Siemens: Maximum Safety In Explosive Atmospheres – Drive Technology For Oil, Gas And Petrochemical Applications

Highly explosive gases are frequently prevalent in the oil, gas and petrochemical environments. In parts of plants where there is a risk of explosion, it is especially drive systems that must optimally comply with all of the applicable regulations – and must have maximum reliability to optimally protect man, machine and the environment. Here, with its seamless portfolio of explosion-protected drive systems, Siemens covers every conceivable application: In the chemical and petrochemical industry – as well as in oil and gas – from 0.1 kW up to 100 MW, with speeds extending up to 15,000 rpm – as standard system or customized solution for all of the applicable types of protection.

The range of Simotics and Loher motors encompasses type of protection Ex n (non sparking) for gas explosion protection, Zone 2, where sparks that can potentially ignite an explosion must not occur. The range also includes pressurized enclosure Ex p for gas explosion protection, Zone 1. In this case, an inert gas inside the motor prevents the ingress of explosive gases. Also part of the portfolio, Ex e (increased safety) for gas explosion protection, Zone 1, which prevents inadmissibly high temperatures at any point on the motor – and Ex d motors with flameproof enclosure for Zone 1. With this degree of protection, the motor is designed so that an explosion in the motor cannot be propagated to outside the motor, and at the same time the enclosure can withstand the pressure of the explosion. Especially for flameproof encapsulated motors, Siemens has a portfolio that is second to none in the global motor market when it comes to scope and features. All flameproof explosion-protected motors in all types of construction are individually tested in the factory to ensure that they are absolutely pressure tight. Our motors with flameproof enclosure are rib cooled up to 2800 kW and for higher power ratings, also tube cooled.

Double protection for extraordinary requirements

Our drives can also be implemented with double protection to address special requirements: On one hand, this is a combination of gas and dust explosion protection for areas in which fine dust and explosive gases can simultaneously occur. The other possibility is double protection in Ex d and Ex e. This double protection is, for example, practical for liquid gas tankers, where it is imperative that the electrical equipment can be absolutely excluded as potential ignition source due to the hazardous freight that they are carrying.  Here, Siemens designs and builds its explosion-protected motors mechanically with “flameproof encapsulation” type of protection. At the same time, it ensures that the temperatures of the active parts of the motor comply with type of protection “Increased safety”.

Certified for the global market// Certificates for the global market

It goes without saying that Siemens explosion-protected motors are always certified according to ATEX; ATEX is the Directive of the European Union that harmonizes the regulations of individual member states when it comes to explosion protection. Further, they are certified by the Physikalisch-Technischen Bundesanstalt (PTB). A version complying with VIK directives (Association of the Industrial Energy and Power Industry) is optionally available. Naturally, to address applications around the world, these motors have other certificates for specific countries, such as NEPSI (China), CCOE (India) and Rostekhnadzor (Russia) – this also applies to low temperatures. This feature makes them predestined for applications in cold regions around the globe. Last not least, these motors are also certified according to the new international IECEx scheme. Over the medium-term, this is intended to be the global platform for mutually recognizing and accepting tests and certificates for explosion-protected equipment. The IECEx scheme has already been specified in Australia and New Zealand and many important industrial nations. Almost the whole of Europe, China, Russia as well as the US and Canada have signed the appropriate certification agreement.

Equipped to cope with extremes

Not only risk of explosion, the process industry is also characterized by other extreme conditions: Frequently, heat, cold, dirt and aggressive atmospheres are a daily occurrence. Our drive systems are also optimally equipped to cope with these conditions. Examples include operating temperatures from -55 – 70°C, and degrees of protection up to IP68. Special series such as the LOHER Chemstar set themselves apart as they are designed to address the requirements of specific sectors: With a high quality paint finish that is resistant to chemicals, galvanized fan cover – and when required, with corrosion-resistant stainless steel screws and bolts. Special shaft seals, which provide protection against water and dust, allow these motors to be installed outdoors.

Water-jacket cooled explosion-protected motors are also included in the portfolio, in types of protection Ex n, Ex e and Ex d. These are the optimum solution where space is restricted, for environments that are noise sensitive or where it makes sense to be completely independent of the ambient air as a result of an especially aggressive atmosphere.

High efficiency for low operating costs

For several years now, the high IE2 efficiency class has been specified for motors in the European Economic Area. Such an IE2 motor has an efficiency that is up to seven percent higher than a conventional motor. According to legal stipulations, explosion-protected motors are excluded from this ruling. However, in spite of this, Siemens offers

explosion-protected motors across the board in IE2 for the complete area of validity of the standard – from 0.75 kW up to 375 kW. This is now applicable for all types of protection – Ex n, Ex e, Ex p and Ex d.  This is because also Ex e motors (increased safety) are now available in IE2. As a result of the specific requirements placed on motors with type of protection Ex e – for example regarding the air gap and starting current – higher efficiencies were difficult to achieve in this area. Siemens has now been successful in achieving this with its new series.

Further, when requested, explosion-protected motors can also be built with the even higher IE3 efficiency class; when compared to conventional motors, they have an efficiency that is up to 10% higher Loher and Siemens are presently developing a seamless series of explosion-protected motors with IE3 efficiency.

Converters specifically developed for explosion-protected motors

Converters are available, specifically designed for use with explosion-protected motors; these converters address the requirements of explosion protection. The Sinamics G180 converter has been specifically developed for the chemical and petrochemical industries. It is available with power ratings extending from 2.2 up to 6600 kW – and is ATEX certified for operation with explosion-protected motors in Zones 2 and 1. For these devices, an ATEX-certified shutdown concept allows the plant or system to be shut down without requiring the use of a main contactor. This also applies when motors are operated in hazardous Zone 1 without the dimensions having to be changed. This allows significant cost saving on the plant side.

Beyond explosion protection, all of the sector-specific features of the process industry are integrated in the Sinamics G180 as standard. For the chemical industry, this extends from the NAMUR terminal strip through PELV up to the du/dt filter. Operation employing the PROFIBUS profile PROFIdrive 4.1 – “Process technology” operating mode – is also possible.

Sinamics G180 can be integrated into the higher-level SIMATIC PCS 7 process control system using driver blocks and faceplates specifically developed for the purpose. This means that the drive can be controlled via PROFIBUS from the central PCS7 control room, where all of the operating data can be visualized.

Couplings and gearboxes according to ATEX

On the mechanical side of the drive train, Flender gearboxes and couplings are also certified according to ATEX. This means that Flender rupex / n-eupex and Flender aprex couplings can be optionally certified as devices for use in hazardous zones according to this directive.

ATEX geared motors from the Motox series, equipped with helical, bevel, helical worm, parallel shaft as well as worm gearboxes.

Table with an overview of explosion-protected motors

Fig_1 Title

Fig_2: Explosion-protected motors are available in all types of protection and in high efficiency classes

Fig_3: Explosion-protected motors are also available with water-jacket cooling up to high power ratings for applications where space is restricted or where the ambient air is very aggressive

Fig_4: Sinamics G180 converters for the process industry are specifically designed for operating explosion-protected motors, also in Zone 1