Storage Tanks

Abstract

In order to provide both access and venting openings to storage vessels, particularly for large quantities of food liquids, which vessels need to be cleaned often, a manway access door is provided with has a partially open stable position which may be used for venting during cleaning. The door is preferably part of a subassembly on its own frame for ease of removal and replacement for repair and maintenance. Spray devices for spraying cleaning liquids inside and outside may be provided.

Description

BACKGROUND OF THE INVENTION

This invention relates to storage tanks and the like and more particularly to a device for venting such a storage tank to atmosphere, especially during cleaning operations.

It is common practice to provide large atmospheric vents in storage tanks so that, when hot liquid is admitted to a cold tank or cold liquid to a hot tank, an unacceptably high or low pressure is not created in the tank by the heating or cooling of air therein or by condensation of vapors. This is important, particularly since storage vessels are not normally designed to withstand an internal vacuum, i.e. external pressure, and the pressure variations generated by these phenomena are often large enough to cause substantial damage to such tanks. This problem is particularly severe in vessels which are used for holding food products or other products requiring that the tank should be cleaned at frequent intervals. Such cleaning is commonly performed by admitting rinsing water and hot detergent solutions to the vessel. Such a vessel is therefore submitted to alternate heating and cooling by detergent solutions and rinse water. The rinse waters and detergents are also commonly applied to the vessel by means of a spraying mechanism operating under considerable pressure. This means that the changes in temperature may be particularly sudden.

In order to provide the necessary venting action, it is usual to fit vessels that are to be subjected to these conditions with a vent in the roof. Such a vent may be up to 12 inches (30 cm.) or more in diameter.

It is also common for vessels of this type to be fitted with a manway door to enable periodic internal inspection and cleaning.

Both these fittings require considerable reinforcement to the tank wall in their immediate vicinity, and in order to obtain adequate rigidity are usually themselves of substantial construction.

SUMMARY OF THE INVENTION

The present invention consists in a manway access door assembly including a door for attachment to a storage vessel means for mounting the door in closed position and means for opening the door to a partially open position for purposes of venting the vessel, the door being adapted to open further to allow access to the interior of the vessel, a splash plate adapted to partially close the aperture when the door is in closed and partially open positions, and means connecting the splash plate to the door for movement therewith beyond the partially open position.

Preferably, means are provided for maintaining the plane of the door substantially parallel to the aperture during opening to the partially open position.

The door may be fitted with cleaning devices for spraying cleaning and rinsing liquids on the inside and outside surfaces thereof when in the partially open position. The inside cleaning device, which may be a spray ball, may be fitted with a nonreturn valve to prevent escape of liquid from the tube when the level of liquid stored is above the level of the door. Such a door may also have a plate to prevent liquid sprayed against the outside surface from splashing out of the door aperture in the vessel.

Conveniently, the door is power operated for opening to the partially open position against the action of a closing spring, and releasable from the power operating means for manual further opening.

In one convenient embodiment, the whole door and power operating device are mounted on a frame which is adapted to be attached to a suitably reinforced aperture in the storage vessel.

The invention will be further described with reference to the accompanying drawings, which show a preferred embodiment of the invention, and wherein:

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side elevation of one form of door according to the invention in position on the side of the tank; and

FIG. 2 is a horizontal section of the door of FIG. 1 and an adjacent part of the tank.

DETAILED DESCRIPTION OF THE DRAWINGS

The door 1 illustrated is mounted on a separate subassembly on its own frame 2 adapted to be attached by studs 3 to a suitable reinforcing flange 4 welded around an aperture in a tank 5 (only a small portion of which is shown in the drawings). A gasket 6 is inserted between the frame 2 and flange 4. The frame has a channel section extension 7 which carries pivot pins 8 and 9 for the door 1 and an operating cylinder-piston unit 10 respectively. The pin 8 carries a hinge 11 which supports the door by means of a bifurcated end 12 receiving one end of a column 13 pivoted by a pin 14. The door 1 normally seats on a flat seat surface 15 on the frame 2 with the interposition of a sealing ring 16.

The door is raised off its seat surface 15 by means of the cylinder 10, which is a single-acting pneumatic cylinder, and it is normally held against the seat surface 15 by closing springs contained inside the cylinder 10. The stroke of the cylinder 10 is such as to move the door away from the seat surface 15 for purposes of venting, but it is not intended that this cylinder 10 should provide sufficient opening for manual access.

Mounted on the column 13 are four radial arms 17. Four bolts 18 pass through the extremities of these arms and are attached to an annular splash plate 19, so that springs 20 surrounding the bolts will urge the plate against a seating surface 19a of the frame 2. It should be noted that the stroke of the cylinder 10 is not sufficient to free the plate 19 from the frame 2. By means of this assembly, the column 13 is guided so that the door 1 is maintained parallel to the wall of the vessel 5 in the immediate vicinity of the door aperture and an even annular gap 21 is thus provided round its edge.

The tank is thus vented through the gap 21 and an aperture 22 centrally of the plate 19.

The column 13 supports a hollow spindle 23 to which the door 1 and a reinforcing and locating collar 24 are welded. The inner end of the hollow spindle carries a spray ball 25 and a nonreturn valve 26, loaded by a spring 27 anchored to a cross pin 28, prevents back leakage of liquid from the vessel into the hollow spindle 23. An inlet connection 29 provides for the supply of cleaning and rinsing liquids to the hollow spindle 23. The column 13 has a flange 30 defining a cavity 31 around the spindle 23 and a nozzle element 32 is lockable on the spindle 23 by means of a setscrew to provide an annular nozzle 33 of adjustable width around the cavity 31, which is fed with cleaning and rinsing solutions by means of an inlet connection 34. The cleaning and rinsing solutions are supplied by means of suitable flexible hoses.

These solutions issue through the valve 26 into the spray ball 25 and are then sprayed into the vessel. This provides cleaning action for the major area of the door while the annular area around the perimeter of the outer surface of the door which is masked by the door itself from the spray ball 25, is cleaned by means of the annular nozzle 33.

Plate 19 is also designed to prevent spray from the nozzle 33 from escaping through the door aperture while the back (outer surface) of the door 1 is being cleaned by the spray.

Fitted to the extension 7 are two microswitches 35 (only one of which is visible in the drawing) which detect the position of the hinge 11. These switches detect respectively the open and closed positions of the hinge, and are used to interlock the movement of the door with the cleaning control system where this is automatic.

When it is required to use the door for access to the interior of the vessel, air is applied to the cylinder 10, to release the tension of the internal spring, and a pin 36 is withdrawn from the hinge assembly and the door 1 is then free to be swung into the interior of the vessel. In this case, the plate 19 will of course move the door. The presence or absence of the pin 36 may be detected by an electric or pneumatic switch which may be used as a further interlock in the cleaning control system.

By forming the door and its frame as a complete subassembly, the whole arrangement may be easily removed for repair or maintenance and replaced.

Various modifications may be made within the scope of the invention. Thus the microswitches 35 may be replaced by pneumatic controls. Also, the cylinder 10 may be hydraulically operated, or may be replaced by an electrical operating mechanism.

Claims

I claim:

1. In a manway access door assembly comprising a door for attachment in an aperture in a storage vessel, means for mounting the door in closed position, and means for opening the door to partially open position for purposes of venting the vessel, the door being adapted for further opening to allow access to the interior of the vessel, the improvement including a splash plate adapted to partially close the aperture when the door is in closed and partially opened positions, and means connecting the splash plate to the door for movement therewith beyond the partially open position.

2. The manway access door assembly as claimed in claim 1, comprising switch means for detecting the partially open and the closed positions of the said door.

3. The manway access door assembly as claimed in claim 1, including power means for opening the door in which the door is releasable from the power means for manual further opening.

4. The manway access door assembly as claimed in claim 1, in which said mounting means includes a column to which the door is fixed and means for constraining the column to move in a fixed relationship to the aperture during the opening to the partially open position.

5. The manway access door assembly as claimed in claim 1 comprising a spray device extending through the splash plate and door and supported in part by the means connecting the splash plate to the door for spraying the inside surface of the door with cleaning liquids and a flow passage passing through the door for supplying cleaning liquids to the spraying device.

6. The manway access door assembly as claimed in claim 5, including a non return valve in the passage for preventing leakage of liquid from within the tank down the passage.

7. The manway access door assembly as claimed in claim 1, including a spray device between the splash plate and the door supported in part by the means connecting the splash plate to the door for spraying cleaning liquids at the outside of the door.

8. The manway access door assembly as claimed in claim 1 comprising a column on which the door is mounted and in which the splash plate cooperates with the column to maintain the door in parallel relationship to the aperture during opening to the partially open position, and said plate being movable with the door to a position clear of the aperture during said further opening.

9. The manway access door as claimed in claim 1, comprising a frame, said door said maintaining means and said closing means being mounted on the frame to form a sub assembly for attachment to the vessel adjacent the aperture.

10. The manway access door assembly as claimed in claim 1 comprising a seating surface for the splash plate, and spring means urging the splash plate against the seating surface, the spring means serving as connectors between the splash plate and the door and functioning to maintain the plane of the door substantially parallel with the aperture during opening to the partially open position.

11. The manway access door assembly as claimed in claim 10 including a column on which the door is mounted, a set of radial arms mounted on the column and individual springs acting between the arms and the splash plate to urge the splash plate onto the seating surface and to maintain the arms and the door parallel with the seating surface when the door is between the closed and partially open positions.