Pressure Relief Valve Operation in Volume Stage
While doing some training with a new driver tonight, I came across an issue I had never seen or heard of before. We had just flowed the deck gun and shut the truck down to pick up hose as the drill was over. Once everything was good to go we put the truck back in gear to check for prime, water level and everything else you do after a driver as a driver before taking the truck back to quarters.
We run with the pressure relief valve set at 140 PSI and on all the time, as this is our predetermined pressure for our 200' 1 3/4" speedlays. As I attempted to set the relief valve I noticed it was not adjusting down below around 160 PSI or so. Cranked the handle all the way to the left and the relief valve remained open at 160 PSI.
At this time I realized the pump was still in the volume stage and switched it back to pressure. As soon as I did this the pressure dropped to 50 PSI and I was able to set the relief valve back to 140 PSI.
I have honestly never attempted to set the relief valve in the volume stage, being as 90 percent of our pumping, whether it be during training or on a scene, is done in the pressure stage initially, and then swapped to volume as the need arises.
So, has anyone else experienced this or have any explanation as to why this happened? Any info is greatly appreciated!