By: Dave H

Video Transcript

Hi, my name is Dave and today we are going to talk about the two types of dual-pressure hydraulic systems that we mount on our vehicles today. One involves the Gemini pump and the other involves the D-182 combo valve, both are very good systems, and both are sold and serviced here at Parts for Trucks. Pay attention to the video and let’s see which one of these is right for you.

A lot of calls come in from our customers as to exactly how to do this, how do we get a system on a truck that can handle both the low- and high-pressure system, that is what we’re going to talk about here today. There are a couple of ways to do that, I am just going to mention the ones that we sell and service here Parts for Trucks. 

The first system we are going to talk about is the Gemini, this is the Gemini pump made by Permco, this pump has a relief valve on the back that is capable of two different relief settings. The problem that we have in the industry is when these come in from the field, is just how they are identified, this is the regular dump pump, it has been around for generations, I believe back in the 60s that this pump has changed very little in its outward appearance and this pump is almost a copy of it, this is the difference. Make sure that if your customers are coming in with a Gemini pump, you replace it with a Gemini pump. Sometimes those mistakes can be made, we want to make sure we avoid that by covering some of these issues here today.

This pump has two relief settings, how do we adjust them? Right here, this jam nut here is backed off and the cylinder is rotated clockwise to increase the pressure setting, and counterclockwise to decrease the pressure setting. This jam nut, when loosened allows us to perform the same rotary functions here on the cylinder to both increase and decrease the pressure. So again, clockwise will increase the pressure setting while counterclockwise will decrease it. It is important to note that when you are adjusting the low setting, the high setting will flex from it, so it comes set from the factory at 2500 PSI and 3,200 PSI. If you would adjust this, know that your high-pressure setting is still going to maintain that 700 PSI differential. It’s best to set up your system by setting this one first because when you set your high pressure setting it will be independent of whatever the low one was.

We have here on the Gemini, unlike the dump pump, an inlet on the side, this inlet is larger than we are used to seeing and we should be running a minimum 1.5-inch if not a 2-inch line to this port. Again, these higher requirements of the walking floor and live bottom trailer need that flow of oil and the way to do it is to make sure that that suction line is about a two-inch diameter. That would be perfect, that is what I would put on my own vehicles. In terms of plumbing this is very much like your dump pump in terms of how It is plumbed. We have our inlet which is normally here, and inside here is where the third line sleeve is to maintain flow of oil when this is in the relief mode. Our inlet in, and the line at the bottom here, this is our pressure line out to our trailer to operate our walking floor or belt trailer. When the line comes back, it comes back to the pump into the return here, and then back to reservoir. Other than that, it’s very much like a dump pump don’t get them mixed up, there’s a big difference in the pressure requirements and people can get hurt or equipment can be damaged, so important to know when you’re looking for the Gemini look for that cylinder on the back. 

Okay so here Parts for Trucks, we have heard from customers that would like to have a system that has those two relief pressures, but they don’t have room for the bulky Gemini pump, how do we do that? Several ways, we need something in the system that we call the combo valve, this valve made by Hydrocar, is sold under many different part numbers by many different distributors but I will just say that it’s a Hydrocar dual-pressure relief valve that has a built-in tipping feature. It allows you to run your end dump trailers while at the same time, allows you to have the higher relief pressure needed for your walking floor or your live bottom trailer. When I say that we do not have room for the Gemini pump, that opens up to other options that are out there for pumps. The one that I am going to talk about that you might see out there is this one right here, this is the P 5100 style pump from Permco. It again, has its signature four bolt inlet that is 2-in and what that does is again, guarantees the flow of oil at the pump for these high-volume applications like the walking floor. You are looking for 45 gallons a minute on some of these applications you’re going to need that 2-inch inlet, not the inch and a quarter one you are used to using in your dump systems. 

So, when we have this pump, it’s connected to the PTO obviously, we’ve got the pressure line that comes out and goes into here, and this is the ability right here in the system to adjust your pressures. So, what we have is our line in, this is our pressure line in, and it will continue on and out to the back of the trailer. What happens then is the pressure in that line is adjusted to the relief function of this valve back here which is an air valve. You’ll notice on the back, this is our fitting in so this will come from the line in the dash the actuator for high and low when it’s depressed this is where that line goes. The system works two ways, there’s a high and low pressure setting that’s adjustable, to adjust the low side of the pressure setting we release the acorn nut on the back here, this is where the low-pressure setting is adjusted. Again, we’re going to back off the jam nut and then follow the old industry terms righty-tighty, lefty-loosey to adjust your pressure either up or down. This cylinder on the back here, is for adjusting the high side, and what we have here are wax plugs, the wax plugs have to be melted and then inside is a set screw, when the set screws are loosened, it allows you to turn this whole cylinder, so again we want to tighten the cylinder clockwise what that’s going to do is that’s going to increase the pressure in the system. If we loosen up, counterclockwise we’re going to lower that pressure setting, again we’ve got our gauge hooked up so that we’ve got a visual indication of what we’re doing here matches with here, so no one is in danger. 

The other two ports to mention on this particular valve are right here, this valve is also the tipping valve for your trailer, so what happens is this is your raise function, and this is the lower function, this will run to the hoist control lever that’s up in the cab so that when you’re running your dump trailer, you can operate it using this and not a dump pump. 

With our dual-pressure systems at Parts for Trucks, we have a console that we like to use and that’s this one here, the housing is angled in such a way that allows us to place this between the seat in the door for the driver so it’s right there by his heel and the shift lever points towards the firewall which allows for the air seat to come down without breaking the valve, so a good system to use. 

You can have this system many ways, we keep the top plate here open so it allows us to use, for this case we’re talking about here today with the dual-pressure valve that can be mounted in there so that you’ve got your dual-pressure system, which is actuated by the push-pull, it goes to your cylinder, allows for the higher pressure, it’s installed right here, when it’s no longer in use it takes the lower pressure setting back so that there’s still some safety there, no danger of anybody getting hurt from accidentally using high-pressure system when only the low is needed.

We can then use a pump like this one here so we are looking at tandem hydraulic pump and we use these for log loaders in the area, we can then use this system to work with tipping valves to allow us to run both a log loader and an end dump trailer at the same time. So, what would happen is we have a relief valve that we’re going to run from, say our first pressure port so we can protect your tractor to make sure that it’s not going to bust a line and injured people. The second port would go through this valve, when we actuate this valve to the higher pressure setting, that would allow us to run the two lines back to the trailer to operate a log loader. When the log loader was not needed, what we could then do is take the line that was going through a relief valve and couple that directly back to the reservoir and then we’re running one pressure line through this valve which we now know has a single acting cylinder spool in there to make the box go up or down. 

So, thanks for watching our video here today, and if you have any questions or would like to find out more about what hydraulic system might be right for your vehicle, contact us at any one of our Parts for Trucks branches or get a hold of us at