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AUTOMATED TRUCK LOADING SYSTEMS

Class # 2030.1 Shoyeb Hasanali Emerson Process Management 12603 Southwest Freeway, Suite 100 Stafford, TX 77477 Introduction Function of bulk marketing storage facilities known as distribution terminals, is to facilitate distribution of liquid products from storage to trucks (also railcars, barges, pipeline). Safety, Security, measurement accuracy, regulatory and reporting requirements are the key driving force in automation of loading terminals. Over the years due to EPA regulations and cleaner fuel acts it has become essential to mix products for making, as an example, mid-grade fuel. Fuel additization became essential where a small percentage of additive had to be added to fuel. For terminal efficiency and cost it became essential to come up with techniques to blend products at the loading rack instead of having to store in tanks. Also it would make more sense to inject additive into the product stream as opposed to physically add additive into compartment at end of load. An integrated blending and additizing control system in terminals became essential not only for realizing efficiency, but also have a system that is configurable and can adapt to blending ratio changes additive percentages adjustments and accurate mixing to obtain on specs. final product for distribution. Integration of modules such as tank levels and inventory, terminal and loading gantry secured access, safety circuit monitoring and transaction management became essential to centralize the overall terminal operation. Blending products such as gasoline, diesel and fuel oils with variable percentages have become a common place for formulating gasoline to cater to different commercial and industrial needs. In the recent years due to increase in crude oil prices and dependency on foreign oil, ethanol blending is becoming common. Ethanol is produced off corn and soybean and reduces overall gasoline contents. A 10% mix of ethanol in products is becoming a common at the gas pumps. Due to increase in cost of running and maintaining terminals many terminal operating companies are consolidating terminals and operating as joint venture terminals. To cater to the demand, terminals have to be efficient and have to remain open more than a single 8 hour shift, in some cases open 24/7. Automation allows terminal to operate un-manned during non-business hours. Automation of a terminal involves efficient integration of different stand-alone equipment. comprehensive list of equipment that makes up a terminal: · · · · · · · Product Receipt/Metering Control valves to store product receipts in their respective tanks Tank level and measurement device Fire Hydrant Systems Security Access Gantry Automation equipment such as strainer, meter, flow control valve, preset Terminal management software Following is a

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Although a complete automation system consists of the above equipment, this paper will focus on the measurement and control instruments for the loading gantry and how it is tied up with the terminal management application software. Background Automation at Marketing Terminals began in the early 1970's as a result of increasing prices of Crude oil and the demand for safe operating conditions. The early automation systems were comprised of positive displacement (PD) meters with mechanical presets and ticket printing devices. Automatic temperature compensating devices on mechanical meters were incorporated for stock reconciliation at reference conditions.

G A LL LL O N S G A O N S

S S E E T T

SS T T OO P P

AUTO MATIC AUTOMATIC TEMPERATURE TEMPERA TURE CO MPENSA TOR COMPENSAT OR

Mechanical

Electronic (Utilizes the Electronic Preset)

Figure 1 As terminals grew in the early 1980's and invent of electronics smarter instruments emerged. Electronic measurement of flow and totalization started replacing high maintenance and costly mechanical stacks on the PD meter with electronic pulse output meters and electronic batch controllers called presets. This not only reduced cost and maintenance but improved the accuracy and performance of the meter. Higher throughput and increased repeatability made turbine meters the obvious primary metering instrument choice and electronic preset replacing mechanical totalizers as a set point device for batches and totalizing.

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Figure 2 With an increase in awareness, strict environmental regulations (Clean Air Act Amendments of 1990 in the US) and the production of cleaner fuel, terminals went through upgrades to meet the new regulatory requirement. Component blending which was primarily a refining function was now being done at the point of distribution. The prime factors responsible for the high level of automation at the loading terminals were: · · · · · · · · · Efficiency Safety Security Flexibility Accuracy Ease in Operation and Maintenance Data Availability Increased Productivity Reduced Cost of Ownership

Areas of Automation in Loading Terminals The areas of terminal automation are: · Metering and Control · Product Blending · Additive Metering · Security Access (business permissive) and Safety Interlocks · BOL, transaction management, audit trail and MIS reporting Electronic Preset is capable of handling most of these functions and total control of the gantry loading. Metering and Control: Selection of primary metering components largely depend on: · Types of products to be handled (viscosity, loading temperature, etc.) · Flow throughput rates · Accuracy

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· ·

Batch measurement (Mass or Volumetric) Local approvals

For the majority of petroleum applications, volumetric metering devices such as positive displacement meters and Turbine meters are commonly used. For mass measurement mass flow meters are being used. Traditionally, gantries were equipped with Positive Displacement meters utilizing mechanical stack-ups to perform the many functions required at the gantry. Mechanical stack-ups are being replaced with electronic presets that allow temperature compensation via temperature probes wired into the preset. Positive displacement meters have gone through many enhancements as provision for extremely low torque (hence low pressure drop), low pulse frequency variation (with direct pulse output without mechanical linkage between the rotor and a pulse generator) and increased durable material used in construction of the meter. Positive displacement meters are still commonly used for measurement of high viscous products. Turbine meters are still the preferred metering device for refined products. Their simple design can provide sustained accuracy over a wide flow range. Typically, a turbine meter maintains an accuracy of ±0.15% over a 10:1 turndown for 0.3 to 3.0 cst viscosity. Accuracy is further improved by meter linearization in the preset. Also, newer approaches to flow conditioning (such as the flow conditioning plate) have considerably reduced the installation requirements for Turbine meters. Turbine meters are a low cost meter that offers a high throughput rate. Mass metering may be required for both products with low vapor pressure such as Propane, Butane, Ethane, etc., and higher viscosity products. Some countries also have regulations to use mass units for custody transfer of fluids. The conventional method to accomplish this is to convert the volumetric units into mass units by applying the VCF (Volume Correction Factor) and Density in the preset which is verified by weighing trucks on scales. However, recent advances in metering technology have resulted in development of direct mass measuring flow meters that operate on the Coriolis principle. Unique design (no moving parts) and high accuracy (±0.1% over 10:1 range) have made Coriolis Force flowmeters a preferable choice in gantry loading applications. Coriolis Force Flowmeters (CFM) also helped provide a substitute to bearing dependent PD and Turbine meters. Coriolis meters are also used in high viscosity applications like asphalt, dyes and detergents. The Coriolis meter is not limited to mass but can also be used as a non-intrusive volumetric flow meter. Control Valve: A hydraulic line actuated, balanced piston operated valve with solenoids is used for flow control and flow profiling by electronic presets. Precise flow control, low pressure drop and reduced maintenance are key features of today's control valves - commonly known as the digital control valve. Metering Accessories: In-line strainers and air eliminators are installed to assure that only product free of entrained air and foreign materials passes through the meter. Differential pressure switches are installed to determine the cleanliness of the strainer. The output from the DP Switch is connected to the electronic preset as an annunciation feature and can be configured to stop the loading process if required. In such a condition, the electronic preset will prompt the operator with a message to clean the strainer. Blending of Product: A typical terminal blending operation consists of mixing of two or more components, the mix being predefined in a given product recipe. The percentage of each component in a recipe depends upon the final desired product. Blending at gantry prevent economic losses due to quality giveaways of octane and in not meeting market demands because of inadequate product inventory due to shortage of storage tanks, etc. As a result of new mandates and market driven requirements, terminals have turned to blending at the gantry as an economical and viable means of complying with these stringent and ever changing requirements. Since blended products are loaded in tank trucks (also railcars, ships/barges), incorrect (out-of-spec) blend results in quality giveaways and/or product loss. High penalties are imposed by regulatory authorities (W&M, EPA, etc.) for out-of-spec blends.

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Electronic Preset

Blending Management Ratio / Sequential

Figure 3 Two principles are available for blending applications at the terminal: Ratio (In-line) and Sequential. Each method has its distinct advantages. Selection of blending method depends largely on economics and logistics (quality requirements, regulation, etc.). The product quality and exact procedure for blending can be specified by way of a Recipe. Electronic preset allow for configuring of multiple recipes which can be selected by the operator/driver prior to loading. In Sequential blending, each component is loaded one at a time into a single compartment to produce a blended product. Each product will have a product selector valve, but shares common metering. Blend quality is assured only if the total batch is completed. The Electronic preset has the enhanced capability of sequential blending by: · automatic control (with or without feedback) of product selector valves · meter factors (with linearization) of each base product · independent temperature compensation methods for each base product · blend accounting and · line flush to assure quality of product. In-line or Ratio blending is usually proportional, which ensures blend accuracy at any given time during batch loading (homogeneous mixture). Each component has a separate metering and control system. The electronic preset offers various blending options, such as, all-stage blending, high flow only blending, cyclic blending, etc. which can be selected depending upon the percentages of individual products and flowmeter ranges. This is essential to maintain the flowrates of individual meters within their accuracy limits. In the case of a fall in line pressure, the preset offers the unique feature of flowrate fallback and automatic recovery. Selection of the type of blending to be used depends primarily on the blend accuracy considerations, local Weights and Measures (W&M) regulations, etc. Tradeoff is usually on consideration of having precise blend at any given time during the loading versus the initial cost of installation. In general, ratio blending has emerged as a choice of preference limited only by economic considerations. Additive Metering and Control: Additive Injection is squirting a very small quantity of product enhancers, detergents, dyes, etc. in the main product. The recent mandate by the EPA to periodically provide Volumetric Additive Reconciliation (VAR) reports and prove the additive meters increased the functional responsibility of the electronic preset. The requirement becomes more complex for injecting multiple additives in a single batch (e.g. generic and branded additive injection in gasoline). The handling of large numbers of additives at a given loading point is increased due to the throughput terminaling by major oil companies. Along with other parameters, the product recipes stored in the electronic preset now specifies the percentage composition of base products, additives and their injection rate. The preset loading system in conjunction with a security access system can support recipes for various suppliers and provide the desired selection to the operator/driver to continue loading without impacting the driver's loading time.

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Types of additive injection/metering systems include: · · · · · Conventional cylinder type injectors (with or without feedback) Conventional injectors with meter for totalization Additive metering panels Multi-component additive metering systems Electronically controlled additive metering systems

Since the loading terminals have different types of injection systems installed for different additives, the electronic preset should be capable to simultaneously handle all of the above types of additive injection systems.

Additive Pump

Electronic Preset

Solenoid Coriolis Meter Check Valve

Base Product

Figure 4 The electronic preset is designed to manage large number (up to 10) of independent additives and control the injection as specified in the recipe. Historically, calibrated cylinders with actuated pistons were used for additive injection. The electronic preset would output the control pulse after certain amount of base product is dispensed. To provide better control, pulse output type meters (e.g. oval gear meters) are used for additive injection. For certain applications, owing to material compatibility and the high viscosity of some additives and dyes, Coriolis meters are gaining popularity as additive injection meters. The electronic preset controls the additive injection and allows the printing of the additive data on the bill of lading in desired units (conversion of units is done by the preset). Today's electronic preset provides unique features like different injection rates per recipe, precise accounting of additives (useful for meeting Volumetric Additive Reconciliation requirement by Environmental Protection Agency in the US), meaningful Volume based alarms, etc. This distinct feature of the electronic preset provides better flexibility, ease in operation, optimum control and reduced installation cost over electronic injection systems. It is a proven fact that the electronic preset as a self-contained unit, improves handling of the blending and additizing process. For optimum reduction in installation cost, the electronic preset is capable of handling multiple additive streams through a single meter. A multiple additive metering feature with line flush capability and separate additive accounting provides distinct advantages and prepares the marketing terminal for compliance with future regulations.

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The electronic preset offers the unique ability to be responsive to change in an operational environment. Access Security and Safety Interlocks: Access security, loading authorization and safety interlocks form an important part of terminal automation. The driver and loading authorization is usually done through Magnetic Card readers situated at the terminal gate or at the gantry. The card readers can be connected to the presets or to the computer system for data logging. The electronic preset can be configured to provide extra security by prompting the driver/operator to enter a Personal Identification Number (PIN) and other auxiliary data for validation and data logging. A sophisticated vehicle identification system can be installed which reads truck ID and verifies approvals, compartment sizes, ownership and approval status and material compatibility (by verifying last product carried) in the central computer database. Safety interlocks like vehicle grounding, overfill protection, vehicle brakes, etc. can be monitored by the electronic preset as permissives. The electronic preset can handle up to 4 discrete permissives from different safety interlock devices and will prompt the operator to connect the interlocks, monitor them on a real-time basis and stop loading upon non-compliance. Printing/Data logging/MIS interface: Printing a Bill of Lading ticket (BOL) is one of the most critical tasks at the terminal. It was achieved earlier by mechanical printers driven by mechanical counters. This was replaced by pulse driven ticket printers with outputs from an electronic preset. With advances in electronic preset technology, a single serial port printer can be multidropped with 32 preset units and print the user configurable printing tickets, event logs, etc. Special printing characters and local languages are also supported to comply with local regulations in various countries. Increased data requirements and on-time availability of terminal data has promoted use of higher end multitasking (RISC based) workstations and relational databases that support all data access and reporting. Operator screens consist of menu driven, user interactive and graphic screens. Touch screen type interaction terminals are being installed at loading racks for access security and monitoring purposes. The Computer systems at different terminals are connected to a central mainframe computer through leased lines assuring almost instantaneous interaction. Up to the minute inventory balances, transfer of bill of ladings and invoices, product movements and tracking terminals deliveries can be efficiently carried out by a central mainframe computer. Ease in operation and maintenance of the system is most important as downtime of a loading terminal can result in loss of business. Unique features such as remote maintenance and diagnostics can improve the serviceability of the electronic preset. On-line technical support performed by qualified technicians and factory trained service personnel can troubleshoot the preset over standard telephone lines. Summary With the superior features offered by today's electronic preset and flow metering systems, loading racks are able to maintain higher throughput capacity with fewer load spots. Product accounting and balancing has improved drastically with highly accurate metering instruments and presets. MIS systems offer almost instantaneous data availability and have drastically reduced cumbersome paperwork and the time of drivers. The electronic preset acts as the hub of the modern terminal automation system by providing highly flexible and real-time control to most critical tasks. It enhances the operation of the metering system by applying appropriate correction factors. Selection of the electronic preset plays a most important role in any terminal operation as it must ensure the properly integrated operation of the terminal as well as provide the flexibility to meet future requirements.

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Access Security

Serial Communications to Automation / Business Systems

Printing Data Log BOL

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2 7

3 8

4 9

5 0

STAR T STO P

Remote Communications for Troubleshooting Diagnostics Ratio and Sequential Blending

Additive Management System

ELECTRONIC PRESET

VCF = Ctl * Cpl

VCF Calculation Flow Compensation

Flow Control and Batching

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AUTOMATED TRUCK LOADING SYSTEMS

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