PTS Flowbench Forum

So I understand the 28+16 stuff ( which is the total draw across both gauges measuring test (static?) pressure and make DP of the measuring orfice which is also helpful for deciding on proper motor sizes and quantity ) and from reading the DM is a 40" ( actually 36" ) DM. Now there are 3 sensors in the box 1. Sensor I am guessing is the 40" sensor used to measure the static or test pressure on the object being tested 2. Is the 16" sensor used for measuring the DP for cfm calculations with the office plate and 3. No idea what size but it's used for measuring the DP across a pitot tube to calculate velocity. I am guessing it' probably a 40" or bigger maybe 100" sensor ( fps= (Sqroot of pitot DP ) * 66.2 so 40" on pitot manometer = sqft of 40" (6.3245) * 66.2 = 418.68 fps ) ) all " numbers are WC I assume this is understood ).
So I have read where some people flow LS head especially at higher numbers ( more than 28" ) so correct me if I am wrong but as long as you have a large enough orfice plate inside the bench ( so you don't exceed the cfm rating at 16" of the internal orfice plate ) then you can test flow the heads upto 36" on the static gauge ( as this number has been stated to be the highest you should actually run the sensor up to ) so you can see the higher pressure turbulence issues some LS heads have been found to have. This can all be done with the standard PTS bench build and the standard 4 plates offered by Bruce and using the PTS digital manometer box correct?

Please correct me if I have misunderstood any of this as I am currently in the preparing to purchase and build stage and want to make sure I build this thing to meet current and possible future needs.


Thank you
I look forward to my build and being a part of the PTS group.

You have it correct.

40" static sensor (up to 36" test pressure)

16" differential pressure (cfm reading up to -25cfm from testing plate, so a 300 plate would allow 275cfm) Plates I sell for a flowbench build take this into consideration.

100" sensor for velocity reading so, no worry over pressuring that sensor

Bruce,
Thanks for the reply.

So when I test at a higher static say 36" I need to make sure that the internal orfice plate is over sized or won't exceed the cfm of that plate ( based on the 16" measurements ) as that could cause the internal orfice plate sensor to possibly be damaged correct?
Usually you use a plate that is close to your max but with the digital gauges you can get away with a bigger plate but it's still best practice to use a plate close to the max flow you project.
But with the higher static test pressure you need a bigger plate correct so you don't damage the internal plate sensor?

Just trying to understand what, why and how all this is done.

Thanks for all the info on this forum and the plans.

If you run at a higher test pressure, what you are testing is going to flow more air....

So you are quite right, that needs to be taken into account when selecting a suitable orifice plate.

Thanks for the replies.
I thought I understood it correctly just wanted to make sure.

Thanks again.