ML442 | v5k
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Expo Technologies UK
T: +44 (0) 20 8398 8011
E: [email protected]
Expo Technologies US
T: +1 (440) 247 5314
E:[email protected]
Expo Technologies China
T: +86 532 8906 9858
E: [email protected]
Purge Flow Rate (Orifice Size Selection) – Only for CF Systems
The purge flow rate is selected by placing the appropriate orifice plate in the SAU. The purge
flow rates given in Table 2 are based on standard setting of the flow sensor of 2.5mbar, 1” WC,
250Pa. For LC systems the purge flow rate is set by the selection of the RLV and is not user
adjustable.
Orifice Plate
Number
Continuous Flow Rate with
2.5 mbarg, 1” WC, 250 Pa
flow sensor set point
N litre/minute
SCFM
A
10
0.4
B
25
0.9
C
40
1.4
D
65
2.3
E
90
3.2
F
135
4.8
G
180
6.4
NO ORIFICE
225
8.0
Table 2 Purge Flow Rates
Action on Loss of Pressurization
The action on loss of pressurization is the responsibility of the user.
The action on loss of pressurization can be set to ALARMS ONLY (AO), or ALARM AND
AUTOMATIC DISCONNECT OF POWER (A&T).
a) Leakage Compensation
The action on loss of pressurization is set by moving the
jumper tube (see Figure 10 Action on Loss of
Pressurization Jumper Tube). The standard setting is
Alarm and Trip where the link is from C to A&T, with a
plug in AO. Changing to Alarm Only (AO) is user
adjustable by moving the link from C to AO, and plugging
A&T.
Figure 10 Action on loss of pressurization jumper tube
b) Continuous Flow
The standard CF system is built set to Alarm and Trip. Alarm Only can be installed when order
specified or supplied as a retrofit kit later. See options.
The selection for action on loss of pressurization depends on the area of operation and the
following guidelines should be followed.
The user must make use of this alarm facility in accordance with the local code of practice for
"action on pressure or flow failure". Most codes include the following recommendations:
Zone 1 Installations:
Alarm and automatic disconnect of power.
Exception: If the equipment inside the PE is suitable for use in Zone 2, the power trip may be
performed manually, (no automatic power trip), if the pressure or flow failure persists for an
unacceptable time
.
