This is precisely what verification and assurance measurements are for. Each answers a different question, but both are based on real data and a precisely defined measurement methodology.
The importance of cooling is also highlighted by the current situation in Europe. High temperatures, drought and the associated adverse hydrological conditions can lead to restrictions on power station output. This year, for example, power stations in France, Hungary and Romania have faced similar problems. The Czech nuclear power stations at Dukovany and Temelín are in a different situation thanks to their use of a closed cooling circuit with cooling towers – their operation is not dependent on the current water level in a watercourse in the same way as power stations with flow-through cooling.
The importance of cooling is also highlighted by the current situation in Europe. High temperatures, drought and the associated challenges… However, this does not mean that the issue of water availability does not need to be addressed. Quite the contrary. Changing climatic conditions increase the importance of long-term preparation – from understanding the actual condition and performance of the existing cooling system to planning its further development in good time. For example, an even more efficient system is planned for the construction of the new Dukovany units.
In the energy sector, a simple principle applies: it is better to be prepared for changing conditions before they start to restrict operations. Knowledge of the capabilities and limitations of a specific facility is one of the prerequisites for responding to such a change in good time. Associated adverse hydrological conditions can even lead to restrictions on power station output. This year, for example, power stations in France, Hungary and Romania have faced similar problems. Thanks to their use of a closed cooling circuit with cooling towers, the Czech nuclear power stations at Dukovany and Temelín are in a different situation – their operation is not dependent on the current water level in a watercourse in the same way as power stations with run-of-river cooling.
Only the measurements will reveal the true situation
A cooling tower changes over the course of its operational life. The heat exchange surface gradually becomes fouled, leading to a deterioration in its performance. Verification measurements are used to assess the current condition of the cooling tower. Based on the measurements and analysis of the technical data, it is possible to identify bottlenecks and explore ways to improve the efficiency of the plant’s operation. Warranty measurements serve a different purpose. They verify whether the equipment meets the technical parameters guaranteed by the supplier. They are carried out on new or refurbished equipment where there is a need for independent verification that the guaranteed technical parameters are met.
As Jitka Hlavová, Director of the Thermal Engineering and Energy Division at ORGREZ, says: “How well a cooling tower operates has a significant impact on operational costs. Over time, its performance parameters may change, for example due to fouling and, consequently, a change in the size of the heat exchange surface. By carrying out measurements, we can verify its current condition and provide the operator with data for any necessary operational optimisations.”
Verification before the repair, and verification of the warranty afterwards
The difference between the two types of measurement is clearly illustrated by the ČEZ Dukovany Nuclear Power Station. Measurements were carried out on the cooling towers there both before and after repairs. The verification measurements made it possible to assess the condition of the equipment prior to the work, whilst the subsequent warranty measurements confirmed its parameters once the repairs had been completed.
We are carrying out verification of the guaranteed parameters of the cooling towers at the Jaslovské Bohunice nuclear power station. We have already completed two of the guaranteed measurements; the final, third one is due to take place this September.
Other recent projects from this spring include Unipetrol Litvínov. This was, once again, a warranty measurement. Whilst each of these sites has different operating conditions, they all share the common feature of independent verification of the contractual technical parameters.
Measurements begin even before the first sensor is installed
In the case of guarantee measurements, the key document is the guarantee measurement project, which clearly defines in advance the conditions under which the measurements will be carried out and how the measured data will be evaluated. It also specifies which quantities and parameters will be monitored, thereby establishing a clear framework for the subsequent assessment of compliance with the guaranteed parameters.
The project includes, amongst other things, the terms and conditions and the test schedule, the standards and measurement methods used, the measurement points and instruments, the method for evaluating contractual values and guaranteed parameters, correction curves, staffing arrangements, and requirements for cooperation between the client and other contractors.
In the case of a guarantee survey, the project is approved by both the client and the contractor. This means that, even before the survey begins, both parties are aware of the conditions, the methodology and the way in which the results will be assessed.
Preparation is also preceded by a site visit. It is necessary to familiarise oneself with the specific layout of the equipment and to identify the locations for installing the sensors. Alongside the positioning of psychrometers and temperature sensors, one of the key aspects of preparation is the method used to measure the cooling water flow rate.
Pipes or open channels? Each requires a different method of measurement
Depending on the scope of the assignment, the following parameters are measured on the cooling tower: inlet and outlet cooling water temperatures, cooling water flow rate, relative air humidity, air temperature, barometric pressure, wind speed and direction, and, where applicable, the power consumption of the cooling water pumps or fans in the case of fan-cooled cooling towers, or other parameters as specified in the assignment.
The technique used depends on the specific operational configuration. If the cooling water flows through pipework, a clamp-on ultrasonic flow meter can be used to measure the flow rate. In an open channel, a different technique is used – we have the OTT Qliner 2 ultrasonic float flow meter available – a mobile system for measuring flow rates in open channels.
All equipment is calibrated regularly in accordance with the calibration schedule or the requirements of a specific project. We use our own calibration laboratory to calibrate pressure and temperature sensors.
The weather also plays a part in the schedule
A measurement team of three to four members usually works on site. Depending on the size of the cooling tower and the scope of the assignment, setting up the equipment can take two to three days, and the measurements themselves take a similar amount of time. However, the schedule is also influenced by weather conditions. Measuring cooling towers is a seasonal activity and the tower’s performance depends on the outdoor environment; therefore, the measurements must be carried out under conditions that comply with the specified methodology. Even a carefully prepared schedule may not always be feasible – if, for example, it starts to rain, the measurements cannot be carried out under those conditions. We therefore factor in a time buffer when planning.
The sensors installed on the equipment are connected to a dedicated measuring unit in the measuring vehicle, where the data is recorded. Once the measurement is complete, the readings are also forwarded to the customer. Both parties thus have access to the same set of measurement data, which forms the basis for their expert assessment.
From measurement results to further decision-making
The result of a guarantee measurement is a technical report assessing compliance with the guaranteed parameters. In the case of a verification measurement, the conclusion depends on the specific terms of reference.
Both types of measurement have one key thing in common: they compare the expected parameters with reality. The design and technical documentation specify how the equipment should operate. Measurements reveal how it actually operates. For equipment whose efficiency affects the economics of the entire operation, knowledge of its actual condition is a vital basis for planning future operations and investments. The measured data can lead to subsequent operational optimisations aimed at increasing the equipment’s efficiency, to modifications to the equipment, or serve to verify the results of an investment that has already been made.