Question 1

Cleanliness of Nitrous Oxide Cylinders and Accessories

newsadmin · Accepted Answer

Ignition of combustible materials will happen more readily in the presence of nitrous oxide. This is why the Department of Transportation (DOT) requires that cylinders containing nitrous oxide, meet the following requirement listed in the “Code of Federal Regulations” (CFR-49) section 173.304 “Charging of Cylinders with liquefied Compressed Gas” paragraph (a)(4)(ii);

Each cylinder must be cleaned in compliance with the requirements of Federal Specification RR-C-901c paragraph 3.7.2 and 3.8.2. Cleaning agents equivalent to those specified in RR-C-901c may be used; however, any cleaning agent must not be capable of reacting with oxygen. One cylinder selected at random from a group of 200 or less cleaned at the same time must be tested for oil contamination in accordance with Specification RR-C-901c paragraph 4.4.2.3 and meet the standard of cleanliness specified.

Cylinders manufactured by Catalina Cylinders for nitrous oxide service are cleaned and tested in accordance with RR-C-901-c at the time of manufacture. Cylinders that are manufactured for charges or fills other than oxygen and nitrous oxide have not been cleaned for oxygen or nitrous oxide service. Conversion of cylinders not cleaned for oxygen or nitrous oxide service can be done but is not recommended by Catalina Cylinders. If such cylinders are to be converted to nitrous oxide service, the cylinders must be cleaned as if for oxygen service prior to filling with nitrous oxide. Also, all cylinder accessories (i.e. valves, regulators, etc.) that will come into contact with the nitrous oxide charge must be compatible with oxygen and cleaned as if for oxygen service. The Compressed Gas Association (CGA) has two publications, pamphlet G-4.1 “Cleaning Equipment For Oxygen Service” and a directory “Directory of Cleaning Agents for Oxygen Service” that we recommend if such cleaning is to be done. Please note that after all cleaning operations it is recommended that the cylinder be dried completely to reduce the chance of corrosion from occurring.

Question 2

Crown Markings of a Nitrous Oxide Cylinder

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The Department of Transportation (DOT) and Transport Canada (TC) require that cylinders made in compliance to their specifications be marked on the crown with certain information. Over the years the format used by Catalina Cylinders and Catalina East Division to display these markings has changed a few times. Shown below is an example of the current crown marking stamped on the standard 10 # N2O cylinders manufactured at Catalina Cylinders, Garden Grove, CA. Under the example of the crown marking is a list of each of the specific crown markings, followed by a brief explanation of that marking. The descriptions of the markings are the same regardless of the different stamping formats used over the years.

Example of crown markings on a 10# N2O Cylinder:

DOT-3AL1800 ELXXXXXXX M4002 MMCYY NO10 U18 TC-3ALM124 CATALINA

Marking	Description
DOT-3AL	The U.S. regulatory authority, the Department of Transportation (DOT), and specification, 3AL, to which the cylinder is manufactured in compliance (required mark).
1800	The service pressure, in pounds per square inch (psi), of the cylinder (required mark).
ELXXXXXXX	The serial number of the cylinder. For Catalina Cylinders - West, the serial number prefix of “EL” is specific to the 10# N2O cylinders followed by a seven digit number.
M4002	The M-number or Manufacturers Number issued by the DOT to the manufacturer, Catalina Cylinders - West.
MMCYY	The original hydrostatic test date of the cylinder, month followed by year, performed at the time of manufacture of the cylinder. The “C” represents the symbol of the Independent Inspection Agency (IIA) performing the inspection of and certifying the acceptance of the cylinder at the time of manufacture (required mark).
NO10	The cylinder identifier (product name). It identifies the market, “NO” for Nitrous Oxide, and capacity “10” for a capacity of 10# of N2O charge, of the cylinder.
U18	The cylinder outlet thread designation as specified in CGA V-19.
TC-3ALM	The Canadian regulatory authority, Transport Canada (TC), and specification, 3ALM, to which the cylinder is manufactured in compliance (required mark).
124	The service pressure of the cylinder expressed in metric units, bars (required mark).
CATALINA	The name of the manufacturer of the cylinder.

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Question 3

High Temp Exposure

newsadmin · Accepted Answer

In CGA Pamphlet G-8.1, “Standards For Nitrous Oxide Systems at Consumer Sites“, it states that nitrous oxide cylinders should not be exposed to temperatures in excess of 125^oF (52^oC) due to the highly combustible nature of nitrous oxide. In CGA pamphlet C-6.1, “Standards For Visual Inspection Of High Pressure Aluminum Compressed Gas Cylinders“, it states that cylinders heated to metal temperatures in excess of 350^oF (176^oC) must be condemned. Common evidence of exposure to elevated temperatures that may heat the metal temperature to 350^oF (176^oC) include:

discoloration, charring, or blistering of the cylinder paint, protective coatings or labels;
distortion of the cylinder;
melting of non-metallic (i.e. plastic, etc.) valve components;
activation of valve pressure relief device; or
activation of a heat indication system

Catalina Cylinders recommends that if there is evidence, or it is believed, that a nitrous oxide cylinder has been exposed to temperatures above 125^oF (52^oC) but the temperature of metal of the cylinder is not believed to have reached 350^oF (176^oC) for any duration of time, the cylinder must still be subjected to hydrostatic testing or condemned. A cylinder that has been exposed to temperatures great enough to change the temper of the cylinder could show an increase in total or permanent expansion as measured during hydrostatic testing. Cylinders showing unusually high total expansion or exceeding the regulatory limits for the relationship of permanent expansion to total expansion (i.e. DOT = 10% and TC = 6%) should be condemned. DOT 3AL and DOT 4E aluminum cylinders subjected to fire must be removed from service according to section (f) (4) of CFR 49 part 173.34, “Qualification, Maintenance, and Use of Cylinders“. No testing for acceptance or re-heat treatment is authorized.

Question 4

High Temperature Exposure of Nitrous Oxide Cylinders

newsadmin · Accepted Answer

In CGA Pamphlet G-8.1, “Standards For Nitrous Oxide Systems at Consumer Sites“, it states that nitrous oxide cylinders should not be exposed to temperatures in excess of 125^oF (52^oC) due to the highly combustible nature of nitrous oxide. In CGA pamphlet C-6.1, “Standards For Visual Inspection Of High Pressure Aluminum Compressed Gas Cylinders“, it states that cylinders heated to metal temperatures in excess of 350^oF (176^oC) must be condemned. Common evidence of exposure to elevated temperatures that may heat the metal temperature to 350^oF (176^oC) include:

discoloration, charring, or blistering of the cylinder paint, protective coatings or labels;
distortion of the cylinder;
melting of non-metallic (i.e. plastic, etc.) valve components;
activation of valve pressure relief device; or
activation of a heat indication system

Catalina Cylinders recommends that if there is evidence, or it is believed, that a nitrous oxide cylinder has been exposed to temperatures above 125^oF (52^oC) but the temperature of metal of the cylinder is not believed to have reached 350^oF (176^oC) for any duration of time, the cylinder must still be subjected to hydrostatic testing or condemned. A cylinder that has been exposed to temperatures great enough to change the temper of the cylinder could show an increase in total or permanent expansion as measured during hydrostatic testing. Cylinders showing unusually high total expansion or exceeding the regulatory limits for the relationship of permanent expansion to total expansion (i.e. DOT = 10% and TC = 6%) should be condemned. DOT 3AL and DOT 4E aluminum cylinders subjected to fire must be removed from service according to section (f) (4) of CFR 49 part 173.34, “Qualification, Maintenance, and Use of Cylinders“. No testing for acceptance or re-heat treatment is authorized.

Question 5

Polishing of Nitrous Oxide Cylinders

newsadmin · Accepted Answer

Catalina Cylinders does not endorse the practice of polishing cylinders.

Polishing methods can subject cylinders to excessive localized heating as well as removal of material from cylinder walls. Due to the physical changes as a result of polishing cylinders, all DOT and TC certificates of conformance, the manufacturing test reports, would be nullified.

Catalina Cylinders recommends that nitrous oxide cylinders be powdercoat painted in a controlled environment at our facilities at the time of manufacture.

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