Re: Unloading Bulk Tanks
To answer accurately, suspect we would need some more details on the layout.
Do both gauges read "0" (and or equal) when you have no pressure??
Regards,
Lyle ■
Re: Unloading Bulk Tanks
yes, both gauges read zero at start. ■
Re: Unloading Bulk Tanks
How about a faulty gauge?
Dirt in the tapping / gauge?
filter in the line ?
Losses across the fludizing membrain ? ■
Re: Unloading Bulk Tanks
Dear alabamajammer62,
The static + dynamic pressure upstream must be higher than the static + dynamic pressure downstream.
(dynamic pressure or velocity pressure)
The difference is the pressure drop loss between the two measuring points.
(Law of Bernouilli)
Your measurements should be representing the static pressure.
If your upstream static pressure reading is lower than the downstream static pressure reading, then it could be that the upstream reading is static pressure and the downstream reading is static pressure + dynamic pressure (caused by the measuring spot configuration), assuming that the pressure drop over the installation between the two measuring points is negligible.
It could also be that the two manometers are giving false readings (not accurate)
Check this by interchanging them.
Success
teus ■
Teus
Re: Unloading Bulk Tanks
thanks for replying. the gauges have been changed and lines have blown out. ■
Re: Unloading Bulk Tanks
thanks teus for replying but unfortunately all of what you are saying is rocket science to me. if it helps, the product that i haul is ground or powdered limestone. ■
Re: Unloading Bulk Tanks
Assuming they are measuring the same thing (type of pressure and product etc), would suggest that the downstream should be lower - otherwise it shouldn’t be flowing?
The gauges could loose calibration above "0" (both maybe correct, both may be incorrect, same for either gauge).
Could test with water manometer, though a 10 m high column maybe a bit to handle (to atm). A gauge manometer maybe more practical – though need to be careful the water is not introduced into the process.
Regards,
Lyle ■
Re: Unloading Bulk Tanks
alittle more info. i don't know if will help or not. i have only been doing this for a little over a year so a lot of this doesn't make alot of sense to me. when i unload i have keep my tank pressure valve completely closed in order for it not to keep building tank pressure. my aerator valve is almost closed so it wont build pressure to fast and clog up.it will run steady for a while, then very quickly it will jump to 15 psi and stop up. i have to constantly watch it. when it starts to rise i have to cut my hopper vave off till it catches up. does this make any sense at all? thanks so much. ■
Re: Unloading Bulk Tanks
If your line pressure rises very quickly and you have to keep the aerator valve and pressurization valves closed, it sounds to me like you need more blower volume.
Do you always convey into the same conveying line or does the bulk tanker travel to different locations?
If you are trying to convey a long distance or in too small of a line diameter, you will also see line pressure rise quickly and unless you keep a good control on the material discharge from the tanker, the conveying line will plug.
Have you ALWAYS had the problem with the guages reading backwards? If so -- my guess is they are mislabeled or during a repair period, the liners were inadvertently reversed.
Regards ■
Re: Unloading Bulk Tanks
dear alabamajammer62,
I tried to figure out the settings of your valves and it seems to me that you are pressurizing the tank through the fluidization section and that the by pass valve is open.
The limestone in the tank seems to flow by gravity to the outlet, leaving a void in the tank.
This void has to be filled with convey air, which is not supplied through the tank pressure valve (closed as you state)
That means that a relative vacuum is created, which is filled by the injected fluidization air.
But this air experiences some resistance while flowing through the limestone.
This resistances creates a pressure drop, whereby the lowest pressure is on top of the limestone. This could be the 2 psi which you are missing.
(Air is bubbling up through the limestone)
To be able to evaluate the complete system ans why it is choking requires more info s.a.:
air volume compressor
compressor type
convey pipe diameter
convey pipe routing
limestone particle size (distribution)
etc
take care
teus ■
Teus
Re: Unloading Bulk Tanks
thank for replying. yes i travel to the same place everyday. i use a 12' hose and pump up into the silo. the access line is 4". the gauges are not reversed nor labeled wrong because when i air up the tank, only the tank pressure gauge rises. after i get the tank to 12 psi i close tank pressure valve, cut aerator valve down to 1 notch before close and then i open hopper valve slowly. line pressure will gradually increase and tank pressure will fall till line pressure is more than tank pressure. i sometimes have to open tank valve to build some pressure and just as soon as it starts rising, i have to cut it back off or it will clog. as i stated before i haven't been doing this long and i was hoping for an explanation so i could inform our shop to maybe have it fixed, but it sounds like it is something that i will have to live with. i can unload it in about 1hour and 15 minutes. some of the other tanks unload in about 45 min and i was hoping to get this one there also. thank to all who replied to my post. i will be checking for answers for a few days. ■
Re: Unloading Bulk Tanks
Dear alabamajammer62,
As you are describing the unloading procedure, I can understand that you want to know why your colleagues unload in 45 minutes while it takes 75 minutes for your tank. (is it a tipping tank?)
First of all you have to check whether the installations are comparable.
Your pressure seems to be limited at 14 psi (blower?). May be the others have screw compressors (max 18 – 2.0 bar # 28 psi)
In your description, I am missing the extra air or by pass valve, which regulates the SLR (Solids Loading Ratio).
See attached file
Can you give us more information about the bulk truck and the complete pipeline you are unloading in.
have a nice day
teus
Attachments
bulktruckscheme model (1) (PDF)
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Teus
Re: Unloading Bulk Tanks
all of our tanks(trailers) have a 15psi cut off check valve. i unload by closing line valve to build tank pressure. aerator valve is open. after pressure builds, i open line valve ,close aerator to next to last notch(so it doesnt keep building tank pressure). then open hopper valve.once pressure is steady or dropping, i may have to either adjust aerator or line valve to raise tank pressure back up. here is a rough diagram of tank
Attachments
drawingJPEG:forum_attachments/file_container/drawing.jpg (BMP)
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Re: Unloading Bulk Tanks
Dear alabamajammer62,
I had a look at a bulktruck today, unloading Gyvlon (Gypsum) and that bulktruck was equiped as given in the attached drawing under number 1.
By setting the valves correctly the bulktruck was unloading at 1.8 to 2.0 bar(o) (25 to 29 psi) in a steady flow.
Your system should be operating in the same way.
To comment the capacity and choking, we need to know air volume and pipe geometry.
take care
teus
Attachments
bulktruckdiagram model (1) (PDF)
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Teus
Unloading bulk tanks
can anyone tell me why my line pressure is reading 14psi and my tank pressure is 12psi? if i try to raise tank pressure,line pressure raises also. shouldn't the pressures be the same? the trailer in question is a 1977 butler pneumatic. ■