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THE ECONOMICS OF ODORIZATION

Utilities must supply natural gas which is odorized within certain limits. Too little odorization may make the presence of the fuel undetectable to some, thereby creating a potentially dangerous situation. Too much of same may not be
particularly hazardous [except by offending olfactory sensors], but it can be costly to the utilities. The excess odorant will make otherwise imperceptible leaks very perceptible. It will propagate within a closed environment [such as a house]. The result is a veritable swarm of technicians following the trail of an overodorized pipeline through user neighborhoods. They respond to customer complaints of gas leaks which are really of no consequence. On top of that, they have expended far more odorant than is necessary and odorant is not cheap.

Many gas utilities opt to substantially overodorize to eliminate potential liabilities. Typical installations utilize metering pumps which inject odorant into natural gas pipelines. At best, on their own, these devices are capable of accuracies on the order of ±10% [this is assuming that they are working properly and that the odorant supply hasn't run dry].

Control of this typical system is effected by a technician, on site. The technician periodically checks and adjusts the metering pump pneumatic timer so that the pump output corresponds to the gas flow indicator reading. In parts of the country that are subject to rapid weather changes, it is not uncommon for such a technician to get a call in the middle of the night to rush to the site to make an adjustment for a sudden cold snap. The addition of a couple of off-the-shelf components, would allow these technicians to sleep better. They would normally only be required to perform routine system maintenance.

Recommended system:
A Microflowmeter (as manufactured by DEA Engineering Company - see www.deaengineering.com) is used to provide positive feedback to the control system that odorant is, indeed, being pumped to the pipeline. This overcomes the previously mentioned potential failures of improper metering pump function and depletion of the odorant supply.

A solenoid valve replaces the pneumatic timer which is normally part of the injection pump.

A computer (such as a PLC which is available from many Industrial Control manufacturers) not only controls the system, but can trigger alarms, transmit information and even shut down the pipeline as warranted.

These improvements typically have a payback on the order of less than a year if a utility reduced its odorant injection to minimum levels. Some additional margin would, no doubt, be judicious. Perhaps of far greater value than whatever savings are achieved, is the comfort such a system provides in this litigious age.

The net result is more efficient operation, significant reduction in odorant injection costs and a substantial increase in reliability and safety.

Odorant Injection Application