Siemens ET 200M, Руководство пользователя, Страница: 29 / 284

Installation
Marshalled Termination Assemblies for ET200M Remote I/O Modules
A5E00482820-12 29
Environmental Considerations
Operate the ET200M MTAs within their environmental specifications to help ensure
reliable, trouble-free operation with minimum down time. Refer to the Technical
Specifications sections for each MTA’s operating temperatures limits, operating
humidity, and maximum moisture content.
Temperature
Keep the air surrounding an operating system below 60°C (140°F). Check air
temperature periodically to ensure that this specification is not being exceeded.
! Caution
Exceeding the specified operating temperature limits can adversely affect
performance and may cause damage to the MTA.
Forced air ventilation is possible when MTAs are mounted in a partially or completely
enclosed panel or cabinet (for example, NEMA 1). When clean air is present, exhaust
fans are often mounted across the top of a panel and louvers formed in the panel
bottom. Air is then drawn upward between the station cases. When air contains
particulate matter, fans and filters are generally located at the panel bottom and louvers
at the top. Filtered air is now forced upward between the station cases. Filters must be
serviced periodically.
Only high quality, quiet running fans should be used. Also, the fans should not generate
electrical noise which could interfere with electronic instruments.
A sealed cabinet (e.g. NEMA 12 or 4X) containing equipment that does not generate
significant heat should contain a recirculating fan for forcing air flow around equipment
and throughout the cabinet preventing hot spots from developing. Forced air
conditioning may be required in very high density panels or consoles. Periodically
change or clean air filters.
Contaminants
The MTA is open to permit circulation of clean cooling air. Liquids and corrosive gases
must not be allowed to enter the case. Whether the MTA is in a control room or field
mounted it must be protected from rain, air conditioning condensate, and plant and
process related fluids and gases. Extended exposure to contaminants can result in
malfunctions.
Industrial environments often contain airborne particulate contaminants. Particulate
matter, usually dust and dirt, is abrasive and can cause intermittent connections. A
layer of dust on circuit boards can interfere with component heat dissipation and can
absorb other airborne contaminants. Extended exposure to these contaminants may
result in malfunctions.
Although ET200M MTAs have a protective coating, the following steps can reduce
contaminant related equipment malfunctions:
1. Identify contaminants and implement methods to reduce their presence.
2. Install protective housing for field mounted units.
3. When cleaning equipment and surrounding area, especially the floor, either
vacuum away all dust and dirt or use a dampened rag or mop. Sweeping or dry
dusting recirculates dust and dirt.
4. Clean or replace all air conditioning filters, room air filters, and equipment filters
regularly.
5. Inform all personnel with access to the equipment of the need for cleanliness.