Flameproof motors – A fresh start for low-voltage motors
Flameproof motor series of VEM
Safety is the top priority, especially in potentially explosive industrial zones. In order to meet the strict guidelines of the chemical and petrochemical industry, as well as of oil and gas production, the VEM Group is successfully proceeding with in-house production of the newly developed flameproof asynchronous motors.
Motors for implication in explosive zones
For decades, the VEM Group has been a reliable and sought-after partner of the gas, chemical and petrochemical industries worldwide. The “Ex eb”, “Ex ec”, “Ex tc” and “Ex tb” product groups, in particular, have established themselves for these challenging and demanding applications and demand for them is constantly growing.
Due to the growing demand from this customer group, the VEM Group has decided to extend its portfolio by adding an “Ex db (eb)” product group. The objective of the group of companies for this segment: To become the leading supplier of premium Ex-drives.
The production of the new Ex (db) motor series will expand the production capacities of the Wernigerode and Zwickau locations and will further increase their importance in the respective markets.
New development with many benefits
The “Ex db (eb)” type of protection is much more in demand outside Europe than the previously used protection type. In addition, the “Made in Germany” seal is known worldwide and stands for maximum safety, as well as for outstanding quality in Ex d products. As a German manufacturer for Ex d motors, the VEM group of companies was able to further consolidate some distribution channels and to improve relationships. The group has deliberately opted for predominantly German suppliers, who, for example, provide the main components. This ensures short and stable supply chains, enabling the VEM Group to manufacture and deliver in a timely and consistent manner.
The new motor concept has various other benefits for the operator. It is modular in design. Due to the modular principle used, these drives can be modified at short notice and with little effort. For example, a conversion from IM B3 to IM B35 can be implemented at short notice by installing a separately supplied flange ring whose dimensions can vary.
The basic concept of the series is that various modifications can be subsequently made to the motor without having to open the flameproof enclosure. For general modifications such as changing the position of the terminal box (e.g., to terminal box on the right) or the design, special Ex qualification is not required for the new VEM motor concept. As a result, specially trained personnel are not needed for these activities.
In addition, a lot of costs can be saved when setting up or operating a motor bearing. Due to its modular design, the asynchronous motor is ideally suited for this purpose, as only a basic model with corresponding add-on or conversion parts must be available. Additions can then be made on-site. This means that the motor can be modified to the customer’s needs at short notice any time. Thus, the “modular principle” also saves costs.
Withstanding the explosion pressure
Flameproof motors are urgently needed, especially in applications such as the chemical or refinery industry, where the atmosphere could be explosive, for example, due to gas. The new Ex (db) motors can withstand four times the maximum expected explosion pressure. For this purpose, the housing and the bearing shields have been designed to be strong.
The motor components have low manufacturing tolerances. This is due not only to the dangerous area of application, but also to what the motor is expected to do in the event of an explosion: Since a possible explosion inside the motor should not extend outwards under any circumstances, the resulting flame must be cooled down by the so-called ignition gap until it goes out.
Overcoming complex issues and passing the necessary certifications
Implementing the customer’s requirements posed a challenge to VFM that had to be tackled, as all aspects – from quality to safety and costs to production – had to be taken into account. The Ex db (eb) motors produced in-house had to undergo lengthy procedures to prove themselves and finally get market approval. The tests included:
- determining the maximum expected pressure (at -40°C)
- four-times pressure test (IBExU)
- protection class test IP6x (for use in zone 21)
- heating test (VEM)
- ignition gap test (IBExU)
- impact test (IBExU)
In addition, the quality and safety certificate had to be extended so that motors of the protection type “flameproof enclosure” could be manufactured in-house.
The motors successfully passed all the tests, so that VEM can take over and run the complete production. The VEM Group also had to ensure serialisation of components and batch tracking. As the motor is suitable for the construction of motor bearings on the basis of its “modular principle”, a new post was created in the group of companies as a result. This was done to guarantee optimal tracking and maintaining inventory of the modules.
VEM has maintained relations with the chemical industry for several years. Until now, however, the group of companies could distribute only third-party products licensed for resale. For this reason, the group was previously not perceived as a manufacturer, but solely as a supplier of Ex (db) motors. This image will be actively changed by the new drive solution. Due to the high quality and the outstanding results in all approval tests, the group of companies is positive about the future and is sure that it will be able to establish itself as a manufacturer of Ex (db) motors.
Exciting processes after the starting signal
As soon as the project was underway, the VEM Group was able to prepare a specification together with the design and sales departments, which in turn helped to set up the development team and define the concept. Here, important issues had to be clarified first, for example, how the group of companies wanted to establish itself as a manufacturer of Ex (db) motors, how these could be made better, and the strength of the market competitors. From the very beginning, it was clear that new cross-departmental structures would have to be established for the series. In order to establish a solid basis for the motors, a great deal of emphasis was placed on design and engineering at the beginning, due to the planned new development of the motors. The design department quickly defined precise tolerances for gap dimensions and necessary wall thicknesses.
In order to establish optimal communication between the departments, new departments were included in the process month after month. Thus, the costing department was needed to define the design of the motors (W43R). Likewise, the engineering department was included to evaluate the manufacture of the components or to request new fixtures. The purchasing department was responsible for supplier qualification for the new models and purchased parts, such as the wire bushings. The quality assurance department also had to compile various documents for the new series, while the testing department put all its energy into preparing the heating and type testing. The assembly and engineering departments were soon able to start prototype production and then series production. The mechanical production department was responsible for testing and measuring the new components, since the tolerances for motors are tight and precise and accurate production of all small parts is necessary for optimal operation. The logistics department was entrusted with the storage and transport of the new Ex (db) components.
After passing many tests successfully, the VEM Group was able to launch the newly developed motor series at the end of 2020. At the same time, sample motors were supplied to a major customer in the chemical industry. These are currently undergoing a very successful qualification process for the motor concept.
Special flameproof motors with special design
The new series had to undergo strict tests and meet stringent guidelines, not least because of the special area of application. The constructions are designed to work without faults in temperature ranges from -40°C up to +55°C. In addition, all requirements for the safe handling of combustible dusts and for designing protective measures against dust explosions had to be met in order to obtain approval for dust Ex (tc / tb) in protection class IP65. The VEM Group worked hard to bring the motors up to the current maximum efficiency levels IE3 and IE4 and to comply with the VIK recommendation.
The entire basic concept of the machine had to be developed, at best, based on the series parts in order to achieve the desired “modular principle”, since the active parts, as well as the lip contour and the bearing system, come from one series. By using the same material, it was possible to transfer all the advantages of the W43R series to the new components.
The idea of being able to swap mechanical components depending on the interface also required some modifications – due to this, for example, feet, flanges, terminal boxes, fans and fan covers can now be swapped based on customer requirements. All structural strength certificates for the expected explosion and the resulting test pressures had to be obtained promptly and successfully. Another concern was the promise of short delivery times, for which some parts of the existing value chain were restructured. This ensures short delivery channels and faster delivery times, as overseas transport of components is virtually eliminated.
In addition, the housing has been designed with 4×45° baseboards and can also be used for motors where the terminal box is on the N side (Y design). Serialisation is also a special step for the VEM Group, as the traceability of components must be guaranteed. Production within tight tolerances and the measurement of clearances relevant to Ex d are special features that the group of companies accepts gladly and enthusiastically to be able to provide the best for their customers.
Outstanding sales launch for VEM
Due not least to the commendable and committed efforts of all those involved, from design to testing, it was possible to implement an entire series production on schedule. Two models were already approved for sale last year, and five more will follow in 2021. The steady demand for motors of the new series proves the foresight of the VEM Group. Thus, the Group was able to book the first customer orders directly on the first day after the series was launched. Approval by the existing customer from the chemical industry has also already started. A larger order for 24 Ex (db) motors was placed by VSK (Worms), one of the established maintenance companies in the chemical industry.
VEM-Group website, 4th December, 2022