Jockey pump question

[KernOily]

Guys - This is a follow-up to my previous jockey pump question.

In the installation of a typical jockey pump, used to pressure-charge a piping system before a much larger pump comes on-line when the demand increases, what keeps the pump from deadheading and subsequent overheating/damage during operation? Is there a minimum flow recycle or bypass off the discharge back to a tank or back to the suction header? BTW this is not a fire pump system.

Thanks in advance for your time!!! Thanks!
Pete

 

[TD2K]

Pete, I would think you would need to run a recycle line back to the tank. Back to the suction line is another option but if there is essentially 'no' forward flow, I doubt the piping and pump surface will be enough to shed the heat of pumping that will go into the fluid. Going back to the tank is always my first choice.

The manufacturer will be able to advise you what the continuous minimum flow is. My experience is that these have gone up over the years, I've seen 25% as a typical value up to as much as 40%.

If you are just going to 'charge' the system with the jockey pump in preparation for starting the main pumps, running the pump dead-headed and shutting it down via logic might be fine.

 

[KernOily]

TD2K, thanks for your reply. The intent is to start the jockey pump from 5 am and run it continuously until 6pm. The main pumps ( two - 150 hp ANSI) will start on a low pressure signal in the header just downstream of the pumps. The jockey pump though needs to run continuously because there are small leaks in the system and because there are intermittent demands for high water rates throughout the day that require the big pumps. The system is a well kill system consisting of several miles of 6" and smaller pipe. The pumpage is 150° produced water. There are numerous teeny leaks that the owner doesn't want to track down and fix because it's like repairing a rusty bucket - fix one, and here comes two more.

Thanks!
Pete

 

[TD2K]

A few more leaks Pete and you'll have your minimum flow

 

[KernOily]

My thoughts exactly!! Controls? We don't need no steenkin controls! ;-)

Now, having said that... do you know of anyone who specifically makes jockey pumps? I suppose I could use anybody's small ANSI pump but I was thinking that there might be someone who makes a small low-efficiency (read: cheap) pump that would take some abuse and has a low minimum flow requirement. Thanks!
Pete

 

[quark]

Pete!

We have a pump with capacity 395 cu.m/hr and it's safe minimum flow is 9 cu.m/hr. You can have a bypass line to the reservoir and this is a general practise. But we have run jockey pumps on fire water system for 24 hours a day. (ofcourse in proper conditions the pump should start not more than once in an hour)

The pump runs for a very short period (in case of minimum leaks and if leakage is more then, as TD2K said, you need not bother)

I strongly feel that 20% safe minimum flow is too generous a figure. (It should be below 10%)

Regards,

Truth: Even the hardest of the problems will have atleast one simple solution. Mine may not be one.

 

[ferdy]

Connect the coil wires from the starter of the jockey pump thru the n.c. points in the main pump starters so when they start working, you jockey pump has a break. How do you control the main pumps?, by pressure controls or flow controls to keep them on line or off?.
Just put all them in a logic fashion.
Regards.