To try geting this thread back on track,
I don't see where cavitation has any bearing on safety (this threas is in the safety section) as related our uses.
The "little blue HF pump" is just not a good choice for a processing pump, doesn't mean you can't use it with success, as long as you're aware of the pitfalls. I'm sure the same goes for other pumps intended to pump water.
Among the main problems seems to be an unattended process. Unless you have multiple safety measures in place (and even then) leaving the process unattended can be catastrophic.
Having electrical devcices on a timer, an ABC fire extinguisher readily available, attending your Process, using steel piping, secondary containment, and a dedicated building (you can afford to loose) will dramatically reduce the suffering of a fire.
It does not matter what pump you use, they all have pitfalls that have to be considered. For instance gear pumps are not tolerant of trash and grit. It tends to lock them up. With any positive displacement pump, if you shut off a valve in the output, the pressure will build up until something breaks. You can't just purchase a pump, throw it in and expect it to work flawlessly. Sorry, but there is no magic bullet.
Right on all counts Rick except I think the magic bullet is scraping the pump altogether.
Like everybody else I guess looked at the price of the real deal pump and freaked. If I could afford to buy pumps like that I probably wouldn't be making bio. I will admit I probably would have used a water pump at one stage, but could only find plastic and alloy pumps at the time.
I made a simple mixer out of some threaded rod a length of stainless pipe a hacksaw blade some bushes and pipe fittings and an old 12v motor. It fits through the top 3/4" port.
I won't say it mixes better than a pump but it is cheaper, less than 20 bucks if you have a motor. More importantly I think it is inherently safer. An old fridge compressor to suck the oil in and blow the bio out and you don't need a pump at all.
It worked fine until the motor burnt out and I fitted a geared down drive which doesn't mix as well.
I do a 2 stage base reaction and mix for an hour, 2 hours since the motor change and it passes a 3/27.
As far as pump pressures it really depends upon what is specified, if I specify a pump to move say 10000 litres per hour of soybean oil at 100C and need a head of say 50 metres I can pretty much guarantee that the pump vendor will supply me a quotation for a pump which includes a perfromance curve where my duty will fall (hopefully somewhere near the BEP). If not then the vendor is not doing his job and will not sell many pumps. In practise pumps are supplied to ISO or ANSI standards and as such what is shown on the curve is pretty much how the pump will perform. So in the above example I know that I can take a reading on the pressure gauge on the outlet of the pump and refer it back to the performance curve. The most recent plant where I specifed the pumps had nine pumps all pumping vegetable oil, at various different temperatures (therefore various densities and viscosities) all with different heads and all amazingly working correctly and reading the correct pressure on the gauges when tested. Funnily enough the only one that we had an issue with was cooling water but that was thankfully not my specification it was done by the client who thought he knew better.
As to comparing water pumps to oil pumps, that is known information. Have a read through books on centrifugal pumps, performance curves and how to understand them or maybe read up on one of the pump vendors web sites. You will find that most catalogue performace curves are shown for water but it is possible to predict the actual fluid performance just by knowing and applying the physical properties of the fluid. Like in the example above, when a vendor puts out a specific curve for a duty it will typically be for that fluid and not necessarily be for water.
So when you said
you did not really mean it did you. I posted suitable links and so did Fabricator but I guess they where not sufficient for you.
Anyway you are missing the point. There are centrifugal pumps operating all day everyday pumping oils without any problems or issues. Yes Hot oil (>200C) typically you would specify a mag drive sealless unit. The reason for this is simply to avoid any possible air ingress through the seal into high temperature oil which would immediately cause product degredation, not for specific safety issues. However for oil at 60, 80 100, 120 even 150C a "standard" centrifugal pump with either single or double mechanical seal would typically be specified and will operate well. No need for cooling or mag drives at these temperatures and also no need for PD pumps (altyhough they could be made to work).
Reduced shear was a product quality requirement not a safety one, however the impeller for the 1000rpm pump is exactly the same as for the 3000rpm pump either open, semi open or closed, it just turns slower and as such will not generate the same amount of head for the same diameter pump. However if you want to achieve higher heads with lower shear then you end up with a larger diameter pump (impeller). It is the impeller thrashing around in th eliquid that causes the shear not the acceleration and or ultimate velocity. So again it depends what you specify as to what you get. You can certainly get more thn sufficient head to run a homebrew type reactor even with a venturi or eductor using the slower speed pump (but then it will be more expensive and that seems to be more imprtant than safety to most on here).
I think you are really missing the point. With centrifugal pumps there is no obvious difference between a pump designed to pump say 100 lpm of water with one that is going to pump a similar amount of vegetable oil at 100C. The only difference is likely to be the O ring material in the mechanical seal. Not all but certainly the majority of pumps designed to pump water are also capable (if not specifically designed for) of pumping other liquids either with exactly the same set up or some very slight material changes. Certainly there are no fundamental mechanical differences at these sorts of temperature. Methanol is slightly different due to flammable atmospheres but again the pump construction is pretty much identical.
So the silk purse from a sow ear analogy is totally incorrect.
I think Rick has it spot on here. However a correctly specified pump either centrifugal or PD will be fine. An incorrectly specified pump of any type will give probelsm either maintenance, process or more importantly safety.
When relating the performance of a pump in a closed loop to the pump curve, do you calculate the head as the discharge pressure or the total pressure [discharge - suction]?
A centrifugal pump curve shows the "head" energy added to the fluid.
So to relate the actual performance to the specific curve supplied with the pump you would look at the differential pressure (discharge - suction). Obviously corrected for density etc.
I'd liike to add another pump option to the discussion - agricultrual roller pumps. They're my favorite pump design of the moment. Central Washington Biodiesel use them for all liquid transfers, as well as mixing 700 gallon batches. I'm surprised that I never hear them memtioned in these discussions. CWB gave me one that had seized. I bought a $30 rebuild kit and it works fine now. When used with a pressure relief valve ($12 at the farm supply), they won't overpressurize hoses. When used with an ex-proof motor, they're safe around flammable chemicals. They tolerate dirt and grit, and will pass moderate-sized frenchfries. They're designed to pump slurries of wettable powders, and are available made from a variety of materials - cheap cast iron (like mine) to expensive stainless steel, with nylon rollers (like mine) to more expensive chemical-resistant ones (teflon?). They'll even self-prime. They have most of the desirable characteristics of gear pumps, but won't jam when something solid tries to pass through.
Aren't roller pumps usually high pressure low volume? Is there such a thing as a 100gpm 1.5" or 2" roller pump?
There probably is somewhere but you are right they would not be common. 10-30gpm would be fairly common but the little blue pump only does 10 or 12gpm depending on who you buy it off. I assume that the 10gpm would be at 0-1' head, for people using 3/4" plumbing on a HWS the head would be a bit higher than that.
dultmeier have a wide range of pumps including fuel rated centrifugal pumps that will give you 100gpm for $1,500.
They also have pumps for hot corrosive(66c) liquids up to 100 ssu which would be in spec for veg oil I think, Magnetic drive same sort of output as the blue pump and only a couple of hundred bucks. but you wouldn't be able to de-meth with it.
The problem with finding a suitable pump is because the specification is pretty tough
You need a pump that is
Viscous fluid capable(oil)
Corrosion resistant(lye) and maybe acid.
Almost any pump will work till it fails, its what happens when it does fail that is important, does it just stop or does it burst into flames.
HAZMAT teams often like air-operated diaphram pumps.
As I understand it, they are pretty bomb-proof, and have no electronics near the pump/liquids.
Of course you would need good access to compressed air.
Oh I have a fuel rated 100gpm pump purchased from a pipeline surplus outfit, there are tons of options open to folks who will just look around.
I have two diaphram pumps, my 10hp 120 gallon two stage compressor will not keep up with them, a smaller compressor would not even have a chance.
Your confusing the pump with the motor driving it, they are 2 separate beasts. A TEFC motor with no internal overload or arcing sparking apparatus is perfectly acceptable in a Class I Zone 2 environment. There is no need for an expensive EX motor on a properly designed processor.
I disagree. Any cast or steel open impeller pump should be good for around 250F. With a good seal and a TEFC motor driving it (of course with the proper P&C) will last the average home brewer a life time. What will fail is the seal.
I purchased 2 used open impeller 130 GPM cast pumps for $100.00 delivered. I got a 3HP TEFC motor for $250CAD and 2 spare Viton mechanical seals for $65.00 each. The manufacturer will even make you a new pump curve if you give them the S.G. of the fluid your pumping. http://www.mppumps.com/non-htm...s_brochures/8061.pdf
These pumps brand new are around $600.
Anybody can find an affordable, suitable pump if they spend some time looking around... Murphy even sells affordable, suitable pumps brand new in the box... People first need to decide they need/want a quality pump and not the cheapest piece of crap they can get there hands on...
Keelec, Those diaphram pumps are great, I have a 1" SST one with Teflon diaphragms, the problem is they use a ton of air and have a very gerky pulse to them, I would never consider it for my processor but it is a great self primer for moving around any of the liquids we use in our hobby, including methanol...
Simple schematic for a pump and heater control with a high limit
Sensor for the biodiesel/glycerin layer
I thought the impeller shaft was the motor shaft(close coupled) on the blue pumps?
There are actually two varieties in that respect.
The little blue pumps are true "close coupled" units. The pumps I sell are also close coupled units.
A lesser known variety is one where the pump shaft and motor shaft are two separate entities but the pump's shaft is hollow and the motor's shaft slides into it and is usually secured with set screws and a key way.
The best Do-it-Yourself Construction Plans on the Internet!
Waste Oil Heating - Biodiesel Systems
Biodiesel Pumps Made In The USA
That is quite a common arrangement for close coupled pumps. Espeially when you getup above fractional horsepower sizes.
|Powered by Social Strata||Page 1 2|