This invention relates to experimental research techniques for components intended for use in high pressure, high temperature environments.

Pressure vessels for testing components in such environments are well known in the art. They typically comprise a container made from suitable materials within which can be enclosed a range of subject items for assessment and evaluation, which are tested within a fluid (gas or liquid) at a pressure and temperature substantially different to the ambient value.

In certain cases it is desirable for a force to be applied to a test piece to create, for example, strain, shear, compression or torsion within the piece. Such tests will depend upon the environment the piece must function in and the nature of the function. It is common to have a situation in which a piece is tested in water which is heated to a maximum temperature of around 350°C and is kept under high pressure to ensure the water remains liquid. A test can take many days.

To ensure a controlled load is being applied to the test specimen, it is common for a servo-electric load machine to be used, although any

mechanism capable of reaching the required load would be suitable, wherein the load arm passes through the container, ensuring that loads are applied to specimens within the pressure vessel. To achieve this, it is necessary for the load arm to pass through a sealing system housed in the pressure vessel wall. This leads to a number of undesirable losses- the fundamental frictional loss when a load arm passes through the container wall, the coefficient of which varies with the temperature of the content, the size of vessel and opening, and material used to create the seal. Different types of seal also vary in performance, and this in turn is likely to degrade over time, rendering calculations to compensate for the friction complex and prone to error.

Efforts to improve these systems have concentrated on minimising the resistance by the seal. The only way around this is to measure load

completely within the pressure vessel, circumventing the seal resistance issue. However, load cell calibration can drift at high temperatures and commercially available load cells are not suitable for operation in high temperature fluid.

Even if such a load cell were available, for operation in high temperature fluid, it would have to compensate for temperature internally- which would require a constant monitoring of its external surfaces including adjustments on seals in response to (potentially very rapid) temperature and/ or pressure changes. Whist this is potentially technically feasible, no such load cell is currently known.

It is an object of the present invention to overcome all of these problems and more by providing an improved load monitoring system. Accordingly, the present invention provides an apparatus for testing

components in a pressure vessel, comprising a first section for containing a component to be tested and a second section, the sections being separated by a baffle, such that the temperature in the first section can be varied whilst the temperature in the second section remains substantially constant by creating a heat gradient across the baffle, characterised in that the second section contains the load cell within the pressure vessel.

The baffle is sized so as to enable heat conducted through it from the hot section to be ejected to the outside of the vessel so that the cold side remains cold, and does not heat the cold side section significantly. Because there is little or no temperature fluctuation, there is more confidence in the calibration of the measurement equipment. In practise this has allowed for "hot" sections of circa 250°C to remain consistent with "cold" ones of circa 30- 40°C over prolonged periods (up to 3 months).

The size of the baffle is selected to enable effective heat transfer to take place to the outside wall of the vessel and the ambient environment, whilst preventing any significant heat transfer from the hot section to the cold section inside the vessel. It is possible to enhance such heat transfer by means of cooling fins or through additional cooling means such as water cooling. The material of the baffle might be selected from more than one substance where the heat transfer properties change so as to promote ejection of heat to the outside rather than into the cool section of the vessel.

Water cooling means could be through the baffle or could be through the second section of the tank (the constant temperature section.

In engineering terms, the most simple manner for effecting a force on the test piece is to use a pull rod through the baffle, although other means could be devised. In such a case the baffle will need to have one or more holes through it, depending on the nature of the rod. It is clear that in order for the invention to work, the clearance of the rod or rods through the hole or holes should be as small as possible allowing for pressure equalisation and thermal expansion of the rod or rods. A person skilled on the art would be able to evaluate the best configuration and dimensions to enable the invention to work effectively.

Clearly, the apparatus could be employed to test pieces in a cooled

environment, rather than a hot one. This could use air or water as the fluid (although clearly, water below freezing point would introduce other difficulties). In such a situation the baffle and/ or the fluid of the second section would need to be heated rather than cooled to maintain the temperature of the second section.

Similarly although this description focuses on pull rods, it is foreseeable that torsion, shear or compression or a combination thereof could be applied to a test piece according to the invention.

The invention will now be described with reference to the following drawings; Figure 1 shows a pressure vessel according to the invention.

Figure 2 shows a close up of the baffle.

In figure 1 there is a common type of autoclave or pressure vessel 10. There is a test piece 12 held in a water environment 14. The water is heated by heating elements which thereby increases the pressure within the vessel.

The test piece is connected at one end to a support frame in the vessel and at the bottom is connected to a pull rod 16 which in this case is used to apply tension and or compression to the test piece.

The pull rod 16 passes through a baffle 20, in this case through the centre of a round baffle. It is clear that there may be more than a single rod should an application require it. There is minimal clearance 18 between the rod and the hole in the baffle.

Below the baffle is the second cold section containing the electronics and in this case a load cell 13 which are sensitive to pressure variation.

Figure 2 shows the baffle 20 in detail. In this case the baffle is of an annular shape made of one material 22. Cooling fins 24 which align with the baffle are positioned on the outer wall of the autoclave 10. The fins may be of a second material of higher thermal conductivity than the baffle also be supplemented or replaced by cooling water or any other forced convection method either around the outside of the vessel or through the baffle itself.

This configuration has been chosen because the autoclave top is lowered onto the rig containing the experiment. In situations where it would be convenient to do so, a baffle could be constructed in which the fins extend through the walls of the pressure vessel. The baffle could in such case be constructed of a first material in which the fins made of a second material, are embedded. To aid heat transfer to the outside the second material could be of a higher thermal conductivity than the first. It might be advantageous to add water cooling routes within the baffle, to force additional heat transfer.