Illinois Fertilizer & Chemical Association
Supply · Service · Stewardship

Two Back Checks Required When Pulling Dual Nurse Tanks

The Illinois Department of Agriculture Bureau of Ag Product Inspection has notified the IFCA office regarding ag retailers pulling two nurse tanks behind a tool-bar may require two back check valves.  Nurse tanks pulled in tandem or side by side and connected to two separate heat exchangers on the tool-bar are required to have two back check valves installed prior to the equalizing line on the toolbar.  Generally, the heat exchangers on the tool-bar are connected with an equalizing line to equalize pressure between both anhydrous nurse tanks feeding the tool-bar.  The problem with an equalizing line is it will act as a circulation line in the event one of the anhydrous ammonia hoses becomes pinched, cut or ruptures.  If connected to two heat exchangers, the excess flow valve on the liquid withdrawal valve will not activate because the leak form the hose does not exceed the gallon per minute on the liquid withdraw valve.  A hose rupture or leak would cause both tanks to empty with only one back check valve in place. 
 
IDA is instructing facilities to install two back check valves prior to the equalizing line on the tool-bar if two separate tanks are connected to two separate heat exchangers.  The back check valves will prevent both tanks from emptying.  Back check valves would not be required on a tool-bar if there is only one quick coupler or if both heat exchangers are not connected by an equalizing line.  Facilites that plumb two side by side anhydrous ammonia tanks into one line must install back check valves on the plumbing of the two ammonia tanks into one line.  If you have any questions, please contact Kevin at the IFCA office.