JPH0329706Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to an improvement of the water side communication pipe of a differential pressure type water level detector for accurately measuring the water level in the air-water drum of a boiler.

Conventionally, in a boiler such as a water tube boiler, a glass water level gauge is installed at the water surface of the air/water drum in a connecting pipe that connects the water side and the steam side on the body side or end plate side of the air/water drum. Obsessed.

Other detectors and bottom water level and high water level detectors are installed as a set or as separate detectors for remote indication of the water surface, but in either case,
The disadvantage is that the water level in the air-water drum is not accurately measured, since these commands or operating water levels often do not match the mean water level (NWL) in the air-water drum. The height of the liquid level in the air/water drum is displayed externally.

The reason why the water level difference between the water level gauge reading and the actual NWL inside the air/water drum does not match is mainly due to the temperature difference between the air/water drum and the water side connecting pipe.
This is because there is a difference in water level. In other words, as the operating pressure of the boiler increases, the specific gravity of the water in the boiler corresponds to the temperature of the water in the boiler. Since the temperature difference also decreases, the difference in specific gravity due to the temperature difference becomes large, and the pressure difference caused by the water level difference between the boiler and the water level gauge becomes large.

Therefore, in order to reduce the water level difference mentioned above, the first step is to reduce the difference between the temperature of the water in the water level detector and the temperature of the water in the air/water drum. There are ways to reduce the temperature difference by making the pipe as short as possible, keeping it well insulated, or eliminating heat insulation on the steam side and increasing the amount of condensed water that flows into the water side.

However, in all of the above conventional methods, a hole is made in the body side or end plate side of the air-water drum to connect the connecting pipe, but as the operating pressure increases, the thickness of the air-water drum becomes 50 to 100 mm or more. However, when a cooled drain is inserted, there are drawbacks such as the need to use double pipes to prevent thermal stress, which makes processing extremely difficult.

In view of the drawbacks of the conventional water level detectors mentioned above, the inventors of the present invention and others have made extensive studies and have decided to install a differential pressure type water level detector by inserting the water side communication pipe as an inner pipe into the relatively small diameter downcomer pipe. This was the first time that we completed the differential pressure type water level detector of the present invention by confirming that it was easy to process, inexpensive, and capable of accurately indicating the boiler water level. Install the water side communication pipe of the differential pressure type water level detector of the air and water drum by inserting the inner pipe into the downpipe of the air and water drum, and connect the water outlet in the air and water drum of the inner pipe to the water flow in the air and water drum. The present invention provides a differential pressure type water level detector that is installed so as to be stable and extend to the internal height of the air/water drum, that is, approximately halfway between the bottom surface of the air/water drum and the NWL.

According to the results of studies conducted by the inventors of the present invention, when attempting to take out the water-side connecting pipe of the water level detector from the downcomer pipe, the influence of the water flow occurs because the pipe is taken out from a place where the water is flowing.

In the present invention, it is necessary to eliminate the influence of this water flow. In other words, it is necessary to prevent pressure loss and velocity head pressure drop due to water flow from occurring.

Therefore, in the present invention, the water side connecting pipe is installed at the downcomer pipe, but the outlet of the water side connecting pipe is installed at a location in the air and water drum where there is no flow of water, that is, as described above. the bottom of the air-water drum and
It is necessary to extend and install the inner pipe to approximately the middle position of the NWL. This reduces the effects of the pressure loss and velocity head as much as possible, and more preferably, a vortex generation prevention plate is attached to the top of the inner pipe to prevent air bubbles from being drawn into the downcomer pipe, the so-called carryunder. ) can be reduced to zero to improve water circulation.

Next, the present invention will be explained with reference to the drawings.

Figure 1 is a sectional view showing how a conventional water level detector 1 is attached to a steam drum. 2 is a steam side connecting pipe, 3 is a water side connecting pipe, 4 is a steam drum, and 5 is an upper boundary pipe (steam side connecting pipe). pipe), 6 is a downcomer pipe.

When the water side connecting pipe 3 in FIG. 1 becomes high pressure, it is necessary to make it into a double pipe in consideration of thermal stress, etc., and the processing and installation thereof has the drawback of being complicated and expensive.

Figure 2 is a cross-sectional view of an embodiment of the differential pressure type water level detector of the present invention showing how the air-water drum is installed, and Figure 3A.
2 is an enlarged sectional view of the air/water drum attachment part of the water side communication pipe in FIG. 2. FIG. 3B shows a cross-sectional view of the T-shaped cap 8 of FIG. 2 when its orientation is changed.

As shown in FIGS. 2 and 3 A and B, the water side communication pipe of the present invention is located at the downcomer pipe 6 below the air-water drum of the boiler.
It is installed by inserting it inside. By doing this, the downpipe has a diameter of 100 to 200 mmφ and a thickness of 10 mm.
It has the advantage that processing is significantly easier since it can be made to about 20 mm mm.

However, since there is a flow inside the downcomer pipe, in order to prevent the difference in water level indication due to the flow from appearing, the pressure loss due to the flow, (△P/γ ¹ ) and the velocity head, (γ ₁ /γ ¹・V ² / 2g), connect the inner pipe 7 to the bottom of the air/water drum where there is no water flow.
Make sure to extend it to approximately the middle position of NWL and insert it.

Here, ΔP is the pressure loss, γ ¹ is the average specific gravity of the water in the water side connecting pipe, γ is the average specific gravity of the water in the downcomer pipe, V is the flow velocity in the downcomer pipe, and g is the acceleration of gravity.

If this inner pipe is not inserted into the air-water drum and the water-side connecting pipe is left attached to the wall of the downcomer pipe, a difference in water level will result, and there is a drawback that the water level cannot be measured accurately.

In addition, in the present invention, it is better not to leave the upper part of the inner pipe 7 open upward, but to attach a T-shaped cap 8 or the like to prevent dirt from entering, and also to prevent air bubbles from being drawn into the downcomer pipe. Although it is preferable to attach a vortex generation prevention plate 9 to ensure water circulation, there is no problem even if it is not provided.

The steam side communication pipe of the present invention is the same as the conventional one, and there is no need to make it a double pipe.

[Brief explanation of the drawing]

Fig. 1 is a cross-sectional view showing how the water level detector of the present invention is attached to the air-water drum, and Fig. 2 is a cross-sectional view of an embodiment showing how the differential pressure type water level detector of the present invention is attached to the air-water drum. Figure 3A is an enlarged sectional view of the air-water drum attachment part of the water side communication pipe in Figure 2, and Figure 3B is the
FIG. 4 is a cross-sectional view when the direction of the T-shaped cap shown in the figure is changed, and FIG. 1...Water level detector, 1'...Differential pressure type water level detector,
2...Steam side communication pipe, 3...Water side communication pipe, 4...
Air/water drum, 5... Evaporation pipe, 6... Downpipe, 7...
...Inner pipe in the downcomer pipe of the present invention, 8... T-shaped cap, 9... Vortex generation prevention plate.

Claims (1)

[Scope of utility model registration request] Install the water connection pipe of the differential pressure type water level detector of the air and water drum by inserting the inner pipe into the downpipe of the air and water drum, and connect the water outlet at the top of the tip of the inner pipe to the downwelling pipe of the air and water drum. A differential pressure type water level detector for a boiler, characterized in that it is inserted and installed approximately halfway between the bottom surface and its average water level.