Assembly, incorrect

How often has this been said by the designer after a piece of equipment has failed The designer is usually correct, but whenever possible we should use designs that are impossible (or difficult) to assemble incorrectly or that are unlikely to fail if assembled incorrectly. For example ... 

The best way to prevent accidents such as this is to use rupture discs, which are harder to assemble incorrectly and which can be checked for correct installation after assembly. It is possible to get discs permanently attached to their vacuum supports by the manufacturer and fitted with a projecting tag, which carries the words vent side on one side. The tag also gives the pressure rating. 

Because eicosahedra are regular geometric solids and the faces can be made up of hexons and pentons of identical subunits, it might seem that self-assembly of eicosahedral viruses would occur easily. However, the subunits usually must be able to assume three or more different conformations and the shells can easily be assembled incorrectly. Several stategies are em-... 

ASl Assembly Incorrect propulsion/control during rendezvous 4 4 4... 

Analysis of consistency. Complex networks of assembly relationships are not easy to understand by engineers during the design and modification of assemblies. Incorrect definition and... 

These advantages include (a) Speed of assembly, (b) Well-fitting joints as these are made to accurate standards and joints of any given size are thus interchangeable, (c) Accurate alignment of assembly, for the use of incorrectly bored corks is obviated, d) Freedom from contamination of liquids by cork and rubber. 

Fig. 17. Testing modules before each assembly step and rejecting incorrect samples (a) E, an erroneous copy, is rejected whereas (b) C, a correct copy, is...

Avoiding Incorrect Assembly Plants should be designed so that incorrec t assembly is difficult or impossible. For example, compressor valves should be designed so that inlet and exit valves cannot be interchanged. 

Status Clear It should be possible to see at a glance if equipment has been assembled or installed incorrectly or whether a valve is in the open or shut position. For example-. 

PISTON ROD OIL SCRAPER LEAKS 1. Worn scraper rings. 2. Scrapers incorrectly assembled. 3. Worn/scored rod. 4. Improper fit of rings to rod/side clearance. 

Mistake-proofing can be accomplished by product design features in order that the possibility of incorrect assembly, operation, or handling is avoided. In such cases the requirements for mistake-proofing need to form part of the design input requirements for the part. 

As discussed in Section 3.2.1, equipment should be designed so that it is difficult or impossible to assemble it incorrectly or so that the incoirect assembly is immediately apparent. 

By making incorrect assembly impossible (for an example, see Section 9.1.3). 

Fines should normally be kept as short and free of bends as possible. However, tubing should not be assembled in a straight line, because a bend tends to eliminate strain by absorbing vibration and compensates for thermal expansion and contraction. Bends are preferred to elbows, because bends cause less loss of power. Some of the correct and incorrect methods of installing tubing are illustrated in Figure 40.26. 

Two major sources of vibration due to mechanical imbalance in equipment with rotating parts or rotors are (1) assembly errors and (2) incorrect key length guesses during balancing. 

To verify that a proposed reaction mechanism agrees with experimental data, we construct the overall rate law implied by the mechanism and check to see whether it is consistent with the experimentally determined rate law. However, although the constructed rate law and the experimental rate law may be the same, the proposed mechanism may still he incorrect because some other mechanism may also lead to the same rate law. Kinetic information can only support a proposed mechanism it can never prove that a mechanism is correct. The acceptance of a suggested mechanism is more like the process of proof in an ideal court of law than a proof in mathematics, with evidence being assembled to give a convincing, consistent picture. 

In a previous section we mentioned the significance of myosin filament structure. In nematodes two forms of myosin-II, myosin A and B, are required for proper filament stmcture (Epstein, 1988). The two forms of myosin are expressed at the proper time to allow for correct filament assembly. An accessory protein called paramyosin is also required for correct filament assembly. In vertebrate cardiac muscle, there are also two isoforms of myosin-II a-myosin and p-myosin. The proper ratio of these two proteins is of utmost importance for proper muscle activity. The incorrect synthesis of a- and P-myosins results in a severe cardiac disorder known as hypertrophic cardiomyopathy. Genetic transmission of the disease occurs in about 55% of families. The inherited condition is called familial hypertrophic cardiomyopathy (FHC), and this condition is a leading cause of sudden death in young athletes. 

Incorrect assembly of plant made impossible by equipment design. 

The formation of a transcriptionally active complex requires the interaction of all transcription cofactors with their respective specific DNA sequences. Once they have bound to their specific sequences, it is on these that the remaining elements of the complex that do not interact directly with the DNA are assembled (Chin 1995 Filardo 2002). The elements of the complex that do not come into direct contact with DNA have their own specificity of interaction with the remaining proteins of the complex. Therefore, they include important restrictions so that a fully active transcriptional complex can be assembled with difficulty on a receptor dimer that has incorrectly recognized a HRE. Indeed, an incorrect interaction can imply a noticeable degree of transcription inhibition. 

The tetraene precursor 14, assembled in a similar way to 11, underwent smooth cyclization using the ruthenium initiator 3 (0.1 equiv) to give macrolactone 15, again in good yield and with complete E-selectivity. Despite the incorrect olefin geometry, transformation into epoxides 16 provided further encour-... 

Safe plants are designed so that incorrect assembly is difficult or impossible. Assembled components must meet their design requirements. A loss of containment may result from using eg. a wrong type of gaskets. 

Making Incorrect Assembly Impossible -choice of equipment, piping and fittings correctly equipment safety safe process structure... 

Firstly, it should be noted that predicted service life cannot take into account poor workmanship, incorrect use or maintenance, faults due to an assembly of components where each one is only tested individually, or unexpected operating conditions. 

Problems with service experience include obtaining sufficient information on the actual conditions of service, finding that these conditions are much milder than the design conditions, or that the polymer formulation used has now been superseded. Life prediction cannot consider failures caused by poor workmanship, incorrect use or maintenance, or faulty design, particularly of joints, attachments or in the choice of neighbouring materials. Many failures in practice are due to degradation in processing, faulty assembly, or to abuse. 

---