Boilers are widely used in the industrial sector, especially in the refining industry. Each large refinery has more than a dozen medium-pressure boilers. The boiler is a high-temperature high-force container, which is a relatively dangerous device. Once the high temperature and high force steam leaks, it is easy to cause personal injury. The level gauge used on the boiler steam drum is a key equipment of the boiler. The liquid level in the steam drum is used to observe it. Some people call it the "eye" of the boiler. If there is a problem with the "eyes", the boiler equipment and the steam supply system is in a dangerous state, so how to choose the boiler drum level gauge is one of the most important problems for each boiler supervisor.
At present, there are three main types of liquid level gauges commonly used in boiler steam drums: quartz tube liquid level gauges, magnetic flap level gauges and high pressure glass plate level gauges. High-pressure glass plate level gauges are mainly used in high-pressure boiler steam drums, including high-pressure two-color glass plate level gauges and bull's eye two-color liquid level gauges, while high-pressure magnetic flap liquid level gauges are also used at home and abroad, but they occupy The ratio is small. Quartz tube type liquid level gauge and magnetic flap level gauge are mainly used in medium pressure boiler steam drum. High pressure glass plate type liquid level gauge has gradually withdrawn from the medium pressure boiler field due to high price, many leakage points and maintenance difficulties.
2. The selection of the level indicator at site.
Here we take the medium pressure boiler drum as the example, discussing the level indicator selection. Generally speaking, each boiler should be installed with at least two liquid level indicators in order to meet the safe operation requirements of the boiler. Among them, at least one liquid level indicator that can directly observe the liquid level should be included, and another liquid level gauge is selected by the user's own usage habits. In order to reduce the maintenance amount, the general user selects the magnetic flap liquid level indicator.
3. Quartz tube level indicator selection
The quartz tube is used to directly observe the liquid level change in the liquid level gauge. As long as the vapor-liquid connection pipe and the valve are unblocked, the water level in the steam drum can be directly seen from the liquid level gauge.
In many liquid level gauge manufacturers, there are not many quartz tube type liquid level gauges that can be used in accordance with boiler steam drums.
The boiler steam drum has strong characteristics. In addition to the high pressure and high temperature, the steam in the steam drum has a strong cavitation effect on the quartz tube of the liquid level gauge.
If the problem of cavitation is not solved, the ordinary liquid level gauge will leak after being used for 3 to 4 months on the steam drum, and even the quartz tube will burst.
Unfortunately, at present, there is no way to completely solve the cavitation of quartz tubes by high temperature and high pressure steam. Only some measures can be taken to reduce cavitation and prolong the life of the level gauge.
In summary, in the selection of boiler drum liquid level indicator, not only should we fully consider the reputation of the level gauge manufacturer and the technical level of the products, quality assurance capabilities, etc., but also consider whether the quartz tube type liquid level gauge is for the boiler drum.
We have done research on the cavitation of quartz tubes for many years. Although we have not found a way to completely solve the cavitation, we have made some beneficial improvements to the structure and materials of the level gauge used on the boiler drum, and studied B49H type boiler steam drum quartz liquid level indicator, after several years of practical application, the effect is quite obvious. The use of this steam drum quartz tube liquid level indicator is 2 to 4 times longer than that of the ordinary liquid level gauge. The level gauge mainly takes the following measures:
1. Add a device to reduce cavitation in the body of the liquid level indicator, which is very effective in reducing cavitation of the quartz tube by steam;
2. The balance tube is used to reduce the flow of steam in the meter body, and the liquid level indication is more stable;
3. The use of thick-walled special quartz tube.
Ordinary quartz tube level gauges also lack protective measures in terms of safety. After the quartz tube is cavished by steam, the wall of the tube becomes thinner and thinner, and finally it cannot withstand pressure and burst. If the quartz tube bursts, the operator just observes the liquid level at a close distance, although the self-locking steel ball closes the vapor-liquid passage to prevent further leakage of vapor and liquid, the high-temperature high-pressure steam and the cracked glass fragments can easily cause the hurt of operator's face.
4. Magnetic flap level indicator selection
The magnetic flap level indicator belongs to the indirect observation level instruments. Because of the characteristics of high temperature and high pressure resistance, all metal structure, long life, good sealing and leakage, it is widely used despite indirect observing the liquid level. The following factors should be considered in the selection:
1. To provide accurate media proportion(density): high temperature saturated water at 200℃, liquid specific gravity of 863Kg / m3, and at 250℃, liquid specific gravity of 799kg/m3, generally selected according to 780Kg/m3, manufacturers in When producing a float gauge, in addition to calculating the float according to the specific gravity of the medium supplied by the user, the buoyancy margin will be properly considered.
2. The material of the level indicator, including the float and the body, when using in the environment of high-temperature and high-pressure, if the used material cannot reach the requirement, the danger can easily occur, it’s very important!