www.innospection.com
Tank inspections, assessments and certifications.
In the current economic climate, many Owner / Operators of bulk liquid Storage Tanks have had to review the frequency & scope of inspections and have a closer look at what the minimum requirements are. The aim being to remain true to their obligations in terms of Health and Safety, Environmental, Insurance, and License agreements; as well as to adhere to their Corporate Policies and undertakings. However, corrosion and the on-set of tighter legislation continue unabated; leaving Engineers and Managers exposed to both corporate and personal prosecutions if they fail to get it right. In the final analysis, it essentially comes down to risk management, and the avoidance of an incident. It has therefore become incumbent upon all to apply Risk Based Inspection principles.
Universally, a Competent Authority ( CA) comprising the Health and Safety Executive, Environmental Agency, Emergency Services, and the Local Government apply the License and legislative ordinances that govern the operation of Storage Tank farms. The CA typically specifies a standard, a code of practice or a publication, such as EEMUA 159 or API 653 as the minimum acceptable standard to be applied for compliance with the legislation. It is a frequent misconception that one can simply specify an "API Inspection" or an "EEMUA inspection" and expect to have the contractors bid against a common scope of work. This will become apparent when one compares typical sample reports and bid prices of each of the bidders.
All the inspection standards and publications make it clear that the ultimate responsibility for compliance with the standard or publication rests solely with the tank Owner / Operator. This is because they alone hold the purse strings, and therefore they alone determine the scope and extent of any inspections and remedial works. There are several very serious dangers in not having a detailed and code compliant specification for all tank inspection works. Take for example a thickness test on the shell. If the position of the test is done at different locations when successive inspections are done, then one can’t determine a reliable rate of corrosion. Without a reliable rate of corrosion one can not forecast the life of that portion of the asset. If one can’t forecast the life, then one can not hope to plan outages, and one also risks getting to a stage when the tank is operating beyond the recommended retirement date. Both of these serious scenarios are avoidable, and both have potentially damaging consequences.
It is also very important to have more than simply pages of statistical data quoted in the report. There needs to be an analysis of the results obtained, and recommendations and options given. For example, the shell thicknesses need to be compared to the retirement thicknesses, taking into consideration the operating parameters of the tank, such as the product specific gravity, liquid fill height, the corrosiveness of the product, etcetera. Some tanks may be found to have been built with little or no corrosion allowance, some may have been modified with the addition of further shell courses ( additional height ), some may have corroded to the extent that they now need wind girders. These various issues all need consideration by a qualified and experienced Tank Engineer, Authorised Tank Inspector or Tank Integrity Assessor. The findings affect the recommendations and options available to the owner / operator for the continued safe use of the tank, and will also impact on the capital expenditure forecasts for the Terminal and the recommendations which the management make to the board of directors.
When it comes to tank floor inspections, the use of a rapid scanning technique is often specified because it gives such comprehensive coverage of the floor area . It is important to note that these techniques are not a direct measurement of the floor thickness, but rather they give a value based on comparative results obtained from scanning a calibration plate. The calibration plate being a test plate with precisely machined defects in it. It is important to check that the operators of the scanning equipment re-calibrate the scanner in situ in the tank, this is because the calibration settings can be lost if the equipment is stripped down and shipped about between being calibrated and re-assembled on site. It is also important that the calibration is then "proved-up" with UT readings of an actual known defect in the tank. This is because the calibration plate may be a different steel to the steel from which the tank floor was constructed. At Innospection Ltd UK, for QA purposes, we re-calibrate at the start of every shift, and also after any breaks just in case someone has fiddled with the equipment in our absence.
Tank floor scanners available today typically produce a computer generated coloured map. The maps produced come with different colours depicting the areas of different percentages of metal loss. It is important to be aware of the different technologies available, at Innospection Ltd UK we use the worlds leading technology, known as SLOFEC. This is an "eddy current " technology which is capable of scanning through carbon steel up to 35mm thick and of scanning through floor coatings and linings up to 10mm thick. The inspection speed is 25m/min and separate maps are generated depicting top-side losses and under-side losses. The physics involved enables SLOFEC to pick up even relatively small pits. Please see www.innospection.com for further details.
CURRENT AND EMERGING REQUIREMENTS FOR FUEL STORAGE SITES IN THE UK.
On 11 December 2009, the PSLG ( Process Safety Leadership Group ) published its final report. The PSLG took over the legacy of the BSTG ( Buncefield Standards Task Group ). The PSLG document is the product of collaboration between the Regulator who is the CA ( Competent Authority , ie Environmental Agency plus the Health & Safety Executive ) and Industry ( comprising : UKPIA = United Kingdom Petroleum Industry Association, The TSA = Tank Storage Association, UKOPA United Kingdom Pipeline Operators Association, The CIA = Chemical Industries Association and the Trades Union Congress ).
Paragraph 27 of the report states :- Within six months of the publication of this report, duty holders should undertake a gap analysis of their compliance with the revised and new guidance contained within this report for "in-scope gasoline tanks" (as defined in paragraph 24) and record their findings. Within nine months of the publication of this report duty holders should agree with the CA an improvement plan to comply with this guidance.
The understanding is that the HSE representatives in all regions of the UK will shortly be out to discuss the implementation of this report with the various Terminals, and if there is no movement towards compliance, then difficulties can be expected.
Pragraph 24 reads as follows :
Definition of "in-scope gasoline tanks" :
In-scope gasoline tanks are defined as: those storing gasoline (petrol) as defined in Directive 94/63/EC European Parliament and Council Directive 94/63/EC of 20 December 1994 on the control of volatile organic compound emissions resulting from the storage of petrol and its distribution from terminals to service stations; vertical, cylindrical, non-refrigerated, above-ground storage tanks typically designed to standards BS 2654, BS EN 14015, API 620, API 650 (or equivalent codes at the time of construction); with side walls greater than 5 m in height; and filled at rates greater than 100 m3/hour (this is approximately 75 tonnes/hour of gasoline). The Containment Policy does not define the meaning of bulk storage, but for the purposes of this guidance the following criteria apply: The liquid is stored in an atmospheric storage tank built to a recognised design code as quoted above.
Figure 1 of the PSLG report relates to "Compliance at existing COMAH establishments" it states that "in-scope gasoline tanks" must comply with the PSLG recommendations in full as a minimum standard. It is therefore recommended that a copy of the PSLG Final Report be studied. It is available on the internet. Please see the attached link : http://www.hse.gov.uk/comah/buncefield/fuel-storage-sites.pdf
It is understood that sites storing gasoline are the highest on the CA’s list of priorities, with the "primary containment" aspects being the most important issue.
The HSE have recommended the application of EEMUA 159 and API 653 as suitable and acceptable practice in terms of storage tank integrity assessments ( and repair as applicable ).
A brief overview of some of the COMAH 1999 implications are as follows :
In terms of the containment policy, in the COMAH Regulations 1999, a Tank must be designed and constructed to a relevant standard to ensure mechanical integrity and that it is compatible with the liquid stored. Excessive vapour generation due to over-fill must be prevented by : Automated Tank gauging, High level alarms, and for products generating flammable vapour clouds a High High Level trip must be fitted for actuation of a ROSOV or an auto-diversion of flow to a safe place. Suitable foundations, Inspection and testing and maintenance need to be in place to prevent a failure of primary containment.
Pipework within a bund needs to have adequate fire resistant supports, the number of joints must be kept to a minimum, and there must be little or no stress imposed on the tank shell, and the pipeline must have thermal reliefs fitted. Remotely Operated Shut Off Valves ( ROSOV’s) must be "fail to safe" ( eg spring closed if the power supply fails ) . These valves must be able to be shut under emergency conditions without any risk to people. Tanks must be isolatable via firesafe anti-static valves on the tank import and export nozzles.
Bunds must be impermeable and sized to be the greater of either 110% of the largest tank and / or 25% of the total volume of all tanks within the bund. Any rainwater drain must require positive action to activate it. No pipework is permitted through the bund floor. Pipework should not penetrate bund walls, and where it occurs, suitable sealing is to be provided. The condition of the bund and its performance is to be assessed by a competent person. For flammable products, bunds are required to have a fire resistant structural integrity. For flammables of density less than that of water, a fire water draw off below the flammable liquid level is required ( ie the provision of a low level suction in the bund ). Any given bund area must not contain incompatible products.
Tank inspections, assessments and certifications.
In the current economic climate, many Owner / Operators of bulk liquid Storage Tanks have had to review the frequency & scope of inspections and have a closer look at what the minimum requirements are. The aim being to remain true to their obligations in terms of Health and Safety, Environmental, Insurance, and License agreements; as well as to adhere to their Corporate Policies and undertakings. However, corrosion and the on-set of tighter legislation continue unabated; leaving Engineers and Managers exposed to both corporate and personal prosecutions if they fail to get it right. In the final analysis, it essentially comes down to risk management, and the avoidance of an incident. It has therefore become incumbent upon all to apply Risk Based Inspection principles.
Universally, a Competent Authority ( CA) comprising the Health and Safety Executive, Environmental Agency, Emergency Services, and the Local Government apply the License and legislative ordinances that govern the operation of Storage Tank farms. The CA typically specifies a standard, a code of practice or a publication, such as EEMUA 159 or API 653 as the minimum acceptable standard to be applied for compliance with the legislation. It is a frequent misconception that one can simply specify an "API Inspection" or an "EEMUA inspection" and expect to have the contractors bid against a common scope of work. This will become apparent when one compares typical sample reports and bid prices of each of the bidders.
All the inspection standards and publications make it clear that the ultimate responsibility for compliance with the standard or publication rests solely with the tank Owner / Operator. This is because they alone hold the purse strings, and therefore they alone determine the scope and extent of any inspections and remedial works. There are several very serious dangers in not having a detailed and code compliant specification for all tank inspection works. Take for example a thickness test on the shell. If the position of the test is done at different locations when successive inspections are done, then one can’t determine a reliable rate of corrosion. Without a reliable rate of corrosion one can not forecast the life of that portion of the asset. If one can’t forecast the life, then one can not hope to plan outages, and one also risks getting to a stage when the tank is operating beyond the recommended retirement date. Both of these serious scenarios are avoidable, and both have potentially damaging consequences.
It is also very important to have more than simply pages of statistical data quoted in the report. There needs to be an analysis of the results obtained, and recommendations and options given. For example, the shell thicknesses need to be compared to the retirement thicknesses, taking into consideration the operating parameters of the tank, such as the product specific gravity, liquid fill height, the corrosiveness of the product, etcetera. Some tanks may be found to have been built with little or no corrosion allowance, some may have been modified with the addition of further shell courses ( additional height ), some may have corroded to the extent that they now need wind girders. These various issues all need consideration by a qualified and experienced Tank Engineer, Authorised Tank Inspector or Tank Integrity Assessor. The findings affect the recommendations and options available to the owner / operator for the continued safe use of the tank, and will also impact on the capital expenditure forecasts for the Terminal and the recommendations which the management make to the board of directors.
When it comes to tank floor inspections, the use of a rapid scanning technique is often specified because it gives such comprehensive coverage of the floor area . It is important to note that these techniques are not a direct measurement of the floor thickness, but rather they give a value based on comparative results obtained from scanning a calibration plate. The calibration plate being a test plate with precisely machined defects in it. It is important to check that the operators of the scanning equipment re-calibrate the scanner in situ in the tank, this is because the calibration settings can be lost if the equipment is stripped down and shipped about between being calibrated and re-assembled on site. It is also important that the calibration is then "proved-up" with UT readings of an actual known defect in the tank. This is because the calibration plate may be a different steel to the steel from which the tank floor was constructed. At Innospection Ltd UK, for QA purposes, we re-calibrate at the start of every shift, and also after any breaks just in case someone has fiddled with the equipment in our absence.
Tank floor scanners available today typically produce a computer generated coloured map. The maps produced come with different colours depicting the areas of different percentages of metal loss. It is important to be aware of the different technologies available, at Innospection Ltd UK we use the worlds leading technology, known as SLOFEC. This is an "eddy current " technology which is capable of scanning through carbon steel up to 35mm thick and of scanning through floor coatings and linings up to 10mm thick. The inspection speed is 25m/min and separate maps are generated depicting top-side losses and under-side losses. The physics involved enables SLOFEC to pick up even relatively small pits. Please see www.innospection.com for further details.
CURRENT AND EMERGING REQUIREMENTS FOR FUEL STORAGE SITES IN THE UK.
On 11 December 2009, the PSLG ( Process Safety Leadership Group ) published its final report. The PSLG took over the legacy of the BSTG ( Buncefield Standards Task Group ). The PSLG document is the product of collaboration between the Regulator who is the CA ( Competent Authority , ie Environmental Agency plus the Health & Safety Executive ) and Industry ( comprising : UKPIA = United Kingdom Petroleum Industry Association, The TSA = Tank Storage Association, UKOPA United Kingdom Pipeline Operators Association, The CIA = Chemical Industries Association and the Trades Union Congress ).
Paragraph 27 of the report states :- Within six months of the publication of this report, duty holders should undertake a gap analysis of their compliance with the revised and new guidance contained within this report for "in-scope gasoline tanks" (as defined in paragraph 24) and record their findings. Within nine months of the publication of this report duty holders should agree with the CA an improvement plan to comply with this guidance.
The understanding is that the HSE representatives in all regions of the UK will shortly be out to discuss the implementation of this report with the various Terminals, and if there is no movement towards compliance, then difficulties can be expected.
Pragraph 24 reads as follows :
Definition of "in-scope gasoline tanks" :
In-scope gasoline tanks are defined as: those storing gasoline (petrol) as defined in Directive 94/63/EC European Parliament and Council Directive 94/63/EC of 20 December 1994 on the control of volatile organic compound emissions resulting from the storage of petrol and its distribution from terminals to service stations; vertical, cylindrical, non-refrigerated, above-ground storage tanks typically designed to standards BS 2654, BS EN 14015, API 620, API 650 (or equivalent codes at the time of construction); with side walls greater than 5 m in height; and filled at rates greater than 100 m3/hour (this is approximately 75 tonnes/hour of gasoline). The Containment Policy does not define the meaning of bulk storage, but for the purposes of this guidance the following criteria apply: The liquid is stored in an atmospheric storage tank built to a recognised design code as quoted above.
Figure 1 of the PSLG report relates to "Compliance at existing COMAH establishments" it states that "in-scope gasoline tanks" must comply with the PSLG recommendations in full as a minimum standard. It is therefore recommended that a copy of the PSLG Final Report be studied. It is available on the internet. Please see the attached link : http://www.hse.gov.uk/comah/buncefield/fuel-storage-sites.pdf
It is understood that sites storing gasoline are the highest on the CA’s list of priorities, with the "primary containment" aspects being the most important issue.
The HSE have recommended the application of EEMUA 159 and API 653 as suitable and acceptable practice in terms of storage tank integrity assessments ( and repair as applicable ).
A brief overview of some of the COMAH 1999 implications are as follows :
In terms of the containment policy, in the COMAH Regulations 1999, a Tank must be designed and constructed to a relevant standard to ensure mechanical integrity and that it is compatible with the liquid stored. Excessive vapour generation due to over-fill must be prevented by : Automated Tank gauging, High level alarms, and for products generating flammable vapour clouds a High High Level trip must be fitted for actuation of a ROSOV or an auto-diversion of flow to a safe place. Suitable foundations, Inspection and testing and maintenance need to be in place to prevent a failure of primary containment.
Pipework within a bund needs to have adequate fire resistant supports, the number of joints must be kept to a minimum, and there must be little or no stress imposed on the tank shell, and the pipeline must have thermal reliefs fitted. Remotely Operated Shut Off Valves ( ROSOV’s) must be "fail to safe" ( eg spring closed if the power supply fails ) . These valves must be able to be shut under emergency conditions without any risk to people. Tanks must be isolatable via firesafe anti-static valves on the tank import and export nozzles.
Bunds must be impermeable and sized to be the greater of either 110% of the largest tank and / or 25% of the total volume of all tanks within the bund. Any rainwater drain must require positive action to activate it. No pipework is permitted through the bund floor. Pipework should not penetrate bund walls, and where it occurs, suitable sealing is to be provided. The condition of the bund and its performance is to be assessed by a competent person. For flammable products, bunds are required to have a fire resistant structural integrity. For flammables of density less than that of water, a fire water draw off below the flammable liquid level is required ( ie the provision of a low level suction in the bund ). Any given bund area must not contain incompatible products.
