WO2004018335A1

WO2004018335A1 - Powder transfer system

Info

Publication number: WO2004018335A1
Application number: PCT/AU2003/001062
Authority: WO
Inventors: John Alexander Ryan; Allan Egan; Chris Moore; Mark Parsons
Original assignee: Airservices Australia
Priority date: 2002-08-21
Filing date: 2003-08-20
Publication date: 2004-03-04

Abstract

A dry powder transfer system comprising a hopper (10) adapted to store a quantity of dry powder, the hopper having an inlet (22) and an outlet (20) and means (24, 26) for agitating powder within the hopper, and a filter means (18) adapted to allow flow of air out of the hopper whilst retaining powder material within the hopper; pumping means (34) for pumping powder to and from the hopper; conduits (42, 44, 48, 50) for connecting the hopper to a vessel to which or from which powder is to be conveyed; pumping means adapted to be used to convey powder between said hopper and a said vessel along said conduits. Preferably the hopper has an internal separator (70) for separating dry powder from gas used to convey the powder to the hopper.

Description

Powder transfer system

Field of the invention

This invention relates to a powder transfer system which is able to transfer powder materials such as dry chemical powders from one vessel to another vessel. The invention will be particularly described in relation to a transfer of dry chemical powders used in fire fighting equipment. It is to be understood that the invention will have far wider application.

Background of the invention

Powder material, once it becomes compacted, is difficult to shift from one vessel to another. Transfer of such materials also causes dispersion of the powder which is unhealthy and messy.

In fire fighting vehicles the pressure vessel which contains the dry chemical powder used in fire fighting needs to be inspected at least once every twelve months to satisfy government safety regulations. The vessel needs to be empty in order for the inspection to be carried out. Emptying such vessels has typically been done in one of two ways. Either the chemical powder is discharged through the outlet nozzle of the pressure vessel which means that the chemical powder is wasted at some considerable cost. Alternatively the powder is emptied from the vessel either by scooping or other similar technique. This emptying procedure is not only time consuming and inefficient but tends to result in powder dust being spread around which is undesirable.

Summary of the invention

According to the invention there is provided a dry powder transfer system comprising: a hopper adapted to store a quantity of dry powder, the hopper having an inlet and an outlet and means for agitating powder within the hopper, and a filter means adapted to allow flow of air out of the hopper whilst retaining powder material within the hopper; pumping means for pumping powder to and from the hopper; conduits for connecting the hopper to a vessel to which or from which powder is to be conveyed; said pumping means adapted to be used to convey powder between said hopper and a said vessel along said conduits.

The hopper may have a downwardly convergent conical base and the outlet from the hopper may be located at the apex of said conical base. The agitation means may comprise a supply of compressed gas which is supplied to said hopper via a series of apertures located in said conical base. Said supply of compressed gas may comprise a supply of nitrogen gas.

Said filter means may comprise a filter element located at or towards the top of said hopper. Said pumping means may comprise a diaphragm pump which is powered by comprised air supplied from a source of compressed air. Preferably said source is able to provide a continuous supply of compressed air at a nominal operating pressure of 700 kPa (100 psi), and no lower than 400 kPa (58 psi). Optionally the hopper is mounted on a wheeled chassis adapted to be wheeled to a location adjacent a vessel to be filled or emptied. The source of compressed air may also comprise a transportable compressor adapted to be moved with the hopper. Where the source of compressed air is a portable compressor, it is desirable that the compressor has a capacity of at least 850 1pm (30 cfrn) to provide sufficient pumping capacity.

These and further features of the invention will be made apparent from the description of an embodiment thereof given below by way of example. In the description reference is made to the accompanying drawings, but the specific features shown in the drawings should not be construed as limiting on the invention.

Brief description of the drawings

Figure 1 shows a diagrammatic illustration of a powder transfer system according to the invention in a mode of operation in which it empties powder from a pressure vessel;

Figure 2 shows a similar view to that of figure 1 with the apparatus in a second mode of operation in which the pressure vessel is refilled with powder from the hopper;

Figure 3 shows the system in a third mode of operation in which fresh powder is filled into the pressure vessel via the system; Figure 4 shows a side view of a hopper according to the invention; and Figure 5 shows a side view of a further embodiment of a hopper according to the invention.

Detailed description of the embodiments

The apparatus of the invention is suitable for transferring dry chemical powder to and from a vessel such as the pressure vessel of a fire truck. As mentioned above, fire trucks carry a load of dry chemical powder which is used for extinguishing certain types of fires. It is important that the powder in the pressure vessel is kept completely dry. It is also important that the pressure vessel is inspected from time to time. This requires the chemical powder in the vessel to firstly be removed from the pressure vessel, and thereafter be replaced in the pressure vessel. It is important that this be done with a minimum of mess and powder dispersal.

As shown in figures 1 to 3, a dry chemical transfer system comprises a hopper 10 having a conical base 12, a cylindrical sidewall 14, and a closed top 16. A filter assembly

18 is mounted to the closed top 16 of the hopper. An outlet 20 is located at the apex of the base 12 and an inlet 22 is mounted to the closed top 16 of the hopper. The cylindrical section of the hopper has a capacity of approximately 200 litres.

Agitation of powder within the hopper is provided by dry compressed nitrogen supplied in a cylinder 24 located to one side of the hopper. Compressed nitrogen from the cylinder 24 is supplied into the hopper 10 via a series of apertures 26 located in the base 12 of the hopper. The apertures 26 are configured in three rows extending around the circumference of the base, as shown, and those three rings of apertures 26 are supplied with gas via a manifold 28 arranged to feed the gas into the apertures 26. The compressed dry nitrogen is used to fluidise the powder located in the hopper to allow for rapid evacuation of the powder in the hopper when evacuation of the powder from the hopper is required. Emptying of the hopper will be described in more detail below and is provided through outlet 20 via a valve 30.

As shown in Figure 1 , a pressure vessel 32 will contains chemical powder to be emptied. The vessel 32 will typically be mounted in a vehicle (not shown) such as a fire truck or the like. A diaphragm pump 34 is used to pump dry chemical powder from the pressure vessel 32 to the hopper 10. The pressure vessel 32 has an opening 36 at the top thereof and a rigid tubular probe or lance 38 is passed into the pressure vessel 32 through this opening 36 to the base 40 of the pressure vessel. A conduit 42 connects the pressure vessel to the diaphragm pump 34 and a second conduit 44 connects the diaphragm pump to the hopper 10. Thus, the dry chemical powder is sucked out of the vessel 32 and travels in the direction of arrows 46 during the evacuation of the pressure vessel. The diaphragm pump 34 is powered by compressed air from a source (not shown) and a suitable pump 34 might comprise a "Graco Husky 1590 air operated diaphragm pump" which is adapted to pump dry chemical powder in the manner described herein. One type of powder with which the system might be used is a fire retardent known as "Purple-K dry chemical powder" which contains muscovite mica, magnesium aluminium, silicate, potassium bicarbonate, and other additives in small quantities. It is important that such materials be kept absolutely dry in order to flow freely and to be effective for the use intended. This is one reason why the system needs to be kept absolutely dry and why dry nitrogen gas is used for agitating the powder in the hopper. It will also be noted that the system is basically a closed system so that ambient moisture is not able to enter the system and increase the moisture content of the powder.

As the powder is pumped into the hopper 10, air will also pass into the hopper.

That air will escape from the hopper through the filter 18 but all powder particles will be retained within the hopper ensuring that the entire operation is carried out in a dust free manner. This ensures that the working environment is kept safe and dust free and also ensures that powder material is not wasted during the operation.

Figure 2 of the drawings shows the system in a mode in which powder is returned to the pressure vessel 32 from the hopper 10 via conduit 48. A return conduit 50 is provided from the pressure vessel 32 back to the hopper 10, this conduit 50 carrying displaced air and powder from the pressure vessel back to the hopper. Agitation of the powder material in the hopper 10 is accomplished by injecting dry nitrogen in the direction of arrows 52 shown in Figure 2 into the base 12 of the hopper in the manner described previously. It will be noted that the nitrogen supply is split in two via a three way valve 54 shown in Figure 2. Dry nitrogen is used to fluidise the dry powder along the conduit to the suction side of the diaphragm pump 34. From the pump, the powder is conveyed along conduit 48 to the pressure vessel 32. The pressure vessel 32 is fitted with a special adaptor 56 which will allow the two conduits 48 and 50 to be coupled to the pressure vessel, thereby ensuring that the operation is a dust free operation. The nitrogen is supplied via regulator 58 which can be adjusted to ensure that agitation of the powder in the hopper is just sufficient to liquify the powder, thereby ensuring free flow of powder from the hopper to the pressure vessel 32. This system may also be used to fill a pressure vessel with fresh powder in the manner shown in Figure 3 of the drawings. As shown, a supplier bucket 60 shown in Figure 3 is provided with fresh powder and diaphragm pump 34 is used to pump that powder via conduit 48 to the pressure vessel 32. The adaptor 56 is used in this operation to ensure dust free transfer, and conduit 50 connects the pressure vessel 32 to the hopper 10 to convey displaced air and powder to the hopper 10 where the air is filtered via the filter 18.

It is envisaged that the system will typically be used only with the same chemical powder to thereby ensure contamination either with moisture or other powders does not occur. It will be appreciated that the couplings of the various conduits to the pumps and vessels will need to be made in a manner, which ensures an air tight connection and quick coupling. It is envisaged that couplings such as cam lock couplings will be used to allow for rapid air tight connection.

It should be noted that an alternative to filling the pressure vessel from the supplier bucket 60 as shown in Figure 3 would be to fill the hopper 10 from the supplier bucket 60. The powder can then be stored in the hopper for a period and then used to fill the pressure vessel whenever the powder in the pressure vessel has been used or discharged for any reason. In that instance, the conduit 48 will be connected to the hopper 10 rather than the pressure vessel 32. One embodiment of hopper is shown in Figure 4 of the drawings. As shown, hopper 10 is mounted on a wheeled chassis 62 and then supported on that chassis via four braces 64 connected to the sides of the hopper. Figure 4 shows the manifold 28 extending around the base of the hopper for supplying liquid nitrogen to the apertures 26.

The wheeled chassis 62 will allow the hopper to be brought alongside a vessel which needs to be filled or emptied, thereby ensuring a quick and efficient transfer of dry chemical powder as and when required. Typically the pump 34 and gas cylinder 24 will be mounted on the chassis 62 along with all necessary conduits.

A further embodiment of the invention is the addition of a cylindrical attachment, which is used for the purpose of capturing dry chemical powder discharged from a dry chemical powder applicator fitted to the dry chemical powder vessel.

As shown in Figure 5, the cylindrical attachment 70 fits between the top of the hopper 10 and a removable closed top 72, and is fixed at each end by clamping means. The cylindrical attachment 70 comprises a cylinder 73, a cone 74 which is fitted inside the cylinder 73. The cone 74 has a truncated apex 75. The base of the cone 74 is fitted flush with the top of the cylinder 73. An inlet duct 76 is fitted horizontally and tangential to the top exterior surface of the cylinder 73.

In use, the pressure vessel 32 is charged with a propellant gas (usually nitrogen) which is discharged through a dry chemical powder applicator 78. Dry chemical powder mixed with gas is discharged from the pressure vessel 77 through the applicator 78 and into the cylindrical attachment 70 via the inlet duct 76. As the powder and gas mix enters the cylindrical attachment 70 it will travel in a downward spiral and deccelerate. The powder and gas will separate at the truncated apex 75 of the cone 74. The powder will be collected in the hopper 10, and the gas will escape through the filter 18 via the aperture in the truncated apex 75. A further embodiment of the invention is the addition of an indicating means to identify when the filter requires cleaning.

It will be appreciated that there may be many variations to this embodiment without departing from the scope of the invention. In particular, the components need not be in a form depicted in the drawing. It will be understood that the invention disclosed and defined herein extends to all alternative combinations of two or more of the individual features mentioned or evident from the text or drawings. All of these different combinations constitute various alternative aspects of the invention. The foregoing describes embodiments of the present invention and modifications, obvious to those skilled in the art can be made thereto, without departing from the scope of the present invention.

Claims

Claims:

1 A dry powder transfer system comprising: a hopper adapted to store a quantity of dry powder, the hopper having an inlet and an outlet and means for agitating powder within the hopper, and a filter means adapted to allow flow of air out of the hopper whilst retaining powder material within the hopper; pumping means for pumping powder to and from the hopper; conduits for connecting the hopper to a vessel to which or from which powder is to be conveyed; said pumping means adapted to be used to convey powder between said hopper and a said vessel along said conduits.

2. A dry powder transfer system according to claim 1 wherein the hopper has a downwardly convergent conical base and the outlet from the hopper is located at the apex of said conical base.

3. A dry powder transfer system according to claim 2 wherein the agitation means comprises a supply of compressed gas which is supplied to said hopper via a series of apertures located in said conical base.

4. A dry powder transfer system according to any preceding claim wherein said pumping means comprises a diaphragm pump which in use is powered by compressed air supplied by a compressor able to supply air at an operating pressure of at least 400 kPa.

5. A dry powder transfer system according to any preceding claim wherein the hopper has a truncated conical separator located in an upper region thereof which is adapted to separate dry powder from gas used to convey the powder into the hopper.

6. A dry powder transfer system according to any preceding claim wherein the vessel comprises a pressure vessel mounted to a fire truck.

7. A method of emptying dry chemical powder from a pressure vessel, said method including the steps of: providing a conduit adapted to be located in said pressure vessel; agitating the chemical powder in said pressure vessel and applying a negative pressure to said conduit to thereby suction the powder into the conduit; allowing the powder to pass along said conduit to a hopper; and separating the powder from gas in the hopper, whilst retaining the powder in the hopper.

8. A method of filling a pressure vessel with dry chemical powder from a hopper, said method including the steps: agitating the powder in the hopper with a substantially moisture free gas; pumping the powder and gas from the hopper to the pressure vessel; allowing gas and some entranced chemical particles to return from the pressure vessel to the hopper along a return conduit; and separating the gas and chemical particles in the hopper, retaining the chemical particles in the hopper.

9. A method according to either of claims 7 or 8 wherein said pressure vessel is located on a fire truck and is adapted to contain chemical powder used for fire extinguishing.

10. A dry powder transfer system substantially as hereinbefore described with reference to the drawings.

11. A method of transferring dry chemical powder substantially as hereinbefore described with reference to the drawings.