IE893291A1 - Work platform assembly - Google Patents

Description

The present invention relates to work platforms and in particular to a work platform assembly for the interior of a bulk tank or vessel having an access door.

Bulk tanks are used extensively for storage and in the process lines of many plants both for liquids and powders. Process materials often undergo a chemical reaction, for example, oxidation, in such tanks which generates heat. All these oxidation reactions are exothermic and the rate of the chemical reaction increases rapidly as the ambient temperature rises. Thus, with many powder materials these conditions can give rise to spontaneous combustion or explosion. This is a particular problem in the spray drying of milk powder where powder can accumulate and layers of powder are deposited on the walls of the spray drier tank. It is estimated that the losses to the industry are very large and whilst the spray drying of milk is not considered to be a very hazardous process obviously any spontaneous ignition leads to product degradation and the experience is that minor fires occur very regularly and occasionally result in a more dramatic explosion. That explosions do not occur very often is due to the fact that milk powder is not a highly explosive dust nor - 2 is it readily ignited. However, spontaneous combustion from purely economic reasons must be prevented as well as an explosion for safety reasons. The only way this can be done is to prevent the build up of deposits of drying milk powder in the spray drier and this has to be monitored and cleaning intervals and procedures arranged to ensure that a critical thickness of powder is never deposited on any portion of the spray drier.

Unfortunately, the more often the plant has to be cleaned the 10 greater the down time. Indeed, the conventional way of cleaning the plant and the tanks is to shut down the plant and erect a scaffolding within the spray drier tank and carry out the necessary work within the tank. This is obviously a time consuming operation. The present invention is directed towards overcoming this problem.

According to the invention there is provided a work platform assembly for the interior of a vessel having an access door comprising:a work platform; a base for mounting outside the vessel; a boom assembly on the base for support of the work platform and for projecting into the vessel; and - 3 means for moving the assembly to allow the work platform traverse the interior of the vessel.

In one embodiment of the invention the boom assembly comprises :5 a telescopic lower boom mounted on the base and a further telescopic upper boom carrying the work platform; means for telescoping each boom; and means for moving upper boom relative to the lower boom.

Preferably the upper boom is rotatably and pivotally mounted to the lower boom.

Typically, the upper boom is movable relative to the lower boom by rotating, raising and lowering the upper boom relative to the lower boom.

In a preferred embodiment the upper boom is pivotally mounted 15 for vertical movement on an upstanding boom support which in turn is mounted by a slew ring assembly on the lower boom, the slew ring assembly allowing pivotal movement of the support about a substantially vertical axis. - 4 The slew ring assembly may be offset laterally on the lower boom and ideally comprises a slew ring gear driven by a pinion and associated worm and wheel gearbox and motor.

In another embodiment telescoping of the booms and the raising 5 and lowering of the upper boom is achieved by fluid operated double acting piston and cylinder assemblies.

In a preferred embodiment control means for operating the assembly are provided on the work platform. Further, the work platform is preferably pivotally mounted and counterweighted for gravity self levelling. Again, it is preferable that the work platform be fitted to one side of the upper boom.

The invention will be more clearly understood from the following description of an embodiment thereof, given by way of example only, with reference to the accompanying drawings in which :Fig. 1 is a side view of the work platform assembly outside a bulk spray drying tank, Fig. 2 is a side diagrammatic view of the assembly in the position of use, Fig. 3 is a side view of the assembly, and Fig. 4 is a plan view of the assembly. - 5 Referring to the drawings there is provided a work platform assembly 1 which is illustrated in Fig. 1 and 2 mounted on a ramp 2 which in turn is mounted outside a spray drier tank or vessel 3 having an access door 4. Referring specifically to Figs, 3 and 4 the platform assembly comprises a base 5 having ground engaging castors 6 and mounting jacks 7. Locking means for rigidly securing the base 5 to the ramp 2 is provided by a number of brackets 7a on the base 5 secured to the ramp 2 by bolts. Mounted on the base 5 is a telescopic lower boom 8 which is extended and retracted by a double acting piston and cylinder assembly namely, an hydraulic ram 9. Mounted at a free end 10 of the lower boom 8 by a slew ring assembly is a pedestal 11 on which is mounted an upstanding boom support 12. The slew ring assembly includes a slew ring gear 13 which in this embodiment is driven by a pinion and associated worm and wheel gearbox and a reversible hydraulic motor, none of which are illustrated.

It will be noted that the boom support 12 is mounted offset from the centre of the pedestal 11. The boom support 12 supports by a pivot mounting 14 a telescopic upper boom 15 which in turn is moved inwards and outwards by a further hydraulic ram 16. Another hydraulic ram forms a Derrick ram 17 for raising and lowering the upper boom 15 relative to the pedestal 11. A work platform, in this case, a basket 18, is secured by a pivot mounting 19 at a free end 20 of the upper boom 15. The basket 18 contains all the controls for - s operation of the work platform assembly 1. Additional support struts 25 shown by interrupted lines in Fig. 3 may be provided for rigidly securing the work platform assembly 1 against the side of the tank 3 or, for example, against the door frame of the tank 3.

In use, the work platform assembly 1 is moved into position adjacent the access door 4 of the tank 3 and the jacks 7 are used to level it on the ramp 2. It is then rigidly secured by bolting the brackets 7a to the ramp 2 and, if necessary, additional struts such as the strut 25 are bolted into position.

Referring now to Fig. 2 it will be seen how the extension of the lower boom 8 by the hydraulic ram 9 inside the spray drier tank 3 will permit the pedestal 11 to be placed adjacent the centre line of the spray drier tank 3. The upper boom 15 can be raised and lowered by the Derrick ram 17 and extended and retracted by the hydraulic ram 16. In Fig. 2 the basket 18 is illustrated in one position and by the use of interrupted lines various other positions of use are illustrated and do not require any further description. An operator in the basket 18 can thus move around the interior wall of the tank 3, de-scaling as necessary.

The work platform assembly is powered by a 24 volt DC system and ideally a mains charger is provided. Alternatively the work platform assembly may be powered by a 380V, 220V or 110V I - Ί AC supply. In some cases the work platform assembly may be powered by compressed air.

Ideally the hydraulic cylinders are fitted with over centre valves which act as lock valves and anti-hydraulic hose burst valves. These will prevent the cylinders from dropping in the event of hose failure.

The work platform assembly may be of any suitable materials of construction.

The invention is not limited to the apparatus hereinbefore 10 described but may be varied in constructional details.

Claims (12)

1. A work platform assembly for the interior of a vessel having an access door comprising:a work platform; 5 a base for mounting outside the vessel; a boom assembly on the base for support of the work platform and for projecting into the vessel; and means for moving the assembly to allow the work platform traverse the interior of the vessel. 10

2. A work platform assembly as claimed in claim 1 wherein the boom assembly comprises :a telescopic lower boom mounted on the base end a further telescopic upper boom mounted on the lower boom and carrying, the work platform; 15 means for telescoping each boom; and means for moving the upper boom relative to the lower boom. - 9

3. A work platform assembly as claimed in claim 2 wherein the upper boom is rotatably and pivotally mounted to the lower boom.

4. A work platform assembly as claimed in claim 2 or 3 5. Wherein the upper boom is movable relative to the lower boom by rotating, raising and lowering the upper boom relative to the lower boom.

5. A work platform assembly as claimed in any of claims 2 to 4 wherein the upper boom is pivotally mounted for 10 vertical movement on an upstanding boom support which in turn is mounted by a slew ring assembly on the lower boom, the slew ring assembly allowing pivotal movement of the support about a substantially vertical axis.

6. A work platform assembly as claimed in claim 5 wherein 15 the slew ring assembly is offset laterally on the lower boom.

7. A work platform assembly as claimed in claim 5 and 6 wherein the slew ring assembly comprises a slew ring gear driven by a pinion and associated worm and wheel gearbox 20 and motor.

8. A work platform assembly as claimed in any of claims 2 to 7 wherein telescoping of the booms and the raising and

9. 9.

10. 10.

11. 11.

12. 12. lowering of the upper boom is achieved by fluid operated double acting piston and cylinder assemblies. A work platform assembly as claimed in any preceding claim wherein control means for operating the assembly are provided on the work platform. A work platform assembly as claimed in any preceding claim wherein the platform is pivotally mounted and counterweighted for gravity self levelling. A work platform assembly as claimed in any preceding claim wherein the work platform is fitted to one side of the upper boom. A work platform assembly substantially as hereinbefore described with reference to the accompanying drawings.