Cement, Energy and Environment

\ ...-.. .... Summary of observations of the fan vibrations mm/sec (vibration velocity) Sample Size Total Range Day 1 2 3 4 8.0 8.0 8.5 9.0 33.5 1.0' 2 7.5 8.0 7.0 7.5 30.0 1.0 3 8.0 8.5 9.0 8.5 34.0 1.ci >t ... 4 7.0 8.5 6.5 7.0 29.0 2.0 5 8.0 8.5 9.0 9.0 34.5 1.0 6 7.0 8.0 7.5 7.5 30.0 1.0 7 8.5 8.0 8.5 7.0 32.0 1.0 8 9.0 9.0 9.5 9.5 37.0 0.5 9 7.5 7.0 8.5 8.0 31.0 1.5 10 7.0 7.5 7.0 7.5 29.0 0.5 Total 320 10 5 Average Velocity= 320/40 = 8.0 Average Range = 10.5/10 = 1.05 Standard deviation = Average range x multiplying factor For a sample size of 4, from tables, the multiplying factor is 0.49 Standard deviation = 0.49 x 1.05 = 0.5 The following exhibit shows the distribution curve with details of the conditions envisaged. ;., ~ l. \hihil - :;. \ ih.1ltP11 l'r r•":" ltu c:~.· 1'1{ • ' ,. ' / / I I / \kr:L \ \ X.ll \ \ ,, ' The overall average/mean and standard deviation of vibration data are worked out. Effects of unbalance and misalignment etc. have been eliminated prior to recording the observations. It was ensured that the vibrations were caused due to chance variations only. I ._ I~ ~ for a long time, hence the inherent base vibrations could not be el iminated. When the fan was newly mstalled the range of vibrations was from 0 to 1.8 ,lrr, '11 rl!,· ur,·.ur do.. "' \. \1.tlh..'L' \,ar· tl itlfh I I II I Ill ,,, . mm/sec, which satisfied the ISO Standard 2372 under Machine Group 'G' . Gradually the vibrations increased and under the present conditions, the range of vibrations is from 5.0 to 11 .0 mm/sec, which is classified as 'Still Admissible' under the ISO Standard. Us1ng 6-sigma rnn trrrl •'1r> ·~·;II Arimissihle' range nas been llxed as the specification limit and the operating range of vibrations falls 111 the range of 6.5 to 9.5 mm/sec (vibration-velocity). Even if there is a shift of 1.5 sigma from the mean, the fan , remains within control of the specification limits except for 3.4 instances of violations per million opportunities. In this particular case, the abnormal reading identifies the defect, which if prolongs, gives an indication of an unbalance and needs correction. If the machine is not stopped , a breakdown may occur causing more damage, hence more cost. This is a reflection of the need for repair in advance of the breakdown. Quality & Standards STRENGTH DEVELOPMENT For strength development in concrete or in mortar prisms and in almost all applications of cement, the most important clinker constituent is the C 3 S phase, otherwise known as tricalcium silicate or alite. It is the dissolution and precipitation of the calcium silicate phases, C 2 S and C 3 S in water which provides the bulk of the matrix, This article first appeared in International Cement Review in November 2009 and is reprinted with kind permission of Tradeship Publrcations Ltd, United Kingdom. Email: info@CemNet.com Website: www.Ce_!nNet.com wrapped around c->ach grain of aggregate and forming a continuous. sol· i structure shaped to suit ·r . ? concrete manufacturer. C ~ ; is the more reactive of the two silicate phases and is mo· ' influential in the qain of stren, • 1 over the first 28 days after miXIng of conc(ete. Arthur Harrison, UK Jl)