EP0530424A1

EP0530424A1 - An x-ray generating apparatus

Info

Publication number: EP0530424A1
Application number: EP91610073A
Authority: EP
Inventors: Luis Petersen
Original assignee: Andrex Radiation Products AS
Current assignee: Andrex Radiation Products AS
Priority date: 1991-09-03
Filing date: 1991-09-03
Publication date: 1993-03-10
Also published as: JPH05205896A

Abstract

In an X-ray generating apparatus, primarily for field use, comprising a casing (1) in which an X-ray tube (4) is arranged for emission of X-rays towards a beam port (13) provided in a wall (12) of said casing, the casing comprises means (5) for supplying a high voltage to said X-ray tube (4) and a radiation shielding (9, 10, 11), preferably made of lead, for preventing emission of X-rays in non-desired directions. At least part (14) of the shielding is applied externally to wall parts (12) of the casing surrounding the X-ray tube (4) and is protected against corrosion or mechanical damage by means of a protective cover (15), e.g. in the form of shock-absorbing rubber hose, which can be drawn onto the external shielding.

Description

The invention relates to an X-ray generating apparatus, primarily for field use, comprising a casing in which an X-ray tube is arranged for emission of X-rays towards a beam port provided in a wall of said casing, the casing further comprising means for supplying a high voltage to said X-ray tube and a radiation shielding, preferably made of lead, for preventing emission of X-rays in non-desired directions.
X-ray equipment of this kind is used for various field testing and examination purposes such as testing of welding joints in building structures or pipelines, and it is an essential requirement to the equipment that a sufficient shielding of the X-ray source is provided so as to define the desired emission of X-rays and prevent emission in non-desired directions to avoid risk of damage to the operating personel. For that purpose means must also be available so that the beam port can be closed in order to minimize radiation during warming up and testing of the equipment.
In the prior art devices of the kind referred to the shielding is arranged on the inner side of the compartment or section of the usually cylindrical casing in which the X-ray tube is positioned. Since the high voltage source for supplying power to the X-ray tube is arranged in the same compartment, which for that purpose must be filled with insulating oil or gas it has turned out that fractions or particles of the shielding, which normally consists of lead, may become detatched either by the mechanical handling of the casing during use or when dismantling the casing e.g. for replacement of the X-ray tube or cleaning of the interior of the above-mentioned compartment and thereby cause a considerable risk of flash-over from the high voltage source.
Moreover mounting of the shielding, during production is difficult and time-consuming due to the position internally in the high voltage compartment, for instance on the inner wall of the casing or on a separate carrying element for the shielding.
According to the invention the above-mentioned disadvantages are substantially removed by an arrangement which is characterized in that at least part of the shielding is applied externally to wall parts of the casing surrounding the X-ray tube.
By the external application of at least the part of the shielding surrounding the X-ray tube, the shielding may more easily be mounted and any presence of detached fragments from the shielding in the high-voltage compartment of the casing is avoided. The external positioning of the shielding further makes it possible to use alternative methods such as plasma-spraying for the application of the shielding.
In the typical case, in which the casing is substantially cylindrical with the X-ray tube and the beam port arranged in a defined compartment of the casing and the wall surrounding said compartment, respectively, the externally applied part of the shielding comprises substantially all the shielding at the cylindrical wall of the casing around the high voltage compartment. Only at one or both ends of the high voltage compartment there may still be a need for arranging a supplementary shielding element in the interior of the casing, but such an element will be relatively easily accessible by removal of the corresponding end wall of the casing.
In a preferred embodiment the externally applied part of the shielding is protected against corrosion by means of a protective cover. Such a cover may advantageously comprise a shock-absorbing material like rubber and to facilitate mounting it may be made in the form of a hose, which can be drawn onto the external shielding.
The protective cover may, however, also comprise a bandage of an epoxy-impregnated fiberglass material or it may comprise a metallic screen or be made of a heat shrinkable material.
In the following the invention will be further explained with reference to the drawings, in which

Fig. 1 shows a typical prior art X-ray generating apparatus for field use,
Fig. 2 a preferred embodiment of the X-ray generating apparatus according to the invention, and
Fig. 3 an enlarged cross-sectional view of a part of the wall of the casing of the apparatus in Fig. 2.

The X-ray generating apparatus shown in Fig. 1 comprises a cylindrical casing 1 with a carrying handle 2 at either end. Electrical power is supplied to the apparatus through a cable 3. An X-ray tube 4 is arranged together with a unipolar high voltage source 5 in a high voltage compartment 6 of the casing positioned between an electronics compartment 7 at one end of the casing and an external cooling radiator 8 at the other end of the casing. Inside of the compartment 6 a radiation shielding 9 is arranged at the cylindrical wall of the casing surrounding the X-ray tube 4 and the high voltage source 5 and at either end of the compartment 6 a disc-shaped transverse shielding element 10 and 11 respectively is arranged.
In the part of the shielding 9 covering the cylindrical wall 12 of the high voltage compartment 6 a beam port or window 13 is formed for the desired emission of X-rays from tube 4. The beam port 13 may as shown take the form of an opening allowing emission in a defined spatial angle, but may also be formed e.g. as a circumferential slit allowing emissions in all directions in a given radial plane, e.g. for inspection of circumferential welding seams in pipe lines.
As mentioned before the arrangement of the entire radiation shielding 9, 10 and 11 internally in the high voltage compartment 6 entails the risk that fragments of the lead shelding, which may become detached either due to the mechanical handling of the apparatus in field use or when disassembling the casing for cleaning or replacement of the X-ray tube, may cause flash-over in the filling of insulating oil or gas in the high voltage compartment, whereby the whole apparatus may become damaged.
In the embodiment of the X-ray generating apparatus according to the invention shown in Figs. 2 and 3, elements corresponding to elements in the prior art apparatus illustrated in Fig. 1 have been designated by the same reference numerals.
In the apparatus according to the invention the part 14 of the radiation shielding covering the cylindrical wall 12 of the high voltage compartment 6 is applied externally to the wall 16 and is protected against corrosion by means of a protective cover 15 on the external side of the shielding. Also the transverse shielding element 17 at the end of the high voltage compartment 6 facing the external cooling radiator 8 may be applied to the external side of the end wall 18 of the high voltage compartment 6.
In order to protect the external radiation shielding 14 against damage caused by mechanical handling of the apparatus in field use the protective cover 15 may advantageously comprise a shock-absorbing material and be made e.g. in the form of a rubber hose, which can be drawn onto the external shielding 14.
As an alternative the protective cover 15 may be applied in the form of a bandage of an epoxy-impregnated fiberglass material or it may comprise a metallic screen or be composed of a heat shrinkable material.
Although the invention has been described in connection with an X-ray apparatus with a unipolar high voltage source it is equally applicable to systems with a bipolar high voltage source.

Claims

An X-ray generating apparatus, primarily for field use, comprising a casing (1) in which an X-ray tube (4) is arranged for emission of X-rays towards a beam port (13) provided in a wall (12) of said casing, the casing further comprising means (5) for supplying a high voltage to said X-ray tube (4) and a radiation shielding (9, 10, 11), preferably made of lead, for preventing emission of X-rays in non-desired directions, characterized in that at least part (14) of the shielding is applied externally to wall parts (12) of the casing surrounding the X-ray tube (4).
An X-ray generating apparatus, as claimed in claim 1 in which the casing (1) is substantially cylindrical with the X-ray tube (4) and the beam port (13) arranged in a defined compartment (6) of the casing and the wall (12) surrounding said compartment, respectively, characterized in that said part (14) of the shielding comprises substantially all the shielding applied to the cylindrical wall (12) of the casing around said defined compartment (6).
An X-ray generating apparatus as claimed in claim 1 or 2, characterized in that said part (14) of the shielding is protected against corrosion by means of a protective cover (15).
An X-ray generating apparatus as claimed in claim 3, characterized in that the protective cover (15) comprises a shock-absorbing material.
An X-ray generating apparatus as claimed in claim 4, characterized in that said shock-absorbing material is rubber.
An X-ray generating apparatus as claimed in claim 5, characterized in that the protective cover (15) is made in the form of a rubber hose, which can be drawn onto the external shielding applied to the casing.
An X-ray generating apparatus as claimed in any of claims 3-6, characterized in that the protective cover (15) comprises a bandage of an epoxyimpregnated fiberglass material.
An X-ray generating apparatus as claimed in any of claims 3-6, characterized in that the protective cover (15) comprises a metallic screen.
An X-ray generating apparatus as claimed in any of claims 3-6, characterized in that the protective cover (15) is composed of a heat shrinkable material.