Bentone BG 400-2 Two-Stage Gas Burner 61-325 kW

Overview

The Bentone BG 400-2 is the two-stage version of the Bentone BG 400 intermediate gas burner. Where the single-stage burner fires at one fixed rate, the Bentone BG 400-2 can run at a low load and a high load, switching between them on demand from the boiler or process controller. Its installation manual rates it at 61 to 325 kW on natural gas G20, 61 to 310 kW on G25 and up to 350 kW on propane G31. Bentone builds the burner in Ljungby, Sweden, and fits it with a Siemens LME22 burner control, a DUNGS MultiBloc MB-ZRDLE gas valve and an electric damper motor for the air side.

Seven Star LLC supplies the Bentone BG 400-2 and its spare parts to boiler operators, HVAC contractors and process heat users in the Sultanate of Oman and across the GCC, with engineering support in Muscat. Two-stage firing is a common choice where load varies through the day, for example on hotel and hospital boilers that see a heavy morning demand and a much lighter night load.

Operating Principle

On a start, the LME22 control checks the air pressure switch, starts the fan and runs a 20 second prepurge, followed by a 3 second pre-ignition and ignition of the gas at the start load. Flame is supervised by an ionisation electrode; the safety time is under 3 seconds and the reaction time on flame failure is below 1 second. Once the flame is established, the Bentone BG 400-2 runs in stage 1 and moves to stage 2 when the controller asks for more heat. The second solenoid valve on the MultiBloc and the damper motor work together so that gas and combustion air increase in step.

The damper motor turns the air damper between three preset positions: fully closed, low load and high load. In the manual these are controlled by coloured cam discs, with the red cam for high load, the orange cam for low load and the blue cam as the closed limit, while the black cam switches the high-load solenoid valve. On the gas side, the MB-ZRDLE 405 to 412 has a maximum inlet pressure of 360 mbar and an S50 regulator range of 4 to 50 mbar, with slow-opening valves and separate adjustment of start load, stage 1 and stage 2. Bentone recommends an excess air level of about 4 plus or minus 1 percent O2 in the flue gas.

Engineering Design of the Bentone BG 400-2

Mechanically the Bentone BG 400-2 shares its main dimensions with the single-stage BG 400. The manual lists flame tube lengths of 172 mm and 272 mm, both with a 140 mm flame tube diameter, a boiler hole circle of 175 to 240 mm and a recommended boiler opening of 145 mm, or 115 mm when the flame tube is fitted from inside. The burner is supplied at 230 V single-phase, 50 Hz, with a main current of 3.1 A, IP20 protection and a maximum fuse of 6.3 A. The NOx class is 2 on G20 and 3 on G25, G30 and G31, and the sound power level is 85 dBA.

The MB-ZRDLE valve is adjusted by hand on the body: the regulator outlet pressure with a screwdriver, covering the full range in about 60 turns of the spring, the start gas flow with a knob under a protective cover, stage 1 with a hydraulic device locked by a screw, and stage 2 with a second hydraulic device. Pressure taps with G 1/8 plugs and a test nipple for inlet pressure make commissioning straightforward. Model codes describe the combination, for example Bentone BG 400-2 L172 LME22 407 for the short flame tube with an MB-ZRDLE 407 valve.

Key Features

The Bentone BG 400-2 brings these documented features to boilers with variable demand:

• Two-stage operation gives a low and a high firing rate, which reduces on-off cycling compared with a single-stage burner.
• The firing range is 61 to 325 kW on G20 and 61 to 340 or 350 kW on butane and propane.
• A Siemens LME22 control provides the start sequence, ionisation flame supervision and lockout with LED fault codes.
• The DUNGS MB-ZRDLE gas valve allows separate setting of start load, stage 1 and stage 2 flow.
• A damper motor with cam discs sets closed, low-load and high-load air positions and can be released for servicing.
• Natural gas groups H, E, L and LL, LPG, butane and propane are all listed as permitted fuels.
• Bentone states EN 676 approval, with versions according to EN 746-2 Annex J/K available for ovens and steam boilers.
• Service once a year or every 3,000 hours is recommended, and the damper motor has a listed life of 500,000 starts.

Industrial Applications

The Bentone BG 400-2 suits hot water and steam boilers, air heaters and ovens where the heat demand changes during the day. Typical installations are central heating and domestic hot water plants in hotels, hospitals and residential compounds, and process heat in laundries, bakeries and food factories. Because low load can be set well below full load, the burner spends less time starting and stopping, which helps boiler efficiency and reduces wear on ignition and safety components.

In Oman, Seven Star LLC supports Bentone BG 400-2 users in Muscat, Sohar and Salalah with complete burners and with gas train and flame supervision parts such as the Dungs MB-DLE 405-412 B01 GasMultiBloc Combined Regulator and Safety Valves, the Dungs GW A6 Compact Pressure Switch for Gas and Air and the Lamtec FFS08 Flame Sensor for Burner Flame Monitoring. For single-stage applications, see our Bentone BG 400 page.

Technical Specifications

The data below for the Bentone BG 400-2 come from the manufacturer installation and maintenance manual attached to this page and Bentone’s model list.

How to Order

To request the Bentone BG 400-2 or its parts, send Seven Star LLC the full model designation and article number from the data plate, plus the gas type and boiler data. Our Muscat team checks the configuration against the attached manual and supplies to sites across Oman and the GCC.