Hammer union figure numbers explained
A hammer union's figure number is its rating and its thread in one. Here is the chart, the sour gas versions, and the mismatch that has hurt people on rigs.
A hammer union's figure number identifies its design: thread, seal and cold working pressure. FIG 602 is rated 6,000 psi, FIG 1002 10,000 psi, FIG 1502 15,000 psi and FIG 2002 20,000 psi, with lower-pressure figures such as 100, 200, 206 and 400 for 1,000 to 4,000 psi lines. Sour gas versions carry lower ratings, for example 10,000 psi for FIG 1502, and FIG 2202 is a 15,000 psi sour gas union. Only the male and female halves of the same figure may be connected.
Figure chart
| Figure | Standard service | Sour gas service | Typical use |
|---|---|---|---|
| FIG 100 | 1,000 psi | - | Low-pressure water and air lines |
| FIG 200 | 2,000 psi | - | Low-pressure lines and tank connections |
| FIG 206 | 2,000 psi | - | Low-pressure lines |
| FIG 400 | 4,000 psi | - | Medium-pressure lines |
| FIG 602 | 6,000 psi | - | Mud, cement and production lines |
| FIG 1002 | 10,000 psi | 7,500 psi | Cementing, well service and test lines |
| FIG 1502 | 15,000 psi | 10,000 psi | Frac, flowback, cementing and well test iron |
| FIG 1505 | 15,000 psi | - | High-pressure plug and check valves, swivels |
| FIG 2002 | 20,000 psi | - | Very high-pressure well service |
| FIG 2202 | - | 15,000 psi | High-pressure sour gas service |
Ratings as published by union makers: TechnipFMC for its Weco figures 602 to 2202, Kuriyama for figures 100, 206 and 400. Confirm against the maker's data for the exact part.
How to read a figure number
For the high-pressure figures, the leading digits follow the rating in thousands of psi: 602, 1002, 1502 and 2002 are 6,000, 10,000, 15,000 and 20,000 psi unions. The pattern breaks at both ends of the chart. FIG 206 is a 2,000 psi union, and FIG 2202 is a 15,000 psi union for sour gas. Treat the figure as a name, and take the rating from the maker's data and the marking on the part.
Sour gas versions
Unions for hydrogen sulfide service are made from material heat treated to sour-service hardness limits and marked as sour gas parts. Because the hardness cap lowers the strength available, the same figure carries a lower rating: 7,500 psi for FIG 1002 and 10,000 psi for FIG 1502. For 15,000 psi in sour gas, makers offer FIG 2202. The hardness limits come from NACE MR0175 / ISO 15156-2.
Never mix figures
Some unions of the same nominal size and different figures will thread together. The joint looks made up, but the threads and seal do not match, and it can fail at a fraction of either rating. The International Association of Drilling Contractors has issued several safety alerts on this. In one incident it describes, a 2 in FIG 1502 male sub was made up to a FIG 602 female half; during a surface casing test the union stripped out at about 1,300 psi and blew off, seriously injuring a worker.
- Check the stamped figure number and rating on both halves before every make-up.
- Keep different figures of the same size apart in the yard and on the truck.
- Do not rely on paint color; it varies by maker and wears off.
- Retire parts whose marking can no longer be read.
Integral fittings
Unions in every figure, with threaded, butt weld or hose ends, are on the hammer unions page, and crossovers between figures on union crossovers and bull plugs. Terms such as CWP, male and female sub and crossover are defined in the glossary. On an integral fitting, the union ends are machined from the fitting's own forged body instead of being welded on. The figure rules are the same: the fitting is made, rated and marked for one figure and one service.
Frequently asked questions
Do the first digits of the figure give the pressure?
For most high-pressure figures they do: FIG 602 is 6,000 psi, 1002 is 10,000, 1502 is 15,000 and 2002 is 20,000 psi. It is not a safe rule. FIG 206 is a 2,000 psi union, and FIG 2202 is a 15,000 psi sour gas union, not 22,000 psi. Read the rating from the maker's data and the marking, never from the number alone.
Can two unions of the same size but different figures be connected?
Some pairs can be threaded together, and that is exactly the danger: the joint looks made up but cannot hold pressure. Only connect a male and female half of the same figure.
Do paint colors show the pressure rating?
Some makers color code by rating; TechnipFMC, for example, paints its 15,000 psi swivel joints red and its sour gas swivels olive green. Colors vary between makers and wear off in service, so check the stamped figure and rating on both halves instead.