3.1.9 Student Book © 2004 Propane Education & Research CouncilPage 1 3.1.9 Replacing Valves and Fittings in ASME Tanks Replacing ASME tank valves and fittings

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

3.1.9Replacing 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


NPFA 58 Specifications for ASME Tank Valves & Fittings

NFPA 58

2001

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.

NFPA 58

2004


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.


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.


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.



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

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 1. Correctly Applying Pipe Thread-Sealing CompoundDo Not Apply to Leading Threads



Step 4: Remove old valve.

Figure 2. Valve Tools



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.


Selecting Pressure Relief Valves for ASME Tanks

Figure 3. Data Plate for Underground ASME Tank



Figure 4. Table 2-3.2.4 from NFPA 58, 2001 Edition



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.


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)


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.


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 Pages 7 & 8

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.

Documents

3.1.9 Student Book © 2004 Propane Education & Research CouncilPage 1 3.1.9 Replacing Valves and Fittings in ASME Tanks Replacing ASME tank valves and fittings