Hence for both the scenarios, we will end up having a table of data consisting of different values of head required for pumping at different flow rates. For calculating the pressure drop through the pipes we will be using Hazen William's formula whereas for calculating the minor losses in fittings we will be using K*(VР’Р†/2g) (V - Velocity in pipe, g - acceleration due to gravity).Р’В There will be a certain exit loss at the discharge points B and C which we will be calculating using K*(VР’Р†/2g) considering K=1. We will first need to determine the resistance (which we often define as pressure drop) through the system that the pump will have to endure to effectively transmit water from the reservoir to the two discharge points (B and C). Step 1 - Calculating the pressure drop / resistance in the system and preparing the data for generating system resistance curve Moreover, a lot of helpful resources are available online for anyone who intend to delve deeper. However, links for all the resources used, will be provided below for further review by anyone. We will not be heading into details regarding the tit bits of all the calculations involed. The point of intersection of the two curves will define the operating point of the pump and the respective flow rate during operation. To determine the actual flow rate through the pump we will need to superimpose the system resistance curve over the characteristic pump performance curve (Flow Vs Head curve). However during its actual operation, the pump may provide a different flow rate (considering we will not be throttling any discharge valves). The rated capacity of the pump has been defined as 20 mР’С–/hr. However, the first thing that we need to concentrate on is the pump itself. We need to find the flow through the pipes AB and AC. We are going to consider the pump to be of constant speed type (not VFD driven) to make things a bit more complex (also generally in India we commonly have to deal with constant speed pumps). This is a very common system which we often have to deal with. Both the discharge points are discharging to atmosphere (into a tank with the inlet pipe above the top water level of the tank). The pump (P) is pumping water from a reservoir (R) to two discharge points (B and C). After doing so we will compare our results by modelling the same system in WaterGems and try to find if our manually derived results are correct.Р”В¬onsider the system depicted above. However in this article we are going to look into solving such a system manually without the aid of a network modelling software. Generally for estimating the flows through branched networks we end up using hydraulic network modelling softwares like Bentley WaterGems, EPANET, KYPipe etc.

We will be using a result oriented approach by solving a working model of a system. In certain situations it may become extremely important to estimate the actual flows through each branch so as to ensure that the required demands at all the discharge points are truly being fulfilled. However, in reality, that may not always be the case.

Generally while creating our P&I diagrams we often tend to estimate the pipe sizes for such a network by considering the flow to be distributed equally in all the branches. We often have to deal with multi-branched pumping schemes where a single pump delivers fluid to more than one location at the same time.

Watergems pump definition