Water / Wastewater 47
a metal diaphragm, and forward the result in temperature- compensated and standardised form to the data logger. A customer-specifi c design was developed for this project: The transmitter is designed for a line pressure of up to 600 bar, which corresponds to a sea depth of 6,000 m. At the same time, pressure differences with an accuracy deviation of less than one thousandth of a bar can be measured. Specially designed for use on the seabed, all parts that come into contact with the medium are made of Hastelloy C-276 to prevent corrosion damage by salty seawater. In addition to this, the pressure connections can be expanded with two pipes on request, so that the transmitter inserts perfectly into the overall construction.
The new instruments for marine geology look set to be a complete success, in no small part thanks to the solid cooperation between sensor developers and Dr Gennerich’s team at the University of Bremen. We at KELLER are also proud to have been able to make a contribution to science along the way. We wish Dr Gennerich and all other committed researchers much success in their future work. Thanks to their hard work, we will defi nitely soon have a better understanding of the elemental forces below us and will also be able to predict their behaviour a little more accurately.
Figure 3: The inner workings of the differential pressure transmitter © KELLER Pressure
other leads into a reference tank. The tank can also be opened to the outside environment via a valve. When submerging or retrieving the OBP, the valve is kept open so that the pressure is always the same on both sides and the sensitive sensor is not damaged. Once the measuring equipment reaches the seabed, the valve is closed. The content of the tank is now kept at exactly the same pressure as at the start of the measurement (P1). If the ambient pressure (P2) changes, the transmitter registers the difference. Pressure deviations in the reference tank due to temperature-induced material expansion are internally compensated for using a precisely calculated volume of quartz glass. In addition to this, the temperature is measured in order to subsequently calculate the remaining deviation mathematically. All measurement data are recorded using a data logger. While taking measurements, the system can be recalibrated at any time by opening the valve and remeasuring the zero point. In this way, any signal shift can be detected and compensated for later during the data evaluation. This design enables changes in the water pressure at the level of the seafl oor to be measured with the utmost accuracy and practically free of measurement uncertainties over long periods of time.
Piezoresistive pressure measuring cells to which pressure is applied on both sides are perfect for this purpose. Applying
pressure to both sides of the same diaphragm offsets most of the pressure’s effect and only the difference remains. This applies to both the measured value and the (one-sided) strain on the silicon diaphragm. The silicon’s crystal lattice structure is extremely resistant to pressure applied evenly from both sides, even within very thin walls, as is required for highly sensitive measuring cells.
The OBP prototype’s sophisticated measuring system requires reliable and precise sensors. KELLER’s PD-23 differential pressure transmitters meet all requirements for this application and are therefore perfectly suited to it. They measure the pressure difference on a single silicon diaphragm, which is separated from the measuring medium on each side by
Figure 4: 3D CAD illustration of the custom-made differential pressure transmitter @ KELLER Pressure
Author Contact Details Anatol Straub, Digital Marketing Specialist • KELLER Pressure • Address: St. Gallerstrasse 119 • Tel: +41 52 235 25 25 • Email:
info@keller-pressure.com • Web:
www.keller-pressure.com
Chlorine generation – a simple and reliable solution
Euro-Gas’ GazCal Gas Generator provides a simple and effective solution for generating Chlorine (Cl2) gas. The GazCal Gas Generator overcomes the traditional diffi culties associated with handling Chlorine gas cylinders, such as problematic accuracy and erratic shelf life.
The rugged, portable and battery-operated tool is designed for use in a wide range of industries, including the water treatment sector, where personnel face the challenges of testing and calibration. The GazCal comes in a robust and compact carrying case and allows for rapid testing and calibration with negligible warm-up time. This simple-to-use device can be operated by anyone, requiring only the necessary PPM level to be set via the unit’s dial-up digital display.
The GazCal generates Cl2 levels ranging from 0.5 – 20 ppm and is also suitable for use as a surrogate for the cross-calibration of O3, ClO2, COCl2, HF and F2. Its design overcomes the problem of short shelf life. The cell life is only used up when the unit is in operation, while traditional cylinders can simply die out before 6 months. The generator can last for up to a decade, often without the need to change the cell and requiring only a yearly recertifi cation of calibration.
The GazCal cell can operate for up to 500 parts per million (ppm) hours, which is equivalent to a continuous usage of 100 hours at a concentration level of 5ppm. This extended lifespan allows for a minimum of 400 calibrations to be conducted. The device includes a cell life indicator that displays the remaining life of the generating cell, enabling operators to plan ahead. Installing a new generating cell is a simple process once the current cell has been depleted. Although the GazCal generator may have a higher initial cost compared to a small cylinder, it is a more cost-effective option in the long run.
Also, unlike gas cylinders, which only attain one specifi c concentration per cylinder purchased, the GazCal is entirely adjustable between the 0.5ppm to 20.0ppm range and in 0.1ppm steps. The GazCal produces many different concentration levels from one device. In addition, low concentrations of Cl2 are effi ciently produced with the GazCal, even 1ppm and 2ppm levels, whereas it is extremely problematic to achieve cylinder stability at low concentration levels.
More information online:
ilmt.co/PL/67K6 For More Info, email:
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New standard provides test method for carcinogens in
water A new ASTM International standard provides a test method for fi nding low concentrations of nitrosamines, a suspected type of carcinogen, in water. The standard (D8456) was developed by ASTM’s water committee (D19).
Nitrosamines exist in low concentrations in water, foods, vegetables, and dairy products. According to ASTM International member William Lipps, this standard presents a relatively easy measurement technique for nitrosamines. “Since nitrosamines are water-soluble, water testing labs can use the standard to check for them in water matrices,” says Lipps. “Manufacturers and labs testing consumer goods and foods can also use the method to test for trace nitrosamines.”
The new standard is also a move forward in sustainability for this form of water testing. “This method decreases required sample volumes, compared to other nitrosamine methods, thus lowering the carbon footprint, and requires a signifi cantly smaller volume of solvent,” notes Lipps. “It also does not use hazardous solvents such as methylene chloride, and it requires limited consumables.”
60049pr@reply-direct.com
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IoT STARTS WITH A SENSOR
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