3.5.7 student book © 2004 propane education & research councilpage 1 following the proper...

3.5.7 Student Book © 2004 Propane Education & Research Council

Following the proper procedures for filling bobtails is essential to a safe and efficient loading operation .

In this module you will learn to identify:

1. Attendance requirements during the loading process

2. Safety procedures during the loading process

3. Steps for propane transfer using the plant pump to fill the bobtail

3.5.7 Loading a Bobtail

3.5.7 Student Book © 2004 Propane Education & Research Council Page 1

Loading Attendance Requirements

U.S. Department of Transportation regulations require that qualified persons be “in attendance” throughout the process of loading a cargo tank motor vehicle.

The person who is responsible for loading the cargo tank is also responsible for ensuring that it is so attended.

A person is “qualified” if he/she

• has been made aware of the nature of the hazardous material• has been instructed on the procedures to be followed in

emergencies

• is authorized to move the cargo tank

• has the means to do so .



Identifying Safety Procedures During the Loading Process— in addition to the regulatory requirements, the person performing cargo tank loading operations should be:

• In a position to monitor the filling of the cargo tank

• Alert for any abnormal operating condition or emergency

• Aware of the activities of other persons in or near the transfer area

• In a location that allows for quick response to abnormal operating conditions or activation of emergency

shutdown systems, and rapid evacuation from the area should the need arise.



Proper and safe procedures prior to the filling operation include:

a) Before moving the vehicle to the loading bulkhead, check for any obstacles that might create an unsafe condition.

b) Remove the chock blocks from the wheels and store them temporarily on the vehicle.

c) Check the PTO to ensure it is disengaged.

d) After starting the engine, ensure all instrumentation indicates normal operation.



Proper and safe procedures prior to the filling operation include:

e) Position the bobtail at the loading bulkhead in a way that maximizes the shearing effect of the hoses and piping should a pull-away occur. The fill connection on the cargo tank should be at least 10 feet from the nearest bulk storage container.

f) Engage the parking brake and turn off the engine.

g) Place chock blocks in front and behind a rear wheel to prevent movement.


Using the Plant Pump to Fill the Bobtail

Step 1: Position the bobtail.

Step 2: Set the liquid level gauges on the bobtail. • Determine the maximum permitted filling level by obtaining the specific gravity of your propane from shipping papers and observing the liquid propane temperature on the thermometer located either in the bobtail, or in the propane storage container at the plant. • When a storage container is filled by volume, the filling operation is stopped when the volume of the liquid inside the container reaches a certain percent of the container's water capacity. This is determined by a fixed maximum liquid level gauge, which extends inside the container and measures the level of the liquid.



Fixed Maximum Liquid Level Gauge

Figure 1. Fixed Maximum Liquid Level Gauge



Variable Liquid Level Gauges

Figure 2. Rotary Gauge



• Temperature and specific gravity are essential when using a rotary gauge. The temperature of the propane can be determined from the thermometer installed in the supply container. The specific gravity can be obtained from the plant receiving records. If the specific gravity information is not available, use 0.508 as the specific gravity for propane.

• When rotary gauges are set, they operate the same as fixed liquid level gauges. During the filling operation, propane vapor vents through the dip tube and bleeder valve into the atmosphere. When the liquid in the cargo tank reaches the bottom of the dip tube, a steady stream of white mist sprays out of the bleeder valve, indicating the maximum permitted filling level has been reached.



If the specific gravity of the propane liquid is 0.508 and its temperature is 60°, by setting the indicator arm so that it crosses the set point, the maximum filling level of 88% is indicated.

Figure 3. Rotary Gauge Face

3.5.7 Student Book © 2004 Propane Education & Research Council Page 5 & 6


The float gauge consists of a float in the container that moves up and down with the liquid. The filling operation is stopped when the pointer indicates it has reached the set point on the gauge face.

Figure 4. Cargo Tank Float Gauge Face



Step 3: Connect the Fill and Vapor Equalizing Hoses. • To maintain pump efficiency when transferring liquid between bulk storage tanks and cargo tanks the use of the vapor equalizing hose is recommended. • Before making the connection, make sure all sources of ignition within 25 feet of the transfer point are removed. Internal combustion engines within 15 feet of the point of transfer must be shut down while transfer operations are in progress, with exceptions as listed in NFPA 58. • Carefully inspect the liquid and vapor transfer hose assemblies, using the rejection criteria. If any defect is found, discontinue the loading operation, notify your supervisor and do not resume loading until the defect has been eliminated.



Step 3: Connect the Fill and Vapor Equalizing Hoses. • Connect the liquid plant hose-end valve to the fill valve on the bobtail.

Once the connector is hand-tight, turn the connector an additional ¼ to 1/8 turn using a spanner wrench, tapping the handle of the spanner wrench with the palm of a gloved-hand.

•If leakage exists, close the hose end valve and disconnect the ACME adapter after the connection has bled down and is de-pressurized. Examine the condition of the O-ring or flat gasket in the filler adapter and replace as needed.



Figure 5a. Excessive Thread Wear

Figure 5 b. New ACME Thread Profile & Worn ACME Thread Profile

3.5.7 Student Book © 2004 Propane Education & Research Council Page 7 & 8


Step 4: Sniff Test to Verify Propane Odorization.

• DOT regulations and NFPA 58 require that propane be odorized prior to transportation to the bulk plant. As a verification of odorization, vent a small quantity of liquid through a #54 vent. Close the vent and sniff immediately after the liquid vaporizes. • If you cannot smell propane odorant – DO NOT LOAD THE Bobtail. Contact your supervisor immediately after disconnecting and securing the transfer hoses in their storage racks. TELL OTHERS IN THE AREA NOT TO LOAD UNTIL APPROVED BY THE FACILITY MANAGER OR SUPERVISOR .



Step 5: Fill the Bobtail. • A qualified person must be present at the transfer point to handle emergencies and monitor the condition of the transfer system at all times while hoses are connected. • Ensure all liquid and vapor valves are fully open in the transfer piping between the plant storage containers and the bulkhead and on the cargo tank.• Start the plant transfer pump. Listen for any unusual pump noise.• Continue the transfer process until a steady white mist fog is first emitted from the gauge vent valve, then immediately shut down the pump, close the ESVs and the hose end valves.



Step 5: Fill the Bobtail. • If a leak or fire develops and it is safe to do so, close all ESVs immediately and stop the pump by moving quickly to a remote emergency shutdown station and activating the emergency shutdown control.

Stay away from the transfer area so long as leaking gas or fire is present. Warn others in the bulk plant.

AVOID BECOMING TRAPPED OR ALLOWING OTHERS TO BECOME TRAPPED WITHIN FENCED AREAS WHERE LEAKING GAS IS PRESENT.



Step 6: Disconnect the Transfer Hoses and Prepare the Bobtail for Travel.

If for any reason the transfer operation is interrupted, or the attendant must leave the area, the pump must be shutdown and transfer hoses disconnected. DO NOT leave transfer hoses connected to a Bobtail while unattended by a qualified person.

3.5.7 Student Book © 2004 Propane Education & Research Council Pages 10 - 13

Time to See If You Got the Key Points of This Module…

• Complete the Review on page 10 & 11.

• See if you are ready for the Certification Exam by checking off the performance criteria on page 12 & 13.

3.5.7 student book © 2004 propane education & research councilpage 1 following the proper...

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