Causes and preventive measures of tube explosion o

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Domestic small once through steam boiler tube burst causes and preventive measures

1 introduction

small once through steam boiler is composed of heating surface tubes arranged vertically. Except for the upper and lower headers, all of our hot surface tubes are riser tubes. The water supply pump supplies water from the lower header to one end of the tube. According to the preheating section and evaporation section, the required steam is generated from the other end of the tube

because the once through boiler has large heating surface and small metal consumption, it realizes the miniaturization of the boiler and the small floor area of the boiler room. In addition, the once through boiler has no drum or drum, the boiler water volume is small, and the explosion energy is small. Coupled with the automatic combustion control, the oil fired boiler has little air pollution. With the increasing requirements for environmental protection in urban areas and the increasing shortage of construction land, once through boilers are increasingly welcomed by all sectors of society

in recent years, once through boilers have developed from direct purchase of foreign products to introduction of foreign technology for domestic production. In terms of domestic production technology and manufacturing quality, there is no problem at all. However, in the actual operation process, once through boiler tube explosion, water tube deformation and expansion occur from time to time, and most of them are domestic boilers. In terms of the local scope of my contact, the shortest service life of the furnace body is only 2 months, and it is common to repair or replace the furnace body in 3-6 months. Because the once through boiler is not easy to repair, it can only be replaced generally, which brings great trouble and economic losses to users. For this reason, the reasons and preventive measures of pipe explosion are briefly discussed for the reference of peers

2 cause analysis

compared with imported original boilers, the main reasons for tube explosion are as follows:

(1) soft water treatment equipment is not as good as imported water treatment equipment. The root cause of tube explosion is the scaling in the tube. Due to the high heat load in the furnace of once through boiler, under the condition of poor heat transfer, the steel pipe will soon overheat, reduce the strength, and cause bursting under the action of internal pressure. Domestic water treatment equipment is equipped with general ion exchangers, which are completely managed and tested manually. Generally, the user unit has no full-time water quality testing personnel. Once the resin deteriorates, the treated soft water will be unqualified. The imported water treatment equipment has a high degree of automation. The water treatment equipment selected according to the local water quality and water supply can implement system program control from soft water confirmation, boiler water analysis to resin regeneration, and the equipment can complete it by itself. Human factors are reduced

(2) boiler water quality monitoring is not as good as imported boilers. Generally, imported boilers are equipped with microcomputer devices to monitor the conductivity of boiler water, and are equipped with automatic drainage devices. If the concentration of boiler water reaches the set specified concentration, it will notify the discharge, and the actuator will discharge automatically to ensure the quality of boiler water. In addition, the more advanced boiler control instrument panel is also equipped with a standard scale monitor. In case the water pipe is attached with scale due to the leakage of hard water, the sensor will judge the adhesion of scale inside the water pipe through the pipe wall temperature and give early warning. Domestic boilers generally do not have these devices

(3) dosing device in the furnace. Water treatment drugs are generally divided into antiscale agents, deoxidizers or a combination of the two. It is mainly used to adjust the pH value of boiler water, prevent the existence of scale on the pipe wall, remove dissolved oxygen in the water, and prevent the corrosion of metal materials. The dosage must be determined according to the quality of boiler water and feed water temperature. Imported boilers are generally equipped with a medicine injection box and a medicine injection pump. The medicine injection pump and the feed pump act synchronously to continuously inject medicine into the boiler at the same time as the feed water. For most domestic small boilers, the dosing device is very simple. The dosage is put into the boiler once a day. The dosing method is very unscientific and it is difficult to achieve good results

3 preventive measures

compared with imported boilers, domestic boilers have inherent deficiencies in devices. Most of the above reasons can be solved, and the key is that the operators should operate in strict accordance with the regulations

(1) each boiler room must be equipped with qualified water quality testers, and their utilization will become more and more popular to strictly control the quality of soft water and boiler water. Water samples shall be tested in strict accordance with standards. It is required that the soft water must be tested every day, and the boiler water should be tested every two hours to determine the dosage and discharge times

(2) strict regular emission system. Once through boilers have small water volume, and the circulation rate of boiler water is generally less than 2. Due to the high concentration of boiler water, its regular blowdown is different from that of other boiler types, so strict regular blowdown operation procedures must be formulated. a. Full discharge must be carried out once a day. The discharge time should be carried out when the boiler is started, not before it is stopped, so as to avoid corrosion. The specific operations are as follows: when the boiler water is at the normal water level, close the steam inlet valve; When the steam pressure rises to 0.15~0.2mpa, stop combustion; After the fan stops, turn off the operation switch; Open the blowdown valve to discharge the boiler water completely; When the discharge is completed, close the blowdown valve and open the operation switch to feed water. b. Semi discharge: determine the discharge frequency according to the boiler load and the boiler water test results. Generally, it will be discharged once and a half after four hours of operation. The operation procedure of semi discharge is the same as that of full discharge, but the discharge volume is small. When the water level is not visible on the water level gauge, it can be discharged. The water volume of once through boiler is small. A 1t/h boiler holds only about 100 kg of water, and it takes only 4-5 minutes from ignition to gas supply. Regular discharge does not affect normal use. Strict and regular discharge is an important measure to avoid and reduce the generation of scale

(3) daily maintenance inspection, in addition to the daily combustion state inspection and oil filter device inspection, the daily oil tank should be regularly drained and cleaned to ensure normal combustion. The soft water tank and water filter must also be checked and cleaned regularly, generally not less than once a month, to ensure the quality of soft water. 7. Remove samples

4 suggestions for improving the current structure

domestic small once through boilers, whether the upper and lower headers are rectangular or circular, have no inspection holes, and the burner is fixed, which brings great difficulties to the regular inspection of the boiler. Generally, the external inspection can only be carried out under the operating state, and the boiler cannot be comprehensively inspected after shutdown. It is recommended to add inspection holes on the upper and lower headers, 120 per interval (set an inspection hole. The burner device should be convenient for loading and unloading, and it should be convenient for inspectors to enter the furnace after removing the burner. Open the inspection hole of the upper and lower headers every half a year to check whether there is scale and water slag sediment in the water pipe; remove the burner and enter the furnace for inspection once a year, focusing on checking whether the water pipe with the strongest heating load is deformed at the flue gas outlet of the furnace, and deal with the problem at an early stage.

it should be reminded that when the boiler is in use After acid cleaning of the boiler, due to the special structure of the boiler, it is not easy to wash off the fallen scale and slag. Due to the change of the flow section at the closing part of the water pipe, the resistance increases, which is easy to cause the accumulation of scale or slag, resulting in blockage, and 8 The oil pump plunger is rusted and easy to check. Therefore, it is not allowed to wait until the scale is too thick. It must be prevented and treated at an early stage. Pickling must be washed repeatedly, and then discharged many times, and the water slag must be washed out by pressure difference

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