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3.7.7. Replacing Valves and Fittings in DOT Intermodal Tanks. Replacing DOT IM tank valves and fittings requires careful application of precautions and proper selection of valves and fittings . In this module you will learn to identify: NFPA requirements for DOT IM tank valves and fittings

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3.7.7

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3.7.7

Replacing Valves and Fittings in DOT Intermodal Tanks

  • Replacing DOT IM tank valves and fittings requires careful application of precautions and proper selection of valves and fittings.

  • In this module you will learn to identify:

    • NFPA requirements for DOT IM tank valves and fittings

    • Precautions for tank valve and fitting replacement

    • Procedures for replacing DOT IM tank valves and fittings


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NFPA 58

2002 Edition

Valve and fitting requirements for DOT IM tanks are found in columns 5 and 6 of Table 2.3.3.2(a) of NFPA 58, LP-Gas Code. Specific valve and fitting requirements are found in other sections of Chapter 2.

Identifying NFPA Requirements for DOT IM Tank Valves and Fittings

Relief valve replacement and dip tube replacement require examination of the tank data plate.


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Identifying Precautions for Tank Valve and Fitting Replacement

It is imperative that plant personnel who perform this operation

apply general safety precautions, including:

  • Never move stationary DOT IM tanks containing propane indoors or into any enclosed space

  • Tank valve or fitting replacement should never be done near ignition sources (no ignition sources within 25 feet), nor should they be done upwind of any open flame

  • Never remove a valve or fitting under propane pressure

  • Wear suitable personal protective equipment


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Identifying Precautions for Tank Valve and Fitting Replacement

It is imperative that plant personnel who perform this operation

apply general safety precautions, including:

  • Verify that the replacement valve or fitting is proper for the tank before removing existing valve(s) or fitting(s).

  • Use suitable tools for valve and fitting removal and installation to avoid damage to them, and to prevent damage to tank connections.

  • Remove a valve or fitting only when the replacement has been properly prepared and is in position for immediate installation.

  • Do not leave tank openings open to the atmosphere except for the brief time needed between removing a valve or fitting, and its replacement with the new valve or fitting .


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Steps in Replacing DOT IM Tank Valves and Fittings

Figure 1b. Do Not Apply to Leading Threads

Figure 1a. Applying PipeThread Sealing Compound


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

NOTES:

Relief valves must be properly sized for the DOT IM tank; be sure that the replacement relief valve capacity in cubic feet per minute is equal to or exceeds the requirements for the tank as given in Table 2.3.2.4(a), NFPA 58, 2001 edition. (See Figure 4)

Fixed liquid level gauges and service valves incorporating fixed liquid level gauges must have dip tube lengths that correspond to the length required for the tank in which they are installed. Use a tape measure or ruler to check the dip tube length and be sure that it matches the D.T. length stamped data plate.


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Steps in Replacing DOT IM Tank Valves and Fittings

  • After a replacement valve or fitting is installed in a tank, the tank must be re-pressurized with propane vapor, and checked for leaks. The check for leakage is done with the tank pressurized by brushing or spraying an approved leak detection solution around the valve or fitting, then watching for bubbles. If no bubbles are observed, the solution should be washed off the tank and then the tank is wiped with a clean towel or dry rag

Figure 2. Valve Tools


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Selecting Relief Valves for DOT IM Tanks

Figure 3. Data Plate for Underground DOT IM Tank


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Figure 4. Table 2.3.2.4from NFPA 58, 1998 Edition


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

  • Selecting Relief Valves for DOT IM Tanks

  • Relief valves must be installed to directly communicate with the vapor space of the tank, without bushings, valves or any intermediate fitting installed between the relief valve and the coupling welded into the tank


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Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

  • Installing Fixed Maximum Liquid Level Gauges and Dip Tubes

  • DOT IM tank maximum filling level is based on 80% of tank volume at a propane liquid temperature of 40° F.

  • After installing a filler valve, relief valve or vapor equalizing return valve, be sure that the appropriate weather cap is installed on the valve to prevent moisture and other material from accumulating in the valve opening.

Figure 5a. Data Plate—500 Gallon AG Tank(Dip Tube 10.7 Inches)

Figure 5b. Data Plate—500 Gallon UGTank (Dip Tube 7.5 Inches)


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

  • Complete the Review on page 8.

  • See if you are ready for the Certification Exam by checking off the performance criteria on page 9.


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