3.7.7 Student Book © 2004 Propane Education & Research CouncilPage 1 Replacing DOT IM tank valves...

3.7.7 Student Book © 2004 Propane Education & Research Council

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:

1. NFPA requirements for DOT IM tank valves and fittings

2. Precautions for tank valve and fitting replacement

3. Procedures for replacing DOT IM tank valves and fittings

3.7.7 Replacing Valves and Fittings in DOT Intermodal Tanks

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

Identifying NFPA Requirements for DOT IM Tank Valves and Fittings

NFPA 582002 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.

Relief valve replacement and dip tube replacement require

examination of the tank data plate.

3.7.7 Student Book © 2004 Propane Education & Research Council Page 1 & 2

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


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 .


Identifying Procedures for Replacing DOT IM Tank Valves and Fittings

Steps in Replacing DOT IM Tank Valves and Fittings

Step 1: Wearing personal protective equipment, reduce the vapor pressure in the tank to near atmospheric pressure

Step 2: Select and prepare the appropriate replacement valve or fitting by applying an approved pipe thread-sealing compound as illustrated in Figure 1.

N O P ip e T h rea d -S ea lin g C o m p o u n dH e re

P ip e T h re a d -S e a l in g C o m p o u n dH e re

Figure 1a. Applying PipeThread Sealing Compound

Figure 1b. Do Not Apply to Leading Threads


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.




Steps in Replacing DOT IM Tank Valves and Fittings

Step 3: Check to be sure that the vapor pressure inside the tank is at or only slightly above atmospheric pressure by opening and closing the fixed liquid level gauge. Using suitable valve wrenches or ratchet handle and sockets, remove the defective valve or fitting.

Step 4: Without delay, insert and hand-tighten the replacement valve or fitting. Tighten with valve wrench or ratchet handle and socket. DO NOT APPLY EXCESSIVE FORCE OR OVER TIGHTEN. Over tightening may damage the new valve, fitting or tank coupling threads.

Figure 2. Valve Tools

•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



Selecting Relief Valves for DOT IM Tanks

Figure 3. Data Plate for Underground DOT IM Tank


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 2.3.2.4 from NFPA 58, 1998 Edition



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

Identifying Procedures for Replacing DOT IM Tank Valves and Fittings 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)

3.7.7 Student Book © 2004 Propane Education & Research Council Pages 8 & 9

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.

3.7.7 Student Book © 2004 Propane Education & Research CouncilPage 1 Replacing DOT IM tank valves...

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