There is a lively interest in how best to measure and regulate ammonia levels in various processes. Sierra has the right solution to this query, but an important caveat is that some precautions must be taken beforehand.
The biggest obstacle to using a flow meter in this situation is the liquefaction of ammonia during the flow, which damages the instrument measuring the flow. The Sierra SmartTrak 100, however, regulates ammonia mass flow while ensuring that all its materials can exist in stable form with anhydrous ammonia.
Importance of Preventing Ammonia Liquefaction
Since ammonia gas becomes deadly to equipment once it liquefies, the most important precaution to be taken in its handling is to keep it dry and warm to prevent its liquefaction and avoid the formation of corrosive gaseous products. While ammonia in a tank is called dry under technical definition, it is possible for such ammonia to mix with the condensate from vapor which has liquefied at key plumbing points. This mixture will then give rise to gaseous products which can corrode 316 stainless steel and Neoprene seals.
Steps in Preventing Vapor Condensation
- Maintain temperatures at plumbing points above the dew point, by using heat tape at appropriate locations such as the ammonia gas entry points into meters and controllers, to keep the gas temperature at 120 °F (or at most 122 °F). The SmartTrak keeps the maximum temperature within the optimum range by allowing a maximum specification of only 122 °F.
- The body of the flow meter should be kept warm as well, to keep vapor from condensing. The SmartTrak has a 316 stainless steel which is kept at 115 °F.
- The equipment design should contain as few valves as feasible as these are the points at which the pressure drops abruptly or the flow velocity increases, both of these being key factors in condensation.
- All plumbing should be kept leak-proof by regular monitoring.
- The processes should be run at constant low pressures because ammonia is least likely to liquefy under such conditions.
- Regulators should be well-maintained and free of gas leaks to keep the pressure at the right level.
- All mass flow controllers and meters should be fixed at the highest points possible because if they are installed at low positions, moisture accumulation is probable.
Provided care is taken on these aspects, the flow meters and controllers from Sierra are warranted to function without complaint for years.
This information has been sourced, reviewed and adapted from materials provided by Sierra Instruments.
For more information on this source, please visit Sierra Instruments.