In Line Centrifugal Pumps 2

[haniyah]

Hi every body,

Can I use in line centrifugal pump to pump water from underground water tank to over head tank? The suction lift is about 10' and the total head is 90'and I want to use upvc pipe for transportation.
And further more that what should be the ideal distance between the elbow of suction line coming into the pump from underground tank and pumps's suction?

 

[Artisi]

1. Yes.
2. Minimun of 5 diameters - 10 would be better.

 

[Clvet]

If there's a suction lift involved, the pump will either have to be self-priming or there will have to be a way to prime the pump. I don't know of any vertical self-primers out there.

How do you plan to prime the pump initially?

 

[pennpiper]

Haniyah's second question asked:
"And further more that what should be the ideal distance between the elbow of suction line coming into the pump from underground tank and pumps's suction?"

Artisi's answer to this question is:
"Minimun of 5 diameters - 10 would be better."

This is an "In-Line" pump according to Haniyah's original question. Now an "In-Line" pump Example

http://cbs.grundfos.com/au-nz/lexica/CAPS_level_2/PRO_TPE_pump.html)

is one that has the suction and discharge horizontally opposed with the shaft vertical and the driver (motor or turbine) mounted above. In the example in the link the suction is on the right and the discharge is to the left.

Let's say that the suction flange face is the reference point for this discussion. Downstream (the pump side) of the reference point the Flow turns down at almost 90 degrees, then 90 degrees horizontal and then 90 degrees to the vertical to the "Eye" of the impeller. All of this in the short span of less than the distance from the center-line of the pump to the face of the pump flange. That is a lot of twisting and flow turbulence.

So, my question is this. Why does Haniyah need 10 or even 5 diameters between the face of the pump flange and the first upstream elbow? I would recommend that a prudent cost effective layout of the piping is all that is required, considering (a) function, (b) the required fittings, flanges and valves and (c) proper consideration for flange loading and stress.

In my opinion, the "10 diameter Rule" is bogus for this application.

 

[JJPellin]

Almost every pump other than a single-stage, end-suction overhung pump has an internal flow path that is not a direct straight line into the impeller. But, all of them are designed for a uniform flow coming into the suction flange. In other words, the design of the pump takes into account the internal flow path. I have personal experience with chronic bad-actor pumps where a major contributor to the problem was a suction line without a sufficient straight run. The worst examples would be double suction impellers in a pump of any configuration. But, problems could be created in any pump if the incoming flow is uneven across the cross-section of the pump and excessively turbulent. I would strongly suggest a straight run of at least 5 diameters as Artisi suggested. If the pump has a double suction first stage impeller, I would insist on a straight run of 10 diameters.

Johnny Pellin