Stainless steel PC - ATEX

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Stainless steel PC of the EXPERT ATEX series

Many production companies want to extend their IT standards to potentially explosive environments in order to record data, visualize or control processes. The stainless steel PC of the EXPERT ATEX series is approved as a category 3 device for zones 22 and 2.

Wherever explosions can occur due to dust or gases, the legislator prescribes special precautions by means of the ATEX directive. If electronic equipment is used, it must not give rise to dangerous sparks. But what exactly must be met in order to be able to use a stainless steel PC in the Ex area? FORSIS has taken on this question and developed an ATEX-compliant variant of the stainless steel PC from the EXPERT series.

The areas of application for the stainless steel PC ATEX are diverse. The project at FORSIS was brought to life through numerous inquiries from the food industry and other production companies.

For example, bakeries deal with flour dust, which can catch fire. In the textile processing industry there is a risk of fine fibers. In other industries there are atomized paints, powders, lacquers or solvents.

The fact that there is a need for a stainless steel PC ATEX is proven not least by the funding of the FORSIS development project by the Federal Ministry for Economic Affairs and Energy as part of the ZIM (Central Innovation Program for SMEs).

General information on explosion protection

The explosion protection according to the ATEX directive 2014/34 / EU essentially distinguishes three levels:

  • Level 1 - Avoid Hazards
    Every operator of an EX area is obliged to operate the system in such a way that, if possible, no explosive atmosphere is created. Devices with a high explosion potential should, for example, be placed in a less endangered zone.
  • Stage 2 - Prevent Explosion
    If devices cannot be placed outside the endangered area, for example sensors in a silo or tank, they must be technically built in such a way that they cannot ignite an existing explosive atmosphere.
  • Level 3 - Limit Impact
    If an explosion cannot be prevented, a system must be set up in such a way that any explosion is directed in a specific direction and the effect is deliberately limited spatially, for example by a predetermined breaking point in a steam boiler.
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ATEX regulations

Atex Computer Zonen2 Min

The relevant regulations for explosion protection in Europe are based on the so-called ATEX directives.

A distinction is made between three zones in ascending order of the explosion risk:

  • Zones 2, 1 and 0 for gas atmospheres
  • In dusty atmospheres, zones 22, 21 and 20

Our stainless steel PC ATEX has been checked and confirmed for zones 2 and 22 by an independent testing institute.

 

Ex zones and device categories according to ATEX

Atex Computer Zonen Min

Which zones are now suitable for industrial PCs?

0 or 20 certainly not, because that would correspond to the use inside a flour silo or fuel tank.
It is also sensible not to place a device directly under a chute of a silo outlet (zone 21) or in the immediate vicinity of a fuel tap (zone 1). This already forbids the primary explosion protection with the approach to avoid potential dangers, unless there is an absolute necessity to do so.
This leaves zones 22 and 2, for which there are indeed many useful applications. ATEX defines device categories for classifying electrical equipment that are designed for a certain level of safety.
For the stainless steel PC ATEX this is category 3, which must prevent effective ignition sources in normal operation.

Tough test procedures: IP65 is not the same as IP65

Atex Computer Interface Min

A special feature of the ATEX certification are the increased requirements for the housing of the stainless steel PC, which differ significantly from the general requirements according to IP65.
On the one hand, the test devices are artificially aged by being stored for 28 days at 80 ° C and 90% humidity and then for 24 hours at -25 ° C.
Several mechanical tests are then carried out. For example, a 1kg ball is dropped from a height of up to 70 cm onto all sensitive housing parts such as the touch screen, display or cable entry. Furthermore, the devices must exist in a dust chamber with overpressure without dust deposits being subsequently found in the device.

When testing the vapor security, a negative pressure is generated in the device. The subsequent pressure equalization may only take place to a limited extent within a certain time interval.

EX interfaces

EX LogoSP

The FORSIS stainless steel PC ATEX offers far more than just standard interfaces for connecting external peripherals.
The LAN interface can easily be laid in the safe area using a cable gland.
The situation is different with keyboards and barcode readers, the interfaces of which have to achieve a suitable level of protection. This is why the stainless steel PC ATEX has two USB and one RS232 interface, each of which is intrinsically safe and certified according to type of protection EX ic. The two USB interfaces have correspondingly different current limits, so that a large number of certified peripheral devices can be connected.
The internal intrinsically safe interfaces are certified as EX ic. Thanks to their design, it is also possible, if required, to have them certified as EX ib as part of an individual test. This means that intrinsically safe end devices that are located in Zone 1 or 21 can also be connected to the ATEX stainless steel PC.

Andreas Brenke Vertrieb

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ZIM funding

Impulse Zim

The Central Innovation Program for SMEs (ZIM) is a nationwide, technology and industry-open funding program. The ZIM is intended to sustainably support the innovative strength and competitiveness of companies and thus make a contribution to their growth, combined with the creation and safeguarding of jobs.

FORSIS, as a medium-sized company that works with ZIM, has received a grant for the sophisticated development of the ATEX stainless steel PC.

Processor

6. Gen. Skylake Intel Core i3 6100U

RAM

Up to 8 GB DDR3L-RAM 1600 MHz

SSD

Up to 256GB

I/O

2x Ethernet 10/100/1000 MBit

LCD

15“ LCD, 1024x768

Touch

Touchpanel analog resistiv (ELO)

Interfaces

VGA, HDMI, 2x USB 3.0, 2x USB 2.0

The types of protection: Ex tD and Ex nR

In order to prevent the simultaneous presence of an ignition source and an explosive atmosphere, constructive measures are required that represent a corresponding type of protection.
Protection type EX tD (protection by housing) applies to flammable dust atmospheres. To ensure this, the surface temperature of the stainless steel PC ATEX must always remain below a certain maximum value. In addition, a dust-proof housing according to IP65 ensures that no dust enters and leads to an explosive atmosphere inside.
For gas atmospheres, the EXPERT 1500 ATEX with ignition protection type EX nR offers what is known as vapor security. For this purpose, the device must be designed so tight that a gas plume can only penetrate the device minimally and very slowly, even with a slight overpressure. The amount of gas that has penetrated must in turn be so small that it does not allow ignition when mixed with the air in the device.

Classification dust

II 3D Ex tc [Ex ic] IIIC T65°C Dc

Device group II

Device for use in potentially explosive dust and gas atmospheres

Category 3D

Zone 22 (dust), with rare and short-term danger, normal safety

Ex tD

Degree of protection: protection by housing

[Ex ic]

Integrated circuits for intrinsically safe interfaces that can be routed to the outside

Dust group IIIC

conductive dust

Maximum surface temperature

T65°C (corresponds to 65°C)

Dc

Equipment Protection Level Dc (Dust – Normal Protection (3D))

Classification gas

II 3G Ex nR [Ex ic] IIB T4 Gc

Device group II

Device for use in potentially explosive dust and gas atmospheres

Category 3G

Zone 3 (gas), with rare and short-term danger, normal safety

Ex nR

Protection class: vapor security

[Ex ic]

Integrated circuits for intrinsically safe interfaces that can be routed to the outside

Gas group IIB

No operation with: hydrogen, acetylene, carbon disulfide!

Temperature group T4

Gases with ignition temperatures above 135 ° C

Gc

Equipment Protection Level Gc (Gas - Normal Protection (3G))

Our stainless steel PC ATEX has been certified for zones 22 and 2 by an independent testing institute.

Nevertheless, the responsibility for the professional installation and the safe operation on site lies with the user. This must pull the power line and the power cable through the cable entry, screw this to the connection plate and the latter to the device. You can no longer determine whether the device is actually still so tight that no more gas can penetrate.

FORSIS has remedied this by installing a test valve for a measurement by an external test device on the ATEX stainless steel PC. This tester can either be purchased or borrowed. It generates a negative pressure of approx. 30 mbar inside the stainless steel PC and then starts a measuring process. During the duration of the test (14 seconds) the value may drop to a maximum of 27 mbar.