0.3 t 0.4 t 0.5 t 1 t 2 t 4 t 6 t 10 t of fuel gas steam boiler is horizontal steam boiler shell type three return, all wet back structure. The fuel in the combustion furnace positive pressure, high-temperature furnace flue gas along the back through the combustion chamber back into the first flue tubes, the oppressive smoke box before turning 180 ° into the second bundle, after the convection heat transfer into the atmosphere. We use the center symmetrical design, the design capacity of the three return structure of a large three-pass steam boiler. The greatest feature of this boiler: All pressure parts and drum central symmetry, boiler all wet back structure, with great inner cylinder and eccentric firebox structure that is conducive to provide adequate radiation heating surface. The convection heating surface with a second backhaul and three return bundles composition. Before returning combustion chamber pipe connected to the board using furnace, combustion chamber back to the tube plate with ellipsoidal head and tube sheet. The second and third backhaul backhaul turn the smoke chamber constitutes a former smoke box, this out tobacco smoke temperature has been below 500 ℃. Therefore, before the smoke box structure fire-resistant insulation materials lighter shaped structure. After the smoke chamber flue gas outlet is disposed along the longitudinal axis of the barrel, not only shorten the length of the furnace; and also avoid chimney in a direction perpendicular to the longitudinal axis of the cylinder, boiler condensate corrosion in the boiler starts to stop. This boiler is designed primarily consider the principle of boiler maintenance and stability. Mixing water in the boiler return means import settings, return to scour smoke tube bundles, then the contact furnace, furnace to improve the return water temperature exposure. Avoid local produce subcooled boiling phenomena. Boiler water temperature in the lower part of the combustion flue gas, low in the upper flow on heat convection, it has been to achieve the best design. Steam boiler has reached the maximum of vaporization space, coupled with the high-temperature surface of the rear bulkhead plus circulating water through the combustion chamber back to make it reasonably uniform heat transfer. Back to the combustion chamber to ensure the safe operation of the tube plate. (B) waveform furnace (according to the user's choice) in this series waveform boiler furnace, both to strengthen the smoke disturbance, but also increases the radiative heat transfer area; both increased stiffness furnace, and effectively weakened expansion stress furnace; and both enhance heat transfer, and the promotion of fuel combustion in the furnace. (C) the smoke pipe and tube sheet welding using the first all-welded and then the pre-expansion, then expanded joint advanced technology, both to prevent the pipe crevice corrosion, but also enhance the weld strength. Ago (iv) symmetry living hinge, door easy to open after smoke, ease of maintenance, cleaning. This series of boiler structure is compact, easy installation and transportation. Hot commissioning before delivery, regardless of the operation rate is still in operation can be stable operation. This series boiler is equipped with imported fill pumps and burners, automatic control, a high degree of automation. Can achieve optimal combustion boiler. Second, horizontal steam boiler steam boiler protection system level protection with two pumps, operation and use. Boiler water level gauge plate supporting one to two, should always be compared with each other, indicating inconsistencies found shall be corrected immediately. Water level should be flushed each class to determine its true level. Also comes with electrode point surge drum water level, the water level can accurately capture signals to alarm or pump control. Pressure to protect a steam boiler pressure exceeds the rated pressure protection, the need for chain protection: method is shutdown, the combustion system to stop working; can also change the burner, single-stage or two-stage combustion, can regulate the amount of oil, thereby reducing. Pressure to ensure safe operation of boilers. Fuel (gas) steam boiler pressure protection and water as the use of multiple protection: ① pressure controller ships with two pressure controller, the pressure signal into an electrical signal electromechanical conversion device, it features the high-pressure, low different signal to the electrical switch, external lines for automatic control or chain protection. Common pressure controller and the electrical contacts, make vapor pressure overpressure alarm, cut off the burner when the limit is reached; pressure controller adjusts single fire or dual fire burning based on the actual operating pressure; for large burners, the pressure can be adjusted according to size the size of the amount of fuel, and always keep the pressure stable operation. ② boiler safety valve safety valve is to protect the last line of defense, in the boiler pressure exceeds the limit, according to the valve design with a set pressure, exhaust pressure relief, to ensure the normal operation of the boiler. Temperature protection Temperature protection is the safe operation of the boiler process is an important program, especially important for temperature regulation and protection of steam boilers; the same protective effect to regulate over-temperature hot water boiler. Boiler temperature protection device is used