pressure drop behind pump

[mfqd13]

Hi, i have de following situation: vertical diesel tank with aprox. 7m height above the outlet. next i have a coalescent filter that has a pressure drop of 0,4 bar (clean) to 1,0 bar (change-out). next i have a pump for 50 l/min and 0,6 bar head. it pumps to a consumer at 50m distance and with no level difference in relation to the pump.

Would be any problem in the aspiration of the pump because of the pressure drop of the filter??

Thanks

 

[BigInch]

Not possible to say without knowing,
What's the elevation difference between bottom of diesel tank and pump centerline?
And do you have the NPSHR required by the pump at 50 l/min

Independent events are seldomly independent.

 

[LittleInch]

As big Inch says we need more info such as min liquid height above pump centreline, size of pipes, temperature of the diesel (warm is worse), type of pump and NPSHR of the pump at 50l/min.

From the vague data you have provided, at worse case for the filter, high temp and low tank level, it would look like there is potential for cavitation and problems with flow. Is this built and operating or are you doing design? Normally you wouldn't put a filter like this on the suction side of the pump as it creates too much pressure drop.

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mfqd13]

The only information that i get from the supplier is that the pump has a max. aspiration height of -4m.
The difference between the bottom diesel tank and the centerline of the pumps is aprox 400mmm. (i can increase a little bit this)

This is in design stage

 

[LittleInch]

Tell him to send you the pump curve - the data supplied is unclear.

Also give us the data in the attached file and then we might get somewhere. Min liquid level is what we really need in m above the pump centreline.

Oh altitude can become important so let us know what height above seal elvel you are.

I suspect you will need to move the F/C downstream of the pump and get a bigger pump, but let's see what comes back

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[mfqd13]

LittleInch

Thanks.
Please see the attachment.

I've attached also the pump and the filter specifications. Let me tell you i'm only analysing 1 pump, but i will have 3 in parallel and the idea was to put only 1 filter for the whole system.

 

[mfqd13]

Please see the pump curve

 

[LittleInch]

Assuming your filter data is correct (and sounds about right to me), it looks like you have a min of 14m absolute head avaialable (based on sea level location), max 19m.

If we take piping losses (friction) as 1m (short distance, reasonable size), vapour pressure as zero.

It looks like the pump would like about 5m absolute head (it's a pretty basic pump). Pressure drop at 1 bar across your filter / c is 13m, 6m at min DP based on SG of 0.8.

So, low liquid level in tank + max DP across filter, available head is 14 - 1 - 13 = 0, < 5 required = cavitation / no flow
high liquid level, low DP, avaialble is 19 - 1 - 6 = 12, > 5 so OK.

You can do the other combinations (low liquid, low DP etc), but I think you might need a pump the other side of the F/C, or raise your tank / lower your pump by 5m for worst case condition

My motto: Learn something new every day

Also: There's usually a good reason why everyone does it that way

 

[BigInch]

Diesel day tank bottoms generally need to be located overhead at least 6 m.

Independent events are seldomly independent.