Datasheet Content
LD, LDM
Tightness Control Device
delta-elektrogas.com EE172 -10/17
ELEKTROGAS – Technical Sheet EE172- 10/17
LD, LDM
Tightness Control Device
Contents
Description ………………………………………..….. 2
Features ……..……………………………..……..….. 2
Functioning ………………….............……….………. 3
Applications ….……………………………..……….... 6
Sizing and adjustments ……………………………... 8
Technical specifications ………………………...…. 13
Installation …………………………………………… 15
Ordering information ……..……………...…………. 16
Accessories …………………………………………. 16
Standard and approvals ……….…………......…..... 17
Description
The LD/LDM tightness control device is designed to verify the absence of inadmissible leaks in
gas trains composed by automatic shutoff valves. The check can be performed before the
ignition of the gas burner or after its stop.
This device is used in industrial firing processes and in forced draught burners, when power is
higher than 1200 kW, according to EN 746-2 and EN 676.
Features
Microcontroller technology
Easy-to-see status of the device through high visibility LEDs
Easy accessible reset button
Adjustable test time to meet the plant needs
Adjustable test instant
Available Ex-proof version with metal enclosure for installation in Zone 2 and 22 (ATEX)
Available with integrated pressure switches and/or integrated auxiliary valves
Designed and manufactured according to EN 1643
WARNING
This control must be installed in compliance with the rules in force.
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ELEKTROGAS – Technical Sheet EE172- 10/17
Functioning
Fig. 1
LD1
Basic version is composed by electronic control only (Fig.1).
This device, coupled to an external pressure switch, checks the pressure in the test volume VT
(yellow color in Fig.2), detecting potential leaks from shutoff valves.
The test is performed in two steps:
1 The upstream valve is tested discharging the test volume and monitoring the pressure
increasing (pressure switch on NO contact).
2 The downstream valve is tested filling the test volume and monitoring the pressure decreasing
(pressure switch on NC contact).
Pressure set up of the switch is usually half of inlet pressure (PT=P1/2).
The operational steps of charging and discharging test volume are done by the valves V1 e V2.
Fig. 2
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ELEKTROGAS – Technical Sheet EE172- 10/17
LD3
Version with two integrated auxiliary valves for supply/discharge operations of the test volume
VT (Fig.3).
Fig. 3
LDM2
Version with metal enclosure and integrated pressure switch (Fig.4).
Fig. 4
LDM4
Version with metal enclosure, integrated pressure switch and auxiliary valves (Fig.5).
Fig. 5
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ELEKTROGAS – Technical Sheet EE172- 10/17
Working cycle
Power-up Led Fault V2
Led Fault V1
Led OK
Led Test
Diagnosis Led Alarm
Led Power
STEP DESCRIPTION
tA 1 2 3 4 5 6
Power-up
NO
OK Power supplied to terminal 3.
Alarm
Device runs a self-check (lasting tA)
YES Alarm
A problem has occurred.
Ready Signal F (fault) is sent to the control unit.
The working cycle stops.
Led2 is blinking according to the type of
problem (see alarm table).
Discharge Start Ready
No faults occurred.
tO = 3 s Device is ready to receive the command
S (start).
Test V1
Discharge
Start signal S is received.
tP Device opens V2 to discharge test
volume.
NO
PT < P1/2 Leak from V1 (time tO = 3 s).
Test V1
YES Device shuts V2 off and test for V1
begins (lasting tP).
V1 OK
Leak from V1
An unacceptable leak from V1 is
detected.
Filling Signal F (fault) is sent to the control unit.
Cycle stops.
to = 3 s V1 OK
The valve V1 is tight.
Test V2
Filling
Device opens V1 to fill the test volume
tP (time tO = 3 s).
PT > P1/2 NO
Leak from V2 Test V2
Device shuts V2 off and test for V2
begins (lasting tP).
YES
Leak from V2
V2 OK An unacceptable leak from V2 is
detected.
Signal F (fault) is sent to the control unit.
Cycle stops.
V2 OK
The valve V2 is tight.
OK signal is sent to the control unit.
LED switched on Tab. 1
LED blinking
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ELEKTROGAS – Technical Sheet EE172- 10/17
Applications
In addition to the basic diagram shown in Fig. 2-5, other connections are possible.
System with 2 safety valves and 2 pressure switches (Fig.6).
In the case of a large test volume, in order to reduce the testing time, two pressure switches can
be used and set with different pressure values PL and PH.
When the tightness test is finished with positive result, the OK enable signal is sent to the
burner control, which can now open the V1 and V2 valves.
Fig.6
System with 2 safety valves and a auxiliary valve for the discharge (Fig.7).
f the second valve V2 is a slow opening type, it is necessary to install an auxiliary valve with fast
opening VD for the discharge into the combustion chamber (or in the atmosphere).
The device checks the tightness of the valves V1 and V2 and the auxiliary valve VD. When the
tightness test is finished with positive result, the OK enable signal is sent to the burner control,
which can now open the valve V2.
Fig.7
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ELEKTROGAS – Technical Sheet EE172- 10/17
Multiple burner system with 2 safety valves installed in series and auxiliary valves for the
filling and discharge (Fig.8).
The device checks the tightness of the main valve V1, the auxiliary valves VF and VD and the
safety valves of each burner.
When the tightness test is finished with a positive result, the OK enable signal opens the main
valve V1 and it is sent to the burner control, to enable the opening of the valves of each burner.
Fig.8
Multiple burner system with 3 safety valves installed in series (Fig.9)
If the main valves V1 and V2 are slow opening is necessary to install the VF and VD auxiliary
valves for filling and discharging of the test volume VT.
The device checks the tightness of the main valves V1 and V2 and the auxiliary valves VF and
VD. The valve V2 can only be tested if the downstream pressure is approximately equal to the
atmospheric pressure and the volume of this chamber is at least equal to 5xVT.
To this purpose the VK valve is opened by the Start-up signal to relieve the pressure at the
value which is adjusted with the pressure switch P2 (it must be calibrated so as to detect
minimum increases of pressure). When the tightness test is finished with positive result, the OK
signal disables the VK valve (via the K normally closed contact), opens the valves V1 and V2
and, at the same time, enables the control units of each burner located downstream.
Fig.9
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ELEKTROGAS – Technical Sheet EE172- 10/17
Sizing and adjustments
Leakage rate
According the EN 1673…
