Why Monitor Pumps
Pumps are the most over looked piece of machinery in all industries. They are critical to the smooth operation of the plant but are run constantly with minimal care about their performance. In general, the only time action is taken is when the pump fails.
Pumps currently account for 10% of the world’s total electricity consumption with the majority of the life cycle costs (85%) of a pump being related to the energy spent in pumping. The rest (15%) is related to the purchase (5%) and maintenance of the pump (10%). Data from Grundfos Pumps*.
The Benefits of Pump Monitoring
- To find out what your pumps are doing now
- To make improvements to your pumping asset to save energy
- To reduce pump maintenance costs
The pump monitoring equipment can monitor your pumps continuously, recording data at fixed intervals of time or on changes to the system. The pump operator can view in real-time pump performance parameters, helping them to make informed decisions about the operation of the pumping system. The data can be analysed to detect changes in performance and actions taken to restore performance back to optimum.
The Thermodynamic Technique
The majority of losses due to the inefficiency of a pump are transferred to the fluid being pumped in the form of a rise in temperature between the inlet and outlet of the pump. The Thermodynamic technique makes use of this fact by measuring the losses across a pump to determine its pump efficiency.
The table blow shows the difference between the Conventional and the Thermodynamic methods of measuring pump performance parameters.
Advantages of the Thermodynamic Technique
- Pump efficiency can be accurately determined on-site
- Accuracy is not sensitive to pipe work configuration
- The equipment is easily installed
- Pump Tests can be carried out with the minimum of disruption to operations
- Pump efficiency is determine irrespective of a flow meter
- Pump efficiency is calculated to an uncertainty of better than 1%
Thermodynamic Pump Testing
A thermodynamic pump test can be carried out within an hour with minimal disruption to the operation of the pump. The pump test measures the current operating point of the pump at various pump heads and flow rates, allowing a new set of pump curves to be draw for the pump. These curves establish a baseline for the pump monitoring program.
To obtain the new pump performance curves, the pump needs to be throttled. The chart opposite shows how the pump is throttled at various points along the pump head / flow curve. Depending on the size of the pump and system conditions, it is necessary to wait for the new operating point to stabilise before data is recorded. A standard pump test records up to 5 test points, each at a different pump head / flow.
In cases where the pump can not be throttled, a single test point is recorded at the working operating point.
Operating Point not at BEP
Using thermodynamic pump monitoring equipment, the exact operating point of a pump can be identified. The charts below show the current operating points of the pumps compared to their as new pump curves. In all three cases, the current best efficiency point (BEP) is not at the manufacturers original BEP point. This is wasting pumping energy and causing excess wear to the pumps!