What is flow capacity limiter of SF-110/120 design?

[BradH]

Regardless of whether the 110v or 220v model, the capacity limit listed for SuperFlow's 110/120 model is ~185 CFM @ 10" H2O. What I'd like help with is identifying what aspect of this type of bench establishes that limit.

The orifices on the top of the bench are of the following size & rated range for 10" H20:
1. .75" = 10
2. 1.00" = 18
3. 1.50" = 30
4. 1.75" = 45
5. 2.00" = 80
-----------------
Total --> 183

The ID of the intake flow controller orifice is approx. 2.35". With the effective diameter reverse-engineered by then subtracting the area of the shaft that the flow controller valve is mounted on, it's about 2.30".

The standard motor that comes w/ the 110v 15A model is rated at 82 CFM @ 23.4" pulling 6.5A through a 1.125" orifice, which I'm interpreting as being pretty close to 1/2 the max capacity of 160 CFM at 10" H2O... so the Delta P for the SF-110/120 design looks to me to be in the 13"-14" H2O range.

If I upgraded the bench to support 20A (still a 110v config) and installed new intake motors for higher CFM at more test pressure w/ the additional amps available, where is the "cork" in the design as described? And, therefore, what would be required to actually see the benefits of those higher-capacity motors?
a) Add another 2.00" orifice to the top plate
b) Increase the diameter of the flow controller orifice to larger ID, such as an effective diameter (net of lost area for flow controller valve shaft) of 2.60" and make a new flow controller valve to match
c) Both
d) None of the above because somehow I've overlooked something else in this equation

Yeah, I know there are other issues w/ upgrading a SF-110/120, but knowing this would be the first step in coming up w/ an upgrade plan.

Thanks,
Brad

[BradH]

All you people with "real" flow benches are either laughing at this or scratching your heads, right?

And I think I'm near clueless on what the actual Delta P is with this style bench and am grasping for a pseudo-answer by trying to back into it from the motors specs.

[RACEPUMPER]

Not laughing at all, just following, I don't have an answer yet, but theres not much room inside a 110. I'm doing a 110 at the moment too.

http://www.flowbenchtech.com/forum/view ... f=8&t=1157

Jim

[Brucepts]

The Delta P is going to be the rise of your incline manometer, that is what sets the Dp over your orifice plates. So knowing the inside flow control hole diameter, + your test pressure, + your Dp you can figureout the amount of pressure going through your flowbench.

Take for instance the total pressure on a PTS design is 28" test pressure Dp 16" for a total of 44" the motors have to generate and move through the flowbench, so all the passages have to be large enough to flow 600cfm @44". So the flow control valves on the 110 would need to be able to flow the test pressure + the Dp. The Incline looks to be about 4"? So rough figures your total would be 10" test pressure plus 4" Dp for a total of 14", so the flow control hole would need to flow XXX cfm at 14" this would be based on it's Coefficient of Discharge (Cd) of which we have no clue.

One problem you have on the 110 design is the closeness of the orifice holes and opening multiple holes that close to each other is going to have an effect on the orifice Cd so each hole by itself will not be flowing the same Cd once the hole next to it is opened and starts flowing air. You are going to have a reduced cfm total as the holes will be fighting each other for flow.

[BradH]

The incline manometer rise is only about 2"when measuring from the top of the fluid level to the bottom of the incline (with the current amount of fluid in mine).

FWIW, anyone know the diam. of a SF-600 flow controller opening? I re-measured my 110's at 2.3".

[larrycavan]

I would think if you look at your orifice combo specs and do some number crunching with Ed's spreadsheet, you should be able to calculate any variance in orifice coefficient that may happen as the result of unplugging / plugging the orifices to change flow ranges.

The static goes to 15" so you do have the option to flow that high. The problem generally is that when you put a high flowing head on those benches you struggle to pull static pressure and have to drop down to 3" of static and convert your CFM.

Now....that stated, upgrading your motors may help in that regard.

Also take note that some years ago I had a discussion with a very, very knowledgeable person from Superflow and was informed that the 110 had some manufacturing variations of the orifice plate over the years. Some were stamped holes and some were machined....

It's a good little bench....little is the problem...as you're well aware of.

Also take note that you can extend the range by changing to the blue fluid. That's what they did when the went from the 300 to the 600 without having to increase the orifice sizes in the bench. So with that alone in mind, you can calculate the new range values as well.

All that aside...if you need to move a lot more air, you're better off with a bigger bench.

[BradH]

OK, "budget" update in progress:
- Switching from original Ametek 116297-00 intake motors to 119419-00
- Switching from .826 s.g. red gage fluid to 1.91 s.g. blue fluid
- Re-wiring the bench to support a higher 20A power source (standard is 15A), then route the "juice" through a Variac w/ 0-130V 20A output to support the higher amp requirements of the 119419-00 motors

Question: What's a good approach to making a larger intake flow control valve? My rough calcs have the standard 2.30" ID (less area of .25" shaft that the valve mounts on) maxing out around 210 CFM @ 10" H20. I think the size needs to be more like 2.60" ID to match the increased flow capacity of the new intake motors.

Pics attached show the same size exhaust valve from someone else's bench from both the plenum-side and motor-side views, to give some context around the work area. Thanks. - Brad

[BradH]

Also attaching the data sheets for the original 116297 SF-110 int/exh motors and the replacement 119419 intake motors. For the intended application, increased amp supply, and expected test pressure ranges, the specs show the 119419 "should" be able to move a lot more CFM at higher pressure than the original-fitment motors... enough that I expect the current intake flow control valve size will act as a restrictor of the max flow capability.

[Brucepts]

Question: What's a good approach to making a larger intake flow control valve? My rough calcs have the standard 2.30" ID (less area of .25" shaft that the valve mounts on) maxing out around 210 CFM @ 10" H20. I think the size needs to be more like 2.60" ID to match the increased flow capacity of the new intake motors.

I would think you would have to machine something to replace what is now installed. More than likely you would have to remove the one there now and swap it with the new one you made?

[1960FL]

Brad,

Switching from .826 s.g. red gage fluid to 1.91 s.g. blue fluid

Remember by doing this yes you up'ed the max scale in inches H20 but you also cut your resolution by 57% so your new scale will have to have even finer markings and your eye will need to be keen. Example in water at 2.5 inch orifice at 10" is like 267 CFM, at 5" it is 189.5, now at 5 1/16' or .0625 more I/E 5.0625" is 190.7CFM or roughly 1.2CFM more but with a reduction in resolution that 1/16" in scale now equals more like 1/9" or 191.7 CFM. so with a 2.5 equivalent orifice at mid DP of 5" with the 1.91SG fluid your resolution at 1/16" increment will be about 2 CFM. There is nothing wrong with this but at the scale decreases below the 50% DP range this multiplies so at 1/4 scale or 2.5" of DP the resolution at 1/16 increment is now 4+ CFM.

Just food for thought.

Rick