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1.Q: What is a vacuum hot water boiler?
A:The so-called vacuum hot water boiler, also known as vacuum phase change hot water boiler.Refers to the normal work, the pressure of the boiler internal medium is lower than atmospheric pressure, through the phase of heat transfer heating cold water boiler
2.Q:What are the structural principles of a vacuum hot water boiler?
A:The furnace body of the vacuum hot water boiler is divided into two parts, the lower part of which is similar to the three-return wet-back boiler shell steam boiler, that is, the heating surface composed of the furnace bladder and flue. The upper part is a vacuum chamber (negative pressure steam chamber), which is equipped with a tubular vapor-water heat exchanger to heat the circulating water flowing through the heat exchanger. Operating principle: when the vacuum hot water boiler is running, the thermal medium water in the furnace body absorbs the heat energy released by the fuel combustion under the vacuum negative pressure. The boiling steam turns into low-temperature steam. The low-temperature steam rises and meets the circulating water in the stainless steel heat exchanger.The water vapor itself is cooled and condensed into water droplets that fall to the surface of the thermal medium and are heated again, completing the cycle.The heat-medium water continuously carries on the “boiling – evaporating – condensing – heat-medium water” cycle in the closed body, so there is no need to add condensate water, and there is no danger of empty burning.The condensation heat transfer coefficient of soda condensation heat transfer is the highest in all the heat transfer conditions.
3.Q:What is a vacuum state?
A:A vacuum does not mean that the absolute pressure is zero, as long as it is lower than the external pressure, it can be called a vacuum.For example, when the vacuum boiler is in operation, the shell is evacuated by the vacuum device, and the pressure is maintained around -0.03mpa (gauge pressure -30KPa), that is, the absolute pressure of the boiler medium is around 0.07mpa.
4.Q:What is vacuum degree
A:Vacuum degree refers to the thinness of the gas in the vacuum state, usually expressed as “high vacuum degree” and “low vacuum degree”.High vacuum means “good” and low vacuum means “bad”.The value of vacuum degree is the value indicating that the actual pressure of the system is lower than the atmospheric pressure, that is, The vacuum degree is equal to the atmospheric pressure minus the total pressure.Vacuum degree international standard unit: Pa
5.Q:Why is the heating medium water in the vacuum hot water boiler heated in a vacuum state?
A:Under different pressures, the boiling temperature of water is different. under an atmospheric pressure (0.1Mpa), the boiling temperature of water is 100℃, while under a pressure of 0.8KPaA, the boiling temperature of water is 4℃. The vacuum hot water boiler works in the pressure range of vacuum degree 2.67 KPa to 66.6 KPa, and the corresponding saturation temperature is 15℃~85℃. Therefore, in a vacuum state, the heat medium water easily boils and vaporizes.
6.Q:What is the key technology of vacuum hot water boiler?
A:The key technology of vacuum boiler is to keep the vacuum degree stable for a long time and the leakage rate is extremely small.
7.Q:How to form the vacuum state of vacuum hot water boiler?
A:Air extraction method: special vacuum pump is used in the factory to force air extraction on the closed tank of the vacuum boiler to form a vacuum state.Some manufacturers use the boiling method: first will be a certain amount of clean water into the boiler to a certain water level, in addition to the exhaust valve to close all the boiler’s other valves, furnace heating up to the thermal medium water pressure under the saturation temperature, to be dissolved in the working medium after all the air discharged, close the exhaust valve, forming a vacuum state.
8.Q:What is the cause of vacuum damage?
A:When the vacuum hot water boiler leaves the factory, the inside of the boiler is in a vacuum state. However, during the operation of the vacuum boiler, the vacuum degree will be destroyed, for the following reasons:
First: leakage of furnace body: quality defects of welding seams, sealing parts and steel products.
Second: non-condensable gas generation (cannot be prevented): heat medium water and furnace body (steel plate) will react chemically to release a non-condensable gas (H2), which will directly affect the vacuum degree of vacuum boiler. However, the chemical reaction also forms a protective film (ferric hydroxide) on the surface of the steel plate, which hinders the chemical reaction. According to experience, the chemical reaction will stop within 2-3 years of boiler operation.
9.Q:How to prevent vacuum damage?
A: First:For the furnace body leakage, then the production process detection is very important, the vacuum boiler in the production process using the “helium mass spectrometry leakage detection” inspection, mainly has parts leakage detection (dissolution plug), semi-finished product leakage detection (furnace body welding) and the whole machine leakage detection three.High detection accuracy (helium molecular level), thorough detection, completely preventable.
Second:During the operation of the vacuum boiler, non-condensable gas must be pumped out, which is called vacuumizing.
10.Q:Why must vacuum be pumped in the operation of vacuum hot water boiler?
A:When non-condensable gas is generated in the vacuum boiler, the pressure will rise, which is called vacuum damage. The non-condensable gas produced in the vacuum boiler has a serious influence on the heat exchange efficiency. When the volume content of non-condensable gas reaches 0.2%, the thermal efficiency will be reduced by 20~30%, the outlet water temperature will not increase and the boiler output will be reduced. Therefore, non-condensable gas must be pumped out when the vacuum boiler is running.
11.Q:What is heat medium water?
A:Thermal medium water is a kind of clean water treated by special impurity removal, deoxidize and softening treatment in the manufacturing plant. It is poured once in the production process and can be used repeatedly during operation. Generally, there is no need to add water without special situation.
12.Q:What is the material of heat exchanger in vacuum hot water boiler?
A:The heat exchanger in the boiler adopts SUS304 stainless steel tubes. The pipe is not easy to form scale, has high heat transfer efficiency, does not rust, and is better than a common heat exchange pipe in terms of water quality and flow rate restriction.
13.Q:What are the main characteristics of vacuum hot water boilers?
A:(1)Do not need installation monitoring, installation can be used;(2)A multi-purpose machine, save investment;(3)No corrosion, no crack, no scar, no explosion, long life;(4). Efficient energy-saving, low operating and administrative costs;(5)High safety performance.
14.Q:What is the state’s regulatory policy on vacuum boilers?
A:The general administration of quality supervision, inspection and quarantine of the People’s Republic of China issued a document in May 2002 [guoqsiqaokehan no. 288], which stipulated the use of vacuum boiler: the vacuum phase change boiler will not explode because the pressure of its medium circulation system is lower than the atmospheric pressure.The manufacturer shall manufacture the vacuum phase change boiler following the standard, and assume the legal responsibility to inform the user (including the boiler installer) of the safe use, and ensure that the boiler system is always in a vacuum state during the use.The installation unit of vacuum phase change boiler is responsible for the installation quality meeting the installation requirements of the manufacturer.After the installation of the vacuum phase change boiler that meets the above requirements, it is not necessary to be confirmed by the safety supervision organization of the boiler and pressure vessel of the administrative department of quality and technical supervision, nor to go through the use registration procedures.
15.Q:Does the vacuum hot water boiler need annual inspection during its service life and does the user need to pay inspection fees every year?
A:There is no need to report for installation, inspection, boiler room project establishment and annual inspection (Pay annual inspection fee)
16.Q:How can a vacuum boiler supply both hot water for heating and domestic hot water?
A:The vacuum hot water boiler plus a group of heat exchange coils can provide both heating hot water and domestic hot water. However, since heating is continuous operation, it is a relatively stable load, while hot water supply is intermittent supply, which is a load with great changes. To satisfy the operation of domestic hot water supply, bypass is generally adopted on the heating circulating water pipe. Or add a water storage tank to domestic hot water.
17.Q:Is the investment of vacuum hot water boiler large?
A:Although vacuum boiler host prices higher than ordinary hot water boiler, but uses the vacuum hot water boiler can save a lot of auxiliary engine investment: plate heat exchanger, displacement heat exchanger,Primary circulation pump, soft water treatment equipment and the expansion water tank, etc., can also save the corresponding pipe installation fee 、auxiliary engine capacity increase fee, systems and control, etc., comprehensive investment or is lower than the common hot water boiler system.
18.Q:What is the rate of return on investment?
A:Because the normal service life of the vacuum hot water boiler is more than twice that of the ordinary hot water boiler (reach the semi-permanent life), the investment return cycle is long, the equipment depreciation rate is low, suitable for long-term use of customers.
19.Q:Why is the service life of vacuum hot water boiler more than twice that of traditional boiler?
A:Traditional boiler has its fatal weakness, which determines its service life is not long. In order to solve the fatal weakness affecting the service life of traditional boilers, vacuum hot water boilers are sealed in the boiler with high purity thermal coal water,which is not in contact with the air and has no oxygen corrosion forever.The boiler heats external hot water through the heat exchanger,the furnace chamber and smoke pipe only contact with the heat medium water,completely eliminate the production of limescale,can maintain long-term high efficiency operation;The circulating return water of the system is not mixed with the heat coal water in the boiler,the smoke discharge is stable,no condensate water is generated, the condensation corrosion phenomenon is completely solved, the boiler life is greatly extended.The whole service life of vacuum hot water boiler is more than 20 years.
20.Q:What kind of customer chooses vacuum boiler more appropriate?
A:Users only need hot water,such as heating, bathing, etc.For users who need a small amount of steam,such as hospitals, hotels, schools, etc.,vacuum boilers can also be used.A small amount of steam can be provided with a steam generator.