Diagnosing Common Fence Paint Spray Equipment Problems
With our combined 100+ years of paint spray equipment knowledge we are constantly contacted and asked to help diagnose fence paint spray equipment problems. We are happy to help in any way we can but think it may help to have a written flow chart to help in the fixing of equipment. We hope this helps.
We must first make a few assumptions.
The vast majority of equipment we see are piston type sprayers. This post assumes you have a piston type and not a diaphragm type sprayer.
We are also assuming the piston is moving up and down. If the piston is not moving up and down the problems is either in the hydraulics, motor or the clutching mechanism. This blog is not meant to cover these problems, please feel free to call if your piston is not moving.
The above two assumptions means you have a problem in what we refer to as the lower unit. This is the actual paint pumping portion of your machine and where we see the majority of problems.
In order to perform the majority of these tests, it is necessary that the pump is operational and has not deteriorated past this point. Most of the time you will notice a reduction in efficiency prior to the pump becoming totally in operational. This is the best time to diagnose what may be wrong. These test will still aid in diagnosing after this point, but will become more difficult.
In order to understand this blog it is important to understand the very basic operation of your machine. Please refer to the simple drawing of a lower unit below in the following explanation. Also included are example pictures of Titan Hydra Pro IV parts mentioned in the diagnosis. The basic parts are the same for other piston pumps, however they will vary in size and shape.
On the upward stroke of the machine, paint is moved in two isolated and separate ways. The paint in the upper paint area (as labeled in drawing) is forced out of the outlet and into the paint hose and subsequently through your tip at very high pressure. This is accomplished by the upper ball seating on the piston valve (with no leakage) and the lower packings preventing any back flow into the lower paint area. This is a pretty easy concept and not too difficult for most people to comprehend.
Simultaneous to this, the lower ball is forced off the foot valve allowing paint to fill the lower paint area. Likewise this is pretty simple to envision.
The downward stroke is more difficult for most people to understand.
On the downward stroke, the upper ball is unseated and the upper paint area and the lower paint area reach the same pressure. There is free fluid movement between these two areas.
Simultaneous to this, the lower ball is seated onto the foot valve preventing back-flow (with no leakage).
As the shaft moves downward into the cylinder, the volume of the upper paint area plus the volume of the lower paint area is reduced by the volume of the shaft that is entering the cylinder. Picture a very full glass of water as you lower your finger into it. The glass will overflow by the volume of the finger entering the glass.
An amount of paint equal to the volume of the shaft, as it is lowered, is forced out the outlet and into the hose and subsequently through your tip at a very high pressure.
Repeat over and over.
Now let’s start finding your problem.
With two exceptions, internal paint leakage is the problem with virtually all lower unit problems and there is only three places this can occur.
Paint can leak around the lower packings on the up stroke.
Paint can leak through the piston valve on the up stroke.
Paint can leak through the foot valve on the down stroke.
The first of the two exceptions is paint can also leak through the upper packings. This is not internal leakage. This paint will exit to the ground and it is obvious what is occurring. Paint will be leaking from the top of the cylinder around the piston.
We used to paint so we understand that disassembling the machine is very messy and time consuming. We like to perform several very quick, simple and clean tests before any tools come into play.
The first diagnostic test we recommend is to see in which direction we can get the shaft to come to a complete stop (and hold there). If you can get your shaft to come to a complete stop on the down stroke, you know the foot valve and lower ball are seating without leakage. If there is leakage, even with no paint exiting through the tip, you have paint leaving the pump and returning back into the drum or pail and the shaft will not stop. If you can get the shaft to come to a complete stop on the up stroke, you know there is no leakage around either the lower packings or around the piston valve and upper ball. If paint leakage occurs in either of these two areas, paint moves from the upper paint area and into the lower paint area and the shaft cannot come to a complete stop on the up stroke.
If the pump will stop on the up stroke and not on the down stroke there is another test to confirm a leaking foot valve. If possible, depending on your exact setup, find a way to see the exact spot paint enters into your system. If you are using a drum tube this would be the end of the tube. If you are using a pail tube this would be the end of the pail tube. If you are inserting the lower unit into a 5 gallon pail, this would be the lower unit inlet. Now isolate this point to just under the surface of the paint (hold your drum tube or pail tube just under the surface of the paint where you can see it). On a properly operating machine you will see paint move to enter the tube on the up stroke (this is easier to see than it sounds). On the down stroke the movement will stop and paint will not enter or exit the tube. If paint exits the tube and moves back into the drum or pail, you absolutely know you have a leaking foot valve/lower ball. Again this is fairly easy to see on most pumps (try it, don’t be intimidated). A leaking valve does not always require a new valve. Sometime it can be as simple as a small piece of debris under the ball.
Again we have an easy test but it does require taking the foot valve off. If you have paint reentering your pail or drum your foot valve is leaking and it WILL need to be taken off so go ahead and remove it. Foot valves are threaded and usually tight meaning they can require a pipe wrench to remove. Simply clean the valve and ball and place the ball into the foot valve. Fill the foot valve with water and check for leakage. Remember the pump is operating at a very high pressure, a simple drip under only gravity will turn into free flow at high pressure. If even a small amount of water leaks, the valve and or ball will need to be replaced. You can try the same test with a new ball but we seldom find the ball to be bad and the foot valve good. We always recommend replacing the ball also if I replace the valve. A slightly out of round ball will cause undo wear on the new foot valve. If the ball and valve pass the drip test, you may have had something caught under the ball and only need to remove it. If you don’t visually find the foreign object, we have no test. You must return the foot valve to the machine and retest the down stroke, sorry.
If the pump stops on the down stroke and not the up stroke, the fix is more difficult. The pump must come apart. After the pump is apart, the same drip test can be performed on the piston valve. This test is more difficult however because on most pumps there is no way to simply place the ball in the valve and fill with water. There are too many different designs to go into detail but it often works to turn the valve upside down and place it on the ball and fill the valve from the backside. If it holds in one direction, it will normally hold in the other.
Now remember we wrote about two exceptions. The second exception is a restricted suction hose. If the hose will not allow enough paint to enter the pump, it will also not work properly. Keep in mind that a suction hose may look fine on the outside but have delaminated on the inside and be completely constricted. The test for this condition is even simpler than those for the pumps. Take the suction hose off the lower unit and place the lower unit directly in a pail of paint, making sure to completely cover the inlet. If the hose is constricted, the constriction is now removed and the pump will return to normal operation. You can either try and repair the hose or replace it. Sometimes with a constricted suction hose you will see your pump move normally through the up stroke and then quickly “jump” down before completing the remainder of the down stroke in a more normal fashion. In this case, the lower paint area has not filled completely with paint and the pump is not moving any material on the initial portion of the down stroke.
How to make your pump stop on UP and DOWN strokes:
The primary starting point for these tests is getting your pump shaft to stop and hold on the up and or down strokes. The best and most efficient way to perform this test is simple. Pump out of and back into the same container. This can be messy, so think through what you are doing before you do it. Some people choose to pump the paint onto a fence or even the base of a post. This removes much of the potential for making a mess but wastes the material. This is a personal choice. Whichever route you choose, start your pump and be sure to remove all the air from the system. You need to position yourself where you can see the lower unit operation. Use your painting gun to produce very short paint bursts with time enough between them to let the shaft come to a complete stop. This sound difficult but is actually very easy. Let’s consider the example of a bad foot valve. When the shaft is on the upward stroke, each short paint burst will result in the shaft moving upward a short distance and then coming to a complete stop. When the shaft reverses and starts down, it will proceed all the way down and start back up with no more bursts from the paint gun. The shaft may not stop immediately on the way up due to the reduction in pressure of the entire system during the down stroke. In extreme cases, the shaft may cycle and not stop on the entire up stroke. In this situation it is slightly more difficult but you can normally tell in which direction the pump is working well and in which direction it is not working. Of course all of these tests assume your pump has not deteriorated to the point it will not even pump up and hold any pressure. If this is the case you can still perform these test but will have to watch what is going on very carefully. Good luck.
We have been long winded but we hope it helps. If you are still stuck, call us and we will be more than happy to help.
Titan Hydra Pro IV Cylinder also known as the Sleeve
Titan Hydra Pro IV Foot Valve with Ball
Titan Hydra Pro IV Rod also known as the Shaft or Piston
Titan Hydra Pro IV Packing also known as Seals
Titan Hydra Pro IV Foot Valve and Ball with water for leak test
Titan Hydra Pro IV Piston Valve and Ball, screws onto Rod with Lower Packings