Construction, working of pneumatic (air) tractor’s brake system (II)

Construction, working of pneumatic (air) tractor’s brake system (II)

Working of air braking system 

When the brake pedal is pushed, the brake valve opens and compressed air is allowed into the brake chamber.

The brake valve consists of three passages.

  • Air intake
  • Exhaust
  • Brake chamber

When the brake pedal is pressed, the exhaust passage will be closed and the air intake passage opens and compressed air goes back to the chamber. During the return stroke, the exhaust passage opens while intake closes and used air goes to the atmosphere. This system is fitted with an emergency mechanical brake, which can be used when air supply fails the air brake system, which is called an air-assisted hydraulic braking system.

Working principle

In the air brakes, the compressed air (around 700 kPa) is used to actuate the brake mechanism. The system consists of an air filter, unloading valve, air compressor, air reservoir, brake valve, and 4 number brake chamber. The compressor takes atmospheric air through the air filter and compresses the air. This air is stored under pressure in the air reservoir. From this reservoir air goes to various accessories of the vehicle which operate on compressed air. Part of the air goes to the brake valve. The control of the brake valve is done by a driver who controls the intensity of braking according to an emergency.

Pedal Depressed

When the brake pedal is depressed, compressed air from the reservoir is transmitted through pipes equally in all directions to the brake chambers through the brake valve which further applies the brake.

Pedal released

When the driver releases the brake pedal, the master cylinder piston returns to its original position due to return spring, and the pressure is dropped. It releases brake shoes from brake drum to their original position and brakes are released.

Difference between air brakes and hydraulic brakes

Difference between air brakes and hydraulic brakes

Probable causes and remedies of the air brake system

Probable causes and remedies of the air brake system

Advantages of air braking system

  • It is more effective when compared to other brakes.
  • The air brake parts are easily located where the chassis design making is simple.
  • The compressed air can be used for tyre inflation wipers, horn, and other accessories.
  • It employs only air as the working medium which is easily available.
  • It is easy to store air at high pressure.
  • It provides a heavy braking effect used in heavy vehicles and trucks.
  • It provides better control.
  • It reduces the stopping distance.
  • It mainly allows less wear and tear of parts.
  • It has a flexible hose connection.

Disadvantage of air braking system

  • If there is any leakage in the passage, the entire system will fail. Therefore sealing of air is difficult.

Applications of air braking system

  • Trucks.
  • Buses.
  • Trailers
  • Semi trailers.

Trending issues on new flatbed trucks

Flatbed trailer main beam is the most important part, and its importance is self-evident. Everyone doesn’t want the main beam of their semi trailer broken. What are the reasons for the fracture of the semi truck beam?

Below is a summary of the reasons for the fracture of the trailer beam. You can look at it and try to avoid it when purchasing and using the semi truck.

Manufacturers defect

  • The flatbed trailer beam uses poor quality steel

The most direct and easiest reason to understand is that the steel quality of the beam used in the factory is not good enough to carry the designed load capacity, which causes the beam to break.

. Reduce the size of the beam

In order to save costs, the truck manufacturer reduced the size of the beam eg. If it was originally a 14mm thick slab, but reduced it to 10mm thick, and the customer did not know, it will also pull the load just like the 14mm thick load capacity. But it will crack in no time.

. Stitching beam web

In addition to reducing the size of the beams, the webs of some beams are connected by light and shorter steels.

. Welding is not good

In addition to the structure of the web, there is also the phenomenon of cracking of the lower wing plate. There are two main reasons for this. One is the technical problems of the welder, and the other is the unstable voltage during welding, which is not good.

. Deceived by unscrupulous salesman

In addition to the reasons mentioned above, there is another point that must be noted. Some salesmen, in order to grab orders, give low prices. They can only reduce the configuration of the semi trailer to achieve profit.

. Customers use and applications

In addition to the reasons for the truck manufacturer above, because of improper use by customers, many cases of flatbed trailer beam cracks and brakes.

. Overload

The biggest reason is long-term overload. This is easy to understand. The load capacity exceeds the designed value of the trailer. The beam cannot bear the weight of the cargo and causes fracture.

. Welding operation on the beam

It is strictly forbidden to weld on the semi truck beam. The trailer beam is supposed to be high strength steel.

  • In mountainous and uneven road, the beam is subjected to excessive distortion

Trucks that often run on rough roads and areas are prone to break beams. The torsion force of trucks that run in rough areas is much greater than that of flat roads. The specifications of the upper and lower wings and webs of the beams must be larger, otherwise the beams are likely to be broken.

How to prevent the beam of the flatbed truck from breaking

when buying a truck, choose a reputable salesman and a good reputable manufacturer. Don’t just look at the price. Then be sure to pay attention when using. Do not overload, weld the beam without permission, but also pay attention to the road conditions.

 GENERIC CODES

P1196: Electronic throttle system limp home – close stuck

Meaning

The electronic throttle system consists of ETS unit, ETS-motor, accelerator position sensor, throttle position sensor and limp home valve.

Among above-mentioned parts, limp home valve is attached under the throttle body and helps air to flow from the outside through this valve to the engine combustion chamber to prevent the vehicle from engine stall when the powertrain control module detects ETS system malfunction.

Possible causes

    Faulty electronic throttle system motor

    Faulty electronic throttle system

    Electronic throttle system unit

    Electronic throttle system harness is open or shorted

    Electronic throttle system circuit poor electrical connection

P1197: Exhaust gas temperature sensor 4 performance engine running

Meaning

The exhaust gas temperature sensors are variable resistors that measure the temperature of the exhaust gas. The exhaust temperature sensor 1 is the first exhaust temperature sensor on the exhaust system. The following exhaust temperature sensors are counted upward from the engine outlet to the exhaust system end. The engine control module supplies 5 V to the exhaust gas temperature signal circuit and supplies a ground to the low reference circuit. The exhaust gas temperature sensor temperature information is used by the ECM during the exhaust gas particulate filter cleaning process. The diagnostic trouble code will be set if the ECM detects that the difference between measured exhaust gas temperature and the estimated exhaust gas temperature is greater than a calibrated amount for greater than 1 s.

Possible causes

    Faulty exhaust gas temperature sensor

    Exhaust gas temperature sensor harness is open or shorted

    Exhaust gas temperature sensor circuit poor electrical connection

    Faulty engine control module

P1198: O2S heater circuit bank 1 sensor 2 electrical malfunction

Meaning

Oxygen sensors (O2S) or heated oxygen sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature, the faster the sensor will start sending an accurate signal to the engine control module.

In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.

The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.

Possible causes

    Faulty O2 sensor

    O2 sensor harness is open or shorted

    O2 sensor circuit poor electrical connection

P1199:  O2S heater circuit bank 2 sensor 2 electrical Malfunction

Meaning

Oxygen sensors (O2S) or heated oxygen sensors (HO2S) need to reach a minimum operating temperature of 750 degrees F to produce an accurate voltage signal. The faster the heated oxygen sensor reaches that temperature, the faster the sensor will start sending an accurate signal to the engine control module.

In order to achieve the require temperature, a heater element is included inside the heated oxygen sensor. The ECM controls the heated oxygen sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.

The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.

Possible causes

    Faulty O2 sensor

    O2 sensor harness is open or shorted

    O2 sensor circuit poor electrical connection

 P1200: Injector control circuit

Meaning

It indicates that an engine running the powertrain control module has detected an incorrect voltage level on one or more injector driver circuits for more than five seconds.

Possible causes

    Faulty fuel injector

    Fuel Injector harness is open or shorted

    Fuel Injector circuit poor electrical connection

   Copyright PUNCH.

All rights reserved. This material, and other digital content on this website, may not be reproduced, published, broadcast, rewritten or redistributed in whole or in part without prior express written permission from PUNCH.

Contact: [email protected]

Source link