Guidance for safe bitumen tank management

Transcription

1 Guidance for safe bitumen tank management Minera Products Association mpa asphat Minera Products Association

2 2 - guidance for safe bitumen tank management MPA Asphat is part of the Minera Products Association (MPA) - the trade association for the aggregates, asphat, cement, concrete, dimension stone, ime, mortar, and siica sand industries and is the sectora voice for minera products. Its membership aso incudes companies manufacturing road construction and quarrying pant and equipment and UK producers of petroeum bitumen. The Refined Bitumen Association is the consoidated voice of the UK bitumen suppy industry. Its membership comprises the UK s major bitumen producers who, between them, suppy neary a of the country s bitumen. The RBA promotes the most effective use of bituminous materias within the construction industry, provides technica support and funds research into bituminous products. It is aso invoved in the deveopment of industry poicy on quaity assurance and best practices reating to safety, storage and handing of bitumen. Whist every care is taken to ensure the accuracy of the genera information and advice offered herein or given by staff of the Minera Products Association and the Refined Bitumen Association, no iabiity or responsibiity of any kind can be accepted by the Minera Products Association, the Refined Bitumen Association or their staff.

3 3 - guidance for safe bitumen tank management Contents page item 4 Introduction the Origin of Spis tank Dimensions & Capacity 5 conversion Factors tank Contents Measurement Instrumentation 6 interpretation/presentation of Tank Contents Measurement Information 7 communication Between the Deivery Tanker Driver and Asphat Pant operationa Personne Summary 8 Appendices 1 Capacity of Vertica Cyindrica Bitumen Storage Tanks 1 Capacity of Cuboid Type Bitumen Storage Tanks 1 Capacity of Horizonta Cyindrica Bitumen Storage Tanks 2 Schematic Instaation Diagram of Non-Contact Radar and Independent High High Leve Aarm Switch 2 Schematic Instaation Diagram of TDR Contact Radar and Independent High High Leve Aarm Switch 2 Schematic Instaation Diagram of Hydrostatic Contents Gauge and independent High High Leve Aarm Switch 3 Possibe Mode for the Dispay of Tankside Information 15 other information

4 4 - guidance for safe bitumen tank management Guidance for safe bitumen tank management INTRODUCTION There are around 325 asphat manufacturing pants throughout the UK invoving approximatey 1300 bitumen storage tanks. Spiages from these bitumen storage tanks as a resut of overfiing have a high potentia for serious injury as bitumen is stored at high temperatures and has a arge therma capacity. Statistics compied for the 6 years, from 1998 to 2003 for reported bitumen spiages at UK deivery sites, show that on average across the industry there were 60 spiages, with 78, 79 & 82 for the years 2001, 2002 & 2003 respectivey. There has been an improvement from a high of 82 spis in 2003, but the number of spis sti averages 27 per year for the 3 years 2010 to This document expains the fundamenta principes that need to be adopted at a asphat pants, for the safe operation of bitumen storage tanks, to reduce the risk of occurrence of a potentiay serious incident. THE ORIGIN OF SPILLS Spis have occurred from the bitumen tanks on many sites due to overfiing as a resut of the incorrect determination of the avaiabe uage space due to a number of factors: 1. Lack of Knowedge of Tank Dimensions & Capacity 2. use of Incorrect Conversion Factors 3. unsuitabe or Wrongy Appied Tank Measurement Instrumentation 4. Incorrect Interpretation/Presentation of Tank Contents Measurement Information 5. Poor Communication between the Deivery Tanker Driver and Asphat Pant Operating Personne 1. TANK DIMENSIONS & CAPACITY A. Storage Tank Capacity and the Determination of Uage The correct determination of the uage space in a given bitumen storage tank is crucia to preventing spis and to ensure this, it is important to estabish what is the actua working storage capabiity of a given tank. There is a ack of uniformity across the asphat industry, with both tank manufacturers and site operating companies, when stating the storage capacity of site bitumen tanks, in terms of the terminoogy used and the units of measurement. Aso, in some cases there is a ack of awareness by site operating personne regarding the storage capabiity of their bitumen tanks and frequenty there are no detais or drawings readiy avaiabe for reference regarding important tank sizing dimensions, incuding their height, diameter, positions of off take and overfi pipes, etc. It is vita that this information is avaiabe to enabe the accurate cacuation of tank capacities, obtained either from tank manufacturers drawings or by on site tank survey measurements and for the industry to adopt common terminoogy for defining tank capacity. B. Definition of Tank Capacity Using the foowing terms and definitions we can cacuate the tank storage capacity for any given tank (as ong as the correct tank data is avaiabe): Nomina Tank Capacity Interna voume in m 3 from the tank bottom to the tank top. Unavaiabe Tank Capacity Interna voume in m 3 from the norma tank draw off pipework to the bottom of the tank + Inside voume in m 3 from the overfi/ vent pipe to the tank top. Avaiabe Tank Capacity Interna voume in m 3 from the norma tank draw off pipework to the overfi/vent pipe. Safe Working Tank Capacity 90% of the avaiabe tank capacity in m 3. Conversion from voume to mass Mutipy voumes in m 3 by 0.92 tonnes/m 3 to express the capacity in tonnes. By way of an exampe in the use of these terms and to show how confusion can arise, consider a new tank recenty instaed on a customer site to hod 100 tonnes of bitumen. Nomina tank capacity 105.8m tonnes Unavaiabe tank capacity 5.3m m 3 = 6.3m tonnes Avaiabe tank capacity 99.5m tonnes Safe working tank capacity 89.6m tonnes

5 5 - guidance for safe bitumen tank management As can be seen from the above, the tank is ony capabe of safey storing 82.4 tonnes of bitumen that can be used for asphat production and not 100 tonnes as impied. The use of a more rigorous statement of the capacity required woud have prevented such a misunderstanding. See the diagrams in Appendix 1 for representation of the above terminoogy for vertica and horizonta tanks. C. The Determination of Uage Foowing on from the definitions previousy discussed, deciding whether there is sufficient space in a particuar storage tank to safey receive a panned deivery of bitumen of known weight (expressed in tonnes) without overfiing invoves: determination of the unused part of the safe working capacity in voumetric terms expressed in cubic metres. conversion of this voume into the mass (or weight) of bitumen that can be safey stored, using the worst case density figure of tonnes/m 3. Impicit in these cacuations is the assumption that the tank shapes (either horizonta cyinders, vertica cyinders or rectanguar cuboids) are uniform and remain so when the tanks are fied/emptied and that the tank dimensions provided by the manufacturer are accurate. 2. CONVERSION FACTORS There is an obvious difficuty in expressing the capacity of a given tank in weight, as the weight of a particuar grade of bitumen that can be stored in a given voume depends on the density of the bitumen, which varies according to the storage temperature. Significanty, there are considerabe differences, between both tank manufactures and operating sites, in the density vaues used for a given grade of bitumen being stored, often far too high, that coud never be appicabe for the range of temperatures at which it is normay stored. Conversion from voumetric to mass units, shoud use the worst case density for the bitumen being stored, to avoid overfiing, i.e. the density of the bitumen at its highest recommended storage temperature (the owest vaue of density ikey to be encountered), when a given mass of bitumen occupies its argest voume. It turns out that the worst case density vaue for a grades of bitumen typicay stored is around 920kg/m 3 (or tonnes/m 3 ), which is the vaue that shoud be used when converting from voume to mass. 3. TANK CONTENTS MEASUREMENT INSTRUMENTATION In practice, measurement of the iquid eve or uage distance and the conversion of either of these into an expression of the tank contents are usuay accompished by some form of tank contents measurement instrumentation. The readings from these, according to their range of measurement and the units used, are interpreted by the operator, to decide whether there is sufficient room in a given tank to safey receive a tanker deivery of bitumen. To warn of abnorma conditions, which if eft unheeded coud ead to difficuties incuding the possibiity of an overspi, various aarms are provided, either derived from the measurement equipment, or by independent means. A. Measurement Derived Aarms Measurement signas from the contents measuring instrumentation are often used to generate various aarms, usuay to warn of abnorma operating conditions, typicay high eve (HLA), or high high eve (HHLA) aarms, to prevent a potentia overspi condition and ess commony ow eve (LLA) aarms to prevent a possibe tank overheating condition. A measurement derived aarm must be fitted to a bitumen tanks. In the event of a mafunction of the contents measuring instrumentation, or as a resut of incorrect setting up, these types of aarms coud fai to provide any overspi safeguard. On some of the tanks fitted with mechanica buoyancy eve indicators, both of the Cat & Mouse and rotary types, high eve and sometimes ow eve aarms are generated using micro or proximity type switches operated by a pointer mechanism. B. Independent High High Leve Aarm Devices in an attempt to avoid overspis, sites have equipped their tanks with high eve aarm generating devices, that act independenty from the contents measuring instrumentation, to provide an independent high high eve aarm (HHLA). These aarms are derived from fixed position switches or probes within the tank, which operate when the bitumen makes contact with them. These must be used in addition to the measurement derived high eve aarms. Independent high eve switch devices must be fitted to a bitumen storage tanks, to provide a safeguard from spis in the event of a faut or probem with the contents measuring instrumentation, or because of some error in the transation of eve measurement into voumetric contents, due to possibe tank dimensiona or deformation abnormaities and/or the buid up of product on the side was of the tank.

6 6 - guidance for safe bitumen tank management Further, where the contents measurement is based on the use of hydrostatic instruments, then the fitting of independent high eve switches must be an essentia priority, as it is not possibe with this technoogy to provide with absoute certainty measurement derived aarms that directy reate to the eve of bitumen stored. C. Setting Up of Tank Contents Instrumentation Taking into account the earier parts of the report reating to avaiabe tank capacity and safe working tank capacity, the minimum tank contents instrumentation to prevent overspis must incude a contents measuring instrument, a measurement derived high eve aarm (HLA) and an independent fixed position point contact high high eve aarm (HHLA) switch. These must be arranged such that: The tank contents instrumentation must be instaed with a measurement span set to cover the height range corresponding to the avaiabe tank capacity. A measurement derived high eve aarm (HLA) must be provided, set at the height corresponding to the safe working capacity, that is 90% of the avaiabe tank capacity, with instructions to the driver to stop oading, shoud it be initiated. An independent fixed position point contact high high eve aarm (HHLA) switch must be instaed, set at the height in the tank corresponding to 92.5% of the avaiabe tank capacity, providing the protection to prevent the tank overfiing, with instructions to the deivery driver to shutdown immediatey, shoud it be initiated. 4. INTERPRETATION/PRESENTATION OF TANK CONTENTS MEASUREMENT INFORMATION Safe bitumen storage tank management requires the cear presentation of the information to both pant operating personne for a aspects of the operation and to the deivery tanker driver during the deivery/ offoading process. A. Deivery Tanker Driver Minimum Information Requirements Large individua amber indicator amps, one per tank to provide HLA warning which is activated off the eve measuring system and positioned to be easiy visibe by the driver from the norma oading point(s), inked to a common audibe aarm kaxon, with a key operated audibe mute push button switch. Large individua red indicator amps, one per tank to provide HHLA warning which is activated off the independent aarm and positioned above the HLA amber indicator amps, inked to a common red fashing beacon with an integra audibe siren, with a key operated audibe mute push button switch, to enabe operating personne to sience the audibe aarm. Large sign or signs easiy visibe to the driver expaining the meaning of these aarms and the action to be taken in the event of them being initiated. It is recommended that the foowing shoud aso be instaed: A instruments and aarms must be part of an annua maintenance programme. This must incude caibration of instruments and aarms by competent and quaified personne. It is recommended that caibration is carried out by the instrument /aarm suppier. For tanks greater than 31m 3 safe working capacity arge individua green indicator amps, one per tank to provide confirmation that there is safe working capacity to accommodate a 31m 3 oad (approximatey 28.5 tonnes) of bitumen, positioned beow the HLA amber indicator amps. See the diagrams in Appendix 2 for exampes of measurement and aarm set ups using non contact radar, contact radar (TDR) and hydrostatic pressure measurement systems. Large sign or signs easiy visibe to the driver expaining the meaning of these indications. B. Site Operationa Personne Information Requirements It is difficut to be too prescriptive with this, as it depends on the particuar arrangement and ayout of each site and the way in which the operation of the asphat pant and its associated bitumen tanks is managed. However, the reevant site personne need to be aware of the operationa status of the bitumen tanks at a times, particuary during the potentiay hazardous bitumen tanker deivery process and information regarding this must, therefore, be presented in the pace or paces where this can be achieved.

7 7 - guidance for safe bitumen tank management As a starting point, it is considered that tank contents measurement information, aong with the aarm presentation equipment described, must be presented in the vicinity of the tanks. The minimum information to be provided shoud be as foows: Large sign on each tank stating the Safe Working Capacity in Tonnes, based on a density conversion factor of tonnes/m 3. Large individua digita type dispay contents gauge, one per tank showing the amount of bitumen being stored within the avaiabe part of the tank expressed in Approximate Tonnes, to one decima pace, based on a density conversion factor of tonnes/m 3. It is recommended that the foowing aso be suppied: Large individua digita type dispay gauge, one per tank, mounted aongside the contents gauge showing the amount of Safe Uage Space in the tank avaiabe for the next oad, expressed in Approximate Tonnes, to one decima pace, based on a density conversion factor of tonnes/m 3. Note: With modern microprocessor based digita signa conditioning/dispay instrumentation, this is capabe of being provided at modest cost and coud avoid errors in safe uage determination. Aso, this measurement readout woud be of use to the deivery tanker driver, who woud be abe to more cosey monitor the progress of the offoading operation. Tank temperature dispay ( C) derived from a dedicated temperature transmitter positioned at the same eve as the draw off pipework, to be as far as possibe above the tank heating system. 5. COMMUNICATION BETWEEN THE DELIVERY TANKER DRIVER AND ASPHALT PLANT OPERATING PERSONNEL It is important that communication between drivers and pant personne is cear to ensure correct seection of tank for the discharging of bitumen. The driver must present the deivery documentation to pant personne who must confirm grade and quantity is correct. The pant personne must confirm the appropriate storage tank and receiving fange for the deivery. A fanges must have independent padock and keys that wi be issued and controed by pant personne. It is recommended that a Bitumen Discharge Permit is used to support this process. Under no circumstances shoud the keys and padocks be common for different fanges/tanks. SUMMARY The safe management of bitumen storage tanks and the avoidance of overfiing invove a combination of: The correct cacuation of uage using information from the tank contents instrumentation, to determine whether or not there is sufficient room in a given tank to aow a new oad to be deivered, without overfiing. Accurate and reiabe contents measurement, with unambiguous presentation of the saient information. The provision of suitabe safeguards to warn of an impending overfi condition, shoud something go wrong. C. Centraised Presentation of Measurement & Aarm Information In most instances it is considered that a of the measurement and aarm information presented in the vicinity of the tanks, as just described, shoud aso be communicated to the asphat pant contro room. This may be a separate mixer cabin type contro room near to the asphat pant, or within a contro room shared with the weighbridge as on some sites, where there is ikey to be an operator in attendance, who can monitor the bitumen tanker deivery off oading process. On new pants it is envisaged that the aarm and measurement information communicated from the bitumen tankside instrumentation wi be interfaced into the asphat coating pant s computer based contro and data acquisition system, for VDU dispay using the standard measurement and aarm data presentation packages avaiabe within the system. See Appendix 3 that shows a schematic drawing of a possibe mode for the dispay of tankside information. Participation and commitment from both the tanker driver and site operations personne during the deivery/offoading process.

8 8 - guidance for safe bitumen tank management APPENDIX 1 CAPACITY OF VERTICAL CYLINDRICAL BITUMEN STORAGE TANKS Nomina capacity Unavaiabe capacity Overfow Safe Working Leve SWL Avaiabe tank capacity Safe working capacity Overfow Safe Working Leve SWL = Heating eements = 90% of

9 9 - guidance for safe bitumen tank management APPENDIX 1 CAPACITY OF cuboid type BITUMEN STORAGE TANKS Nomina capacity Unavaiabe capacity Overfow Overfow Safe Working Leve SWL Avaiabe tank capacity Safe working capacity Overfow Overfow Safe Working Leve SWL = Heating eements = 90% of

10 10 - guidance for safe bitumen tank management APPENDIX 1 CAPACITY OF horizonta CYLINDRICAL BITUMEN STORAGE TANKS Nomina capacity Unavaiabe capacity Overfow Safe Working Leve SWL Avaiabe tank capacity Safe working capacity Overfow Safe Working Leve SWL = Heating eements = 90% of

11 11 - guidance for safe bitumen tank management APPENDIX 2 schematic instaation diagram of non-contact radar and independent HIGH high eve aarm switch Non contact radar device Independent high eve switch probe 100% Independent HHLA Safe working HLA 92.5% 90% Desirabe measuring range Low eve LLA 5% 0% pipe Overfi/ vent pipe Heater bank

12 12 - guidance for safe bitumen tank management APPENDIX 2 schematic instaation diagram of TDR contact radar & independent HIGH high eve aarm switch TDR contact radar device Independent high eve switch probe Upper banking zone 100% Independent HHLA Safe working HLA 92.5% 90% Desirabe measuring range SS Wire Low eve LLA 5% Lower banking zone Weight pipe 0% Overfi/ vent pipe Heater bank

13 13 - guidance for safe bitumen tank management APPENDIX 2 schematic instaation diagram of hydrostatic contents gauge and independent HIGH high eve aarm switch Independent high eve switch probe 100% Independent HHLA Safe working HLA 92.5% 90% Desirabe measuring range pipe Low eve LLA 5% Signa eevation (zero suppression) 0% Overfi/ vent pipe Heater bank Hydrostatic pressure TX

14 14 - guidance for safe bitumen tank management APPENDIX 3 POSSIBLE MODEL FOR THE DISPLAY OF TANKSIDE INFORMATION TTX I/O processing instruments LTX HHLS Tank 1 Tank 2 Tank 3 High high eve aarm (HHLA) Safe working capacity 80 Tonnes Fashing beacon Instrument pane Avaiabe tank contents Audibe siren with key operated mute 45.0 Tonnes Avaiabe safe uage 35.0 Tank temperature 150 Tonnes C High eve aarm (HLA) Low eve Fashing beacon Large indicator amps High high eve aarm (HHLA) High eve aarm (HLA) Uage avaiabe for fu oad of bitumen Audibe kaxon with key operated mute Information to mixer cabin contro room and/or remote monitoring system

15 15 - guidance for safe bitumen tank management Other information 1. Guide to Safe Deivery of Bitumen (UK Edition) Refined Bitumen Association 2. Mode Code of Safe Practice in the Petroeum Industry Part 11: Bitumen Safety Code Energy Institute

16 16 - safe bitumen tank management MPA Asphat is part of the Minera Products Association, the trade association for the aggregates, asphat, cement, concrete, dimension stone, ime, mortar and siica sand industries. MPA Asphat August 2013 MPA Asphat Giingham House, Giingham Street London SW1V 1HU Te +44 (0) Fax +44 (0) mpaasphat@mineraproducts.org Refined Bitumen Association Ltd Hammerain House, Hookstone Avenue Harrogate, North Yorkshire HG2 8ER Te +44 (0) Fax +44 (0)