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.
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
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.
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.
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.
Voltage : 230VAC 50/60Hz
Voltage tolerance : -15% / +10%
Power absorption 10 VA (1W for 24V DC)
Integrated valves 2×21 VA
Ambient temperature -15°C / +60°C
Enclosure IP54 (LD)
Cable gland PG9 for cable Ø6 / 8 mm
PG16 for cable Ø10 / 12 mm
ISO 4400 plug PG11 for cable Ø8 / 10 mm (optional)
Wires cross-section 2,5 mm2 max
Fuse 5 A (slow-acting)
Output signals 5 A max. resistive
2 A max. inductive
Reset signal applying mains voltage
Test period 10 s / 90 s adjustable
Filling/ Discharge time 3 s
Max. Working pressure 500 mbar (50 kPa)
Connections Rp 1/4
Gas type Non-aggressive gases included in the 1, 2 and 3 families
Integrated pressure switch Comply with EN 1854
Integrated solenoid valves Comply with a EN 161, class A
Weight LD1 450 gr LDM2 1200 gr
LD3 1600 gr LDM4 2100 gr