DP 24-24-1 Additive Systems

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 1 of 10 Rev. 3

Apr., 1999

TABLE OF CONTENTS SCOPE..........................................................................................................................................................................2 REFERENCES ..............................................................................................................................................................2 NOMENCLATURE.........................................................................................................................................................2 ADDITIVE ...............................................................................................................................................................2 BLENDING .............................................................................................................................................................2 CAR SEAL OPEN (CSO).........................................................................................................................................2 INJECTOR..............................................................................................................................................................2 RISER ....................................................................................................................................................................2 PRESET .................................................................................................................................................................2 BACKGROUND .............................................................................................................................................................3 EXXON COMPANY, U.S.A., ADDITIVE POLICY.............................................................................................................3 ADDITIZATION HISTORY..............................................................................................................................................3 SYSTEM COMPONENTS ..............................................................................................................................................4 SYSTEM.................................................................................................................................................................4 RECEIVING FACILITY ............................................................................................................................................4 STORAGE TANK....................................................................................................................................................4 SUPPLY PUMP ASSEMBLY ...................................................................................................................................5 PIPING SYSTEM ....................................................................................................................................................5 INJECTORS ...........................................................................................................................................................6 INJECTION LOCATION .................................................................................................................................................6 INJECTION VOLUMES..................................................................................................................................................7 VISCOSITY IMPACT .....................................................................................................................................................7 FIGURE 1 ADDITIVE SYSTEM FLOW SHEET ...............................................................................................................9 REVISION HISTORY ...................................................................................................................................................10

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 2 of 10 Rev. 3

Apr., 1999

Changes to the previous revision are marked with an → . SCOPE This Design Practice covers additive injection systems utilized at Exxon Company, U.S.A., Marketing Distribution Terminals. REFERENCES See the following Design Practice and Engineering Practices for additional information: → DP 22-22-10

Terminal Layout and Spacing

→ EP 9-9-2

Small Vertical Aboveground Atmospheric Storage Tanks

EP 15-24-1

Instrumentation for Additive Systems

EP 23-24-1

Additive Receipt

EP 24-22-10

Additive System Design and Layout

EP 24-24-1

Additive Injectors

EP 24-24-2

Skid Mounted Portable Additive Systems NOMENCLATURE

ADDITIVE Small quantity (less than 3%) of chemical or dye added to motor fuel(s) to enhance performance, or to provide identification for tax purposes. BLENDING Process of combining multiple components into a finished product. Typically the components are in amounts greater than 3% and are not injected in small quantities. CAR SEAL OPEN (CSO) A method of adding a locking device or tag to a valve's handwheel or quarter turn lever to prevent accidental closure of the valve. INJECTOR Device for proportioning the amount of additive to the fuel stream. RISER The related devices located in a meter run to an individual loading arm. PRESET A generic term that describes the equipment that allows the setting of a volume to be delivered to a truck and then automatically stops flow when complete.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 3 of 10 Rev. 3

Apr., 1999

BACKGROUND The use of fuel additives satisfies two important needs: •

Marketing Strategy

•

Governmental/Environmental Requirements

Additives improve vehicle performance and reduce emissions, or identify fuels. They are the prime component which distinguishes one brand of Mogas from another and are used as a prime marketing tool. Governmental/environmental requirements which are directing additive use were initiated by the California Air Resource Board (CARB). CARB dictates basically that all gasoline sold in the state of California shall be additized and records certifying this shall be kept. Recent federal legislation also requires distinguishing between low sulfur and regular sulfur diesel fuels; that is done via dye injection. The Clean Air Act of 1990 followed CARB's lead and mandated the use of additive in all gasolines by January 1, 1995 and requires: •

Compliance

•

Record-Keeping

•

Penalties for noncompliance EXXON COMPANY, U.S.A., ADDITIVE POLICY

Exxon Company, U.S.A., policy states that all Exxon branded gasoline, including that received under purchase and exchange agreements, shall contain approved additives in quantity and type to provide the quality features required by Exxon's Motor Gasoline Quality Policy. Guidelines for compliance with this policy are as follows: •

Proprietary additive is required in all gasoline sold as branded Exxon product.

•

Proprietary additive shall not be in gasoline sold as unbranded product. A "generic" additive will be required.

•

Proprietary additive shall not be in gasoline supplied to exchange accounts or delivered to parties for whom Exxon provides terminaling service.

•

Mechanical injection equipment must be installed at all locations requiring rack additization. ADDITIZATION HISTORY

Originally additives were blended into gasolines at the refineries, but with the trend toward exchange agreements, additives are now injected into the gasoline at terminals as trucks are being loaded. Additive "injection" at terminals has evolved as follows: a.

Hand loading typically from the top of tank truck compartments.

b.

Metering pumps.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 4 of 10 Rev. 3

Apr., 1999

ADDITIZATION HISTORY (continued) c.

Piston-type injectors.

d.

Electronic controlled injectors. SYSTEM COMPONENTS

SYSTEM A basic additive injection system consists of: a.

Receiving facility

b.

Storage tank

c.

Pump suction line from storage tank

d.

Additive supply pump(s)

e.

Return line from pump(s) to tank

f.

Additive supply line(s) from pump(s) to individual injectors

g.

Individual additive injectors

h.

Injection line(s) from individual injector(s) to product lines

i.

Control circuit to activate the particular additive system

j.

Product meter outputs to cycle injectors

See Figure 1 for a flow sheet of a typical additive system. RECEIVING FACILITY Mogas additive is typically delivered to a terminal by dedicated tank truck. A receiving station consists of a hose adapter, block valve, check valve, containment and piping to the tank. The tank truck is equipped with the hose and couplers required to connect to the receiving facility. A truck mounted pump is used for pump off to an unloading station (receiving facility). See EP 23-24-1 for a typical receiving facility layout. STORAGE TANK → Additive storage tanks at Exxon owned facilities should be installed inside the general tankfield diked area. Any proposed exceptions to this shall be reviewed and approved by the Technical Support Group. Tanks placed outside the main diked areas shall comply with the spacing requirements in DP 22-22-10. → Additive tanks shall be built per EP 9-9-2 and meet the requirements of EP 24-22-10. These tanks are typically a vertical type with 10,000 gallon capacity. This allows for a full tank truck delivery of 6,500 gallons with spare volume to allow for delivery schedules. → Storage tanks at exchange locations vary from 10,000 gallon dedicated vertical tanks to the smaller skid mounted tank units which have a minimum recommended capacity of 4,000 gallons. See EP 24-24-2. Dye injection may be in small quantities, and may only require drum storage and handling facilities.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 5 of 10 Rev. 3

Apr., 1999

SYSTEM COMPONENTS (continued) SUPPLY PUMP ASSEMBLY The supply pump is typically a positive displacement type pump. The pump is installed to inject additive into the flowing product line at the proper pressure and flow rate. The supply pump assemblies can be either single pump or dual pump assemblies, however Exxon uses only the dual unit. The dual pump (two pump) assembly is piped and manifolded together so either pump can be in operation while the other pump is in standby, or removed from service. The assembly is fitted with a dual motor controller and selector switch, so either pump can be operated, but only one power supply is required. The assembly is a freestanding pump rack with a structural base for mounting the pumps, and a control unit. The control unit is a combination thermal magnetic breaker/motor starter, mounted in an explosion proof enclosure fitted with a Hand/Off/Auto (H-O-A) switch, a padlockable power ON/OFF switch, pump selector switch and fused 480-120V control power transformer sized to handle 100W pump running light in addition to normal control devices. Typical assemblies also include the following items: a.

Suction strainer to protect pumps from debris

b.

Pressure relief bypass valve

c.

Inlet and outlet isolation valves

d.

Discharge pressure gage

e.

Discharge pressure switch to trip motor on low pressure

f.

Plugged tee fitting (1/2 in. NPT) on the pump suction for use in testing pump operation

g.

Steel piping with thermal relief valves

h.

Pump discharge check valves to prevent backflow

PIPING SYSTEM The basic piping system consists of three sections: a.

Pump suction from tankage

b.

Pump return to tankage

c.

Pump to injector header

All piping shall be welded carbon steel (Past experience has been excessive leakage from threaded-joint piping systems.). The pump suction shall be a minimum of two inches NPS. The pump to tankage return line is for discharge pressure relief. Under reduced or no-flow conditions, a positive displacement pump will over pressure the line which can overload the pump. The relief valve prevents this by allowing flow back to the tank. The relief valve shall normally be set to relieve at 40 psi above the product loading pump "dead head" pressure (pump operating at minimum flow and product tank at highest level). This is usually in the range of 125-140 psig.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 6 of 10 Rev. 3

Apr., 1999

SYSTEM COMPONENTS (continued) The pump skid is provided with a discharge pressure relief valve for additive recirculation to the tank. The purpose of this recirculation is to assure additive flow. Since injectors operate on an intermittent basis and only when there is gasoline product flow, there will be times when there is no additive flow to the loading rack. The return line shall be one inch NPS. The supply line to the injectors shall be a minimum of two inches NPS. INJECTORS One (1) injector is required for each meter loading spot. Injectors at many existing Exxon terminal and exchanges are piston type or electronic injectors. All new installations shall be electronic injectors per EP 24-24-1. All new installations shall have flow alarms and shutdowns. Injectors are grouped on racks with a single supply line. In older terminals and at some exchange terminals these racks are located near the loading rack. In newer or upgraded terminals injector racks are located on each lane with a main supply header connecting all. This reduces the tubing lengths between injectors and risers. This also aids in calibration and testing because the injectors are close to the meters so that injector response to meter pulse can be checked. Electronic additive injectors do not rely upon the cylinder/piston assembly to inject the required additive volume. Instead, these injectors open a solenoid valve, measure the flow of additive and then close the valve when the required additive volume has been injected. By measuring each injection attempt, the meter based injectors can track the injection performance on a "cycle by cycle" basis. If a particular injection attempt results in too little additive being injected, the device simply "corrects" the additization on the next attempt. In addition, electronic injectors typically "monitor" the injection process and can be programmed to produce an alarm if the additive treatment fails to meet a predetermined tolerance. Electronic injectors can be paced at any rate, but for the greatest accuracy, a 1 pulse per 1 gallon of fuel signal is preferred. However, experience has shown that Brooks presets/electronic injectors must be paced at 1 pulse per 40 gallons of fuel signal. Unlike the electronic injectors, a piston type injector injects every 40 gallons. Therefore, a properly operating electronic additive injector should additize within a closer tolerance than a piston type injector. INJECTION LOCATION Additive is injected upstream of the product meter, and as close to the meter as possible. In some existing facilities due to a lack of space on the piping, the injection point is into the side of the strainer. This practice should not be followed at new installations. Multiple additives may be required at a site and there will be a manifold at the riser with appropriate check and ball valves in each line.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 7 of 10 Rev. 3

Apr., 1999

INJECTION VOLUMES The additive volume added to gasoline varies depending on the additive component. The amount of Exxon additive injected currently varies from 0.75 to 1.2 gallons of additive per 1,000 gallons of gasoline. VISCOSITY IMPACT The viscosity of additive is generally in the higher range (630 SSU @ 32°F). Additives are diluted with solvents to lower their viscosity. This dilution also lowers the pour point temperature which improves cold temperature handling. To reduce freight and production costs it is desirable to handle higher viscosity additive rather than diluted. Increasing the viscosity has an impact on the injection system and existing systems may not be able to handle the increase. Increasing the viscosity will present the following problems: a.

Increased pressure drops through the piping, injectors and tubing.

b.

Possibility of pump cavitation due to item a.

c.

Decrease flow rate capacity through injectors.

d.

Possibility of line plugging in cold weather.

The above impacts on system pressure drop and decrease in flow can be offset in some circumstances by increasing the pump discharge pressure. However, if the pipe or tubing size used in a system is too small in diameter, practical increases in pressure will not result in the desired additive flow rates. In most cases it is better to increase the pipe and tubing diameter. Another area of concern is the additive meter(s). An oval gear meter measuring a fluid at 900 SSU and 3.3 GPM will have a ∆ p of 15 psi. To limit the pressure drop to 15 psi when the viscosity is increased to 2,200 SSU, the flow rate must be decreased by 60 percent to 1.3 GPM. The injector's type and size will impact the ability to handle higher viscosities. As the injected additive amount and viscosity has increased over the years, piston type injectors have been retrofitted with a larger size cylinder. Electronic injectors handle higher viscosity fluid better than the piston type injectors In typical systems, a significant portion of the pressure drop will occur in the piping/tubing from the storage tank to the injection point. This is especially true with additive systems that use 3/8 to 1/2 in. tubing. With current additive rates and viscosities, piping of 2 in. should be considered for the suction piping and discharge headers from pumps to the injectors. From the injectors 5/8 in. (minimum) tubing should be used. Also, at higher viscosities and temperatures approaching the pour point, small temperature changes can drastically change the viscosity. In cold climates heat tracing should be considered. When designing a new additive injection system, changing additive, or if a system is simply having problems, always evaluate the impact of viscosity. Additive selection is controlled by the Terminal Automation System (TAS) and by each meter for the particular product(s) being loaded. The TAS has the database to determine which additive is required for each customer.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

Page 8 of 10 Rev. 3

Apr., 1999

VISCOSITY IMPACT (continued) The meter or meter preset provides the signal to pace the injector. A signal is sent to the injector for each 1 or 40 gallons of gasoline delivered, however this volume can vary depending upon injector installed. A typical sequence of operation is as follows: a.

Driver inserts card into the TAS.

b.

TAS acknowledges card and permits loading of selected products.

c.

Appropriate additive pump starts.

d.

Injection system is pressurized.

e.

Additive recycles to the tank until gasoline starts flowing.

f.

Injector receives a control pulse from the meter (preset) as each 1 or 40 gallons of gasoline is delivered.

g.

Injector operates, injecting calibrated amount of additive.

h.

Item f & g repeat until loading is completed.

i.

Driver completes loading and "pulls" card.

j.

Pump stops.

Exxon Company, U.S.A.

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

FIGURE 1 ADDITIVE SYSTEM FLOW SHEET →

NOTES: 1. Thermal relief shall be provided as required on pump suction or discharge piping. 2. Flow meter not required with electronic additive injectors. Exxon Company, U.S.A.

Page 9 of 10 Rev. 3

Apr., 1999

DP 24-24-1 Exxon Company, U.S.A. Marketing Distribution DESIGN PRACTICES

ADDITIVE SYSTEMS PROPRIETARY INFORMATION - For Authorized Company Use Only

REVISION HISTORY Date 1/94 7/94 3/97 4/99

Revision 0 1 2 3

Description Issued as DP 24-24-1, with minor changes to Revision B, dated 12/93. Issued as DP 24-24-1, with minor changes to Revision 0, dated 1/94. Issued as DP 24-24-1, with minor changes to Revision 1, dated 7/94. Issued as DP 24-24-1, with minor changes to Revision 2, dated 3/97.

Exxon Company, U.S.A.

Page 10 of 10 Rev. 3

Apr., 1999