3.1.5 Student Book © 2004 Propane Education & Research CouncilPage 1 3.1.5 Identifying Procedures...

3.1.5 Student Book © 2004 Propane Education & Research Council

3.1.5

Identifying Procedures for Evacuating ASME Tanks at Bulk Plants or at Customer

Locations

A full understanding of the operation of the liquid evacuation process is essential in order to remove the liquid from domestic tanks safely.

In this module you will learn to:(1) Identify U.S. DOT regulations pertaining to evacuating

ASME tanks (2) Identify hazards and safety precautions associated with

evacuating propane liquid(3) Select the proper equipment for evacuating the tank (4) Identify procedures for evacuating propane from a

stationary ASME tank

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

U.S. DOT Regulations Pertaining To Evacuating ASME Tanks

49 CFR § 173.315 (j) storage containers for liquefied petroleum gas for permanent installation on consumer premises may be shipped by private motor carrier only under the following conditions:

1. Each container must be constructed in compliance with the requirements of the ASME code

2. Each container must be equipped with safety devices in compliance with the requirements for safety devices on containers as specified in NFPA pamphlet no. 58

4. …Containers shall not be shipped when charged with liquefied petroleum gas to more than 5 percent of their water capacity.

5. Storage containers of less than 1,042 pounds water capacity (125 gallons) may be shipped when charged with liquefied

petroleum gas in compliance with DOT filling density.


Hazards and Safety for Evacuating Propane Liquid

Hazards Associated with Liquid Propane Evacuation

1. Exposure to liquid propane can result in freezing of the skin.

2. Exposure to flammable gas and other materials at high pressure

3. Potential ignition of flammable gas



Precautions for Liquid Propane Evacuation

1. All hoses used in the evacuation procedure must be designed and listed for use with liquid propane (1750 psig bursting pressure, and 350 psig working pressure).

2. All sources of ignition within 25 feet of the point of transfer must be removed, extinguished, or turned off for the duration of the operation. Internal combustion engines within 15 feet (5m) of the point of transfer must be shut down while transfer operations are in progress, except for engines on transfer equipment and others as listed in NFPA 58.



Precautions for Liquid Propane Evacuation

3. At least one recently inspected fire extinguisher, having a minimum capacity of 18 lb. dry chemical with a B:C rating must

be within easy reach during the entire operation.

4. A qualified individual must be present at the operation during the entire evacuation procedure.

5. Heavy vinyl safety gloves and eye protection should be worn during this entire operation.

3.1.5 Student Book © 2004 Propane Education & Research Council Pages 2 & 3

Selecting Proper Equipment for Tank Evacuation

CTMV Pump or Portable Compressor

• If a CTMV (cargo tank motor vehicle) pump is used, the liquid transfer hose must be as short as possible, but no

longer than 50 feet.

• If the CTMV cannot be positioned any closer, a small portable compressor should be used.

• If a portable compressor is not available, it may be necessary to move the ASME tank to a different location on the site, closer to the CTMV. When an ASME tank

containing more than 5% liquid is lifted, the tank’s lifting lugs should not be used. Instead, suitable lifting slings that have sufficient weight-bearing capacity ratings should be used to cradle-lift the tank.


Selecting Proper Equipment for Tank Evacuation

Liquid Transfer Hose

Figure 1. Liquid Transfer Hose


Proper Equipment for Tank Evacuation

Vapor Hose —

1. If the cargo tank pump is used, the vapor equalizing hose should be installed on the ASME tank vapor equalizing valve to limit pump cavitation.

2. If a portable compressor is used, two vapor hoses are required:• For connection to the cargo tank vapor equalizing

connection (compressor suction)• For connection to the ASME tank vapor equalizing

connection (compressor discharge)



Vapor Hose —

Figure 10. Evacuating ASME Tank Using a Portable Compressor(Page 11)



Vapor Hose — If the tank is not equipped with a vapor equalizing valve, install a purging adapter (Figure 2) in the vapor service valve outlet.

Figure 2. POL to Male ACME Purging Adapter



Additional Adaptors & Valves— The liquid propane in the stationary ASME tank can be removed either through a top or bottom opening. A special unloading adapter (Figure 3) is needed to operate the filler valve.

Figure 3a. Sherwood 902A Figure 3b. Fisher M450A



Additional Adaptors & Valves— The liquid propane in the stationary ASME tank can be removed either through a top or bottom opening. A special unloading adapter (Figure 3) is needed to operate the filler valve.

Figure 3c. Rego 3119A Figure 3d. Rego 3120



Actuated Liquid Withdrawal Excess Flow Valves —

Figure 4. Actuated Liquid Withdrawal Excess Flow (Evacuation) Valve



Actuated Liquid Withdrawal Excess Flow Valves —Withdrawal valves may be installed in the bottom, top, or side depending on the internal construction of the tank.

Figure 5. Mounting Options for Withdrawal Valves



Actuated Liquid Withdrawal Excess Flow Valves —During the evacuation process, the units also serve as excess flow valves. In some cases, a damaged seat may allow an excessive amount of liquid to be discharged when the closing cap is loosened. A bleed hole in the closing cap has been provided to vent the liquid before the cap is completely unscrewed.

If a significant amount of liquid continues to be blown from under the closing cap for more than 30 seconds, it can be assumed that the internal seat will not prevent a dangerous amount of gas from escaping. IF IN DOUBT, DO NOT REMOVE THE CLOSING CAP. This is particularly true if the tank is located in a congested area, such as a mobile home park. Should only vapor be leaking from under the cap, the connection to the liquid withdrawal valve can usually be made.



Actuated Liquid Withdrawal Excess Flow Valves — A transfer valve with a machined adapter (Figure 6) must be used to evacuate a tank through a liquid evacuation valve.

Figure 6. Transfer Valve with Machined Adapter



Exposure of body tissues to liquid propane when installing transfer and withdrawal valves can result in frostbite or freeze burn. Protect your hands and other body parts with appropriate PPE. Special care is required with angle valves to ensure that they do not direct liquid toward people or ignition sources.

WARNING


Procedures for Evacuating Propane from a Stationary ASME Tank

On most old style LP-gas containers larger than 125 water gallon capacity and manufactured prior to July 1, 1961, a liquid withdrawal (evacuation) internal dip tube was attached to the bottom of the filler valve by the manufacturer and extended to the bottom of the container. (Figure 7)

Since 1961, container manufacturers have installed a separate valve called an actuated liquid withdrawal excess flow valve for liquid evacuation of domestic containers. An internal withdrawal tube extends to a point near the bottom of the container and connects to the valve (Figure 8).



Figure 7. Older ASME Tank With Fill to Liquid Space—Evacuation Through Filler Valve

O LDTYPE

Combined Fille r Valve /Liquid W ithdrawal Tube

Vapor S ervice, Equalizing,Fixed Maxim um Liquid Level GaugeMultivalve

LiftingLug



Figure 8. Newer ASME Design with Separate Evacuation Fitting

VaporMultivalve

Filler Valve

Evacuation Valve/Liquid WithdrawalTube

LiftingLug

Evacuation Valve

Multivalve

Filler Valve

Evacuation Valve/Liquid WithdrawalTube

Lug

Evacuation ValveO p tion a l L oca tio n



Information outlining features of liquid withdrawal valves, unloading adapters and installation methods is given in the Supplemental Information section of this module. Always read and follow manufacturers’ instructions for use. Use the adapters specified by manufacturers and wear personal protective equipment while evacuating propane containers. Remember at all times that you are working with a pressurized flammable gas. Follow all company-specific procedures that apply.



Figure 9. Portable Propane Compressor



Determine the Quantity of Propane to be Transferred.

1. Read the percent volume indicated by the rotary or float gauge on the delivery vehicle cargo tank.

2. Multiply the percent volume indicated by the water capacity of the cargo tank on the delivery vehicle.

3. Add the water capacity of the stationary ASME tank to be evacuated to the volume of propane in the delivery vehicle's cargo tank.

4. The total amount must not be higher than the maximum permitted filling level for the cargo tank on the delivery vehicle.


Compressor Transfer Method

Step 1: Position the bulk delivery vehicle to receive propane.

Figure 10. Evacuating ASME Tank Using a Portable Compressor

The delivery vehicle should be approximately 10 feet from the suction side of the compressor. The maximum distance between the compressor and the two tanks will depend on the length of the vapor hose.



Step 2: Connect a transfer valve to the inlet of the

withdrawal valve on the stationary tank.

Step 3: Close all valves in the liquid transfer line.

Step 4: Lay out the liquid transfer hose between the stationary tank and the cargo tank.

Step 5: Connect one end of the liquid transfer hose to the outlet of the transfer valve and the other end to the fill connection located on the cargo tank of the delivery vehicle.



Step 6: Connect the vapor hoses between the compressor and tanks. Connect the discharge hose between the discharge side of the compressor and the vapor equalizing valve (or purging adapter) on the stationary tank.

Step 7: Pressure Test the Vapor and Liquid Hoses. Slowly open one valve at a time, starting with the transfer valve in the stationary tank, to pressure test the liquid supply line. Check all connections downstream to the next closed valve for leakage once a valve is opened. Slowly open each valve downstream one at a time after each section of line is considered tight. Close all valves in the line and make repairs, if any leaks are detected.



Step 8: Transfer as much liquid as possible from the stationary ASME propane tank to the cargo tank. Read and follow compressor manufacturer instructions. Typically, portable compressors are run only for short time periods of one or two minutes to create a pressure differential between the two tanks.

Step 9: Bleed Down and Disconnect all Hoses. During this procedure, liquid propane gas trapped in the hose connections is bled off to the atmosphere. Any liquid propane gas trapped in the hose itself (between shut-off valves) must be bled off at the customer location.



CAUTION:If the excess-flow valve does not "slug" shut, immediately close the transfer valve. Do not remove the transfer valve until the pressure in the tank has been reduced to 0 psig. Once the pressure has been reduced, the withdrawal valve must be serviced before the ASME tank is returned to service.

CAUTION:Do not cross thread the plug during installation. Also, avoid tightening or moving the withdrawal valve when installing the plug.


Cargo Tank Pump Transfer Method

Step 1: Position the CTMV as close as permitted to the stationary ASME tank being evacuated, usually 10 to 50 feet away, depending on the length of the hose.

Step 2: Connections for transferring propane using the auxiliary pump inlet are illustrated in Figure 11.



Figure 11. Evacuating ASME Tank Using the Auxiliary Pump Inlet



Step 3: Lay the liquid transfer hose between the stationary tank and the bulk delivery vehicle.

Step 4: Connect one end of the liquid transfer hose to the outlet on the unloading adapter or the transfer valve on the stationary tank. Connect the other end to the auxiliary adapter on the delivery vehicle.

Step 5: Connect one end of the delivery hose to the fill connection on the delivery vehicle.

Step 6: Connect the vapor equalizing hose between the equalizing connection on the tank of the delivery vehicle and the vapor equalizing valve (or purging adapter) on the stationary tank.



Step 7: Start the engine and engage the cargo tank transfer pump.

CAUTION:The pump should operate at the slowest possible speed. Over-speeding will only increase wear on the pump.



Step 8: Observe the liquid level gauges on the ASME tank and the cargo tank. Stop the pump immediately when there is no indication of liquid transfer, the transfer pump becomes noisy or suddenly increases in speed, or when the ASME tank liquid level gauge reads 5 percent.

Step 9: Check the float gauge in the ASME tank to be sure that most of the liquid propane gas has been removed. The excess-flow valve in the evacuation valve could have slugged if the gauge indicates more than 5%. Allow the excess-flow valve to reset and restart the pump if this is the case. Monitor the flow with the sight gauge.



Step 10: When liquid has been lowered to the 5% level, shut down the pump. Close all valves in the liquid transfer hose, including the transfer valve and any shut-off valve between the pump-off inlet and the delivery hose.

Step 11: Close all valves in the CTMV delivery hose assembly and at the fill connection of the cargo tank.

Step 12: Close all valves in the vapor equalizing hose. Close the vapor service valve in the stationary ASME tank (w/purging adapter attached), if applicable.



Step 13: Bleed Down and Disconnect all Hoses.

CAUTION:If the excess-flow valve does not "slug" shut, immediately close the transfer valve. Do not remove the transfer valve until the pressure in the tank has been reduced to 0 psig. Once the pressure has been reduced, the withdrawal valve must be serviced before the ASME tank is returned to service.

CAUTION:Do not cross thread the plug during installation. Also, avoid tightening or moving the withdrawal valve when installing the plug.

3.1.5 Student Book © 2004 Propane Education & Research Council Pages 19 - 21

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

• Complete the Review on pages 19 & 20.

• See if you are ready for the Certification Exam by checking off the performance criteria on page 21.

3.1.5 Student Book © 2004 Propane Education & Research CouncilPage 1 3.1.5 Identifying Procedures...

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