3.7.4 student book © 2004 propane education & research councilpage 1 3.7.4 identifying testing...

3.7.4 Student Book © 2004 Propane Education & Research Council

3.7.4

Identifying Testing Procedures for Anhydrous

Ammonia (NH3) Contamination

Because many propane marketers sell both propane and anhydrous ammonia, it is important the ammonia not contaminate the propane vapor. For safety purposes, it is important to understand the testing procedures for anhydrous

ammonia contamination. In this module you will identify:

(1) Physical properties, hazards & characteristics of anhydrous ammonia

(2) Procedures for testing for anhydrous ammonia contamination

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

Physical Properties, Hazards & Characteristics of Anhydrous Ammonia

Anhydrous ammonia (NH3) is a hazardous material with the

following physical properties:

1. At room temperature and atmospheric pressure, anhydrous ammonia is a pungent, colorless gas,

approximately 40% lighter than air.

2. Compressed and cooled, it is a colorless liquid about 68% as heavy as water.

3. Its boiling point at atmospheric pressure is -28°F.





4. Anhydrous ammonia in closed, pressurized containers behaves similarly to propane.

5. Anhydrous ammonia is an inhalation hazard; at a concentration of more than 5000 parts per million, it will disable a person and suffocation results. Exposure to body tissue is harmful, resulting in caustic burns. Exposure to liquid ammonia results in frostbite. Eye exposure in concentration causes blindness.



Figure 1. Pressure Gauge and Valve on Anhydrous Ammonia Nurse Tank





6. Anhydrous ammonia is corrosive, especially to brass valves and fittings, and other metals that contain alloys

of copper and zinc.

7. Under certain conditions it may be flammable.

8. It is highly chemically reactive, and in the presence of other materials may be highly explosive.

9. Anhydrous ammonia in the presence of water will burn body tissue.



Warning: Exposure to anhydrous ammonia is dangerous and can result in injury or death.

Always use proper personal protective equipment (PPE) and handling procedures when working around it.

Be sure you read a current material safety data sheet (MSDS) provided by the chemical’s supplier & understand the information it contains.

Know how to react in the event of a chemical release or exposure.


Procedures For Testing Propane For Anhydrous Ammonia Contamination

When it is known or suspected that a container may have been used in anhydrous ammonia service, a test should be done to assure that all residue is gone.

Even though the container may have been thoroughly purged with water, some NH3 vapor may still be mixed with propane vapor. If this is allowed to remain in the container, it can easily damage or destroy any copper or brass equipment in the propane system

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


Step 1: Obtain a bottle of distilled water, tweezers, a clean, soft dry cloth, and a package of red litmus paper.

Step 2: Remove work gloves.

Step 3: Using a clean, dry cloth, wipe off the tweezers thoroughly.

Step 4: Using the tweezers, carefully remove one piece of litmus paper from the package.

Caution!Do not allow the litmus paper to touch any part of the hand or any portion of the tank or tank valves. This can easily cause the paper

to accidentally turn blue.



Step 5: Carefully soak the red litmus paper with distilled water.

Step 6: Carefully open the service valve, fixed maximum liquid level gauge, or any valve that is in the vapor space of the container.

Step 7: Hold the paper directly in the stream of propane vapor for at least 30 seconds.



Step 8: Close the gauge or service valve.

• If the litmus paper turns blue, repeat the test using a new piece of litmus paper.

• If the propane vapor is contaminated with anhydrous ammonia, the litmus paper will turn blue, and the container will have to be

purged with water as outlined in module 3.1.13.

• After purging, repeat all steps through the litmus paper test.

• A small concentration of anhydrous ammonia in the propane will cause the paper to turn blue.

• If pure propane vapor is discharged on the red litmus paper, the paper will remain red.



Step 9: If the tank will not be filled with propane immediately, re-pressurize the tank with propane vapor (15 to 20 psig).

Step 10: Store all tools, supplies, and equipment.

Note:If contamination is found, the container must be evacuated, cleaned and purged following the instructions in module 3.1.13, “Converting ASME Tanks in Ammonia Service to Propane

Service.” (All brass cylinder valves & fittings must be replaced after the cylinder is cleaned & purged.)

3.7.4 Student Book © 2004 Propane Education & Research Council Pages 4 & 5

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

• Complete the Review on page 4.

• See if you are ready for the Certification Exam by checking off the performance criteria on page 5.

3.7.4 student book © 2004 propane education & research councilpage 1 3.7.4 identifying testing...

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