5 replies to this topic

[Process Engineer_DES]

Respected Sir, i post here a querry
from a tank to another tank on the same height, we have to pump a heavy hydrocarbon oil, let the length of the line be 200m, we have to put a pump to move the fluid, the discharge pressure of the pump is 1025psi and the inlet pressure to tank B is 1000 psi.
my questions are:
which type of pump would be the best in these conditions?
the line dia is assumed to be 4 inches where as the velocity should not be more than 10ft/sec.

What are the basic requirements for designing a pump?
NPSHA,NPSHR

[breizh]

Hi ,
Many info are available using the search or download buttons . Did you try ?

To support your query a paper from Art .

Hope this helps
Breizh

[Process Engineer_DES]

Thank you,
Another question.. What type of pump is normally used for NgL? the heights of the two tanks are the same and the suction of the pump is also on the same height.

[breizh]

HI ,
Did you try Google , it 's a wonderful resource ?
http://www.flowserve...eam/NGL-and-LPG

Hope this helps

Breizh

[kkala]

querry from a tank to another tank on the same height, we have to pump a heavy hydrocarbon oil, let the length of the line be 200m, we have to put a pump to move the fluid, the discharge pressure of the pump is 1025psi and the inlet pressure to tank B is 1000 psi. my questions are: which type of pump would be the best in these conditions? the line dia is assumed to be 4 inches whereas the velocity should not be more than 10ft/sec. What are the basic requirements for designing a pump? NPSHA,NPSHR

1. For selection of pump type, refer to "PumpSelectionCurve.pdf" attached to S.AHMAD's post in http://www.cheresour...h__1#entry36154. Perry's "Chemical Engineers' handbook", 7th edition, McGraw-Hill 1997, Fig 10-26 (preliminary pump selection) also contains same diagram in English units.
If viscosity of "heavy hydrocarbon oil" is higher than (say) 220 cSt, consider the case of a rotary pump; but normally a centrifugal pump can do the task, just verify it through the mentioned reference.
Pump specification and hydraulic calculations may be the most common activity for a lot of us, so it is worth while devoting time on the subject, either by studying basic principles in books or by looking into problems like this one.
2. Following points of the problem, as stated, may need some furter check or clarification.
α. Tank B inlet pressure of 1000 psig =69 barg (assumed gauge) is too high for an atmospheric tank, unless B is a pressure vessel.
β. Pressure difference along the 200 m pipe is 1025-1000=25 psi? If this is only frictional pressure drop, it is rather high (3.8 psi/100 ft). However it can be up to 3 psi/100 ft for pipes of less than 250 m length (physical + equivalent) according to local practices.
γ. Check pressures. The task cocerns pump specification, as I understand. A sketch would be helpful.
3. Basic requirements of process pump specification call for
α. Type of pump (assumed centrifugal)
β. Pumped liquid properties: density, viscosity, vapor pressure at max pumping temperature.
γ. Pump flow rate (assumed as given, a m3/h)
δ. Pump head at the above flow rate: Pdischarge - Psuction, expressed as height of pumped liquid. You can also express it as pump ΔP (pressure units), since liquid density has been specified.
This needs selection of pipe diameter for discharge (given 4") and suction line (usually>4"), then calculate frictional ΔP along them; also consider any static differences. Tanks may be at same level, yet most conservative assumption is suction tank almost empty and destination tank full. Probably you can neglect this for simplicity (instructor to advise).
ε. NPSHA (available NPSH), calculated as per the examples in Art Montemayor's paper attached to post by breizh. You can also read books for "getting" NPSH sense. NPSHR (required NPSH) is given by pump supplier, usually being 2 ft lower than NPSHR, or even lower.
4. Above is hopefully helpful. Presenting your calculations after your try may also help.

[kkala]

Another question.. What type of pump is normally used for NgL? the heights of the two tanks are the same and the suction of the pump is also on the same height.

For liquified natural gas (LNG) I know that a local terminal uses pumps submerged in the liquid of LNG tank. Never having dealt with LNG design, I am now aware of the reason for this selection.
LNG is a cryogenic liquid. I would simply assume a vertical pump for this student task, seeing this pump type has low NPSH requirement. (see image at http://www.sulzerpum...umps_E00631.pdf.
The exercise probably aims at skillfulness in NPSHA calculation .

Edited by kkala, 25 September 2011 - 04:48 AM.