When Should You Specify High-Pressure Pumps
In our next two blogs, we’re going to be focusing on pump station technology. For this blog, we’re going to look at calculating your pump needs, and specifically, how to know when the demands of the job justify changing to a high-pressure pump.
We will also present two of our most popular high-pressure pumps, the BAKER-FLOW and BAKER-BLOC, which can produce pressures of up to 40 bar, and consider the features, relative merits, and suitable applications of both.
Calculating Pump Needs: What You Need to Consider
There are 2 key aspects to consider when determining whether a standard pressure pump is sufficient for a positive pressure, closed-loop application, or there must be an upgrade to high pressure pump. But before we delve into this, it is first important to understand the various definitions of pump pressure.
The pressure of the system when there is no fluid flowing, that is when the system is static. The static pressure at the inlet of a pump should always be considered especially when there is a high positive pressure to the inlet of the pump, or when it has over 80m of vertical pipe on the pump suction.
Maximum Working Pressure
Maximum Working Pressure is the limit the pump can be subjected to. When designing a pumping system, the static pressure should always be considered to ensure it doesn’t exceed the maximum working pressure of the pump. In building applications, this is typically necessary when there are more than 20 standard floor levels of pipework above the pump, that is the calculated pressure at the pump inlet is over 800kPa. It is commonly detailed in HVAC & Fire specifications that for systems with a design pressure ≤ 500 kPa, the pump casing minimum static test pressure shall be 1.6 MPa. This invariably covers the majority of installations. For systems with a design pressure > 500 kPa, the pump casing minimum static test pressure shall be 1.6 MPa or 1.5 times the total of the pump shut-off head plus the static and system pressures, whichever is the greater.
The pump must strictly NOT be subjected to a pressure exceeding the Max Working Pressure.
Hydrostatic Test Pressure
It is important not to confuse Test Pressure with Working Pressure. Test Pressure is generally a minimum of 30% greater than the Max Working Pressure of a pump. It is the pressure the pump was tested at in the factory for a limited period to ensure it will withstand its advertised Working Pressure for the duration of its lifetime. It is strictly a factory test by the manufacturer only.
The pressure the pump will deliver at, relative to the flow rate as per its performance curve.
Closed Head Pressure
The “head height” or “total head height” of a pump is the maximum height at which it will cease to produce flow, or the point at which no water will emerge from the pipe. Interestingly, head height is not affected by the density of the liquid or by the diameter of the pipe, although both of these factors will affect flow.
Flow refers to the volume of liquid that passes through a given point in the system. The higher up the water has to reach, the lower the flow will be. The terms “Head height” and “vertical lift” are used to refer to the height at which the flow equals 0.
Friction also needs to be accounted for. As water is pumped through the pipe, it creates friction, causing resistance and negatively affecting the flow.
To summarise, when deciding on a pump station for a given application, you will need to consider the height to which the water needs to be delivered and what the flow needs to be when it gets there.
The 2 key aspects therefore are static pressure, and the pump working pressure. The standard range of BakerFlow and BakerBloc pumps are designed and manufactured with a max working pressure of 1600kPa, with the exception of several models which at the time of this article, are currently suitable for 1000kPa (please contact our office for further details).
This relates specifically to the materials used in the construction of the pump. If the pump is to be subjected to higher than 850kPa pressure, it may be necessary in some instances for the mechanical seal to be upgraded.
Beyond 1600kPa static pressure, Masterflow manufacturers a high pressure range of its BakerFlow and BakerBloc range. The “D” series is available to suit pressures of 2100kPa and 2500kPa and requires the materials of be ductile iron instead of cast iron, and high-pressure seals. The pump casing also includes additional ribbing.
For the 2500kPa – 4000kPa range, the “S” range is available and is in stainless steel construction.
There are many installations of “D” series pumps across Sydney, Melbourne, Brisbane, and Perth. The “S” series are much less common but have been installed in various mining applications in QLD and commercial projects such as Lonsdale St Melbourne and Barangaroo Sydney.
Contact Masterflow Today
You can speak to a member of our expert team of engineers about our range of high pressure pumps. To further discuss selecting the right pump and materials for your application, call us on + 61 2 9748 2022 or send us a message online.