3.1.9
Replacing Valves and Fittings in
ASME Tanks
Replacing ASME tank valves and fittings requires certain
precautions and proper selection of valves and fittings.
Reasons to replace valves and fittings include:
• Damage or leaks
• Improper installation of seals to fittings such as float gauges
or the sealing cap on an evacuation valve that causes a
leak
• Pressure relief valves that are not reseating after venting
excess pressure
In this module you will identify:
(1) NFPA specifications for ASME tank valves and fittings
(2) Precautions for tank valve and fitting replacement
(3) Procedures for replacing ASME tank valves and fittings
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 1
NPFA 58 Specifications for ASME Tank Valves &
Fittings
NFPA 58
2001
NFPA 58
2004
Valve and fitting requirements for ASME tanks are
found in columns 5 and 6 of Table 2.3.3.2(a) of NFPA
LP-Gas Code. Specific valve and fitting requirements
are found in other sections of Chapter 2.
Valve and fitting requirements for ASME tanks are
found in columns 5 and 6 of Table 5.7.7.1 of NFPA
LP-Gas Code. Specific valve and fitting requirements
are found in other sections of Chapter 5.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 1
Precautions for Valve and Fitting Replacement
General safety precautions during valve and fitting replacement include:
1. Never move stationary ASME tanks containing propane indoors
or into any enclosed space.
2. Eliminate ignition sources within 25 feet of the replacement
operation, & the operation should also be performed downwind
of any open flame or ignition source.
3.
Reduce tank vapor pressure to near atmospheric pressure.
4.
Wear suitable personal protective equipment
5. Verifying that the replacement valve or fitting is the correct one
for the tank before removing existing ones.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 1
Precautions for Valve and Fitting Replacement
General safety precautions during valve and fitting replacement include:
6. Use suitable tools for removal and installation to avoid damage
to the valves, fittings, and tank connections.
7. Remove a valve or fitting only when the replacement is ready to
be installed.
8. Keep the tank openings closed to the atmosphere, except for
the brief time needed between removing and replacement of
valves and fittings.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 2
Replacing ASME Tank Valves and Fittings
Step 1:
Select the replacement valve. (See the Note Box
for NFPA 58 requirements for fixed liquid level
gauge dip tubes,)
Step 2:
Reduce the vapor pressure in the tank to
atmospheric pressure.
Step 3:
Prepare the replacement valve or fitting.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 2
Replacing ASME Tank Valves and Fittings
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Figure 1. Correctly Applying Pipe Thread-Sealing Compound
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Do Not Apply to Leading Threads
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 3
Replacing ASME Tank Valves and Fittings
Step 4:
Remove old valve.
Figure 2. Valve Tools
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 3
Replacing ASME Tank Valves and Fittings
Step 5:
Install the new valve according to manufacturer’s
instructions.
•
Immediately insert and hand-tighten the replacement valve
or fitting. Then tighten it with the 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.
•
After a replacement valve or fitting is installed, re-pressurize
the tank with propane vapor, and check for leaks. Brush or
spray an approved leak detection solution around the valve
or fitting, and watch for bubbles. If none are observed, wash
the solution off the tank and dry it with a clean towel or dry
rag.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 4
Selecting Pressure Relief Valves for ASME Tanks
Figure 3. Data Plate for Underground ASME Tank
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 4
Selecting Pressure Relief Valves for ASME Tanks
Figure 4. Table 2-3.2.4 from NFPA 58, 2001 Edition
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 5
Selecting Pressure Relief Valves for ASME Tanks
For an ASME tank having a 97.5 square foot surface area, the 100
square foot line from Table 2-3.2.4 indicates that the replacement
relief valve should have a venting capacity of at least 2340 standard
cubic feet per minute (SCFM) of air.
Relief valves must be installed to be in contact 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. A new weather cap should be installed with the relief valve at
the time of replacement.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 5
Selecting Dip Tubes for Fixed Liquid Level Gauges
Figure 5a.
Data Plate—500 Gallon AG Tank
(Dip Tube 10.7 Inches)
Figure 5b.
Data Plate—500 Gallon UG
Tank (Dip Tube 7.5 Inches)
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 5
Selecting Dip Tubes for Fixed Liquid Level Gauges
Dip tube lengths for the same diameter aboveground and
underground tank are different because of the liquid temperature
used as the standard for the two ASME tank services.
Aboveground tank maximum filling level is based on 80% of tank
volume at a propane liquid temperature of 40° F.
Underground tanks are based on 90% of tank volume at a propane
liquid temperature of 50°F.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 6
Special Valve Installation Procedures
After installing a
• filler valve
• pressure relief valve
• vapor equalizing return valve
be sure the appropriate weather cap is installed on the valve to
prevent moisture and other material from accumulating in the valve
opening.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Page 6
Time to See If You Got the Key Points of
This Module…
• Complete the Review on page 7.
• See if you are ready for the Certification
Exam by checking off the
performance criteria on page 8.
3.1.9 Student Book  © 2004 Propane Education & Research Council
Pages 7 & 8