EMPTY/LOAD DEVICE TRAINING MODEL SERIES 6200, 6600, & ENX.

transcript

EMPTY/LOAD DEVICE TRAINING

MODEL SERIES

6200, 6600, & ENX

Part I. How it StartedOne of the issues that freight car designers face today is to achieve

the maximum braking effectiveness on a car whether it is empty or loaded. Today’s cars are being constructed much lighter than in years past, yet they carry heavier loads. If these cars were to utilize the same braking forces from years ago, it would result in brake related wheel defects like, shelling, flat spots and so on.

The greater the weight of a moving object, the greater the force required to slow it down and bring it to a complete stop. An empty freight car requires less braking force to slow it down or stop it compared to a loaded car.

To solve this issue, the Empty/Load device was created to limit braking forces while the car is empty and maximize the braking force in loaded condition.

How it helps:Single capacity air brake equipment cannot recognize

whether the car is empty or loaded. As a result, the brakes apply in proportion to the brake pipe pressure reduction, regardless of the weight of the car. With a heavy service brake application, a light car may be over-braked when it is in empty, which may result in the following:

• Flat spots on wheels due to sliding• Shelling of the wheels• Premature removal of brake shoes• Increased damage to rail

To order to prevent these over-braking issues, the empty/load device was developed.

How it works:Part A: Principles of Empty/Load Braking

Most empty/load brake equipment is not designed for a variable car load, which means that it does not proportion the braking force to the load of the car. The device only detects if the car is empty or loaded, not partially loaded. Typically, if the car is loaded to 20% or more of its capacity, the car is considered to be loaded and is braked as if it were loaded.

We must first understand that the retarding force on the car is directly dependent upon the pressure developed in the brake cylinder. So, we must reduce the brake cylinder pressure to reduce the braking force. Therefore, it is necessary to determine if the car is empty or loaded and then adjust the brake cylinder pressure accordingly.

How the load is detectedAt this point there are 2 methods of detecting the load of a car. They are the

Arm-type detecting devices and the Slope sheet canister detecting device.

1. Principles of the Arm-Type Sensing Devices. When a car is empty, the truck springs have only the weight of the car on them and are in a relaxed state. As the car is loaded, the springs

will compress. So, by measuring the amount of spring deflection we can determine whether the car is empty or loaded. A common method of measuring the spring deflection is by using a moveable sensor arm or piston that is part of a valve mounted on the

car. As air is applied, the sensor arm or piston will rotate or extend to touch the side frame or a bracket located on the side frame. The empty/load device detects the change in distance between the initial setup position and the side frame and deflects the air pressure accordingly.

MODEL 6600 EMPTY/LOAD VALVES

6600-1

6600-2 6600-1U

Versions of the Arm-Type Empty/Load

6600 Series

ELRP SC-1

ENX EL-# ELX-U

The Arm Type System

This system is typically comprised of 3 parts depending on the application. These parts are:

ReservoirSensing Valve (S1)

Proportional

Valve (P1)

Located in specific places in the braking system, all have a unique job in the braking process.

The Sensing Valve is located over the bolster side frame and senses whether the car is empty or loaded. Air is either blocked and returned to the brake cylinder or passed through to the proportional valve and reservoir.

cont…

The Proportional Valve located between the Control Valve and the Brake Cylinder, deflects the air away from the brake cylinder into the reservoir, therefore reducing the brake cylinder pressure and braking force.

The Reservoir is an empty canister that is a holding tank for the deflected air.

Cont…

6600 SERIES VARIATIONS • 6600-1: This valve is a standard 60% valve, which will reduce the car’s

brake cylinder pressure to approximately 60% of the loaded car pressure when the car is in empty condition.

Mounted to the car structure, the valve’s 3 piece construction is used on the standard freight cars or end trucks of 5-unit articulated cars.

• 6600-2: This valve is a standard 60% valve like the 6600-1 with 3 piece construction for use in areas where the 6600-1 cannot fit.

• 6600-1U: This valve is a standard 60% like the 6600-1, but it is condensed into one piece or unitized piece. It is used on the intermediate trucks of the 125 ton articulated 5-unit double stack cars.

NOTE: These valves have all have a 50% version where the valve will reduce the brake cylinder pressure by 50% for empty car condition.

2. PROPORTIONAL VALVE

Proportional ValvePipe Bracket

Indicator

The Proportional Valve is mounted in the brake pipe between the Air Brake Valve and the Brake Cylinder, so the air pressure must go through the Proportional Valve before it gets to the Brake Cylinder.

The Proportional Valve’s primary function is to provide a balance of brake cylinder pressure and equalizing reservoir for an empty brake application.

When a empty car load is detected, a percentage of the air pressure is deflected away from the brake cylinder to the reservoir. Depending on the weight of the car, a 50% valve will send 50% of air pressure to the brake cylinder and a 60% will send 60% of the air pressure to the brake cylinder.

The 50% is NOT interchangeable with the 60% proportional valve.

3. Equalizing Reservoir

The Reservoir accepts the deflected air pressure from the proportional valve during an empty application.

It is located between the Sensor Valve and the Proportional Valve.

The primary function is to provide air pressure balance with the brake cylinder.

Understanding the Air Flow

Downstream Valves

6600 Series

Downstream (6600)

Charged

RelativePressure

Low Brake Pipe

ControlValve

ReservoirAux Emergency

ProportioningValve

SensorValve

Brake Cylinder

Reservoir

Downstream (6600)

Minimum Application

RelativePressure

Low Brake Pipe

ControlValve

ProportioningValve

SensorValve

Brake Cylinder

Reservoir

LOADED CAR

Downstream (6600)

Full Service – Car Loaded

RelativePressure

Low Brake Pipe

ControlValve

ProportioningValve

SensorValve

Brake Cylinder

Reservoir

Downstream (6600)

Valve Detail – Car Loaded

Sensor motion limited by car side frame, detecting loaded car.

Air passes directly through the sensor to the cylinder.

Downstream (6600)

Emergency – Car Loaded

RelativePressure

LowBrake Pipe

ControlValve

ProportioningValve

SensorValve

Brake Cylinder

Reservoir

EMPTY CAR

Downstream (6600)

Full Service – Car Empty

RelativePressure

Low Brake Pipe

ControlValve

ProportioningValve

SensorValve

Brake Cylinder

Reservoir

In Empty condition, the arm fully extends, allowing proportional air to be

diverted to the reservoir.

Downstream (6600)

Valve Detail – Car Empty

Sensor motion not limited

Indicatorextends

Proportional spool divides pressure

To Reservoir

Pressure equalizes.

RelativePressure

Downstream (6600)

Emergency – Car Empty

RelativePressure

Low Brake Pipe

ControlValve

ProportioningValve

SensorValve

Brake Cylinder

Reservoir

In Empty condition, the arm fully extends, allowing proportional air to be

diverted to the reservoir. This occurs during Emergency application as well, but the pressures

are a little higher.

Downstream (6600)

Valve Detail – Exhaust

Exhaust valve opens

Check valve opens

RelativePressure

Exhaust

To Reservoir

MODEL ENX EMPTY/LOAD VALVES

Upstream (ENX)

Charged

RelativePressure

Reservoir

TMB Cylinder

Brake Pipe

#3 Pipe

Upstream (ENX)

Minimum Application

RelativePressure

Side Frame

To Cylinder From Control Valve

There is not enough airin the system to force

the arm to drop.

LOADED CAR

Upstream (ENX)

Full Service - Loaded

RelativePressure

Reservoir

TMB Cylinder

Brake Pipe

Side Frame

Control Valve

RelativePressure

Upstream (ENX)

Full Service - Loaded

Port to Reservoir closed

Side Frame

The arm is limited by the side frame..

RelativePressure

Upstream (ENX)

Emergency - Loaded

Reservoir

TMB Cylinder

Brake Pipe

Side Frame

Upstream (ENX)

Emergency - Loaded

RelativePressure

Side Frame

EMPTY CAR

Upstream (ENX)

Full Service - Empty

RelativePressure

Reservoir

TMB Cylinder

Brake Pipe

ControlValve

Side Frame

Upstream (ENX)

Full Service - Empty

RelativePressure

LowSide Frame

To Reservoir

Port to Reservoir opens

Indicator extends whenarm drops and pressurereaches 15psi.

Upstream (ENX)

Emergency - Empty

RelativePressure

Reservoir

TMB Cylinder

Brake PipeSide Frame

Arm fully extended

RelativePressure

Upstream (ENX)

Emergency - Empty

From Control Valve

Side Frame

Arm not limited by Side Frame in empty position.

To Cylinder To Reservoir

Arm drops when air is applied. Load is not detected, So port to reservoir opens and air is displaced.

MODEL 6200 EMPTY/LOAD VALVES

• 6200-5B• 6200-50/50• 6200-5/30• 6200X-40B

3. Versions of the Slope Sheet Mounted Empty/Load

6200 Series

6200 SERIES VARIATIONSThere are basically three (3) members of the 6200 Series valve family.

Each is designed to conform to specific car construction or customer requirements. Each delivers a percentage of the loaded car pressure when the car is in empty condition, thus reducing the effective braking force. They are as follows:

A) 6200X-40BF: This is a standard 40% valve which delivers 40% of the loaded pressure to the Brake Cylinder during empty car condition. This lower braking force is necessary due to the trend toward building lighter aluminum cars while designing it for the current 286,000 lb Gross Rail Load.

B) 6200-5: This is a standard 60% valve which delivers 60% of the loaded pressure to the Brake Cylinder during empty car condition. This valve is designed for cars with heavier light weight conditions.

6200 SERIES VARIATIONSC) 6200-50/50: This is a 50% valve with a standard change over point of

17psi. It is designed for intermediate light weight cars.

Note: Although the 6200-5, 6200X-40 and the 6200-50/50 are all applied and tested the same, the valve operating portions (replacement portions) are not interchangeable. If a valve operating portion needs to be replaced, it can be identified by its model number, which is machined into the front surface of the valve body.

• GENERAL– The following tests and inspections are to be performed in conjunction

with the latest revision of the AAR Code of Air Brake System Tests for Freight Equipment, Standard S-486, latest revision, special tests section, auxiliary devices sub-section.

• INSPECTION• Before proceeding with testing of empty load equipment, the

following inspection should be performed:– Inspect for any general damage to empty load valve, including dents or

punctures. (Replace if obvious defect exists.)– Check for secure attachment of empty load valve to slope or floor sheet

of car. (Make any necessary repairs.)– Inspect pipe or hose connections for secure attachment. Make sure

hoses or pipes are free from cuts, cracks, or other damage or defects. (Replace if necessary.)

– Check hose or pipe connections for proper installation. Empty load valve will not function properly if piped incorrectly. (Make adjustments if necessary.) (See Figure 1.)

• TESTING– LOADED CAR MODE

• Locate and remove uppermost machine screw and lock washer. (See Figure 2.)

• Insert test handle (see Figure 3) into vacant hole. This will place empty load valve into loaded mode.

• Make 20 psi reduction using single car test device. With brakes applied, check to see that indicator stem is not extended, indicating that empty load valve is in loaded mode. (See Figure 4.)

• Release brakes by placing single car test device handle into Position No. 1. Brake cylinder piston should retract and air should exhaust from retaining valve only.

Empty Car Testing ProcedureFollowing test can only be conducted on an empty

car.• After completion of loaded car test, remove test handle and

replace machine screw and lock washer.

• Do not over-tighten, as no seal is required at this point.

• Make 20 psi reduction using single car test device. With brakes applied, check to see that indicator stem has extended, indicating that empty load valve is in empty mode. (See Figure 5).

• Release brakes by placing single car test device handle into Position No. 1. Brake cylinder piston should retract and air should be heard exhausting through retaining valve and possibly through empty load valve vent protector as well. Indicator stem should no longer extend.

Note: If empty / load valve does not pass above tests, or is damaged or defective, it must be replaced with reconditioned or new valve body.

Downstream (6200)

Charged

RelativePressure

Brake Pipe

ControlValve

Reservoir

Aux Emergency

Brake Cylinder

Downstream (6200)

Minimum ApplicationRelativePressure

Brake Pipe

ControlValve

Reservoir

Aux Emergency

Brake Cylinder

Downstream (6200)

Full Service – Car Loaded

RelativePressure

Brake Pipe

ControlValve

Reservoir

Aux Emergency

Brake Cylinder

Downstream (6200)

Emergency – Car Loaded

RelativePressure

Brake Pipe

ControlValve

Reservoir

Aux Emergency

Brake Cylinder

Downstream (6200)

Full Service – Car Empty

RelativePressure

Brake Pipe

ControlValve

Reservoir

Aux Emergency

Brake Cylinder

Downstream (6200)

Emergency – Car Empty

RelativePressure

Brake Pipe

ControlValve

Reservoir

Aux Emergency

Brake Cylinder

Downstream (6200)

Valve Detail – Car Loaded

Indicator

Product pushes

against diaphragm

Diaphragm pushes rod, forcing

spool to cut off port to reservoir.

With port sealed, air flows through

the valve into the brake cylinder

Downstream (6200)

Valve Detail – Car Empty

Car Body

Indicator

No product

With reservoir port open,

proportional air fills the

reservoir.

Figure 5

Truck Mounted Brake System

Conventional Brake System

EMPTY/LOAD DEVICE TRAINING MODEL SERIES 6200, 6600, & ENX.

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