In the oil and gas industry, in gas odorization and in the energy industry, it is often necessary to add liquid components in extremely small quantities in proportion to a variable reference value. For example, working with natural gas, biogas and liquefied petroleum gas, which are odorless but also potentially dangerous, means relying on substances with the strongest possible odors, such as mercaptans or tetrahydrothiophene. In order to allow this medium to be metered with extra precision, European market leader LEWA equips its own odorizing systems with hydraulically actuated, electromagnetically driven micro-metering pumps from the MAH, MBH and MLM series.
Intermediate size developed for MAH series
The Leonberg-based manufacturer has now expanded its portfolio to adapt to recent developments. “After receiving more and more frequent requests for gas volumes of about 15,000 Nm³/h in the last few months, we decided to design an intermediate size for gas networks up to PN 16,” explains Walter Richter, Sales Manager for Gas Odorization at LEWA. “The MAH 4 closes a series gap between the MAH 3 and the MAH 5.” This area was previously covered by the larger MLM 15 pump, which has a stronger stroke solenoid but presents a less cost-efficient solution. It was necessary to rely on the larger unit, as the MAH 3 only reaches a maximum delivery rate of 175 ml at a required pressure of 16 bar. For the MAH 5, this value is 600 ml, but the maximum possible discharge pressure is only 10 bar. “In contrast, the newly developed MAH 4 can odorize gases in the delivery range from 200 – 350 ml at the necessary higher pressure,” Richter says.
Like all solenoid-driven diaphragm metering pumps from LEWA, the MAH 4 also consists of an electromagnetic drive with stroke setting, a pump head with metal diaphragm and a control system contained in a separate housing. “The metering pump is actuated with pulses,” explains Richter. “The discharge stroke is executed by the armature of the magnet. The suction stroke takes place after switching off the electrical pulse using the force of the thrust spring.” The pump is particularly robust and reliable. Operating it incorrectly does not cause damage. Instead, for example, an overload—perhaps due to a closed valve in the discharge line—merely leads to stalling the magnet, as its force is limited. “A closed valve in the suction line would cause maximum cavitations,” Richter says. “After the faults are remedied, the pump continues pumping—just like that.”
Under the same boundary conditions, the MAH 4 stands out for its metering accuracy of ± 1 percent and, thanks to the wide control range up to 1:1,000, its outstandingly high metering flexibility. Furthermore, its design is absolutely odor-tight and leak-free, making it safe for dry runs with high process reliability. The new intermediate size only differs from the trusted MAH 5 in that it has a different inner diameter for the plunger and bushing. Both dimensions were reduced from 5 to 4 mm.
Odor control system with additional functions
In addition to expanding the pump area, LEWA has also reworked the control system that monitors and regulates odorizing systems continuously and completely automatically. It now features an additional totalizer for pump strokes, which can also be queried using MODBUS RTU. Communicating over this protocol allows a delayed response of 0 – 250 ms to be set in the new version. By making these changes, the manufacturer is responding to increasing requirements while also enabling better integration into customer systems as well as easier data exchange between the CPU of the odor control system and the control infrastructure on site. There are additional features, such as indirect monitoring of gas traps for OD 7 and OD 8 odorizing systems using an existing filling level sensor, not to mention additional software for operating two to three gas meters in sequence. This program gives the customer various options. “The number of meters can be determined by the customer. They can be operated in parallel or in series as well as monitored in series,” explains Richter. “If, in the latter option, the meters indicate equal values—the deviation can be configured as a percentage in our system—only one gas meter is used as the reference value.” The result is that meter signal evaluation is further optimized.
The MAH 4 and the revised odor control system will be presented at this year's GAT/WAT in Berlin together with the removable injection nozzle for biogas, natural gas and liquefied petroleum gas odorizing systems.
For an initial discussion and specific questions about LEWA odorizing systems and all new products, Walter Richter, Sales Manager of Gas Odorization at LEWA, will be available in Hall B, Booth D-14.