Instrumentation specialist, Endress+Hauser, has a successful 25-year track record in the flow calibration market. The company's success can be attributed to three factors, namely its five internationally accredited and leading edge calibration centres, its customer-centric approach, and its focus on international quality accreditation.
According to Endress+Hauser flow product manager, Romeo Rocchetti, the success of Endress+Hauser in this field is the result of a sustained strategy that encapsulates these three aspects. "Customers demand quality products and exceptional service, both pre- and post-purchase. Our high quality products that conform to international standards and our ability to offer the best calibration services anywhere in the world, form the basis of our service and consultative offering."
Flow calibration systems need to be precise, dependable, offer cost effective controlling and balancing, and ensure precise fluid inventory and cost allocation in custody transfer applications. This is achieved though long term stability and guaranteed, traceable accuracy of flow measurement. Flowmeters in quality critical applications need to be checked periodically, tested, and recalibrated if necessary.
State-of-the-art testing facilities
Endress+Hauser's largest calibration centre situated in Cernay, France, prides itself on its state-of-the-art technology. The centrepiece of the facility is the 28 m tall water tower. The height of the tower, coupled with the overflow, ensures constant water pressure throughout the entire calibration process, which is vital to maximum metering accuracy.
With the help of seven centrifugal pumps, the softened water is pumped into a 25 m high intermediary tank. This storage tank serves to fully degas the water. The downpipe to the calibration facility has to be completely full at all times, so excess water is pumped back up to the header tank. The pumping rate is held constant between 5 and 10% above the rate of flow to the device under test. The excess water spills over a long overflow edge at a height of 24 m and flows back to the reservoir. This process ensures constant water pressure.
A water tower with constant water level and overflow offers many advantages in achieving stable conditions during calibration:
* Constant pressure conditions at the device under test throughout the entire calibration.
* No pumping pulsations in the flow.
* No inaccuracy of measurement throughout calibration caused by measuring the level or readjustment of the flow.
* No delay during calibration caused by refilling a measuring tank or water tower.
* Measurements of any duration can be conducted at defined calibration points. These tests are ideal for checking the long-term metering capabilities and stability on flowmeters.
The most outstanding feature of the plant is the fully automated calibration and linearisation function of its three weighing tanks (for 400 kg, 5 t, or 50 t). The control weights are permanently installed above the tanks and can be lowered mechanically when needed. Certified control weights in the form of stainless-steel cylinders are permanently positioned around the two large weighing tanks. This allows technicians to verify the functionality of the entire measuring chain as well as the linearity of the weighing part at any given time. All valves for ensuring measurement integrity have been integrated in duplicate. Sensors between the two valves detect leaks and immediately alert the plant control unit if problems arise.
A low electrical potential is applied to prevent mechanical influences affecting the measuring tanks during calibration. The measurement procedure is interrupted immediately if the tanks are touched. The highly complex calibration rigs are operated by specially trained experts and maintenance is handled by qualified personnel.
Internationally accepted standards
Globally, Endress+Hauser subjects all flowmeters to continuous quality checks throughout production prior to final testing, adjustment and calibration. This is done based on internationally valid standards.
The company employs leading edge metrology and automation technology at its flow calibration facilities in Cernay. The calibration centre is one of the most advanced of its kind in the world and relies on gravimetric calibration as its reference method. As an internationally active enterprise, Endress+Hauser bases the recognition of its products and testing procedures on international standards.
The centre is ISO/IEC 17025 accredited by the Swiss Accreditation Service (SAS) as a calibration laboratory for the 'flow' measured variable. Overall, accuracy achieved for this accreditation is better than ±0,05% on the complete rig, including all possible uncertainty factors. Accreditation constitutes official recognition of the company's engineering and scientific ability to perform a service defined in the certificate. Consequently, Endress+Hauser is in a position to perform certified and traceable calibrations within the ISO 9000 framework for its customers. Swiss Calibration Services (SCS) calibration certificates issued by Endress+Hauser are accepted by all ISO member states, including South Africa.
Being a recognised, accredited calibration facility does have its advantages. For the customer there is traceability back to national standards, such as, METAS, PTB, NMi, SABS/SANAS. Traceability ensures an uninterrupted chain of proof regarding the test equipment, from the test device to the hierarchically highest standard in each country (national standard). A further advantage is world-wide acceptance of the certification and periodic inspection by the national standard authority to ensure standards are being maintained.
For more information contact Romeo Rocchetti, Endress+Hauser, 011 262 8000, [email protected], www.za.endress.com
| Tel: | +27 11 262 8000 |
| Email: | [email protected] |
| www: | www.endress.com |
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