Maintenance interval

The most versatile arrangement, from an operations point of view, is individual transfer valves, one for the twin coolers and one for the twin filters. The use of one valve for both the filter and cooler results in a loss in flexibility, as the cooler maintenance interval is usually somewhat longer term than a filter changeout. Should one cooler be out of service, and the filter that is paired with the operating cooler be fouled, the compressor will have to shutdown. Each user will have to review the extra cost oi a second valve against the operation limit. 

A laboratory should draw up a plan of what performance checks are required for each instrument, why they are necessary and how they should be carried out. Maintenance intervals and performance checks for certain instruments are documented in the CITAC/Eurachem Guide to Quality in Analytical Chemistry [14]. 

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. 

With ceramic membranes (typical pore size 0.2 pm) this legal limit of 10 ppm is easily obtained [18]. Average membrane flux is 150 1/m h values are reported between 125 and 6001/m h [19]. The interval between cleanings or the maintenance interval can amount to 1000 h. By combination of the membrane unit with a static separator the concentration factor can be as high as 180, the oil content in the final concentrate can amount to over 90%. The pay-back time for such an installation would be less than two years at a cost of NLG 94/m effluent, and related to the present costs of treatment [18]. 

Keeping in mind these insights, we turn to a second application of the model, the estimation of the lifetime of a catalyst bed. This is an important consideration in the design of any reactor and is particularly critical in transportation applications where maintenance intervals must be well known. As an initial approach to developing metrics for this analysis we define Ae time in service or service life, at constant wall temperature, as the duration when the overall conversion in the reactor (for full power output) is greater than 85%. This conversion was chosen because it is close to the autothermal point of operation where the burning of unreacted methanol will just balance the endothermic heat of reaction. A reference catalyst mass was determined by requiring a methanol conversion of 85% at the wall temperature of 240"C for fresh catalyst. 

After establishing the maintenance types, the maintenance time interval should be determined. Maintenance time interval refers to the interval between the maintenance work and inspection. Maintenance time interval directly influences the security and economy of devices. Over long maintenance time interval may fail to guarantee the security and usability of devices for those faults bringing consequences in security and usability. As for the fault with consequences in economy, over short or long maintenance time interval will influence the economy. When new devices come into service, due to the lack of information, it is hard to determine the maintenance time interval. Accordingly a conservative initial maintenance interval... 

Items Specific Maintenance rules Maintenance interval. 

During inter-maintenance interval, the program and the process of the CRC withdrawal from the reactor vessel were developed, and all necessary devices were designed and manufactured. 

All bearings in the CRD are precision ball bearings which are lubricated with a special grease that has been developed for this type of low radiation and moderate temperature application. This lubricant, which is also used in the harmonic drive components, has been subjected to long duration tests in helium. Therefore, the possibility of bearing or speed reducer seizure from deterioration of the lubricant is minimized. Relubrication of these components at regular maintenance intervals is planned. 

Lapp, S., 2005. Applications of fault tree analysis to maintenance interval extension and vulnerability assessment. Process Saf. Progress. 

The objective of preventive maintenance is to extend the life of an item and prevent all failures before they occur by detecting critical wear that leads to failure or breakdown. This can be accomplished by estimating a lifetime schedule for each item. The way this estimation takes place determines the type of preventive maintenance. In predetermined maintenance the estimation is static and results in static maintenance intervals. In condition-based maintenance, maintenance intervals are determined according to either the detection of a degradation mechanism by monitoring or a forecast derived from the analysis and evaluation of a number of parameters (i.e., vibration, imbalance, machine noises, power demand) of the degradation mechanism (thus, condition-based maintenance is often referred as predictive maintenance). 

Using such distributions of the remaining life of an item, the remaining life for an item for which a failure can be prevented by replacing or servicing the item is calculated and thus the preventive maintenance intervals for the item determined (Lanza et al. 2009 Gertsbakh 2006). 

Serviceability Caterpillar designed the 797 to reduce service time thus ensuring maximtun availability. Routine maintenance points, such as fluid fill and check points, are close to ground level. Easily accessed connectors allow technicians to download data and to calibrate machine functions, thus extending maintenance intervals which further increases availability. The 797 is also designed to make major components accessible, which effectively reduces removal, installation, and in-truck maintenance time for all drivetrain components. 

Where certain redundant systems and components are kept on standby, operation of these systems and components should be rotated in order to subject all components to similar operating times and thus to similar surveillance procedures and frequencies. Maintenance intervals should be adjusted to ensure that not all systems and components wear out at the same time. 

Actual MTBF experienced will probably differ from predicted MTBFs used in FTA calculations during initial certification. Direct advantages are possible if the FTA can be updated with actual MTBF data either action can be taken to improve safety or (if the predicted MTBFs were very conservative) maintenance intervals can be increased. 

As the staple graph coincidence permutation diagram opens the first level of abstraction, then the second level is represented by the coincidence permutation tree, see Fig. 9. Here, the number of involved systems and the maximum number of overlapping maintenance interval are graphically described. Note that the permutations with non-involved systems are not considered here. The purpose of both diagrams is to simplify the collecting of pattern probabilities as shown in Section 5. 

The problem of dike-heightening is similar to the problem of maintenance optimization the imcertain occurrence of failures affects the planning and timing of preventive maintenance actions. When using a risk-based decision rule, the optimal time between repairs is often determined by the interval with the lowest present value of the costs involved. Due to the probabilistic nature of such an approach, this value is uncertain and the expectation is used for decisionmaking. However, practical experience has shown that the variance of this optimum is usually quite large see, for example. Van Noortwijk (2003). In these cases, it is desirable to choose a maintenance interval which is less optimal, but of which the outcome is less uncertain. en making such a decision one is often said to be risk averse. 

This section focuses in the comparison of results obtained when methods presented in section 2 are implemented to analyse uncertainty propagation in the problem of optimizing maintenance intervals of a motor-operated valve in safety equipments of a nuclear power plant. These equipments consist in two main components, actuator and valve, in serial configuration and working independently. So, the problem considers how the uncertainty associated to some initial parameters in the input vector affect on system leUability and cost (R-fC) as decision criteria. 

Then, optimization of preventive maintenance intervals under reliability and cost criteria (R+C) is tackled. The equipment reliabihty and its associated cost are quantified, using analytical models, as functions of parameters obtained in the estimation process together with maintenance intervals in each component as decision variables. Both, equipment reUabHity and cost functions, are considered to be deterministic in the sense that when all necessary input data for the model are specified they provide only one value for every output. That is, following notation introduced in last section, input vector is x = (jS, jj, sa, a, ey) which is transformed by the simulator to the output vector through the mentioned analytical models V(P, r),sx,a,sy) = (C,R) = y. 

This paper presents an analysis of the results obtained in the preventive maintenance interval optimization of a safety related equipment based on rehability and cost criteria and considering that reliability parameters and maintenance effectiveness are random variables which introduce uncertainty in the decision making process. 

Looking at Fig. 5, it can he seen that the ARAco model leads to a quicker start of aging and, for constant maintenance intervals and efficiency, to a cyclic... 

An RCM optimization module enabling calculation of effective failure rates for common RCM activity types, i.e., age replacement, functional proof testing, inspection in time-delay models and a gradual failure progression model, see e.g. Vatn (2007) for a description of these models. The RCM module enables maintenance interval optimization taking the entire regularity model into accoimt. 

Vaurio, JK. 1995. Optimization of test and maintenance intervals based on risk and cost. Reliability Engineering and System Safety 1995 49 23-36. 

Selecting and acquiring medical equipment Evaluating and identifying equipment to be included in the plan Determining scheduled maintenance intervals and procedures Repairing and maintaining patient care equipment... 

The time interval during which the reactor could be left in autonomous operation would depend on design details and opotating needs. For example, periodic operator action would be needed to keep the primary cooling water chemistry from drifting beyond acceptable limits. If need be, a timer clock could be used to initiate reactor shutdown automatically if it is not reset by an operator at the required maintenance intervals. 

The reliability of a plant is a sum of reliabilities of all the equipment, instruments, and other hardware. The reliability of each item of equipment is estimated based on its past operational performance (failure rates, repair durations, etc.) and on current maintenance practices (preventive maintenance intervals and durations, test intervals, etc.). Once the economic impacts of various scenarios in which units or major equipment items fail has been established, the required safety features can be designed (e.g., profit-risk scenario and minimal cutoff could be established) (see Fig. 8.10). To the left of the dotted line in the figure, the litigation cost is higher than the cost of safety features the reverse trend exists on the right of the dotted line. 

PFRs can deal with very high volumes of reactants and quickly deliver very high product yields. Able to operate at high temperatures, PFR heat control has remained challenging. While PFRs have long maintenance intervals, their eventual servicing is more costly than for GSTRs or batch reactors. 

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