Patent Description:
In gas turbine engines, compressors and turbines typically have axially arranged sets of rotors, each comprising an array of blades mounted to rotor discs. The respective sets of rotors are located between end shafts on a tension stud that extends through all or part of the set of rotors. In operation, the rotation of the rotors causes high separation forces to develop in the rotors. To counter these separation loads, a compression load is applied to the shaft and the rotors prior to use to offset the separation loads that develop in operation. To develop the compression load in the shaft and rotors, the tension stud is stretched during assembly to develop a tension within the tension stud. The tension stud is then held in its stretched form by a load retainer that engages with the shaft. The tension stud will react against the shaft via the load retainer to apply the compression load to the shaft.

Due to the high loads required to counter the separation loads encountered in operation, the risk of injury to assembly fitters due to an energy release resulting from a failure of one or more components of the rotor assembly is high.

To overcome this problem, each component of the tooling assemblies is designed with a high factor of safety, which leads to increased size and weight of each component as well as increased expense. Further, each component is subject to regular non-destructive testing, which is time-consuming and leads to increased assembly time.

An alternative solution to overcome this problem is to utilise a robotic assembly to avoid interaction of an operator with the tool assembly during loading of the tension stud. However, this leads to significant expense.

<CIT> discloses a protective assembly engaging in case of tensile failure comprising an elongate tubular member, and a catcher rod. The tubular member has a first end portion and an opposite second end portion, and a fuse portion is positioned between the first end portion and the second end portion. A cross-sectional area of the tubular member is reduced at the fuse portion. The catcher rod has a first end portion and an opposite second end portion, with the catcher rod being accommodated concentrically within the tubular member. The second end portion of the catcher rod is secured to the second end portion of the tubular member. The first end portion of the tubular member is provided with a first divergent conical portion, and the first end portion of the catcher rod is provided with a second divergent conical portion. In the event of breakage of the tubular member, the second divergent conical portion impinges against the first divergent conical portion to limit the axial movement of the tubular member.

Hence a need for improving the system for applying a tension load to the tension stud is highly desirable.

According to a first aspect of the invention, there is provided a tool assembly for applying a load to a tension stud of a rotor assembly for a gas turbine, according to claim <NUM>. The tool assembly comprising: at least one safety apparatus for containing a release of energy from a tension stud of a rotor assembly. The safety apparatus includes a containment member configured to pivot about a pivot location. The containment member includes a retaining arm located on a first side of the pivot location and a catch located on a second side of the pivot location, wherein the containment member is movable about the pivot location to a first position in which the catch is engaged with a lip of a disc of the rotor assembly to position the retaining arm in a containment position. Hence there is provided a safety apparatus suitable for containing a load applied to a tension stud of a rotor assembly in the event of a failure of one or more components and/or connections of the rotor assembly. The provision of the safety apparatus significantly reduces the risk to nearby workers and equipment as any energy released by a failure of one or more components will be restrained by the safety apparatus. Further, the provision of safety apparatus as part of the tool assembly avoids the necessity to redesign current components, which are already in operation.

In one example, the catch is substantially hook shaped.

The safety apparatus may include a handle configured to move the containment member between the first position in which the catch is engaged with the lip of the disc of the rotor assembly and a second position in which the catch is not engaged with the lip of the disc of the rotor assembly.

The handle may include a cam shaped outer profile at an engagement location with the containment member, wherein the handle is movable relative to the containment member at the engagement location to move the containment member about the pivot.

The tool assembly may include two diametrically opposed safety apparatus connected to the tool apparatus. The provision of two diametrically opposed safety apparatus means that the energy released as a result of a failure will be shared between the two safety apparatus.

The tool assembly may include a biasing member configured to bias the containment member so the catch is not engaged with the lip of the disc of the rotor assembly.

The tool head may include a removable insert, the removable insert including a male thread for engaging with a co-operative female thread of the tool head and a female thread for engaging with a co-operative male thread of the tension stud. The removable insert may be made of a higher grade material compared with the rest of the tool head and so prolong the usable lifetime of the tool head.

The compression body may include a substantially cylindrical sidewall comprising an aperture. The provision of a substantially cylindrical sidewall comprising an aperture enables an operator to access the inside of the compression body. In one example, the operator is able to access a connector connected to a load retainer within the compression body.

The tool assembly may include a measurement apparatus configured to measure the elongation of the tension stud. The measurement apparatus may be used to determine that the tension stud has extended by a pre-determined amount, equivalent to a pre-determined tension load being developed in the tension stud and hence, a pre-determined compression load being applied to the shaft.

In one example, the measurement apparatus comprises a plunger configured to extend through the tool head and engage with the tension stud.

According to another aspect of the invention, there is provided a method of applying a load to a tension stud of a rotor assembly, according to claim <NUM>. The method includes connecting the tool assembly to the tension stud, engaging the compression body of the tool assembly with the disc of the rotor assembly, engaging the catch of the safety apparatus with the lip of the disc of the rotor assembly, actuating the actuator to apply a load to the tool head and the compression body, which causes a tension load in the tension stud. This method enables a load to be safely applied to the tension stud.

The catch of the safety apparatus may be engaged with the lip of the disc of the rotor assembly by movement of the handle.

The method may also include the step of measuring the elongation of the tension stud via measurement apparatus. The measurement apparatus may be used to determine that the tension stud has extended by a pre-determined amount, equivalent to a pre-determined tension load being developed in the tension stud and hence, a pre-determined compression load being applied to the shaft.

The method may also include the step of determining that the tension stud has elongated by a predetermined amount and rotating a connector connected to a load retainer which is co-operatively threaded to the tension stud, wherein the load retainer is moved so that it engages with the shaft of the rotor assembly.

<FIG> shows an example of a rotor assembly <NUM> of a gas turbine engine. The rotor assembly <NUM> shown in <FIG> includes a compressor rotor <NUM> and a compressor turbine <NUM>. In example, the turbine engine is an SGT-<NUM>, SGT-<NUM> or SGT-<NUM>.

A tension stud or tension bolt <NUM> is provided in the axial centre of the rotor assembly <NUM>, along an axis A of rotation of the rotor assembly <NUM>. In one example, the compressor rotor <NUM> has a compressor tension stud <NUM> and the compressor turbine <NUM> has a turbine tension stud <NUM>. The compressor tension stud <NUM> and the turbine tension stud <NUM> may be connected together via a threaded connector <NUM>.

In operation, the rotor assembly <NUM> is arranged to rotate about the axis A of rotation. All rotor parts shown in the figures may be substantially rotationally symmetric about the axis A of rotation. Stator parts are not shown in the figures and elements that interlock the rotors may not be shown in the figures.

The rotor assembly <NUM> includes one or more shaft elements, for example, an inlet shaft <NUM> and an exit shaft <NUM>.

The inlet shaft <NUM> and compressor discs <NUM> are provided around the compressor tension stud <NUM> and configured to rotate about the axis A of rotation.

Further, the exit shaft <NUM> and turbine discs <NUM> are configured to rotate about the turbine tension stud <NUM>.

The inlet shaft <NUM> and the compressor discs <NUM> may be interlocked axially between axially adjacent rotating parts. Further, the turbine discs <NUM> and exit shaft <NUM> may be interlocked axially between axially adjacent rotating parts.

For example, the inlet shaft element <NUM> and the compressor discs <NUM> may comprise corresponding teeth that mesh together to interlock the inlet shaft element <NUM> and the compressor disc <NUM>. A plurality of rotor blades <NUM> are held in place by the compressor discs <NUM>. In one example, a rotor blade <NUM> comprises a "t-shaped" root that is held in place between correspondingly shaped sections of the compressor discs <NUM>. In other examples, the rotor blades <NUM> may extend from the compressor discs <NUM> themselves in the form of a blisk.

The compressor turbine <NUM> has a similar arrangement to the compressor rotor <NUM> in which a plurality of turbine rotor blades <NUM> may be held in place by the turbine discs <NUM>. In one example, a rotor blade <NUM> comprises a "t-shaped" or "fir-tree" shaped roots that are held in place between correspondingly shaped sections of the turbine discs <NUM>. In other examples, the rotor blades <NUM> may extend from the turbine discs <NUM> themselves, in the form of a blisk.

As such, the compressor tension stud <NUM>, the inlet shaft <NUM>, the compressor discs <NUM> and the rotor blades <NUM> may rotate together at the same speed about the axis A of the rotor assembly <NUM>.

Further, the exit shaft <NUM>, the turbine tension stud <NUM>, the turbine discs <NUM> and the turbine blades <NUM> may rotate together at the same speed about the axis A of the rotor assembly <NUM>.

In one example of assembly, the exit shaft <NUM> is mounted vertically in a frame and the rotor assembly <NUM> is constructed in a top-down vertical orientation. In another example, the exit shaft <NUM> is mounted horizontally in a frame and the rotor assembly <NUM> is constructed in a horizontal orientation.

<FIG> shows a cross section of a schematic of part of the rotor assembly <NUM> along with a tool assembly <NUM> for applying load energy to the turbine tension stud <NUM>.

The tool assembly <NUM> includes a tool apparatus <NUM> and a safety apparatus <NUM>. The tool apparatus <NUM> includes a compression body <NUM> configured to engage with the turbine disc <NUM> of the rotor assembly <NUM>. In one example, the compression body <NUM> has a profile at one end that may correspond with a shape of the turbine disc <NUM> to ensure a positive engagement between the compression body <NUM> and the turbine disc <NUM>. The compression body <NUM> may be received in a cavity formed by a lip <NUM> or rim on the turbine disc <NUM>, such that in use, one end of the compression body <NUM> abuts against the lip <NUM> of the turbine disc <NUM>.

The compression body <NUM> may be substantially cylindrical with an axial hole therethrough such that one end of the tension stud <NUM> may be received in the compression body <NUM>. The compression body <NUM> may have substantially cylindrical shaped walls and may include an aperture to enable access to the inside of the compression body <NUM>. The compression body <NUM> also includes a projection angled away from the cylindrical wall of the compression body <NUM> to provide a pivot point <NUM> for the safety apparatus <NUM>.

The tool apparatus <NUM> includes a tool head <NUM> configured to connect to the turbine tension stud <NUM>. The tool head <NUM> may be substantially cylindrical and include a first region having a first diameter and a second region having a second, smaller diameter, creating a lip to enable an actuator <NUM> to engage with the tool head <NUM> and exert a load thereon. The compression body <NUM> is sized to receive at least part of the tool head <NUM> within the axial hole of the compression body <NUM>.

In <FIG>, the tool head <NUM> is not engaged with the tension stud <NUM>. In one example, the tool head <NUM> includes a female threaded connection which is configured to engage with a corresponding male threaded connection on the tension stud <NUM>.

Within the tool apparatus <NUM> there are critical cyclic life components that require monitoring during their repeated use, the female thread of the tool head <NUM> that engages with the tension stud <NUM> is one such component. To minimise the cost of replacing the entire tool head <NUM> once the internal female thread of the tool head <NUM> has worn to an undesirable state, the tool head <NUM> may include a removable insert <NUM> such that the tool head <NUM> is connected to the tension stud <NUM> via the removable insert <NUM>. In one example, the removable insert <NUM> includes a male thread for engaging with a co-operative female thread within the tool head <NUM> and a female thread for engaging with a co-operative male thread of the tension stud <NUM>. The removable insert <NUM> may be economically made from higher grade material compared with the remainder of the tool head <NUM>. Further, the removable insert <NUM> may be changed-out with a spare or replacement removable insert <NUM> whilst the original is away for inspection. This enables continued use of tool apparatus <NUM> whilst the original removable insert <NUM> is being inspected. Further, the removable insert <NUM> may comprise a non-shouldered outer thread, which enables its reversal. As such, the usable life of the removable insert is extended because the redundant thread is utilised.

The tool apparatus <NUM> includes an actuator <NUM> configured to apply a load to the tool head <NUM> and the compression body <NUM>. The actuator <NUM> may have an axial hole therethrough for receiving at least part of the tool head <NUM>.

The tool apparatus <NUM> may include a measurement apparatus <NUM> for measuring the stretch or elongation of the turbine tension stud <NUM>. The measurement apparatus <NUM> will be explained in more detail below.

The rotor assembly <NUM> includes a load retainer <NUM> and a connector <NUM>, which will be explained in more detail below.

<FIG> shows a cross section of a schematic of part of the rotor assembly <NUM> along with the tool assembly <NUM> for applying a load to the turbine tension stud <NUM>. In the example shown in <FIG>, the tool head <NUM> is engaged with the tension stud <NUM> via the replaceable tool insert <NUM> and the safety apparatus <NUM> is shown in a second, open position, wherein the catch <NUM> of the safety apparatus <NUM> is not engaged with the lip <NUM> of the turbine disc <NUM>. In the example shown in <FIG>, the tool head <NUM> is received in the through hole in the compression body <NUM> and the removable insert <NUM> is engaged with the tension stud <NUM>.

<FIG> shows a cross section of a schematic of part of the rotor assembly <NUM> along with the tool assembly <NUM> for applying a load to the turbine tension stud <NUM>. In the example shown in <FIG>, the tool head <NUM> is engaged with the tension stud <NUM> via the replaceable tool insert <NUM> and the safety apparatus <NUM> is shown in a first, containment position, wherein the catch <NUM> of the safety apparatus <NUM> is engaged with the lip <NUM> of the turbine disc <NUM>.

In the arrangement of <FIG>, the actuator <NUM> is engaged with the tool head <NUM> and the compression body <NUM>. In operation, the actuator <NUM> is configured to expand to push against the tool head <NUM> and the compression body <NUM> and exert a load on the tool head <NUM> and the compression body <NUM>. As the compression body <NUM> is engaged with the turbine disc <NUM> of the rotor assembly <NUM>, the force applied to the compression body <NUM> ++& will be reacted by the turbine disc <NUM> and the turbine disc <NUM> will also be subject to compression.

In one example, the actuator <NUM> is a hydraulic load cell to accurately apply a pre-determined load to the tension stud <NUM>. In other examples, the actuator <NUM> may be a pneumatic load cell, a torqued threaded arrangement or an electric solenoid.

Due to the connection between the tool head <NUM> and the tension stud <NUM>, the load applied to the tool head <NUM> results in an extension of the tension stud <NUM> and a tension load to develop in the tension stud <NUM>.

The load applied to the tension stud <NUM> is pre-determined to match the 'steady state' separation loads experienced in operation of the turbine assembly <NUM>. In one example, to determine the tension load applied to the turbine tension stud <NUM>, a change in length or extension of the turbine tension stud <NUM> is measured by a measurement device <NUM>. The measurement device <NUM> may include a sliding plunger that projects through the tool head <NUM> and engages with an end of the turbine tension stud <NUM>. The measurement device <NUM> may have an exposed end that projects from the tool head <NUM>. In one example, the measurement device <NUM> includes a spring to bias the plunger against an end of the turbine tension stud <NUM>. The exposed end of the measurement device <NUM> may be fixed such that the elongation or extension of the tension stud <NUM> may be measured due to the corresponding reduction in length of the measurement device <NUM>.

Due to the stress-strain relationship, a pre-determined tension load can be provided to the tension stud <NUM> by stretching the tension stud <NUM> by a predetermined amount.

Once the turbine tension stud <NUM> has been extended by a pre-determined amount, corresponding to a pre-determined tension load being developed in the turbine tension stud <NUM>, a load retainer <NUM> is moved to engage with the turbine disc <NUM>.

The load retainer <NUM> is moved relative to the turbine tension stud <NUM> to engage with the turbine disc <NUM>. In one example, a connector <NUM>, which may be in the form of a spinner, is connected with the load retainer <NUM> to enable an operator to move the load retainer <NUM> relative to the turbine tension stud <NUM>, without the need for the operator to have direct access to the load retainer <NUM>. In one example, the load retainer <NUM> comprises a threaded nut configured to receive a corresponding thread on the turbine tension stud <NUM>.

In order to access the connector <NUM>, the wall of the compression body <NUM> may include an aperture to enable access to the inside the compression body <NUM>.

Following the engagement of the load retainer <NUM> with the turbine disc <NUM>, the actuator <NUM> may be unloaded. During unloading, the load path between the turbine tension stud <NUM> and the turbine disc <NUM> is changed from passing through the compression body <NUM> to passing through the load retainer <NUM>. In other words, the compression body <NUM> becomes unloaded as the actuator <NUM> is unloaded and the load retainer <NUM> becomes loaded as the actuator <NUM> is unloaded.

Once the actuator <NUM> has been fully unloaded, the tool assembly <NUM> can be removed.

In operation, depending on the size of the rotor assembly <NUM>, the rotor assembly <NUM> may be subject to separation loads of approximately 50kN. In other examples, the separation loads may be more than 250kN, more preferably more than 500kN, more preferably more than 750kN and more preferably more than 1000kN. To compensate against this separation load, the turbine tension stud <NUM> will be subject to a matching tension load. As such, the components of the tool apparatus <NUM> and rotor assembly <NUM> will also be subject to high loads. Whilst the components are designed to withstand the loads applied to them, in practice, there are a number of reasons why failures in the components and/or connections of the rotor assembly <NUM> that are subject to a load may occur.

A first source of potential failure is that one or more threads between connecting elements may fail. For example, the thread between the load retainer <NUM> and the turbine tension stud <NUM> may fail, causing the load energy within the tension stud <NUM> to be released.

Alternatively, the threads between the removable insert <NUM> and either the corresponding thread of the tool head <NUM> or the corresponding thread of the turbine tension stud <NUM> may fail during loading of the turbine tension stud <NUM>, which causes the load energy from the actuator <NUM> to be unrestrained at one end.

In another example, there may be a lack of engagement between the compression body <NUM> and the turbine disc <NUM> or the actuator <NUM> and the tool head <NUM> or the compression body <NUM>.

Further, the load applied by the actuator <NUM> may be too high, or higher than the capacity of one or more of the components and/or connections, resulting in a failure of one or more components and/or connection between components.

In each of these examples, a release of energy occurs, which may cause injury to a nearby operator or damage to nearby equipment. The energy released may be between approximately 1500J to 4000J and so the safety apparatus <NUM> is designed to withstand and contain this release of energy.

<FIG>, <FIG> and <FIG> all show an example of the tool assembly <NUM> including a tool apparatus <NUM> and a safety apparatus <NUM>. In the examples shown in <FIG>, <FIG> and <FIG>, the tool assembly <NUM> includes two safety apparatus <NUM> arranged diametrically opposite on the tool apparatus <NUM>. However, other arrangements of tool assembly <NUM> are possible; for example, the tool assembly <NUM> may have more or fewer than two safety apparatus <NUM>.

The safety apparatus <NUM> or catcher arm is used with the tool apparatus <NUM> to safely apply a tension load to the turbine tension stud <NUM> with a reduced risk of an undesired energy release outside of the tool assembly <NUM> as the safety apparatus <NUM> is configured to contain the load energy released from the tension stud <NUM> due to a failure of one or more components.

Where possible all components of the tool apparatus <NUM> are designed to meet mechanical strength requirements for a given cyclic life with acceptable safe working margins. At a given time during assembly, operators must access the tool assembly <NUM> (i.e. measuring stretch and dismantling tooling). During this time, it is especially essential to provide a second-tier of safety to "fool-proof" against failure scenarios such as accidental over pressure of the actuator and/or damaged or worn threads. This is achieved by the addition of the safety apparatus <NUM> to the tool apparatus <NUM>. In the event of a component failure, the safety apparatus <NUM> are configured to contain to the energy released from the tension stud <NUM> and/or one of the other components subject to loading.

The safety apparatus <NUM> includes a containment member <NUM> which is pivotable about a pivot <NUM>. The pivot <NUM> may be provided by the compression member <NUM>, for example, via the projection of the compression member <NUM>. Alternatively, the pivot <NUM> may be part of the safety apparatus <NUM>. The pivot <NUM> may comprise a retaining bolt configured to be received within a corresponding hole, which enables the containment member <NUM> to pivot about the hole.

In the examples shown in <FIG>, <FIG> and <FIG>, the pivot <NUM> has a pivot housing that is configured to connect to the tool apparatus <NUM>. In one example, the containment member <NUM> is connected to the compression body <NUM> of tool apparatus <NUM>.

The containment member <NUM> includes a retaining arm <NUM> located on a first side of the pivot <NUM>. In one example, the retaining arm <NUM> has a curved or hooked shape such that a first part of the retaining arm <NUM> is at an angle to a second part of the retaining arm.

The safety apparatus <NUM> also includes a catch <NUM> located on the second side of the pivot <NUM>. The catch <NUM> is configured to engage with the lip <NUM> of the disc <NUM> of the rotor assembly <NUM>. In one example, the catch <NUM> is substantially hook shaped to enable it to hook onto the lip or rim <NUM> of the turbine disc <NUM>. The catch <NUM> is shaped such that its shape corresponds with the shape of the lip <NUM> to provide a positive engagement between the catch <NUM> and the lip <NUM>.

The containment member <NUM> is movable about the pivot <NUM> to a first position in which the catch <NUM> is engaged with the lip <NUM> of the disc <NUM> of the rotor assembly <NUM> and a second position in which the catch <NUM> is not engaged with the lip <NUM> of the disc <NUM> of the rotor assembly <NUM>. In the first position, in which the catch <NUM> is engaged with the lip <NUM> of the disc <NUM>, the retaining arm <NUM> is in a containment position such that it will be able to contain any load released from the actuator <NUM> and or tension stud <NUM> as a result of a failure of one or more components and/or connections. In the containment position, the retaining arm <NUM> overlaps with at least part of the tool apparatus <NUM> in the direction of the rotational axis A of the rotor assembly <NUM>, and the catch <NUM> is located on the lip <NUM> of the disc <NUM>. Thus, if the tool head <NUM> is moved away from the disc <NUM>, as a result of a failure and release of energy, then the tool head <NUM> will contact the retaining arm <NUM> of the safety apparatus <NUM>. The retaining arm <NUM> will be subject to a shear force, axial force and bending moment and is sized to withstand these forces. In addition, the connection between the catch <NUM> and the lip <NUM> will also be subject to high forces as a result of a failure and release of energy and the catch <NUM> is sized to withstand these forces.

In one example, the material of the safety apparatus <NUM> is a nickel chromium molybdenum steel, which is preferably due to its high tensile strength and toughness.

The safety apparatus <NUM> may also include a handle <NUM>. A user may operate the handle <NUM> to move the containment member <NUM> between the first position in which the catch <NUM> is engaged with the lip <NUM> of the disc <NUM> of the rotor assembly <NUM> and a second position in which the catch <NUM> is not engaged with the lip <NUM> of the disc <NUM> of the rotor assembly <NUM>.

In one example, the handle <NUM> includes a region <NUM> having cam shaped outer profile at an engagement location with the containment member <NUM>. The handle <NUM> may be connected to the tool apparatus <NUM> via a second pivot <NUM>. In one example, the handle <NUM> is connected to the compression body <NUM> of the tool apparatus <NUM> and the containment member <NUM> is located between the second pivot <NUM> and the compression body <NUM> and the cam shaped outer profile of the handle <NUM> is engaged with the containment member <NUM>. As such, when the handle <NUM> is moved about the second pivot <NUM>, the containment member <NUM> will be moved about the first pivot <NUM> due to the shape of the cam shaped outer profile. As such, movement of the handle <NUM> will result in the containment member <NUM> being moved between a first, containment position and a second, open position.

In one example, the containment member <NUM> includes an elongate region defining a longitudinal axis. In one example, the catch <NUM> is located at a proximal end of the elongate region and the retaining arm <NUM> is located at the distal end of the elongate region. The catch <NUM> and the retaining arm <NUM> may project away from the longitudinal axis of the elongate region in substantially the same direction. In one example, at least part of the retaining arm <NUM> defines a second axis. The longitudinal axis defined by the elongate region and the second axis defined by the retaining arm <NUM> may be substantially perpendicular.

In one example, the containment member <NUM> has a substantially rectangular shaped cross section, but any suitable cross section may be used.

The catch <NUM> and retaining arm <NUM> may be part of the same component or, alternatively, they may be distinct components that are joined together.

Where the tool assembly <NUM> comprises a first safety apparatus <NUM> and a second safety apparatus <NUM>, as shown, the retaining arm <NUM> of a first safety apparatus <NUM> may project towards the retaining arm <NUM> of the second safety apparatus <NUM> and the retaining arm <NUM> of the second safety apparatus <NUM> may project towards the retaining arm <NUM> of the first safety apparatus <NUM>. Put another way, retaining arms <NUM> of different safety apparatus <NUM> may project towards each other in the tool assembly <NUM>.

The containment member <NUM> is configured to pivot about a pivot location <NUM> between a first position in which the catch <NUM> is engaged with the lip <NUM> of the disc <NUM> and the retaining arm <NUM> is in a containment position for containing a load applied to a turbine tension stud <NUM> of a rotor assembly <NUM>, as shown in <FIG>, and a second, position in which the catch <NUM> is disengaged with the lip <NUM> of the disc <NUM> and the retaining arm <NUM> is in a non-containment position, as shown in <FIG> and <FIG>. In the containment position, at least part of the retaining arm <NUM> overlaps with at least part of the tool apparatus <NUM>, such as the tool head <NUM>, in the direction of the rotational axis A of the rotor assemble <NUM>. In addition, the catch <NUM> is engaged with the lip <NUM> of the disc <NUM>. In the containment position, the safety apparatus <NUM> is configured to contain the load within the tension stud <NUM>. When the containment member <NUM> is in the second, non-containing position, the containment member <NUM> is not configured to contain loads therein.

The tool assembly <NUM> may include a biasing member <NUM>, such as a pre-loaded spring, configured to bias the containment member <NUM> in the second position.

The containment member <NUM> is sized such that it can withstand the various loads resulting from a failure and release of energy of one or more components of the tool apparatus <NUM> and/or rotor assembly <NUM> whilst the load is being applied to the tension stud <NUM> or after the load has been applied to the tension stud <NUM>.

The safety apparatus <NUM> of the tool assembly <NUM> may be configured to operate with different compressor/turbine arrangements. <FIG> shows an example of the tool assembly <NUM> and a part of a power turbine <NUM>. In the example shown in <FIG>, the power turbine <NUM> includes a plurality of turbine discs <NUM>, the outer most of which includes a lip or rim <NUM> on which the catch <NUM> of the safety apparatus <NUM> may engage. The tool assembly <NUM> may be used to safely apply a tension load to a power turbine tension stud <NUM> in the same manner as applying a load to the turbine tension stud <NUM> of a turbine compressor. The operation of the tool assembly <NUM> is as described above.

<FIG> shows an illustration of a method of applying a load to a tension stud <NUM> of a rotor assembly.

In step <NUM>, the tool assembly <NUM> is connected with the tension stud <NUM>. In one example, the tool head <NUM> is used to connect the tool assembly <NUM> to the tension stud.

In one example, the tool head <NUM> includes a removable insert <NUM> comprising a hollow cylinder in which both the outside face and the inside face of the hollow cylinder are threaded. The thread on the outer face of the removable insert <NUM> may connect with a corresponding thread of a cavity within the tool head <NUM> for receiving the removable insert <NUM>. The thread on the internal face of the removable insert <NUM> may connect with a corresponding thread on the tension stud <NUM>.

In step <NUM>, the compression body <NUM> of the tool assembly <NUM> is engaged with the disc <NUM>, <NUM> of the rotor assembly <NUM>, <NUM>. The compression body <NUM> may have one end that is shaped to match a corresponding profile on the disc <NUM>, <NUM> such that a positive engagement occurs.

In step <NUM>, the catch <NUM> of the safety apparatus <NUM> is engaged with the lip of the disc <NUM>, <NUM> of the rotor assembly <NUM>, <NUM>. In one example, catch <NUM> may be moved into engagement by moving the handle <NUM>. As the retaining member <NUM> is fixed relative to the catch <NUM>, the retaining arm <NUM> is moved into the containment position as the catch <NUM> is engaged with the lip <NUM>, <NUM>.

In step <NUM>, the actuator <NUM> is actuated to apply a load to the tool head <NUM> and the compression body <NUM> to cause a tension load to develop in the tension stud <NUM>, <NUM>.

In a further step, the method may include measuring the elongation of the tension stud <NUM>, <NUM> via measurement apparatus <NUM>. The method may further include determining that the tension stud <NUM>, <NUM> has elongated by a predetermined amount and rotating the load retainer <NUM> which is co-operatively threaded to the tension stud <NUM>, <NUM>. The load retainer <NUM> is moved so that it engages with the shaft <NUM>, <NUM> of the rotor assembly <NUM>, <NUM>.

Each feature disclosed in this specification (including any accompanying abstract and drawings) may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise.

Claim 1:
A tool assembly (<NUM>) for applying a load to a tension stud (<NUM>, <NUM>) of a rotor assembly (<NUM>, <NUM>) for a gas turbine, the tool assembly (<NUM>) comprising:
at least one safety apparatus (<NUM>) for containing a release of energy from a tension stud (<NUM>, <NUM>) of a rotor assembly (<NUM>, <NUM>) for a gas turbine, the safety apparatus (<NUM>) is characterised by comprising:
a containment member (<NUM>) configured to pivot about a pivot location (<NUM>),
the containment member (<NUM>) comprising:
a retaining arm (<NUM>) located on a first side of the pivot location (<NUM>); and
a catch (<NUM>) located on a second side of the pivot location (<NUM>), wherein the containment member (<NUM>) is movable about the pivot location (<NUM>) to a first position in which the catch (<NUM>) is engaged with a lip (<NUM>, <NUM>) of a disc (<NUM>, <NUM>) of the rotor assembly (<NUM>, <NUM>) to position the retaining arm (<NUM>) in a containment position; and
a tool apparatus (<NUM>) comprising:
a tool head (<NUM>) for connecting to the tension stud (<NUM>, <NUM>);
a compression body (<NUM>) for engaging with a disc (<NUM>, <NUM>) of the rotor assembly (<NUM>, <NUM>); and
an actuator (<NUM>) for applying a load to the tool head (<NUM>) and the compression body (<NUM>),
wherein the at least one safety apparatus (<NUM>) is connected to the tool apparatus (<NUM>) via the pivot (<NUM>).