GB2407585A

GB2407585A - Method and apparatus for treating the internal surface of a hollow vessel

Info

Publication number: GB2407585A
Application number: GB0325936A
Authority: GB
Inventors: Frank Morris
Original assignee: STAINLESS RESTORATION Ltd
Current assignee: STAINLESS RESTORATION Ltd
Priority date: 2003-10-31
Filing date: 2003-10-31
Publication date: 2005-05-04
Anticipated expiration: 2023-10-31
Also published as: GB0325936D0; GB2407585B

Abstract

A method is disclosed for treating the internal surfaces of a generally closed, hollow vessel (1, Fig 1), such as a stainless steel domestic hot water cylinders, having first (3, Fig 1) and second (4, Fig 1) apertures that are spaced along the length of the vessel. The vessel is provided with a removeable internal spray head (7) located through the first of the apertures and then, with the vessel in an orientation such that the first aperture is the upper of the two apertures, treatment liquid is introduced into the spray head such that the liquid issues from the spray head to treat the inner surfaces of the vessel. Treatment liquid is continuously drained from the vessel via the second aperture. Apparatus 10 for carrying out this method comprises at least one treatment station provided with means for supporting the vessel at the station in the orientation described. The apparatus further comprises a tank (11) for holding a treatment liquid, a spray head (7) for location through the first aperture of the vessel for issuing treatment liquid to treat the inner surfaces of the vessel. Means are also provided for supplying treatment liquid from the tank to the head as well as drain means (14) for returning treatment liquid discharged from the second aperture to the tank.

Description

Method and Apparatus for Treatine Internal Surface(s) of a Hollow Vessel

The present invention relates to a method and apparatus for treating the internal surface(s) of a generally closed, hollow vessel and more particularly such a vessel having first and second apertures that are spaced along the length of the vessel.

An example of such a vessel is a cylindrical vessel intended for use as a hot water cylinder in a domestic or commercial water supply.

For many years, hot water cylinders have been made of copper. There is however now a trend to produce such cylinders from stainless steel, e.g. a 2304 duplex grade of stainless steel. During manufacture, the cylinder undergoes a fusion welding process (e.g. using tungsten inert gas welding) . This process can affect the corrosion resistant properties of the material, particularly in the areas adjacent to the weld. It is important that the corrosion resistant properties be restored particularly in view of the fact that the interior of the cylinder will come into contact with hot water that may contain relatively high levels of chloride. Thus an acid treatment ("pickling") is used to restore the corrosion resistant properties of the material.

Currently stainless steel cylinders of the type described in the previous paragraph are acid treated in a "batch-like" matter simply by filling the cylinder with acid and then flushing with water. However such a process is time consuming and labour intensive.

It is therefore an object of the present invention to obviate or mitigate the above mentioned disadvantages.

According to a first aspect of the present invention there is provided a method of treating the internal surface(s) of a generally closed, hollow vessel having first and second apertures that are spaced along the length of the vessel, the method comprising providing the vessel with a removable internal spray head located through the first of the apertures and then, with the vessel in an orientation such that said first aperture is the upper of the two apertures, introducing treatment liquid into the spray head such that the liquid issues from the spray head to treat the inner surface(s) of the vessel, and continuously draining treatment liquid from the vessel via the second aperture.

The invention therefore provides a continuous method for the treatment of the internal surface(s) of generally closed hollow vessels. More particularly, the method is effected by spraying the treatment liquid from a spray head located through a first aperture which (in the "treatment orientation" of the vessel) is at a higher level than a second aperture from which the treatment liquid is continuously drained. This process overcomes the disadvantages associated with the batch process outlined above.

The method of the invention is applicable particularly to the treatment of vessels in which the first aperture is provided in the vessel wall towards one end of the vessel and the second aperture is provided centrally in the opposite end of the vessel.

The invention has particular application to the treatment of cylindrical vessels made of stainless steel which are intended for use as cylinders in domestic or commercial hot water systems. The invention is particularly applicable to stainless steel vessels (e.g. formed using a welding operation such as that described above) intended for use as domestic or commercial hot water cylinders. For the treatment of stainless steel vessels, the treatment liquid will be an acid (e.g. nitric acid or hydrofluoric acid). Such a treatment will improve the corrosion resistance at the interior of the vessel, particular adjacent to any weld lines.

Whilst the invention finds particular application in the acid treatment of stainless steel vessels, it will be appreciated that the invention is more generally applicable and could be applied to vessels of other materials and using treatment liquids other than acids. Thus, in a simple case, the method could be used for the washing of the interior surface of a vessel (steel or otherwise).

In operation of the method, it is preferred that at least a portion of the treatment liquid issuing from the spray head is directed at the interior surface at the end of the vessel adjacent the first aperture. That (internal) end is thus treated by the spray and the walls of the vessel may be treated by a combination of being contacted by spray and liquid draining down the walls under gravity.

In a particular preferred embodiment of the invention, the spray head is spherical and has a plurality of apertures for directing treatment liquid in a number of different radial directions, preferably to provide a 360 spray pattern.

It is particularly preferred that treatment liquid discharged from the cylinders is re-circulated for further use. Thus, for example, the apparatus may be effected using an apparatus having a holding tank for the treatment liquid. In this case, the treatment liquid is supplied from the tank (e.g. by means of a pump such a centrifugal pump) to the spray head and treatment liquid discharged from the vessel is returned via a drain or a diaphragm air driven pump to the tank.

Conveniently the method of the invention may be effected simultaneously on two or more vessels using an apparatus having a plurality of vessel treatment stations.

The invention provides (in a second aspect) an apparatus for treating the internal surface of a generally closed hollow vessel having first and second apertures that are spaced along the length of the vessel, the apparatus comprising at least one treatment station provided with means for supporting the vessel at the station in an orientation such that the first aperture is the upper of the two apertures, the apparatus further comprising a tank for holding a treatment liquid, a spray head for location through the first aperture of the vessel for issuing treatment liquid to treat the inner surface(s) of the vessel, means for supplying treatment liquid from the tank to the head, and drain means for returning treatment liquid discharged from the second aperture to the tank.

In a preferred embodiment of the apparatus of the second aspect of the invention, the or each treatment station includes a fork for supporting a lower end of the vessel at the treatment station. The apparatus preferably also incorporates a drain for returning treatment liquid discharged from the vessel back to the tank. In a particular preferred construction, the drain has an inlet provided at the or each treatment station below the fork at the station.

The apparatus may be such that vessels to be treated are manually loaded at and removed from, the or each treatment station or alternatively lifting apparatus may be used. A further possibility is for the apparatus to include a conveyer system on which vessels to be treated are loaded and conveyed to and from a treatment station.

The invention will be further described by way of example only with reference to the accompanying drawings, in which: Fig. 1 schematically illustrates a domestic hot water cylinder to be treated in accordance with the method of the invention; Fig. 2 schematically illustrates the method of the invention; Fig. 3 is a detailed (to an enlarged scale) of a spray unit employed in the process depicted in Fig. 2; Fig 4 illustrates one embodiment of apparatus in accordance with the second aspect of the invention; Fig. 5 is similar to Fig. 4 but illustrates cylindrical vessels to be treated in position in the apparatus; and Figs. 5 and 6 are details of the apparatus shown in Fig. 4.

Reference is initially made to Fig 1 which illustrates a stainless steel domestic hot water cylinder 1 whereof the interior surface 2 is to be acid treated (i.e. pickled) by use of an apparatus in accordance with the invention as described more fully below with reference to Figs 2-7. The illustrated cylinder 1 is a generally closed vessel which, in use in a domestic hot water supply system, will be orientated as shown in Fig 1. Provided in a lower region of the cylindrical wall is an aperture 3 in which an immersion heater will ultimately be located. Additionally, the top of cylinder I has a water outlet port defined by a hot water draw pipe 4 projecting from a dished end 5 of the cylinder 1.

Although not illustrated in the drawing, the cylinder I may incorporate (as conventional) a heat-exchanger coil.

For the purposes of treating the cylinder 1, a spray head unit 6 is mounted therein (see also Figs 2 and 3). This unit comprises a generally spherical spray head 7 mounted on a lance 8 having a boss 9 that is screwed into aperture 3 such that the boss seals the aperture against egress of acid. As shown particularly in Figure 3, spherical spray head 7 has a plurality of apertures 7a to which are orientated in a number of different radial directions to provide a 360 spray pattern.

Cylinders 1 will generally incorporate apertures additional to those referenced as 3 and 4 in the drawings. In this case, any such additional apertures will be "plugged" before effecting the process of acid treatment which is described more fully below.

Fig 2 schematically illustrates treatment of the internal surfaces 2 of cylinders 1 in a treatment apparatus 10. This apparatus includes an acid holding tank 11 which is part of an acid re-circulation system incorporating a pump 12 for supplying acid to a manifold 13 and a drain system 14 including spaced upright inlet pipes 15 for returning acid to the tank 11. Although not illustrated in the drawings, tank 11 incorporates a heater (for heating the acid) and a thermostat to insure that the correct temperature is maintained. Generally, the acid will be maintained at a temperature of 40 to 60 C.

In use of the apparatus 10, the cylinders 1 are supported on the apparatus 10 in an inverted position (as compared to that shown in Fig 1) such that their hot water draw pipes 4 locate into the upper ends of drain inlet pipes 15. Additionally, hoses 16 serve to supply acid from the manifold 13 to the lances 8 and therefore to the spray heads 7.

The generally spherical spray head 7 incorporate a plurality of apertures 7a for directing spray jets in a plurality of different radial orientations such that the interior surfaces of the cylinders 1 are acid treated either by virtue of being contacted directly be spray from the head 7 or by virtue of passage of acid along the interior walls of the cylinder. Acid drains from the cylinders 1 via their hot water draw pipes 4 and then via the pipes 15 so as to enter the drain system 14 to be returned to tank 11 for re- circulation by the pump 12.

Figs 4-7 illustrate in more detail a structure of apparatus in accordance with the invention. For convenience, the same reference numerals used in Figs 2 and 3 are used for Figs 4-7 to donate the same components.

The apparatus 10 illustrated in Figs 4 and 5 is designed for the simultaneous treatment of a total of ten cylinders 1 that are arranged in two rows of five cylinders each. Fig 4 shows the apparatus without the cylinders I whereas Fig 5 shows the ten cylinders in position.

The apparatus 10 has a frame structure comprising lower end frame members 21 connected by a longitudinal rail 22 and an upper frame structure comprised of spaced uprights 23 which are mounted at their lower ends on the rail 22 and which at their upper ends are connected by a further rail 24.

As will be appreciated from Figs 3 and 4, the two rows of five cylinders 1 are arranged one on each side of the upper frame structure. For this purpose, five of the uprights 23 are provided at their lower ends and on each side with a horizontally projecting spar 25 (see also Fig. 6) terminating in a V-shaped fork 26 whereof the inner sides converge to a radiussed portion 27 (see Fig 7). As will be appreciated from the drawings, this radiussed portion 27 locates above the inlet pipes 15 of the drain system 14.

Additionally each of those uprights 23 provided with a pair of forks 26 are further provided (on each side) with a generally semi-circular location bracket 28 associated with a chain 29.

In use of the apparatus illustrated in Fig 3, each cylinder is located in an inverted position such that its dished end 5 is supported on the fork 26 with the hot water draw pipe 4 locating the radiussed portion 27 of the fork 26 and projecting into the inlet pipe 15 of the drain system. It will be appreciated that the bracket 28 partially encircles the outer surface of the cylinder I which can then be retained in position by virtue of the chain 29 extending between (and being fastened to) the free ends of the bracket 28.

Each such cylinder I to be treated is provided with a spray head unit 6 as described more fully above with reference to Figs 2 and 3. Each such spray head unit 6 is connected to the manifold 13 via the hose 16, each of which is associated with a valve 30 for controlling flow along the hose.

It should be appreciated that a number of amendments may be made to the illustrated embodiments. Thus, for example, the treatment apparatus 10 may be constructed so as to accommodate a greater or lesser number of cylinders. Thus, for example, such a modified apparatus might accommodate only one row of cylinders.

Alternatively or additionally there may be less than or more than 5 cylinders for each row supported by the apparatus.

It should also be appreciated that the apparatus may be used for treating different sizes of cylinders, e.g. 90 litre cylinders or 300 litre cylinders. At any one time, the cylinders being treated may be of the same or different sizes.

Claims

1. A method of treating the internal surface(s) of a generally closed, hollow vessel having first and second apertures that are spaced along the length of the vessel, the method comprising providing the vessel with a removable internal spray head located through the first of the apertures and then, with the vessel in an orientation such that said first aperture is the upper of the two apertures, introducing treatment liquid into the spray head such that the liquid issues from the spray head to treat the inner surface(s) of the vessel, and continuously draining treatment liquid from the vessel via the second aperture.

2. A method as claimed in claim 1 wherein the first aperture is provided in the vessel wall towards one end of the vessel and the second aperture is provided centrally in the opposite end of the vessel.

3. A method as claimed in claim 2 wherein the vessel is cylindrical.

4. A method as claimed in claim 3 wherein the vessel is intended for use as a domestic hot water cylinder.

5. A method as claimed in any one of claims 2 to 4 wherein at least a portion of the liquid issuing from the spray head is directed at the interior surface at that end of the vessel adjacent the first aperture.

6. A method as claimed in any one of claims I to 5 wherein the spray head is spherical and has a plurality of apertures for directing treatment liquid in a number of different radial directions.

7. A method as claimed in any one of claims I to 6 wherein the vessel is of stainless steel.

8. A method as claimed in any one of claims 1 to 7 wherein the treatment liquid is an acid.

9. A method as claimed in any one of claims 1 to 8 wherein the treatment liquid is held in a tank and the liquid is supplied to the spray head by means of a pump.

10. A method as claimed in claim 9 wherein the pump is centrifugal pump or a diaphragm air driven pump.

11. A method as claimed in claim 9 or 10 wherein treatment liquid discharged from the vessel via a second aperture is returned to the tank.

12. A method as claimed in any one of claims I to I 1 effected simultaneously on a plurality of vessels.

13. Apparatus for treating the internal surface of a generally closed hollow vessel having first and second apertures that are spaced along the length of the vessel, the apparatus comprising at least one treatment station provided with means for supporting the vessel at the station in an orientation such that the first aperture is the upper of the two apertures, the apparatus further comprising a tank for holding a treatment, a spray head for location through the first aperture of the vessel for issuing treatment liquid to treat the inner surface(s) of the vessel, means for supplying treatment liquid from the tank to the head, and drain means for returning treatment liquid discharged from the second aperture to the tank.

14. Apparatus as claimed in claim 13 wherein the spray head is spherical and has a plurality of apertures for directing treatment liquid in a number of different radial directions.

15. Apparatus as claimed in claim 13 or 14 including a pump for supplying treatment liquid from the tank to the spray head.

16. Apparatus as claimed in claim 15 wherein the or each treatment station includes a fork for supporting a lower end of the vessel at the treatment station.

17. Apparatus as claimed in claim 16 incorporating a drain for returning treatment liquid discharged from the second aperture of the vessel to the tank.

18. Apparatus as claimed in claim 17 wherein the drain has an inlet provided at each treatment station below the fork at the station.

19. A method as claimed in any one of claims I to 11 when carried out on the apparatus of any one of claims 12 to 18.

20. A method of treating the internal surface(s) of a generally closed, hollow vessel substantially as hereinbefore described with reference to the accompanying drawing.

21. Apparatus for treating the internal surface(s) of a generally closed hollow vessel substantially as hereinbefore described with reference to the accompanying drawings.