Flameproof encapsulated motors - restarting the low-voltage motors

Safety is the top priority, especially in potentially explosive industrial areas. In order to meet the strict guidelines of the chemical and petrochemical industry as well as oil and gas production, the VEM Group is successfully pushing forward the new development of its flameproof encapsulated asynchronous motors in its own production.

Motors for explosive applications

For decades, the VEM Group has been a reliable and sought-after partner in the gas, chemical and petrochemical industries worldwide. The product groups "Ex eb", "Ex ec", "Ex tc" and "Ex tb" in particular have established themselves for these demanding and rough areas of application and are enjoying increasing demand.

Due to the growing demand from this customer base, the VEM Group decided to supplement its portfolio with an “Ex db (eb)” product group. The aim of the group of companies in this segment: to become the leading supplier of premium Ex drives. Through the production of the new Ex (db) engine series, the locations in Wernigerode and Zwickau will expand their production capacities and become further important in the corresponding markets.

New development with many advantages

The type of protection "Ex db (eb)" is much more popular outside of Europe than the type of protection previously used. In addition, the “Made in Germany” seal is known worldwide and stands for maximum safety and excellent quality for Ex d products. As a German manufacturer of Ex d engines, the VEM group of companies was able to further consolidate some sales channels and advance relationships. The group consciously chose predominantly German suppliers who, for example, provide the main components. This ensures short, stable supply chains, allowing the VEM Group to build and deliver in a timely and consistent manner.

The new engine concept has various other advantages for the operator. It has a modular structure. Due to the modular principle chosen, these drives can be modified at short notice and with little effort. For example, a conversion from IM B3 to IM B35 can be achieved at short notice by installing a separately supplied flange ring, which can have variable dimensions.

The basic concept of the series is that various modifications can be made to the engine later without having to open the flameproof enclosure. For general modifications such as changing the terminal box position (e.g. in the right terminal box) or the design, no special explosion-proof qualification is necessary with the new VEM motor concept. This means that no specially trained personnel are required for these activities.

In addition, extreme cost savings can be achieved when setting up or operating an engine warehouse. Due to its modular design, the asynchronous motor is ideal for this, as only a basic version with appropriate add-on or conversion parts needs to be available. Additions can then be made on site. This means that the engine can be adapted to customer needs at short notice at any time. The “modular principle” therefore saves costs at the same time.

Withstand the explosion pressure

Flameproof encapsulated motors are urgently needed, especially in areas of application such as the chemical or refinery industry, where explosive atmospheres can occur, for example due to gas. The new Ex (db) motors can withstand four times the maximum expected explosion pressure. For this reason, the housing and the end shields in particular were designed to be very strong.

The engine components have a low manufacturing tolerance. This is not only due to the dangerous area of application, but also to the task that the engine is supposed to fulfill in the event of a possible explosion: Since a possible explosion in the interior of the engine should under no circumstances escape to the outside, the resulting flame must be cooled down by the so-called ignition gap to such an extent that it goes out.

Overcome complex obstacles and pass exams for necessary certificates

Realizing customer requirements presented VEM with a challenge to overcome, as all aspects from quality to safety and costs to production had to be taken into account. The specially manufactured Ex db (eb) engines had to prove themselves in lengthy procedures in order to ultimately achieve market approval. The tests included:

Determination of the expected maximum pressure (at -40°C)
Quadruple pressure test (IBExU)
Protection rating IP6x (for use in Zone 21)
Heating test (VEM)
Ignition gap test (IBExU)
Impact test (IBExU)

In addition, the certificate for quality and safety had to be expanded so that motors with the "flameproof enclosure" type of protection could be manufactured in-house.

The motors successfully withstood all tests, so that VEM can take over and carry out the entire production. The VEM group also had to take care of the serialization of components and batch tracking. Since the engine's "modular principle" makes it suitable for the construction of engine bearings, a new job was created within the company group for the occasion. This is intended to guarantee optimal tracking and inventory of the modules.

VEM has had relationships with the chemical industry for several years. So far, however, the group of companies has only been able to sell third-party products that are licensed for resale. For this reason, the group has so far not been perceived as a producer, but solely as a supplier of Ex (db) engines - this impression is actively counteracted with the new drive solution. Due to the high quality and the outstanding results in all approval tests, the company association looks positively into the future and is sure that it will be able to establish itself as a producer of Ex (db) engines.

Exciting processes after the starting signal

As soon as the project got underway, the VEM Group was able to create a specification sheet together with construction and sales, from which the development team and concept development emerged. Important issues first had to be clarified, for example how the company association wanted to establish itself as a manufacturer of Ex (db) engines, how they could be made better and how strong the competitors were in the field. It was clear right from the start that new cross-departmental structures had to be set up for the series. In order to create a solid basis for the engines, the start was primarily focused on construction and technology due to the planned new development of the engines. The design quickly and precisely defined 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. The calculation was needed to define the design of the engines (W43R). The technology was also addressed, which should evaluate the production of components or request new devices. Purchasing was responsible for supplier qualification for the new models and purchased parts, such as the wire cable bushings. Quality assurance also had to put together various documents for the new series, while the test department put all its effort into preparing the heating and type testing. Assembly and technology were soon able to begin prototype production and series introduction. Mechanical production was responsible for testing and measuring the new components, as the tolerances for engines are tight and precise and precise production of all small parts is necessary for an optimal process. Logistics was also entrusted with the storage and transport of the new Ex (db) components.

After successfully passing many tests, the VEM Group was able to go on sale with the newly created engine series at the end of 2020. At the same time, sample engines were delivered to a large customer in the chemical industry. These are currently undergoing a sometimes very successful qualification of the engine concept.

Special pressure-resistant motors with a special design

The new series had to withstand extreme tests and strict guidelines, not least due to its special area of application. The designs are designed to work flawlessly in temperature ranges from -40°C to +55°C. In addition, all requirements for safe handling of combustible dust and for planning protective measures against dust explosions had to be met in order to receive approval for Dust-Ex (tc / tb) with protection class IP65. The VEM group worked hard to bring the motors to the current highest efficiencies IE3 and IE4 and to meet the VIK recommendation.

The entire basic concept of the machine had to be developed in the best case based on the series parts in order to enable the desired "modular principle", since both the active parts, the rib contour and the bearing system come from a series. By using the same material, all the advantages of the W43R series could be transferred to the new components.

The idea of being able to exchange mechanical components depending on the interface also required some modifications - for example, feet, flanges, terminal boxes, fans and fan covers can now be changed according to customer requirements. All proof of strength for expected explosions and the test pressures derived from them 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 routes and a faster delivery time, as overseas transport for components is almost eliminated.

Furthermore, the housing has been designed with baseboards at 4x45° and can also be used for motors where the terminal box is on the N side (Y design). Serialization is also a special step for the VEM Group, as the traceability of components must be guaranteed. In addition, production within tight tolerances and the measurement of the fits relevant for Ex d are special features that the company association is happy to take on with great enthusiasm in order to be able to provide the best for its customers.

Outstanding sales start for VEM

Not least due to the commendable and committed commitment of everyone involved from the design to the test field, entire series production was able to be implemented according to schedule. Two sizes were already approved for sale last year, and five more will follow in 2021. The constant demand for engines from the new series proves the foresight of the VEM Group right. She was able to book the first customer orders on the first day after the series went on sale. Approval from the well-known chemical customer has also already begun. A larger order for 24 Ex (db) motors was placed by VSK (Worms), one of the established maintenance providers in the chemical industry.