Maintenance frequency

M7 Improved Housekeeping, Training, Inventory Control (e.g., alter maintenance frequency institute leak detection program improved inventory control institute training program on waste minimization)... 

Many users are concerned about the maintenance frequency of their SRVs installed base. Many major companies have their own internal procedures or are following codes and recommendations. However, there are no strict legal requirements that touch on maintenance frequency of SRVs. Once in some boiler installations in the past, it was a rule, or better a habit, for the firemen to pop the valves daily or weekly by means of the lifting lever, an unenviable job as it was extremely dangerous for the personnel and also not very good for the valve itself. It also required a minimum operating pressure of 75% of set pressure, usually of very hot steam, something you do not want to be very close to. This procedure also led to a lot of accidents and so is not used very frequently anymore. Other companies only tested and maintained their valves after an accident or major pressure upset, and all the rest was/is between both these extremes. 

The maintenance frequency is, in my opinion, dependent on too many variables and combinations thereof (process conditions, environment, location, temperature variations, pollution, etc.) to completely generalize the recommendations. It is my experience that reliability of SRVs can only be determined on a historical basis for each individual installation, application, location and even type of SRV. The variety of applications and types of valve makes it impossible for us to correlate meaningful information with relation to such events as failure rates for all industries however, we can track the individual valve and its health. I would compare the frequency for inspecting the valves with regular doctor check-ups. For instance, the older you get, the more frequent will be your doctor check-ups if you work in a dangerous environment, the more frequently you should see a doctor. 

Conclusion The difference in purchasing price between a pilot valve and a balanced bellows metal-to-metal valve is already compensated after the first maintenance cycle of these valves. This is an ROI of less than 1 year if the attached recommended maintenance frequency is followed. 

Unavailable due to maintenance MAN Q — f me Tmc fmc = Corrective maintenance frequency Tmc = Average corrective maintenance time... 

Human error after maintenance HUM Q = HEPfmc Ts fmc = Corrective maintenance frequency HEP = Human error probability... 

The frequency of maintenance should be defined in these SOPs and, unless otherwise justified, should comply with the OEM s recommendations. Maintenance frequencies may be determined by recalibration requirements and reliability-centered preventive maintenance calculations. Advice can be sought from supplier organizations, but it should not be solely relied on because it is highly unlikely that they fully understand the precise nature of the pharmaceutical or healthcare application. Justifications for periodic inspection intervals should be recorded, remembering that they can be modified in the light of operational experience. Any change to recalibrations periods or preventive maintenance intervals, however, must be controlled. 

Areas considered and rated from a maintenance perspective are shown in Table 5. Skip liner maintenance frequency is judged on the velocities and energy noted in Table 3. Transfer chute maintenance frequency is based upon the number of chute direct impact and sliding areas and number of moving components. 

Skip Liner Maintenance Option Frequency Conveyors, Apron Transfer Chute and Feeders, and Associated Loading Pocket Feed Chute Maintenance Maintenance Frequency Frequency ... 

Inspections and even thorough examinations are not substitutes for properly maintaining equipment. The information gained in the maintenance work, inspections and thorough technical examinations should inform one another. A maintenance log should be kept and be up to date. The whole maintenance system will require proper management systems. The maintenance frequency will depend on the equipment, the conditions in which it is used and the manufacturer s instructions. 

There are other secondary concerns, such as the time required to clean the residual from the previous sample, waste generation, storage effects, maintenance frequency, whether the device can be easily decontaminated, and whether data can... 

The fault tree is drawn, and then the Boolean equations and minimal cut sets are derived for the top event. Probability estimates can be generated from hardware failure data, human error estimation, maintenance frequency, etc. Probability estimates are then assigned to the events. Be sure to take into consideration uncertainty limits to your failure data. Through the laws of probability, combine the... 

Mold release behaviour , wear , corrosion or maintenance frequency are just some of the practical everyday issues faced by plastic processing contractors. Surface finishing can make a decisive contribution to optimizing molds in service, and to the efficiency of new molds. The aim is to reliably produce end products of suitable quality over the longest possible production period. There are now numerous classic... 

The modelling was carried out with stochastic Petri nets with predicates and the software used was the Petri net module of GRIF, developed by SATODEV. The results obtained in terms of frequency of failure, percentage of planned and unplanned downtime, and especially costs, make it possible to suggest areas where preventive maintenance frequencies can be optimised. 

Based on this model, changes to the preventive maintenance frequencies were made -i-50%, +100%, +150%, +200% of the initial period. 

In term of results, this figure shows also that total downtime remains stable, with the two above-mentioned trends cancelling each other out. An increase was also observed in total downtime when preventive maintenance frequencies were doubled. This gives a limit that cannot be exceeded if we wish to maintain the same level of availability while reducing preventive maintenance. 

Indeed, the initial results show that preventive maintenance frequencies can be doubled, thus reducing preventive maintenance costs by 50%, while maintaining the same level of system availability. However, a more refined analysis is needed in order to identify the optimum frequency for critical equipment in terms of availability and cost. 

Compared to the theoretical case, the strategy that consists to estimate the parameter for each path gives results that show an increase of corrective maintenance frequency (Tables 2a, 3a and 4a). 

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