DE29703101U1 - Simple flow measuring device for partially filled pipes and ducts that can be installed without conversion measures based on a measuring method for fully filled pipes - Google Patents

Description

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Utility model application

Applicant: Axel Zangenberg Fischingen 19.02.1997

Vosgesstr.3
79592 Fischingen

Inventor: as applicant

Flow measuring device for partially filled pipes and channels that can be easily installed without any modifications, based on a measuring method for fully filled pipes.

The invention relates to a device for measuring the flow in partially filled pipes and channels. It is characterized in that the measured value is recorded using a measuring system for fully filled pipes (preferably MID, magnetic inductive flow meter), because this is currently the most accurate measuring method, and no modifications to the channel or pipe system are required for installation. This means that the measuring system can also be used mobile.

Current state of the art

Previous measuring methods for partially filled channels and pipes are so popular because they are very easy to clean. The measuring sensors are very easy to access.

However, the accuracy leaves much to be desired. For example, for a type-calibrated Venturi channel, the permissible traffic error according to DIN 19559 is 4G, i.e. between 12 and 20% for channel widths => 300mm and between 20 and 32% for channel widths <= 300mm.

The existing measuring methods also require a variety of installation conditions, which in many cases cannot be met for structural reasons.

However, as measurements are increasingly used to calculate taxes, these errors are no longer tolerable.

Previous measuring methods and their installation conditions for determining the flow in partially filled channels and pipes are:

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the Venturi Channel -

This dams up the incoming water by creating a constriction. The dammed water height is a measure of the flow.

This is shown in a Q/h curve in which a certain flow rate is assigned to a dam height.

Installation conditions are: A calming section at least 10x the channel width long before the venturi and an outlet section 2x the channel width long after the venturi. A gradient before the venturi, depending on the design - usually between 2 and 5 %o . There must be no backflow. There must be no lateral inflows or bends before the venturi. A smooth channel wall and no deposits are further conditions.

The weir - here the water is dammed up against a weir wall. The water flows over the weir edge. The water height above the weir edge is a measure of the flow. This is shown in a Q/h curve in which a certain flow is assigned to a dam height. There are many different weir shapes. For example, rectangular, triangular and trapezoidal weirs.

Installation conditions are:

Calm flow. Flow velocity of about 0.6m/s. No deposits.

Measuring the flow rate and the flow height - The water flow speed is measured at specific points in the channel using a sensor. Multiplying this by the flow height gives the flow rate. The speed is recorded using ultrasonic Doppler, ultrasonic transit time or magnetic inductive speed sensors. Since the speed is recorded at specific points, it must be corrected using a flow profile curve determined for the channel. This flow profile is determined individually for each channel, as it is influenced by deposits, wall roughness, gradient and channel routing. However, the determined flow profile can change again over time due to changes in the roughness and deposits on the channel walls. This is again noticeable in the measurement results.

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Solution to the previous problems nwd B^chreib'utg * ·* * The measuring method with the smallest measuring error is currently the MID (magnetic inductive flow meter) for fully filled pipes.

The device determines the average velocity across the entire cross-section of its measuring tube.

If turbulence or changes in roughness occur, these are immediately recorded and taken into account. As a result, measuring devices with maximum measurement errors of 1% and better are now available.

The MID is used as the basis for the flow measuring device described.

The system is designed in such a way that the measuring tube of the MID is always full thanks to an upwardly bent end piece (1) at the outlet. A cleaning hose can be inserted into the system through the end bend that is open at the front without having to remove it.

The adjustment to the different channel widths is carried out with the help of a hinged door (2) (sketch 4 Fig. 1-3). Seals (3) are attached to the sides and bottom, which are pressed against the walls. This means that the water can only flow through the inlet pipe (4) and thus through the MID (5).

In the pipeline version, the pipe is sealed off using an inflatable channel sealing cushion (6) with a core pipe. This means that a mobile measurement can be adapted to a wide range of pipe diameters (6b). Typical values are sealing ranges of 200-500mm or 500-800mm. The system is inserted into the channel (sketch Fig. 1+2). The part with the channel sealing cushion (6) is pushed into the pipe (sketch Fig.3) and then inflated (sketch Fig.4).

Afterwards all water flows through the MID (sketch 5 Fig.5)

The required calming sections are very short and are therefore already integrated into the measuring device.

If the channel is dammed upstream of the measuring device, all flows can be recorded continuously, since all new water flowing in now results in an increase in the damming, which flows out again through the closing bend.

The check for blockages is particularly necessary when used in raw sewage. A level measurement device (8) is installed in the inlet section of the flow measuring device. Preferably an ultrasonic level measurement device. A comparison curve (diagram) can be created using the backwater height calculation described in Appendix 1. A certain amount of water flows through the MID at a certain backwater height. This depends on _;

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depends on the type of outlet bend and the measuring pipe of the MID. This curve, the height of the backflow to the MID discharge, is compared in a measuring amplifier (9). If there are deviations from the target curve, the backflow increases to the corresponding MID flow, a blockage alarm is given.

When measuring in rectangular channels, the measurement is designed so that small amounts of water can be measured precisely. However, if - for example due to rainfall - a larger amount of water flows into the measurement, the measuring range can be extended as follows:

The MID is used to record the normal quantity. If the water quantity increases, the backflow also increases. The upper edge (10) of the flow measuring device for rectangular channels is designed as a weir. If the water now flows over the weir edge (sketch 4 Fig. 3), this overflow quantity can be recorded using a level measurement. In this case, however, a special Q/h curve is necessary, as the water that continues to flow through the MID must also be taken into account. The flow quantities are summed up up to the weir edge (10) (sketch 4 Fig. 1+2) using the MID measurement. From the weir edge, the MID quantity counting is switched off and the total quantity measurement continues using the Q/h curve. The Q/h curve is a combination (diagram 3) of the MID quantity (diagram 1) for the backflow height and a pure weir Q/h curve (diagram 2). The level measurement also serves to monitor blockages.

If there is no risk of blockage, the level measurement can be omitted and the Q/h curve can be derived from the MID discharge volume. When the water flows over the weir edge, the damming height continues to increase. This means that more water flows through the MID installed below. A limit value detection system determines when the flow through the MID corresponds to a damming at the level of the weir edge. The output signal from the MID is then sent to a linerizer, which converts the MID flow signal into a total sum flow signal - weir and MID. (Diagram 4) The more water flows over the weir edge, the more flows through the MID.

If the flow falls below the weir edge height, the system switches back to pure MID flow measurement.

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Position list "** *** **

1 - End pipe bend

2 - folding door

3 - Seals

4 - Inlet opening

5 - MID (magnetic inductive flow meter)

6 - Channel sealing cushion empty

6b - Channel sealing cushion inflated

7 - Calming section 7b - Run-off section

8 - Altitude measurement (preferably ultrasonic depth sounder.)

9 - Measuring amplifier

10 - Overflow edge - weir edge

11 - Measuring box for rectangular duct

12 - Evaluation

13 - Compressed air bottle

14 - Inlet side

15 - Drain side

Claims (7)

Utility model application ' &idigr; *! II* ^eI Zangenbefg Vogesenstr.3 79592 Fischingen Protection claims: 1. Flow measuring device for measuring in partially filled channels and pipes using a measuring method for fully filled pipes, characterized in that the device can be installed in the rectangular channel as a measuring box (11) with an integrated MID with an adjustable hinged door (2) for channel width adjustment or in the channel pipe by inserting an inflatable channel sealing cushion (6) with an MID (5) attached to the core pipe without having to carry out any reconstruction work on the structure. 2. Measuring device structure according to claim 1, characterized in that the measuring tube is sealed with a channel sealing cushion in the channel (6+6b) and thereby the water is dammed up so that it can only flow through the MID measuring tube. 3. Measuring device structure according to claim 1, characterized in that the measuring tube is accommodated in a measuring box (11) which can be adjusted to the channel width by opening it up through doors (2) with seals and thereby dams up the water so that it can only flow through the MID measuring tube (4, 5). 4. Measuring device structure according to claim 1, characterized in that the calming section (7) of 3 x measuring tube diameter before and 2x measuring tube diameter (7b) after the MID measuring tube required for the measuring method for fully filled lines (preferably MID (5)) is accommodated directly in the measuring box and therefore no further installation conditions have to be observed. 5. Clogging detection of the measuring device according to claim 1, characterized in that a clogging of the measuring tubes is determined by comparing the MID flow rates (5) with the associated accumulation heights by the upstream level measurement (8). 6. Measuring device with overflow quantity detection according to Appendix 1, characterized in that the excess water quantity flowing in the rectangular channel flows over the measuring box (11) and can be measured by a level measurement (8) as an overflow weir quantity (10) and recorded by a combined Q/h curve (diagram 3) . 7. Overflow quantity detection according to Appendix 1 and 6, characterized in that the excess water quantity flowing through the measuring box (11) is derived from the additionally increased MID flow and is output as the total water flow via a combined Q/h curve (diagram 4) .