WO1990008724A1

WO1990008724A1 - Adjustable discharge valve for container/storage tanks/silos for pulverulent materials

Info

Publication number: WO1990008724A1
Application number: PCT/NO1990/000017
Authority: WO
Inventors: T. Marthon Michaelsen
Original assignee: MARITIME GMC AS
Current assignee: MARITIME GMC AS
Priority date: 1989-01-26
Filing date: 1990-01-26
Publication date: 1990-08-09
Anticipated expiration: 1991-07-26
Also published as: NO890321D0; AU5025290A

Abstract

Herein is disclosed an automatic, continuously adjustable discharge valve, designed with an eye to application in connection with containers/storage tanks/silos for pulverulent materials, particularly chemicals. The container/storage tank/silo (1) has a central bottom outlet (2) which is arranged to close/open with the aid of an upwardly pointing, essentially wedge-shaped closing and sealing plug (3, 4), such that the powder material when the plug (3, 4) is lifted will be able to run out through the outlet (2) through the annular slot (28) formed between the outer circumferential edge of the plug (3, 4) and adjacent inner wall of the container/storage tank/silo (1) at the outlet (2). The discharge powder quantity per unit of time can be varied/adjusted by changing the elevation of the plug (3, 4). The discharge valve comprises a vertical double-acting pressure-fluid-operated piston/cylinder assembly (6, 6') which, in service position, is coaxial with the said essentially wedge-shaped closing and sealing plug (3, 4) and whose upper end either carries an actuator head (8) for operation of the plug (3, 4) between closed and maximally open position, or is connected to the plug (3, 4) for the identical purpose. The piston/cylinder assembly (6, 6') is provided with an electronic position sensor (7) which, together with the piston/cylinder assembly's (6, 6') two hoses (18) is interfaced with a PLS [Programmable Logic System].

Description

ADJUSTABLE DISCHARGE VALVE FOR CONTAINERS/STORAGE TANKS/SILOS FOR PULVERULENT MATERIALS

The present invention relates to an adjustable discharge valve for containers/storage tanks/silos for pulverulent (powdery) materials, particularly chemicals, where the container/storage tank/silo has an outlet in the form of a bottom opening which is so arranged as to be openable/closeable by the aid of a cone shaped closing and sealing plug, such that the pulverulent material, when the closing and sealing plug is open, will run out of the outlet through the annular space formed between the cone shaped closing and sealing plug's outer circumference and the outlet's adjacent inner wall. By raising or lowering the cone shaped closing and sealing plug relative to the outlet, the said annular space and therefore the discharged powder quantity per time unit can be varied/adjusted.

An outlet valve of this type is known from British patent claim no. 2,187,731 in which the cone shaped closing and sealing plug is arranged as an inflateable bellows with vertical axis. The plug is lifted by the pumping of pressure fluid into the bellows, and bleeding off of the bellows pressure causes lowering of the plug. In this known discharge valve there are also effected measures by which to vibrate the closing and sealing plug, so as to facilitate the discharge, particularly in the case of packed mass.

The discharge valve disclosed in the British patent aforementioned is based on a pulse system and is therefore unable to ensure continual dosing until reaching dosing quantities of over 2 tonnes an hour. The discharge valve is of no use for dosing where the same valve is charged with the task of varying the dose quantity from 10 kg/hour to 1500 kg/hour. For sea(water)-based dosing of chemicals in the oil industry, however, just such dosing variation is an absolute requirement. With the known discharge valve, poor feedback is obtained to the PLS [programmable logic system] about the quantity weighed out, as the valve is continually moving from closed to open position. The disclosed discharge valve has a high level of noise since three metallic parts are always impacting on each other.

The objective in accordance with the present invention has been to remedy these disadvantages.

This objective is achieved by means of the features stated in the characteristic portion of the ensuing patent claim 1.

The discharge valve according to the present invention has a hopper shaped valve casing which, for powder containers, is designed to be fixed to a frame in the discharge station and, for stationary tanks/silos, directly to the tank/silo's outlet. In the valve casing is arranged a pressure fluid cylinder with vertical axis, whose (upper) conical piston rod end serves as actuation organ for the said cone shaped closing and sealing plug, is designed complementarily to the plug, so as to be capable of lifting/lowering the closing and sealing plug under controlled, evenly distributed application of power. The pressure cylinder is equipped with a position sensor. The plug's actuator organ is connected to a variable vibrator so that the powder can be set in motion via the plug. This makes it possible through essentially known means to discharge the powder, even when tightly packed.

The container/storage tank/silo or installation cradle for the same is equipped with weigh cells and/or a quantity monitor which provides an accurate feedback of the quantity discharged per unit of time to the PLS. Since the vibrator, position sensor, cylinder valves and weigh cells/quantity monitors are interfaced with the PLS, one will at all times have full control of the powder discharge process. This means that if one, via the PLS, selects a discharge quantity per time unit of, for example, 400 kg/hour, the piston in the pressure cylinder will be displaced to a preset level corresponding to that discharge rate. When, accordingly, sufficient powder quantity has been discharged for the weigh cells/quantity monitor to record the weight loss/quantity, the PLS will "compute" to what extent the discharged quantity is correct relative to the chosen dose. In the event of disparity, the PLS will signal causing the discharge valve to reduce/increase the discharge slot. This implies that the further into the discharge period one progresses, the closer will one be to the chosen dose.

The discharge valve as disclosed herein provides a continuously adjustable annular discharge slot, enabling very precise dosing to be achieved. The movements that the valve's moving parts must perform take place under controlled conditions with very little noise. It is possible to dose continually down to very small powder quantities per unit of time. The discharge valve provides precise feedback to the PLS on the position at which it is placed, enabling small adjustments to be easily implemented. It also reacts very precisely to changes in the discharge slot. Discharging is accomplished calmly and controlledly, which enables weight assays to be made without disturbance.

One embodiment of a discharge valve as disclosed by .the invention is elaborated in more detail hereinafter with reference to the drawings in which: Fig. 1-3 are principle sketches showing how the discharge valve of the invention functions with powder containers;

Fig. 4 and 5 are corresponding principle sketches showing the discharge valve's installation and function with stationary storage tanks;

Fig. 6 shows an embodiment for a suitable closing and sealing plug which facilitates the fluidisation of the tank's contents by supplying air;

Fig. 7 and 8 show detailed axial section elevations of the discharge valve, respectively in open and closed position.

Reference is made first to drawings Fig. 1-3 in which Fig. 1 shows the situation when the dosing station is empty, namely before the powder container is located over the discharge valve; in Fig. 2 the container is positioned above the discharge valve, which is in the closed position; and in Fig. 3 which corresponds to Fig. 2 the valve is shown in open position.

On the drawings the reference figure 1 denotes a container/storage tank/silo for pulverulent material, particularly chemicals.

The powder container of Fig. 1-3 has a central bottom outlet 2. The outlet 2 is arranged to be closed and opened by aid of a cone shaped closing and sealing plug 3 which at its largest (lower) circumference is provided with a ring-shaped sealing ring 4, which in the plug's closed position forms a seal against the adjacent inner wall of the cross-over section between container 1 and outlet 2. When the closing and sealing plug 3 is lifted, an annular slot opens up between the plug and adjacent container inner wall at the cross-over section to outlet 2. This annular slot's area can be varied depending on the plug's 3 elevation, whereby it is possible to change/adjust the discharged powder quantity per unit of time, in other words the dose rate. This represents the prior art. The discharge valve embraces a hopper shaped valve casing 5 which at container 1 is fixed to a cradle in the discharge station, Fig. 1-3, and at stationary storage tanks/silos 1' to the outlet of the tank/silo 2', Fig. 4-6.

The valve casing 5 encloses the double-acting pressure fluid cylinder 6 with vertical axis. The pressure cylinder 6 is equipped with an electronic positioning sensor 7.

The pressure cylinder's 6 upper piston rod end supports an upwardly pointing conical/wedge-shaped actuator organ or actuator head 8 for the closing and sealing plug 3. The head 8 is shaped complementarity to plug 3 and therefore has approximately the same cone shape. Reference figure 10 denotes a circumscribing seal which according to Fig. 1-3 is intended to seal between the container outlet 2 and valve casing 5, while 11 indicates the vibrators and 12 a shock absorber for the valve casing 5. Reference figure 13 denotes an attachment for the double-acting pressure cylinder 6.

Reference figure 14 indicates weigh cells and 15 a PLS (control unit).

As shown in Fig. 1-3 the PLS is interfaced with the weigh cells 14, vibrators 9,11, and the pressure cylinder's 6 valves and position sensor 7. The same is true of Fig. 4 and 5.

Since a PLS is interfaced with the weigh cells 14 which assay the container 1 with contents, the annular discharge slot 16 between plug 3 and container outlet 2 will be adjusted if the discharged powder quantity per time unit does not match the chosen dosing.

In Fig. 1 the dosing station is empty, meaning that the container 1 is not yet in position above the discharge valve. Seal 4 seals between the plug 3 and container outlet 2, while seal 10 seals against the actuator head 8, thereby preventing undesirable substances from gaining access to the closed system within the valve casing 5.

In Fig. 2 the powder container 1 is located above the discharge valve. At this location of the container, the container outlet 2 reaches down inside the valve casing at seal 10, where a seal is established between the valve and the container. The PLS 15 is now able to weigh the container with powder.

In Fig. 3 the PLS when selecting the discharge quantity per unit of time will control the discharge valve's actuator head 8 to take up an elevation bearing a relation to the chosen dose quantity, thereby making the annular discharge slot small when a small dose quantity is chosen, and larger when a larger quantity is chosen.

When the closure and sealing plug 3 is lifted by the discharge valve's actuator head 8 free of its seal's contact with the cross-over section between the container 1 and outlet 2, the actuator head's 8 vibrator 9 is started up, thereby ensuring a uniform discharge stream. After a certain quantity of powder has been discharged, the PLS via the weigh cells 14 will update the discharge rate and, as appropriate, adjust it so as to discharge out the correct quantity of powder by the timeout.

If, after a given period of time, no change in weight is detected, the pressure cylinder's 6 piston will quickly lift up and then return. If still no weight change is detected, the vibrators 14 will be started up, causing the entire container 1 to vibrate. If the weight change remains zero, the PLS will signal an empty container.

The sequence is essentially the same in the arrangement in Fig. 4 and 5. Here, however, the closing and sealing plug is carried directly by the upper piston rod end, which thus constitutes the attachment for the plug 3. An arrangement of this type is only possible with a stationary storage tank/silo.

In the embodiment in Fig. 6, which is intended for discharge valves for stationary storage tanks, the closing and sealing plug 3 is materialised as a double-wall with circumferential opening (or openings) 16 for the supply of air from the valve casing 5, by which means to fluidize the contents of the storage tank.

Reference is now made to the detail sketches in Fig. 7 and 8 showing a discharge valve for powder containers, in respectively closed and open position, which employs the same reference figures as previously.

In Fig. 7 and 8 the double-acting pressure fluid cylinder 6 is fastened in the valve casing 5 by means of three brackets 17.

When the container 1 is set down above the discharge valve, the container outlet 2 reaches down into the valve casing at the casing's seal 10, which ensures a dust-tight connection between adjacent parts.

When the discharge valve is activated for discharging of powder via the PLS 15 and solenoid valves (not shown) which are connected to the pressure cylinder's 6 hoses 18, the actuator head 8 is lifted until it reaches the elevation corresponding to the selected discharge rate.

The actuator head 8 is installed on a fixing plate 19 at the upper end of the piston rod 6' and is vibrationally insulated from the piston rod 6' by means of a shock absorber 20. The actuator head 8, its air vibrator, for example in the shape of a ball vibrator 9, its shock absorber 20 and the piston rod 6' are isolated from the surroundings by means of a dust bellows 21. The pneumatic ball vibrator 9 is so arranged that it is activated when the actuator head 8 lifts, allowing vibrations to propagate into the container contents. This vibrator 9 is controlled suitably by a servo valve (not shown) whereby variation of the vibration frequency can be achieved.

Reference figure 22 denotes an upper fastening plate for the pressure cylinder 6 and 23 a lower fastening plate for the same.

Reference 24 denotes a ventilation pipe for the dust bellows 21, where 25 indicates the hoses of the vibrator 9, while 26 indicates the electronic signal for the position sensor 7 which is provided for the pressure cylinder 6. Reference 27 denotes an elastomeric shock-absorbant substance fastened to the actuator head 8.

Should the PLS 15, Fig. 1-5, record a discrepancy between desired and detected discharge rate, the situation is adjusted by changing the lift elevation of the actuator head 8, whereby the annular discharge slot 28 is widened/narrowed between the plug's 3 outer circumference and the adjacent inner wall at the container's 1 cross-over section to the outlet 2.

As shown in Fig. 1-3 the PLS 15 is interfaced with the weigh cells 14, so that container 1 with its contents and discharge valve is weighed, allowing the dose quantity to be calculated from the "weight loss".

If no weight change is recorded over a period of time, the PLS will signal that the full air quantity shall be applied to the vibrator 9. If still no weight change is detected, the air vibrator 11 fastened to the cradle of the outlet valve will activate, causing the entire container to vibrate.

Considering the aforementioned vibration options, possibly in combination with the fluidisation of the pulverulent mass discussed in connection with Fig. 6, bridging of the pulverulent material as well as compression is avoided. By applying, continuously adjustable vibration, vibration characteristics can be matched to the properties of the powder to be discharged.

The discharge valve ensures precision feedback to the PLS 15 on the elevation that the actuator head/closing plug has attained.

Using the discharge valve of the invention there is no need for manual operations after the container has been positioned above the valve.

Claims

1. Automatic continuous adjustable discharge valve for containers/storage tanks/silos (1; 1') for pulverulent materials, particularly chemicals, in which the container/storage tank/silo (1; 1') has a central bottom outlet (2; 2') which is so arranged as to be capable of closing/opening with the aid of an upwardly pointing, essentially wedge-shaped closing and sealing plug (3,4) such that the pulverulent material when the plug (3,4) is lifted will be able to run out of the outlet (2; 2') through the annular slot (28) which is formed between the plug's (3,4) outer circumference edge and the adjacent inner wall of the outlet (2;2'), and where the discharged powder quantity per unit of time can be varied/adjusted by changing the elevation of the plug (3,4), characterised in that the discharge valve comprises a -vertical double-acting pressure-fluid-operated piston/cylinder assembly (6,6') which in service position is coaxial with the said essentially wedge-shaped closing and sealing plug, and whose upper end either carries an actuator head (8) for operation of the plug (3,4) between the closed and maximum open position, or is connected to the plug (3,4) for the same purpose, and which piston/cylinder assembly (6,6') is provided with an electronic position sensor (7) which, together with the piston/cylinder assembly's (6,6') two hoses (18) is interfaced with a PLS (15).

2. Discharge valve conforming to Claim 1, characterised in that the piston/cylinder assembly's (6,6') actuator head (8) is shaped generally complementarity to the essentially wedge-shaped closing and sealing plug (3,4) and therefore possesses essentially the same conical form.

3. Discharge valve conforming to Claim 1 or 2, characterised in that the actuator head (8) is provided with a vibrator (9), preferably a pneumatic ball vibrator, which is interfaced with the PLS (15).

4. Discharge valve conforming to Claim 1, 2 or 3, characterised in that an installation cradle for the discharge valve is provided with one or several vibrators (11) which are interfaced with the PLS (15).

5. Discharge valve conforming to any of the aforementioned claims, characterised in that there are provided weigh cells (14) and/or a quantity monitor interfaced with the PLS (15).

6. Discharge valve conforming to any of the aforementioned claims, characterised in that the closing and sealing plug (3') and/or actuator head (8) are made as a double wall and have one or several openings along the largest circumferential edge, and are supplied with air supply, preferably centrally from the valve casing (5).

7. Discharge valve conforming to any of the aforementioned claims, characterised in that there between the actuator head's (8) lower limiting edge and an upper cylinder fastening (22) is confined a bellows (21) which ensures dust-free enclosure of inter alia the actuator head's (8) vibrator (9) and piston rod (6').

8. Discharge valve conforming to any of the aforementioned claims, characterised in that there between the piston/cylinder assembly (6,6') and actuator head (8) is connected a shock absorber (20).

9. Discharge valve conforming to any of the aforementioned claims, characterised in that there is fastened to the actuator head (8) a shock absorber (27).