Cabinet installations are an important part of any industrial control system. They are used to house components such as power supply modules, network and server equipment, as well as field termination assemblies. This article will discuss the essential requirements for cabinets in industrial control systems, including system cabinets, network and server cabinets, and field termination assembly cabinets.
General Requirements
Any cable used to interconnect equipment which is physically located in different cabinets, shall be tagged with source and destination on both ends. All cabinets and the equipment therein shall have nameplates permanently attached indicating the service description. Nameplates shall comply with the relevant sections of 34-SAMSS-820 specific to nameplates. Cabinets designed for both front and rear entry shall have a nameplate attached to both the front and back. All cabinets shall be equipped with lockable doors.
System Cabinets
System cabinets shall be NEMA Type 1 as per NEMA 250 and NEMA ICS6. Vendor standard cables shall be designed and installed in such a way as to allow cable disconnection in order to service the equipment. Wiring, spacing, cabling, terminal blocks, and wire ducts in 34-SAMSS-820 shall apply for wiring associated with power supply and power distribution, utility power, lighting, and convenience outlets, intermediate terminal strips for I/O wiring, and grounding.
Network and Server Cabinets
Network / Server equipment located in Central Control buildings (CCB) may be installed in industrial strength network / server cabinets conforming to the EIA / ECA 310 specification. NEMA type 1 cabinets shall be used for network / server cabinets located in Process Interface Buildings or other locations which are not environmentally controlled. Network / Server cabinets located in CCB which meet the air conditioning requirements specified in Section 9 of SAES-J-801, Control Buildings, may have perforated doors to facilitate air circulation and cooling.
The requirements in Section 17, “Electrical wiring and power distribution” shall apply for all network and server cabinets. Network cabinets and server cabinets which contain multiple servers which utilize fiber optic Network Interface Cards (NIC) shall be equipped with Fiber Optic Patch Panels to terminate fiber optic cables entering or exiting the cabinet. Fiber Optic Patch panels shall be sized to accommodate a minimum of 10% spare termination ports. Fiber optic cables within a cabinet shall be routed in plastic wire ducts or protective conduit.
Field Termination Assembly Cabinets
The requirements of 34-SAMSS-820, “Instrument Control Cabinets – Indoors” shall apply to Field Termination Assembly (FTA) cabinets with the following exceptions or modifications: Equipment installed in FTA cabinets which are installed indoors in air-conditioned buildings shall be designed for 100C – 350C.
Heat dissipation calculations are not required for FTA cabinets. For FTA cabinets which are designed for front and rear access which contain power supply modules which are shared by equipment in both sides of the cabinet, the separation panel may be shortened to accommodate power supply modules located at the top of the cabinet. FTA cabinets may be designed for front and rear access.
The requirement for 20% spare Terminal Blocks (TBs) is for TBs required for landing of field cables only. It does not apply to power distribution wiring or TBs which are an integral part of the vendor’s Field Termination Assemblies. Terminal blocks used to land field wiring for signals which are connected to Input / Output modules which provide the loop power and which contain current limiting circuitry do not require fused or quick disconnect type terminal blocks. Cabinet lighting is not required for FTA cabinets which are located in sufficiently lighted areas. Certificates are not required for FTA cabinets. This information is verified during product evaluations.
Marshalling Cabinets
Marshalling cabinets shall comply with the requirements of 34-SAMSS-820, “Instrument Control Cabinets – Indoors.”
Cabinet Protection
All System cabinets and any Field Termination cabinet which contains power supply modules shall contain a minimum of one continuously running air circulation fan. All cabinets shall be designed to ensure the heat rise within the cabinet does not exceed 10°C. Where circulation fans are required to meet the maximum heat rise requirement, redundant air circulation fans shall be provided.
Heat load calculations may take credit for heat dissipation from air circulation for one of the redundant fans. Cabinet cooling fans shall be sized to handle 20% more air flow by volume than the amount taken credit for in the heat dissipation calculation.
Cabinets which contain redundant cooling fans, shall be configured to have one fan run continuously and the other fan to be energized based on the temperature inside the cabinet. Activation of the redundant fan shall be at 30°C. Cabinets which require redundant air circulation fans for cabinet cooling shall be provided with a fan failure sensor for the continuously running fan.
Fan failure alarms shall be connected to the DCS to provide alarming of any failure at the operator console. All system, network and server cabinets, any cabinet which contains redundant air circulation fans and any field termination cabinets which contain power supply modules shall contain a continuous analog temperature sensing device (RTD).
This device shall be connected to the DCS to provide cabinet temperature indication and to provide high temperature alarming at 35°C to the operators. Each cabinet with cooling fans shall be fitted with replaceable or washable filter screens inserted behind slotted louver inlets for cabinet air supply air. Filter screens shall be installed for easy maintenance access and shall be large enough to provide sufficient air intake flow. Cabinets which house power supply modules shall be capable of housing a High Sensitivity Smoke Detector (HSSD).
Documentation
Documentation shall be provided for all cabinets as defined in form NMR-7923, Non Material Requirements for Control Panels.
Conclusion
Cabinets are an essential part of any industrial control system. This article has discussed the essential requirements for system, network, and server cabinets, as well as field termination assembly cabinets. These requirements include nameplates, lockable doors, NEMA Type 1 compliance, wiring and power distribution requirements, fiber optic patch panels, and more. Additionally, cabinet protection requirements have been discussed, including air circulation fans, temperature sensors, and High Sensitivity Smoke Detectors. Finally, documentation requirements have been discussed. By following these requirements, cabinets in industrial control systems can be installed safely and correctly, ensuring optimal performance.
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