Centrifugal Pump

Dear

Many thx for sahring the information.

Attached a rough line dwg of the application.

Two pumps are being used for different applicaion in same machine so it is not installed paralley.

If connected as drwn in the green colour, can i have the same flow as before as individual pump if my pipe size is same?

or as you mentioned i will make main line 6" and branched to 3" and 4" will have any adverse effect in terms of pressure and flow?

Please guide me.

The tank with the lower inlet head will take the greater part of the green flow, and will fill first.

• What stops it overflowing?
• What stops it bursting?
• What stops the flow to the left tank while the one on the right fills?
• What is the significance of filling the two tanks sequentially as opposed to simultaneously?

It would be wise to consult a local Process Engineer that has sight of the system. Prepare a Piping and Instrumentation Diagram, and do a mini-HazOp [Hazard and Operability Study] on the system before any modification is made to it.

Hi Rallish,

To have a better communication and understanding, First let us see ONLY one of the existing Pumps...

- Can we conclude from the details provided by you that the PUMP "A " - 0.6 M3/MIN, 50 mtr Head which feeds to Pipe Header, runs contineuosly BUT pumps water only when the pneumatic valve opens? That would mean that for rest of time, it will be running in NO LOAD condition. What is the frequency of the pneumatic valve operation? Also, what is the peak load and average water consumption of the machine connected to pump A??

I want to see whether it is possible to have a meaningful discussion in such forums and also if the solution can be found to such problems.

It is not possible to have a meaningful discussion on this topic with you involved, because you still have no idea of what the OP wants.

I suggest that you remove yourself from this discussion to avoid your continued interference in a discussion you do not understand.

Good day!

why you are interfering?? I just do not understand your attitude?

Are you the owner of the group?

I did not write to you..so pls behave as you should on a public forum.

You are only adding confusion to the discussion. You have not made a single constructive comment yet.

Good Bye.

As PWSlack said, there are a number of new variables here to be considered with a single pump.

I'd find out what the original rationale for two pumps was.

I'd never design a system to use two pumps if one would do the job.

My simple short answer - "NO".

I suggest you contact someone that understands what you want to do and can advise you correctly.

As you are "new " to this, get someone that is "old" to this type of re-modeling of the system. There are SO many variations to what you propose, that there is not enough time to cover all of them in this forum.

As well as all the other excellent advice provided by the league of oracles, you need to consider that you are introducing a single point of failure for two systems. This may not be a good thing.

I will encourage you to keep exploring the possibility in detail though. You will learn through the process and shed a little of the "new to this". At least you had the good sense to ask.

Don't stop trying and learning mate. If you have the nads, skills, intuition, care and resources, then suck it and see.

Hi,

Its quite a interesting situation for learning and discussion.

- First the Input Data.

a. The suction/discharge pressure of both the pumps when they are running independently. Pls mount the pressure gauges if not there.

b. The existing Flow rate of these pumps from their curves.. I have a feeling that both the pumps have the same characteristic curves.

- Now for the modification

a. You have to estimate the pressure drop in the modified system

b. You have to be aware that the Both the pumps will now opearte at same discharge and suction pressure.

c. The suction size and velocity is very very Important factor esp. with 2 pumps. So make a big suction header with velocities approx. 1 m/ sec max.

d. Design the piping in such a way that the pressure drop in both the lines is almost same.

e. Its not as complicated as it seems to be...:)

More after hearing from you

K K gupta

Dear Mr. Ralish,

Since there is a difference in the Pump Head - 50 Metre and 36 Metre this cannot be connected to operate in parallel. We need both pumps of the same HEAD for using in as PARALLEL OPERATIO. This concept ( of Parallel Operation) is like synchronising 2 generators of equal voltage and different volt generators cannot be put on parallel opration.

Hence discharge pipe size has no meaning. You have to operate the pumps of different heads independently.

DHAYANANDHAN.S

Perhaps you should look at the drawing provided by the OP. With proper controls and valving it can be made to work. He wants to go from two smaller pumps to one larger pump.

It just struck to me..We used to get the Impellers of pump, TRIMMED to reduce the Heads... So u can try the same method to match the heads of the 2 pumps

Er, why would the OP want to do that?

to save energy ...

Normally the operator may use a throttling valve..but it causes loss of energy

thats twice you got it wrong.... do you understand how a centrifugal pump works?

I have commissioned atleast 100 Centrifugal Pumps from small to very big in my career and have the first hand experience, so pls think twice before challenging what I say..

Thanks

Regardless of the number of pumps you have commissioned, you have consistently failed to grasp the crux of the OP's question.

I tend to agree with the others who say your answers are "misguided", at best.

For clarity, I have copied the OP's statement here:"if i combine these two pump to a single pump".

I hope this helps you to understand the real question.

only 100!

I've been at this for over 20 years installing pumps at AND commissioning them at a rate of at least 3 a week. So you do the maths!

As for challenging anything YOU say....

....to quote myself again.... "My father says.. open it and prove it, keep it shut and let them think it!"

As you have stated something that at best is questionable, then you must except that you will be challenged by someone that has a better understanding than you. Your comments are way off target and at best are not helpful to the OP.

Normally I would say sorry for this wakeup call, but if I read you correctly I would say you have never been challenged, therefore it must come as a shock and you feel insulted and belittled.

If that is the case, so be it, but accept that your comments have been greeted with a certain degree of disbelief and learn from the comments given to you, in the spirit of mutual learning

Hi Guru,

Yes its correct to assume that I got the question wrong...and the reasons for this is not important..so what I ever solutions I suggested earlier does not apply in this case..BUT in case someone wants to run above 2 pumps in parallel and YOU want the discussion, I am open for it..

if the question from the OP was "to run two pumps in parallel", then we could have a discussion, as it was not, then there is no point at this moment in time.

However what I do like about you, is you have realised your limits, and hopefully you have learnt something.

I hope you are not offended by the bluntness of myself and others, and you will continue to use CR4.

That is so old school.. if you are going to waste time doing that, and not getting it right, you have reduced the pump to a pile of scrap. Use a VFD!

Welcome to the 21st Century!

Dear Sir,

My intention is to combine two small size pump to larger capacity one....

One branch will b of 3'' and other will b 4'' size as i mentioned in th dwg....

rr

The forum does not understand the process.

• It doesn't know what the fluid being pumped is.
• It doesn't know the temperature of the fluid.
• It doesn't know what the process implications are of filling one tank and then the other rather than both tanks at once.
• It doesn't know what stops the tanks from overfilling.
• It doesn't know what stops them bursting.
• It doesn't know what stops the one tank draining into the other.

Therefore it is better to engage with the Process Engineer at the facility that does know these things.

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Let's examine your proposed single pump solution from a startup perspective. When it is first installed the discharge pipes are empty. When the pump is started, the fluid flows up the pipes. When the level reaches 36m it will start to flow out of the pipe into the machine. If the fluid could all escape at 36m, why would the pressure of the system rise enough to push the fluid up to 50m? The answer is, the piping going to 36m must have enough restriction in it to limit the flow to the desired flow rate. When the pump output exceeds the flow out of the system, the pump pressure will rise and the fluid will rise to the 50m height. However, as the pressure in the pipe rises, the amount of restriction needed in the lower pipe will change.

This restriction in the lower pipe will be a combination of pipe size, pipe configuration, fluid dynamics, and any kind of valve, or restrictor plate that you might need to put in line to limit the flow.

Your proposed solution also includes a small increase of total flow. Where can the excess fluid go?

hi,

right hand side tank capacity is approximately 750 litre capacity and also drain line ther which will take care the excess flow.

The left hand tank is actually a head with 6 outlet and a penumatic stop valve installed on the pipe which will open and allow theflow to head when the machine needed only.

if the flow on the lefthand pipe ie 3'' pipe is blocked by pneumatic valve, will all the flow will diverted to the right hand han tank i mean all the 1.5m3/hr?

rr

There are only two outlets in your system. If you block one, all the flow will try to go out the other outlet.

Most pumps are selected to run at or near their best efficiency point. With one pump running two processes, when one process shuts off, the overall flow will decrease a little due to the higher system back pressure. But flow in the second process will increase greatly, unless you throttle the flow back. When you throttle the flow back you will move the flow away from the best efficiency point and may below the minimum flow rate for the pump, resulting in possible damage to the pump or excess power consumption. You could use a VFD to throttle back the flow and stay closer to the best efficiency point, but you would add cost and increase the complication of your system's control.

GA from me.

KKGUPTA.. pay attention!