Question on return filter plumbing

[Texasmark]

Question is this: On the return (to the fluid storage tank) filter in a hydraulic system, I want to add a pressure gauge to tell me when the filter is dirty to the point where the return pressure may get up to a couple hundred psig.

I have the Northern tool return filter assembly and it has a clearly marked 3/4" NPTF inlet and outlet. In addition, at 90 degrees from both are two 1/8" NPTF ports plugged from the mfgr. I called them and no help.

I Have a clean system right now and the cylinder is not attached. With cycling volume at 16 (pump rating) or less gpm, the pressure on both is around 5-10 psig, just enough to register on a 200 psig gauge.

When I cycle the control lever, with no outputs connected as stated, the pressure drops to 0 for the second I hold the valve in the work position.

If I plumb my gauge into either of these will it tell me when I have a clogged filter, or do I have to plumb a tee in the input to the filter from 3/4" down to 1/8" NPT to have that luxury?

Thanks for your time and inputs.

Mark

 

[BukitCase]

The Q&A section on that filter says it has an internal bypass set @ 15 psi. Nothing mentioned about the two 1/4" ports though - you might be able to see where they go by removing one, spinning off the filter, and seeing where air comes out when you blow into the port -

Looking at the casting, they may BOTH be connected to the same 3/4" port; hard to tell... Steve

 

[J_J]

You should be able to plumb a small gage into the side of the filter. Just adapt it down.

Valley Instrument Grade B Back Mount 2in. Dry Gauge — 0-30 PSI | Dry Gauges| Northern Tool + Equipment

 

[Texasmark]

into the side of the filter.

Side of the filter or filter housing?

Thanks,
Mark

 

[Texasmark]

The Q&A section on that filter says it has an internal bypass set @ 15 psi. Nothing mentioned about the two 1/4" ports though - you might be able to see where they go by removing one, spinning off the filter, and seeing where air comes out when you blow into the port -

Looking at the casting, they may BOTH be connected to the same 3/4" port; hard to tell... Steve

Well the 15 psig bypass will solve the pressure spike problem and that is good info.

I didn't know if the ports were common, a means to mfgr. the housing, ports for adjusting things like relief valves, or places to put a pressure monitor.

I attempted to differentiate between the ports by trying to isolate flow from the work part of the system and gravity flow from the tank feeding back. I was unable to determine for sure that they were port sensitive or just as you said connected to the main line.

Since I was able to see the gauge change with no flow from the control valves (in the operate position) in both ports, I think as you say it is connected to a common rail.

I think the gauge in either port will satisfy my curiosity.

Thanks,
Mark

 

[J_J]

Filter housing of course. I just think of the whole thing as a filter.

 

[Texasmark]

Filter housing of course. I just think of the whole thing as a filter.

I figured that's what you meant. But you could have meant something else and if you did, I was curious to learn just what that was.....part of my learning something every day.

Thanks,
Mark

 

[hydriv]

Well the 15 psig bypass will solve the pressure spike problem and that is good info.

I didn't know if the ports were common, a means to mfgr. the housing, ports for adjusting things like relief valves, or places to put a pressure monitor.

I attempted to differentiate between the ports by trying to isolate flow from the work part of the system and gravity flow from the tank feeding back. I was unable to determine for sure that they were port sensitive or just as you said connected to the main line.

Since I was able to see the gauge change with no flow from the control valves (in the operate position) in both ports, I think as you say it is connected to a common rail.

I think the gauge in either port will satisfy my curiosity.

Thanks,
Mark

If the Inlet port has a 1/8 inch port next to it and the Outlet port also has a 1/8" port next to it, then I doubt that they are connected. It is easy to check. Remove both plugs and also the spin-on filter cartridge. Use a blow gun to inject 90 PSi of compressed air into the small port on the Inlet side and put your finger in front of the port on the Outlet side.

If you do not feel any air flow, then they are separate. You want your gauge to be on the Inlet port because you are trying to observe resistance to oil flow caused by a partially plugged filter. This gauge should be checked when the engine is running at full throttle so that the filter is receiving all the flow the pump is capable of putting out. Having a second gauge in the Out port will show the difference between in incoming and outgoing pressures. If both gauges are reading high, then the problem is most likely with another part of the system between the filter and the reservoir.

But if the gauge on the IN port reads high but the gauge on the Out port reads low, then the restriction is in the spin-on filter.

 

[buickanddeere]

The two 1/4"ports are for a delta P gauge to monitor filter restriction if the filter discharge pipe work is above atmospheric pressure.

 

[Texasmark]

The two 1/4"ports are for a delta P gauge to monitor filter restriction if the filter discharge pipe work is above atmospheric pressure.

You mean a Manometer? Makes sense and answers the similar readings I got when trying to determine if each was connected to one of the main ports. Course knowing the filter has a 15 psig bypass answers my question.

Thanks,
Mark