The MSP series, in the various types: MSP/A1, MSP/A2, MSP/M, etc. relates to Pressurization Control Systems, of Enclosures (Cabinets/Electro-instrumental Panels) explosion protected by means internal overpressure, type of protection “p”

The fundamental criterion of this type of protection is the absolute need to secure the pressurized enclosure, by means of an appropriate “Purging” operation, before activating both the power supplies and any type of signal energized from the outside.

The system is also able to keep a protective gas inside the enclosure, after Purging, at a pressure higher than external atmosphere, in order to avoid the penetration of any explosive atmosphere

In particular, the MSP/A1 and MSP/A2 systems are integrated in the ATEX and IECEx certificates of our MAP series Pressurized Cabinets (“Ex ib pzc” or “Ex ib pxb” type of protection) and can manage not only the Pressurization with protective gas leakage compensation, but also the dilution of any limited release of gas, from internal source.

Each System consists of the following 3 Units:
UNIT 1: “Protective Gas Feeding” series MAG/…
UNIT 2: “Purging Gas Discharge and Pressure Control” series URS40/…
UNIT 3: “Purging/Pressurization Control Logic” series MCP/…

and it can also be supplied separately, to be applied to an Ex p cabinet of another manufacturer

it is also possible to equip an our MAP cabinet with one of the many Systems existing on the market

However, these systems consist of pressurization control “Kits”, which generally make just 2 contacts available (i.e: “Purging Completed” and “Pressurization Failure”) without providing the user with specific instructions regarding the management of the power supplies and signals energized from the outside

In fact, the EN IEC 60079-2 Standard (Art. 7.1÷7.10 and Table 3) obligatorily requires that safety devices be integrated in the control system to allow the activation of the power supplies and signals energized from the outside, only after completion of the “Purging” operation

Therefore the possible Three-phase and/or Single-phase power supply voltages and any Analog/Digital signals and/or Data Transmission Lines (Fieldbus, Serial, Ethernet, Optical Fiber) energized from the outside, other than intrinsically safe, must be suitably interrupted remotely in a safe area, until purging is completed and, when this is not possible, suitable Switches and/or Contactors must be integrated into the control System to intercept the Power supplies and, if necessary, proper cutting Relays for the Signals powered from the outside

In our MSP series Systems, the components relating to the pressurization control logic (Unit 3) are generally housed inside an Ex d Enclosure, to which it may sometimes be necessary to assemble an Ex e enclosure for the terminal blocks

The Ex d Enclosure is sized to also contain all the additional necessary Devices, such as: Switches, Contactors and Cutting Relays, defined and evaluated by us from time to time in the estimate phase

The same enclosure can also be equipped with selector switches and Breakers, for the insertion of plants foreseen to complete the pressurized cabinet, such as:

External lighting plant
Anti-condensation heating plant
Air conditioning plant

The User who decides to adopt the aforementioned “Kits”, equipped with only 2 auxiliary contacts, will run the risk of having to integrate all the other necessary Devices, housing them in Enclosure/s, with suitable type of protection (Ex d, Ex de , etc.) thus having to face major design difficulties in addition to the extra costs for unforeseen devices

Yet with reference to the obligation to avoid any presence of voltage inside a pressurized cabinet, until the purging is completed, we intend to report a Serious misunderstanding that can be found frequently, in installations in Zone 2.