Double Block and Bleed Isolation Plugs

EST double block and bleed isolation plugs create a monitored cavity for pipe weld isolation and localized hydrostatic testing.

Published family range: 3/4–48 in. NPS (DN20–DN1200), with size-specific selection.
Up to 2,250 psig between seals; standard upstream limit 10 psig (0.7 barg).
Confirm pipe schedule, bore, seal material and required monitoring accessories.

EST double block and bleed (DBB) plugs isolate a local section of pipe for connection work and weld testing. The three-port arrangement supports filling and venting the cavity between the seals while monitoring the upstream side. Localized testing uses a smaller volume of test medium than filling the complete line.

Between-seal pressure is not upstream pressure

The standard DBB design has a published maximum of up to 2,250 psig (155 barg) between the seals, but only 10 psig (0.7 barg) upstream. Confirm the exact assembly and operating limits before selection. These two ratings apply to different zones.

For applications requiring a different upstream-pressure capability, compare the GripTight isolation plug with mechanical grippers. The conventional DBB and GripTight assemblies are separate products and must not be selected solely by their shared between-seal test rating.

Size and configuration selection

The current manufacturer catalogue lists 3/4–48 in. NPS (DN20–DN1200). The linked DC2687 chart covers 3/4–24 in. configurations; request size-specific documentation for larger assemblies. Select by measured pipe bore, schedule, material, weld geometry and available installation space.

Standard seals are urethane, with alternative materials requiring compatibility review. Confirm the required gauges, hoses, fittings and handling equipment in the quotation; the technical sheet lists accessories that are not included with particular configurations.

Isolation and testing overview

The plug is installed and monitored under the manufacturer’s instructions and the approved site procedure. After welding and the required cooling, it can be repositioned for the specified localized test. Hot-work authorization, isolation controls and required weld inspection remain part of the project work plan.

Double block and bleed product demonstration. Use the applicable operating instructions for the supplied assembly.

Technical specifications and operating instructions

Double block and bleed technical specification sheet — DC2687 (PDF). Find the matching operating instructions in the manufacturer’s test and isolation plug library.

Selection and maintenance questions

What temperature and weld clearance should be used?

Confirm the seal material and temperature limit for the supplied plug, and follow its operating instructions for distance from the weld, cooling and monitoring. Weld heat, geometry and duration affect the seal temperature; a single clearance is not a guarantee for every application.

Can the plug pass an internal weld protrusion?

Check the measured bore, internal weld profile and plug clearance before selection. Clearance depends on the particular size and assembly; provide the dimensions to Justram for review.

How long does a localized pressure test take?

Timing depends on access, installation, weld cooling and the required test procedure, including the specified hold time and inspection. Plan the work from the approved procedure rather than a fixed product-page time estimate.

What inspection and storage are required?

Inspect seals, O-rings and mechanical components before use, and follow the manufacturer’s maintenance and storage instructions. Identify replacement parts by the plug model and size.

Send the pipe dimensions, material, local test pressure, expected upstream pressure, medium, temperature and access details. Request a double block and bleed plug quotation, or review the test plug range.