Error design

Figure 1.15(b) provides some insight into the reasons for the meehanieal failures experieneed. Some root eauses of failure are found to be improper material seleetion, fabrieation imperfeetions and design errors. Other eauses of failure are ultimately... 

Distributor switched from feed to reflux. (Drawing wrong) Everything looked good except separation. Liquid maldistribution problem. Design error. 

Support plate used as a vapor distributor with restricted open area. Reduced capacity in order to make separation. Design error. 

Bottom draw nozzle too small. Pump cavitation problem. Raising tower 10 feet did not help. Flooded the bottom of the tower. Design error in original plant. 

Downcomers sized too small for actual flow. Limited capacity. Design error. 

Pipe downcomers from chimney tray too small for flow. Poor separation. Slightly higher pressure drop. Design error. 

Hats on chimney tray excessively restricted vapor resulting in liquid entrainment. Design error. 

Chimneys (risers) blocking flow to draw sump forcing liquid to overflow prematurely. Flooding of trayed section below pump around. Lack of response to pump around flow changes. Design error. 

Reboiler return line sized too small. Poor separation limited capacity. Unstable operation. Expansion design error. 

Improper tray spacing at feed location. Premature flooding. Design error. 

Materials evaluation and selection are fundamental considerations in engineering design. If done properly, and in a systematic manner, considerable time and cost can be saved in design work, and design errors can be avoided. 

CCF means different things to different people. Smith and Watson (1980) define CCF as the inability of multiple components to perform when needed to cause the loss of one or moi e systems. Virolainen (1984) criticizes some CCF analyses for including design errors and poor quality as CCF and points out that the phenomenological methods do not address physical and statistical dependencies. Here, CCF is classed as known deterministic coupling (KDC), known stochastic coupling (KSC), and unknown stochastic coupling (USC). 

Operational Error Design Error Process Upset Mechanical Failure Unknown Natural Hazard Sabolage/Arson... 

Rasmussen (1989) Study of 190 accidents in CPI facility Top 4 causes insufficient knowledge 34% design errors 32% procedure errors 24% personnel errors 16%... 

Analysis of accidents and major losses in the CPI indicates that they rarely arise from a single human error or component failure. Often there is a combination of some triggering event (hardware or human) together with preexisting conditions such as design errors, maintenance failures or hardware deficiencies. 

Motivational campaigns are one way of dealing with routine violations (see Section 2.5.1.1). They are not directly applicable to those human errors which are caused by design errors and mismatches between the human and the task. These categories of errors will be discussed in more detail in later sections. 

Corrosion (direct cause) due to Design error (basic or root cause) not recovered by Inspection (failure of recovery)... 

The primaiy causes of accidents arc mechanical failure, operational failure (human error), miknown or miscclhmcous. process upset, and design error. Figure 14.4.1 is the relative number of accidents that liave occurred in tlie petrochemical field (on a percentage basis), There are lliree steps that normally lead to an accident ... 

Design Error Process Upset Unknown Operational Error Mechanical Failure... 

Design error Process upset Unknown Operational error Mechanical taiiure... 

Accidents in industry occur for many reasons. A few of which can be attributed to mechanical failure, operational error (human error), and process upset, and design error. In order to understand tlie root cause of an accident, system safety appraaches have been put to use. 

Contractor designs will be in the context of a competitive bidding situation and in-company checks of the design should cover not only design errors but also cases where calculated risks have been taken, which may not, however, be acceptable to the operating company. 

Inhibitors of AR have been demonstrated to prevent a wide variety of biochemical, functional and structural alterations in animal models of diabetes. Early studies demonstrated arrest of both early cataract development and nerve conduction velocity. At least 30 clinical trials of AR inhibitors have been published involving nearly 1000 patients in total. However, there is little impressive data of their efficacy up to now but, rather than undermine the hypothesis linking excess polyol pathway activity to diabetic complications, it may reflect methodological difficulties and trial design errors. 

Contingency allowance, this is an allowance built into the capital cost estimate to cover for unforeseen circumstances (labour disputes, design errors, adverse weather). Typically 5 per cent to 10 per cent of the direct costs. 

Failures can either be fail-safe or fail dangerously. Fail safe incidents may be initiated by spurious trips that may result in accidental shutdown of equipment or processes. Fail dangerously incidents are initiated by undetected process design errors or operations, which disable the safety interlock. The fail dangerously activation may also result in accidental process liquid or gas releases, equipment damage, or fire and explosions. 

Error Avoidance Strategies for the Industry, Designing Error out of Products... 

---