Maintenance work

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. 

Ma.intena.nce. There are two types of maintenance work required (11). The first is regular preventative work, such as the periodic inspection and repair of a liner used to promote flow, protect the stmcture, or both. Loss of a liner may be unavoidable for an abrasive or corrosive product, yet... 

Hydrogen is involved in cathodic protection with magnesium anodes on account of the high contribution of self-corrosion. This must be considered in its use in closed containers, e.g., boilers. In enamelled boilers there is no danger from deflagration of the oxy-hydrogen gas under normal service conditions [2] however safety requirements must be observed [28,29], particularly with routine maintenance work. 

Does each permit have a hand-back procedure which incorporates statements that the maintenance work has finished and that the plant has been returned to production staff in a safe condition ... 

Clearance from the elevated overcapacity flare must comply with radiant heat spacing requirements for elevated flares, considering persoimel exposure when maintenance work is being performed on the multijet flare and the... 

Develop and emphasize maintenance work plans on large mining cijuipmeni... 

Maintenance logs which record both the preventive and corrective maintenance work carried out... 

Scheduled maintenance Work performed at a time specifically planned to minimize interruptions in machine availability e.g. changing a gearbox when machine is not required for use (includes predictive and preventive maintenance). 

Many accidents have occurred because maintenance work was not cai -ried out in accordance with the (often unwritten) rules of good engineering practice, as the following incidents and Section 10.4.5 show. 

Inspections showed that two cooling towers contained asbestos. Sticky warning labels were fixed to them. No maintenance work was carried out... 

Another hazard with air coolers is that even though the motor is isolated, air currents have caused the fans to rotate while they were being maintained. Fans should therefore be prevented from moving before any maintenance work is carried out on or near them. 

It is important that the inspection and maintenance activities be docn-mented as reqnired per company practice and any process safety management regnlatory reqnirements. Maintenance records shonld indicate the inspection resnlts and the scope of maintenance work performed, if any. Before the flame arrester is reinstalled in the process, it shonld be visnally inspected to make snre that reassembly conforms to the mannfactnrer s recommendations. Some companies affix a tag to the flame arrester indicating the inspection and maintenance date. 

The failure data for these rates is obtained from maintenance work requests supplemented by incidence reports and Licensee Event Reports from the 1975-1980 time period. The work requests provide a complete history of all repairs performed at Oconee. They are not restricted to safety-related systems, they are written during all modes of unit operation, and they are not produced in response to licensing-based criteria. 

Within the maintenance system, there is generally a means to determine when maintenance work is required and when that work is completed. Different facilities call such records by different names, among them work orders, work requests, trouble tickets, maintenance records, and work authorizations. Despite the variation in names, this valuable information contains ... 

The main functions of a painting specification, whether for new or maintenance work, are as follows ... 

After any maintenance work involving replacement or adjustment of components it is essential that the plant be re-commissioned in a safe way, including dry mns with the gas turned off to ensure that flame failure devices operate correctly and pilot turndown tests to ensure that if the pilot can energize the flame detector then it can also smoothly ignite the main burner. 

Internal personnel will normally undertake boiler plant operation. Maintenance work may be by either internal personnel or outside contractors. Service contracts will be available from equipment suppliers covering all items of the boiler plant. Recently, companies have started offering contract energy-management schemes. These may be designed to suit individual applications and will be tailored to customer requirements. They may take over the operation of an existing plant or, if necessary, include for a new replacement plant. They will usually operate over a 3-10-year contract period. Dependent upon the terms of contract, all fuels, electricity, repairs and replacements may be covered. 

The actual hours necessary to carry out the planned maintenance work task ... 

The total hours to complete the planned maintenance work task (including non-productive hours). Nonproductive hours would include such items as collecting spares, tea breaks, discussions, etc. 

Week task forms should only require amending when either additional plant and equipment is introduced or the frequency of planned maintenance tasks is being adjusted to meet revised operational or maintenance demands. Departments in which work is to be carried out may be issued a copy of their department s week tasks four weeks in advance. This then enables them to program their operation, where necessary, so that the maintenance work can be carried out without disruption to the department s output. Alternatively, on receipt of this prior notice the departmental head can contact the engineer controlling the work to discuss departmental matters that may affect the proposed planned maintenance. This may, in some instances, require the engineer to reschedule the planned maintenance programmed for that department. 

Shutdown work request log When the planning department receives a shutdown work order, it is immediately recorded in the shutdown work request log. The maintenance clerk should verify that the item number assigned agrees with the next sequential number on the maintenance work order log. Work requests forwarded to shutdown planning should indicate equipment number and... 

Historical data Historical data is an improvement over the basic estimating approach in that it does represent the average time required for repetitive jobs. The method for development of data is rather simple in that work orders are assembled for repetitive maintenance work and average times are derived for various categories or natural groupings of work. This could be for jobs of short duration, or the technique could be applied to the same type of jobs, such as pump overhauls. 

Items of plant fabricated from stainless steels should be inspected before first use and after any maintenance work or unplanned shutdown. All materials that rely for their corrosion resistance on the presence of an oxide or similar passive layer are susceptible to localized attack where that layer is absent or damaged. Damage is most commonly caused by scratching, metallic contamination (nearby grinding or touching with ferrous tools), embedding of grit and weld spatter. 

In recent years, numerous mechanical improvements have been implemented to increase the run length and minimize maintenance work during turnarounds. Examples include ... 

It is essential that all major maintenance work and findings are recorded in the plant running log as a guide to the reliability of components, the need for cleaning, and other indicators to future work. 

In addition, a variety of cleaning, inspection, and planned maintenance work is also required, including boil outs, lay ups, protection of idle boilers and nondestructive testing. Some of these many ancillary tasks are discussed in the following sections. 

Closed-and-dry lay-up programs are employed under naturally high-humidity conditions. Again, the boiler is drained, washed down, cleaned if necessary, inspected, and then thoroughly dried. Valves must not leak, and seals must be airtight, which is not always possible, especially if maintenance work or periodic inspections are required. 

Closed-loop systems should lose very little water, perhaps only 5 to 10% of the system volume per year. In practice, however, losses often tend to be much higher than this, perhaps due to unforeseen maintenance work that necessitates a system to be partially drained. A typical loss is more likely to be 50% of the system volume per season. This obviously causes problems with regard to maintaining adequate chemical treatment reserves for effective deposit and corrosion control. In fact, often the first sign that a closed-loop system is losing water is when a periodic test is undertaken and the result indicates a reduced level or complete lack of treatment reserve. 

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