Inadvertent failure causes

We note that with regards to divergence, for example, the systematic aligiunent to a safe state in case of detected failure is generally irrelevant for HIPS whose inadvertent failures can cause other safety issues (risk at restart, water hammer, demands on other safety systems, human error, etc.) excluding production losses, which can be considerable. It follows that beyond the SIL, the probabihfy of a spurious failure is also an important design criterion. 

During the process operation, water was introduced into the blender, probably as a result of a mechanical failure. Operators noticed the production of heat and the release of foul-smelling gas. During an emergency operation to offload the blender of its reacting contents, the material ignited and a deflagration occurred. The most likely cause of this incident was the inadvertent introduction of water into water-reactive materials (USEPA-OSHA, 1997). 

When oxytocin is used judiciously, serious toxicity is rare. The toxicity that does occur is due either to excessive stimulation of uterine contractions or to inadvertent activation of vasopressin receptors. Excessive stimulation of uterine contractions before delivery can cause fetal distress, placental abruption, or uterine rupture. These complications can be detected early by means of standard fetal monitoring equipment. High concentrations of oxytocin with activation of vasopressin receptors can cause excessive fluid retention, or water intoxication, leading to hyponatremia, heart failure, seizures, and death. Bolus injections of oxytocin can cause hypotension. To avoid hypotension, oxytocin is administered intravenously as dilute solutions at a controlled rate. 

For the meaningful deviations identified by the procedure described above, the possible causes for triggering the deviation are systematically searched. As an example, possible causes for no flow may be an empty feed tank, a closed valve, an inadvertently open valve to another direction, a pump failure, a leak, and so on. In this context, it may be useful to indicate the logical relationship between the causes, such as where simultaneous failure of several elements is required in order to trigger the deviation. This is of great help for the assessment of the probability of occurrence. 

Elevated aluminum levels have been implicated as the cause of dialysis encephalopathy or dementia in renal failure patients undergoing long-term hemodialysis [85]. Some patients used aluminum-containing medications. Moreover, patients with renal failure cannot remove aluminum from the blood. Dialysis dementia can arise after three to seven years of hemodialysis treatment. Speech disorders precede dementia and convulsions. Since many hemodialysis units rely on systems to purify fluoridated tap water, it is likely that many patients are being exposed inadvertently to increased concentrations of fluoride and aluminum. Increased serum fluoride concentration and fluoride intoxication have been also observed in chronic hemodialysis patients. Arnow et al. [96] reported that 12 of 15 patients receiving dialysis treatment in one room became acutely ill, with multiple non-specific symptoms and fatal ventricular fibrillation. Death was associated with longer hemodialysis time and increased age compared with other patients who became ill. 

Where two or more preparations are being used, an interval of 15 min should be left between instillations to avoid losses by inadvertent elution, dilution or inactivation. Failure to do so is a common cause of therapeutic failure. 

Well-casing failure. Corrosive wastes can cause the failure of casing and packing and inadvertently inject wastes into other formations. 

Undesirable rod motion can result from control system failure and can be either inward or outward. Inward motion is a plant availability problem, but is not a safety concern. The extreme case of undesirable inward motion is an inadvertent reactor trip. This event might be caused by a loss of power or erroneous trip signals. This event places the plant in a safe condition. 

Equipment failures can be primary, secondary, or command. A primary failure is one that occurs under normal operating conditions and for which the component itself is responsible. A secondary failure is one that is caused by external conditions or factors and for which the equipment item itself cannot be held responsible. For example, if a corrosive liquid is inadvertently fed to a pump, then the subsequent failure of the pump is secondary. A command failure is one that is caused by... 

In short, an important general moral of this case is that choosing too narrow a system context within which to situate one s design work on a technological device can lead to cognitive myopia. This can result in failure to consider some possible downstream harms, an inadvertent but blameworthy violation of the FEREl responsibility to not cause harm or contribute to creating an unreasonable risk of harm, by commission or omission. 

It should be emphasized that a FMEDA provides failure rates, failure modes and diagnostic coverage effectiveness for random hardware failures. If done properly, it does not include failure rates due to "systematic" causes including incorrect installation, inadvertent damage, incorrect calibration or any other human error. 

A similar reaction of ethyl levulinate was conducted with a UF preparation. The acid-catalyzed reaction incorporated the levulinate into the resin structure, forming aii insoluble mass. This reaction does not occur to a large extent during the initial particle board degradation owing to the large volume of ethanol solvent however, it can cause a problem in the workup of the products after the ethanol has been removed. The reaction explains the failure of attempts to distill ethyl levulinate directly from the levulinate-resin product mixture without prior extraction of the ester from the resin. These attempts resulted in low ester yields and the formation of intractable resin. Thus, by extracting the ester we can avoid the inadvertent condensation reaction with the resin. 

Damage The partial or total loss of hardware caused by component failure exposure of hardware to heat, fire, or other environments human errors or other inadvertent events or conditions (MIL-STD-882). 

Total loss of feedwater flow may be caused by de-energization of the feedwater pump motors and by failure of the oil cooling of these pumps, as well as by inadvertent closing of isolating and/or control valves on the feedwater lines. The transient is characterized by a pressure drop in the coolant circuit and by a reduction of the MCP cavitation margin. 

Reactor pressure increase Several events may cause this e.g., inadvertent closure of one turbine control valve, pressure regulator downscale failure, generator load rejection, turbine trip MSIV closure, loss of condenser vacuum, loss of nonemergency AC power to station auxiliaries, loss of feedwater etc. All these have been analysed. Features are included in the instrumentation and control systems or redundancies to maintain reactor pressure through a combination of component automatic responses or operator actions, depending on the identified cause. 

---