Bootlegger
New member
So my day job is selling high-precision instrumentation, which is a big part of why I'm drawn to this "hobby". If one of my pharmaceutical or petrochemical customers was trying meter out CO2 from gas cylinders the last thing I'd sell them is a cheap regulator set with a manual control needle valve. What I'd propose, and often sell to them, is a mass-flow controller.
Why?
There are too many factors that can adversely affect flow rate, which anyone who runs a reactor knows. For example, temperature changes lead to pressure changes, which in turn change your bubble rate. Also, the small, restrictive orifices on needle valves can clog form dirty gas, which makes fine tuning nearly impossible over time. And, worst of all, it's not like we size anything right. In reality, the common gauge sets we use aren't really for the kind of ultra-low flows we run. They're way over-sized and, as such, we're asking a lot of a needle valve, which is also over sized. We lose quite a bit of resolution this way.
Circling back, I'd sell my customers properly sized a mass-flow controller. A mass-flow controller is a flow-meter with integrated needle valve. The meter side measures incoming flow while the valve side controls the outgoing flow. As long as the mass-flow controller is sized right, it can automatically control flow rates with ultra-high precision, even when pressure changes (within limits of course).
The kind of mass-flow controller we'd want in this hobby, other than <$200, is one with an integrated display and controls. The idea here is you can program the flow rate you think you need and then dial it in over time. Also, most of these controllers have 0-5V and 0-10V inputs for using external control devices, though I don't see this being necessary.
Here are a couple of controllers available on Ebay:
http://www.ebay.com/itm/AALBORG-MAS...566?pt=LH_DefaultDomain_0&hash=item35edbd670e
http://www.ebay.com/itm/ALICAT-SCIE...242?pt=LH_DefaultDomain_0&hash=item1a0311939a
If I could figure out how to make one that can be build and sold for $200 (with ample margin of course) I'd be the first to do it. Unfortunately, there's a lot of technology that goes into these mass-flow controllers. Most of the controllers I sell start around $1000 new and go much higher from there, depending on needs.
Why?
There are too many factors that can adversely affect flow rate, which anyone who runs a reactor knows. For example, temperature changes lead to pressure changes, which in turn change your bubble rate. Also, the small, restrictive orifices on needle valves can clog form dirty gas, which makes fine tuning nearly impossible over time. And, worst of all, it's not like we size anything right. In reality, the common gauge sets we use aren't really for the kind of ultra-low flows we run. They're way over-sized and, as such, we're asking a lot of a needle valve, which is also over sized. We lose quite a bit of resolution this way.
Circling back, I'd sell my customers properly sized a mass-flow controller. A mass-flow controller is a flow-meter with integrated needle valve. The meter side measures incoming flow while the valve side controls the outgoing flow. As long as the mass-flow controller is sized right, it can automatically control flow rates with ultra-high precision, even when pressure changes (within limits of course).
The kind of mass-flow controller we'd want in this hobby, other than <$200, is one with an integrated display and controls. The idea here is you can program the flow rate you think you need and then dial it in over time. Also, most of these controllers have 0-5V and 0-10V inputs for using external control devices, though I don't see this being necessary.
Here are a couple of controllers available on Ebay:
http://www.ebay.com/itm/AALBORG-MAS...566?pt=LH_DefaultDomain_0&hash=item35edbd670e
http://www.ebay.com/itm/ALICAT-SCIE...242?pt=LH_DefaultDomain_0&hash=item1a0311939a
If I could figure out how to make one that can be build and sold for $200 (with ample margin of course) I'd be the first to do it. Unfortunately, there's a lot of technology that goes into these mass-flow controllers. Most of the controllers I sell start around $1000 new and go much higher from there, depending on needs.
