Why register? ...To Enhance Your Experience
+ Reply to Thread
Results 1 to 6 of 6
  1. #1
    Forum Member GTRider245's Avatar
    Join Date
    May 2005
    Location
    Augusta,GA
    Posts
    3,056

    Default 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!
    Career Firefighter
    Volunteer Captain

    -Professional in Either Role-

    Quote Originally Posted by Rescue101 View Post
    I don't mind fire rolling over my head. I just don't like it rolling UNDER my a**.


  2. #2
    MembersZone Subscriber
    Join Date
    Jan 2007
    Location
    Pa Wilds
    Posts
    581

    Default

    Trying to read between the lines as to pump manufacturer, volume & engine. This info would be helpful. Generally speaking, most volunteer departments do not work their pumps adequately. It is not unusual for relief valves to become sluggish or quit operating all together due to a lack of use. Having said this, there are a number of reasons why a relief doesn't function properly. First, does this engine have a pressure governor AND a pressure relief valve? The relief valve is supposed to be able to handle the entire pump volume, so it is doubtful that the pump volume could be too much for the relief to handle, but if the set point on the pressure governor was above the 140 psi, then you would have a war between the relief and the pressure governor. Second, if this is a Watrous pump, I would remove the screen from the pilot assembly and clean it along with making sure that the small orfice at the end of the shaft is not blocked. Run the pump pressure up to say 150 psi and set the relief at under 100 psi, then periodically turn the Watrous pilot valve off and on until the response from off (150)to fully open (under 100 set pt.) gets well under 10 seconds and preferably under 5 seconds to fully open and fully close. If it is a Hale, you will need to work the handle from a low point near 50 psi to a high above 200 psi. You will need to make sure there is at least 10 to 20 gpm flowing back to the tank or being discharged to the water source. If you are working with a large pump (1500 gpm +) circulating water back to the tank will result in significant heat being generated in the tank water. If you can touch the water (dribble some out a discharge to monitor temperature) it isn't a problem. Warmer than you can stand on a bare hand might be a problem if you introduce very cold (50 deg. or colder) water rapidly. Different metals and shrinkage cause stress in the pump and can cause major damage when a pump is rapidly cooled. A large single stage pump operating at 150 psi and up can heat a 300 gal tank to the uncomfortable point in less than 15 minutes. The uncomfortable point on a bare hand is about 110 deg. F. In the old days we were taught to monitor the steamer cap, but with current intake valving, it is better to dribble some out of a discharge at the panel to monitor the temp. Do not depend upon an over temp sensor. It is there to help if you get forgetful.
    Lastly, you did not say how high you got when you switched from volume to pressure. It is best to throttle down before making the switch, to minimize the slamming of internal pump check valves when you make the change. You might have created a pulse/peak that loosened the stuck relief valve, returning it to proper function. Try setting up your pump in pressure at 120 psi with the relief set above that pressure. Record the rpm needed to get the 120 psi. Turn the relief down to the minimum and record the relieving pressure when fully? open. Say 60 psi. Record the rpm & original pump pressure along with the relieving pressure. Operate the transfer valve from pressure to volume and record the pump pressure (should be around 60 if 120 in pressure) Return to pressure mode. Periodically check the pump and relief performance against this information to assure yourself that the transfer valve, pump condition and relief operation haven't changed since the last test. Reset your relief by raising the setting above the desired (140 set at 160 to 170) bring your pump pressure to 160 and lower the relief until the discharge drops to the desired 140 psi. If you are using a Watrous relief valve.... 1. lower rpm 2. turn off relief control switch 3. raise the pump rpm until the discharge reaches 150 psi +. 4. return engine to idle. 5. Take pump out of gear. Your relief valve is supposed to handle the pump in the volume position, but the relief might not be opening completely, so it dumps the lower volume in the pressure mode, but doesn't open suffiently to dump the volume in parallel setting.

  3. #3
    Forum Member FIREMECH1's Avatar
    Join Date
    Apr 2008
    Location
    HUSKER LAND
    Posts
    2,425

    Default

    Quote Originally Posted by GTRider245 View Post
    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!
    I'm going to hit the section I highlighted in red first. If you were in volume stage at 160psi, there is no way your pressure dropped to 50psi, even if the PRV opened after switching to pressure. Something isn't quite right (info/reading???)

    Setting the PRV in either volume or pressure is the same. It is when you switch from one to the other that can makes things VERY INTERESTING ..... REAL QUICK, if you have lines out.

    Several things could have caused the problem. Without knowing the pump man., I'll go through a couple. Blocked line to the valve on the discharge manifold, blocked line from the intake to PRV, or pump discharge to the PRV. If a waterous, a clogged screen or vent (end of removable screen) could also cause the problem.

    I need the pump manufacturer to be of more help.

    FM1
    I'm the one Fire and Rescue calls, when they need to be Rescued.

    Quote Originally Posted by EastKyFF
    "Firemens gets antsies. Theys wants to goes to fires. Sometimeses they haves to waits."

  4. #4
    Forum Member GTRider245's Avatar
    Join Date
    May 2005
    Location
    Augusta,GA
    Posts
    3,056

    Default

    Thanks guys. I should have provided more info.

    The engine is a 2004 E-One with a 2 stage 1250 GPM Waterous. Standard throttle and relief valve, no pressure governor.

    Let me see if I can clarify on the pressure drop deal. While the truck was in volume, I attempted to lower the relief pressure all the way down (handle would not turn any farther to the left). The PRV was showing open at 160 PSI at this time. Operated the transfer valve to pressure and immediately the pump pressure dropped to 50 PSI and the relief valve remained open. At this time I was able to raise the relief pressure to the desired 140 PSI and set it.

    I should add that throught the pump training the relief valve operated just fine in the pressure stage, and this was the only hiccup we encountered. I pulled the screen from the PRV and it looked clear. I will play with it some more tomorrow and see if I can't flush it out using KuhShise's advice.

    Thanks again fellas.
    Career Firefighter
    Volunteer Captain

    -Professional in Either Role-

    Quote Originally Posted by Rescue101 View Post
    I don't mind fire rolling over my head. I just don't like it rolling UNDER my a**.

  5. #5
    Forum Member FIREMECH1's Avatar
    Join Date
    Apr 2008
    Location
    HUSKER LAND
    Posts
    2,425

    Default

    Back flushing the PRV at 150psi with the screen removed does wonders for abnormal issues. A good blow gun blowing through the bottom side of the screen holder is a good idea as well. I have a trick for issues with it, but I can't post it up here.

    From the sounds of it, something became obstructed and with the switch of the PRV loosened it and blew it out. I have the guys go through the back flushing on their Saturday run-through list, as well as a good cleaning of the screen and filter.

    Good luck, hopefully you won't have any issues again.

    FM1
    I'm the one Fire and Rescue calls, when they need to be Rescued.

    Quote Originally Posted by EastKyFF
    "Firemens gets antsies. Theys wants to goes to fires. Sometimeses they haves to waits."

  6. #6
    MembersZone Subscriber
    Join Date
    Sep 2006
    Location
    Northeast Coast
    Posts
    3,820

    Default

    It sounds like the PRV was stuck and when you transferred from volume to pressure the pressure change on the spring allowed the relief valve to fully open, thus dropping the pressure to the lowest setting (you were hard to the left)? This may have "unstuck the PRV" allowing you to reset it properly. Our relief valves get worked daily with every pump check to ensure the spring is allowed to exercise. We also typically leave them just above our desired PDP for our primary 1.75" lines.

    Whoops, guess I should have continued reading before posting, looks like FireMech beat me to it.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. Replies: 30
    Last Post: 12-03-2010, 02:11 AM
  2. Hale pressure relief valve stuck
    By Catch22 in forum The Engineer
    Replies: 6
    Last Post: 12-16-2008, 09:07 PM
  3. Relief Valve
    By koziol41 in forum Firefighters Forum
    Replies: 1
    Last Post: 02-04-2003, 12:23 PM
  4. Pressure relief valves vs. pressure regulators
    By akjustin in forum The Engineer
    Replies: 4
    Last Post: 06-07-2002, 12:33 PM
  5. pressure govenors vs pressure relief valves
    By akjustin in forum Firefighters Forum
    Replies: 2
    Last Post: 05-24-2002, 12:14 PM

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts