Sensing unit for detecting refrigerant leak sealant additive
A device for determining the presence or absence of refrigerant leak sealant within the refrigerant charge of air conditioning systems or stores is described. A sensing unit having a seal-forming surface is wetted and placed in fluid communication with a refrigerant access port of the air conditioning system. A depressor opens the refrigerant port and refrigerant begins to flow through the sensing unit. If any leak sealant is present in the refrigerant charge, a sealant plug begins to form on the seal-forming surface and reduces the flow rate of the refrigerant through the sensing unit, thereby indicating the presence of the sealant. Refrigerant charges that do not contain a leak sealant will flow through the sensing unit at a substantially constant rate, indicating the absence of sealant.
1 . A sensing unit for use with a device for detecting the presence or absence of a leak sealant additive in an air conditioning charge, the sensing unit comprising:
an inlet for admitting refrigerant, an outlet for exhausting the refrigerant;
a passage between the inlet and the outlet; and
a seal-forming surface within the passage on which leak sealant additive can form a sealant plug to at least partially restrict refrigerant flow from the inlet to the outlet.
2 . The sensing unit of claim 1 wherein the seal-forming surface comprises a porous insert between the inlet and the outlet.
3 . The sensing unit of claim 2 wherein the porous insert comprises sintered metal.
4 . The sensing unit of claim 1 wherein the passage comprises a machined orifice and wherein the seal-forming surface comprises a surface adjacent the machined orifice.
5 . The sensing unit of claim 1 wherein the seal-forming surface defines a flow restrictor that allows less than five percent of the refrigerant charge to pass in three minutes.
6 . The sensing unit of claim 1 wherein the seal-forming surface defines a flow restrictor that limits refrigerant flow to between about 100 cm 3 /min and about 1000 cm 3 /min from a refrigerant source at 60 to 200 psig.