LittleInch,
Thanks again for the response. We will continue to look into it. I cannot believe I did not mention it before, but the reason we originally needed the air eliminator on the discharge is because we are metering the flow into trucks simultaneously. The flow on the pump will be going...
Edstainless,
Limiting the flow so that they all empty at nearly the same rate is great, but the rail cars could be spotted at various places along the line, and even then, the spots are used with different pumps and header lines. It is not always so that, let's say spot "A" will be for "A"...
cvg,
I agree with both of those. Unfortunately this is an old system with no room in the rack to do a piping arrangement change. There are rail spots on either side of the rack, hoses, gangways, a catwalk, and loading arms here. it would be difficult to do so. However, we could throttle the...
bimr,
Thanks for the response. From your chart, it looks like the pump they tested lost prime at about 10% of entrained air. I could potentially use this as a starting estimate for how much air could be in the line. Assuming that our pump does not lose capacity when air is in the system, and it...
cvg,
From experience, we know that they are drawing air. Also, the cars closer to the pump have less losses in the header and therefore empty at a faster rate than the cars farther from the pump. They share a common header pipe and connect every 70 feet down the line.
We know it is a problem...
Hello all,
I am having difficulty determining the amount of air that will be pulled into the suction piping when one of our rail cars empties, but the pump is still pumping remaining rail cars. This is the basic scenario:
We are unloading 4 rail cars with a centrifugal pump. When the railcars...
LittleInch,
I would need to run some hydraulics to determine if the orifice plates would work and what our new flow rates would be. But the cars also line up in different spots every time, or the same spots could be used for a different hose or header pipe, so I think it could over complicate...
GD2,
We have contacted our Goulds rep for their PumpSmart services. I was under the impression it was only for their pumps, which are centrifugal pumps. We use positive displacement due to low NPSH requirements and efficiency with more viscous products (and we use the same PDs all over, and...
racookpe1978,
My apologies, it is a positive displacement pump (we have sliding vanes and rotary gear pumps in this application).
I'll dig deeper to find some typical flow rates that we have and get some more information. Like you pointed out, the scenarios vary widely with the temperatures and...
Artisi,
It is not often we get loss of prime during this operation. There are times when it happens, however, and we pinch or close down on the discharge valve and open up a bleeder line to purge the air until we can get a good prime again. By this time, the operators have noticed that there is...
Hi all, thanks for taking the time to read this.
I would like to know how a horizontal pipeline that is flowing a fluid reacts when air is added to it.
Background: I am looking to analyze the suction piping of a pump to program a variable frequency drive (VFD). Under normal conditions, the...
LittleInch/QualityTime/MortenA,
I apologize for the delay in responding.
I agree that air inlet from low level rail cars will cause an issue. When rail cars are empty, we get "burps" of vibration when it pumps large pockets of air through the pump. With the current set up, is there a way to...
Hi Asit859,
Is the second pump even necessary? Assuming you can use just one positive displacement pump closer to the reservoir, why would you not go this route? Are the friction losses too great on the discharge of the pump? Do you already have a pump here that you want to utilize?
I have not...
Georgeverghese,
I will certainly reach out to the pump vendor to see if they have NPSHr tests with the product or if they could run them for us. Even if I do not get hung up over NPSHr with a vapor pressure of 0.02 psia, I would still see reductions in flow and power, even if not through the...
I have never seen a curve like that, thanks.
I'll ask some of the vendors we have for a device that would shut with no liquid. I think that would work very well in this situation if they are not too costly.
LittleInch,
Yes, the system has multiple rail cars connected to a header pipe and the pump at the end. We currently use sliding vane Blackmer pumps and rotary gear Viking pumps.
I agree the header is undersized for the product.
Our operations department should be monitoring the rails cars...
Bimr and Hpost,
The railcars are vented to atmosphere. However, when flowing into the pump at approximately 1700 GPM, the friction losses in the suction pipe bring the NPSH available to approximately 10.4 ft. When increasing the flow rate to 1800 GPM (which the pump is rated for), the NPSH...
Hello all,
We are currently having two issues with our existing PD pumps that we use to unload rail cars. They are cavitating and aerating due to the varying product levels in the rail cars. We typically unload from multiple cars simultaneously, and this makes it difficult for our operators to...
Agreed. The other pump manufacturer we are familiar with here for Positive Displacement pumps is Blackmer, their sliding vane pump HXL10E has NPSH of around 8-9 the vendor tells me. The only problem is the price point is much higher. We could also try a screw pump, which would be cheaper and not...
LittleInch,
Just to update you. Viking updated their document recently, and the pump quoted is the RS in Table 5, pg. 12 of the attached file.http://files.engineering.com/getfile.aspx?folder=681319c8-4867-4c3f-8311-9d18b6a6bc3d&file=AD-19-NPSH.pdf
