Operating conditions abnormal

In Table 11.6 the values of colurrm 2 relate to normal operating conditions. Abnormal conditions may prevail when the machine is exposed to overhead lines, the... 

These applications have considerably more stringent performance requirements than any other application. Circulating water pumps, boiler feed pumps, forced-draught (FD) and induced-draught (ID) fans, pulverizers (ball mills) and condensate pumps are components in a thermal power station that may require extra safety in a standard motor to make it able to fulfil these requirements and withstand abnormal service conditions and system disturbances. Abnormal operating conditions may be one or more of the following ... 

Protection against overloading This can be achieved by an overcurrent relay. The basic requirement of this relay is its selectivity and ability to discriminate between normal and abnormal operating conditions. Three types of such relays are in use thermal, electromagnetic and static. Thermal relays are employed for motors of up to medium size and electromagnetic and static relays for large LT and all HT motors, as discussed in Section 12.5. 

Most often, the bearing or the lubricant is blamed for the failure. This is like blaming the fuse for an electrical failure. The failure is most likely a result of some abnormal operating condition, or lack of proper maintenance. In short, something causes the bearing to fail prematurely. 

Use materials that are applicable over the full range of operating conditions such as normal, startup, routine shutdown, emergency shutdown, and draining the system. For example, carbon steel may be acceptable for normal operating conditions but may be subject to brittle fracture at low temperatures under abnormal conditions (as in the case of a liquefied gas). Cold water, of less than 60°F, during hydrotest may cause brittle fracture of carbon steel. 

A nonincendive device is one which will not release sufficient energy under normal operating conditions to ignite a specific substance. Under abnormal conditions, such as a malfunction of the device, it may release enough energy to cause ignition. Because of this, such devices are suitable for use only in Division 2 and unclassified areas. 

A variety of electromechanical relays was used for the detection of abnormal operating conditions (e.g., overload, short-circuit, etc.), leading to the isolation of the faulty components. In the second half of the twentieth century electromechanical relays were progressively replaced by electronic controls that arc capable of faster response and higher reliability. 

The fact that both normal and abnormal machine dynamics tend to generate unbalanced forces in one or more directions increases the analyst s ability to determine the root-cause of deviations in the machine s operating condition. Because of this, measurements should be taken in both radial and axial orientations. 

Abnormal operating conditions or neglecting necessary maintenance precautions cause most bearing failures. Bearings may experience premature and/or catastrophic failure on machines that are operated heavily loaded. 

Topics should embrace a knowledge of the hazards and precautions, including the use and maintenance of protective devices including personal protection, under both normal and abnormal operating conditions including emergencies. 

Distinguish normal from abnormal operating conditions (Bastl and Fenkel, 1980 Long and Kanazava, 1980). 

We can, however, consider the stability of each of the three operating points in Example 14-7 with respect to the inevitable small random fluctuations in operating conditions, including cA, in steady-state operation. Before doing this, we note some features of the rate law as revealed in Figure 14.4. There is a maximum value of (- rA) at cA = 1.166 mol m-3. For cA < 1.166, the rate law represents normal kinetics ( rA) increases as cA increases for cA > 1.166, we have abnormal kinetics (—rA) decreases as cA increases. We also note that (-rA) in equation (C), the rate law, represents the (positive) rate of disappearance of A by reaction within the CSTR, and that (—rA) in equation (D), the material balance, represents the (positive) net rate of appearance of A by flow into and out of the reactor. As noted above, in steady-state operation, these two rates balance. 

The main business of most chemical companies is to manufacture products by means of controlled chemical reactions. The reactivity that makes chemicals useful can also make them hazardous. Chemical reactions are usually carried out without mishap, but sometimes they get out of control because of problems such as the wrong or contaminated raw material being used, changed operating conditions, unanticipated time delays, failed equipment, incompatible materials of construction, or loss of temperature control. Such mishaps can be worse if the chemistiy under both normal and abnormal conditions is not fully understood. Therefore, it is essential that chemical process designers and operators understand the nature of the reactive materials andchemistry involved and what it takes to control intended reactions and avoid unintended reactions throughout the entire life cycle of a process facility. 

Operation qualification involves a high degree of dynamic testing of the computer system in conjunction with the controlled process. It normally uses an alternative medium to represent process conditions, and can be performed in conjunction with plant and equipment engineering commissioning. Operation qualification testing may include both normal and abnormal operating conditions. 

As concerns the former, statistical tests on the measured data are usually adopted to detect any abnormal behavior. In other words, an industrial process is considered as a stochastic system and the measured data are considered as different realizations of the stochastic process. The distribution of the observations in normal operating conditions is different from those related to the faulty process. Early statistical approaches are based on univariate statistical techniques, i.e., the distribution of a monitored variable is taken into account. For instance, if the monitored variable follows a normal distribution, the parameters of interest are the mean and standard deviation that, in faulty conditions, may deviate from their nominal values. Therefore, fault diagnosis can be reformulated as the problem of detecting changes in the parameters of a stochastic variable [3, 30],... 

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