Section 7.3

 7.3 Inspecting Doubles and Triples

Use the seven-step inspection procedure described in Section 2 to inspect your combination vehicle. There are more things to inspect on a combination vehicle than on a single vehicle. Many of these items are simply more of what you would find on a single vehicle. (For example, tires, wheels, lights, reflectors, etc.) However, there are also some new things to check. These are discussed in Section 7.3.1.

7.3.1 Additional Checks

Do these checks in addition to those already listed in Section 2, Step 5: Do Walk-around In­spection.

Coupling System Areas

• Check fifth wheel (lower).
  • Securely mounted to frame and / or body and / or rails.
  • No missing or damaged parts.
  • Enough grease.
  • No visible space between upper and lower fifth wheel. 
  • Locking jaws around the shank, not the head of kingpin.
  • Release arm properly seated and safety latch and / or lock engaged.
• Check fifth wheel (upper).
  • Glide plate securely mounted to trailer
• frame and / or body and / or rails.
  • Kingpin not damaged.
• Air and electric lines to trailer.
  • Electrical cord firmly plugged in and se­cured.
  • Air lines properly connected to glad hands, no airleaks, properly secured with enough slack for turns.
  • All lines free from damage.
• Sliding fifth wheel.
  • Slide not damaged or parts missing.
  • Properly greased.
  • All locking pins present and locked in place.
  • If air powered, no air leaks.
  • Check that fifth wheel is not so far forward that the tractor frame will hit landing gear, or cab will hit the trailer, during turns.

Landing Gear

• Fully raised, no missing parts, not bent or otherwise damaged.
• Crank handle in place and secured.
• If power operated, no air or hydraulic leaks.

Double and Triple Trailers

• Shut-off valves (at rear of trailers, in service and emergency lines).
  • Rear of front trailers: Open.
  • Rear of last trailer: Closed.
  • Converter dolly air tank drain valve: Closed.
• Be sure air lines are supported and glad hands are properly connected.
• If spare tire is carried on converter gear (dolly), make sure it's secured.
• Be sure pintle-eye of dolly is in place in pintle hook of trailer(s).
• Make sure pintle hook is latched.
• Safety chains should be secured to trailer(s).
• Be sure light cords are firmly in sockets on trailers.

7.3.2 Additional Things to Check During a Walk-around Inspection

Do these checks in addition to subsection 5.3, Inspecting Air Brake Systems.

7.4 Doubles and / or Triples Air Brake Check

Check the brakes on a double or triple trailer as you would any combination vehicle. Sub­-section 6.5.2 explains how to check air brakes on combination vehicles. You must also make the following checks on your double or triple trailers.

7.4.1 Additional Air Brake Checks

Check That Air Flows to All Trailers (Dou­ble and Triple Trailers).

Use the tractor parking brake and / or chock the wheels to hold the vehicle. Wait for air pressure to reach normal, then push in the red "trailer air supply" knob. This will supply air to the emergency (supply) lines. Use the trailer handbrake to provide air to the service line. Go to the rear of the rig. Open the emergency line shut-off valve at the rear of the last trailer. You should hear air escaping, showing the entire system is charged. Close the emergency line valve. Open the service line valve to check that service pressure goes through all the trailers (this test assumes that the trailer handbrake or the service brake pedal is on), and then close the valve. If you do NOT hear air escaping from both lines, check that the shut-off valves on the trailer(s) and dolly(ies) are in the open position. You MUST have air all the way to the back for all the brakes to work.

Test Tractor Protection Valve.

Charge the trailer air brake system. (That is, build up nor­mal air pressure and push the "air supply" knob in.) Shut the engine off. Step on and off the brake pedal several times to reduce the air pressure in the tanks. The trailer air supply control (also called the tractor protection valve control) should pop out (or go from "normal" to "emergency" position) when the air pressure falls into the pressure range specified by the manufacturer. (Usually within the range of 20 to 45 psi.)

If the tractor protection valve doesn't work properly, an air hose or trailer brake leak could drain all the air from the tractor. This would cause the emergency brakes to come on, with possible loss of control.

Test Trailer Emergency Brakes.

Charge the trailer air brake system and check that the trailer rolls freely. Then stop and pull out the trailer air supply control (also called tractor protection valve control or trailer emergency valve) or place it in the "emergency" position. Pull gently on the trailer with the tractor to check that the trailer emergency brakes are on.

Test Trailer Service Brakes.

Check for normal air pressure, release the parking brakes, move the vehicle forward slowly, and apply trailer brakes with the hand control (trolley valve), if so equipped. You should feel the brakes come on. This tells you the trailer brakes are connected and working. (The trailer brakes should be tested with the hand valve, but controlled in normal operation with the foot pedal, which applies air to the service brakes at all wheels.)

Test Your Knowledge - Section 7

• What is a converter dolly?
• Do converter dollies have spring brakes?
• What three methods can you use to secure a second trailer before coupling?
• How do you check to make sure trailer height is correct before coupling?
• What do you check when making a visual check of coupling?
• Why should you pull a dolly out from under a trailer before you disconnect it from the trailer in front?
• What should you check for when inspecting the converter dolly? The pintle hook?
• Should the shut-off valves on the rear of the last trailer be open or closed? On the first trailer in a set of doubles? On the middle trailer of a set of triples?
• How can you test that air flows to all trailers?
• How do you know if your converter dolly is equipped with antilock brakes?

 These questions may be on your test. If you can't answer them all, re-read Section 7.

Using a hand held device while driving is a serious traffic violation that could result in a driver disqualification.

To comply with Federal Motor Carrier Safety Administration (FMCSA) rules:

• No reaching
• No holding
• No dialing
• No texting
• No reading

For more information see www.fmcsa.dot.gov