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 airdimensions.com, 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.