Pressure protection for an offshore platform

Abstract

A method for pressure protection of an offshore platform ( 14, 16 ) of an oil and gas installation, the offshore platform ( 14, 16 ) being connected to source of hydrocarbons via a pipeline ( 18 ), the method comprising: using a safe link device ( 62 ) at the pipeline ( 18 ); wherein the safe link device ( 62 ) is located subsea and outside of the safety zone of the platform ( 14 ), ( 17 ); protecting the platform via a subsea High Integrity Pressure Protection System (HIPPS) for the platform ( 14, 16 ) and/or the pipeline ( 18 ); and wherein the safe link device ( 62 ) is arranged to activate to release pressure from the pipeline ( 18 ) when the pressure exceeds a preset threshold that is above the normal ultimate limit state pressure for the platform ( 14, 16 ).

1 . A method for pressure protection of an offshore platform of an oil and gas installation, the offshore platform being connected to source of hydrocarbons via a pipeline, the method comprising:
 using a safe link device at the pipeline;   wherein the safe link device is located subsea and outside of the safety zone of the platform;   protecting the platform via a subsea High Integrity Pressure Protection System (HIPPS) for the platform  14 ,  16  and/or the pipeline  18 ; and   wherein the safe link device is arranged to activate to release pressure from the pipeline when the pressure exceeds a preset threshold that is above the design pressure for the platform.   
     
     
         2 . A method as claimed in  claim 1 , wherein the HIPPS is arranged to control the pressure to a lower level than the preset threshold for activation of the safe link device. 
     
     
         3 . A method as claimed in  claim 1  or  2 , wherein the preset threshold is above the normal operating pressure for the platform and above the ultimate limit state pressure for the pipeline. 
     
     
         4 . A method as claimed in  claim 1 ,  2  or  3 , wherein the preset threshold is below the maximum allowable accumulated pressure for the platforms and/or below the accidental limit state pressure for the pipeline. 
     
     
         5 . A method as claimed in any preceding claim, wherein the safe link device is a physically triggered device including at least one of: a structure in the pipeline that is designed to burst at a set pressure, a valve with a breakable pin that will fail at the required pressure, or a rupture disc. 
     
     
         6 . A method as claimed in any preceding claim, wherein the safe link device comprises a rupture disc that will break and release the pressure from the pipeline when the pipeline pressure exceeds the preset threshold. 
     
     
         7 . A method as claimed in any preceding claim, wherein the safe link device is located 500 m or more from the platform. 
     
     
         8 . A method as claimed in any preceding claim, comprising using multiple safe link devices for redundancy and/or wherein the safe link device comprises multiple pressure activated mechanisms for redundancy. 
     
     
         9 . A method as claimed in any preceding claim, wherein the preset threshold is in the range 430-450 barg. 
     
     
         10 . A method as claimed in any preceding claim, comprising arranging the platform such that there is no mechanism for emergency depressurisation of a hydrocarbon inventory of the platform in the event of a fire or other emergency that causes an over-pressure. 
     
     
         11 . A method as claimed in any preceding claim, wherein the platform is an unmanned platform with no permanent personnel. 
     
     
         12 . A method as claimed in any preceding claim, wherein the platform is an unmanned platform and has no provision of facilities for personnel to stay on the platform, for example there may be no shelters for personnel, no toilet facilities, no drinking water, no personnel operated communications equipment, no heli-deck and/or no lifeboat. 
     
     
         13 . A method as claimed in any preceding claim, wherein the platform is an unmanned platform and requires personnel to be present for fewer than 10,000 maintenance hours per year. 
     
     
         14 . A pressure protection system for a platform of an offshore oil and gas installation, wherein the platform is connected to a source of hydrocarbons via a pipeline, the pressure protection system comprising:
 a safe link device at the pipeline;   wherein the safe link device is located subsea and outside of the safety zone of the platform;   a subsea High Integrity Pressure Protection System (HIPPS) at the platform and/or the pipeline for protecting the platform; and   wherein the safe link device is arranged to activate to release pressure from the pipeline when the pressure exceeds a preset threshold that is above the design pressure for the platform.   
     
     
         15 . A pressure protection system as claimed in  claim 14 , wherein the HIPPS is arranged to control the pressure to a lower level than the preset threshold for activation of the safe link device. 
     
     
         16 . A pressure protection system as claimed in  claim 14  or  15 , wherein the preset threshold is above the normal operating pressure for the platform and above the ultimate limit state pressure for the pipeline. 
     
     
         17 . A pressure protection system as claimed in  claim 14 ,  15  or  16 , wherein the preset threshold is below maximum allowable accumulated pressure for the platforms and/or below the accidental limit state pressure for the pipeline. 
     
     
         18 . A pressure protection system as claimed in any of  claims 14  to  17 , wherein the safe link device is a physically triggered device including at least one of: a structure in the pipeline that is designed to burst at a set pressure, a valve with a breakable pin that will fail at the required pressure, or a rupture disc. 
     
     
         19 . A pressure protection system as claimed in any of  claims 14  to  18 , wherein the safe link device comprises a rupture disc that will break and release the pressure from the pipeline when the pipeline pressure exceeds the preset threshold. 
     
     
         20 . A pressure protection system as claimed in any of  claims 16  to  19 , wherein the safe link device is located 500 m or more from the platform. 
     
     
         21 . A pressure protection system as claimed in any of  claims 16  to  20 , comprising multiple safe link devices for redundancy and/or wherein the safe link device comprises multiple pressure activated mechanisms for redundancy. 
     
     
         22 . A pressure protection system as claimed in any of  claims 14  to  21 , wherein the preset threshold is in the range 430-450 barg. 
     
     
         23 . A pressure protection system as claimed in any of  claims 14  to  22 , wherein the platform has no mechanism for emergency depressurisation of a hydrocarbon inventory of the platform in the event of a fire or other emergency that causes an over-pressure. 
     
     
         23 . A platform as claimed in any of  claims 14  to  23 , wherein the platform is an unmanned platform with no permanent personnel, wherein the unmanned platform has no provision of facilities for personnel to stay on the platform, for example there may be no shelters for personnel, no toilet facilities, no drinking water, no personnel operated communications equipment, no hell-deck and/or no lifeboat; and/or wherein the unmanned platform is arranged such that personnel are required to be present for fewer than 10,000 maintenance hours per year.