What happened to the averaging pitot

[Old Grey]

Back in 2008 when I was look at making a flow bench, the hottest item was the new averaging pitot - that everyone was raving about, and even Bruce had one - then I read this

http://www.flowbenchtech.com/forum/view ... ?f=4&t=255

and Bruce said this below.

I for one have made the switch from pitot to orifice style

I am so happy I made the switch that I no longer offer pitot flow elements for sale anymore! Nor can I even understand why anyone would go that route in my opinion?

A pitot bench needs to many flow elements to cover a range of CFM compared to an orifice style flowbench.

Tony has already pointed out quite a few more differences and positives. The design of an orifice bench is also simpler, my PTS orifice style flowbench has one moving part (slider plate for direction change) and it has no effect on the bench accuracy as it's after the testing orifice plate.

I have sold in the past more than a couple of flow elements and averaging pitot tubes and feel bad about it now knowing what I do now using my orifice style flowbench. I have helped a few of those customers over to an orifice style flowbench out of "guilt" and so I can sleep better at night

Does anyone know the specifics why he changed his mind, or any post that tell us why?

[Brucepts]

That quote pretty much says it all

I swapped over when I designed the new PTS Orifice Style flowbench, was simply easier to build and use. Range changes are way easier! Swap out an orifice plate as apposed to changing out a flow element. Plates from me are $30 how much is a flow element from the "other" vendors?

Look at the cost of a flow element style flowbench from the "other" vendor? A bench that uses 1 shop vac for $1000?

Ease of construction? A PTS orifice bench can be built in a garage using simple hand tools and some sweat. Sure you could assemble some expensive PVC pipe pieces sourced from another vendor, heck it's nothing to make a flow element to be honest. Don't be fooled into thinking you need a +$300 flow element.

I was selling the averaging tubes that you could install in a PVC pipe for $30 and it would work with the FP1 manometer. I stopped making them because of split/parting of ways with the "other vendor", the demand for the PTS parts and the design of the PTS DM.

We have talked about making the software change to use the PTS DM for a flow element style flowbench, actually just had this conversation again on Friday! But, there just isn't that big of a market for it once people consider the PTS Orifice style flowbench.

I could probably sell the same "flow element kit" using a shop vac with a PTS DM for around $500. But, I'd have a hard time actually thinking people would be getting a good quality flowbench. It would simply be a different level of flowbench. Nice thing would be the upgrade potential when you out grow the flow element, simply build an orifice style cabinet toss the flow element (which you would not feel bad about as it would not have cost you +$300 for some PVC pipe) and then you would have a real professional quality flowbench and not a bunch of expensive PVC

I have a past with other flowbench vendors so I'm kinda biased now! I have the only forum where you can discuss other flowbench products and actually get support for other vendor's products. You don't have to go to someone else's forum to get support for PTS Products

[Brucepts]

Sorry my reply went off on a tangent . . .

[Old Grey]

That's ok.

I just wanted to know if it was an accuracy problem, but now it seams like a cost problem.

[Tony]

That's ok.

I just wanted to know if it was an accuracy problem, but now it seams like a cost problem.

There is a lot more to it than that.

Every pitot measurement needs to have correction factors applied before a useful flow number emerges.
That is a complicated procedure, requiring readouts from a weather station, and if it is not done with rigorous precision, the final calculated flow numbers will be neither accurate or repeatable.

For instance, you measure the flow of a port during a hot summers day, do some work on it, and remeasure it at frosty dawn, when the measurement conditions are very different.
It can be very difficult to pin down a very small change when the final number is so critically dependent on all the applied corrections.

And it is being able to reliably and consistently measure very small changes we are really looking for.

Now an orifice bench just compares the pressure drops through what you are measuring with the pressure drop through a known reference orifice plate. Exactly the same air flows through both, so no correction factors are required.
Hot or cold the RELATIVE pressure drops will always remain exactly the same regardless of the air "quality".

The whole thing is very simple and easy to apply, and that simplicity pays huge dividends in both accuracy and repeatability.

I can think of quite a few original pitot bench users that have moved over to an orifice bench, and been delighted with the change.
I have never heard of anyone ever going the other way.

[Old Grey]

Thanks for that.

The accuracy and repeatability is really the only thing I am looking for.