WO1990005596A1

WO1990005596A1 - Improvements in and relating to pressure vessels

Info

Publication number: WO1990005596A1
Application number: PCT/GB1989/001397
Authority: WO
Inventors: Thomas Walter Bunyan
Original assignee: Pilgrim Engineering Developments Ltd
Current assignee: Pilgrim Engineering Developments Ltd
Priority date: 1988-11-22
Filing date: 1989-11-22
Publication date: 1990-05-31
Anticipated expiration: 1991-05-22
Also published as: GB8827261D0

Abstract

A self-contained brushing unit is used to clean the inner surface of a stud bolt hole (30), by rotating/traversing a brush (9) over the surface. The unit is preferably powered by an internal battery.

Description

Improvements in and relating to pressure vessels

Large pressure vessels have removable covers which are held in place by a number of heavy studbolts which could be up to 8 inches (20.3cm) diameter and 72 inches (1.83 metres) long, screw-threaded at each end. These studs are usually screwed into correspondingly threaded holes in a flange which is integral with^* the body of the pressure vessel. They pass through clearance holes in the cover and the assembly is secured by retaining nuts resting on self-aligning washers. The studs are hydraulically stretched while the nuts are screwed down. The present invention is concerned with cleaning out the stud bolt holes during the dead time while the cover and the stud bolts are removed to gain internal access to the pressure vessel for maintenance pruposes. This task is important in order to avoid seizure on re-assemblv. Thread cleaning is usually carried out dry using two or three hand-controlled externally mounted machines taking about 15 minutes for each of approximately 60 studs. Using three machines, this corresponds to 5 hours 'critical path time' during which free access to the vessel is restricted. It is an object of the present invention to carry out the stud hole cleaning operation without restricting access and indeed even when personnel access is not feasible for any reason.

According to the present invention a stud bolt hole cleaner is characterised by the combination of a brush rotatable about the axxs of the stud bolt hole to sweep the inner surface thereof, together with self-contained means for rotating the brush and traversing it axially to cover substantially the whole of said surface, including means for automatically reversing said traversing action at each end of the surface to be cleaned, the cleaner being mounted to a plug member which, in use, closes the stud .bolt hole to prevent entry of adventitious material.

Preferably, the cleaner is electrically operated and the direction of traverse is reversed at each end of the surface to be cleaned. Limit switches may be used for this purpose, so that in the case of a battery operated cleaner, operation will be completely automatic, the rotating/traversing movement of the brush continuing until the battery is -discharged. In a preferred embodiment, the invention provides a completely self-contained compact rotating wire brush dry thread cleaner, one of which is introduced into each hole, is battery-driven, and performs the cleaning operation until the batteries are discharged, i.e. approximately 8 hours cleaning time. A reversing switch automatically reverses the supply polarity to the motor at each extremity of its travel. Other than placing the cleaner and subsequently removing it, no personnel involvement is necessary.

The cleaner preferably includes a filter element to trap cleaned-off debris, optionally in conjunction with a magnet, to catch ferrous debris. The motor used to operate the brush (including traversing it) may also be used to operate a fan which circulates air through the filter element, and over the magnet, if present. However, better utilisation of the battery may be achieved by providing a second motor, whose sole function is to operate the fan. Air circulation and brush operation may thus be separated, thereby simplifying construction.

In order that the invention be better understood a preferred embodiment of it will now be described by way of example with reference to the accompanying drawings, in which;- Figure 1 is a cross-sectional side view of a stud bolt hole equipped with a cleaner according to the invention, and

Figure 2 is a- plan view, partly cut-away of the cleaner of Figure 1.

Referring to both figures a light crosshead square section ring (2) carries four wire brushes (9) on cantilever plate springs (9a) which are rigidly attached at the four corners to the crosshead ring (2), which is a sliding fit on a square section driving tube (1).

The driving tube (1) is rotated, by an electric motor through through a reduction gear box (6) at one end of the motor shaft. The other end of the motor shaft drives a fan (8) at full motor speed at the other end. A perforated tubular chassis (11) supports the motor (3) the fan (8) and the gear box (7). The chassis is covered with a fine mesh (muslin) filter tube (11) to isolate the debris wire- brushed out of the threads and circulated by the air blast from the fan. The reversing switches are shown at (13). A magnetic filter deals^' with the metallic particles, i.e. scuffing and frettage off the threads.

As previously indicated, the fan (8) may be operated by a completely separate motor and in many cases this will be preferable, since it enables the characteristics of the two motors to be optimised quite independantly. In general terms, the brushing/traversing action may be better handled by a slower speed motor, whilst air circulation via the fan (8) may be better accomplished by means of a higher. speed motor.

The power supply is from internal batteries, either the U2 size contained in tubular boxes (4) or the flat type as (4a) or alternatively from an external power supply through a watertight plug and socket (not shown).

It will be appreciated tu__.t the whole apparatus is shown in-situ, in a stud bolt hole in a pressure vessel flange generally indicated by (30).

The whole apparatus is carried by a plug (5) which closes and seals the stud bolt hole, preventing entry of any solids/liquids which may be in the vicinity as a result of whatever operations are being carried out on or in the pressure vessel of which the pressure vessel flange (30) forms a part.

Cleaning of the machine is very simple^' as it remains attached to plug (5) when removed to the fitting shop after use. It may be simply upended and connected to a power supply via plug (18), so that the fan 8 will blow out accumulated debris via slots (17). The magnet may also be removed and cleansed of all metal particles, ready for re-use.

Claims

CLAIMS : -

1. A stud bolt hole cleaner characterised by the combination of a brush rotatable about the axis of the stud bolt hole to sweep the inner surface thereof, together with self-contained means for rotating the brush and traversing it axially to cover substantially the whole of said surface, including means for automatically reversing said traversing action at each end of the surface to be cleaned, the cleaner being mounted to a plug member which, in use, closes the stud bolt hole to prevent entry of adventitious material.

2. A stud bolt hole cleaner according to claim 1 characterised in that the self-contained means is an electric motor, the means έor automatically reversing the traversing action being limit switches.

3. A stud bolt hole cleaner according to claim 2 characterised in that the unit is self-contained and that the motor is operated by an internal battery.

4. A stud bolt hole cleaner according to claim 2 characterised in that the motor is operated by an external power supply.

5. A stud bolt cleaner according to any of claims 1-4 further characterised in that the motor has a drive output shaft at each end, one shaft driving the brush assembly through a gearbox and the other shaft driving a fan disposed to circulate air for cooling and for the collection of cleaned-off debris.

6. A stud bolt cleaner according to any of claims 1-4 characterised by the provision of a second motor which serves to circulate air for cooling and for the collection of cleaned-off debris.

7. A stud bolt clectuor according to any of claims 1-6 characterised by the inclusion of a filter element for receiving cleaned off debris.

8. A stud bolt cleaner according to claim any of claims 5-7 further including a magnet for retaining ferrous particles.

9. A stud bolt cleaner substantially as herein described with reference to and as illustrated by the accompanying drawings.^'