This time of year, we get numerous calls with issues on guns locking up, crossing over and guns spraying for a few seconds before it just stops spraying. As the weather gets hotter, the gun cross-overs will increase.
REDUCE YOUR HOSE HEAT
Running your hose heaters at 130 and having the hose run across 200' of roof deck on a hot day makes the chemical too hot. In the southern regions, most roof decks are over 130 during the afternoon.If you start to spray and only work for a minute or two before the gun locks up - its not the seals, its your temperatures. We have done roof jobs with the heaters on 90 to spray.
You will also notice when you dis-assemble the gun that it is clean compared to what a normal cross over looks like inside.
How to test your chemicals to see if they're too hot: Remove the manifold assembly from the gun.
With the system pressure OFF and on JOG to circulate the fluid, open the "B" side shut off valve and pour 1/2oz into a paper cup. If the fluid begins to froth into a foam (like a beer from an empty keg) - reduce the heat.
You may need to recirculate the fluid to get all the hot chemical out of the hose and allow time for everything to cool down some. Set your heater at 100 - its much easier to heat up, than to cool down. If the chemical is not hot enough, the reaction time will be slow or the foam will be spongy. Increase the temperature another 5.
Chances are, if you're spraying on a steel building or a roof deck, the surface temperature you're spraying on is 110-150 and that will cause the foam to react anyway.