Thermal relief valve question

[1carwash1]

I’m rebuilding a pumping plant and replacing all the high pressure pumps. The rinse cycle is pressure fed and the high pressure soap and wax are gravity fed. How effective would it be to install thermal relief valves? I was thinking that they would be effective on the pressure fed cycle but would they be effective on the gravity fed high pressure functions? In the past, I have had an occasional tip clog but never had any damage to the pumps (General pumps) so I am wondering if thermal relief valves are even necessary? I’m also using pressure regulators not unloaders.

 

[MEP001]

The only time I've ever had a pump overheat with damage was with an attendant who kept leaving the washdown switches on. Other than that, it's never been a problem unless the bay hose freezes and a customer dumps a bunch of money in it and leaves it running. Once was my fault because I was in a hurry and changed a bay hose and didn't test it, came in the next day and the tip had gotten plugged.

I doubt a thermal relief valve will even be effective without water pressure behind it.

Are you running hot water on soap and wax?

 

[1carwash1]

The only time I've ever had a pump overheat with damage was with an attendant who kept leaving the washdown switches on. Other than that, it's never been a problem unless the bay hose freezes and a customer dumps a bunch of money in it and leaves it running. Once was my fault because I was in a hurry and changed a bay hose and didn't test it, came in the next day and the tip had gotten plugged.

I doubt a thermal relief valve will even be effective without water pressure behind it.

Are you running hot water on soap and wax?

Yes, hot water soap and wax. Why do you ask? Does it make a difference?
My previous plant was gravity fed for all functions and did not have thermal relief valves. Over the years, I had numerous plugged tips but never had any damage to the pumps (General).

 

[MEP001]

If you had cold everything, I would have recommended eliminating the rinse solenoids.

 

[1carwash1]

I spoke with Cat technical support. They recommended that instead of using a thermal relief valve it would be better to use a pressure relief valve. In the event a tip becomes clogged, the increase in pressure should open the pressure relief valve allowing cooler water to enter the pump. We run our pressure at 1100~1200psi. Which Cat Pop-Off pressure relief valve should we choose? The 300~1500psi or 1000~ 3000psi. Both seem to fall within our pressure setting? The top seller on KR’s website is the 1000~3000 pressure range.

 

[MEP001]

I'd go with the 300-1500 if I HAD TO use a pressure relief, but I never use them and never see them on car washes (I've worked on about 500 different car washes all across Texas), and when there are relief valves I often end up removing them because they're leaking. IMO if you plumb everything between the pump and boom with brass or stainless you shouldn't have an issue with clogged tips. I've been doing this for 41 years and haven't ever seen or known of anyone who had a tip plugging issue.

 

[John J Spokas]

I'd go with the 300-1500 if I HAD TO use a pressure relief, but I never use them and never see them on car washes (I've worked on about 500 different car washes all across Texas), and when there are relief valves I often end up removing them because they're leaking. IMO if you plumb everything between the pump and boom with brass or stainless you shouldn't have an issue with clogged tips. I've been doing this for 41 years and haven't ever seen or known of anyone who had a tip plugging issue.

This sounds strange.

 

[MEP001]

This sounds strange.

What does?

 

[Dan kamsickas]

I've been doing this for 41 years and haven't ever seen or known of anyone who had a tip plugging issue.

It's extremely common here in the great white north. Customers use the guns to pry the ice build up from their wheel wells and get crap stuck in the tip.

 

[John J Spokas]

What does?

Having a positive dispalcement pump set up with no pressure relief valve sounds strange to me.
Am I miss-understanding something in your post here?
I see this thread started out discussing temperature relief valves but in that last post you said you never use PR valves. On centrifugal pumps yes no problrem but on positive displacement pumps there is the potential for big problems.

 

[washnvac]

I use the thermal relief valves. Mostly because I have some CAT 623 pumps. When someone leaves that running without the trigger pulled, it heats up really quick. Within 60 seconds or so, it typically starts blowing out to bring in lower temp water. Both hot & cold are gravity fed.

 

[1carwash1]

The idea was to protect the pump in the event the tip became clogged. However, since I'm using regulators, I do not see the point in installing pressure relief valves. In the event a tip becomes clogged, the water will circulate through the regulator back to the pump inlet. There may or may not be an increase in pressure but the temperature of the water in the closed loop will increase. Hence, it may be more advantageous to install thermal relief valves. The problem I see with thermal relief valves is that if the system is gravity fed and the thermal relief valve opens will it suck in air or purge hot water. In my case, the rinse cycle is pressure fed so I'm quite certain that the thermal valve will purge heated water on the rinse cycle. However, my wash and wax cycle is gravity fed. In the latter case, how is the hot water ejected from the thermal relief valve?

 

[washnvac]

I use these:

General Pump 100556 Brass Thermal Protector - 1/4 Inch NPT, 90 Degree 1/4 Inch Hose Barb, 145 Degree F

 

[MEP001]

It's extremely common here in the great white north. Customers use the guns to pry the ice build up from their wheel wells and get crap stuck in the tip.

Then if he's in that area he definitely should use something to protect the pump. I've only seen it happen once, from someone prying mud from his fenders, and it didn't even completely plug the tip.

 

[Dan kamsickas]

Then if he's in that area he definitely should use something to protect the pump. I've only seen it happen once, from someone prying mud from his fenders, and it didn't even completely plug the tip.

Think of that mud frozen. Complete freaking mess. Cat makes a pop-off valve we pump into the pump just in case.

 

[1carwash1]

Think of that mud frozen. Complete freaking mess. Cat makes a pop-off valve we pump into the pump just in case.

If your Regulator is working properly why do you need a pop off valve(I assumed you are referencing a pressure relief valve)? The regulator will just bypass the water back to the pump inlet In the event of a clogged tip.

 

[Dan kamsickas]

If your Regulator is working properly why do you need a pop off valve(I assumed you are referencing a pressure relief valve)? The regulator will just bypass the water back to the pump inlet In the event of a clogged tip.

I've seen a plugged tip cause a freeze up into the equipment room fouling the unloader. A freeze up and a bay left running in bypass tends to overcook the pump. I've also seen unloaders fail. CAT calls is a pop off valve. It's their part number 30961. Cat recommends them as a secondary relief point for pump protection. They are not 100% needed but if we were to ship a piece of equipment and it blew from over pressure it would be bad on us.

 

[MEP001]

Melted pump from washdown switch left on (No plugged tip):



The low-pressure seals are melted to the seal retainers. The melted black stuff is the plastic cages of the valves. The grayish plastic bits were the valve backup rings. It takes a long time for it to get that hot, but it does happen.

 

[1carwash1]

What a mess, was the back end of the pump damaged? So what is the consensus here; pop-off valve, thermal valve, or both?

 

[MEP001]

I don't know if either would have saved the pump in my picture. The pop-off would not have done anything because the pressure it would have been set for would not have been reached. The bay had a weep gun and the tip wasn't clogged. I don't know if a thermal valve would have helped because the water was from a tank. It might have dribbled some water out, but it will take some testing to see if it would prevent damage.

I have one bay with an unloader on it because I wanted to see if customers would be confused by non-weep guns. I had considered using non-weep guns on all the bays but haven't gotten around to replumbing them all. If the tip in that bay ever gets plugged, the pump won't get hot.