As a manufacturer of hammer union by API flange and/or hub adapters, WOODCO USA strongly supports the creation of an API Standard Specification for Figure Number designated hammer unions. Presently operators and users of Figure Number designated threaded, butt weld and integral, wing nut hammer unions have “Mostly Learned” that they can connect any male Figure Number half union to any female Figure Number half union, as long as both halves have the same Figure Number and size designation.

Reported incidents resulting from accidentally connecting incompatible 2″ Figure Number 1502 male half unions, to 2″ Figure Number 602/1002 Female Half  Unions, which engage improperly when threaded together and fail explosively when placed under pressure, prompted the creation of API Recommended Practice 7HU1, 1st Edition, May, 2009, specifying a modification to the dimensions of 2″ Figure Number 602/1002 Female Half Unions, while retaining interchangeability with all such Unions in the field.

To purchase a copy of Recommended Practice 7HU1, Click Here.

A new API Task Group 5 Subgroup, had its first meeting on December, 13, 2011, and a new effort began to create an API Standard for Figure Number designated hammer union connectors.

Investigation has revealed that over time manufacturers of Figure Number hammer unions have created a “Defacto Standard” for these unions, that will allow them to reliably join, test, and function, but with small dimensional differences.

Based upon the number of these unions in the field, and the fact that no single manufacturer can satisfy the demand for the quantity or configurations of equipment with these connectors, a strong need for an API Standard exists.

If your company owns or uses Figure Number designated hammer union connected equipment, please contact the manufacturer identified on the equipment and urge them to participate in, or support, the current API effort to standardize these unions. The standardization effort does not intend to obsolete, or make unusable, any current Figure Number designated hammer unions, but rather to bring the current compatible designs into future uniformity of dimensions and materials.

Buyers of Figure Number Union replacement seals should use caution when buying generic seals from suppliers that do not manufacture Figure Number Unions. Union manufacturers have specified exact dimensions and elastomer compounds and have conducted necessary tests to confirm a reliable seal. Generic seal suppliers are possibly making untested copies and may have no method to assure proper performance in the field.

Should you want to contact API directly, to comment on or make suggestions, concerning the task group currently working on this project, send an email to:

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