1. PURPOSE
This article is about the considerations to be given in the design process to accommodate all the types of equipment in control buildings.
2. SCOPE
2.1 This standard applies to the requirements for the provision of instrumentation, computer systems, and communications equipment within control buildings in plants.
2.2 It may be used as a guide when considering the requirements of third party projects.
3. RELATED DOCUMENTS
3.1 Air Products Engineering Documents
3ES80101 Risk Management of Hazards in Equipment Enclosures That Can Be Entered by Personnel
Design Criteria for Plant Layout
Hazardous Gas Analyser Installations
3.2 Instrument Society of America (ISA)
ISA RP60.1 Control Center Facilities
ISA RP60.3 Human Engineering for Control Centers
ISA 71.04 Environmental Conditions for Process Measurement and Control Systems: Airborne Contaminants
4. GENERAL
Control buildings usually have the following separate equipment rooms:
- Control room
- Analyser room
- DCS room
- Electrical equipment room
The rooms might be in one building or in separate buildings depending on the geography of the site or the logistics regarding personnel.
4.2 When determining the location and internal building layout, the following shall be considered:
- Minimization of cable runs by placing the Marshalling (when applicable) and Distributed Control System (DCS) termination cabinets in the centre of the plant
- Analyser responses are improved by locating the analysers as close as possible to the sample point.
- The main pipe rack provides a good route for the multicores running between the DCS and the field junction boxes.
- The main equipment rooms shall not be located adjacent to major machinery or other sources of noise and vibration.
- In plants containing flammables, the control room and all equipment rooms shall be located in a nonhazardous area.
4.3 Access doors shall be provided in each equipment room, preferably directly to the outside, with sufficient height clearance to allow the cabinets to be maneuvered into place. An allowance shall be provided in case rollers or wheels are used to move the equipment.
5. CONTROL ROOM CONSIDERATIONS
- The control room lighting arrangement shall consider the position of the DCS visual display units and shall not create glare or reduce the legibility of the displays. If necessary, spotlights shall be provided to direct lighting where required for working purposes when the main lights are dimmed to assist operator comfort.
- The temperature and air quality in the control room shall be consistent with normal office standards (see Table 1).
- The layout of the main controls and the equipment shall ensure that the operator can carry out all normal and all emergency functions without leaving the normal position at the console.
- Note: This includes the control of the communication equipment, including telephones, radios, and intercoms, the opening and closing of the main gate, and the control of the camera/monitor system. The operator shall have sight of the main gate and the tanker fill area either directly or via the camera/monitor system. Pan, tilt, and zoom controls shall be provided to cover all fill points.
- A horizontal work space shall be available adjacent to the console for viewing documents and A1 (594 x 840) sized drawings. Storage facilities shall be available in the control room for key documents such as P&IDs, schematics, manuals, and others.
6. ANALYSER ROOMS
- For analysers that are sampling hazardous, flammable gases, the installation shall comply with 4PS05002E that defines requirements necessary to protect personnel from explosions.
- For analysers that take a nonflammable sample but consume a flammable gas as a fuel source [e.g., flame-ionisation, detector-type (FID) hydrocarbon analyser], Section 5.6 of 4PS05002E shall be applied. Most air separation plants have at least one analyser of this type that uses hydrogen as a fuel.
- The ventilation of analyser rooms shall be adequate to dilute any leak of asphyxiate gases from sample lines to a safe level. The minimum number of air changes per hour shall be as listed in Table 1.
- To avoid gas buildup under the floor, ducting or trenches shall not be used in the analyser room. All cable and tube entry to and from the analyser panel shall be from overhead.
- Analyser sample vents shall exit the building at a safe location and away from ventilation or air conditioning intakes.
- Two exits from analyser rooms shall be provided.
- When the analyser room is remote from the control room, a telephone or intercom link shall be provided to assist in analyser calibration and maintenance.
7. DCS ROOM
- The DCS equipment produces significant amounts of heat and, therefore, the DCS room usually has to be air conditioned to maintain the temperature below 25°C. The room height shall be sufficient to accommodate the air conditioning ducts as well as the cable tray or ducts located above the 2.4 meter height of the DCS cabinets.
- The DCS room can also be used for accommodating shutdown systems, interface cabinets, marshalling racks, and other miscellaneous equipment cabinets. The space, power, and air conditioning requirements of this equipment shall be considered at an early project stage.
8. ELECTRICAL EQUIPMENT ROOM
- When included in the project scope, the electrical equipment room is used to house systems such as the Uninterruptible Power Supply (UPS) including backup batteries, the Constant Voltage Transformer (CVT), and the distribution board for instrument power supplies. Alternatively, the UPS and CVT might be located in the electrical substation and the distribution boards in the DCS room.
- Ideally, the electrical equipment room should be completely separated from the DCS room and other instrument rooms with separate access doors with at least one exiting directly to the outside.
Table 1
Notes:
1. Higher rates may be required to avoid asphyxiation or explosion hazard as defined in 3ES80101.
2. The temperature range for rooms containing ultrahigh-purity analysers shall be 18° to 22°