Maintenance access

Layout considerations include avoiding crane lifts over operating equipment, especially equipment that contains hazardous materials, and, in particular, hazardous materials held under pressure or high temperature. Allow space for maintenance access without damage to other equipment. Apply risk management concepts to the layout and siting. 

The potential for interference with the normal operation and maintenance of a process vessel is high. A major design effort is required to overcome this disadvantage. All aspects of the process vessel operation must be considered. Lines of sight for process vessel and crane operators, access for crane-held ladles and buckets, process vessel movements, and maintenance access must be accommodated by the enclosure design. This is more easily achieved in a new installation. 

Easy maintenance access must be provided. Removable roof panels for access to furnace subassemblies are desirable. Water-cooled equipment, electrode, and roof movement mechanisms, etc. all require overhead access for proper maintenance. 

In some installations (e.g. clean rooms), the electrical distribution system can be located in the sealed ceilings, allowing maintenance access without affecting the clean facilities (Figure 7.12). 

Adjacent space Within cooled space Maintenance access ... 

Fresh hydrofluoric acid used for catalyst make-up is anhydrous and of 99.5%+ purity. Since the acid in the unit is continually being regenerated, the only hydrofluoric acid consumed in the process is that which is absorbed in the bauxite towers, lost to the acid tar, lost in handling, or lost through venting equipment and lines for maintenance access. Typically, hydrofluoric acid consumption, including losses to all sources, will average about 0.5 to 0.8 pound per barrel of alkylate. 

Two flare booms may have the advantage of having a short enough length to be pivoted and retracted when not in use, as on drilling rig flares. Being retractable has a maintenance access advantage also. 

A sufficient number of access doors, ladders and walkways shall be provided for safe and easy accessibility to internals and mechanical equipment of the tower for inspection and maintenance. Access doors shall be tight, resistant and easy to operate. Access ladders from the ground should be located in such a position to permit future cell addition. 

Reverse osmosis skids are typically contained within a frame of galvanized or urethane-coated steel. Skids should be designed for easy access for monitoring and maintenance. Access to controls, instruments, valves, the pump and motor, and membranes is essential. Access to the permeate from each pressure vessel is often overlooked. Without such access, profiling and probing used to troubleshoot poor performance is not possible (see Chapter 14.7). 

The selection of the components for a SCF food processing plant requires careful evaluation of the operating requirements from the perspectives of cleanliness, sanitation, maintenance, accessibility and safety for the pressures and temperatures to be encountered. Specific areas must carefully considered to ensure the satisfactory... 

The second loss is by radiation from the belt. The belt, which is of heavy construction for rigidity and flatness is a very significant heat sink. Some of this heat transfers to the panel where it is needed and some where it is not needed. The remainder is lost to the atmosphere by radiation during its idle return to the input end. This loss can be reduced by insulation but the problem of removing and restoring this insulation for inspection and maintenance access makes it impractical. A measurement on a double belt revealed a 20°F (11°C) loss in belt temperature during the return run. 

Figure 7-6 shows a plan of the feed gas compressor area for a 200,000 tons per year ethylene unit. Main pipe runs are also shown. It is an In-Line-Layout with equipment in process flow sequence. The large diameter gas lines directly interconnect process equipment. On the complete plot plan, equipment (including compressors) is arranged on both sides of a central yard in process flow sequence. Pumps are located at their point of suction and are lined up under the yard. A parallel road is arranged to every line of equipment for convenient construction and maintenance access. 

With turbine surface condensers, it often pays to choose a pump with a low NPSH, especially when die condenser is directly below the turbine. The compressor house floor can be lowered. With the lower elevated condenser, operation and maintenance access is improved. Vertical pumps are usually specified with a minimum height from grade to equipment because their suction inlet nozzle is below grade. 

Figure 2 Serviceability Analysis of a Design Can Be Performed Prior to a Prototype Build. Here the Jack human figure is used to analyze the maintenance access to an electrical box inside of the aircraft nose cone. Eye views and collision detection can help the designer during the evaluation process. (Courtesy EMBRAER)...

Plot space Plot space is limited and constrained by maintenance access, fire, safety and emergency handling requirements Sufficient plot space is generally available... 

The process gases enter a forced-circulation-type waste heat boiler at 800-1000 °C. Several changes have been made to the mechanical rapping equipment and cooling pipe bundles of the boiler to improve the performance and maintenance access. The gases exit the waste heat boilers at a temperature of 300-350 °C and pass through the hot cyclone separators and electrostatic precipitators into the mercury removal towers. Two electrostatic precipitators are installed simultaneously in both lines to ensure continuous processing. 

The approach models instant maintenance access only. There is no delay considered between a system failure and the beginning of a maintenance action insofar the maintenance unit is not busy with another system. - In Rakowsky (2007) it is shown how to model delayed maintenance access. 

The product gases leave the elements together with the electrolytes downward through vertical discharge pipes, the collectors, and flexible PTFE hoses. All inlet and outlet connections are located at the bottom of the electrolyzer, releasing the space above the cell for maintenance access. The mesh-type anode serves as a support for the membrane, while a defined gap can be maintained between the louver type cathode and the membrane by spacing devices. 

Even with the clearest model presentation, there is a need for the ongoing model development to be supervised by dedicated design co-ordinators. The modelling software usually includes clash detection and notification, but it is still necessary to ensure that in conflicts the most important needs prevail and to maintain the integrity of operational and maintenance access and ergonomics. There is also frequently a need for ongoing independent review of the drawings or output communication, from the point of view of their users. 

The emphasis of the CANDU 300 design effort has been to reduce construction time and cost. This is aided by a station layout which provides 360 degree construction and maintenance access to the five principle buildings (Figure B), thereby permitting optimized construction sequence and methods. Modularized shop fabricated systems are also extensively used. 

The ergonomic review of a workstation must consider backup provisions and maintenance access and activities. This document is to be used as a trigger point in determining if an ergonomic assessment of a particular workstation is required. 

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