Ladder access control

The important features of ladder access control are the size and strength of the cover and its ability to lock or otherwise be secured from unauthorized access. 

For process equipment, designers need to specify necessary safety features and the tests for meeting requirements. For process equipment, there should be fail-safe features. Fire protection, overpressure, excess heat, runaway reactions, dust control, exhaust ventilation, dangers of flammable liquids, leaks, sensing devices to report status are all examples of important safety features. Designers and purchasers need to consider access for setup, maintenance and cleaning. There may be a need for access by stairs, fixed ladders or platforms as part of large equipment. 

The converter tower should be made of stainless steel 316. The catalyst mass on each of the 4 beds is "sandwiched" between two layers of quartz the top layer ensures proper gas distribution to the underlying catalyst bed and the underlayer prevents catalyst pellets falling through the stainless steel supporting grid. There is a manhole above each bed, used for catalyst inspection and catalyst replacement. Ideally these manholes should be accessible by a permanent scaffolding construction with a ladder and a small platform to each bed position. Thermocouples are located after entry and at the exit of each of the converter beds. The operation of the converter is controlled by the entry temperature of each bed. It should be verified that each thermocouple is correctly positioned and in good condition. 

Figure 8.7 From CIS49 REVI General Access Scaffolds and Ladders. Construction Information Sheet No. 49 (revision) (HSE Books 2003). Crown copyright material is reproduced with the permission of the Controller of HMSO and Queen s Printer for Scotland.

EXHIBIT 2-6 Operator Access to Controls Platform Item or Grade Fixed Ladder... 

For tall vertical drums, platforms are usually circular and supported by brackets attached to the shell of the drum. Platforms at horizontal drums are usually rectangular and are supported by brackets attached to the concrete piers supporting the drum or trunnions attached to the shell of the drum, or by struaural steel supported from grade. Drums located in structures, if size permits, use the struaure floor for access to controls. Top head platforms on horizontal and vertical installations are supported by trunnions attached to the vessel head. Generally, access to freestanding drum platforms is by ladder. Typical drum platform arrangements are shown in Exhibit 5-19. 

Platform elevations for drums are set by. the items that require operation and maintenance. On tall vertical and high elevated horizontal drums, the platform elevations are determined by a maximum ladder run of 30 ft (9,150 mm). Exhibit 5-20 illustrates horizontal drum platform and ladder elevation requirements. Platform floor space requirements are dictated by operator access to controls, instruments, and maintenance accesses. Exhibits 5-21 and 5-22 show platform floor space requitemene for horizontal and vertical... 

This chapter highlights the general requirements for tower plant layout design. It describes the internal workings of towers and provides the information required to orient nozzles locate instruments, piping, and controls and provide platforms and ladders for operator and maintenance access. 

Mold changeover is often labor intensive. For very large machines, process adjustments may be far above or below floor level. Permanently mounted caged ladders are used for overhead access. Special breathing apparatus is needed for set up of controls that are more than a meter below grade. If the carrousel is far above the operators reach, automatic load and unload features are used. 

Planning and control strategies should be aimed at making decisions about such issues by management, rather than leaving them to site workers who will not normally be aware of all the constraints. For example, a subcontractor may attempt to put up ladders or a temporary scaffold to gain access to the outside of a structure, unaware that the spot chosen is on a major access route that happens to be quiet at the time. Third parties should not have to make decisions about ensuring their own safety they should be excluded from work areas where they may be at risk. 

It should be noted that vertical vessels have some drawbacks that are not process-related and that must be considered in making a selection. For example, the relief valve and some of the controls may be difficult to service without special access platforms and ladders. The vessel may have to be removed from a skid for trucking due to height restrictions. 

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