright.

Then we’ll take the four bolts with the washers all ready down there, and we’ll just place them right on top in there. This head assembly can be moved as long as you’ve got the valve body together with it. It can be rotated in any position to make your plumbing easier. It’s very important that you’ve got to move both the head and the valve body. I typically install it so that my inlet port is on the top, discharge port is on the bottom.

We’ll place that directly on top, get these screws just threaded a couple of times, nice and good. Then we take our 5/32nd Allen key, and I like to just get these started just so I know that my gasket is not shifting anywhere.

Now, I’ve got everything on there nice and tight. Lastly, we’re going to take our torque wrench set to 28 inch pounds, and we’re going to just make sure that we’re nice and tight on our four head bolts. That will prevent the pump from leaking. It’ll also make sure you get a good seal and good performance. There we go, like so.

The pump is now assembled, ready to go. The first thing I recommend is to test the unit to make sure you’re getting the proper performance. What we want to do then is connect the power, whether that’s 115 or 230 volt. The wiring is located on the backside of the pump. We want to make sure the pump is getting actual performance. Depending on the eccentric size, which you can find on our website at, you can see the max flow, pressure, and vacuum.

In this case, we have a B161, so you should get around 7 liters per minute open flow, about 22 inches of mercury ultimate vacuum, and about 30 PSIG as ultimate pressure. You know that if your pump is achieving those marks, then you’ve done the install correct and the pump is ready to go.

Methods for Diaphragm Pump Selection

Part 1: Pressure, Vacuum, and Flow

Pressure and Flow
For most sampling applications, the following information is sufficient in determining the type of pump to select:

  • Required Vacuum
  • Required Pressure
  • Sample point conditions
  • Required Flow Rate
  • Temperature and Type of Gas being pumped
  • Ambient temperature where pump will operate
  • Distance and diameter of tubing
  • Voltage, frequency, and classification of motor

If the required vacuum is not known, you will need to calculate the pressure drop from the sample point to the pump inlet. ADI can perform this calculation. What we need to know is the required flow rate, line distance and diameter, Gas composition and temperature and initial pressure at the sample point.

If the sample gas is venting to atmosphere downstream, then only the vacuum needs to be calculated. If the gas is returning to a flare or back to process, then the pump will probably require pressure to get there. Again, ADI can calculate this – however we will need to know the pressure at the return point.

Reading the Curves

  • The pump curves we provide are really (2) curves plotted onto (1) graph.
  • The left side of the zero is inlet vacuum vs. flow rate with the assumption that the outlet discharges to atmospheric pressure (or close to it).
  • The right side of the zero is outlet pressure versus flow rate with the assumption that the inlet pulls from atmospheric pressure (or close to it).
  • In applications where the pump is pulling a vacuum and providing discharge pressure; we have another set of curves called “combination curves”.
  • Please contact ADI in these cases.

Vacuum Example

  • If the inlet pressure drop is calculated as 5 InHgG at 8 SLPM and the sample vents to atmosphere, then all we need to do is find a pump that will provide ≥ 8 LPM at this vacuum. See below.

Mini Diaphragm Pumps

Pressure Example

  • If the pump is located close to the sample point and the downstream pressure required is 5 PSIG @ 6 LPM, then all we need to do is find a pump that will provide ≥ 6 LPM at this pressure. See below.

M-Series Diaphragm Pumps

Pressure and Vacuum Applications
Say an application requires a pump to pull through 200′ of 3/8″ sample line, flow to an analyzer, and then return to a process line 350′ away. In this case, the pump will be required to pull a vacuum on the inlet, provide flow to an analyzer, and provide positive pressure to the process line.

  • For this we must use what we call “combination curves”.
  • These curves show a pump’s flow rate at a given vacuum and outlet pressure.

Combination Curve Example

  • In this case, we need to pull 10 InHg @ 7 LPM to draw the sample, but also provide a discharge pressure of 10 PSIG in order to push the sample back to the process line. See below.

Pressure Vacuum Combination Curve

Pressure Boosting Applications
In some cases, the process line may be under positive pressure when it reaches the pump inlet. If the gas sample must then be pushed back to a process line, a pump can be used to “boost” the pressure. When the pump inlet pressure exceeds 0 PSIG, the pump performance capabilities (in terms of discharge pressure and flow rate) can increase significantly. It is very important that under these circumstances specific calculations are done by ADI to avoid oversizing the pump; which can lead to premature diaphragm, bearing, and motor wear. The information we require in these applications (in addition to gas type and temperature) are pump inlet Pressure (PI) , Pump outlet Pressure (PO), and flow rate.

With the right collaboration, ADI can ensure that your next pump is optimized for the application. Should you have any further questions or concerns, please do not hesitate to contact Chris Williamson ( or Greg English (

Dia-Vac® Diaphragm Pump Repair Instructions (R, M Series)

Hi, I’m Chris. Welcome to ADI’s YouTube channel.

Today we’re going to go over the proper installation of our diaphragm pump repair kit. This is our 11005 diaphragm pump repair kit. It’s a Teflon EPDM kit. It’s our most common diaphragm. Really, any of the other materials, whether it be all Teflon, Teflon/Viton, or Viton, you can follow along with the same sort of instructions and you’ll get the same result.

Also, any of our pumps that use what we call our standard head right here, this square head, whether it’s our mini Dia-Vac® pump as you can see right here, or an explosion proof with a different motor, anything that’s got this sort of a head… there may be a different shape in the diaphragm. For example, the mini uses a round. But you can see it’s still Teflon coated and EPDM, and really the instructions are the same for that one as well.

What we’ll need in order to do this change-out properly are a few tools. First of all, we’re going to need a 5/32 Allen key. Then we’re going to need a 3/16 Allen key. We’ll need a 3/16 torque wrench, set to 110 inch pounds. A 5/32 torque wrench that’s set to 70 inch pounds. And a bottle of Loctite medium strength 242 or equivalent.

The first thing that we’re going to want to do, of course, on the head is remove the four head bolts. So we’ll grab our 3/16 Allen key, and we’ll go ahead, break the seal on that.

Okay. Now that our four head bolts are loose, we’ll go ahead and remove them, and just place them somewhere where you’ll find them later. Then now our head is able to be taken off the pump.

You can see here the diaphragm. Where you would normally find wear is along this diaphragm. Obviously, this diaphragm is still good. You may even see some of the EPDMs start to impede if the chemical has actually attacked the diaphragm.

In any case, this is the inside of our pump head. This is the valve body. What’s nice about this pump head is because the valve body is inserted and married into this part, we can position this in any position, and as long as this valve body is inserted, it will always flow in the direction of the gas.

What we’ll do is we’ll put the head aside for now, and we’ll take a look at the diaphragm. Now you can see this diaphragm is okay, but typically a worn diaphragm, you’ll start to see some cracks around here. You may see some of the EPDM flake up depending on how long it’s been in service.

What we want to do is grab our 5/32 Allen key. Insert it into the diaphragm screw. Now that it’s loose, we’ll go ahead and remove the complete diaphragm assembly. What that diaphragm assembly is made up is of a screw, a Teflon washer seal, a diaphragm plate, and then of course the diaphragm. The first thing we’re going to want to do is pull off the old diaphragm. We’ll discard it. Then we’ll pull the head out and remove the Teflon washer.

Now we’ve got these parts, and we’ll go ahead and we’ll go into our kit. I’ll go ahead and just pull out the washer for now. We’ll take our screw and just thread it through like so. Then we’ll take our diaphragm plate, place the screw in there, take the new diaphragm, place it through the center hole, and now I’ve got a new diaphragm assembly. Next part, we’ll grab our Loctite. One drop of Loctite on the thread. Place it over the connecting rod. 5/32 Allen, and then we’ll begin to tighten that down.

We’ll go ahead and grab the 5/32 torque wrench at 70 inch pounds. Make sure it’s nice and tight. Now our diaphragm is good. Then what we need to do is change out the inner components of the head, which includes the gasket and the two valve discs. Again, we’ll grab our 5/32 Allen key, and we’ll want to just unscrew these top valve body screws here on top of the head. Now it’s really important for me and my left hand to keep it underneath the head here. That prevents the valve body from falling out once these are loose. So we keep pressure under there, we hold it, and then nothing gets lost. Our valve body drops right out. We’ll put our head to the side.

Inside here we can see the gasket. We can see the discs. These may wear before the diaphragm, but most people like to just go ahead and change out all the parts at one time while the head’s open. We’ll go ahead and take out those valve discs, discard them. Then we’ll take the old gasket, discard that. We’ll go back to our repair kit, and we’ll pull out the gasket. When you look at the valve body, you can see that one of the posts has two splices on the end of it. That’s the one that you’re going to want to put with the bigger hole, but it can only go in one direction. Then we’ll take our new valve discs, place them in. They should have a little bit of movement to them.

Take care to keep it nice and flat, and don’t allow the discs to get up on the posts. What can happen is you put the head on it, and then it can become pinched. Now we’ll take our head, and you can see that this is the one with the posts. Lines up with this one with posts. We’ll go ahead, keeping it flat the whole time, we’ll marry those parts together. Always putting pressure underneath the head to hold it in place, and then we’ll take our valve screws and place them on top. Again, using our 5/32 Allen key, we’ll go ahead, all the while keeping this tight. We’ll get that, give it one turn, then give it one turn, so it’s nice and tight. Now I can release it. It won’t fall out.

Now, we’ll orient the head onto the pump. The way that it’s going to go from the factory is from right to left, but again, this pump can be in any position, and it will always flow in the direction of the arrows.

Let’s go ahead and line it up there. We’ll go back to our original head bolts. Put those on like so. Then we’ll grab our 3/16 Allen key and go ahead and get these started. We’re almost there. Now our head’s installed correctly. In order to ensure that we don’t have any leaks, we don’t have any performance issues, and have a nice good seal, I want to make sure that we torque down our screws. Valve body screws are going to be set to 70 inch pounds. Then we’ll grab our 3/16 torque wrench, set for 110 inch pounds, and now we’ve got the diaphragm back installed into the pump.

Everything should be working good. The way you’re going to want to test it, on a general purpose motor, the electrical component is in the back here. You’re going to want to wire it for 110 or 220. Wiring instructions are located on all the motors. You’re going to want to plug it in, and then you’re going to want to check out which eccentric size you have, which you can find at our website at It’ll be on the very front of the model number. Depending on the eccentric size, you’ll get different flows and pressures.

In this case, we have an R-221. Once we do our install of our diaphragm, we want to go ahead and test the pump and make sure that we didn’t make any mistakes and that it’s working properly. We’ll do that by adding power to it, and then we’ll put a pressure gauge on it.

This pump should be around 50 PSIG on the discharge. The inlet should get about 22 inches of mercury, and the flow should be approximately 26 liters per minute. If your pump is getting all those three numbers, then you know you’ve done the install correctly and the pump is ready to go and be installed in the system.