Flow Level Pressure 41


Figures 4 and 5. Unlike Figure 2, where the level signal was not influenced by any other signals on the probe, Figure 4 shows that there is an impedance mismatch at the top of the probe that can influence the level signal as it rises into that area. Figure 5 shows the level signal actually lost before reaching the process flange.


Figure 6


As explained above, this adverse interaction is application/installation dependent, but is always a concern nonetheless. Because of this, standard GWR single rod probe designs cannot be classified as overfill safe.


However, by properly matching the single rod probe to a cage/chamber, the impedance mismatch, and the corresponding adverse effects, can be eliminated. By utilizing the cage as the second conductor, a properly sized and installed single rod can yield overfill safe performance.


Caged Coaxial Probes


The ECLIPSE Model 706 broad offering of caged probes combines the performance/sensitivity advantages of a coaxial probe and the viscosity immunity of a single rod probe. Unique to Magnetrol, the caged GWR probe is a single rod probe which uses an existing or new


cage, bridle, or stillwell as the second conductor to re-create the same signal propagation of a coaxial GWR probe. Caged GWR probes are designed for 2” (DN50), 3” (DN80) or 4” (DN100) diameter chambers and utilize a specially designed impedance matching section that results in the same overall characteristic impedance of a coaxial style GWR probe. Caged GWR probes offer the same sensitivity and performance as coaxial GWR probes, but the single conductor design allows it to be used in applications with viscosities up to 10,000 cP.


Figure 7


As shown in Figures 6 and 7, these probes allow the ECLIPSE Model 706 to measure accurate levels up to the process flange without any non-measureable zone at the top of the GWR probe, and their signals look very much like those of a coaxial probe.


Summary


Overfill safe GWR probes are unique to Magnetrol and ECLIPSE guided wave radar transmitters. Instead of using algorithms to infer level readings in uncertain areas of a GWR probe, Magnetrol takes pride in the innovative design of probes so that actual, true product level can always be measured.


A New Member in the Family of Modular Level Meters


Krohne, Inc. (The Netherlands) have introduced the OPTIWAVE 5200 C/F, a new 10 GHz FMCW radar level meter for liquid applications in up to a 30m / 98 foot measuring range. The cost effective 2-wire loop powered device measures level and volume in storage or process tanks with process conditions up to 250°C / 482°F and pressures up to 40 bar / 580 psi. for general purpose or hazardous locations. (Class 1/Div 1) Together with the recently launched OPTIFLEX 2200 C/F TDR level meter, the OPTIWAVE 5200 C/F has been designed and developed for use in SIL 2 safety-related systems according to IEC 61508.


The OPTIWAVE 5200 C/F electronics are compatible with a wide selection of antennas. The unique PP and PTFE Wave Horn antennas are process sealed by their antenna material instead of a traditional process seal construction with “O” ring gaskets. These gasket free antennas are ideally suited for extremely corrosive environments. The PP antenna can be mounted on process connections as small as 1 ½ inch. The metallic horn and waveguide antennas use a dual seal mechanism, which is a combination of “O” ring gaskets with Krohne's unique Metaglas process interface design, for a completely hermetic seal in highly toxic or explosive applications. Metallic horn antennas range in sizes from DN 80…200 / 3…8”.


The modular design of the housing with its unique bayonet locking system and antenna extensions ensures suitability for a variety of mounting positions and applications. To make the display screen easy to read, the quick coupling system permits 360° housing rotation. The housing can also be removed under process conditions. The remote converter version OPTIWAVE 5200 F features full display and configuration capability up to 100 m / 328 feet away from the antenna.


Fully compatible with all installed KROHNE BM 70 flange systems, this new meter can also upgrade any BM 702 radar level meter with enhanced measurement performance and features and is compliant to newer requirements such as SIL and NAMUR guidelines. This new unit offers 4…20 mA with HART communication and PACTware DTM’s at no extra charge.


Reader Reply Card No 133


Flow Rates Checked in Suspension


The KDF/KDG low-volume flow meters or monitors by KOBOLD Messring GmbH (Germany), enable low flow rates to be checked reliably and cost- effectively. The devices, which operate according to the suspended float principle with a stainless steel ball that floats in the media flow, come in special designs for fluids and for gases (air). The devices with stainless steel housing are installed vertically, with a flow direction from bottom to top, using 1/4” threads or 8-mm-diameter hose clips. A needle valve allows the media flow to be set such that the measuring ball is positioned for optimum suspension. It is quick and easy to read off the respective flow rate by directly consulting the measuring tube made of robust borosilicate glass.


The version for fluid KDF media has 9 measuring ranges for water from 0.25– 2.5 l/h to 16–180 l/h. With 15 measuring ranges, between 0.5–5 l/h and 500–5000 l/h for normal air, KDG flow meters can be used for many applications. Ring initiators can be fitted optionally as limit-value transmitters, enabling preset flow rates to be monitored contact-free from the outside.


The devices with upstream or downstream differential pressure regulators are a simple and practical means of maintaining constant flow rates. The robust, stainless steel housing contains a valve with a FPM or PTFE membrane, which ensures that the flow rate on the relevant side is maintained within the preset range.


Reader Reply Card No 135


A Major Advance in Non-Invasive Pipe Flow Monitoring


Pulsar Process Measurement (UK) have launched Flow Pulse, a compact and cost-effective pipe flow monitor that promises exceptional repeatability, accuracy and simple installation with no down time. Flow Pulse is perfect for monitoring flow rate in fluid distribution systems, for pump efficiency checks, in process plant or sewage pumping stations.


Flow Pulse is a leap forward in flow measurement and in ease of installation - no need to break into a pipe, or to get any engineering involved, just clamp a small sensor to the outside of a pipe and immediately get a reliable, repeatable flow measurement (tools required = one screwdriver). Virtually no installation costs, no interruption to service, clean and simple.


Flow Pulse uses a novel spread spectrum analysis technique never before used in flow monitoring. It introduces a radical new Digital Signal Processing approach for exceptional repeatability:


Ultrasound is fired through the pipe wall at 90 degrees to the flow via a tangentially mounted high-output ceramic, then refracted at angles across the axis of the flow and subsequently reflected from bubbles, particles and vortices in all directions and at a wide range of frequencies. The wide, refracted, ultrasonic beam maximises the ultrasound energy that could be captured from flowing particles. These multiple reflections are received back into the unit via a second crystal.


The mass of data generated is analysed using Flow Pulse’s Refracted Spread Spectrum Analysis (RSSA) digital signal processing platform to derive flow information. RSSA analyses and integrates the received signals over a wide frequency range, then slices them for real-time analysis and flow rate calculation.


Flow Pulse operates in a flow range from as little as 0.3m/s through to 4m/s, with a minimum particle size of 100µ and concentration of 200ppm or above (the equivalent of hard water).


Pipe material can be rigid plastic, stainless steel, mild steel or cast iron. Corrugated pipe is not an issue and even light corrosion will give a good result. Flow Pulse provides repeatability and accuracy of around ±5%.


Reader Reply Card No 134


APRIL / MAY 2013 • WWW.PETRO-ONLINE.COM


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