GB2316491A

GB2316491A - Wet gas meter with inclined level indicating tube

Info

Publication number: GB2316491A
Application number: GB9717132A
Authority: GB
Inventors: Joachim Ritter
Original assignee: Individual
Current assignee: Individual
Priority date: 1996-08-16
Filing date: 1997-08-14
Publication date: 1998-02-25
Anticipated expiration: 2017-08-14
Also published as: DE19632896A1; GB2316491B; DE19632896C2; GB9717132D0

Abstract

A wet gas meter has a casing 2 for receiving a blocking liquid 7, a gas inlet 4 and a gas outlet 10. A measuring drum 3 is located in the casing 2 and mounted for rotation about a horizontal axis 4. A level indicator tube 11 is in fluid communication with the interior of the casing 2, hence the level of the blocking liquid 7 in the tube 11 provides an indication of the level of the blocking liquid 7 in the casing 2. The level indicator tube 11 is inclined from the vertical at an angle of 1‹ to 89‹ so that a small change in the level of blocking liquid 7 in the casing 2 results in a larger change in the position of the surface of the blocking liquid 7 along the tube 11. The level of the blocking liquid 7 determines the volume of gas in measuring chambers 5 and therefore the volume of gas per revolution of the measuring drum 3.

Description

2316491 DRUM GAS METER The invention relates to a drum gas meter with a

casing used to contain blocking liquid, including a gas inlet and gas outlet, with a measuring drum located inside the casing, which is pivotally mounted on a horizontal axis, incorporating a device to measure the liquid level. The invention also relates to a level indicator tube for use with a drum gas meter.

Such drum gas meters are used to precisely measure the volume of gas flow. Inside the casing of the meter is a measuring drum which is rotatably mounted on a horizontal axis. The casing is filled with a so-called blocking is liquid so that the axis of rotation of the casing is below the blocking liquid level, or the blocking liquid height, and so that the drum rises ca. 4/10 above the blocking liquid.

If a gas is now introduced into the gas inlet, the rotation of the measuring drum is then effected through a positive displacement by the gas flow, and the specific design of the measuring chambers within the measuring drum. The blocking liquid is used to seal off the measuring chambers from one another, and to seal off the space within the measuring drum from the space outside the drum.

The level or the height of the blocking liquid directly determines the volume of the measuring chamber and therefore the volume per revolution of the measuring drum. The gas volume flow through is calculated on the basis of the predetermined number of. revolutions. In the factory, the calibration of the measuring drum volume and therefore that of the drum gas meter's display is done by adjusting the blocking liquid level. Given the measuring drum's 2 construction, the blocking liquid's level is the most important because it is the only parameter affecting the drum gas meter's accuracy (not taking into account manufacturing tolerances).

As the blocking liquid needs to be let out prior to transport, the correct and precise setting of the blocking liquid level by the user is of utmost importance to reestablish factory calibration. In other words, the user must refill the drum gas meter with the blocking liquid, up to a certain height or a certain level, so that at a given flow, the measuring drum's predetermined number of revolutions corresponds with a certain volume flow.

In addition, due to the blocking liquid's inevitable evaporation over time, the blocking liquid level must be checked, not only during initial installation, but also at regular intervals during its use and in particular prior to measurement.

There are currently various systems known to establish or read the blocking liquid level. It is therefore common to equip a drum gas meter with a U-tube, which is fitted to the side of the meter which communicates with the inside of the meter's casing so that the blocking liquid level is displayed in the upright limb of the U-tube. A disadvantage of this setting, with the use of a U-tube, is that a positive or negative meniscus (the upright liquid column's concave or convex form in the U-tube) is created by the blocking liquid's surface tension, which can result in a parallax error during a user reading. Besides, any change in the blocking liquid level is indicated by an exclusively vertical change in the so-called meniscus' height.

The existing device to keep the blocking liquid level in SP2017. P3 13 August 1997 a gas volume meter or a drum gas meter constant, as known from the German utility model G 72 15 966.1, exclusively performs a vertical movement or change. This existing device has a level sensor which is equipped with an electrode. The tip of this vertically arranged electrode defines the height of the liquid level so that when a set level is reached, the electrode's tip is only just touched.

Measuring systems in the form of a sight glass, in a bulge at the side of the casing, at blocking liquid level height, are also available. Such systems can also be equipped with a magnifying glass and / or a vertical needle to mark the blocking liquid's surface. Here, the is above mentioned errors, caused by the surface tension, can also occur. Additionally, also in this case, the height of the blocking liquid's surface is simply displayed by an exclusively vertical change in the blocking liquid level.

It has already been suggested to equip drum gas meters with an overflow bore, the vertical position of which would be factory set. A disadvantage of such an overflow bore is the fact that due to the surface tension, a large vertical range of blocking liquid levels would be without overflow. Additionally, in this case the display would also only be "vertical".

The aim of this invention is to provide a drum gas meter of the type set out above with which the blocking liquid level can be more accurately read and adjusted than with the existing drum gas meters.

This task is solved by a drum gas meter working in accordance with the teaching of the claims.

The core of this invention is therefore, that a SP2 017. P3 13 August 1997 conventional drum gas meter is equipped with a level indicator tube which, at leastin the blocking liquid level region is inclined away from the vertical, at an angle (setting angle a) from 1 to 89 0, in particular 10 to 85 ' and, in addition, in particular from 50 to 85 0.

In this case, "liquid level region" means the height of the blocking liquid's surface between the minimum volume flow and the maximum volume flow. In other words, the level indicator tube runs at the height of the blocking liquid during the drum gas meter's state of rest, in the form of an angle tube which is inclined in respect to the vertical. By selecting a certain setting angle for the level indicator tube, in accordance with the invention, the blocking liquid level display is expanded compared to existing indicator systems such as the U-tube. As a result, indication accuracy is practically as precise as could be required. The greater the level indicator tube's slant, the more precise the spreading becomes and therefore the display. Additionally, improved accuracy is also achieved by avoiding any parallax errors almost entirely. To reduce the capillary effect within the inclined level indicator tube, the inner diameter of this tube should be as small as possible.

Besides, it is possible for the level indicator tube to be of any shape below the blocking liquid level, and it is also feasible for it to be fixed to the casing, or to be in connection with the interior, in any way. The only crucial element is that the level indicator tube is fixed at an angle in the desired measuring area and therefore in the area of possible blocking liquid levels. It is preferably extended or run straight. In accordance with a preferred embodiment, the level indicator tube is either rigid or can be fixed to the casing and pivotable around a vertical axis, or which is integrated to the dial (mostly at the front of the drum gas meter) SP2017. P3 13 August 1997 In accordance with a preferred embodiment, the level indicator tube has at least one marking for the blocking liquid. This marking preferably designates the blocking liquid level during standard flow. The level indicator tube preferably also shows other markings, e.g. for the level indicator during minimum and maximum volume flow "Q". It is also possible to provide markings for any volume flows "Q" which are situated between the minimum and the maximum volume f low, e. 9. f or a volume f low of "10%-Qmax" and "25-,.--Qmax", etc.

The markings will normally be placed onto the level indicator tube in the factory. For standard volume flows, for example, the blocking liquid level marking is fixed so that the display error is as close to 0 % as possible. When increasing the volume flow above standard, the blocking liquid level falls during measurement due to the increase in gas pressure within the measuring drum (the volume in the measuring drum / measuring chamber therefore increases) and increases when the volume flow is reduced due to a decrease in gas pressure. An increase in the volume flow results in a negative (- x %) measuring / indicator error, and a decrease in a positive (+ y %) one.

Reversing this effect, with a slanted level indicator tube, the blocking liquid level can be set for a certain volume flow which differs from the standard volume flow, so that for this particular volume flow the measuring error is as close to 0 -06 as possible.

If one wishes to calibrate the dr-um gas meter in accordance with this invention, for a maximum volume flow, a corresponding marking needs to be applied to the level indicator tube which must obviously lie above the marking for the standard volume flow. In other words, the user is required to fill more blocking liquid into the meter if he SP2017. P3 13 August 1997 wishes to measure a larger volume flow than that of the standard one, and also wishes to achieve a measuring error as close to 0 % as possible. In an analogous manner, the opposite applies to a volume flow which is smaller than 5 that of the standard one.

Due to the expansion or the improved indicator accuracy which has occurred as a result of the level indicator tube, in accordance with the invention, it is possible to fix corresponding markings and to design these in, a readable way which has not, or has only inadequately been possible with existing systems.

In accordance with a further favoured design, the level is indicator tube's setting angle is reduced at its free end. It is therefore possible for the level indicator tube to be bent at its free end so that it has a steeper angle or turns into the vertical. Whilst measuring the volume, this level indicator tube design simultaneously acts as a manometer to measure the gas pressure because, due to the gas flow pressure, the blocking liquid level inside the measuring drum drops and increases correspondingly, as described above, outside the measuring drum, and therefore also inside the level indicator tube. The increase in the blocking liquid level inside the level indicator tube therefore occurs as a result of the communicating tube principle and is hence a scale with which to measure the gas pressure. The pressure display corresponds with the gas pressure inside the measuring drum, enabling an even more precise pressure measurement.

With the above embodiment it was assumed that the blocking liquid level inside the level indicator tube is visually read with the help of an observer. Obviously, it is also possible to read or establish the blocking liquid level with the help of any existing method in the field of level

SP2017. P3 13 August 1997 indicator technology, i.e., optoelectrically or optoelectronically. To do this, photodiodes, photosensors or similar equipment can be used. The method of detection is not relevant. Rather it is important that as a result of the level indicator tube's slanting position, in accordance with the invention, an expansion and thus an improved display accuracy or reading accuracy is achieved.

The invention is explained in detail with the help of the following drawings which illustrate a preferred embodiment in diagram form. The drawings show:

Figure 1 a diagram of a drum gas meter in accordance with the invention; and is Figure 2 an enlarged side view of the drum gas meter's level indicator tube of Figure 1.

The. greatly simplified drum gas meter as illustrated in Figure 1 has a casing 2 in which a measuring drum 3 is arranged which can rotate around a horizontal axis 4. The measuring drum 3 has several measuring chambers 5. The gas to be measured is introduced to the corresponding measuring chamber 5, which is "within reach" of the gas flowing in, via the inlet 6. The sealing of the measuring chambers 5 from one another and the sealing of the space within the measuring drum 3 is achieved by the blocking liquid 7. The horizontal axis of rotation 4 is situated below the blocking liquid level 8 inside the casing 2; the measuring drum 3 rises ca. 4/10 above the blocking liquid 7.

As a result of the gas flowing through the inlet 6 into the measuring chamber 5, open at the time, the measuring drum 3 is rotated; the gas is then released via the outlet 10. By measuring the measuring drum's number of SP2017. P3 13 AugusC 1997 revolutions the gas volume flow can be established or calculated.

A level indicator tube 11 is f ixed to the side of the 5 casing 2 which communicates with the inside of the casing 2. In other words, the blocking liquid 7 is also situated inside the level indicator tube 11.

The level indicator tube 11 is inclined in the blocking liquid 7 level indicator region 12 or arranged ina certain setting angle a to the perpendicular. The larger this angle a the better the display accuracy. In this case, the level indicator region 12 means the desired blocking liquid's 7 surface height inside the level is indicator tube 11, f or the measuring area between the minimum and the maximum volume flow. This display relates to the drum gas meter in its state of rest, i.e. there is no gas flow. Naturally, it is also possible for the level indicator tube 11 to extend beyond this area in an inclined and straight position, and even to have markings to measure the gas pressure (as described below)- As can be clearly seen f rom Figure 2 in particular, the level indicator tube 11 has several markings 13 which assist in reading the blocking liquid's surface inside the level indicator tube. The blocking liquid position 15a corresponds to the blocking liquid level 14a with a maximum volume flow. Accordingly, the blocking liquid position 15b corresponds to the blocking liquid level 14b with a standard volume. The same applies to the blocking liquid's position 15c which corresponds to the blocking liquid level 14c with a minimum volume flow.

At its free end 16, the level indicator tube 11 preferably 35 changes to a steeper area (not shown) which has markings displaying the gas pressure. During the drum gas meter's SP2017. P3 13 August 1997 1 operation (=gas flow) the blocking liquid level inside the casinS 2 is lowered which means that it is increased inside the level indicator tube 11 so that the blocking liquid 7 is pushed into the steeper area.

The drum gas meter, in accordance with the invention, and its components can be made of a suitable material such as plastic. The blocking liquid 7 is of a standard type.

SP2017. P3 13 August 1997

Claims

1. A drum gas meter with a casing for receiving a blocking liquid, with a gas inlet and a gas outlet, the meter also having a measuring drum located in the casing, which is mounted for rotation on a horizontal axis, and with a device to measure the liquid level which comprises a level indicator tube fixed to the casing and communicating with the interior of the casing which contains blocking liquid, the level indicator tube being inclined away from the perpendicular at an angle (setting angle a) of 10 to 890, at least in the blocking liquid level region.

2. A drum gas meter in accordance with claim 1 wherein the setting angle a amounts to 50 to 850.

3. A drum gas meter in accordance with Claim 1 or Claim 2 wherein the level indicator tube has at least one marking for the blocking liquid.

4. A drum gas meter in accordance with any one of the preceding claims wherein the level indicator tube in the blocking liquid level region extends substantially straight.

5. A level indicator tube for use with a drum gas meter in accordance with any one of the preceding claims, wherein the tube is constructed so that its setting angle a is reduced at its free end.

6. A drum gas meter substantially as herein described with reference to the accompanying drawings.

7. A level indicator tube substantially as herein described with reference to the accompanying drawings.

SP2017. P3 13 August 1997