DEP SPECIFICATION
LOADING FACILITIES FOR BULK ROAD VEHICLES
DEP 31.06.11.11-Gen.
February 2011(DEP Circular 83/11 has been incorporated)
DESIGN AND ENGINEERING PRACTICE
DEM1
© 2011 Shell Group of companies
All rights reserved. No part of this publication may be reproduced, stored in a retrieval system, published or transmitted, in any form or by any means, without the prior written permission of the copyright owner or Shell Global Solutions International BV.
PREFACE
DEP (Design and Engineering Practice) publications reflect the views, at the time of publication, of Shell Global Solutions International B.V. (Shell GSI) and, in some cases, of other Shell Companies.
These views are based on the experience acquired during involvement with the design, construction, operation and maintenance of processing units and facilities. Where deemed appropriate DEPs are based on, or reference international, regional, national and industry standards.
The objective is to set the recommended standard for good design and engineering practice to be applied by Shell companies in oil and gas production, oil refining, gas handling, gasification, chemical processing, or any other such facility, and thereby to help achieve maximum technical and economic benefit from standardization.
The information set forth in these publications is provided to Shell companies for their consideration and decision to implement. This is of particular importance where DEPs may not cover every requirement or diversity of condition at each locality. The system of DEPs is expected to be sufficiently flexible to allow individual Operating Units to adapt the information set forth in DEPs to their own environment and requirements.
When Contractors or Manufacturers/Suppliers use DEPs, they shall be solely responsible for such use, including the quality of their work and the attainment of the required design and engineering standards. In particular, for those requirements not specifically covered, the Principal will typically expect them to follow those design and engineering practices that will achieve at least the same level of integrity as reflected in the DEPs. If in doubt, the Contractor or Manufacturer/Supplier shall, without detracting from his own responsibility, consult the Principal.
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1) Operating Units having a Service Agreement with Shell GSI or another Shell Company. The use of DEPs by these Operating Units is subject in all respects to the terms and conditions of the relevant Service Agreement. 2) Other parties who are authorised to use DEPs subject to appropriate contractual arrangements (whether as part
of a Service Agreement or otherwise).
3) Contractors/subcontractors and Manufacturers/Suppliers under a contract with users referred to under 1) or 2) which requires that tenders for projects, materials supplied or - generally - work performed on behalf of the said users comply with the relevant standards.
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TABLE OF CONTENTS
1. INTRODUCTION ...5
1.1 SCOPE...5
1.2 DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS ...5
1.3 DEFINITIONS ...5
1.4 CROSS-REFERENCES ...9
1.5 SUMMARY OF MAIN CHANGES...9
1.6 COMMENTS ON THIS DEP ...9
1.7 DUAL UNITS...9
2. BASIC DESIGN OF A LOADING TERMINAL ...10
2.1 GENERAL ...10
2.2 PEAK DEMAND...10
2.3 LOADING FLOW RATES ...10
2.4 SIMULTANEOUS LOADING USING TWO OR MORE ARMS/HOSES ...13
2.5 CALCULATION OF NUMBER OF LOADING BAYS ...13
2.6 ALLOCATION OF LOADING ARMS TO BAYS...14
2.7 PUMP CAPACITIES ...14
3. ROAD VEHICLE LOADING SYSTEMS...15
3.1 INTRODUCTION ...15
3.2 TYPICAL FLOW DIAGRAMS ...15
3.3 THE CHOICE BETWEEN TOP AND BOTTOM LOADING ...15
3.4 BOTTOM LOADING ARMS/HOSES AND COUPLINGS ...16
3.5 TOP LOADING ARMS ...17
4. FLOW CONTROL AND INTERLOCKS ...19
4.1 FLOW CONTROL SYSTEM ...19
4.2 PUMP CONTROL SYSTEM ...19
4.3 FLOW MEASUREMENT...19
4.4 CONTROL VALVES ...21
4.5 OVERSPILL PROTECTION SYSTEM ...22
4.6 BONDING INTERLOCK...23
4.7 INTERLOCK SYSTEM...23
5. AUTOMATION...24
5.1 ADVANTAGES OF AUTOMATION ...24
5.2 ASSESSMENT OF FUNCTIONAL REQUIREMENTS ...24
6. ADDITIVE INJECTION ...25
6.2 DOSING LOCATION ...25
6.3 GENERAL DESIGN GUIDELINES ...25
6.4 GANTRY ADDITIVE INJECTION SYSTEM ...25
7. VAPOUR EMISSION CONTROLS...27
7.1 APPLICATION OF VAPOUR EMISSION CONTROLS ...27
7.2 VAPOUR COLLECTION SYSTEM ...27
7.3 VAPOUR RECOVERY UNITS...27
7.4 FIRE AND EXPLOSION PROTECTION...28
8 LOADING TERMINAL DESIGN ...29
8.1 LOADING TERMINAL LAYOUT ...29
8.2 LOADING ISLAND/ BAY LAYOUT AND DESIGN ...30
8.3 GANTRY DESIGN ...31
9 MISCELLANEOUS...32
9.1 EMERGENCY AND FIRE PROTECTION ...32
9.2 PIPING ...33
9.3 LOADING PUMPS ...34
9.4 ELECTRICAL REQUIREMENTS, EARTHING AND BONDING ...34
9.5 ILLUMINATION...36
9.7 DRAINAGE AND PAVEMENT...37 9.8 PRODUCT WATER DETECTION ...37 10. REFERENCES ...38
APPENDICES
APPENDIX A PLASTIC MATERIALS ...41 APPENDIX B FIGURES ...42
1. INTRODUCTION
1.1 SCOPE
This DEP specifies requirements and gives recommendations for the design of loading facilities for bulk road vehicles for common white and black oil products. Today, these fuels may contain considerable amounts of bio components (specifically blends of gasoline with ethanol, and blends of Automotive Gas Oil (AGO) with FAME (Fatty Acid Methyl Esters)). This DEP may also be applied to other hydrocarbon and chemical products such as bitumen and solvents, however, the Principal should be consulted for such applications. This DEP clarifies the design issues and describes the hardware required but it does not cover detailed design or engineering.
This DEP contains mandatory requirements to mitigate process safety risks in accordance with Design Engineering Manual DEM 1 – Application of Technical Standards.
This is a revision of the DEP of the same number dated January 2010; see (1.5) regarding the changes.
1.2 DISTRIBUTION, INTENDED USE AND REGULATORY CONSIDERATIONS
Unless otherwise authorised by Shell GSI, the distribution of this DEP is confined to Shell companies and, where necessary, to Contractors and Manufacturers/Suppliers nominated by them. Any authorised access to DEPs does not for that reason constitute an authorization to any documents, data or information to which the DEPs may refer.
This DEP is intended for use in facilities related to oil refineries, chemical plants, gas plants, exploration and production facilities and supply/distribution installations. This DEP may also be applied in other similar facilities.
When DEPs are applied, a Management of Change (MOC) process should be implemented; this is of particular importance when existing facilities are to be modified. If national and/or local regulations exist in which some of the requirements could be more stringent than in this DEP, the Contractor shall determine by careful scrutiny which of the requirements are the more stringent and which combination of requirements will be acceptable with regards to the safety, environmental, economic and legal aspects. In all cases the Contractor shall inform the Principal of any deviation from the requirements of this DEP which is considered to be necessary in order to comply with national and/or local regulations. The Principal may then negotiate with the Authorities concerned, the objective being to obtain agreement to follow this DEP as closely as possible.
1.3 DEFINITIONS
1.3.1 General definitions
The Contractor is the party that carries out all or part of the design, engineering, procurement, construction, commissioning or management of a project or operation of a facility. The Principal may undertake all or part of the duties of the Contractor.
The Manufacturer/Supplier is the party that manufactures or supplies equipment and services to perform the duties specified by the Contractor.
The Principal is the party that initiates the project and ultimately pays for it. The Principal may also include an agent or consultant authorised to act for, and on behalf of, the Principal.
The word shall indicates a requirement.
The capitalised term SHALL [PS] indicates a process safety requirement. The word should indicates a recommendation.
1.3.2 Specific definitions
Term Definition
air eliminator A device installed in a petroleum piping system to separate free vapour to a specified level from a flowing product stream, and discharge the separated vapour either automatically or by manual venting
bay (1) area at each side of a top-loading gantry at which road vehicles can be filled at both sides.
(2) area alongside the island of a bottom-loading facility.
bio component biofuel component (in liquid form) derived from organic materials. Ethanol and FAME (Fatty Acid Methyl Ester) are examples of bio components
biodiesel diesel fuel derived from vegetable oil or animal fat consisting of long-chain alkyl (methyl, propyl or ethyl) esters
biofuel a blend of main fuel grade (typically gasoline or diesel fuel) with a bio component.
bonding the connecting together of metal parts to ensure electrical continuity
bottom-loading envelope
the positioning of road vehicle adapter connections as recommended by API RP 1004
bulk road vehicle a tank or other container mounted on a road-going chassis that is towed or self-propelled and capable of carrying petroleum products in bulk
NOTE: For road transport vehicle specifications, reference should be made to national standards.
Class I, II, or III petroleum products
the method by which petroleum products and biofuels are classified for storage and handling by their flash point temperature, in
accordance with IP-Part 2, as follows:
Class I products have a flash point below 21°C (70°F);
Class II products have a flash point between 21°C (70°F) and 55°C (131°F) inclusive;
Class III products have a flash point above 55°C (131°F) - refer to IP-Part 2.
common black oil products
class III oil products such as heavy fuel oils and residual fuel oils
NOTE: This excludes bitumen and contaminated products (e.g. products with free water, particle matter, H2S).
common white oil products
gasolines, kerosenes, gasoils and distillates of oil products with a viscosity (unheated) of less than 20 mm2/s (20 cSt) and a Final
Boiling Point (FBP) of less than 385°C (725°F) (e.g. white spirits, toluene).
NOTES This excludes:
1. contaminated products, e.g. with free water, particulate matter H2S; 2. products with true vapour pressures above 0.86 bar (12.5 psi), e.g. LPG,
pentanes;
3. very toxic substances (see DEP 01.00.01.30-Gen); 4. chemicals, e.g. ketones, alcohols, ethers, MTBE.
denatured ethanol ethanol that has been rendered unfit for human consumption (often by adding unleaded gasoline).
Term Definition
ethanol Ethyl alcohol made primarily from corn, various other grains and non grain feedstock. Ethanol comes in hydrous and anhydrous form. Anhydrous is the most pure type and is preferred for blending.
FAME – fatty acid methyl ester
FAME is an acronym for Fatty Acid Methyl Ester, the most common type of biodiesel produced from natural oil. The natural oils react with methanol and form the FAME. The type of FAME depends on the type of natural oil used (rapeseed, soy, tallow etc).
flame arrestor device used in gas vent lines to prevent the passage of flames into enclosed spaces
foot valve valve fitted at the outlet of a road vehicle tank compartment and sometimes referred to as an emergency valve or bottom outlet valve
gantry structure associated with a product supply system and provided with all equipment necessary for loading, and providing safe access to, road vehicles
hose loader assembly
system consisting of pipe, swivel and hose connection for bottom loading
loading area area comprising all filling islands and bays but excluding vehicle waiting areas.
loading arm system of pipes and swivels, balanced for easy movement, through which product is transferred from the supply pipe into a road vehicle tank
loading island area on which the equipment necessary to load a vehicle is mounted, e.g. meters, control valve, loading arms, hose loaders, control equipment etc.
NOTE: Islands can be designed for multi-product or single product loading loading terminal or
facilities
combination of one or more loading bays or gantries, including additional facilities such as parking areas, waiting lanes, dispatch office, social amenities, and the product and utilities supply piping, from the point at which the piping enters the loading area
meter pre-set control
device or system which controls the quantity of incoming product loaded into a compartment of a road vehicle, sometimes called primary level control. This may be manual or electronic
neat biofuels is the term used for pure biofuels (before any mixing with main grade fuels, such as gasoline or diesel, has taken place)
neat ethanol is the term used for pure alcohol
occupancy ratio proportion of any particular period for which the loading bay is in use for the loading of bulk road vehicles
overfill protection system installed in addition to the meter pre-set control and designed to cut off flow if the product rises above a predetermined level in the compartment of the bulk road vehicle being filled. The equipment comprises sensors in the form of thermistors, opto electronic or float-controlled reed switches, solenoid or air-operated flow-control valves, etc.
static electricity electric charge on a non-conductor or poor conductor, often caused by mechanical friction (e.g. product flow in a pipe)
ullage depth of free space left in a tank above the liquid
vapour one or more of the components of petroleum when in the vapour phase
Term Definition
vent device for the release of hydrocarbon vapour or air from pipes, tanks, or fittings, and for the entry of air
vent lines piping system for the transfer of hydrocarbon vapour or air to or from pipes, tanks, or pipe fittings, e.g. air eliminators
working platform area of the gantry structure from which the person loading the vehicle from the top operates the meters, loading arms etc., and from which access is gained to the top of the tank of the bulk road vehicles
1.3.3 Abbreviations
ADR Accord Dangereux Routier
AFFF Aqueous Film Forming Foam
AGO Automotive Gas Oil
AR Alcohol Resistant
BOL Bill of Lading
Bxx FAME mixed with diesel or AGO (xx indicates the percentage of FAME)
COPS Cross Over Protection System
CROSS Customisable Routing and Scheduling System (for Road Transport) EPA Environmental Protection Agency
ERP Enterprise Resource Planning
ESD Emergency Shut Down
Exx Ethanol mixed with gasoline (xx indicates the percentage of Ethanol)
FAME Fatty Acid Methyl Ester
IGO Industrial Gas Oil
JDE Enterprise Resource Planning System MTBE Methyl Tertiary Butyl Ether
NRV Non-Return Valve
OEL Occupational Exposure Limit
PD Positive Displacement
pS/m Pico Siemens per meter
ppm parts per million
PVC Poly Vinyl Chloride
SAP Shell Standard Enterprise Resource Planning System SDA Static Dissipator Additive
STEL Short Term Exposure Limit
SWA Steel Wire Armoured
TMS Transportation Management System
VFD Variable Frequency Drive
VOC Volatile Organic Compound
VRU Vapour Recovery Unit
1.4 CROSS-REFERENCES
Where cross-references to other parts of this DEP are made, the referenced section number is shown in brackets. Other documents referenced by this DEP are listed in (10). 1.5 SUMMARY OF MAIN CHANGES
This DEP is a revision of the DEP of the same number dated January 2010. The following are the main, non-editorial changes.
Old section
New section
Change
General General Split of document in 2 parts. In DEP Spec which contains all
mandatory requirements and in DEP Inf, its companion tha contains additional supporting information.
General Gerneral Process safety requirements have been indicated by the use of the capitalised term "SHALL [PS]"
1.6 COMMENTS ON THIS DEP
Comments on this DEP may be sent to the Administrator at [email protected], using the DEP Feedback Form. The DEP Feedback Form can be found on the main page of “DEPs on the Web”, available through the Global Technical Standards web portal http://sww.shell.com/standards and on the main page of the DEPs DVD-ROM.
1.7 DUAL UNITS
Amended per Circular 83/11
Dual units have been incorporated throughout this DEP.
This DEP contains both the International System (SI) units, as well as the corresponding US Customary (USC) units, which are given following the SI units in brackets. When agreed by the Principal, the indicated USC values/units may be used.
2. BASIC DESIGN OF A LOADING TERMINAL
2.1 GENERAL
In the design of a loading terminal, the total cost of loading vehicles should be minimised. The costs of the loading terminal include:
• capital charges for the loading facilities (e.g. gantry, structures, pumps, lines, automation system, VRU etc.).
• manpower costs for the administration and surveillance of the loading activities. • maintenance costs of the loading facilities.
The above costs should be balanced against:
• the cost of vehicle time while “in the yard”, queuing for a loading bay, occupying the loading bay and exiting the terminal.
Wherever possible, for products lighter than diesel fuel, Bottom Loading configurations shall be used for all new gantry development works including refurbishment to achieve maximum possible loading efficiency and truck utilisation, reduce group HSSE risks by improving occupational health and minimise VOC emissions to the environment.
Top loading shall only be used when bottom-loading alternatives are not available and only after carrying out an HSE risk assessment of the operations. Approved fall protections systems shall be installed and used as designed.
2.1.1 Biofuels
When introducing neat biofuels, or fuels containing biofuels, into a Terminal, there are several issues that shall be checked at the design stage, such as: product contamination; materials compatibility with piping, pump seals and vapour recovery units; reduction of conductivity with certain mixtures of FAME; product classification; type of fire fighting systems and foam required; and spill containment facilities to deal with ethanol mixtures. Usually conventional slops are fed back to refinery for reprocessing. Slops containing Ethanol, FAME, MTBE, ETBE etc. shall not be fed back to the refinery and should be treated differently than conventional slops (eg. incineration). The terminal shall implement a proper Slops Management System for oxigenized products.
At terminals, any contamination of Jet Fuels with FAME (or with diesel containing FAME) shall be avoided to ensure that the average level of FAME in a batch of jet fuel is below the maximum level as specified in DEFSTAN91-91 for Jet A-1.
FAME shall be handled using procedures that do not allow the temperature to drop below 6°C above the FAME’s cloud point to avoid formation of solids that can cause blockages of fuel lines and filters. In areas of cold climate, depots should consider whether heating of transfer lines is necessary to maintain the temperature at the correct level.
2.2 PEAK DEMAND
Any loading facility should be designed to meet the forecast loading demand during peak periods. A statistical analysis of historical figures should be the starting point, but the effects of planned improvements in methods and loading equipment and any changes likely to occur in working hours, shift patterns, vehicle sizes and types, variations in demand growth of different products, requirements for additional or fewer grades etc., shall be taken into account.
2.3 LOADING FLOW RATES
2.3.1 Determination of loading flow rate
Flow rates are restricted by the economic size of pumps, piping and measuring equipment or by the hazard of static electricity, (see 2.3.2).
High loading flow rates reduce the time spent by a vehicle at a loading gantry, resulting in the following:
(i) a reduction in vehicle idle time, i.e. standing charges;
(ii) a reduction in the bay occupancy time, which could reduce the total number of required loading bays.
On the other hand, the additional costs of pumps, larger bore piping, loading arms, flow meters and other equipment, together with increased energy consumption, shall also be taken into account.
For bottom loading, a 4-inch system should be employed (see 3.4.1).
2.3.2 Maximum flow rates of uncontaminated liquids due to static electricity hazards
If a flammable atmosphere may be present (e.g. when loading flammable products and/or when switch loading is applied), the loading velocities SHALL [PS] be determined using the flowchart in (2.3.3).
Before loading, if a flammable atmosphere may be present, the following are the key issues to be taken into account when using the flowchart in (2.3.3) to determine the safe loading speed.
1) Determine whether a flammable atmosphere could occur
2) Classify the product conductivity (≤ 50 pS/m, > 50 pS/m or unknown) (≤ 50 micromhos/cm, > 50 micromhos/cm or unknown)
3) Classify the product sulphur content (≤ 50 mg/kg, > 50 mg/kg) (≤ 50 ppmw, > 50 ppmw)
4) Detemine whether the vehicle / tanker is suitable for high speed loading
There are High Speed Loading vehicles / tankers that allow for higher loading rates and are designed to meet certain specific requirements. If a vehicle/tanker is to be classed as suitable for high speed loading, then all compartments on that vehicle SHALL [PS] be high speed loading compartments.
2.3.3 Flowchart for determining the maximum safe loading velocity for road tankers Gasoline ( or other over- rich) Flammable atm possible in compartments? vd<0.5, v<7? Conductivity? Reduce loading speed till vd<0.5, v<7 S content? High speed loading vehicle? O K t o load OK to load S content? H igh speed loading vehicle? vd<0.38, v<7? vd<0.35, v<7? vd<0.25, v<7? Reduc e loading speed t ill vd<0.38, v<7 Reduce loading speed till vd<0.35, v<7 Reduce loading speed till vd<0. 25, v<7 OK to load O K to load >50 pS/m >10 pS/m >=50 mg/kg >=50 mg/kg <50 mg/kg <50 mg/kg Yes Yes No No
Yes Yes Yes
Yes No No No No Yes No Middle distillate? Yes No =<10 pS/ m or unknown Yes No
v is the velocity in m/s and d is the internal pipe diameter in metres, and the variable (vd) is the velocity times the internal pipe diameter expressed. The variable vd is expressed in m2/s.
Flow limits
a) With a possible flammable atmosphere, conductivity ≤ 10 pS/m (10 micromhos/cm) or unknown, middle distillate with a sulphur content ≤50 mg/kg (≤50 ppmw) and
I. a non-high-speed-loading vehicle,
loading speed SHALL [PS] give vd ≤ 0.25 m2/s (≤ 2.7 ft2/s); (max. 1200 L/min (11 ft3/min) with standard 10 cm (4 in) pipework).
II. a high-speed loading vehicle,
loading speed SHALL [PS] give vd ≤ 0.35 m2/s (≤ 3.8 ft2/s) (max. 1650 L/min (58 ft3/min) with standard 10 cm (4 in) pipework).
b) With a possible flammable atmosphere and:
I. conductivity between 10 and 50 pS/m (10 and 50 micromhos/cm) and middle distillate with a sulphur content ≤50 mg/kg (≤50 ppmw); or
II. conductivity ≤10 pS/m (≤10 micromhos/cm) and sulphur content >50 mg/kg (>50 ppmw) or product other than middle distillate
loading speed SHALL [PS] give vd ≤ 0.38 m2/s (≤ 4.1 ft2/s) (max. 1800 L/min (64 ft3/min) with standard 10 cm (4 in) pipework).
c) With:
I. no flammable atmosphere; or
II. loading gasoline or other liquid that produces an over-rich atmosphere; or III. a possible flammable atmosphere; and
i. conductivity > 50 pS/m (< 50 micromhos/cm) or
ii. conductivity between 10 pS/m and 50 pS/m and sulphur content >50 mg/kg (> 50 ppmw) or non-middle distillate product or
iii. conductivity ≤10 pS/m and sulphur content >50 mg/kg (>50 ppmw) or non middle distillate product and high speed loading vehicle loading speed SHALL [PS] give vd ≤ 0.5 m2/s (≤ 5.4 ft2
/s) (max. 2400 L/min (85 ft3/min) with standard 10 cm (4 in) pipework).
Diameter d should normally be the diameter of the smallest section upstream of the tank being filled, but if the smallest section is less than 10 m (33 ft) long and has a diameter of at least 67 % of the next smallest section, the diameter of the next smallest section may be taken. This commonly allows the use of 3 inch meters (10 in ft) in DN 100 (NPS 4) bottom loading systems, where vd>0.5 m2/s (5.4 ft2/s), but pipe length is limited to around 2 m (6 ft) where flow conditioning straighteners are used.
If contaminated non-conductive liquids are loaded, the loading velocity should be limited to 1 m/s (3 ft/s). For liquids with a conductivity of more than 50 pS/m (50 micromhos/cm), no loading velocity restrictions apply for static electricity reasons, but the loading velocity should still be limited to 7 m/s (23 ft/s).
2.4 SIMULTANEOUS LOADING USING TWO OR MORE ARMS/HOSES
For top loading, the simultaneous use of two or more arms will result in the need for additional equipment to prevent overfilling which may otherwise not be necessary (see 4.5.1). The cost and other operational consequences (HSSE) arising from such equipment shall be taken into account in the economic comparison but this is not a recommended configuration for products lighter than diesel fuel.
2.5 CALCULATION OF NUMBER OF LOADING BAYS
2.5.1 General
Depending on local circumstances the design of loading facilities should distinguish between two design concepts as detailed below:
(i) the 'morning peak period' design concept, (ii) the 'waiting time' design concept.
2.5.2 The 'morning peak period' design concept
The demand in this 'peak period' has a considerable effect on the size of the final arrangement and hence shall be ascertained by consulting local staff. If all waiting vehicles have to be loaded in one hour (resulting in an average waiting time of half an hour for those vehicles which cannot be served at once), the loading facility will be twice as large as one
where all the vehicles have to be loaded in two hours (resulting in an average waiting time of one hour for those vehicles which cannot be served immediately).
2.5.3 The 'waiting time' design concept
If the arrival of vehicles is irregular, the design procedure should be based on a specified maximum average waiting time per vehicle. Such is the case, for example, in terminals operating 24 hours per day, or in terminals which try to spread the working load as evenly as possible over the working day.
2.5.4 Manual estimation of the number of loading bays required
The first step is the calculation of the 'peak period' demand; this is defined as follows for each method:
• in the 'morning peak period' method, the peak period demand is the offtake by those vehicles which queue outside the gate and which shall be loaded in the first morning period (one or more hours).
• in the 'waiting time' design method, the peak period demand is defined as the offtake during (any) one hour in a period, which has the highest vehicle arrival frequency. This period may be longer than one hour and can occur on more than one occasion in any one day.
2.6 ALLOCATION OF LOADING ARMS TO BAYS
For operational reasons, it is desirable to limit the number of loading arms at one gantry/loading bay to six. Allocation of loading arms should take into consideration the combination of products each tanker will carry so that tankers do not have to move from one bay to another during loading. Also, the product-grouping requirement (see 8.1.5) shall be taken in account.
The accommodation of more than 6 arms may be considered where product loading grouping and speciality products require single load arms. Special consideration then should be paid to access, loading envelope and drainage requirements.
2.7 PUMP CAPACITIES
2.7.1 Single loading arm
If only one product loading arm or hose is allocated for any product, a single pump rated for the maximum design flow rate of the loading system (meters, piping, loading arm/hose) should be provided.
2.7.2 Two loading arms
If two product loading arms/hoses are allocated for any product, a single pump rated for the maximum design flow rate of the loading systems for two arms/hoses, operating together, should be provided.
2.7.3 More than two loading arms per product
If more than two loading arms/hoses are allocated for any product, as a means of optimising pump numbers and sizes, a reduced total pumping capacity may be provided to allow for the time when vehicles occupy a loading bay but product is being loaded slowly or not at all, i.e. at the beginning or end of the filling cycle. By reducing the pumping capacity, the VRU and pipe work capacity may also be reduced.
3. ROAD VEHICLE LOADING SYSTEMS
3.1 INTRODUCTION
Wherever possible, for products with a flash point lower than diesel fuel, Bottom Loading configurations shall be used for all new gantry development works including refurbishment. This Section describes the choice between the two systems and the construction details of the loading arms/hoses including the provisions for vapour collection. Typical flow schemes are also presented.
3.2 TYPICAL FLOW DIAGRAMS
Figures 3.1a and 3.1b give a typical flow diagram of a bottom loading installation. A fully equipped automatic system includes the following main elements:
a) loading pump: pumps the product to the gantry to one or more loading arms (see 9.3);
b) emergency Shut Down (ESD) system and (optional) ESD valve: to isolate the loading system rapidly in an emergency (see 4.4.4);
c) air eliminators: to eliminate air from the product if there is an operational need or required by regulations. (see 4.3.7);
d) a filter or strainer: to ensure product cleanliness and to protect the flow meter and couplings (see 4.3.6);
e) additive injection system (see 6.); f) flow meter (see 4.4);
g) flow control valve: to control the flow (see 4.4);
h) loading arm connected to a dry-break coupling (see 3.4);
i) vapour return hose to VRU or to move vapours to a low risk location without receptors. (see 3.4);
j) overfill protection sensor: to give a signal if the road vehicle is overfilled (see 4.5); k) bonding connection (combined with overfill protection connection): to discharge
static electricity generated during loading (see 4.6);
l) interlock system: to prevent loading unless all conditions for safe operation are fulfilled (earth connected, no overfill, vapour return hose connected etc.) (see 4.7); m) isolation valves: to make maintenance possible and to stop the product flow in
emergencies (see 9.2.9);
n) drains and vents: to empty the system in case of maintenance (see 9.2.6); o) meter prover connections: to connect a meter prover flow meter (see 4.3.5); p) relief valves: to protect the system against overpressure, especially against thermal
expansion (see 9.2.10);
q) temperature sensors for volume correction (see 4.3.2);
r) pressure point: to enable the connection of a pressure gauge (see 4.3.5)
The flow scheme of a top loading facility is similar, apart from the loading arm and the "dead man" valve, see Figure B.1c.
Figures 3.2, 3.3 and 3.4 clarify the special symbols used for bulk road loading vehicle flow schemes.
3.3 THE CHOICE BETWEEN TOP AND BOTTOM LOADING
For products lighter than diesel fuel, bottom loading configurations should be used for all new gantry development works including refurbishment to achieve maximum possible loading efficiency and truck utilisation, reduce group HSSE risks by improving occupational health and minimise VOC emissions to the environment.
Top loading shall only be used for black oil products and heated oils in combination with a dedicated vehicle fleet. In case of switch-loading, vapour collection and treatment shall be installed, see also 7.3.1. A HSE risk assessment should be performed of the operations including but not limited to:
• OELs (Occupational Exposure Limits) • working at heights
• manual handling • escape routes
Approved fall protections systems shall be installed and used as designed. Preffered fall protections are adequate posisionned guard rails. Ropes (life lines) should be used in case existing guard rails would not offer sufficient protection against falling. Bottom loading should be employed for solvents and common white oil products.
If changing over to bottom loading is considered, the following costs should be taken into consideration:
a) vehicle conversion costs,
b) vehicle recalibration costs (see 3.4.3),
c) gantry conversion costs (bottom loading is a one-sided operation).
Top loading may be employed for the loading of black oil and heated products and for locations where operating conditions would not allow any alternative. This should be based solely on economics taking into account health/safety and future legislative requirements (Fuel Oils can be loaded via bottom fill gantries).
3.4 BOTTOM LOADING ARMS/HOSES AND COUPLINGS
3.4.1 Couplings
Liquid and vapour shear or break away couplings for loading systems and vehicles should be in accordance with API RP 1004 (or equivalent).
No widely accepted standards for nominal DN 80 (NPS 3) loading couplings are yet available. If couplings of nominal DN 80 (NPS 3) size have to be used, similar provisions to those described in API RP 1004 should be applied.
Although operational reasons may justify the DN 80 (NPS 3) size system, the DN 100 (NPS 4) API system is generally preferred due to its higher loading rates and wide acceptance.
3.4.2 Couplings for aviation products
All aviation product grades should, wherever possible, be bottom loaded into dedicated single product vehicles equipped with product-selective couplers. Selective couplings SHALL [PS] not only provide selectivity between all aviation grades, but also prevent connection to non-selective couplings at the loading facilities.
Where this is not possible, the provisions of the Shell Aviation Quality Control Manual SHALL [PS] be followed.
3.4.4 Loading arms and hoses
Bottom loading systems use either swivelling piping systems or a flexible hose system, or combinations of both, to make the filling connection and the vapour return connection between the bay and the vehicle.
A flexible hose is too heavy to handle by hand in any size over DN 80 (NPS 3) when full of product, and even in DN 80 (NPS 3) size the hose should be suspended or supported as much as possible to allow easier handling. Consequently it is a non-preferred solution and shall be avoided wherever possible.
If hoses are used these should contain a bonding wire connected to each hose end’s connection fittings for continuity.
Regardless of which type of loading arm is used, all arms/hoses etc. should be electrically conductive with a resistance less than 10 Ω .
3.4.5 Coupling location and reach of loading arms/hoses
The loading system should be designed so that connections can be readily made for multi-compartment loading, with the liquid and vapour adapters being situated within loading envelopes based on national or international standards.
3.4.7 Provisions for vapour collection
Whether or not vapour collection is required by local regulations, new/modified loading facilities and new bulk vehicles shall be designed to allow for the collection of vapour. Collected vapour should be vented to a safe location if a vapour recovery unit is not yet available.
When bottom loading, vapours SHALL [PS] be directed away from the immediate loading area to ensure persons operating/loading are not exposed to vapours though a simple vapour collection and dispersion system. This is vented in a safe area away from normal operations, buildings etc, or high enough to effect adequate dispersion.
When the terminal is operating at peak throughput, the loading gantry vapour collection system, including the vapour recovery unit, shall not generate a counter pressure at the vehicle side of the vapour collection adapter in excess of 55 mbar (0.8 psi).
Bulk road vehicles are normally not designed as pressure vessels and therefore they are not built to withstand the maximum discharge pressure of loading pumps that may arise in the event of a failure of the overfill shutdown system or blockage of the vapour return line. Each compartment SHALL [PS] therefore be fitted with a liquid relief system, capable of handling the maximum loading flow rate, so that the compartment cannot be pressurised beyond its normal working pressure. This is normally achieved by fitting a manlid, which lifts against a spring once a pre-set pressure is exceeded.
The vapour collection system fitted to the vehicle is often the limiting factor to the number of loading arms that can be connected to a vehicle at any one time during bottom loading operations. Reference shall be made to the Manufacture’s nameplate fitted to the vehicle for details of the flow limits.
3.5 TOP LOADING ARMS
Although use of top loading is discouraged, the following shall apply for cases where top loading is the only feasible option.
3.5.1 Loading arms
A wide variety of loading arm configurations is available. The main points governing selection are:
a) operation on one or both sides of the loading platform, b) loading of single or multiple product vehicles,
c) loading rates,
d) reach (design envelope) of the loading arm, e) accessories,
f) whether vapour collection is required.
The two main types of loading arms that should be employed are: a) Articulated or Scissor type arms
b) Boom type arms
Provisions should be made to secure the arms during loading. When loading any volatile product, the operator shall load from the platform and not while standing on the truck top.
The use of loading arms at both bays of a loading gantry SHALL [PS] be allowed for in any automatic interlocking earthing systems.
3.5.2 Provisions to minimise product loss and static electricity build up
To prevent evaporation and the generation of static electricity due to splashing during loading of Class I and Class II products, the loading arm or filling pipe SHALL [PS] be long enough to reach the bottom of the tank compartment to be filled. The loading arm should be provided with a T deflector at its lower end to divert flow from the vertical to the horizontal. The deflector should direct the flow to at least two opposite sides.
For Class III products, a straight filling pipe or drop tube of shorter length may be considered (to minimise clingage and drips) only if these products are loaded into dedicated vehicles. When switch loading is required, the normal Class I/II type load arm SHALL [PS] be used.
A drip bucket shall be provided for each loading arm to collect drips when the arm is stowed after use; these products should be sent to slops. Loading arms should be installed so that the contents of the arm downstream of the manual shut off-valve will drain into the filled tank compartment prior to stowing the arm. This may entail raising the height of the pedestal base flange and the use of vacuum breaker valves on the top of the load arms.
3.5.3 Provisions for vapour collection
Where vapour collection is not yet required by regulations, new and/or modified top loading loading facilities and new bulk loading vehicles should be designed for the appropriate equipment so that they may be easily converted at a later stage.
Bulk road vehicles are normally not designed as pressure vessels and therefore are not built to withstand the maximum discharge pressure of loading pumps that may arise in the event of a failure of the overfill shutdown system or blockage in the vapour line. Each compartment SHALL [PS] therefore be fitted with a liquid relief system capable of handling the maximum loading flow rate so that the compartment cannot be pressurised beyond its normal working pressure. There are 3 types of collector arrangements, see a) to c) in section 3.5.5. of the informative DEP companion. For the vapour collection arrangements (a) and (b) this can be achieved by a pressure relief arrangement which releases the manhole seal at typically 0.3 barg (4.4 pisg). For option (c) this can be achieved by fitting a man lid that lifts against a spring once a pre-set pressure is exceeded.
For top loading with vapour collection, overfill protection is required as described in (4.5). If no vapour collection systems are used for top loading, measures shall be taken to avoid OELs being exceeded (e.g. for benzene or toluene).
4. FLOW CONTROL AND INTERLOCKS
4.1 FLOW CONTROL SYSTEM
The product flow should only be enabled when all safety interlock conditions have been satisfied. The interlock system is described in (4.6).
The flow control system should start the loading operation with a loading rate substantially lower than the normal high flow rate of the loading system to avoid generating static charges that could result in an electrostatic ignition. The system should be regulated in such a way that the high flow rate is only achieved when the loading arm or deflector has been completely submerged. This will prevent splashing. This can be achieved by using a system with a two-stage flow control, with a low flow and a high normal flow. As all other components of the liquid handeling system, the flow control system SHALL [PS] be electrically connected to the loading system structure with an electrical contact resistance of less than 10Ω. At the end of the loading cycle when the required loading quantity is almost reached, say the last 150 L (5 ft3) or 200 L (7 ft3), the flow control system should reduce the loading rate (typically to 10 % of max. flow). This will ensure that the pre-set quantity will be loaded with the required precision (normally within 3 L (0.1 ft3) or 4 L (0.15 ft3)). This can be achieved, as during start-up, by a two-stage flow control. The flow control system SHALL [PS] be capable of stopping the flow in an emergency within a minimum of time, considering allowed surge pressure calculation for exsiting pipeline (pipeclass). 4.2 PUMP CONTROL SYSTEM
The pump control system SHALL [PS] be interlocked with the ESD system whereby gantry loading pumps will stop when an emergency switch or a fire/gas alarm is activated.
Pressure transmitters installed on product lines intended for use in controlling load rack flow rates should not be installed / located in the end cap or within a dead leg of the product line.
4.3 FLOW MEASUREMENT
4.3.1 Product temperature measurement
For this measurement Platinum Resistance Elements accurate to ±0.2°C (± 0.35°F) shall be used, inserted in a stainless steel thermowell. RTD (Resistance Temperature Detectors) Thermowells shall be installed into the center 1/3 of the way into the pipe and filled with a heat conducting fluid. A test thermowell should be installed in the same manner and adjacent to the RTD/Thermowell for RTD verification purposes. Coriolis meters are often provided with a contact RTD measuring the meters tubes external temperature. Use of such an RTD without a thermowell for temperature correction volumes is not acceptable.
4.3.2 Product Pressure Measurement
Pressure gauges used for pipe/small volume prover operation or pressure transmitters used for BOL (Bill of Lading) net calculations, shall be located directly upstream of the flow control valve.
4.3.3 Custody transfer requirements
Flow meters used at the points of sales (i.e. where custody transfer takes place) shall be approved for use by the local Weights and Measures Authority. Flow meters used for custody transfer may require sealing.
When turbine meters are installed, care shall be taken to assure the proper flow conditioning is achieved for proper meter operation and accuracy.
4.3.4 Meter proving
Meters, particularly those used for custody transfer, should be proved periodically to determine whether the indicated quantity in relation to actual quantity has changed as result of wear or other factors. Any inaccuracies that have developed can be corrected by adjustment of the calibrating mechanism, or by use of a factor derived from the proving runs.
Generally, bulk meters are proved 'in situ' by one of the following methods: 1) volumetric proving tanks;
2) reference “master” meters;
3) mechanical displacement provers including pipe and captive displacers. 4) small volume “loop” provers
Methods (1), (2) and (4), using mobile proving equipment, are generally applied to road loading gantry meters, with method (4) being the preferred method. It is essential that a gantry be designed to accommodate and safely operate the proving equipment. This means that suitable connections/stubs with double block and bleed valves, in between should be provided for easy connection. Double block and bleed valves should be located between the two stub connections, not on the stub. For bottom and for top loading applications with appropriate adapters, the proving valves and stubs are not required (i.e., proving is accomplished through the loading arms). Alternatively it shall be possible to correctly position a mobile proving tank in order to achieve easy and safe filling and pump out the contents. The layout of the proving system shall also allow easy and safe access to sight glasses, thermometers, registers and scales for accurate measurement.
If a meter prover is installed the following applies:
a) The meter prover SHALL [PS] be bonded to the truck and the gantry.
b) All prover components SHALL [PS] be electrically connected with a constant resistance of less than 10 Ω.
c) The meter prover SHALL [PS] not incorporate a fine filter (< 150 µm) to protect the reference meter although a coarse strainer (> 150µm) is acceptable. This is essential as there will not be an adequate residence time between the meter prover and the truck for the dissipation of any excess charge generated in the prover system.
d) Meters should be proved under conditions of temperature, pressure and flow rate closely resembling those of actual operation. This would encompass the usual delivery flow rate into a tank prover. Another acceptable consideration is to prove via pipe prover with the prover return line delivering to the transport truck. Some designs include terminal return lines where, following the proving, the fluid is delivered back to the originating tank. Further information can be found in the API Manual of Petroleum Measurements Standards – Chapter 6 – Metering Assemblies – Section 2 – Loading Rack Metering Systems.
e) Meters should be proved with products having a viscosity similar to those for which they are normally used.
f) When using proving equipment, there is always a chance of introducing air or vapour into the system. Air or vapour shall be eliminated before proving.
g) Since product and proving equipment temperatures and pressures have to be taken into account, thermometers and pressure gauges traceable to the local standards organization shall be used for accurate measurement.
h) To ensure proper operating performance, meters should be installed according to manufacturers’ recommendations. Make certain that any areas that may trap or build up with debris are avoided. Avoid installing the meter at high point in the piping to prevent trapping air in pockets and causing problems with equipment and perhaps creating safety issues.
i) Standard national or internationally accepted equipment and procedures shall be rigorously adopted.
j) In the absence of clear national procedures the guidelines given in the EI Petroleum Measurement Manual Part X (Meter Proving), or Petroleum Measurement Paper Number 4 “Code of Practice for the Proving of loading Gantry Meters” should be followed. Alternatively, API MPMS 4.1, 4.2, 4.4, 4.5, 4.6, 4.8 and 5.6 may be applied.
4.3.5 Filters/Strainers
Where fuels are loaded through a micro filter or filter water-separator, the residence time of the liquid in the line between the outlet of the filter and the receiving tank should be sufficient for any exess charge they generate to be dissipied before the fuel reaches the receiving tank. The maximum velocity of the liquid in the line should be determined in accordance with section 2.3.3.
4.4 CONTROL VALVES
4.4.1 Manual product start/stop control valves
In traditional top loading a 'deadman control' in the form of a 'hold-open' valve SHALL [PS] be provided. This enables the operator, when filling through an open manhole, to watch the level of the product and to stop the flow immediately in an emergency. The valve-operating lever (or control rod) shall be located so that the operator can see the product in the compartments at high level, while avoiding the vapour plume emitted from the manhole. Where operators operate from the loading platform, rather than the top of the truck (e.g. as a means of reducing exposure to vapour emissions) alternative arrangements featuring electronic deadman systems for use in top loading SHALL [PS] be applied.
4.4.2 Automatic flow control valves
In the design of the system the surge pressure due to rapid closure of the control valve SHALL [PS] be taken in account (see 4.4.5).
4.4.3 Flow-limiting valves
At non-automated loading gantries, flow-limiting valves SHALL [PS] be fitted on each of the loading arms because pump output is not controlled to match product demand. These valves are used to protect equipment against excessive flow rates, which can occur when only one loading arm out of several delivering similar product is used and more than the required number of pumps are running.
4.4.4 Emergency shutdown (ESD) valve
In unmanned terminals or other terminals with increased risks due to spillage (e.g. terminals in built-up residential areas or large terminals) an additional ESD valve SHALL [PS] be included.
In the design of the system the surge pressure due to rapid closure of the ESD valve SHALL [PS] be considered (see 4.4.5).
4.4.5 Surge pressure
The piping system shall be designed to allow for the maximum surge pressure expected, see DEP 31.38.01.11-Gen.
To reduce the maximum surge pressures and thus the design pressure of the pipe system, the following measures shall be considered:
• Slow valve closure
Typically shutdown systems closure time shall be minimized. The closing time shall be set considering allowed surge pressure calculation for exsiting pipeline
(pipeclass). The valve closing time has an impact on the filling level of the vehicle’s compartment and therefore the compartimet hullage shall be reconsidered in order to avoid spills. See also 4.5.5.
• Valve characteristic • Pressure relief systems • Surge pressure alleviator
A flanged tee should be installed upstream of the ESD valve, to facilitate installation of an alleviator if surge pressure is found to be a problem.
No surge pressure alleviator shall be installed between a PD meter and the control valve, because this will result in extra pulses being generated by the pulse transmitter as the alleviator first absorbs product and then pushes it back down the line. In such cases the alleviator (or 'T' piece) should be installed directly upstream of the PD meter.
• Limiting the liquid velocity
Loading systems should be designed to operate at the maximum safe flow limits to avoid build up of electrostatic charges. The design should also contemplate the loading system to withstand an emergency closure surge pressure impact 4.5 OVERSPILL PROTECTION SYSTEM
4.5.1 Necessity of overfill prevention systems
For all closed systems where it is not possible to monitor visually the liquid level (i.e. for bottom loading and top loading with vapour collection), an overfill protection system SHALL [PS] be installed.
4.5.2 Overfill protection systems
Floaters and displacers SHALL [PS] not be employed for overfill protection.
Air reaction systems shall be limited in use to special applications such as liquid sulphur or bitumen.
4.5.3 Ullage of compartments and valve closure time
The total elapsed time between the high level signal initiated by the liquid level control sensor and the final closure of the valve SHALL [PS] be such that there is no possibility of a spill over from compartments. However, in order to minimise the shock pressure (surge) in the piping system due to valve closure, it is often necessary to slow down the valve closure, (see 4.4.5). Hence the quantity of product that passes through the valve during the closure period SHALL [PS] be taken into account when setting ullage in vehicle compartments, especially in those with small capacity.
The response time of the overpressure protection system is either constrained by pressure surge considerations or by the instrumentation. Where the resulting ullage requirements cannot be met, one or more of the following options shall be explored:”
a) plan for the elimination of small compartments;
b) use hydraulic analysis of the loading system to minimise the likelihood of pressure surges. If high pressure surges cannot be avoided, consider fitting flow control valves with 'equal percentage' characteristic to reduce surge pressure;
c) downrate the compartments of existing vehicles where required by the amount necessary for safe liquid cut-off;
d) allow for appropriate ullage in the design of new bulk vehicle compartments.
4.5.4 Requirements for design and maintenance of overfill systems
Overfill systems, including connectors and connector envelopes, should be designed according to a recognised standard such as the IP “Code of Practice for Bottom Loading, Vapour Collection and Overfill Prevention”.
Sensor systems should be fail-safe, i.e. not permitting loading in case of failure. This may be achieved by using self-checking systems.
Sensing probes SHALL [PS] be suitable for use in petroleum products and electrical/electronic probes SHALL [PS] be certified safe for operation in Zone 0 when connected to a certified controller. The wiring for the sensing probe system on the vehicle should be both physically and electrically isolated from other vehicle circuits, by the use of dedicated conduits and vehicle boxes.
4.5.5 Consideration for liquid detectors in vapour return lines
The VRU system shall be provided with means to collect and drain condensate from low points in the system.
The sump shall be equipped with a high-level switch which activates an alarm and the VRU ESD, as well as being fitted with a means to test the operation of the switch and a suitable drainage point. A sight glass should be installed in the sump.
4.6 BONDING INTERLOCK
A bonding cable SHALL [PS] be connected to the vehicle before any other operations are carried out (e.g. opening manlids, connecting hoses etc.). The bonding resistance between the vehicle and the gantry SHALL [PS] be less than 10 Ω, and this bonding SHALL [PS] remain in position until all other loading operations have been completed.
Loading SHALL [PS] not be permitted by the flow control system/interlock system if the vehicle is not bonded effectively. If an overfill protection system is provided, the overfill protection connection should be combined with the earthing connection.
The driveaway traffic light turn green and/or the exit barrier shall only open after the bonding cable has been disconnected. A similar requirement exists for:
• the safe storage of the loading arms, if applied (see 3.4.6);
• the position of the ramps providing access to the top of the road truck (see 8.3.2.2). For non-automated loading gantries (e.g. top loading with mechanical pre-set), the bonding cable between the loading facilities and the road car SHALL [PS] be clearly visible and equipped with a status warning light indicating its connection/non-connection to the road car. Further information can be found in: API RP 2003 Protection against ignitions arising out of static, lightning and stray currents and NFPA 30 Flammable and combustibles liquids code.
4.7 INTERLOCK SYSTEM
On the vehicle the following interlocks shall be considered:
a) driveaway interlock, e.g. a lift bar normally covers all product connections: when lifted the brakes are applied.
b) air pressure interlock: a pressure switch contact should be connected to the overfill detection system, so that a loss of vehicle air pressure will cause the gantry loading valve to be closed.
c) vapour vent interlocks: the vapour vent valves which connect each compartment to the vapour collection manifold on the vehicle should be open before loading is permitted.
d) verification of vapour collection connection: a proximity switch contact shall be connected to the overfill protection system so that loading is only permitted if the vapour collection connection is made.
5. AUTOMATION
5.1 ADVANTAGES OF AUTOMATION
Automation offers many advantages over manual systems. New installations shall be automated and the automation of existing installations should be considered at the earliest opportunity. Automation should be fit for purpose and follow a standard approach in terms of vendor, system functionality and implementation.
5.2 ASSESSMENT OF FUNCTIONAL REQUIREMENTS
6. ADDITIVE INJECTION
6.2 DOSING LOCATION
Before it is decided to inject additives at the loading gantry the advantages and disadvantages of dosing at other locations should be considered.
When loading gantry dosing is selected, the following aspects shall be implemented: • a secure additive selector system (automatic selection is preferred to manual or key
selectors);
• the injector control system to incorporate a feedback signal that confirms that dosing is taking place. If dosing does not take place within the specified limits, loading should be interrupted;
• additive volume totaliser meters, in order to enable a periodic check on the correct injection ratio (at least daily, but preferably at the end of each shift).
6.3 GENERAL DESIGN GUIDELINES
6.3.1 Additive type
The pump seals should be compatible with the type of additives to be used.
6.3.3 Injection methods
When different additives can be selected, care should be taken to avoid cross-contamination of additives. For these applications modified flow-proportional additive injection should be employed. With this method no additive is injected during the final amount (say 200 L) (say 7 ft3) of the batch, thus leaving the loading linework purged of all additivated products.
6.4 GANTRY ADDITIVE INJECTION SYSTEM
6.4.1 Additive receipt facilities
To ensure that the correct additive is safely discharged and received into the right storage tank the following measures shall be taken:
a) vehicle/rail discharge points shall be clearly marked to identify the additives in accordance with their delivery documents;
b) the systems for different types of additives and additives of competitors shall be kept completely segregated. Thus separate connections and pumping systems shall be used. Valve cross-overs shall be avoided. Dedicated connections should be employed wherever possible.
6.4.2 Additive storage vessel
Pre-mixing of the additive by the supplier makes the on-site operating procedure simpler, but could add to the transportation costs. If mixing on site is selected then the quality control procedures shall be defined.
Care should be taken with the maximum storage temperature of many additives, in particular ignition improvers. Temperature alarms SHALL [PS] then be provided, as well as e.g. water-spray cooling for fire protection or the use of underground storage tanks.
Tank mixers and tank filling/draining facilities shall be provided.
For storage of light additives, pressure/vacuum valves should be fitted to prevent emissions. For storage and handling of very toxic additives DEP 01.00.01.30-Gen and DEP 31.38.01.11-Gen. shall apply.
Means of establishing the amount of additive in the storage tank (dipping or level gauging) shall be provided to allow reconciliation of stocks.
6.4.3 Injection system
The following Injection systems may be applied. Requirements depend on the system selected:
• Electronic injector systems
The additive piston injector should be fitted with a proximity sensor, which sends feedback pulses to the controller, thus confirming that the injector is operating correctly. Depending on the control system these systems are capable of ‘modified proportional injection’ (e.g. line clearing).
• Electronic flow-proportioning control • Pneumatically driven injectors • Turbine driven injectors • Mechanical systems • Gantry Blending
Where blending is performed downstream of the final meter, the blending component meter shall be considered as a custody transfer meter and tested accordingly.
6.4.4 Injection nozzle
The additive injection point shall be positioned upstream of the flow meter.
The simultaneous injection of multiple additives/components at the same location in the pipe shall be avoided to assure a homogenous mixture
7. VAPOUR EMISSION CONTROLS
7.1 APPLICATION OF VAPOUR EMISSION CONTROLS
For common white products, the vehicle loading gantries shall be of the bottom loading type with vapour collection systems and existing top loading facilities shall be converted into bottom loading during a defined conversion period. Such conversion periode should be minimized to ALARP.
For black oil products and heated oils, top loading gantries are allowed and do not require vapour collection and recovery, provided a dedicated vehicle fleet (no switch loading) is used. In case mixed vehicle fleet is used, vapour collection and recovery shall be applied.
7.2 VAPOUR COLLECTION SYSTEM
The requirements depend on the system selected: • Direct system
With bottom loading of road tankers the vapours from all compartments will be collected, including those from non-gasoline loading (e.g. automotive gasoil). These additional vapours, plus the vapours generated during the loading itself (e.g. by evaporation of the product), shall be taken into account when sizing the vapour collection and vapour recovery unit or incinerator.
• Direct system with vapour holding tank
The vapour holding tank shall be protected against over-and-underpressure. If a flexible diaphragm is used in the holder then its material shall be compatible with the composition of the vapours and it shall be designed to eliminate static electricity hazards.
• Vapour balancing system
• Design of vapour collection systems
Vapour collection systems should be designed and sized according to the IP “Guidelines for the Design and Operation of Gasoline Vapour Emission Controls” or equivalent API Standard. The vapour collection system SHALL [PS] be adequate to cater for the highest loading rate anticipated at the loading gantry, including
displacement from gasoil compartments on mixed loads in multi-product gantries. In direct systems the vapour generation in product tanks due to ambient
temperature changes and solar radiation should also be considered. 7.3 VAPOUR RECOVERY UNITS
The main types of vapour recovery units on the market are: • Carbon adsorption
• Liquid absorption
• Refrigeration/Condensation • Membranes
7.3.1 The choice of vapour recovery unit
The different types of units have different fields of application. The following should be taken into account in the choice of a VRU:
a) throughput profile (peak, 15 minutes, hourly, four hourly and daily capacity); b) required outlet concentration;
c) type of vapours to be processed (only gasoline, or also diesel, solvent, chemicals, additive, ethanol or MTBE vapours);
d) consumption of energy, utility and other consumables (anti-icing additives, absorption liquid, carbon, glycol etc.);
e) availability of utilities at the site (steam, electricity, cooling water, hot oil, sewage system, absorption liquid, instrument air, nitrogen etc.);
f) simplicity of operation and maintenance;
g) environmental aspects (waste water, spent active carbon, refrigeration medium); h) accuracy of recovered gasoline measurement (to allow the prepaid duty on the
recovered gasoline to be reclaimed);
i) experience of and technical back-up (service organisation / spare parts) supplied by the Manufacturer;
j) safety.
k) materials compatibility with products being recovered.
7.3.2 Design of VRUs
VRUs should be designed and sized according to the IP “Guidelines for the Design and Operation of Gasoline Vapour Emission Controls”.
Area classification SHALL [PS] be in accordance with IP-Part 15 or alternative recognised codes. The electrical requirements SHALL [PS] be in accordance with (9.4).
Most Manufacturers build their VRUs according to a standardised design. If a Manufacturer’s design is proven in practice in similar situations, that design should be adopted (as far as possible) in order to avoid redesign which would result in excessive cost and the risk of improperly functioning units.
7.4 FIRE AND EXPLOSION PROTECTION
The vapour collection system SHALL [PS] be protected from internal fire and explosion. To limit the consequences of an ignition the following techniques or a combination of them shall be applied.
• Containment • Explosion venting
Explosion venting should only be applied if no other feasible alternative exist. The vents should be placed at intervals less than the predicted run-up distance to detonation and should be at least equal to the cross sectional area of the pipe. In normal operation the discharge of flame and pressure from the pipe can be
considerable; therefore great care should be taken with the location of the vent and the direction in which the flame will be released.
• Active explosion suppression or isolation
Due to their complicated design these techniques should not be employed. • Flame and detonation arresters
In the design of the vapour collection system the often considerable pressure drop of flame arresters shall be taken into consideration and an extra allowance for fouling of the flame arresters shall be made.
Flame arresters SHALL [PS] have been demonstrated to work under actual conditions and SHALL [PS] have been tested to an appropriate standard, e.g. BS 7244 or EN 12874.
• Risk assessment and cost effectiveness of protection
Especially for large installations (more than 4 connected loading bays or more than 8 connected tanks) a Quantitative Risk Analysis study should be performed to determine the most cost effective arrangement of detonation arresters.
