Engineering and Construction

Fatigue loadings must be considered, but even where fatigue turns out not to be a design criterion, it is vital to protect against vibration and consequent loosening of bolted assemblies. In this respect HSFG bolts are commonly used as they dispense with the necessity to provide a lock-nut; when correctly specified and installed they also display good fatigue-resistance.

However, just as plant engineers can display a lack of understanding about the necessity to design supporting steelwork afresh for each different structure even though the ‘same’ plant is being built, structural steelwork engineers must be aware that seemingly identical or repeat pieces of plant or equipment can in fact vary in significant details.Most plant installations are purpose-designed, and the layout and loadings are often provided initially to the structural engineer in terms of estimated or approximate values. It is vital to be aware of the accuracy of the information being used for design at any stage, and to avoid carrying out designs at an inappropriately advanced level.A considerable margin should be allowed, provided that it is established that the plant designers have not allowed a similar margin already in estimating the plant loadings. Experience shows that loadings are often over- estimated at the preliminary design stage, but that this is compensated for by new loadings at new locations that were not originally envisaged.