Increase Design Condition of a Pump

Contact the pump manufacturer for advice.

It depend on the pump.

Assuming that it is a centrifugal pump.

Sometimes pumps are sold with a reduced impeller. In that case you can increase the size for better performance,

The speed can also be increased.

In both cases within limits of the pump and you will need more power to drive it.

A new pump set selected for the duty may be your best option.

He mentions API610, which is a standard for centrifugal pumps. The equivalent for gear pumps is API676.

You mean, pump design? Technically,like impellers and the other stuff, or this just a increase in rating conditions for changes of delivery or intended usage.(Pump selection)

If this is only intended for change in Q volumetric rate and Head, use Hydraulic Power of the condition. Like P=ρgQH add up pump efficiency and pressure losses due to conduit friction there. You should get your pump rating for the new pump.

However, if you mean really is pump design like impellers, volutes and casing design, consult the book for pump design. There you should see the pumps in their design parameters.

get the pump curves from the manufacturer and you will know weather its possible or not by looking at the current operating point and the point you want to get to on the curves.

Well put, brich. Just a few points to add (some of which repeats what has already been said).

Assuming again that increase in design condition means increase in flowrate, which is the most likely meaning, then you should first check the pump documentation (or nameplate, or manufacturer) to see if the impeller is trimmed, and could be re-fitted with a larger diameter impeller (as mentioned by Hendrik). Otherwise, the only option is to increase the pump speed. Check with the pump documentation or manufacturer to find the max. rated pump speed.

The biggest limiting factor will be the motor rating. If it is sized in accordance with API610 specs (abs.kw +15%/20%/25%, depending on size), then it might not have enough in hand to accommodate much, or any, increase in flow (considering the increase in absorbed power will be the cube of the increase in speed, see Affinity Laws above). Follow brich's recommendations above to calcúlate the new absorbed power, not forgetting that an increase in flowrate is also likely to result in an increase in system head (so you also need to refer to the system curve), and allow the minimum margin in accordance with API610 (I assume that is what you are working to?). Even if the motor is sized for End of Curve and max. impeller dia, there still might not be much room for an increase, especially if a VFD is going to be used (normally constant torque below the rated speed and decreasing torque above). If you have to change the motor, it might also be necessary to change couplings, baseplates, etc. So a new pump might be a better option.

If our assumption is incorrect and the increase in design condition is not flowrate, then it is most likely to be system pressure or temperature. In both cases the pump documentation (or nameplate) should tell you what the pump is rated for.

Whatever the case, you really should be discussing this with the pump manufacturer in the first instance.

Thanks all for your advices and suggestions, the initial design condition of the connected piping is 82 barg and 80 °C, due to changed process condition, they would like to rerate the pressure to 98 barg, temperature remains at 80 °C. We can do the assessment of the piping components including the flange, using ASME VIII, whether or not suitable for the rerate condition, however not clear how to assess the suitability of the pump for the rerate condition.

As advised by PWSlack, we will request the manufacturer to look for this rerate condition.

I see, just check the Q, H, RPM rating, given on the manufacturers curves for the pump.

Pressure is inversely proportional to flow capacity, while flow capacity and pressure is directly proportional to rpm.

I could not well assessed the condition because the configuration is not given in figures or diagram. Its either 98barg is like static pressure head something like that or the pressure of the discharge side of the pump at operation. Its not clear.

But if that pressure you mean to say is at line at discharge side of the pump, you must look at the pump curve of you pump (at Q-flow, H-head, rpm) relationships.

Definitely in this case, if your pump is in range with the Q and the P in the curve, you have to only increase the rpm(increase motor power rating & add up step-up transmission). But, if its not on the curve, you must buy a new bigger pump.

see page 7 (this Q, H, rpm pump curve) http://www.eninepump.com/zhichi/technical_6.pdf

If you are planning to increase speed, you can use the affinity laws to estimate changes in pumping capacity (or reverse to estimate the changes in specific speeds required to achieve the needed pumping capacity). However, seals and a few otehr components might not be sustainable at significantly increased speeds, you would need to talk to the manufacturer about the pump specifications. On the other hand, the majority of water pumps we use in our pump station designs are essentially the same pumps, and the motor speeds/impellers are the main difference.