The best would be to get the information on the nameplates (pump and motor) of the actual pumps. You have to make sure that the pump can handle the same flow and the same head loss. If you need an increase in flow then you would have to do a bit of design before purchasing.
You are replacing, so do a lessons learned. Did the old pumps operate well? If not what problems did you experience? What features would be needed in a new pump to overcome the problems? If there were no problems replace them with pumps just like the ones there presently. Have you asked the person who operates the pumps if a change needs to be made. A smart operator would be able to tell you.
The cost of buying a pump is marginal compared to its service life. So you shouldn't worry about paying more initially if the performance and operating quality mean you will cut down on repair and maintenance costs over the long run.
There should be a plate on the pump itself indicating the brand, model and serial number. The easiest thing is to order a similar product from the same supplier.
If the model no longer exists, the supplier will be able to suggest an equivalent.
If you want to change brands, then you are going to have to provide more details on your operation: operating curve, total dynamic head, system control and mounting. Don't forget to ask for an adapter kit.
Regarding replacing a lift station pump, you should ask yourself the following questions:
- Has the operation change since the station was commissioned, number of connected customers, nature of the effluent, etc.?
- What are the issues encountered in this pumping station? (regular blockage, FOG, wipes, sand and so forth.
- Are the original pumps suitable for the operation in terms of energy consumption, run times, flow rates, etc.?
Once these questions have been answered, you will be in a better position to determine whether you need to replace the pump with an identical model, an upgrade or a new type of pump system.
In my opinion, a proper study of the situation can mean the difference between modifying a couple of parameters to prolong pump life and reduce maintenance costs and having to invest in new technology.