I agree with pwslack,

But I not sure, I believe the interpretation was lost, because its not that different pump manufacturers pumps won't work together, they will. Its just the the flow rate would not be guaranteed.

But really, even if it were the same pumps, the flow rate is still an estimate, because they are using water at probably 55 degree F as a base line.

Go to the manufacturer and request a different distributor and explain the reason.......even though, the distributor probably has the manufacturer do the sizing.

Even with two identical pumps, there are a lot of variables. Lift, pressure, pipe restrictions. I can understand the reluctance to the project.

You could get away with it by using check valves on the outlet of each pump, maybe.

? check valves

Check valves.

I didn't say that's the way I'd do it. I said it could be done that way.

of course not and no it can't. Is nonetheless an interesting question. ANSI pumps are generally certified to be within +/-5% of the published curve so it might be said that a given mfg would have the same problem as multiple mfgs. PRV's could maybe used in a manual sort of way, or FT's & FC's could do better. Or lead / lag / alternate. Or recycle loop. Pump guys do this all the time. Call one.

No apologies Lyn, your arrogance well exceeds your humor.

This is right. Without undo brainwork, reasonably equivalent pumps will do reasonably equivalent work, give or take a little but it is not a yes or no question. Get fancy if you want. Make sure NPSHA > NPSHR for both and measures are in place to prevent either pump from operating below its minimum flow. GA Holzfeller!

Yes two different pumps can work in parallel. Not well though.

If you really want to save your existing pump and use a different pump in parallel, look into a VFD. It can adjust for the difference in pump curves.

Typically, you're better off using 2 of the same pumps because it creates less of an operations and maintenance nightmare.

Multiple pumps is always a challenge. First you need to make sure there is adequate suction supply for both pumps, you don't want to increase suction head by having the pumps fighting over the available water.

The controls have to be set up to time the pumps starting and stopping, to control surges and spikes in the system, and adequate pressure tanks are necessary.

Depending on the use, you might consider having one pump handling large flow up to a certain pressure, and a second pump for lower flow but capable of higher pressure. I call this the 'topping off' pump.

I would say that the argument is not valid. Of course, there will be different performance provided by different pumps but let us take a case of expansion of 50% in flow. You couple a pump of 50 cum/hr. to an existing pump of 100 cum/hr. The same manufacture's argument holds no water, so to speak. It happens all the time when a pump is sent for repairs & another is coupled to the mins for operation. If I want a certain discharge over a certain head, my concern of course, is how the two behave at variable frequencies when coupled to a vfd.

For parallel operation of the centrifugal pumps, you need to have two identical pumps in Hydraulics(Q-H) characteristics and slopes, as also the suction piping layout.

Generally, the pumps in process service is required to operate at normal/rated/turndown capacity and not necessarily at a single point fixed capacity.

Incase, you operate in a system, with a control valve, two pumps of different Q-H slopes, there won't be equal sharing of capacities between the 2 pumps and there could be a possibility of overloading of the motor of one pump and damage/vibration to the other pump being forced to operate at lower than it's minimum continuous stable flow.

This is precisely the reason, the end user tries to use pumps of identical hydraulics (same pump models) manufactured by single manufaturer. Also, any new pump manufacturer can guarantee their pump's performance in isolation and not in parallel with any other pump .

But if after few years, the original pump supplier is not existing, one can try to supply the existing pumps curve to a different manufacturer and get a new pump engineered closer to the curve in slope. Else, you need to change both the pumps.

Hope this helps,

Kingcow Protector

They just want you to use their pumps.

You can mix and match and getting it to work is part of the craft.

Play their game and ask them to quote for a full replacement solution. You can watch them put their logos onto the OEM pumps that they'll be badging up....

Or call them on their BS and ask them to prove it won't work.

Meanwhile get more quotes. YOU have the whipping hand here.

It is not that the other manufacturer's pump will not work if engineered and selected for the job. The problem will begin after and during operation because each will blame each other's pump and not willing to accept responsibilities of pump damaged/trouble-shooting during and after warranty period. Suggest you put a pair and use existing as spare/standby.

It depends on how the others select their pumps. Pump heads, RPM, and flow rates need to be fairly close to the original pump selection. Pump curves need to be added together and plotted against the system curve to see what the balance points are under different operating sceenarios. Suction head needs to be reviewed at the various flow rates possible.

After this type of review, you should have a comfort level whether the particular quoted pump will work in parallel with the existing pump.

If both pumps (similar impellers) are made to same national or international standard to deliver a certain Q at a certain H, can't we operate them in parallel?.

Of course you can. But, each manufacturer varies in their design & thus, try to make sure that they derive maximum benefit. I fail to see why the pumps cannot be different if I keep various affe ting factors under control. But pump manufacturers do not bother about the client, only their bottomline.

For parallel operation of pumps , the most important thing is that the shut off heads of both the pumps should be same. Otherwise, the pump with less shut off head will give less discharge. Pumps with different flow may very well work in parallel. Once in parallel, the pumps will not run on their individual; characteristic curves but they will run on the combined curve. As long as the shut off heads are same, there is no problem in selecting pumps form different manufacturer.

I guess you must be talking about surface operation of the pumps!

My friend Holzfella is correct, it's the manufacturers that CAN'T or WON'T work together, and if you think about it they want you to spend money with them, not buy from someone else.

In Libya we routinely use different makes of ESP's (motors, protectors & PUMPS) together in the same string with NO problems!! NOTE: I say different manufacturers NOT different sizes (flow rates) of pumps. To date, even with mixed units we regularly achieve between 2 to 3 years run life downhole!!

Providing you ensure that your inflow to the pumps is OK... (and I guess you're not here to talk about that) and you have a control valve or orifice plate on the pump output then you should have no problems

I would suggest that the second pump you get has the same rating as the first,. unless you do not require that volume when both are running, then you might think about a check valve (Phoenix) in the line to prevent back flow.. however CV's for parallel operation are a good idea or you'd have operators running around trying to open & close valves every time you stop and start the pumps! Out of interest, what are you pumping? Oil, water and how far?

I'm in agreement with both brich and IRSHAD here. If you have two centrifugal pumps running in parallel that have the same shut-off heads on the System Head Curve as well as provide NPSHA>NPSHR, then you will most likely not experience any problems with 2 different manufacturer's pumps. One pump may deliver at a different flow rate then the other.

You can optimize their respective H-Q characteristics of each pump by:

1. Installation of a independent VSR controllers;

2. Installation of the appropriate flow and head control valves on the discharge lines;

3. Trim the impellers, if necessary;

4. Provide separate pump suction lines, and insuring that there is NPSHA>NPSHR for both

I have seen different pump manufacturer's centrifugal pumps installed side-by-side many times in the past in the water works industry, sometimes with multiple pumps in parallel. This is not uncommon, but requires careful engineering testing, analysis & design.

No big deal, really! The manufacturer's that stated that they couldn't do the work were full of BS....so, talk to other manufacturers/suppliers/installers that can do the work and guarantee/warranty said work in accordance with the Contract Documents.

There should be no problem with using different manufacturer's pumps in parallel operation. I recommend you read the following "Pump Guy"'s article on this topic as well as any other one of his you can get your hands on: http://www.flowcontrolnetwork.com/articleprint.aspx?articleid=4071

EXACTLY!!!!!!!

Excellent!! I wish Larry was my mentor. His experience on pumps, the monitoring, the trouble shooting are awesome. This sums up that as alternative application 2 pumps from 2 different manufacturers can work with no problem but not as parallel. My suggestions to install 2 pumps (engineered as per application) of same make stands. The existing to be as standby/alternative application only.

As many have pointed out it can work as long as the pump curves are very similar in shut off, flow vs. head, slopes of curves, NPSH requirements etc. Each will produce a flow consistent with the point on its curve that produces the required head to meet the discharge pressure. My question to you is "Why do you want to buy a different pump than the one you want to parallel and thus require your maintenance department to stock a whole set of spare parts for a different pump?" We used to work with our customers to minimize the number of spare parts required to stock by utilizing the same size pumps where possible, often just varying the impeller diameter to achieve the proper head, if we could do so without sacrificing too much efficiency by not running near the BEP and by minimizing the number of manufacturers we bought from. Occasionally a customer would request a change rather than buy just one or two pumps where the spares were vastly different from all the other pumps being recommended. It may just well be that the other pump distributors also know that it is an exercise in futility to quote when they fully expect that your people will simply buy an identical pump.

Standardisation of engineering items can solve this. For instance the type of receptacle/plug, voltage/frequency of power supply etc varies from country to country. So are pumps. If all are made to a common ISO standard interchangeability will be possible and money could be saved.

Standardisation would not help in this instance. The most important considerations (pump-size, shape of curve, duty-point on curve, suction conditions, etc.) all fall outside of what would be covered by a pump standard.

In any case, standards have already been in use for many years for some pump types, eg ISO5199 for chemical process pumps, API610 for hydrocarbon process pumps, etc.

Ultimately this should not be a problem for any pump engineer worth his salt.

If types of pumps and impeller sizes(Q,H,rpm) are standardised,we can select a pump for a given duty from any manufacturer in the world.

This is a composite curve from a manufacturer of chemical standard pumps (ISO5199). All manufacturers of such end-suction, single-stage centrifs use the same sizes (eg 50-32-160 is nominally 50mm Suction, 32mm discharge and 160mm Impeller). Similarly for HPI pumps to API610 and water pumps to DIN24255/EN733/ISO9908.

Clearly this is not a solution to the OP's problem.

The world isn't like that, though.

But in the totalitarian world, how then can they claim, "Our pumps are better than yours".

or the opposite

Depends on materials,workmanship,cost etc

Then why standardize

Or we could just conglomerate all pump manufacturers into 1 company and have that 1 company supply all of the pumps worldwide...

What a great idea.. why haven't the pump manufacturers thought of that!!

If they did as you suggest then where is the free commercial competition? In fact it's quite the opposite. A certain french owned maker of pumps has now changed ALL the designs of their pump so they cannot be used in conjunction with others, but they STILL conform to standards relating to type of material, manufacturing processes etc, etc...

So that's your idea with a hole in it!!

yes, and have all cars come in the same color, with the same options, same model with interchangable parts........Yes the possibilities are endless.

I seem to recall that the vehicles from some eastern country were not being sold in Europe because of a certain parts interchangeability with some BMW models.

Yes, two parallel pumps not the same make could anhilate one over the other. Problem is how to synchronize the head output of eah pump. Unbalance head at discharge side pushes the weaker one.

I think that saying they could "annihilate" each other is going to draw a lot of negative comment on your position. Unless the pump curves are dramatically different, they may not run at exactly the same throughput but they will operate at basically the same discharge head to meet the discharge pressure that is established either by the system resistance or the action of a discharge pressure regulating valve that is either flow, temperature or pressure controlled to meet some operating criteria. The slope of the curves would have to be vastly different and the question would be why would anyone pick such a combination to run in parallel in the first place when there most likely would be a more compatible combination. The safest course is the same pump at the same RPM with the same diameter and design since some pumps are offered with various designed impellers to meet NPSHA or increased flow within the same casing size. But annihilating one or the other is a bit strong a position.

Your pump can work paralelly with another pump of another producer. You need to know at least 3 points (amounts/pressure). If the points are identical and shut-off head is also identical the pumps will work with no problems. If you are on doubt, then simulate it in Hydroflo 2.2 prog and choose the pupms from the PumpBase additional program. You can observe the charts with combination of centrifugal pumps of different producers.

A horse and a goat can't be yoked together to push a cart....

I was just going through this, and I thought it would be valuable to add.

At one of our satellite plants we are increasing production by 50%. (From (2) process units to (3) process units)

Had to add another cooling tower and replace our (3) existing pumps with (2) larger pumps.

Well now since this is one of our satellite plants, I was hoping to use some empirical data, but as I was looking at the equipment, the (3) identical pumps, one has a different impeller size, (so it's not so identical) . When this happens the larger pumps will throttle the smaller pump cause shaft deflection and stress the seals.

I did come across this site McNally Institute which has some good explanation of what is going on, I thought I'd share it.

In my case, I have two options of which I will try both, and that is going to the site and taking one pump at a time off line and look at the results. There is an outlet pressure on each pump. and each pump are within 5 PSI of each other. (My problem was not having the required pressure from the main at the location to the process equipment, of which the second option I'll have to do manually)

But here is the site: http://www.mcnallyinstitute.com/15-html/15-01.htm

How this happened with the different pump impellers, who knows, The plant was built new about 15 yrs ago, and the last expansion about 8 years ago the third pump was added. And the mistake just kept being carried through.

(by doing it manually, fortunately I also have software that will assist me in some of the grunt work)

But the Mcnally site gives a good explanation also of the effect of having (3) pumps in parallel