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 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.

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

To see a free example of the solution offered by Recommended Practice 7HU1, Click Here.

The task group activity to create Recommended Practice 7HU1 resulted in questions about the safety and interchangeability of all sizes and pressures of Figure Number designated hammer unions for 6,000 psi and higher working pressures.

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 and not-so-small dimensional differences. Manufacturers cannot explain these differences to the satisfaction of one another, or other interested parties. This has resulted in some manufacturers issuing various warnings that include a caution not to attempt joining similarly marked and rated Figure Number hammer unions together unless made by the same manufacturer.

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.

You can contact any of the hammer union manufacturers by searching the internet using their company name to find their website and then click on their Contact link.

Tell them: 

In the interest of safety and productivity, we urge your company to participate in the current API effort to standardize the identification designation, material, and dimensions of Figure Number designated hammer unions.

Please add your company name and your personal contact information.

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: standards@api.org