Mechanical reliability, equipment

The chemical process industries (CPI), petroleum and allied industries apply physical as well as chemical methods to the conversion of raw feedstock materials into salable products. Because of the diversity of products, process conditions and requirements, equipment design is often unique, or case specific. The prime requirement of any piece of equipment is that it performs the function for which it was designed under the intended process operating conditions, and do so in a continuous and reliable manner. Equipment must have mechanical reliability, which is characterized by strength, rigidness, steadiness, durability and tightness. Any one or combination of these characteristics may be needed for a particular piece of equipment. 

Process Reliability Simulation VIP The process reliability simulation VIP is the use of reliability, availability, and maintainability (RAM) computer simulation modeling of the process and the mechanical reliability of the facility. A principal goal is to optimize the engineering design in terms of life cycle cost, thereby maximizing the project s potential profitability. The objective is to determine the optimum relationships between maximum production rates and design and operational factors. Process reliability simulation is also applied for safety purposes, since it considers the consequences of specific equipment failures and failure modes. 

Noncontact Seals Noncontact seals are used extensively in gas service in high speed rotating equipment. These seals have good mechanical reliability and minimum impact on the rotor dynamics of the system. They are not positive sealing. There are two types of non-contact seals (1) labyrinth seals and (2) ring seals. 

These two successful commercial applications of rotating packed beds prove that scale-up from pilot-scale equipment can achieve the desired process performance in commercial-scale operations. In addition, the mechanical reliability of the rotating equipment is in line with the experience with other rotating... 

The fourth item covers various other costs resulting from a lack of mechanical reliability. An example of costly remedial measures being employed as a result of minor mechanical difficulties has already been quoted in the section on seals, in which extensive ventilation systems were installed as a result of leakage of toxic fumes. As another example in this category, the user may be forced to consider installing additional spare equipment, or additional facilities for stockpiling product, if particularly severe and prolonged problems are experienced. 

The first step in the process is risk identification, which is accomplished by review of the proposal/study by suitably experienced experts using well-considered checklists. These must embrace all facets which may affect the project outcome, such as plant feedstock quality, process reliability, mechanical reliability, potential foundation problems, operational hazards, environmental impact, equipment costs, construction costing and labour, statutory requirements, contractual and legal problems peculiar to the country of construction, eventual decommissioning costs, and so on. Risks due to operational hazard are generally treated separately from commercial risk, and will be discussed in Chapter 12, but they are obviously an essential part of the overall process. 

The manner is which an exchanger is piped up influences its performance. Horizontal units should have inlet and outlet nozzles on the top and bottom of the shell or channel. Nozzles should not be on the horizontal centerline of the unit. In general, fluids should enter the bottom of the exchanger and exit at the top, except when condensation occurs. Units are almost always designed to be counterflow and the piping must reflect this. When concurrent flow has been specified, it is equally important that equipment be piped to suit. For multipass units, the shellside fluid can be admitted at either end of the shell without affecting the thermal performance. However, for some cases better distribution or mechanical reliability can be achieved with the inlet nozzle at a specific location. 

The plant engineer should bear in mind that the control system comprises, besides the detecting element and the controller, also the final control element, which is generally a feature of the electrical and/or mechanical engineering equipment of the plant. It is this equipment that is of major importance in deciding the efficiency of a control method. Thus, if it lacks the necessary reserve capacity, accuracy or reliability, the value of the control system as a whole will be impaired. 

Many North American companies are concerned that lead-free components and assemblies will not meet the reliability or functionality requirements necessary for high-end equipment supplied to banks, air traffic control systems, web-based businesses, and other mission-critical applications. Accordingly, manufacturers of aerospace and military electronics have no plans to introduce lead-free solders. There are too many reliability concerns to utilize lead-free solder materials in high-reliability equipment related to the mechanical characteristics of the materials themselves and the effects of high temperatures to process them. The effect of new and modified intermetallic compound phases within solder joints and at the interfaces is yet an additional concern, and there are many more. 

The IEEE Guide to the Gollection and Presentation of Electrical, Electronic, Sensing Gom-ponent, and Mechanical Equipment Reliability Data for Nuclear Power Generating Stations (IEEE Std. 500-1984) compiles data from over a dozen other references and includes information for most types of components. 

The units and ancillary equipment must be protected from mechanical damage and the effects of weather to ensure the reliable operation of an impressed current station. This is achieved by installing it in a weatherproof plastic housing (see Fig. 8-2). Sufficient ventilation must be provided to disperse heat. The ventilation holes should be protected with brass gauze to keep out animals. Transformer-rectifier units must be connected to a circuit that is continuously energized, especially if they are in a building where the current is turned off at night, e.g., gas stations that are not open for 24 h. 

Jones, G. 1978 In Proceedings of Conference on Reliability of Aircraft Mechanical Systems and Equipment. Instn Mech. Engrs, MOD and RaeS, London, 61-IQ. 

Now let us consider utility failure as a cause of overpressure. Failure of the utility supphes (e.g., electric power, cooling water, steam, instrument air or instrument power, or fuel) to refinery plant facihties wiU in many instances result in emergency conditions with potential for overpressuring equipment. Although utility supply systems are designed for reliability by the appropriate selection of multiple generation and distribution systems, spare equipment, backup systems, etc., the possibility of failure still remains. Possible failure mechanisms of each utility must, therefore, be examined and evaluated to determine the associated requirements for overpressure protection. The basic rules for these considerations are as follows ... 

Guide to the Collection and Representation of Electronic, Sensing Component, and Mechanical Equipment Reliability Data for Nuclear Generating Stations. IEEE Standard 500-1984, Institute of Electrical and Electronics Engineers, New York, 1984. 

The purpose of predictive maintenance is to minimize unscheduled equipment failures, maintenance costs and lost production. It is also intended to improve the production efficiency and product quality in the plant. This is accomplished by regular monitoring of the mechanical condition, machine and process efficiencies and other parameters that define the operating condition of the plant. Using the data acquired from critical plant equipment, incipient problems are identified and corrective actions taken to improve the reliability, availability and productivity of the plant. 

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