Patent Publication Number: US-2020291752-A1

Title: Safety Apparatus for an Actuator

Description:
FIELD 
     This relates to a safety apparatus for an actuator. 
     BACKGROUND 
     Actuators are used in a vast array of applications and environments. In the oil and gas exploration and production industry, for example, actuators are used in numerous applications in order to control equipment and often form key components in the safety and operational systems of an oil and gas installation. 
     Actuators used in oil and gas installations are subject to a number of significant challenges. For example, actuators used in both offshore and onshore oil and gas installations may be exposed to extremes of temperature, while offshore installations are also subject to the corrosive effects from the marine environment. As such, it is important that actuators used in such environments are subject to regular inspection, repair and maintenance regimes in order to avoid or at least reduce the incidence of actuator failure. Even where such inspection, repair and maintenance regimes are carried out on a regular basis, however, actuator failure remains a risk. 
     It will be recognised that many actuators used in oil and gas installations are large constructions with high load capacity, such that actuator failure results in a significant release of stored energy. 
     In one failure mode, the failure of an actuator may result in axial ejection of one or more actuator component, such as the actuator spring, end cap bolts, end caps and/or tie rod. In another failure mode, the failure of an actuator may result in lateral, e.g. radial, ejection of one or more actuator component. 
     While any actuator failure poses a risk, the proximity of actuators to personnel working areas means that actuator failure represents a significant risk to personnel and other equipment. 
     An additional challenge posed by oil and gas installations towards the end of their operational life and/or which are in the process of being decommissioned is that repair and/or replacement of a given actuator may be impractical or uneconomical. Nevertheless, there remains a need to reduce the risk posed by failure of such actuators. 
     SUMMARY 
     According to a first aspect, there is provided a safety apparatus for an actuator, comprising: 
     a housing arrangement configured for location on an actuator, the housing arrangement comprising an outer housing comprising a base portion and a wall portion extending from the base portion, the housing arrangement defining an enclosure for encompassing an end portion of the actuator and configured to form a barrier for containing one or more component of the actuator and/or release of stored energy in the event of actuator failure. 
     Beneficially, embodiments of the safety apparatus reduce the risk to personnel and equipment which may otherwise result from the ejection of components and/or release of stored energy caused by actuator failure. This is achieved by providing a safety apparatus configured to contain one or more component of the actuator in the event of actuator failure, such that ejection of the one or more component may be prevented. 
     The housing arrangement may be modular in construction. 
     The outer housing may comprise or take the form of a bag. 
     The outer housing may comprise and/or may be at least partially constructed from a fabric material. 
     Beneficially, an outer housing which comprises and/or is at least partially constructed from a fabric material provides a safety apparatus which is flexible and/or lightweight. It is envisaged, for example, that the outer housing may be configured for location in an offshore kit bag or like container, permitting transport of the safety apparatus by helicopter or other conventional means; obviating the requirement for specialist transport at significant expense and which typically has limited availability. 
     The outer housing may be reconfigurable between a first configuration and a second, larger, configuration. The first configuration may define a storage configuration. The second configuration may define a deployment configuration suitable for locating the outer housing on the actuator. 
     The outer housing may comprise and/or may be at least partially constructed from a synthetic fibre material. 
     The outer housing may comprise and/or may be at least partially constructed from an aramid material. 
     The outer housing may comprise and/or may be at least partially constructed from a para-aramid material. 
     The outer housing may comprise and/or may be at least partially constructed from Kevlar® or like material. 
     Beneficially, an outer housing constructed from a para-aramid material, such as Kevlar® or like material, provides a barrier capable of containing one or more components of the actuator ejected in the event of actuator failure. 
     The outer housing may comprise and/or may be at least partially constructed from Twaron® or like material. 
     Beneficially, an outer housing constructed from Twaron® or like material provides a barrier capable of containing one or more components of the actuator ejected in the event of actuator failure. An outer housing constructed from a para-aramid material, such as Twaron® or like material, also provides an outer housing which is thermally stable and resistant to chemical attack, and which is thus suited to the harsh environment of an oil and gas installation. 
     The outer housing may comprise and/or may be at least partially constructed from a meta-aramid material. 
     The outer housing may comprise and/or may be at least partially constructed from Nomex® or like material. 
     Beneficially, an outer housing constructed from a meta-aramid material, such as Nomex® or like material, provides a barrier capable of containing one or more components of the actuator ejected in the event of actuator failure. An outer housing constructed from a meta-aramid material, such as Nomex® or like material, also provides an outer housing which is fire resistant, and which is thus suited to the harsh environment of an oil and gas installation. 
     The outer housing may comprise and/or may be at least partially constructed from a composite material, such as glass fibre composite or carbon fibre composite, and/or a polymeric material, such as Polyether Ether Ketone (PEEK). 
     Beneficially, an outer housing constructed from a composite material, such as glass fibre composite or carbon fibre composite, and/or a polymeric material, such as Polyether Ether Ketone (PEEK) may provide a rigid outer housing. 
     The outer housing may be configured to resist an impact force. For example, the outer housing may comprise and/or may be at least partially constructed from an impact resistant material, such as a rubber material, a foam material or the like. In particular, but not exclusively, the outer housing may comprise a vinyl nitrile polymer foam compound material or like material. 
     The outer housing may comprise a unitary construction. For example, the outer housing may be constructed as a moulded component or a continuously wound component. 
     Alternatively, the outer housing may comprise a modular construction. 
     The outer housing may comprise a plurality of layers of material, such as the materials described above. 
     The safety apparatus may comprise a plurality of the outer housings. For example, the safety apparatus may comprise a first outer housing for location about a first end portion of the actuator and a second outer housing for location about a second end portion of the actuator. 
     The housing arrangement may comprise an inner housing. 
     In use, the inner housing may form an armour layer of the safety apparatus. 
     The inner housing may be configured for location within the outer housing. 
     The inner housing may be offset from the outer housing so as to define a cavity therebetween. 
     The inner housing and the outer housing may be dimensioned so that the cavity may house an indicator arrangement, as will be described further below. 
     The inner housing may comprise a base portion. 
     The inner housing may comprise a wall portion. 
     The wall portion of the inner housing may extend from the base portion of the inner housing. 
     The inner housing may comprise or take the form of a bag. 
     The inner housing may comprise and/or may be at least partially constructed from a fabric material. 
     Beneficially, an inner housing which comprises and/or is at least partially constructed from a fabric material provides an safety apparatus which is flexible and/or lightweight. It is envisaged, for example, that the inner housing may be configured for location in an offshore kit bag or like container, permitting transport of the safety apparatus by helicopter or other conventional means; obviating the requirement for specialist transport at significant expense and which typically has limited availability. 
     The inner housing may be reconfigurable between a first configuration and a second, larger, configuration. The first configuration may define a storage configuration. The second configuration may define a deployment configuration suitable for locating the inner housing on the actuator. 
     The inner housing may comprise and/or may be at least partially constructed from a synthetic fibre material. 
     The inner housing may comprise and/or may be at least partially constructed from an aramid material. 
     The inner housing may comprise and/or may be at least partially constructed from a para-aramid material. 
     The inner housing may comprise and/or may be at least partially constructed from Kevlar® or like material. 
     Beneficially, an inner housing constructed from a para-aramid material, such as Kevlar® or like material, provides a barrier capable of containing one or more components of the actuator ejected in the event of actuator failure. 
     The inner housing may comprise and/or may be at least partially constructed from Twaron® or like material. 
     Beneficially, an inner housing constructed from a para-aramid material, such as Twaron® or like material, provides a barrier capable of containing one or more components of the actuator ejected in the event of actuator failure. An inner housing constructed from a para-aramid material, such as Twaron® or like material, also provides a housing which is thermally stable and resistant to chemical attack, and which is thus suited to the harsh environment of an oil and gas installation. 
     The inner housing may comprise and/or may be at least partially constructed from a meta-aramid material. 
     The inner housing may comprise and/or may be at least partially constructed from Nomex® or like material. 
     Beneficially, an inner housing constructed from a meta-aramid material, such as Nomex® or like material, provides a barrier capable of containing one or more components of the actuator ejected in the event of actuator failure. An inner housing constructed from a meta-aramid material, such as Nomex® or like material, also provides a housing which is fire resistant, and which is thus suited to the harsh environment of an oil and gas installation. 
     The inner housing may comprise and/or may be at least partially constructed from a composite material, such as glass fibre composite or carbon fibre composite; and/or a polymeric material, such as Polyether Ether Ketone (PEEK). 
     Beneficially, an inner housing constructed from a composite material, such as glass fibre composite or carbon fibre composite; and/or a polymeric material, such as Polyether Ether Ketone (PEEK) may provide a rigid inner housing. 
     The inner housing may comprise a unitary construction. For example, the inner housing may be constructed as a moulded component or a continuously wound component. 
     Alternatively, the inner housing may comprise a modular construction. 
     The inner housing may comprise a plurality of layers of material, such as the materials described above. 
     Where the safety apparatus comprises a plurality of the outer housings, the safety apparatus may comprise a plurality of the inner housings. 
     For example, the safety apparatus may comprise a first inner housing for location within the first outer housing and a second inner housing for location in the second outer housing. 
     The safety apparatus may comprise an indicator arrangement. 
     The indicator arrangement may form part of the housing arrangement. 
     The indicator arrangement may be configured to provide an indication that failure of the actuator has occurred. 
     The indicator arrangement may be interposed between the inner housing and the outer housing, for example in the cavity between the inner housing and the outer housing. 
     The indicator arrangement may be configured for location around the inner housing. 
     The indicator arrangement may be configured for location within the outer housing. 
     The indicator arrangement may comprise a visual indicator, such as a dye. 
     The visual indicator, e.g. dye, may be contained within an indicator housing. 
     Beneficially, the provision of an indicator housing permits the visual indicator to be securely stored. 
     The indicator housing may comprise or take the form of a bag. 
     Alternatively, the indicator housing may comprise or take the form of a sponge, a gel or other material suitable for storing the visual indicator. 
     The indicator housing may be configured to release the dye in the event of failure of the actuator. 
     The indicator housing may be configured to puncture or otherwise release the visual indicator when subjected to a force reaching a selected threshold force. 
     The selected threshold force may be selected to be of a magnitude greater than that experienced by the safety apparatus in normal operation. This ensures that the indicator arrangement does not prematurely activate, for example due to expansion and compression resulting from fluctuations in temperature or other environmental forces on the safety apparatus and/or an external impact on the safety apparatus. 
     The selected threshold force may be of a magnitude greater than or equal to an impact force on the inner housing resulting from ejection of the one or more component of the actuator during failure and/or resulting from the direct impact of the ejected component on the indicator housing itself. 
     In use, release of the visual indicator may be determined externally of the actuator, for example by personnel or by remote monitoring system, such as CCTV. 
     The outer housing may be configured to absorb the visual indicator, such that the visual indicator bleeds through to an external surface of the outer housing. 
     Alternatively or additionally, the outer housing may comprise a weep hole to permit the visual indicator to pass to an exterior of the safety apparatus. 
     The indicator housing may comprise a base portion. 
     The indicator housing may comprise a wall portion. 
     The wall portion of the indicator housing may extend from the base portion. 
     The indicator housing may comprise a unitary component. For example, the indicator housing may define a single envelope for receiving the visual indicator. 
     Alternatively, the indicator housing may comprise a plurality of housing portions. The indicator housing may, for example, comprise a first housing portion for containing a first visual indicator and a second housing portion for containing a second visual indicator. The second visual indicator may be different to the first visual indicator. For example, the second visual indicator may be a different colour to the first visual indicator. 
     Beneficially, the use of different visual indicators may permit an operator to determine the likely cause of the actuator failure from the colour of the visual indicator. 
     Where the safety apparatus comprises a plurality of the outer housings, the indicator arrangement may comprise a plurality of the indicator housings. For example, the safety apparatus may comprise a first indicator housing for location between the first outer housing and the first inner housing and a second indicator housing for location between the second outer housing and the second inner housing. 
     The indicator arrangement may comprise a label indicating that failure has occurred. 
     The indicator arrangement may comprise a status indicator. 
     The status indicator may be reconfigurable from a first configuration to a second configuration. The status indicator in the second configuration indicating that failure of the actuator has occurred. 
     The status indicator may comprise an indicator strip or streamer. The indicator strip may be coloured, e.g. red, to as to indicate the status of the safety apparatus. 
     The status indicator may be configured such the indicator strip is covered in the first configuration, reconfiguration of the status indicator from the first configuration to the second configuration uncovering the indicator strip. 
     The status indicator may be reconfigurable from the first configuration to the second configuration in response to force exceeding a threshold force, for example the selected threshold force at which the indicator housing is configured to puncture or otherwise release the visual indicator. The threshold force may comprise an axial force applied to the status indicator. 
     The status indicator may, for example, comprise and/or take the form of a piece of material. The piece of material may comprise portions folded, sewn or otherwise arranged to cover the indicator strip in the first configuration. 
     Alternatively or additionally, the status indicator may be deformable member reconfigurable from the first configuration to the second configuration. 
     The status indicator may be provided in combination with the label to indicate the status of the safety apparatus. 
     The safety apparatus may comprise a securement arrangement. 
     The securement arrangement may be configured to retain the housing arrangement on the actuator. 
     The securement arrangement may be configured for location around the housing arrangement, in particular around the outer housing. 
     The securement arrangement may comprise at least one strap. 
     The securement arrangement may comprise a plurality of straps. 
     The strap, or at least one of the straps, may comprise and/or may be at least partially constructed from a synthetic fibre material. 
     The strap, or at least one of the straps, may comprise and/or may be at least partially constructed from a polyethylene material or like material, for example an Ultra-High Molecular Weight Polyethylene (UHMwPE), such as Dyneema® or like material. 
     Alternatively or additionally, the strap, or at least one of the straps, may comprise and/or may be at least partially constructed from polyester or like material. 
     Alternatively or additionally, the strap, or at least one of the straps, may comprise and/or may be at least partially constructed from an aramid material, for example: 
     a para-aramid material such as Kevlar®, Twaron® or like material; and/or 
     a meta-aramid material, such as Nomex® or like material. 
     The label may be provided on the securement arrangement of the safety apparatus. For example, the label may be provided on one or more strap of the securement arrangement. 
     The status indicator may be provided on the securement arrangement of the safety apparatus. For example, the status indicator may be provided on one or more strap of the securement arrangement. 
     The securement arrangement may be coupled to the outer housing. 
     The securement arrangement may further comprise one or more guide. 
     The guides may be disposed at the interfaces between the straps to assist in installation and to ensure that the straps remain in position once installed. 
     The securement arrangement may further comprise one or more profiled edge piece. 
     The edge pieces may be provided on the outer housing, the edge pieces disposed at the interface between the base portion and the wall portion of the outer housing. 
     Beneficially, the edge pieces guide the straps around the interface between the base portion and the wall portion of the outer housing while avoiding sharp edges. 
     The securement arrangement may comprise a fastener for securing the strap. 
     The fastener may comprise a ratchet fastener. 
     Where the safety apparatus comprises a plurality of outer housings, the securement arrangement may be disposed about both the first outer housing and the second outer housing and configured to secure the first outer housing the second outer housing together. 
     Beneficially, by virtue of its location on the first end portion of the actuator the first outer housing may assist in retaining the second outer housing in the event of failure of the actuator, and vice-versa. 
     The safety apparatus may comprise one or more protective layer. 
     The protective layer, or where the apparatus comprises a plurality of protective layers at least one of the layers, may comprise a nylon material or like material. 
     The protective layer, or where the apparatus comprises a plurality of protective layers at least one of the protective layers, may comprise a waterproof layer. 
     Alternatively or additionally, the protective layer, or where the apparatus comprises a plurality of protective layers at least one of the protective layers may provide protection against UV degradation. 
     One or more protective layer may be disposed in, on and/or around the outer housing. 
     For example, one or more protective layer may be disposed on an exterior of the outer housing. The protective layer disposed on an exterior of the outer housing may comprise and/or may be at least partially constructed from a nylon woven material coated in polyurethane, or like material. 
     Alternatively or additionally, one or more protective layer may be disposed on an interior of the outer housing, such as between the inner housing and the outer housing. 
     The protective layer disposed on an exterior of the outer housing may comprise and/or may be at least partially constructed from a PVC material or like material At least one protective layer may comprise a base portion and a wall portion, the wall portion extending from the base portion. 
     The safety apparatus may be provided in combination with the actuator. 
     According to a second aspect, there is provided an actuator assembly comprising: 
     the safety apparatus of the first aspect; and 
     an actuator. 
     According to a third aspect, there is provided a kit of parts comprising: 
     an outer housing comprising a base portion and a wall portion extending from the base portion; 
     an inner housing; and 
     an indicator arrangement, 
     the outer housing, the inner housing and the indicator arrangement forming or forming part of a housing arrangement configured for location on an actuator, the housing arrangement defining an enclosure for encompassing an end portion of the actuator and configured to form a barrier for containing one or more component of the actuator in the event of actuator failure. 
     The kit may comprise a plurality of the outer housings. For example, the kit may comprise a first outer housing for location about a first end portion of the actuator and a second outer housing for location about a second end portion of the actuator. 
     In such embodiments, the securement arrangement may be disposed about both the first outer housing and the second outer housing and configured to secure the first outer housing the second outer housing together. 
     Where the kit comprises a plurality of the outer housings, the safety apparatus may further comprise a plurality of the inner housings. For example, the kit may comprise a first inner housing for location within the first outer housing and a second inner housing for location in the second outer housing. 
     Where the kit comprises a plurality of the outer housings, the indicator arrangement may comprise a plurality of the indicator housings. For example, the kit may comprise a first indicator housing for location between the first outer housing and the first inner housing and a second indicator housing for location between the second outer housing and the second inner housing. 
     A fourth aspect relates to use of the safety apparatus according to the first aspect to resist ejection of one or more component of the actuator in the event of actuator failure. 
     The features defined above or below may be utilised, either alone or in combination with any other defined feature. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a perspective view of a safety apparatus; 
         FIG. 2  shows a part cutaway view of the safety apparatus shown in  FIG. 1 ; 
         FIG. 3  shows an enlarged sectional view showing a housing arrangement of the safety apparatus shown in  FIG. 1 ; 
         FIG. 4  shows an enlarged sectional view of a second housing arrangement of the safety apparatus shown in  FIG. 1 ; 
         FIG. 5  shows an enlarged bottom view of part of the housing arrangement shown in  FIG. 3 ; 
         FIG. 6  shows an enlarged bottom view of part of the second housing arrangement shown in  FIG. 4 ; 
         FIG. 7  shows an enlarged view of a status indicator of the safety apparatus shown in  FIG. 1 , in a first configuration; 
         FIG. 8  shows an enlarged view of the status indicator shown in  FIG. 7 , in a second configuration; 
         FIG. 9  show an enlarged view of part of a securement arrangement of the safety apparatus shown in  FIG. 1 ; 
         FIG. 10  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 1 ; 
         FIG. 11  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 1 ; 
         FIG. 12  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 1 ; 
         FIG. 13  shows a perspective view of an alternative safety apparatus; 
         FIG. 14  shows a part cutaway view of the safety apparatus shown in  FIG. 13 ; 
         FIG. 15  shows an enlarged sectional view showing a housing arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 16  shows an enlarged sectional view of a second housing arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 17  shows an enlarged bottom view of part of the housing arrangement shown in  FIG. 15 ; 
         FIG. 18  shows an enlarged bottom view of part of the second housing arrangement shown in  FIG. 16 ; 
         FIG. 19  shows an enlarged view of a status indicator of the safety apparatus shown in  FIG. 13 , in a first configuration; 
         FIG. 20  shows an enlarged view of the status indicator shown in  FIG. 19 , in a second configuration; 
         FIG. 21  show an enlarged view of part of a securement arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 22  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 23  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 24  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 25  shows a perspective part cutaway view of a further alternative safety apparatus; 
         FIG. 26  shows an enlarged sectional view of a housing arrangement of the safety apparatus shown in  FIG. 25 ; 
         FIG. 27  show an enlarged view of part of a securement arrangement of the safety apparatus shown in  FIG. 13 ; 
         FIG. 28  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 25 ; 
         FIG. 29  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 25 ; and 
         FIG. 30  shows an enlarged view of another part of the securement arrangement of the safety apparatus shown in  FIG. 25 . 
     
    
    
     DETAILED DESCRIPTION OF THE DRAWINGS 
       FIGS. 1 and 2  of the accompanying drawings shows a perspective view of a safety apparatus  10  for an actuator  12 . 
     In use, the safety apparatus  10  is locatable on the actuator  12  and is configured to form a barrier for containing one or more component of the actuator  12  ejected in the event of actuator failure. 
     The safety apparatus  10  has a housing arrangement including an outer housing  14 , the outer housing  14  encompassing an end portion  16  of the actuator  12 . 
     In the illustrated safety apparatus  10  shown in  FIGS. 1 and 2 , the outer housing  14  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an outer housing  14  capable of containing the energy of the ejected components and other contained energy, reducing the risk to personnel and other equipment. 
     As shown in  FIG. 3 , the outer housing  14  has a solid base portion  18  and a wall portion  20  extending from the base portion  18 , the base portion  18  and the wall portion  20  defining an enclosure for encompassing the end portion  16  of the actuator  12 . Beneficially, the base portion  18  and the wall portion  20  form an outer housing  14  which is capable of containing components ejected both axially and laterally from the actuator  12  in the event of failure. As shown, the outer housing  14  is generally cylindrical in shape. However, it will be recognised that the outer housing  14  may define any suitable shape. 
     A protective layer  19  is disposed on an exterior of the outer housing  14 . The protective layer  19  is formed from a nylon woven material coated in polyurethane. The protective layer  19  is generally cylindrical in shape. However, it will be recognised that the protective layer  19  may define any suitable shape. 
     A further protective layer  21  is disposed on an interior of the outer housing  14 . The protective layer  21  is formed from PVC. The protective layer  21  is generally cylindrical in shape. However, it will be recognised that the protective layer  21  may define any suitable shape. 
     The housing arrangement of the safety apparatus  10  further comprises an inner housing  22 . In use, the inner housing  22  defines an armour layer of the safety apparatus  10 . The inner housing  22  is disposed within the outer housing  14  and is configured for location about the end portion  16  of the actuator  12 . 
     In the illustrated safety apparatus  10 , the inner housing  22  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an inner housing  22  capable of containing the energy of the ejected components, reducing the risk to personnel and other equipment. 
     As shown in  FIG. 3 , the inner housing  22  has a solid base portion  24  and a wall portion  26  extending from the base portion  24 . Beneficially, the provision of outer housing  14  and inner housing  22  provides additional resistance to ejection of components of the actuator  12  in the event of failure. 
     The inner housing  22  is offset from the outer housing  14 , such that the inner housing  22  and the outer housing  14  together define a cavity  28  for receiving an indicator arrangement  30 , the indicator arrangement  30  forming part of the housing arrangement of the safety apparatus  10 . 
     The indicator arrangement  30  is configured to provide a visual indication that failure of the actuator  12  has occurred, and comprises a visual indicator in the form of a coloured dye  32 . In the illustrated safety apparatus  10 , the dye  32  is a red in colour. However, it will be recognised that the dye  32  may be any suitable colour. 
     As shown in  FIG. 3 , the dye  32  is contained within an indicator housing  34 , the indicator housing  34  configured to puncture or otherwise release the dye  32  to indicate when failure of the actuator  12  has occurred. Release of the dye  32  may be determined externally of the actuator  12 , for example by personnel or by remote monitoring system, such as a CCTV system. The indicator housing  34  is interposed between the inner housing  22  and the outer housing  14 , and comprises a solid base portion  36  and a wall portion  38  extending from the base portion  36 , the base portion  36  and wall portion  38  defining a cavity for receiving the dye  32 . 
     As shown in  FIGS. 1 and 2 , and referring also to  FIG. 4  of the accompanying drawings, the safety apparatus  10  further comprises a second outer housing  14   a , the outer housing  14   a  encompassing an end portion  16   a  of the actuator  12 . 
     As shown in  FIG. 4 , the outer housing  14   a  is substantially identical to the outer housing  14 , having a solid base portion  18   a  and a wall portion  20   a  extending from the base portion  18   a , the base portion  18   a  and the wall portion  20   a  defining an enclosure for encompassing the end portion  16   a  of the actuator  12 . The base portion  18   a  and the wall portion  20   a  form an outer housing  14   a  which is capable of containing components ejected both axially and laterally from the actuator  12  in the event of failure. The outer housing  14   a  is generally cylindrical in shape. However, it will be recognised that the outer housing  14   a  may define any suitable shape. 
     The outer housing  14   a  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an outer housing  14   a  capable of containing the energy of the ejected components, and reducing the risk to personnel and other equipment. 
     The safety apparatus  10  further comprises an inner housing  22   a , the inner housing  22   a  disposed within the outer housing  14   a  and configured for location about the end portion  16   a  of the actuator  12 . In use, the inner housing  22   a  defines an armour layer of the safety apparatus  10 . 
     As shown in  FIG. 4 , the inner housing  22   a  has a solid base portion  24   a  and a wall portion  26   a  extending from the base portion  24   a . Beneficially, the provision of outer housing  14   a  and inner housing  22   a  provides additional resistance to ejection of components of the actuator  12  in the event of failure. 
     A protective layer  19   a  is disposed on an exterior of the outer housing  14   a . The protective layer  19   a  is formed from a nylon woven material coated in polyurethane. The protective layer  19   a  is generally cylindrical in shape. However, it will be recognised that the protective layer  19   a  may define any suitable shape. 
     A further protective layer  21   a  is disposed on an interior of the outer housing  14   a . The protective layer  21   a  is formed from PVC. The protective layer  21   a  is generally cylindrical in shape. However, it will be recognised that the protective layer  21   a  may define any suitable shape. 
     The inner housing  22   a  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an inner housing  22   a  capable of containing the energy of the ejected components, and reducing the risk to personnel and other equipment. 
     The inner housing  22   a  is offset from the outer housing  14   a , such that the inner housing  22   a  and the outer housing  14   a  together define a cavity  28   a  for receiving an indicator arrangement  30   a.    
     The indicator arrangement  30   a  is configured to provide a visual indication that failure of the actuator  12  has occurred, and comprises a visual indicator in the form of a coloured dye  32   a . In the illustrated safety apparatus  10 , the dye  32   a  is a red in colour. However, it will be recognised that the dye  32   a  may be any suitable colour. 
     As shown in  FIG. 4 , the dye  32   a  is contained within an indicator housing  34   a , the indicator housing  34   a  configured to puncture or otherwise release the dye  32   a  to indicate when failure of the actuator  12  has occurred. Release of the dye  32   a  may be determined externally of the actuator  12 , for example by personnel or by remote monitoring system, such as a CCTV system. The indicator housing  34   a  is interposed between the inner housing  22   a  and the outer housing  14   a , and comprises a solid base portion  36   a  and a wall portion  38   a  extending from the base portion  36   a , the base portion  36   a  and wall portion  38   a  defining a cavity for receiving the dye  32   a.    
     As shown in  FIGS. 5 and 6 , in the safety apparatus  10  the outer housings  14 , 14   a  each comprise a weep hole  39 , 39   a  for permitting the dye  32 , 32   a  to escape, and thus indicate that the actuator  12  has failed. However, it will be recognised that in other arrangements the safety apparatus may not have a weep hole  39 , 39   a.    
     As shown in  FIG. 1  and referring now also to  FIGS. 7 and 8  of the accompanying drawings, the indicator arrangement  30   a  further comprises a label  40   a  and a safety indicator in the form of indicator strip  40   b . The indicator strip  40   b  comprises a piece of material which is folded and/or sown together to form a seam. In use, when exposed to an axial load the seam bursts, thereby exposing the indicator strip  40   b.    
     As shown in  FIGS. 1 and 2 , the safety apparatus  10  has a securement arrangement—shown generally by  42 —configured to retain the outer housings  14 , 14   a  on the actuator  12 . 
     The securement arrangement  42  is configured for location around the housings  14 , 14   a  and comprises a plurality of straps  44 . In the safety apparatus  10 , the straps  44  are constructed from an Ultra-High Molecular Weight Polyethylene (UHMwPE), material, e.g. Dyneema®. 
     Referring now also to  FIGS. 9, 10, 11 and 12  of the accompanying drawings, there are shown enlarged views of parts of the safety apparatus  10 . 
     As shown in  FIG. 9 , the securement arrangement  42  further comprises guides  46 , the guides  46  provided on the housings  14 , 14   a , respectively. The guides  46  are disposed at the interfaces between the straps  44  to assist in installation and to ensure that the straps  44  remain in position once installed. 
     As shown in  FIG. 10 , the securement arrangement  42  further comprises profiled edge pieces  48 , the edge pieces  48  provided on the housing  14 , 14   a , respectively. The edge pieces  48  are disposed at the interface between the base portion  18  and the wall portion  20  and at the interface between the base portion  18   a  and the wall portion  20   a . The edge pieces  48  guide the straps  44  around the interface between the base portions  18 , 18   a  and the wall portions  20 , 20   a  while avoiding sharp edges. 
     As shown in  FIG. 11 , the securement arrangement  42  further comprises buckles  49 . 
     As shown in  FIG. 12 , the securement arrangement  42  further comprises fasteners  50 , the fasteners  50  in the safety apparatus  10  comprising ratchet fasteners, buckle or similar appropriate joining arrangement. 
     The safety apparatus  10  provide a number of benefits. For example, the safety apparatus  10  is passive, that is the safety apparatus  10  has no actuation mechanism and/or does not require power to operate. Beneficially, the provision of a passive safety apparatus eliminates or at least reduces the risk posed by the release of stored energy and/or ejection of components resulting from failure on all actuators, including those which are not subject to regular inspection and/or which are located on oil and gas installations which are in the process of being decommissioned and for which repair and replacement of the actuator is impractical or uneconomical. 
     It will be recognised that the safety apparatus described above is merely exemplary and that various modifications may be made. 
     For example, reference is now made to  FIGS. 13 to 24  of the accompanying drawings which shows an alternative safety apparatus  110 . The safety apparatus  110  is similar to the safety apparatus  10  and like components are represented by like numerals incremented by 100. However, whereas in the safety apparatus  10  the outer housings  14 , 14   a  are constructed from a para-aramid material, in the safety apparatus  110  the outer housings  114 , 114   a  are constructed from a meta-aramid material. 
     In the illustrated safety apparatus  110  shown in  FIGS. 13 to 24 , the housing arrangement includes an outer housing  114  which takes the form of a meta-aramid bag, the meta-aramid construction resulting in an outer housing  114  capable of containing the energy of the ejected components and other contained energy, reducing the risk to personnel and other equipment. Moreover, the meta-aramid construction results in an outer housing  114  which is fire resistant, and thus suited to the harsh environment of an oil and gas installation. 
     As shown in  FIG. 15 , the outer housing  114  has a solid base portion  118  and a wall portion  120  extending from the base portion  118 , the base portion  18  and the wall portion  120  defining an enclosure for encompassing the end portion  16  of the actuator  12 . Beneficially, the base portion  118  and the wall portion  120  form an outer housing  114  which is capable of containing components ejected both axially and laterally from the actuator  12  in the event of failure. As shown, the outer housing  114  is generally cylindrical in shape. However, it will be recognised that the outer housing  14  may define any suitable shape. 
     A protective layer  119  is disposed on an exterior of the outer housing  114 . The protective layer  119  is formed from a nylon woven material coated in polyurethane. The protective layer  119  is generally cylindrical in shape. However, it will be recognised that the protective layer  119  may define any suitable shape. 
     A further protective layer  121  is disposed on an interior of the outer housing  114 . The protective layer  121  is formed from PVC. The protective layer  121  is generally cylindrical in shape. However, it will be recognised that the protective layer  121  may define any suitable shape. 
     The safety apparatus  110  further comprises an inner housing  122 . In use, the inner housing  122  defines an armour layer of the safety apparatus  110 . The inner housing  122  is disposed within the outer housing  114  and is configured for location about the end portion  16  of the actuator  12 . 
     In the illustrated safety apparatus  110 , the inner housing  122  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an inner housing  122  capable of containing the energy of the ejected components, reducing the risk to personnel and other equipment. 
     As shown in  FIG. 15 , the inner housing  122  has a solid base portion  124  and a wall portion  126  extending from the base portion  124 . Beneficially, the provision of outer housing  114  and inner housing  122  provides additional resistance to ejection of components of the actuator  12  in the event of failure. 
     The inner housing  122  is offset from the outer housing  114 , such that the inner housing  122  and the outer housing  114  together define a cavity  128  for receiving an indicator arrangement  130  of the safety apparatus  110 . 
     The indicator arrangement  130  is configured to provide a visual indication that failure of the actuator  12  has occurred, and comprises a visual indicator in the form of a coloured dye  132 . In the illustrated safety apparatus  110 , the dye  132  is a red in colour. However, it will be recognised that the dye  132  may be any suitable colour. 
     As shown in  FIG. 15 , the dye  132  is contained within an indicator housing  134 , the indicator housing  134  configured to puncture or otherwise release the dye  132  to indicate when failure of the actuator  12  has occurred. Release of the dye  132  may be determined externally of the actuator  12 , for example by personnel or by remote monitoring system, such as a CCTV system. The indicator housing  134  is interposed between the inner housing  122  and the outer housing  114 , and comprises a solid base portion  136  and a wall portion  138  extending from the base portion  136 , the base portion  136  and wall portion  138  defining a cavity for receiving the dye  132 . 
     As shown in  FIGS. 13 and 14 , and referring also to  FIG. 16  of the accompanying drawings, the safety apparatus  110  further comprises a second outer housing  114   a , the outer housing  114   a  encompassing an end portion  16   a  of the actuator  12 . 
     As shown in  FIG. 16 , the outer housing  114   a  is substantially identical to the outer housing  114 , having a solid base portion  118   a  and a wall portion  120   a  extending from the base portion  118   a , the base portion  118   a  and the wall portion  120   a  defining an enclosure for encompassing the end portion  16   a  of the actuator  12 . The base portion  118   a  and the wall portion  120   a  form an outer housing  114   a  which is capable of containing components ejected both axially and laterally from the actuator  12  in the event of failure. The outer housing  114   a  is generally cylindrical in shape. However, it will be recognised that the outer housing  114   a  may define any suitable shape. 
     The outer housing  114   a  takes the form of a meta-aramid bag, the meta-aramid construction resulting in an outer housing  114   a  capable of containing the energy of the ejected components, reducing the risk to personnel and other equipment. The meta-aramid construction also results in an outer housing  114   a  which is fire resistant, and which is thus suited to the harsh environment of an oil and gas installation. 
     A protective layer  119   a  is disposed on an exterior of the outer housing  114   a . The protective layer  119   a  is formed from a nylon woven material coated in polyurethane. The protective layer  119   a  is generally cylindrical in shape. However, it will be recognised that the protective layer  119   a  may define any suitable shape. 
     A further protective layer  121   a  is disposed on an interior of the outer housing  114   a . The protective layer  121   a  is formed from PVC. The protective layer  121   a  is generally cylindrical in shape. However, it will be recognised that the protective layer  121   a  may define any suitable shape. 
     The safety apparatus  10  further comprises an inner housing  122   a , the inner housing  122   a  disposed within the outer housing  114   a  and configured for location about the end portion  16   a  of the actuator  12 . In use, the inner housing  122   a  defines an armour layer of the safety apparatus  10 . 
     As shown in  FIG. 16 , the inner housing  122   a  has a solid base portion  124   a  and a wall portion  126   a  extending from the base portion  124   a . Beneficially, the provision of outer housing  114   a  and inner housing  122   a  provides additional resistance to ejection of components of the actuator  12  in the event of failure. 
     The inner housing  122   a  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an inner housing  122   a  capable of containing the energy of the ejected components, and reducing the risk to personnel and other equipment. 
     The inner housing  122   a  is offset from the outer housing  114   a , such that the inner housing  122   a  and the outer housing  114   a  together define a cavity  128   a  for receiving an indicator arrangement  130   a.    
     The indicator arrangement  130   a  is configured to provide a visual indication that failure of the actuator  12  has occurred, and comprises a visual indicator in the form of a coloured dye  132   a . In the illustrated safety apparatus  110 , the dye  132   a  is a red in colour. However, it will be recognised that the dye  132   a  may be any suitable colour. 
     As shown in  FIG. 16 , the dye  132   a  is contained within an indicator housing  134   a , the indicator housing  134   a  configured to puncture or otherwise release the dye  132   a  to indicate when failure of the actuator  12  has occurred. Release of the dye  132   a  may be determined externally of the actuator  12 , for example by personnel or by remote monitoring system, such as a CCTV system. The indicator housing  134   a  is interposed between the inner housing  122   a  and the outer housing  114   a , and comprises a solid base portion  136   a  and a wall portion  138   a  extending from the base portion  136   a , the base portion  136   a  and wall portion  138   a  defining a cavity for receiving the dye  132   a.    
     As shown in  FIGS. 17 and 18 , in the safety apparatus  110  the outer housings  114 , 114   a  each comprise a weep hole  139 , 139   a  for permitting the dye  132 , 132   a  to escape, and thus indicate that the actuator  12  has failed. 
     As shown in  FIGS. 13 and 14  and referring now also to  FIGS. 15 and 16  of the accompanying drawings, the indicator arrangement  130   a  further comprises a label  140   a  and a safety indicator in the form of indicator strip  140   b . The indicator strip  140   b  comprises a piece of material which is folded and/or sown together to form a seam. In use, when exposed to an axial load the seam bursts, thereby exposing the indicator strip  140   b.    
     As shown in  FIGS. 13 and 14 , the safety apparatus  110  has a securement arrangement—shown generally by  142 —configured to retain the outer housings  114 , 114   a  on the actuator  12 . 
     The securement arrangement  142  is configured for location around the housings  114 , 114   a  and comprises a plurality of straps  144 . In the safety apparatus  110 , the straps  144  are constructed from an Ultra-High Molecular Weight Polyethylene (UHMwPE), e.g. Dyneema®. 
     Referring now also to  FIGS. 21, 22, 23 and 24  of the accompanying drawings, there are shown enlarged views of parts of the securement arrangement  142 . 
     As shown in  FIG. 21 , the securement arrangement  142  further comprises guides  146 , the guides  146  provided on the housings  114 , 114   a , respectively. The guides  146  are disposed at the interfaces between the straps  144  to assist in installation and to ensure that the straps  144  remain in position once installed. 
     As shown in  FIG. 22 , the securement arrangement  142  further comprises profiled edge pieces  148 , the edge pieces  148  provided on the housing  114 , 114   a , respectively. The edge pieces  148  are disposed at the interface between the base portion  118  and the wall portion  120  and at the interface between the base portion  118   a  and the wall portion  120   a . The edge pieces  48  guide the straps  144  around the interface between the base portions  118 , 118   a  and the wall portion  120 , 120   a  while avoiding sharp edges. 
     As shown in  FIG. 23 , the securement arrangement  42  further comprises buckles  49 . 
     As shown in  FIG. 24 , the securement arrangement  142  further comprises fasteners  150 , the fasteners  150  in the safety apparatus  10  comprising ratchet fasteners, buckle or similar appropriate joining arrangement. 
     As described above, the safety apparatus  10 , 110  are merely exemplary and various modifications may be made. 
     For example, reference is now made to  FIG. 25  of the accompanying drawings which shows a further alternative safety apparatus  210 . The safety apparatus  210  is similar to the safety apparatus  10  and like components are represented by like numerals incremented by 200. However, whereas the safety apparatus  10  comprises two outer housings  14 , 14   a , in the safety apparatus  210  a single outer housing  214  is provided. 
     The safety apparatus  210  has a housing arrangement including an outer housing  214 , the outer housing  214  encompassing an end portion  16  of the actuator  12 . 
     In the illustrated safety apparatus  210  shown in  FIGS. 25 to 30 , the outer housing  214  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an outer housing  214  capable of containing the energy of the ejected components and other contained energy, reducing the risk to personnel and other equipment. 
     As shown in  FIG. 26 , the outer housing  214  has a solid base portion  218  and a wall portion  220  extending from the base portion  218 , the base portion  218  and the wall portion  220  defining an enclosure for encompassing the end portion  16  of the actuator  12 . Beneficially, the base portion  218  and the wall portion  220  form an outer housing  214  which is capable of containing components ejected both axially and laterally from the actuator  12  in the event of failure. As shown, the outer housing  214  is generally cylindrical in shape. However, it will be recognised that the outer housing  214  may define any suitable shape. 
     A protective layer  219  is disposed on an exterior of the outer housing  214 . The protective layer  219  is formed from a nylon woven material coated in polyurethane. The protective layer  219  is generally cylindrical in shape. However, it will be recognised that the protective layer  219  may define any suitable shape. 
     A further protective layer  221  is disposed on an interior of the outer housing  214 . The protective layer  221  is formed from PVC. The protective layer  221  is generally cylindrical in shape. However, it will be recognised that the protective layer  221  may define any suitable shape. 
     The housing arrangement of the safety apparatus  210  further comprises an inner housing  222 . In use, the inner housing  222  defines an armour layer of the safety apparatus  210 . The inner housing  222  is disposed within the outer housing  214  and is configured for location about the end portion  16  of the actuator  12 . 
     In the illustrated safety apparatus  210 , the inner housing  222  takes the form of a para-aramid bag, the para-aramid construction beneficially resulting in an inner housing  222  capable of containing the energy of the ejected components, reducing the risk to personnel and other equipment. 
     As shown in  FIG. 26 , the inner housing  222  has a solid base portion  224  and a wall portion  226  extending from the base portion  224 . Beneficially, the provision of outer housing  214  and inner housing  222  provides additional resistance to ejection of components of the actuator  12  in the event of failure. 
     The inner housing  222  is offset from the outer housing  214 , such that the inner housing  222  and the outer housing  214  together define a cavity  228  for receiving an indicator arrangement  230 , the indicator arrangement  230  forming part of the housing arrangement of the safety apparatus  210 . 
     The indicator arrangement  230  is configured to provide a visual indication that failure of the actuator  12  has occurred, and comprises a visual indicator in the form of a coloured dye  232 . In the illustrated safety apparatus  210 , the dye  232  is a red in colour. However, it will be recognised that the dye  232  may be any suitable colour. 
     As shown in  FIG. 26 , the dye  232  is contained within an indicator housing  234 , the indicator housing  234  configured to puncture or otherwise release the dye  232  to indicate when failure of the actuator  12  has occurred. Release of the dye  232  may be determined externally of the actuator  12 , for example by personnel or by remote monitoring system, such as a CCTV system. The indicator housing  234  is interposed between the inner housing  222  and the outer housing  214 , and comprises a solid base portion  236  and a wall portion  238  extending from the base portion  236 , the base portion  236  and wall portion  238  defining a cavity for receiving the dye  232 . 
     Referring now also to  FIGS. 27, 28, 29 and 30  of the accompanying drawings, there are shown enlarged views of parts of the securement arrangement  242 . 
     As shown in  FIG. 27 , the securement arrangement  242  further comprises guides  246 , the guides  246  provided on the housing  14 . The guides  246  are disposed at the interfaces between the straps  244  to assist in installation and to ensure that the straps  244  remain in position once installed. 
     As shown in  FIG. 28 , the securement arrangement  242  further comprises profiled edge pieces  248 , the edge pieces  248  provided on the housing  14 . The edge pieces  48  are disposed at the interface between the base portion  218  and the wall portion  220 . The edge pieces  248  guide the straps  244  around the interface between the base portion  18  and the wall portion  20  while avoiding sharp edges. 
     As shown in  FIG. 29 , the securement arrangement  242  further comprises buckles  249 . 
     As shown in  FIG. 30 , the securement arrangement  242  further comprises a fastener  250 , the fastener  250  in the safety apparatus  210  comprising a ratchet fastener, a buckle or similar appropriate joining arrangement.