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Manual BVS 19 ATEX E 080 X
3.2.2 Pressurized enclosure system with pre-
purging
To pre-purge the housing connect a digital work-
ing 2/2 way solenoid valve (SVD.L) to the termi-
nal 5 and 6 of the PS 830. Also configure the pre-
purging period into the structure menu of the
control device. After pre-purging the valve closes
automatically and the adjustable throttle of the
SVD.L lets a small amount of purging medium
into the housing to hold pressure.
The installer can determine the pre-purging time
once by doing the attenuation test according IEC
60079-2.
As an alternative he can calculate the purging
time without the elaborate attenuation test see
below:
The purging time depends on minimum flow
(Q
), free internal volume (V) and the free vol-
min
ume of the connected pipes (Va). Final the cal-
culated time must be multiplied by 10.
The purging time t
purge
The minimum flow (Q
mum pre pressure (P
the valve (P
), internal pressure of the Ex pzc-
Valve
housing (P
) and the nozzle diameter (d). The
Int
pressure lost at the valve (P
exceed 500 mbar. The maximum internal pres-
sure of the housing is defined to be less than 20
mbar.
The minimum flow Q
min
ρ is the density of the purging medium. The den-
sity of air is ρ =1,2393 kg/m
3
gen is 1,25 kg/m
. We calculate the ρ of air for
all gases, because the difference is only 3%.
The installer can calculate the purging time of its
Edition July 2020
Copyright
is:
) depends on the mini-
min
), the pressure lost at
premin
) should not
Valve
can be calculated by:
3
, the density of nitro-
3.2.2 有预吹扫的正压系统
若要预吹扫外壳，请将数字工作2/2路电磁阀
(SVD.L)连接到PS830的端子5和6。还将预吹
扫周期配置到控制设备的结构菜单中。 预吹扫
，阀门自动关闭，SVD.L的可调节流阀允许少量
的吹扫介质进入外壳以保持压力。
安装人员可以通过根据IEC60079-2进行衰减测
试来确定一次预吹扫时间。
作为一种选择，可以计算吹扫时间，而不需要精
心的衰减测试，见下文：
吹扫时间取决于最小流量(Qmin)、自由内部体
积(V)和连接管道自由体积 (Va)。 最后，计算
时间必须乘以10。
吹扫时间tpurge是
最小流量 (Q )依据最小压力
(P premin)，阀的压力损耗 (P valve)， 防爆
简化正压腔体的内部压力(P )和喷嘴直径 (d)。
阀的压力损耗(P valve)不可以超过 500 毫巴。
腔体最大内部压力定义为小于20毫巴.
最小流量Qmin计算
ρ定义为吹扫介质。
空气密度为ρ =1,2393 kg/m3，氮气密度
1,25 kg/m3。我们计算了空气中所有气体的ρ
，因为差异只有3%。 安装人员可以自己计算其
吹扫时间
21
thuba Ltd., CH-4002 Basel
Switzerland
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