Equipment, for maintenance

Shutdown. Written procedures for normal, as well as for emergency, shutdowns should be prepared, rehearsed, and kept up-to-date. Operating supervisors must be responsible for leaving the process equipment in a safe condition or preparing plant equipment for maintenance work. 

Work space The area or volume of a space in which work on a given process is carried out. The term is also used tor the clearance area provided around equipment for maintenance. 

Drain valves that are used only occasionally to empty equipment for maintenance should be blanked when not in use. Regular surveys should be made to see that the blanks are in position. On one plant, a survey after a turnaround showed that 50 blanks were loose, each hanging on one bolt. 

This chapter describes some accidents that occurred because operating procedures were poor. It does not include accidents that occurred because of defects in procedures for preparing equipment for maintenance or vessels for entry. These are discussed in Chapters 1 and 11. 

The incidents described could occur in many different types of plants and are therefore of widespread interest. Some of them illustrate the hazards involved in activities such as preparing equipment for maintenance and modifying plants. Others illustrate the hazards associated with widely used equipment, such as storage tanks and hoses, and with that universal component of all plants and processes people. Other incidents illustrate the need for techniques, such as hazard and operability studies, and protective devices, such as emergency isolation valves. 

Preparation of Equipment for Maintenance The essential feature of this procedure is a permit-to-work system The operating team members prepare the equipment and write down on the permit the work to be done, the preparation carried out, the remaining hazards, and the precautions necessary. The permit is then accepted by the person or group who will carry out the work and is returned when the work is complete. The permit system will not make maintenance 100 percent safe, but it reduces the chance that hazards will be overlooked, lists ways of controlling them, and informs those doing the job what precautions they should take. The... 

Access to the critical parts of the equipment for maintenance and cleaning should be available. 

Maintenance is a major source of accidents, not so much the maintenance in itself but the preparation of equipment for maintenance. Sometimes the procedures are inadequate sometimes the procedures are satisfactory but not followed. In particular ... 

Opening of equipment for maintenance can result in loss of product. Where possible, the liquid should be blown into the previous or next process vessel or drained back into a bucket for recovery. Any product that is recovered that is not badly contaminated can be returned to a separate storage tank upstream in the process. If a substandard or off-spec glycerine tank is provided in the refining section, it can be equipped with an easily removable cover. 

What follows is a list of useful equipment for maintenance, troubleshooting, and modest instrument modification. 

DQ checks that the design documentation matches the requirements stated in the EDS. Layout drawings, operating and maintenance procedures, parts lists and system descriptions are included in the DQ. Both hardware and software configuration are reviewed together with the supplier s product documentation. DQ offers the opportunity to monitor the progress of project validation as well as any operational and safety issues, such as the use of radioactive instruments or access to analysis equipment for maintenance. 

Start-up after shutdown of a group of equipment for maintenance or cleaning where coordination of several disciplines is required. 

Good initial design of pipework and vessels facilitates preparation of equipment for maintenance and repair. The positioning of flanges so that blanks can be inserted in pipelines and the provision of drain cocks or plugs at low points are typical of items to be considered at the design stage. 

Another form of redundancy is the excess capacity often built into plants with more than one processing line. If two sets of drying towers are used, for example, the capacity of each may be more than 50% of the plant design capacity. The primary justification for multiple trains usually is to enhance turndown capability or to allow continued operation even when one train must be shut down. The same approach may be taken with the cooling section. Given the sizes of chlorine gas headers, valves would be expensive and probably ineffective as shutoff devices. Many plants therefore use U- or J-shaped traps in the piping. These can be filled with water or acid to stop the gas flow and to isolate equipment for maintenance. 

Important users of vacuum include evaporators and dechlorination systems. Lower levels of vacuum are useful in brine sludge filtration and in clearing lines and equipment for maintenance. 

Give consideration to accessing electrical equipment for maintenance troubleshooting. This may involve maintenance bypass switches for certain interlocks. However, the machine should not be allowed to run production in the maintenance bypass mode. The equipment should be so designed to provide access to sensors, switches, and motors, etc., for preventive maintenance procedures performed on a regular basis. 

The short-term memory is extremely susceptible to interference from other activities. It is used as a working store to remember where one has got to in a sequence of events, for example in isolating a piece of equipment for maintenance purposes. It also stores small bits of information between one stage of a process and another, such as the telephone number of a company between looking it up in the directory and dialling the number. 

Non-routine procedure such as equipment clean-outs and preparation of equipment for maintenance Auxiliary equipment operations inciuding as examples LEV and Ventilation Systems, Heat/Cool Skids, Water (Soft, RO, WFI, Tower, etc.) Systems, Instrument and Process Air Systems, Waste Treatment Systems, Cooling (Glycol Refrigeration) Systems, Steam Generation, and others Safety and operational issues Change control procedures ... 

Has potential for external pressure (vacuum) from sudden cooling, condensing, pump-out, during clean-up or preparation of equipment for maintenance, or potentially subrnerged overflow line been addressed ... 

Are provisions made for safe handling of flammable or potentially explosive materials Consider materials of construction, cleanup and preparation of equipment for maintenance. 

Will adequate design provisions exist for cleanup and preparation of equipment for maintenance of equipment/piping/control systems (including lockout of all energy sources and double isolation where required) ... 

---