Page 553 - APPLIED PROCESS DESIGN FOR CHEMICAL AND PETROCHEMICAL PLANTS, Volume 1, 3rd Edition

Applied Process Design 519

Maximum Pressure During Venting
I

P,ed• bar·ga
,...._ 0.6�
..... ,
', '\ .. 0.8� � -, ....
1.0
' ... ' 1.5� � ' ...
"' � '� 2.0� � i\ ,,,/ ... .. �
""' I'..\.
' -, -, -, <, <, ' ' ,......- .,,
,,. ......
-, -, ' ' \. ' ' ./ .,.. ,, ........ �
,, '\
,'Y / �
r-, '\. ' ' .... / :,--Dust class St-1 , .. / ,,. , ...
/ .,,
' -,l �
\. -, ..."' 'i Dust class St-2 ...-' .. x.,.. "' ...... /
:,- Dust class St-3
7
" ' ... '" l?C K' / ........... L,,i. l.,Xy'
,,
I/
l r,..k' r\ '\, .. / / 1 .... .,.i. i. i.v
i\ -, -, i. i.i. � v / "'i..."'
......
....
! r-, <, i...,,"' � i.i.v � ;;
,,
\ v ....,,.... .,.i. V/"
.,
. I ! "'\. ' r\ / v / 1 .... )" v
"'\:
/
'
�
1 ....
� I\ .... ' ......0 v "'i,.,l,
/ ....
' V/i.r
r-.. ... ' , ... /.., � /
-, -, -,
-, "" /
-,
l i\."'
100 10 0.1 10 100 1000
----Vent Area, m 1 Vessel Volume, m 3 ---•
Figure 7-65F. Venting nomograph for classes of dusts, Pstat = 0.5 bar ga. Reprinted with permission, NFPA 68-1988, Deflagration Venting,
(1988) National Fire Protection Association, Quincy, MA 02269. See note Figure 7-63A.

These require special electronics to cause responses of explosion door carefully designed and weighted can also
the systems to actually inject the suppression medium, prove useful for pipelines.
such as [54]: The use of properly designed relief panels or "free
floating" vessel covers are usually effective for dust explo-
1. halons (haiogenated hydrocarbons) See Figure 7-62 sions in silos tanks, filter housings, and the like. The
2. water, primarily for dust explosion design basis has been previously discussed.
3. powders A very careful study is required to develop a confi-
4. ammonium phosphate for some organic peroxide dence for deflagration suppression in any flammable or
dust system. The po ten ti al damage can be enormous.
Special explosion characteristics must be understood The Fauske and Associates' Reactive System Screening Tool
before selecting the type of suppression medium. (RSST) was developed as a result of the DIERS studies and
For pipelines, bursting disks have been proven practi- allows rapid evaluation of the potential for runaway reactions.
cal, especially when equipped with a sensor to pick up the It measures the rate of energy and gas release during the run-
explosion and a detonator to rupture the disks in advance away and is valuable for screening various process systems
of the pressure wave. The installation of a moveable before commercial designs are completed (see Figure 7-61).