Using the Kst nomographs to estimate the venting requirements in weak dust-handling equipment

Dust explosions–Cases, causes, consequences, and control

“…Furthermore, protecting the vented enclosure is not the only important concern in dust explosion venting. The blast waves and flames which are emitted into the surroundings by the vent can be hazardous, not to speak of the risk posed to the personnel by unburned dust, smoke and soot which may suddenly spew from the vent in copious manner [144][145][146]. The maximum flame length emitted from a vent can be up to 10 times the cube root of the vented vessel volume [147].…”

Explosion

“…The HSE has carried out experiments on a 20 1 sphere and an 18.5 m 3 cylindrical vessel to investigate a number of features of venting, including extension of the Kst method (Lunn, Brookes and Nicol, 1988) and the effect of vent ducts (Lunn, Crowhurst and Hey, 1988).…”

“…The derivation of these nomographs has been described by Lunn, Brookes and Nicol (1988 The nomographs were adopted in NFPA 68: 1988, are given in the 1998 edition of NFPA 68 and are shown in Figure 17.121.The nomographs are fora high energy(10,000J) ignition source, and there is a separate nomograph for each value of the vent opening pressure Pstat. The three values of Pstat are 0.1, 0.2 and 0.5 barg and that of Fre d is 0.2--2.0 barg.…”

“…The lowest reduced pressure for which the Bartknecht nomographs apply is 0.2 barg, but, as already described, Lunn, Brookes and Nicol (1988) have extended the nomograph method down to reduced pressures of 0.05 barg, or even less.…”