Union Type Holders

The union type holder provides flexibility, ease of installation, and high-pressure ratings in tight piping configurations. The union type holder is available only for pipe sizes 2″ (50 mm) and smaller. These holders are designed to be used with either Standard or Composite (LL) Rupture Discs.

Rupture discs for use in union type holders are generally shipped with a detached tag to be affixed to the completed assembly after the rupture disc is installed. When ordering your rupture discs, please let us know if you plan to install them in a union type holder and if you require the standard configuration or a permanently attached flow tag.

Size, pressure rating, and flow direction specifications are laser-marked on the assembly.

Available sizes, ratings, and bores: See Table 12, Union Holder Assembly Number and Connections and Table 13, Union Holder Specifications.
Contact the factory for applications outside this range.
Any combination of welded or threaded connections is available.

Seating configuration: 30˚ seat
Ideal for use with both standard and composite rupture discs.

Available materials: Carbon steel, 316 SS
Other materials available on request.

Available sizes: 1/2″ (hex only), 1″, 1½”, 2″

Refer to Table 4, Minimum/Maximum Burst Pressures for Standard Rupture Discs at 72˚ F (22˚ C) and Table 5, Minimum/Maximum Burst Pressures for Preformed Composite Rupture Discs at 72˚ F (22˚ C) for rupture disc details.

Our options and accessories ensure our rupture discs and holders perform in any environment. Consult a representative if you aren’t sure which you need.

Corrosion-resistant liners, coatings, and other protective materials available on request

Gaskets for a perfect seal, even on scratched or pitted disc holders

Protective rings to prevent damage to fragile rupture discs and delicate liners from foreign material in the seating area

Cleaning for oxygen or chlorine service

Optional flow tag compatibility
For those requiring positive identification of rupture disc installations, a special union type holder allows the installation of a rupture disc with a permanent flow direction tag. The flow tag extends beyond the holder for easier verification of orientation after installation (not available in 2″ 2000# configuration).

Muffled plugs
If the unit has a threaded outlet, we can add a muffled plug to reduce reaction forces upon disc rupture and redirect fragments or product from dispersing directly from the nozzle. Contact us for more information.

Wing, hex, and hammer nut options available
Wing nut union holders have coarse threaded nuts and subs for maximum strength and easy assembly.

Wing nut and hammer nut union holders are supplied with extra-heavy hammer lugs – a favorite of field personnel who replace rupture discs in hard-to-reach locations.


We’ve spent decades refining our manufacturing processes with efficiency and agility in mind. We’re ready to put our methods to work for you.