Electricity + Control February 2019

SENSORS, SWITCHES + TRANSDUCERS

Improved interface level measurement in polyolefin plant Magnetrol ® reports that one of the largest polyolefin pro- ducers in Germany faced a complex interface measurement challenge. The polyolefin plant had a vessel with a mixture of benzene and water. Benzene, an aromatic hydrocarbon that is an important constituent in gasoline, has a very low dielectric constant (low conductivity), which can be problematic for cer- tain measurement technologies. The level technology used in this case was a guided wave radar (GWR) transmitter mounted in a chamber on the side of the vessel. The chamber had the potential to fill completely and there was a tendency for the GWR to lose signal near the top of the probe due to the low amplitude signal produced by the benzene. Magnetrol ® assisted the polyolefin producer in solving the complicated issue of measuring a low dielectric constant. The challenge Outside of a sight glass, the GWR was the only level technology in the vessel. The existing GWR signal was being lost at differ- ent times of the day, including in the middle of the night, allow- ing zero remote visibility into the process and causing safety concerns due to potential overfill. Sometimes the signal was lost for hours and the only method of regaining it was to discon- nect the power supply and restart. During these periods of lost signal, a technician had to be sent out to the vessel, no matter the time of day or night, in order to physically view the sight glass. This occurred many times over an 18-month span, as the GWR manufacturer could not resolve the issues related to the top of probe impedance mismatch, adding substantially to the total cost of ownership Because of the failed GWR, the user considered moving to a displacer transmitter due to the historical reliability of the technology. However, a last opportunity was given to GWR by installing the Magnetrol Eclipse ® Model 706. The Model 706, with its specifically designed impedance matched chamber probe, has reportedly been performing flawlessly. The impedance matching allows for level measure- ment up past the process connection (100% level point), pro- viding overfill prevention and measurement in full chambers. It has eliminated maintenance and service time at the vessel and those inconvenient times when signal was lost. Supporting proof of reliability can be provided through Safety Integrity Level (SIL) documentation, such as certificates and FMEDA reports. Enquiries: Visit www. magnetrol.com of the device. The solution

Affordable and effective level sensors Val.co offers a range of affordable and effective level sensors that have applications across all sectors of industry, but that benefit, in particu- lar, the tank building and hydraulics industry. The Val.co range includes: small float switches, Linear-LC sen- sors, limit level switches for side installation, multipoint and simple or double contact limit level switches. Five ranges Affordable, small float switches for lid or bottom installation for in- dustrial use are available in brass, stainless steel, polypropylene, PVC and PVDF. Combinations are available for use under aggressive conditions and have a parallel or conical thread connections in 1/8, 3/8 and 1/4. The Linear C range provides a comfortable continuous measurement based on proven float technology. An inte- grated reed chain with resistance circuit enables continu- ous monitoring of the level. Switching of tube lengths up to 2 000 mm enables affordable electronic measurement in large tanks. The OMNI-LC digital indicator provides for measurements to be displayed locally and in plain text (with background lighting). Vari- ous types of limit level switches for side installation include: • Type SML – stainless steel designed for contact with media with pressure resistance up to 30 bar. • Type NW1 – brass and stainless steel versions with NBR-butadi- ene with a stainless steel or PVDF float. • Type MW3 – micro switch variant with max 5 A switching cur- rent, electrical connection via DIN plug 43650-A or round pug connector M12x1. • Type NW3 – reed switch variant in brass or stainless steel with NBR-butadiene, stainless steel of PVDF float. • Type RW-HK – for internal or external installation in stainless steel. • Type MW1 – one of two micro switches, convenient for use as an advance warning contact or for monitoring of two close lev- els. Multipoint level switches are available for complex level monitoring, with tube length switching up to 6 000 mm and a plastic version up to 5 000 mm. The multipoint is used for distance monitoring of tanks that use up to six float stations. It offers additional application safety with temperature elements that can be optionally integrated in a switching tube to monitor the media temperature continuously. Effective limit level switches are supplied in a simple or double contact sensor in proven reed switch design. Again, these switches are available in stainless steel, brass, aluminium or PVC. In contin- uous operation they are temperature resistant up to >105 0 C. Op- tional switching functions as a normally closed (NC) or change-over contact make external voltage supply unnecessary. GHM Messtechnik, South Africa, managing director, Jan Grobler says, “The Val.co range complies with all international standards. The robust devices can perform in the most demanding conditions and are approved for explosion-proof ATEX Ex d – Ex i a, EAC and for naval use”. Enquiries: Jan Grobler, Managing Director, GHM Messtechnik South Africa,Tel. +27 (0) 11 902 0158 or email info@ghm-sa.co.za

Improved interface level measurement instrumentation resolved the costly level measurement challenge faced by the plant.

Electricity + Control

FEBRUARY 2019

29