Rules and Regulations for Safe Handling of Propane Gases
The following material is from the LP Gases Handbook, pages 50 - 61,
which discusses rules regarding containers, both ASME and DOT. At the end of the page is appendix C which lists the specifics of
requalification. The LP Gases Handbook is a resource which attempts to put into plain English and clarify the rules found in NFPA 58 which
govern the storage and handling of liquified petroleum gases.
In the following paragraphs, the lines starting with numbers are the rules from NFPA 58, the text in the paragraph immediately following is
the commentary and is not part of the actual rule text.
Liquefied Petroleum Gases Handbook
Fourth Edition
Based on the 1995 edition of NFPA 58, Standard for the Storage and Handling of Liquefied Petroleum Gases
Edited by
Theodore C. Lemoff, P.E.
Senior Gases Engineer
National Fire Protection Association NFPA(r) Quincy, Massachusetts
50 Chapter 2: LP Gas Equipment and Appliances
Other sections in Chapter 2 cover items which are needed to make the container a complete system to safely contain
LP Gases:
2-3 Container Appurtenances
2-4 Piping, (including Hoses, Fittings and Valves)
2-5 Equipment
2-6 The final section covers appliances.
2-2.1.2 Refrigerated containers shall comply with Chapter 9.
Because of the inherent difference between refrigerated and pressurized storage containers, requirements for the less common
refrigerated containers are placed separately in NFPA 58, in Chapter 9. Refrigerated storage is normally used for storing a large quantity
of LP Gas (1,000,000 gal or more) as a liquid at its normal atmospheric pressure boiling point (about
40 deg F). At that temperature, the liquid can be stored at a very low pressure, usually less than 5
psi.
2-2.1.3 Containers shall be designed, fabricated, tested, and marked (or stamped) in accordance with the Regulations of the U.S.
Department of Transportation (DOT), the ASME Boiler and Pressure Vessel Code, "Rules for the Construction of Unfired Pressure Vessels,"
Section VIII, or the API-ASME Code for Unfired Pressure Vessels for Petroleum Liquids and Gases applicable at the date of manufacture; and
as follows: (See Appendices C and D.)
In the 1995 edition, this paragraph was revised (with a corresponding change to the definition of ASME Code) by removal of the restriction
that pressure vessels be constructed according to ASME Code, Section VIII, Division 1, and now permits construction to Section VIII,
Division 1 or 2. Refer to the commentary following the definition of ASME Code for more information on Division 2.
Containers that have passed their useful service life due to corrosion, mechanical damage, or lack of a nameplate must be removed
from service. As most ASME containers are the property of a propane marketer, the marketer will usually accumulate a number of containers
destined for scrap and ship them to a scrap metal dealer. The marketer is advised to take steps to
ensure that these containers are, in fact ,destroyed. The editor recently received a phone call from, and later
met with, a state's fire marshal and chief pressure vessel inspector who discovered a number of propane tanks that had recently been sold
for, and were being used in, propane service that did not meet the ASME Code requirements.
Investigation determined that the tanks had been sold to a scrap dealer and had subsequently been "repaired" by
the use of fiberglass patches, by sanding corroded areas and repainting. The tanks were sold to propane consumers who were
persuaded that they would be able to purchase propane at a lower price if they owned their own container.
To the editor's knowledge, this case is being treated as a criminal matter.
There is nothing in NFPA 58 to prevent a consumer from purchasing his or her own
LP Gas tank. When this is done, the owner is not relieved of the requirements of the standard that the container be maintained.
It is the responsibility of the propane marketer to take reasonable steps to verify that a container is fit for service before filling the
container. This applies equally to a 20-lb gas grill cylinder, a 500-gal tank at a residence, and a 30,000-gal container at an
industrial facility.
(a) Adherence to applicable ASME Code Case Interpretations and Addenda shall be considered as compliance with the ASME Code.
There has been some confusion as to the intent and application of this paragraph, particularly in regard to containers built to ASME-API
specifications U-200 and U-201, and ASME specifications U-68 and U-69 constructed to codes in existence prior to 1949.
As these containers have a very long service life, when properly maintained, many remain in
use and are sometimes relocated and reinstalled. It is the Committee's intent that use, relocation, and reinstallation of such containers be
permitted to continue provided the requirements of 1-2.5, Retroactivity, are met; 1-2.5 states that the provisions of the
current edition of NFPA 58 not be applied to "equipment.., in compliance with the provisions of this standard in effect at the time
of manufacture. " The reason for allowing these old containers to continue to be used is simply that there has been no evidence that
there are any flaws in the design and construction of these containers which become evident after over 40 years of use. At the time
these containers were built, they incorporated the then-state-of-the-art in design,
metallurgy, and fabrication techniques. While it is true that these have improved significantly over the years, there is no evidence
that these containers are less safe than when they were built, where they are properly maintained.
There are a number of nondestructive tests that can be used to determine whether the container is in compliance with the standard in
effect at the time of manufacture. These include hydrostatic testing, ultrasonic metal thickness testing, and others.
The person performing the evaluation must be familiar with the code to which the container
was constructed and the test method to be used. Each test method has advantages and disadvantages.
Hydrostatic testing, for example, will verify that a container is suitable for continued service; however,
because water is heavier than propane, it must first be determined that both the container and its foundations can support the additional
weight without causing damage. This is a real concern in larger containers.
(b) Containers fabricated to earlier editions of regulations, rules, or codes listed in 2-2.1.3 and the ICC Rules for Construction of
Unfired Pressure Vessels, prior to April 1, 1967, shall be permitted to be continued in use in accordance with 1-1.4.
2-2.1.3* Prior to April 1,1967, regulations of the U.S. Department of Transportation were promulgated by the Interstate Commerce Commission.
In Canada, the regulations of the Canadian Transport Commission apply. Available from the Canadian Transport Commission, Union Station,
Ottawa, Ontario, Canada.
Construction of containers to the API-ASME Code has not been authorized after July 1,1961.
To the editor's knowledge, all pressurized LP Gas containers in the U.S., Canada, and other countries served by marketers based in the
U.S. and Canada comply with 2-2.1.3. Many other countries that use NFPA 58 have their own container requirements.
Furthermore, a safe container can be built using other criteria, and this flexibility is
desirable in the standard.
Containers originally used for LP Gas were Interstate Commerce Commission (ICC) cylinders. DOT/ICC restricts cylinders to 1,000 lb
(454 kg) of water capacity and less. In the early days, there were some ICC specifications, such as ICC-26 and
others; but these have not been used for many years. The current basic container for reusable
service is a DOT 4BA-240 cylinder (steel construction) and a DOT 4E specification (aluminum construction).
There are also "throw-away" cylinders, such as the hand torch cylinders, which have different DOT
specifications (or old ICC specifications) currently DOT 39.
Even though the responsibilities of the U.S. Department of Transportation and the Canadian Transport Commission are restricted to
the transportation environment while much of the application of NFPA 58 is concerned with container usage and storage, there are compelling
reasons why the standard must recognize these containers. From a safety point of view, it would be extremely hazardous to require that
LP Gas be transferred from a DOT shipping container to another use or storage container on the premises of the user or storer.
Such a procedure would also be adverse from an economic standpoint. However,
the NFPA Technical Committee continuously monitors DOT and CTC standards to ensure that they are adequate for the applications
covered by NFPA 58. For example, the Committee did not permit the 4E (aluminum) cylinder for several years until its use and storage safety
had been demonstrated by tests and experience.
While all DOT/ICC/CTC containers (cylinders) are portable in the sense that they are designed to be transportable full of product, when it is
considered that such containers commonly hold from 1 lb (0.5 kg) to 420 lb (190 kg) of propane, the degree of portability varies widely.
In practice, cylinders in portable service are those that can be moved with reasonable ease by a strong individual, or those that contain up
to about 100 lb (45 kg) of LP Gas [about 200 lb (90 kg) total weight of cylinder and product].
These containers are usually filled at a location other than where they are installed or used, although it is
common to see 100-lb cylinders "permanently" installed at residential and commercial locations being filled on site.
When this is done the standard cylinder valve is replaced with a multiport valve so that the
cylinder can be refilled without dismantling the piping. Containers
larger than these usually are filled at the installed location and are considered to be in stationary
service.
A DOT/ICC cylinder is required to be marked with certain information; usually on the cylinder itself or on its neck ring
or collar. This information is especially vital in determining the suitability of the cylinder for continued service indicated by the
retest date.
The second type of container is the "bulk container," usually an unfired pressure vessel built to the ASME Code.
The original LP Gas bulk containers were riveted, but there was great difficulty in
keeping them leak-free around the rivets and at the seams. The industry then began to forge-weld containers, and in the 1930s began
to use the fusion-welded pressure vessels. At that time the ASME Code specifications were U-68 and U-69, which had a safety factor of 5 to 1
(design operating pressure to theoretical burst pressure). The normal working pressure of these containers was 200 psi (1.4 MPa).
NFPA 58 allowed the pressure relief valve setting to be 125 percent of the working pressure, or 250 psi (1.7 MPa).
This was done to ensure that there would be no pressure relief of the flammable product into the
atmosphere as a result of ambient air temperatures or solar radiation, which would create a hazard.
Prior to 1949, there were also ASME specifications U-200 and U-201, which were developed in conjunction
with the American Petroleum Institute. These were known as the API-ASME Code specifications.
Such containers,however, were restricted in use to installations such as refineries, gas processing plants, and
tank farms.
In 1949, ASME adopted the current ASME Code precept with a safety factor of 4 to 1.
At that time the requirement for the pressure relief valve setting was changed to the working pressure of a
container, which generally was 250 psi (1.7 MPa). In effect, the previous 4 to 1
safety factor and the 5 to 1 safety factor were comparable from an ultimate burst standpoint because 200 x 5 and 250 x 4 both equal
1,000. Many pre-1949, 200-psi (1.4 MPa) ASME tanks are still in service.
With the exception of those used in vehicular systems, ASME Code containers are usually found in stationary installations.
At times, there are ASME Code Case Interpretations and Addenda to the base code; they are also applicable to ASME containers.
See Appendices C and D for further description of DOT/CTC and ASME Code containers.
2-2.1 .4 Containers complying with 2-2.1.3 shall be permitted to be reused, reinstalled, or continued in use as follows:
(a) A container shall not be filled if it is not suitable for continued service.
(b) DOT cylinders shall not be refilled, continued in service, or transported unless they are properly qualified or requalified for
LP Gas service in accordance with DOT regulations.
(c) Containers that have been involved in a fire and show no distortion shall be requalified for continued service before being
used or reinstalled as follows:
1. DOT containers shall be requalified by a manufacturer of the type of cylinder to be requalified or by a repair facility approved by DOT.
Exception: DOT4E specification (aluminum) cyllnders shall be permanently removed from service.
2. ASME or API-ASME containers shall be retested, using the hydrostatic test procedure applicable at the time of original
fabrication.
3. All appurtenances shall be replaced.
Maintenance of the container is extremely important. Containers may be subjected to conditions at the point of installation that can create
corrosion. In addition, the handling of cylinders can result in cuts, gouges, and dents, which can weaken them and defeat protective
coatings (paint). It is the responsibility of the container's owner to see that it is properly maintained and requalified, that the container
is repaired if such can be done in a safe manner.
Corrosion is a major factor in the failure of DOT cylinders, especially where the wearing ring is attached to the bottom of the
cylinder. This area is especially vulnerable to the elements, and there will be cycles of drying and wetting that accelerate corrosion.
The cylinder has to be upended in order for this area to be checked, and it has to be done very thoroughly or small areas of heavy
corrosion can be missed. Many times there will be deep corrosion under scale on the surface and the deep corrosive spot will not be observed.
Then when the cylinder is put back into use, it can fail at such a point. All scale, rust, and corrosion must be thoroughly removed at
the time of retest or requalification; this is especially the case with the area where the wearing ring is attached to the bottom of the
container. After the rusted or corroded area is properly cleaned, the cylinder surface should be well coated with a protective coating to
prevent future rust and corrosion.
When a cylinder is removed from service and discarded, it should be cut up so that it cannot be repaired by a junkyard or others and put
back into pressure service. Care should be used when it is cut up to ensure that it has been properly purged of all product, including
vapors. Compressed Gas Association Pamphlet C-2, Recommendations for the Disposition of Unserviceable Compressed Gas Cylinders, is useful
in these circumstances.
The retesting and requalification of DOT and CTC cylinders are best done by a qualified test organization or, if not, then by a thoroughly
qualified and trained individual.
If a cylinder has been subjected to fire, the metal shell (usually steel or aluminum) can be weakened and can be requalified only by a
properly qualified repair facility authorized by DOT or CTC. When an ASME Code container has been subjected to fire, it must be retested
using the hydrostatic test procedure applicable at the time it was originally fabricated, because the fire heat can alter the properties
of the steel and result in reduction of its ability to contain pressure.
In the 1995 edition, (c) was added to require replacement of container appurtenances where a container was exposed to fire.
The Committee was advised that there were no procedures for requalification of container
appurtenances where the container was exposed to fire, and agreed that replacement was needed.
2-2.1.5 ASME paragraph U-68 or U-69 containers shall be permitted to be continued in use, installed, reinstalled, or placed back into
service. Installation of containers shall be in accordance with all provisions listed in this standard.
(See Section 2-2, Table 2-2.2.2, Table 2-3.2.3, and Appendix D.)
This requirement was added in the 1995 edition to clearly and specifically state that these containers can be continued in service
and reinstalled. See commentary following 2-2.1.3(a).
2-2.1.6 Containers showing serious denting, bulging, gouging, or excessive corrosion shall be removed from service.
This includes ASME and API/ASME containers as subject to inspection. Prior to the 1986 edition, only DOT/CTC containers were addressed in
this context. ASME containers are being used more widely as bulk distribution has replaced cylinder exchange as the preferred method of
distributing propane. ASME containers are also used in vehicular applications, where they are more subject to physical damage and
corrosion than stationary containers.
2-2.1.7 Repair or alteration of containers shall comply with the regulations, rules, or code under which the container was fabricated.
Other welding is permitted only on saddle plates, lugs, or brackets attached to the container by the container manufacturer.
The heat of welding directly to the container can affect the strength of the metal and change its characteristics so that it does not meet
the code. Such heating can set up localized stressing, which can affect materially the strength of the metal.
Welders holding certification for repair of pressure vessels can perform welding
operations in a manner that will not weaken the container. For repairs to pressure vessels, an ASME "R" stamp is required.
2-2.1.8 Containers for general use shall not have individual water capacities greater than 120,000 gal (454 in3).
Containers in dispensing stations shall have an aggregate water capacity not greater
than 30,000 gal (114 in3). This capacity restriction shall not apply to LP
Gas bulk plants, industrial plants, or industrial applications.
This limits the size of containers that may be installed for general use and in service stations.
The 30,000-gal (114-in3) limit on total storage in dispensing stations intended to provide a limit on storage
at locations where only portable cylinders are filled. The term "general use," which is not defined in the standard, is intended to
mean installations where LP Gas is not the primary or sole product or raw material used.
Thus an LP Gas bulk plant where most employees can be expected to be aware of the proper procedures for handling
LP Gas is not general use, while a container used as an alternate fuel supply at a manufacturing plant whose product is not related to
LP Gas is general use.
1995 LIQUEFIED PETROLEUM GASES HANDBOOK
LIQUEFIED PETROLEUM GASES HANDBOOK 1995
432 Appendix C: DOT (ICC) Cylinder Specification Containers
C-3 Requalification, Retesting, and Repair of DOT Cylinder Specification Containers.
C3.1 Application.
C3.1 .1 This section outlines the requalification, retesting, and repair requirements for DOT cylinder specification containers but
should be used only as a guide. For official information, the applicable DOT regulations should be consulted.
C3.2 Requalification (Including retesting) of DOT Cylinders.
C3.2.1 DOT rules prohibit DOT cylinders from being refilled, continued in service, or transported
unless they are properly qualified or requalified for LP Gas service in accordance with DOT
regulations.
C3.2.2 DOT rules require a careful examination of every container each time it is to be filled, and it must be rejected if there is evidence
of exposure to fire, bad gouges or dents, seriously corroded areas, leaks, or other conditions indicating possible weaknesses that might
render it unfit for service. The following disposition is to be made of rejected cylinders:
(a) Containers subjected to fire are required to be requalified, reconditioned, or repaired in accordance with 0-3.3.1, or permanently
removed from service except that DOT 4E (aluminum) cylinders must be permanently removed from service.
(b) Containers showing serious physical damage, leaks, or with a reduction in the marked tare weight of 5 percent or more are required
to be retested in accordance with 0-3.2.4(a) or (b) and, if necessary, repaired in accordance with 0-3.3.1.
C3.2.3 All containers, including those apparently undamaged, are required to be periodically requalified for continued service.
The first requalification for a new cylinder is required within 12 years after the date of manufacture.
Subsequent requalifications are required within the periods specified under the requalification method
used.
C3.2.4 DOT regulations permit three alternative methods of requalification for most commonly used
LP Gas specification containers (see DOT regulations for permissible requalification methods for
specific cylinder specifications). Two use hydrostatic testing, and the third uses a carefully made, and duly recorded, visual examination
by a competent person. In the case of the two hydrostatic test methods, only test results are recorded, but a careful visual
examination of each container is also required. DOT regulations cite in detail the data to be recorded for the hydrostatic test
methods, the observations to be made during the recorded visual examination method, and the marking of containers to indicate the requalification
date and the method used. The three methods are outlined as follows:
(a) The water jacket-type hydrostatic test is permitted to be used to requalify containers for 12 years before the next requalification is
due. A pressure of twice the marked service pressure is applied, using a water jacket (or the equivalent) so that the total expansion of the
container during the application of the test pressure can be observed and recorded for comparison with the permanent expansion of the
container after depressurization. The following disposition is made of containers tested in this manner:
1. Containers that pass the retest, and the visual examination required with it (see C-3.2.4), are marked with the date and year of
the test (Example: '6-90," indicating requalification by the water
jacket test method in June 1990) and are permitted to be placed back in service.
2. Containers that leak, or for which the permanent expansion exceeds 10 percent of the total expansion (12 percent for Specification 4E
aluminum cylinders), must be rejected. If rejected for leakage, containers are permitted to be repaired in accordance with 0-3.3.1.
(b) The simple hydrostatic test is permitted to be used to requalify containers for seven years before the next requalification is due.
A pressure of twice the marked service pressure is applied, but no provision is made for measuring total and permanent expansion during
the test outlined in 0-3.2.4(a) above. The container is carefully observed while under the test pressure for leaks, undue swelling, or
bulging indicating weaknesses. The following disposition is made of containers tested in this
matter:
1. Containers that pass the test, and the visual examination required with it (see C-3-2.4), are marked with the date and year of the retest
followed by an "S" (Example: "8-91S, indicating requalification by the simple hydrostatic test method in August 1991) and are permitted to be
placed back in service.
2. Containers developing leaks or showing undue swelling or bulging must be rejected.
If rejected for leaks, containers are permitted to be repaired in accordance with 0-3.3.1.
(c) The recorded visual examination is permitted to be used to requalify containers for five years before the next qualification is
due provided the container has been used exclusively for LP Gas
commercially free of corroding components. Inspection is to be made by a competent person, using as a guide the Compressed Gas Association
Standard for Visual Inspection of Steel Compressed Gas Cylinders (OGA Pamphlet 0-6), and recording the inspection results as required by DOT
regulations. [Note: Reference to NPGA Safety Bulletin, Recommended Procedures for Visual Inspection and Requalification of DOT (ICC)
Cylinders in LP Gas Service, is also recommended. The following disposition is to be made of containers inspected in this manner:
The Compressed Gas Association's Standard for Visual Inspection of Steel Compressed Gas Cylinders, Pamphlet C-6, is a guide that can be
used to requalify cylinders as required by DOT regulations. It contains examples of various types of pitting, corrosion, and failed
cylinders and is very useful for persons not completely familiar with the subject.
The National Propane Gas Association publishes two safety pamphlets that provide useful information on requalifying cylinders: NPGA 117,
Visual Cylinder Inspection, which is a guide for visual inspection of cylinders prior to refilling, and NPGA 118, Recommended Procedures for
Visual Inspection and Requalification of DOT (ICC) Cylinders in LP Gas Service, which provides the
complete set of DOT requirements along with illustrations demonstrating the use of the gauges needed to
complete the inspection and a "visual inspection report form." (See Figure C. 1.)
1. Containers that pass the visual examination are marked with the date and year of the examination followed by an "E' (Example: "7-90E,
indicating requalification by the recorded visual examination method in July 1990) and are permitted to be placed back in service.
2. Containers that leak, show serious denting or gouging, or excessive corrosion must either be scrapped or repaired in accordance with
0-3.3.1.
C3.3 Repair of DOT Cylinder Specification Containers.
C3.3.1 Repair of DOT cylinders is required to be performed by a manufacturer of the type of cylinder to be repaired or by a repair
facility authorized by DOT.
Repairs normally made are for fire damage, leaks, denting, gouges, and for broken or detached valve protecting collars or foot rings.
1995 LIQUEFIED PETROLEUM GASES HANDBOOK