Environmental and economic issues are forcing the focus on energy management. This applies in particular to steam. But up to now, there has been no solution that allowed steam to be measured in a verifiable manner.
Currently steam is not subject to legal metrology controls since it is an unstable medium. It is difficult to traceably calibrate steam using a weighing scale. In other words, there are no clearly defined requirements according to the verification ordinance that stipulate measurement technology, accuracy and maintenance intervals.
Therefore, when it comes to distribution and invoicing, disagreements are almost inevitable. For this reason, steam consumers are calling more and more for a verifiable method of measuring steam, which is acceptable to both steam producers and consumers. Operators of steam generators are required by the conditions of emissions trading to account for the steam quantities produced in a clean and verifiable manner.
To calculate the steam mass flow rate, pressure, temperature and flow are measured. Three sensors are generally required, each of which has an inherent inaccuracy. This makes it difficult to predict the total system uncertainty under operating conditions. This is important, for example, in the auxiliary circuits in chemical plants, which were designed many decades ago to allow for high throughput and high rates of flow. Nowadays these circuits are often operated at the very low end of their operating range, which is completely different to the original design operating point. This can have a huge impact on the total performance of the measuring point, with unaccounted steam usage amounting to several thousands of rand per month.
Endress+Hauser can now offer customers a convenient all-round package for verifiable steam measurement. It consists of four parts:
1. Application-optimised measurement technology
Using the flow measurement principle of vortex shedding is ideal for the reliable and long-term stable measurement of volume flow in steam applications. This robust measuring principle is widely accepted. In addition to tried and tested measurement technology for pressure, temperature and flow, an external energy monitoring system from Endress+Hauser calculates the quantity of steam consumed. The cost-saving complete solution is universally applicable.
2. Real-life calculation of total accuracy for the entire measuring point
Endress+Hauser has now made it possible to calculate the maximum total uncertainty under process conditions, ie, even in unfavourable operating conditions which, experience has shown, result in maximum measured errors. This calculation takes into account all the factors relevant to the process that can influence the measurement error of the steam measuring point.
Using the solution, users receive a traceable calculation of the overall performance, of the steam measuring point, taking current operating conditions into account.
3. On-site calibration to guarantee verifiable measurement results
All Endress+Hauser sensors are calibrated prior to delivery using accredited calibration rigs. The company is also an independent calibration partner, accredited in accordance with ISO/IEC 17025 for providing onsite calibration services for flow, pressure and temperature. To ensure that the theoretically calculated accuracy of the entire measuring point can also be verified on a practical level, it provides a continuous, on-site calibration solution for sustained testing of steam systems.
Each component can be tested by carrying out individual calibrations using traceable calibration instruments. Inline calibration for the flowmeter can be facilitated by short-term operation in a bypass. For pressure and temperature measuring devices and for the external calculator, traceable calibration instruments are used.
The onsite calibrations are carried out by trained and certified calibration technicians in accordance with SOP (standard operating procedures). Calibration logs provide the user with continuous verification of the calibration results and, for the first time, with a statement of the real total accuracy of the measuring point.
4. Verification without removing the measuring device
The company also offers its FieldCheck test and verification tool. This monitors and verifies Endress+Hauser flowmeters while they are installed, without any disruption to the process. This solution is the first of its kind to enable inline verification directly during operation – a huge advantage for steam producers.
What makes the solution stand out from the rest? Endress+Hauser believe it is the ability to carry out traceable calibration and process checks. Most importantly, as an accredited calibration service provider with verifiable on-site calibration capability, it is well positioned to do this.
Tangible results
Endress+Hauser was requested by a well known energy supplier to assist in finding a solution to avoid regular discussions with their steam customers. The customers were querying the measurement technology and the measuring solution. The invoiced amounts were allegedly much too high. With E+H’s solution, they were able to prove using traceable standards that the measurements were correct. The feedback confirmed that the solution deals effectively with all of the points necessary to verify optimum performance, starting with the measurement, including uncertainty calculation and regular testing during operation.
Endress+Hauser is now in a position to assist customers in ensuring that unnecessary disputes are avoided when it comes to the invoicing and balancing of steam.
For more information contact Evan Dent, Endress+Hauser, +27 (0)11 262 8000, [email protected], www.za.endress.com
| Tel: | +27 11 262 8000 |
| Email: | [email protected] |
| www: | www.endress.com |
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