Gas Connection Adapters - Should We Help Our Customers Kill Themselves?

The reasons usually offered for wanting an adapter follow this general line of thinking:

• The supplier was supposed to ship the cylinder with a specified connection, but somehow the cylinder came with the wrong connection. And, of course, it took so long to get the cylinder in the first place that the customer could not wait for another one with the proper connection.
• My customer is going to use this gas for only this one experiment, and he does not want to spend the money for another pressure regulator.

The role of CGA
The Compressed Gas Association has developed a system of cylinder valve outlet connections that minimize the possibility that cylinders of incompatible gases will be connected to a user’s gas system. This system of cylinder connections was the result of efforts made by members of the Compressed Gas Manufacturers’ Association, Inc. immediately after World War I. In January 1949, the Compressed Gas Manufacturers Association changed its name to the Compressed Gas Association. Shortly thereafter, the result of 30 years of effort by the CGA and various governmental bodies was presented to the American Standards Association and the Canadian Standards Association. These two bodies accepted the CGA valve outlet standards within the year. Since initial acceptance, the standards have been changed to accommodate new gases, remove obsolete connections, and recognize new technologies.

Although the main purpose of the CGA valve outlet standard is to prevent interconnection with non-compatible gases, one should not rely on the valve outlet connection as the sole means of identifying the contents of any compressed gas cylinder. The primary means for identifying the contents of any cylinder of compressed gas should be the label attached to the cylinder, which displays the chemical or commercially accepted name of the material contained within.

The use of adapters as a convenient shortcut to circumvent the CGA system is as old as the system itself. This use undermines the spirit of this system and often presents a potential workplace hazard. Unfortunately, the convenient use of adapters has a history of disaster. Incident reports are filled with graphic descriptions that indicate the cause of the accident. Very often, the culprit is identified as the improper use of an adapter. Often the accidents reported result in serious injury, property damage, and/or death. When the economics are compared, the savings realized by the misapplication of an adapter is minuscule when considering the cost difference between a new regulator and an adapter.

Also, the cost of a lawsuit to the supplier of the adapter, as well as the increased insurance premiums, would be incredible compared to the few dollars profit that would be made on the sale of an adapter. Although a few adapters are arguably “safe” because the gases assigned to these connections do not react with one another or present no another hazard, there are many combinations that should be avoided.

Table 1 lists a number of adapters and the main potential hazard of each. Each of the examples listed has been involved in a failure resulting from misapplication. Many are the result of a request made by distributor sales personnel who did not recognize the potential hazard involved with the adapter in question. Others can be attributed to instances in which the components were routinely sold by equipment suppliers. For purposes of clarity, the adapters are described by listing the connections relative to the direction of flow from the cylinder valve. One example: an adapter that would be used to connect a CGA 350 cylinder valve to an oxygen pressure regulator having a CGA 540 would be listed as CGA350F x CGA 540M. The list is far from complete.

Often the argument is made that a particular adapter is supplied because the customer is considered to be knowledgable. In the case of the CGA660F x CGA 705M example, the supplier was assured that the only gas on the customer’s premises was ammonia. While this may have been true at the time of the sale, consideration must be given to future possibilities. The customer who “knows what he is doing” could retire, be promoted to another department, or move to another job, leaving the adapter behind. The end-user company could introduce a new process that uses chlorine. Someone from another department that uses chlorine could be looking for a solution to his connection problem and “borrow” the adapter. As long as the adapter exists, the potential hazard remains a threat.

In university settings, the potential hazard is even greater. The users are often not experienced in the characteristics of the gases they are using, or the equipment required, or the potential danger of connection interchange. Additionally, the personnel involved are for the most part graduate students in laboratories. They tend to use equipment that has been left behind by previous tenants in an attempt to stretch their research grants. The new resident of the lab may easily misuse an adapter used “properly” by the previous student.

Some customers swear that they are only going to use the adapter on this one cylinder and then destroy it or dispose of it so that it cannot be used in the future. There can be little assurance that this would really happen. Sales personnel cannot fill the role of policemen.

Do you trust your customers sufficiently to be willing to accept the liability involved in providing them with an adapter instead of the proper equipment to use with the gas that you have provided?

Summary
The best and safest practice is to use specific equipment with each gas and not to interchange at all.

There are a few exceptions:

• If purity is not an issue
• Some equipment could be used on similar gases;
  i.e., a hydrogen regulator could be used with methane or ethylene and then hydrogen again. Or, a regulator used on helium could be used with nitrogen or argon.

Other than the foregoing class of gases, the chances of a serious accident increase dramatically. Above all, equipment that is to be used on oxygen should be used for oxygen only. It should never have been converted from some other service unless it has been totally disassembled and all components have been cleaned for oxygen service.

The CGA connection system is not perfect. There are many opportunities within the system to connect incorrect equipment to an incompatible cylinder of gas. But the use of adapters exponentially increases the chance of an accident. It is the responsibility of the supplier, not only to sell safe products, but also to educate end-users in the safe use of these products. Frank Scornavacca is president of SGD, Inc., Emerson, N.J.
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