Thermowell projection into the stream is usually minimized if flow velocity is high (due to very long well length). Due to the inherently long thermowell, pay particular attention to vortex-induced vibrations and the resonant frequency of the thermowell. This will likely set your maximal...
Typically the Cv listed on the valve body and datasheet will be the 100% open Cv. A Cv of 0.4 does not sound oversized to me - an equal % CV will get down to 0.1 Cv around 60-70%, while a linear CV will likely be near 30% open to get a Cv of 0.11. In either case, the valve seems sized...
Good point. What is the normal operating % of the control valve, and what is the CV value at 100% open?
My rough math on this: 0.05 kg/s -> 1.3 gpm (s.g. of liq butane at 0.6). dP = 85 psig, maybe take 5 psig away from line losses = 80 psig. Q = Cv * (dP/s.g.)^0.5, estimated Cv = 0.11
I would...
There might be a few issues with the following solution, but this might be your best "cheap" try at fixing this:
Put a restriction orifice in the line directly on the reactor inlet nozzle. Size this such that the majority of your pressure drop occurs through the orifice, not in the CV...
Do you want the plant layout, isometrics, controls software setup, and fully trained operators supplied as well?
Eng-tips isn't a place for free design and for others to do your job for you. Get out of here.
Thanks for the input all. Our vendor suggested Discflo as an option, but cautioned that motor HP will be much higher (lower efficiency, I guess).
The current pump isan APT-33 with what is called a "special open" impeller. I'm not sure that extreme measures for low-shear are necessary, as this...
Ed,
I had wondered if impeller tip speed was the most critical factor, but I admit some ignorance as to the design of centrifugal pump internals; for example, I know that they have some level of internal recirculation flow while operating, but don't know if different levels of internal recirc...
Does anyone have a reference to a means to calculate the maximum shear rate of a liquid being pumped through a centrifugal pump? We currently are looking at replacing a Sulzer pump with a different brand (Summit), and while the pump curves are very closely aligned and within the process needs, I...
Rika,
Normally a full engineering FFS review is required if you want it to be able to withstand the -35 mbar condition. However, I know how stingy corporate management can be, and money for such an analysis may not be approved in a timely fashion, if approved at all. In lieu of that, you can...
Thanks for the advice, all.
Why? That equation pertains to tray strippers, and this is a packed tower.
A follow-up question on notation in these equations. Can anyone tell me what the subscript "BM" stands for? I cannot find an explanation in Perry's - they just introduce the term with no...
I have a water remediation stripper than was used to strip out 1,1,1-tricholorethane as well as dichloroethane and dichloroethene. For the past few years, though, it has been turned off. The original design of this is nowhere to be found, so I'm having to reconstruct the design from bits of data...
I agree with Pierreick on this - your risk from O2 depletion is MUCH higher than from internal deflagration, both from a probability standpoint (you operate well below the flash point) and a risk standpoint (AA polymerization is near-explosive once it hits decomposition temperatures). Due to...
MementoMori,
By the by, what is commonly used elsewhere and would also work here would be an Air/N2 blend to get O2% down to approximately 5-7%. The limiting oxygen concentration of most monomers is in the 7-10%(ish). That is why you see recommendations in monomers that contain MEHQ that O2 is...
Latexman,
I agree, but to OSHA, this IS a flammable liquid.
1910.106(a)(19)
Flammable liquid means any liquid having a flashpoint at or below 199.4 °F (93 °C). Flammable liquids are divided into four categories as follows:
The prohibition later on in the standard applies to ALL "flammable"...
MementoMori,
Be aware that OSHA may prohibit the transfer of flammable materials via air, depending on your plant's "classification".
To me, the definition is not clear on what types of chemical plants are covered and which are not. Can anyone elucidate?
1910.106(h)
Processing plants —...
Btrueblood,
The positioner itself actually drifts - it will be commanded to an output of 0% but actually be a few % open. I don't know the reason. The setup can be finicky - simply adjusting the zero screw can drive output back down to 0% again, but since this does not alter span it reduces the...
Deleted the thread over at the valve engineering forum because it didn't get any responses...
We currently use Siemens 760 electropneumatic positioners for various control valves on the site. While they are generally reliable, I've seen a few issues with the valves. First is that the zero tends...
Good point. I should have put in the caveat that mass flow is independent of downstream conditions, not changes in upstream density. The wording about the upstream conditions not mattering were more in line with the fact that it doesn't matter if you are Ma = 0.01 or 0.99 upstream of the choke...
No. The correct statement would be "under choked flow conditions, with decreasing of downstream pressure , the mass flow rate is constant". It doesn't matter what the upstream conditions are. If you hit Ma=1, you have choked flow.
A simply way to prove this is the fact that flow can become...
Hassann,
No, all thermo books do NOT have that provision. Choked flow is defined as a Mach number of 1. That's it. Evaluations of critical pressure ratio for choked flow are typically taken with upstream stagnation conditions (see Perry's Chemical Engineering Handbook, Section 6-22 in the 7th...
