mc-306/dot-406 cargo chapter not for sale or distribution...

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Don

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MC-306/DOT-406 Cargo Tank Truck: Design, Construction, and Operating Procedures 2 2 2 2 2 2

CHAPTER CHAPTER CHAPTER ©

Bill

Han

d

Introduction

Cargo tank truck specifi cations are established and enforced by the U.S. Department of Transportation (DOT). Gasoline tank trucks had been constructed to the MC-306 cargo tank specifi cation since 1967. In early 1990, DOT revised its cargo tank regulations and devel-oped the DOT-406 cargo tank specifi cation to replace the MC-306, following a three-year transition period during which both MC-306 and DOT-406 cargo tanks could be constructed. After September 1995 all new atmospheric pressure cargo tanks constructed were required to be built to the DOT-406 specifi cation. Even though the old MC-306 specifi cation cargo tanks are being retired, it is not unusual to see these cargo tanks in service today. Some older MC-306’ s that have been retired from hazmat service can been seen on the highway converted to haul other liquids such as non-potable water, fertilizer, and other non-regulated materials.

From an emergency response perspective, the changes from the MC-306 to the DOT-406 specifi cation primarily deal with improved overturn, dome cover and relief vent performance in a rollover situation, and an increased minimum tank shell requirement. However, the basic shape, profi le, and operation of the gasoline tank truck remain the same.

Design and Construction Features

MC-306/DOT-406 units are commonly constructed of aluminum, although older MC-305 steel and stain-less steel tanks built prior to 1967 may occasionally be found. Shell thicknesses range from .151 to .187-inch (3.83 to 4.75 mm.) thick aluminum alloy, with the front and rear tank heads and the bottom tank shell normally being the thickest points. The maximum allowable work-ing pressure (MAWP) can be no lower than 2.65 pounds

per square inch gauge (psig) (18.3 kPa) and no higher than 4 psig (27.6 kPa). These tanks are not pressure ves-sels and are not designed for pressures above that exerted by the static head and vapor pressure of its contents.

Unlike containers constructed of steel, aluminum shell tank trucks will melt at temperatures as low as 1,200°F. (649°C.) when impinged by fi re at the vapor space above the level of the stored liquid. Boiling liquid, expanding vapor explosions (BLEVE) are not a common hazard. That being said, empty tanks (fi lled with gasoline vapor) can present hazards if they are subject to direct fl ame impingement. There have been cases where the tank shell has melted and there was an internal explo-sion in the compartment.

Although spectacular, upright gasoline tank truck fi res often become open tank or “pit” fi res after the top of the aluminum tank melts down to the liquid product level. In these situations, it is possible that the tank’s con-tents may either boil or be splashed out of the tank by improper fi refi ghting foam applications. If the unit has rolled over and is burning in the “wheels up” position, the rear compartment can fail rapidly due to the weight of the rear wheels as the aluminum container melts. Failure of the front compartment can also occur due to the weight of the unit’s mounted landing gear. During fi refi ghting operations, responders should keep as much distance as possible between themselves and the cargo tank. Foam operations should be conducted to keep emergency responders outside of the failure zone of a tank compartment.

As compared to low-pressurized containers, MC-306/DOT-406 tank trucks are typically elliptical shaped; see FIGUREFIGUREFIGURE 2- 1A 2- 1A 2- 1A and FIGUREFIGUREFIGURE 2- 1B 2- 1B 2- 1B . They are constructed of fl at aluminum sheets which are form-rolled, then welded along the seams. When tank ends and internal baffl es are attached to the container, or “barrel,” the tank becomes a structural unit. As a result, the tank’s structural integrity

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© Jones & Bartlett Learning, LLC. NOT FOR SALE OR DISTRIBUTION.

© Jones & Bartlett Learning, LLCNOT FOR SALE OR DISTRIBUTION




















doesn’t depend on the chassis or trailer for support. In an emergency, greater attention must be directed toward the barrel rather than the framing to which it is attached.

Tank capacities range from 2,000 (7,570 liters) to approximately 10,000 gallons (37,850 liters), although capacities as large as 16,000 gallons (49,205 liters) can be found in some states. These larger cargo tanks are sometimes referred to as “supertankers” within the indus-try. Tandem tank trucks or “pups” of up to 5,000- gallon (18,925 liters) capacity are also used extensively throughout the western United States; see FIGUREFIGUREFIGURE 2- 2 2- 2 2- 2

and FIGUREFIGUREFIGURE 2- 3 2- 3 2- 3 . Federal and state vehicle weight limits—rather than volume restrictions—are the primary criteria for determining vehicle loads and capacities.

LOW PRESSUREFigure 2-1A

NON-PRESSURIZEDFigure 2-1B

FIGUREFIGUREFIGURE 2-1A, 2-1B 2-1A, 2-1B 2-1A, 2-1B Cargo tank trucks under low pressure (e.g., MC-307/DOT-407, MC-312/DOT-412, MC-331, MC-338) will have a round shape, whereas non-pressurized cargo tank trucks (e.g., MC-306/DOT-406) will usually have an elliptical shape. Note: Some MC-306/406 vehicles may be found in service with round tanks. They may be transporting anything from liquor to solvents for industrial use.

© Bill Hand

FIGUREFIGUREFIGURE 2-2 2-2 2-2 Tractor-trailer MC-306/DOT-406.

© Michael Hildebrand

FIGUREFIGUREFIGURE 2-3 2-3 2-3 A tractor with double trailers commonly found in the Rocky Mountain states and Alaska.

© Tyler Bones

To transport several products simultaneously, tank trucks are divided into compartments—usually four or fi ve, but sometimes as many as eight. In general, the front and rear compartments are the largest. A minimum of 3 percent of each compartment must be left empty as a vapor space for product expansion.

Compartments are separated by disc-shaped bulk-heads. Compartment bulkheads provide structural support for the tank, but can be damaged in a rollover situation. Bulkhead failure will allow product to fl ow between com-partments, as well as change the tank’s weight distribution.

4 Gasoline Tank Truck Emergencies

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If an MC-306/DOT-406 tank truck is involved in a roll-over, responders should assume that the bulkheads have failed and view the cargo tank as a single compartment.

Although not required by federal regulations, many gasoline tank trucks have double bulkheads between compartments to prevent fuel contamination. On double bulkhead compartments, there will be small vents from both the top and bottom of the space between bulkheads. The bottom vents may or may not be threaded depend-ing on when the tank was made and the manufacturer. Carriers are permitted to plug the top vents if they choose to do so. These are visible on the outside (top and bot-tom) of the tank. If the bottom drain plug is not in place and product is leaking, it usually indicates a leaking com-partment bulkhead. However, one may still not be able to determine which compartment is leaking; see FIGUREFIGUREFIGURE 2- 4 2- 4 2- 4 .

Within each compartment are baffl es that minimize product surges during transportation; see FIGUREFIGUREFIGURE 2- 5 2- 5 2- 5

and FIGUREFIGUREFIGURE 2- 6 2- 6 2- 6 . Approximately .16 to .187-inches (4.06 to 4.75 mm.) thick, they are typically open in the cen-ter and at the 6 and 12 o’clock positions; see Figure 2- 5 and Figure 2- 6. To make it easier to completely off-load an overturned tank truck lying on its side, most tank

Valves

Baffles

Compartment

Compartment

Bulkhead

Bulkhead

BulkheadDome CoverAssembly

Each compartment has two baffles to keep the gasoline from surging forward when the truck uses the brakes.We only show one baffle in the right hand compartment so the reader can see the Internal Safety Valve.

InternalSafety Valve

FIGUREFIGUREFIGURE 2-4 2-4 2-4 Cutaway of a tank compartment. The bulkheads are the strongest points on the container shell.

© Jones & Bartlett Learning

FIGUREFIGUREFIGURE 2-5 2-5 2-5 These stenciled black dots indicate where baffl e openings are located at the 3 and 6 o’clock posi-tions. The right photo shows an interior tank view of the baffl e opening and 3-inch drain.

© Bill Hand

manufacturers will place additional baffl e openings at the 3 and 9 o’clock positions. Tank trucks so equipped are sometimes identifi ed by black dots or information stencils painted on each tank end at the 3 and 9 o’clock positions.

CHAPTER 2 MC-306/DOT-406 Cargo Tank Truck: Design, Construction, and Operating Procedures 5

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FIGUREFIGUREFIGURE 2-6 2-6 2-6 Cutaway diagram of a compartment baffl e.

© Jones & Bartlett Learning

Vapor

3-Inch Drain3-Inch Drain

Liquid Drain Hole

Bulkhead Bulkhead Bulkhead

There are several indicators of both the number of compartments and the capacity of each:

� Manufacturer’s Specifi cation Plate. Under Federal law, each tank constructed to DOT specifi cations must have a certifi cation plate mounted on the cargo tank. On truck and trailer units, the cer-tifi cation plate will be mounted on the left front of the tank along with the trailer plate, although units built before 1985 will have it on the right front of the tank. On some older trailers, the plate might also be mounted on the right side of the fi fth wheel or slide plate.

The specifi cation plate provides the DOT con-tainer specifi cation number (MC-306/DOT-406), date of manufacture and test, shell material, number of compartments and their capacity, and maximum product load; see FIGUREFIGUREFIGURE 2- 7 2- 7 2- 7 . Always check the certifi cation plate prior to initiating transfer opera-tions to verify container design and construction

information. Codes for shell materials include the following:

AL Aluminum CS Carbon Steel HSLA High Strength Low Alloy Steel HSLA-QT High Strength Low Alloy, Quench

Tempered Steel MS Mild Steel SS Stainless Steel

Some cargo tanks are designed to multiple container specifi cations, which allow them to transport more than one commodity. A common multipurpose confi guration is the combination DOT-406/DOT-407 unit. In addition to the man-ufacturer’s specifi cation plate, these cargo tanks have a second “multi-purpose” plate which iden-tifi es the specifi cation under which the cargo tank is being operated. These plates are color-coded, as


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are the fi ttings that are added to make the cargo tank meet the respective specifi cations. A sliding shield or fl ip over plate exposes the specifi ca-tion plate currently in use. However, these plates may move as a result of an accident or may not be properly positioned by the vehicle driver. The common color codes are:

MC-306/DOT-406 Red Plate and Fittings MC-307/DOT-407 Green Plate and Fittings

� Number of Dome Covers. There will generally be one dome cover for each compartment; DOT requires that each compartment with a capacity greater than 400 gallons must have its own dome cover. However, there are “foolers”—large front and rear compartments may sometimes have two dome cov-ers. Untrained individuals may also confuse a clean-out cap as a dome cover. If in doubt, compare the number of dome covers with the number of internal safety valves on the bottom of the cargo tank. Each individual compartment has its own unloading valve.

� Number of Discharge Outlets or Control Valves. Each compartment will have its own control valve.

FIGUREFIGUREFIGURE 2-7 2-7 2-7 Specifi cation plate.

© Bill Hand

A compartment will either be piped to its own dis-charge outlet or be tied into a manifold. Individual piping and discharge outlets are more common on gasoline tank trucks, while manifolds are more com-mon on tank trucks transporting fuel oil and aviation fuels. Some of those tanks are single compartment.

� Capacity Markings Painted along the Overturn Rail. When provided, these will often consist of one to three numbers per compartment painted on the side of the overturn rail. If the dome cover on a compart-ment is opened, a vertical rod intersected by three discs or plates (sometimes known as “butterfl ies”) will be visible. These discs or plates mark three levels of fullness—generally 100, 75, and 50 percent—and are directly related to the capacity markings painted on the side of the overturn rail (i.e., the top disc cor-responds to the highest number and so forth).

These markings may be helpful in a rollover situation in quickly ascertaining the capacity of a compartment. The dome covers are rarely opened during normal operations other than maintenance. It is not a common industry practice to climb on top of cargo tanks unless a loading rack is equipped


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with an OSHA-compliant fall protection system. Most companies prohibit drivers from the top of gasoline tank trucks and in some cases have removed the access ladders from the tank.

FIGUREFIGUREFIGURE 2-8 2-8 2-8 Cable-actuated safety valve.

© Bill Hand

FIGUREFIGUREFIGURE 2-9A 2-9A 2-9A Air-actuated internal safety valve.

© Bill Hand

FIGUREFIGUREFIGURE 2-9B 2-9B 2-9B The operation of air-actuated internal valves is a two-step process involving (1) the open-ing of the master air control valve (right side of com-partment) and (2) the respective compartment valve (individual compartment air switches in white box).

© Bill Hand

1

2

Master Control Valve

Internal safety valves are normally 4-inch (101.6 mm.) “plug” valves, but can be as large as 6-inch (152.4 mm.) valves. They are spring-loaded and normally closed, and require either air pres-sure or cable (mechanical) activation to remain open; see FIGUREFIGUREFIGURE 2- 8 2- 8 2- 8 . The operation of air-actuated internal valves is a two-step process which involves opening the master air control valve and the com-partment valve; see FIGUREFIGUREFIGURE 2- 9A 2- 9A 2- 9A and FIGUREFIGUREFIGURE 2- 9B 2- 9B 2- 9B . However, it is important to recognize that some air-actuated valves can be opened manually.

Always refer to the tank’s specifi cation plate if it is visible to deter the number of compartments and capacity.

CAUTION

Safety Features

Gasoline cargo tank trucks have a number of safeguards.

1. Internal Safety Valves. An internal safety valve is required for each compartment. The plug-type valve sits inside the compartment to protect it from mechanical stress and accident damage. Within 4 inches (101.6 mm.) of the tank shell is a “shear cut” section of piping designed to break under mechanical stress, such as when an auto goes under a cargo tank. This shear cut reduces the thickness of the piping by approximately 20 percent. If a col-lision causes stress at that point, the piping should fail at the shear point while the internal valve remains intact within the compartment, thereby minimizing product loss. However, it is important to remember that many bottom-loaded units will have “wet” piping (product in their piping) prior to making deliveries. Even if the internal safety valve remains intact, any mechanical damage to the dis-charge piping can result in 20 to 40 gallons (75.7 to 151.4 liters) of product being spilled.


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FIGUREFIGUREFIGURE 2-10 2-10 2-10 The emergency shutoff must be located 10 feet away from the point of product discharge and can be found on either the driver’s side or passenger side of the front of the cargo tank. On the MC-306 and DOT-406 they are almost always on the driver’s side. Photo shows a cable-actuated emergency valve.

© Bill Hand

On vehicles with cable-actuated internal valves, a secondary safeguard for ensuring that the internal valves are closed is to close the com-partment door on the side of the tank where all internal valve controls are located. When the door is pushed closed, all internal safety control valve handles will be forced to the vertical, or closed, position. However, be aware of older, modifi ed tank trucks which may not have a compartment for the internal valve controls, or poorly main-tained vehicles where the compartment doors will not physically move the internal control valves to the closed position.

The performance of safety valves and all other cargo tank safety features is directly related to pre-ventive maintenance. There have been instances in which the internal safety valves have been found tied open or improperly seated.

2. Fusible Links, Nuts, and Plugs. Fusible links and nuts are found on cable-actuated systems, whereas fusible plugs and plastic air lines are used on air-actuated systems. In the event of a spill fi re under or around the vehicle, the fusible device will melt, releasing cable tension or air pressure. Both fusible links and nuts are required to actuate at temperatures not greater than 250°F. (121°C).

3. Emergency Shutoff. These valve controls, when actuated, automatically close all internal safety valves. They are designed for use during product transfer operations should a spill or fi re block or prevent personnel from reaching the discharge outlets and controls. Depending upon their method of actuation (air or cable), the control mechanism may be a knob, air switch, break tube,

or valve. The emergency valve control will be found on the left front of the tank, directly behind the cab; see FIGUREFIGUREFIGURE 2- 10 2- 10 2- 10 . On some tanks, a second remote valve may be found at the right rear of the trailer or near the discharge outlets. Although the emergency valve control must be marked, the type of marking can vary.

4. Vacuum and Relief Valve Protection. Both nor-mal and emergency pressure relief protection is required on all tank vehicles. Common pressure relief devices include relief valves, fusible plugs, and pressure vents. These devices will usually be part of the integrated dome cover assembly; see FIGUREFIGUREFIGURE 2- 11A 2- 11A 2- 11A . They are designed to open into the vapor space of the container, and must be mounted to prevent any accumulation of water or ice from impairing their operation. DOT pressure relief requirements include: • The primary pressure relief device must be set

at no less than 125 percent of the MAWP or 3.3 psig, whichever is greater, and not more than 138 percent of the MAWP.

• Each vacuum relief device must be set to open at no more than 6-ounces vacuum.

Each individual compartment is provided with emergency venting, which is required to function in any vehicle position, including a roll-over. However, in a rollover situation involving a fi re, pressure relief devices might not relieve the internal pressure as rapidly if they are blocked or covered by product. In other instances, the prod-uct surge created by the rollover may cause the relief device to actuate and allow liquid product to escape from the tank. Current DOT regulations


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require that relief valves be designed to allow for no more than one liter of product release in the event of a rollover or a dynamic pressure surge. If there is fi re impinging on either an upright or rolled tank, pressure will build in the tank and product can be forced out of either the relief device or in some cases the dome cover. This is an important consideration during incidents were the cargo tank is being impinged by fi re from an external source, such as a burning vehicle or the truck tractor.

5. Vapor Emission Controls . Vapor recovery is important for both environmental and product conservation measures. Vapor recovery, as the term implies, is the recovery of hydrocarbon vapors when a tank truck is being fi lled or unloaded. It provides a closed circuit for the control of both liq-uid and vapor during product transfer. The vapor recovery header may be built into the overturn rail or run internally through the tank; see FIGUREFIGUREFIGURE 2- 11B 2- 11B 2- 11B . A number of older MC-306 tank trucks may have a separate external vapor recovery system. Vapor recovery piping and connections will often be marked by an orange color code; see Figure 3-4, page 25—The API Color Code Chart.

When a tank truck is off-loaded, vapors will be highly concentrated in each compartment. This vapor concentration, if contained, will almost always be too rich to burn. If the “empty”

tank is subjected to intense fi re conditions, the aluminum shell will fail quite rapidly and in rare cases, it will fail violently.

6. Overturn Protection. Overturn rails or guards must be provided on tank trucks to protect all fi ll open-ings, manholes, inspection devices, and relief devices from damage during a rollover. These devices must withstand a vertical load twice the weight of a loaded tank and a horizontal load in any direction equiva-lent to one half the weight of a loaded tank. If the product can accumulate in the overturn protection area during normal operations, a drainage system must be provided to handle the runoff.

Although the overturn barriers will normally protect the dome covers from direct mechanical stress, older style dome covers and those not prop-erly maintained will usually leak when involved in a rollover because of excessive liquid head pres-sures, product surge after the initial impact, or faulty gaskets.

Loading and Off-Loading Procedures

Most MC-306/DOT-406 tank trucks in gasoline ser-vice and operating in major U.S. metropolitan areas are designed with a vapor recovery system. In contrast, fuel oil tank trucks are not required to have a vapor recovery system because of fuel oil’s lower vapor pressure.

1

23

FIGUREFIGUREFIGURE 2-11A 2-11A 2-11A Integrated dome cover showing clockwise (1) tank overfi ll sensor, (2) vapor recovery vent and hose connected to the vapor recovery header/rollover protection, and (3) observation port/opening.

© Mike Hildebrand


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The following general procedures are used through-out the petroleum industry for the loading and off- loading of gasoline tank trucks.

� Loading Procedures. When a gasoline tank truck is being loaded, liquid product is moved from storage tanks to the loading rack and fi nally into the tank truck. Tank trucks may either be top loaded or bottom loaded. Although bottom load-ing is most prevalent, top loading for the transfer of combustible liquids and low vapor pressure products (e.g., fuel oil) may be found in some areas. A fi ll stem tube is inserted into each com-partment and product is then transferred.

The most common method of loading gaso-line into tank trucks is through bottom loading. Each tank compartment has a vent connected to the vapor recovery piping system. These vents are connected either mechanically or pneumatically to each compartment’s internal safety valve. When the internal valve is opened, the vent will also open automatically. This provides both vacuum and pres-sure protection during product transfer operations, without the vehicle operator having to physically open the dome cover; see FIGUREFIGUREFIGURE 2- 12 2- 12 2- 12 . As product is transferred, the vapors are collected into the vapor collection header on the tank truck and then piped to either a vapor condensing unit or a burner.

Although there are top-loading vapor recov-ery systems in operation, vapor recovery is gener-ally synonymous with loading through the bottom of the tank truck. It’s important to remember that bottom-loaded tank trucks typically have product in their piping prior to making their deliveries. Any mechanical damage to the discharge piping can result in 20 to 40 gallons (75.7 to 151.4 liters) of product being spilled.

There are several safeguards that are installed on both petroleum product loading racks and tank trucks in order to prevent overfi lls:

• Product transfer can’t occur until an electrical sensor connection is made between the load-ing rack pump controls and the tank truck. Although there are several manufactures of these overfi ll protection systems, most people in the cargo tank industry refer to these as a “Scully System.”

• “Dead man” switches control product fl ow. If the dead man switch is released, the fl ow of product will be stopped.

• Most newer tank trucks have a bar or switch interlock connected to the vehicle braking sys-tem. When the interlock is engaged, the brakes will be engaged and the vehicle cannot be moved; see FIGUREFIGUREFIGURE 2- 13 2- 13 2- 13 .

FIGUREFIGUREFIGURE 2-11B 2-11B 2-11B This cutaway view reveals the internal vapor recovery system.

Courtesy of Safe Transportation Training Specialists


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FIGUREFIGUREFIGURE 2-12 2-12 2-12 Internal safety valve with mechanical rod connection to vapor recovery system vent.

Courtesy of Safe Transportation Training Specialists

FIGUREFIGUREFIGURE 2-13 2-13 2-13 Bar interlock which activates the vehicle brakes when raised. Also note the vapor recovery connection on the left.

© Bill Hand

Brake Interlock Bar“Dixie Gate”

“Safety Gate”

Vapor RecoveryConnection


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• Preset loading meters and control valves pro-vide a method to load a specifi c and predeter-mined quantity of product.

• Product level sensors are installed in each com-partment. When actuated, they will signal a high-level condition and shut off product fl ow. Several types of sensing devices exist, includ-ing fl oats, optical sensors, and thermistors.

� Off-Loading Procedures. When a tank truck off-loads its product, the product transfer process is reversed. Liquid product now fl ows by grav-ity through a 4-inch hose from the tank truck into storage tanks, while vapors are returned to the tank truck through a 3-inch vapor line; see FIGUREFIGUREFIGURE 2- 14 2- 14 2- 14 . Vapor recovery piping and connections will often be

Vapor

Vapor

Liquid

Liquid

FIGUREFIGUREFIGURE 2-14 2-14 2-14 “Closed” off-loading system from a gasoline tank truck to an underground storage tank.

© Mike Hildebrand

marked by an orange color code. After delivery, the tank truck returns to the terminal, where the petro-leum vapors are safely disposed. Options include fl ares which burn off the vapors, and condensers which liquefy the vapors for recovery.

When a tank truck is off-loaded, vapors are highly concentrated in each compartment. Vapors from an “empty,” off-loaded gasoline tank truck with a capacity of approximately 9,200 gallons (34,822 liters) can be condensed into approximately 8 gallons (30.3 liters) of product. This vapor concentration, if contained, will be too rich to burn. If the off-loaded, “empty” tank is subjected to intense fi re conditions, the shell will rapidly fail, or in rare cases explode.


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Scan A—Construction Details

Typical Design MC-406 Cargo Tank

Round cross-section with stiffi ng rings.

Non-Typical Design MC-406 Cargo Tank

Elliptical shape (passenger side view).

14

© Photos.com

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M967

M967

M969

The M967 Bulk Fuel Transport and the M969 Refueler are the military version of the DOT-406 Cargo Tank and are con-structed of steel.

Non-Typical Design MC-406 Cargo Tank

15

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Important Specifi cation Plate Information for Emergency Responders

1. DOT Specifi cation Number 406 AL (Aluminum shell)

2. Maximum Allowable Working Pressure (3.3 psig)

3. Test Pressure (5 psig)

4. Original Test Date (May 2012)

5. Total Nominal Capacity (9,500 gallons)

6. Maximum Loading Density (8.6 lbs/US gallon)

7. Compartment Nominal Capacity Front to Rear Gallons (3,300; 2,350; 1,250; 2,600)

8. Shell Material Alloy (5454-H32 Aluminum)

9. Head Material Alloy (5454-0 Aluminum)

10. Weld Material Alloy (5356 Aluminum)

11. Manufactured Shell Thickness Top Ends (.182) Top Center (.194) Side (.182) Bottom (.204)

12. Minimum Shell Thickness Top Ends (.173) Top Center (.183) Side (.173) Bottom (.189)

13. Manufactured Head Thickness (.204)

14. Minimum Head Thickness (.173)

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Cable from Valve toControl Box & Lever

Shear Section

MechanicalInternal Valve

Push Rod

When the Bottom Internal ValveIs Opened, the Push Rod Opensthe Vapor Push Vent

Fusible Link

Loading/Discharge Pipe

Vapor Push VentFusible LinkDetail

Mechanically Operated Internal Valve

17

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Pneumatically Operated Internal Valve (Exterior View) Shown from the Underside of the Tank

Shear Section

Note the shear section, which is scored and designed to break away on impact, allowing the internal valve to close in the safe position.

Pneumatically Operated Internal Valve Interior View (Valve Open)

18

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Latch Style Dome Lid

Cylinder ContainingSpring That Regulates

5-lb PRD

VaporRecoveryPush Vent

Coupler to VaporRecovery Rail

VaporRecovery Rail

Dome Latch

Low Voltage Lineto Optical/ThermalLoad Monitor

3-lb PRD &Vacuum BreakerCover

3-lb PRD &Dome Lid

Vapor RecoveryPush Vent

Dome LidBonnet Ring

3-lb PRD & Vacuum BreakerAttached toInterior

Optical/ThermalLoad MonitoringSensor

Pneumatic Line

19

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Coupler to VaporRecovery Rail

Vapor Recovery Rail

Strong Back

Low VoltageLine to Optical /Thermal LoadMonitor

3-lb PRD &VacuumBreakerConcealedunder StrongBack

Vapor RecoveryPush Vent

Dome Lid Bonnet Ring

Pneumatic Line

Strong Back Style Dome Lid

Strong Back Style Dome Lid (open view)

Vapor Recovery Rail

Strong Back

Coupler toVaporRecovery Rail

Vapor Recovery Push Vent

CylinderContainingSpring ThatRegulates 5-lb PRD

Low VoltageLine to Optical/Thermal LoadSensor/Monitor

3-lb PRD & VacuumBreaker Concealedunder Strong Back

Pneumatic Line

20

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Safety Gate Lifts Up to Allow Access to Discharge Lines

VaporRecovery

Connection

VaporRecovery

ConnectionProduct Discharge Valves

DOT-406 Cargo Tank Vapor Recovery System

LIFTING THIS GATE MAY OPEN VAPOR RECOVERY VALVES AND/OR SET TRAILER BRAKES!

WARNING

21

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Spring LoadedAPI Valves

Air Inter-LockPaddle Sets TrailerBrakes WhenDepressed

Flow Reducersand Caps

Air Inter-Lock

Scan Sheet content and photos courtesy of Safe Transportation Training Specialists

www.safetransportation.com

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mc-306/dot-406 cargo chapter not for sale or distribution...

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