5.3 Emergency Systems: Internal Valves, Remote Shut-offs & Crash Protection
Key Takeaways
- The AAMVA manual says to check that vapor recovery kits, grounding and bonding cables, emergency shut-off systems, and any built-in fire extinguisher work.
- Under 49 CFR 178.345-11, a cargo tank's self-closing system must be able to close all loading and unloading outlets within 30 seconds in an emergency.
- The remote closure must be more than 10 feet from the loading or unloading outlet where vehicle length allows, or at the far end of the tank.
- Where thermal closure is required, it must activate at no more than 250°F.
- 49 CFR 392.25 bans flame-producing warning devices, such as flares, for cargo tanks used for flammable liquids or flammable gases, whether loaded or empty.
Emergency systems are the parts of a tank vehicle you hope never to use and must know how to use without thinking. 49 CFR 383.119(g) lists proper use of emergency systems as required knowledge, and the AAMVA manual (8.1.2) makes checking them part of every inspection.
Special Purpose Equipment in the Manual
If your vehicle has any of the following equipment, make sure it works: vapor recovery kits, grounding and bonding cables, emergency shut-off systems, built-in fire extinguisher. Never drive a tank vehicle with open valves or manhole covers.
The manual also says to check the emergency equipment required for your vehicle, find out what you are required to carry, and make sure you have it and it works (Section 6.1).
Internal Self-Closing Stop Valves
For DOT-406, DOT-407, and DOT-412 cargo tanks, 49 CFR 178.345-11 requires each loading or unloading outlet to have an internal self-closing stop valve, or else an external stop valve as close as practicable to the tank wall.
- An internal valve sits inside the tank at the outlet, often at the bottom of each compartment. If piping outside the tank is damaged, the closed valve seat stays inside the shell and holds the product.
- Outlet piping that extends past the valve must have another stop valve or leak-tight closure at its end, such as a closed valve and a cap.
- In transit with hazardous materials, 49 CFR 177.834(j) requires all valves and closures in liquid discharge systems to be closed and free of leaks.
The Self-Closing System and Remote Closure
Under 49 CFR 178.345-11(b), each outlet must have a self-closing system that can:
| Requirement | Detail |
|---|---|
| Close in an emergency | All outlets within 30 seconds of actuation |
| Remote closure location | More than 10 feet from the loading or unloading outlet where vehicle length allows, or on the end of the cargo tank farthest from the outlet |
| Survive damage | If the actuating system is damaged or sheared off, the outlets must stay closed and hold product |
| Thermal closure | Where required for flammable, pyrophoric, oxidizing, or poisonous liquid materials, it must activate at no more than 250°F, located as close as practicable to the main loading or unloading connection |
| Manual backup | Outlets on those tanks must also be closable remotely by manual or mechanical means |
The remote control is placed away from the outlet so you can close the valves from a safer spot if a hose fails or a fire starts at the connection. Systems may be cable-operated, air-operated, or hydraulic, depending on the tank.
Proper use
- Know where every remote closure control is on the tank you are driving before you load or unload. Tanks differ.
- Know how it works (pull handle, push button, air valve) and what closed looks like.
- If a hose ruptures or product escapes during a transfer, use the emergency closure right away, then move away from the release.
- Don't reach through vapor or liquid to close a valve. Use the remote control.
- Report any control that sticks, is damaged, or fails to close the valves, and don't use the tank until it is repaired.
Sacrificial Shear Devices
Under 49 CFR 178.345-8, piping that extends beyond an accident damage protection device must have a stop valve and a sacrificial device, such as a shear section, outboard of the valve. When an internal self-closing valve is used instead of bottom damage protection, the sacrificial device must be within 4 inches of the tank shell or sump (never more than 8 inches).
The sacrificial device must break at no more than 70% of the load that would damage the valve or tank wall, and its failure must leave the valve intact and able to hold product. Never weld, sleeve, or brace over a shear section; making it stronger defeats its purpose.
Crash Protection Built Into the Tank
| Protection | Rule (49 CFR 178.345-8 unless noted) | Purpose |
|---|---|---|
| Bottom damage protection | Must withstand 155,000 lbs from front, side, or rear | Protects outlets and piping in the bottom third of the tank |
| Rollover damage protection | Must withstand loads equal to twice the weight of the loaded cargo tank motor vehicle | Protects manholes, valves, and fittings on the top two-thirds of the tank |
| Rollover protection drain | Required if the device could collect liquid on top of the tank | Directs liquid to a safe discharge point |
| Rear-end tank protection | Must deflect at least 6 inches without contacting the tank | Protects the tank and piping in a rear-end collision |
| Manhole covers (178.345-5) | Safety device keeps the cover from opening fully when there is internal pressure; fastenings must resist vibration and a rollover | Prevents a cover from blowing open |
| Pressure relief (178.345-10) | Must reclose leak-tight after a pressure surge, releasing no more than 1 gallon, in any vehicle orientation | Limits product loss in a rollover |
Gravity-actuated reclosing valves are not authorized as pressure relief valves on these cargo tanks.
Warning Devices After a Stop or Crash
49 CFR 392.25 prohibits flame-producing emergency signals, such as fusees or flares, for any cargo tank motor vehicle used for Class 3 (flammable liquid) or Division 2.1 (flammable gas) materials, whether loaded or empty. Use emergency reflective triangles, red electric lanterns, or red emergency reflectors instead. The emergency equipment rules require either three bidirectional reflective triangles or at least six fusees, so a flammable-service tanker must carry the triangles.
After a Crash
The manual's accident steps are to protect the area, notify authorities, and care for the injured:
- Protect the area. If possible, get the vehicle off the road. Turn on flashers and set out reflective triangles so other drivers can see them in time. If you stop to help at another crash, park away from it.
- Notify authorities. Call for help with the exact location. Report the product and any leak.
- Care for the injured. Don't move a severely injured person unless fire or traffic makes it necessary.
For a tank vehicle, add:
- Use the emergency closure if it is safe to reach and product is escaping from an outlet.
- Keep people back, upwind, and uphill from any leak (Section 6.3).
- Keep ignition sources away: no smoking and no flares.
- Have shipping papers available for responders if you are hauling hazardous materials.
Common Test Traps
- "Where is the remote shut-off required?" More than 10 feet from the outlet where vehicle length allows, or at the end of the tank farthest from the outlet.
- "What does a shear section do?" It breaks off so the valve stays intact and the tank holds product.
- "Flares or triangles for a gasoline tanker?" Triangles; flame-producing devices are prohibited, loaded or empty.
Under 49 CFR 178.345-11, where must the remote means of closing a DOT-406 cargo tank's outlets be located?
What is the purpose of a sacrificial shear section in cargo tank outlet piping?
A tanker that hauls gasoline breaks down on the shoulder while empty. Which warning devices may the driver use?