High Pressure Aerosol Containers:

A Design Systems Perspective

Yurij F. Wowczuk

General Manager

ITW Sexton

A special thanks to a mentor and

colleague, Dr. Montfort A. Johnsen

History of high pressure aerosol

containers

• The hazardous aspects of bursting aerosol cans has been a topic of

concern since about 1942 – even before there was an aerosol

industry.

• The first commercial introduction of a pressurized container was

used to package insecticides for the United States Army

• A number of geometries were

soon developed, but all had a

minimum burst resistance of

1500 psi-g. In practice they

generally held pressures into

the 1800 to 2000 psi-g range.

Obviously they were heavy

and costly. The wall thickness

was 0.090”.

• The United States ICC (Interstate Commerce Commission –

forerunner to the US DOT) approved lightweight “pressure cans” in

1945. The term “Aerosol” was still not in widespread use.

• Initial packaging parameter was a maximum of 25 psig @ 70

degrees F. Since this was not high enough for fine particles needed

for insecticides, the ICC increased the temperature threshold to 130

degrees F.

• The first pressure relief devices were introduced in the 1950’s. Most

were unsuccessful or failed to achieve repeatable results in the

waterbath or in the field:

– Fusible alloys joined to mounting cup orifices

– Pressure Plugs

– CAI (Cornell Aeronautical Institute) Spike

– Beard Clip

– Steritip/Saftipac

• The first successful

pressure relief device was

American Can Company’s

RVR (Rim Vent Release)

cans

Problems with pressure relief devices in three piece containers as well as one

piece aerosol Limitations of Three Piece Containers consisting of pressure relief

devices:

» cost

» reliability

» appearance

» robustness

» performance

Aluminum aerosols are inherently limited with regards to applicable pressure relief devices given their one piece construction and impact

extrusion processes.

2P and 2Q

• DOT regulates the manufacturing and testing specifications for

containers used for the transportation of hazardous materials in

commerce.

• Specifications are found in in the Hazardous Materials Regulations

of the Department of Transportation Bureau of Explosives 6000

Book part 178.

2P • A DOT 2P container is used if the internal pressure is from 140

psig (9.7Bar) to 160 psig (11Bar) at 130° F (54.4° C).

• Destruction test must not burst below 240 psig. [16.5Bar] (or 1.5

times the maximum pressure of the contents at 130 ° F).

• Test one can out of each lot of 25,000 containers although many

manufacturers increase their testing frequency.

• Minimum wall thickness for any container shall be 0.007 inch.

• Container print must be marked to show DOT-2P and name or

symbol of person or company making the mark.

2Q • A DOT 2Q container is used if the pressure is from 161 psig

(11.1Bar) to 180 psig (12.4Bar) at 130° F (54.4° C).

• Destruction test must not burst below 270 psig. [18.6Bar] (or 1.5

times the maximum pressure of the contents at 130 ° F).

• Test one can out of each lot of 25,000 containers although many

manufacturers increase their testing frequency.

• Minimum wall thickness for any container shall be 0.008 inch.

• Container print must be marked to show DOT-2Q and name or

symbol of person or company making the mark.

In Europe Typically high pressure cans are specified as:

• 12 bar (174 psig) cans or

• 15 bar (218 psig) cans or

• 18 bar (261 psig) cans

• For containers filled at a pressure of less than 6,7 Bars (97 psig)

at 50ºC (122ºF), the test pressure must be equal to at least

10 (145 psig) Bars.

• (b) For containers filled at a pressure equal to or greater than 6,7

Bars at 50ºC, the test pressure must be 50% higher than the

internal pressure at 50ºC.

• Important to understand EU and US as issue of harmonization is

becoming increasingly relevant and important.

Dot Special Permits

• Special permit containers must be plainly and durably marked DOT-

SP followed by the special permit number assigned.

• In addition to the manufacturer’s mark other DOT required

information may be required.

• Special permits are granted by the DOT for special products or

pressures that exceed the specifications of 2P, 2Q and DOT-39.

• Special permits may also be granted for product handlers (fillers).

Example - Sexton Special Permits

• SP-9393 a DOT-39 exemption for Refrigerant R-22

• SP-10232 a 2Q exemption for HFC 134a and other non-flammable

refrigerant gases

• SP-10590 a 2P exemption for flammable low pressure hydrocarbon

gases

• SP-11917 a DOT-39 exemption for flammable high pressure

propane gas

• SP-12187 a DOT-39 exemption for higher pressure R-404a and

other refrigerant blends

Designs and Safety Considerations

1. Rim Vent Release (RVR)

2. PRD (Pressure Relief Device) patented by Sexton

Recent developments have compromised the unilateral position of pressure relief

devices: • Decision by the EU to allow the packaging of HFC-134a in 18 bar

containers

• FEA’s (Federation of European Aerosol Associations) insistence on global code harmonization

• DOT’s decisions to allow plastic aerosol use for packaging contents over 4 oz. and approval of an 18-bar can for the interstate transit of HFC-134a.

– Both decisions have been met unfavorably in the marketplace

• Safety concerns

• Volatility of coatings

• Valve crimp problems

• Restriction of use (i.e., DIY market)

Safety Advantages of Pressure Relief

Devices

• Any field failures must be reported to the appropriate government

agency. Such failures may – and likely will, given severity – lead to

the revocation of special permits and/or related provisions.

• In recent times, there have been no failures associated with

aerosol cans for refrigerant gas fitted with a pressure relief device.

This is not the case for an 18 bar can or aluminum.

Safety Advantages of Pressure Relief

Devices

• “18 bar” cans must withstand an internal pressure of “21.6 bar”

(312 psi-g.) without bursting. HFC 134a at 164 degrees F exceeds

“21.6 bar”. As such, their performance design parameters are

borderline and will result in a much more volatile and dangerous

burst event than a can fitted with a PRD.

• At such a marginal performance factor, the use of a waterbath gives

no assurance that an 18 bar product would safely perform in

situations of misuse, over pressurization, or after improper filling (ie

headspace management).

Safety Advantages of Pressure Relief

Devices

• Containers fitted with pressure relief devices remain intact when

over pressurized and which reduces the likelihood of serious injury.

• Containers fitted with PRDs can withstand 27 bar or more before

the pressure relief device opens.

Conclusion:

History has shown that there is a need to supply the aerosol industry

with a safe reliable pressure relief device for low and high pressure

gases. I’m proud to say the RVR for lower pressure and the PRD

for higher pressure gases fulfill that need.

MUCHAS

GRACIAS