- Thread starter Anguz
- Start date
daleyd
Member
- Messages
- 10,539
- Location
- Wrexham, North Wales
Do you want just a panel builder or someone to design the whole process for you? If you want someone to look at the whole thing, programming and design calcs etc it’s really a systems integrator job, but there is some overlap - some panel builders will do programming work etc, but some will just do the build side of things.
Do you have any preferences for controls? Stand-alone controller or plc - do you need hmi to view any process data and enter any settings? How big is the enclosure? Would you be programming any set up yourself, or would you need that doing as well?
Do you need CE(or whatever the uk equivalent is now) certificates?
How many panels are needed? If it’s a repeat job then you’ll pay once for the design work, which makes per panel costs cheaper. If it’s a job for yourself sticking some terminals in a small panel and mounting an instrument is pretty straightforward.
If you have a spec to work to I’ve used a company called smart controls in st Neots in the past, they are pretty good. But I don’t know about them doing programming etc, we’ve only used them for physical panel build.
I can help with pointing you in the right direction on the controls side of thing if you want, process control is my day job.
Agroshield
Member
- Messages
- 6,351
Are you currently measuring the flow of water? If so with what? The output of that process is the input to the oxygen doser so would need to be known by the doser designer. Similarly, a flow vs time graph would be essential.
What I am saying is that the an integrated solution might have to include control and measurement of the water flow as well as the oxygen dose.
What I am saying is that the an integrated solution might have to include control and measurement of the water flow as well as the oxygen dose.
Anguz
Forum Supporter
- Messages
- 1,976
- Location
- Northamptonshire
we are currently dosing it as a fixed flow of oxygen via 4 regulators, each one switching in via a solenoid as the flow increases.
we have a proper flowmeter for the water flow with 4-20ma output, and rotameters on each regulator
its worked like that for the last 30 years but our lot want a bit more exacting control
the electric side isnt a problem, we can do the plc control... just need to control the gas flow and have some feedback as to what its doing
we have a proper flowmeter for the water flow with 4-20ma output, and rotameters on each regulator
its worked like that for the last 30 years but our lot want a bit more exacting control
the electric side isnt a problem, we can do the plc control... just need to control the gas flow and have some feedback as to what its doing
daleyd
Member
- Messages
- 10,539
- Location
- Wrexham, North Wales
Depends how accurately you want it - I’ve done some work with mass flow meters to dose various chemicals/gases (anmmonia and nitrogen mainly, but I’ve done others as well) into furnaces. You send a 4-20 or 0-10v signal out (or do it via comms) and the flow meter gives a corresponding signal back of actual flow. I think you can get cheaper versions that aren’t as accurate as mass flow, but they might be “good enough” for what you want. As always it comes down to cost - mass flow meters are quite pricey but the savings in gas might mean that’s not an issue.
You can use the plc or whatever control you use to give an output according to the read in water flow signal. Either a simple proportional output or you can use a characterisation block, or whatever the equivalent is in your preferred brand of plc/control, to give more flexibility. With our stuff you can fairly easily do totals of the flow, if you wanted daily/weekly/monthly totals of gas used etc….
daleyd
Member
- Messages
- 10,539
- Location
- Wrexham, North Wales
Just looked back through some emails I had with our customer on this subject, they started off using Brooks instruments Mass Flow Controllers, but they had 2 fail in fairly short order (This was Ammonia for a nitriding furnace, so pretty corrosive stuff to be fair ) - they changed to a company called Bronkhorst (Which they use on their newer furnaces, the one I did was a retrofit to an old furnace, they supplied the mass flow controllers) and I've not heard any more for the last 12 months or more so assume they have been OK.
www.brooksinstrument.com
www.bronkhorst.com
Mass Flow Controllers | Thermal & Pressure-Based Meters
Brooks Instrument mass flow controllers and meters set the global industry standard for precise, accurate and repeatable mass flow control and measurement.
www.brooksinstrument.com
Our mass flow controllers
learn more about Bronkhorst mass flow controllers with different operating principles for gases and liquids. What suits your process?
www.bronkhorst.com
daleyd
Member
- Messages
- 10,539
- Location
- Wrexham, North Wales
No, you would need another sensor for that - mass flow is just an accurate dosing device, which I think is what the op wants. If you wanted to close the loop you could add a dissolved oxygen sensor I guess (I’m not a process engineer, so I don’t know if it would work), but from what I understand he just wants an accurate method of dosing.
If you want to have a closed loop then PID times can be tricky for dosing, I did one a few years back that went into an effluent stream and holding tanks - when you dosed the chemical it took 2 days for any effects to be measurable….might not be the case here of course
Erie Fred
Member
- Messages
- 6,315
- Location
- Erie, Pa USofA
That's what I thought.
And yes, full closed loop using some sort of dissolved O2 sensor to feedback to the PLC would
need to have some time interval in there.
However, O2 in water (if it's in a pipe) might prove a pretty fast feedback ?
Dosing water with oxygen is one thing, making sure that it dissolves properly, and consistently, is another, and will depend on the nature of the delivery point. Presumably it uses something that produces very fine bubbles. A dissolved oxygen sensor would be a good way of veryfing that the system is working as intended. Dissolved oxygen sensors will need to be replaced from time to time, based on my experience with them, plus some sort of maintenance/cleaning schedule for the oxygen permeable membrane. .
My experience is with chlorine gas into water, and similarly sulphur dioxide (used to knock back the chlorine after disinfection). So the process had a controller, a chlorine gas demand valve, a flow measuring indicator, flow meter for the water, a venturing and gas injector, and a gas controller. The bit you're interested in would be the gas controller?
Well forget all the mass flow stuff, what you have is a rotameter type flow meter/indicator ( pea in a tapered tube) connected to the vacuum demand valve. The demand valve was to keep the chlorine from oozing out, being that it's horrible stuff. Simply, the water flow through the injector draws a vacuum, the gas flows from a sight glass, v notch flow controller, and demand valve into the injector. The clever bit, if you like, was the stepper motor (used to be a DC motor) attached to a rack and pinion which was connected to the gas control v notch - chlorine demand goes up (as calculated from the flow and measured by a little chlorine cell), the rack would drive down a step, then wait for the loop time to see if was enough, rinse and repeat. Sounds complicated, but in practice all very simple to set up and fault find. The v notch gas control would be a simple plastic rod in a glanded hole, with a tapered v notch machined into it, in whatever shape and taper was needed, it would match the flow capability of the site glass.
If the water pipe was big, the injector would have some water teed off, pumped through the injector into a dosing point, thus getting the gas into the water. I once was presented with a problem that had existed for years and years, the chlorine cell would bounce from one end of the scale to the other, every 3 minutes or so. Everything I checked was correct, I went down to the basement to watch the water coming over the dosing sparge pipe - sure enough, bubbles every 3 minutes. Then I listened to the injector, same cadence to the sound.. The problem was the controller/gas flowmeter etc were upstairs, the injector, downstairs was syphoning. A simple loading valve solved the problem - Huw the hero!
Anyway, the company you want to ask is Wallace and Tiernan, they do all this stuff, whether they to it for oxy is another question. They are not cheap, given the stuff they cell is for water chlorination, and water companies. Dissolved oxy measuring cells are simple membrane and silver anode things, plenty about. A few years ago I could have given you all the bits for this, seen plenty going into skips.
Well forget all the mass flow stuff, what you have is a rotameter type flow meter/indicator ( pea in a tapered tube) connected to the vacuum demand valve. The demand valve was to keep the chlorine from oozing out, being that it's horrible stuff. Simply, the water flow through the injector draws a vacuum, the gas flows from a sight glass, v notch flow controller, and demand valve into the injector. The clever bit, if you like, was the stepper motor (used to be a DC motor) attached to a rack and pinion which was connected to the gas control v notch - chlorine demand goes up (as calculated from the flow and measured by a little chlorine cell), the rack would drive down a step, then wait for the loop time to see if was enough, rinse and repeat. Sounds complicated, but in practice all very simple to set up and fault find. The v notch gas control would be a simple plastic rod in a glanded hole, with a tapered v notch machined into it, in whatever shape and taper was needed, it would match the flow capability of the site glass.
If the water pipe was big, the injector would have some water teed off, pumped through the injector into a dosing point, thus getting the gas into the water. I once was presented with a problem that had existed for years and years, the chlorine cell would bounce from one end of the scale to the other, every 3 minutes or so. Everything I checked was correct, I went down to the basement to watch the water coming over the dosing sparge pipe - sure enough, bubbles every 3 minutes. Then I listened to the injector, same cadence to the sound.. The problem was the controller/gas flowmeter etc were upstairs, the injector, downstairs was syphoning. A simple loading valve solved the problem - Huw the hero!
Anyway, the company you want to ask is Wallace and Tiernan, they do all this stuff, whether they to it for oxy is another question. They are not cheap, given the stuff they cell is for water chlorination, and water companies. Dissolved oxy measuring cells are simple membrane and silver anode things, plenty about. A few years ago I could have given you all the bits for this, seen plenty going into skips.
Xylem Water Solutions & Water Technology | Xylem UK
Xylem is a leader in developing innovative water solutions through smart technology. Learn more about Xylem's water, wastewater and energy solutions.
www.xylem.com
