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Downtime Eliminator: My Diaphragm Pump Is Not Working

on Apr 11, 2019 in How-To Tips

Downtime Eliminator Flexo printing
Problem: My diaphragm pump isn’t working.

Answer: We have had a lot of operating software upgrades over the years so there are different control systems out in the field. As a result, this topic can get pretty in depth. I’m going to keep this as simple and to the point as possible. I’m going to steer away from 100% pneumatic units as those are an entirely different animal. Parts washer operations, while different, use a lot of the same principals as anilox roll cleaning units. So, if you have an electric parts washer, a lot of what I’m going to go over will also apply. Read on to troubleshoot your problem.
diaphragm pump parts washer
Is Wash Time Selected/Programmed?
First and foremost, on any Flexo Wash unit, there has to be a wash time selected/programmed into the unit. On older narrow web units, there’s a switch on the front of the units to select wash 1, 2 or 3. On newer narrow web units, wash times are programmed into the LED Display (which there are also three programs) and then you select which program to run via that display screen. Older wide web units only give you the option of one programmed wash time, while newer versions will give you several programmed wash times. Regardless of the unit, you must have a wash time programmed in or the diaphragm pump will not come on.

What Should Happen When You Press Start
Now that we have got that squared away, let’s quickly review what’s supposed to happen when you press the start button. First, the drain valve switches from drain to waste (or drain to rinse as in a parts washer) to drain to solution tank (or tank 1 in a parts washer). Secondly, the lid lock engages so you can’t open the lid. Lastly, the diaphragm pump comes on. Remember, some parts washers and wide web units have two valves on them. That means you have to have the waste valve closing (or rinse tank valve in a parts washer) and the drain to tank valve opening for the unit to start.

Is the Lid Sensor Working?
Let’s say you have a narrow web anilox cleaner or parts washer, and you press start but the valve doesn’t switch, the lid doesn’t lock and the pump doesn’t come on. You find that odd since the rotation motor (or slide motor in a parts washer) is now running. Whelp, you’ve got a bad lid sensor and the unit has defaulted to manual rotation/slide. If you have a bad lid sensor on a wide web unit, you may get an alarm stating the lid isn’t closed or you see the word “starting” on the screen. You then have to go in and check the inputs to make sure that the lid sensor is actually sending an input. Here’s the kicker, on really old units, you don’t have an input screen so you have to check on the PLC input card for that signal.

Check your Drain Valve
Here’s another scenario: You push start and the lid lock engages, the rotation/slide comes on, your display screen says washing but that pump still isn’t coming on. Notice I didn’t say anything about that drain valve switching. On narrow web anilox units, the diaphragm pump and drain valve are on the same air solenoid. That means they are on the same output of the control system. So, if that valve didn’t switch and the pump didn’t come on, then either the solenoid valve is bad or we aren’t getting the output from the controls (which means we may have a bad controller). 

Wide web anilox cleaners/parts washers and some narrow web parts washers are a little different. I mentioned above that these units have two valves on them. There are sensors on these valves and if the valves don’t switch correctly (or in the correct amount of time), then the unit is going to fault and that pump isn’t going to come on. You would need to check and make sure that the valves are actually switching or the sensors on the valves are sending the correct inputs. You may have a bad solenoid on one of those valves or something stuck in the drain valve itself which is not allowing it to open/close.

Air Needs to Be Running through the Pump, Not Water
Last scenario for today: You press start, the lid locks, the rotation/slide comes on, display screen says washing (or counting time down), the valve switches but that pump just isn’t running. The first thing to do is pull the air line off the pump and make sure there is air coming out of it AND NOT WATER. Truth: we have had a few people call in here about their pump not working and when that air line is pulled off, water runs out of it. The air chamber in the pump was full of water as well. Diaphragm pumps don’t run on water FYI. If you don’t have air, then there’s a leak in the line somewhere or a bad solenoid valve. If there is air, then the flow valve on the front of the pump may be bad. We have seen the spring in these flow valves break, which drops the needle inside of that flow valve down and cuts air off to the pump. I would suggest taking that off and putting the air directly to the pump to see if that makes that pump come on.

If direct air to the pump doesn’t make it work, try taking the muffler off of the back bottom side of the pump. Those mufflers are porous and they will get clogged up over time which equalizes the pump. Diaphragm pumps have to discharge air to work correctly.

What If Pump is Running, but Not Pumping Solution Out Correctly
If none of the above gets that pump going then I’d say it’s a goner. More than likely, the switch valve has frozen up. Please remember that everything we have discussed above is if the pump isn’t running at all. If your pump is running but not pumping solution out correctly, then there is either a bad diaphragm, a broken shaft inside of the pump, the valve balls have swollen/stuck in the chamber or that flow valve is causing you an issue. The easy way to check for a bad diaphragm is to pull that muffler off and see if it is wet or solution is leaking out of that muffler port. We do sell replacement diaphragms, valve seats, balls and mufflers for those pumps.
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