Double Block and Bleed Isolation/Test Plug

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Safe and Effective Pipeline Pressure Testing 

Positively isolate and monitor potentially explosive vapors during hot work, then effectively hydrotest the new weld connection with EST Group’s Double Block and Bleed Isolation Plug. The dual-port design creates a positive pressure barrier between the seals - safely isolating hot work from any residual upstream gases. In addition, the volume of water required for a test is so small that testing can be accomplished using a hand pump.

Lightweight aluminum/steel construction makes our pipe isolation plug easy to maneuver, often allowing operators to forego the use of lifting devices or cranes, which can be in high demand during turnarounds.

Our 8” schedule 80 Double Block and Bleed Isolation Plug weighs in at just 36lbs (16.3kg) compared to other plugs weighing in excess of 100lbs (45.4kg) of the same size!

Test Pressure

  • 2250 PsiG (155 BarG)
  • Upstream pressure rated to 10 PsiG (0.7 BarG) - higher pressures available upon request

Size Range

  • 3/4” to 48” NPS (DN20 to DN1200) - larger sizes available upon request

Standard Seal Material

  • Urethane
  • Alternate materials available

Features & Benefits

  • Lightweight, aluminum and steel construction
  • Monitor potentially explosive vapors during hot work
  • The dual-port system allows water to be circulated between seals, providing improved cooling during pre/post-weld procedures
  • Uses less than a gallon (3.8L) of test media – cutting down on fill times and reducing waste/treatment expenses.
  • ASME PCC-2 Type IV Testing Device*
  • Test pressures to 2250 PsiG (155 BarG) between the seals
  • Available for NPS ranging from 3/4” to 24” (DN20 - DN600)
  • Pressure tests performed with less than a gallon of water

Double Block & Bleed Applications

Block & Bleed plugs are found in numerous applications, including:
  • Oil, Gas and Chemical Process Plants
  • Offshore Oil & Gas Platforms
  • Shipyards
  • Plant revamps and additions
  • Piping Systems, Spools, Pressure Vessels with Flanged Connections
  • Flange Replacement Programs
  • Tie-In Work

Basic Operation

  • After determining pipe and schedule size, install DBB upstream of “hot work” area
  • Expand seals by tightening compression nuts
  • Inject inert gas or water between seals (isolation zone) and pressurize
  • Monitor isolation zone pressure during “hot work”
  • After weld cools, release pressure and seal, reposition the plug’s isolation zone over the weld area
  • Pressurize isolation zone

Performing a Pressure Test

Perform the steps outlined below when conducting a pressure test on ¾” to 3” Double Block and Bleed Isolation Plugs:
  • Step 1: Attach hoses to the pressure and upstream monitor connections plug. (¼ NPT ports)
  • Step 2: Place plug, so both seals are inside the pipe you are testing.
  • Step 3: Remove residual air between the seals, if necessary.
  • Step 4: Hand tighten the hex nut until the test plugs grip the pipe ID. Slight wiggling of the plug may allow for further hand tightening of the hex nut.
  • Step 5: Using a calibrated torque wrench, tighten the hex nut to the normal installation torque.
  • Step 6: Slowly introduce the test pressure. (If performing a pressure drop test, hold the desired pressure with the pump for a minimum of 5 minutes to allow parts to settle prior to closing the isolation valve).
  • Step 7: After isolation or testing application is complete, release all pressure from the pipe.
  • Step 8: Loosen the hex nut until the top of the nut is at the top of the threads.
  • Step 9: Remove the plug from the tube end.
  • Step 10: Inspect the plug for wear and replace any worn components. 


Curtiss Wright EST’s Double Block & Bleed Isolation Plug will enable you to positively isolate and monitor potentially explosive vapors during “hot work”.

In need of a high-pressure isolation plug? Check out our GripTight Isolation Plug

*ASME PCC-2 (Article 503) - “Test Devices for Localized Pressure or Tightness Testing of Welded Repairs


Why perform a pressure test?

Conventional flange-to-pipe weld testing can create dangerous conditions for workers and carry high costs, including downtime, delays, and wastewater disposal issues. The GripTight Isolation Test Plug integrates a Double Block and Bleed plug with our GripTight gripper technology, ensuring operational safety and minimizing the risk of blowout/expulsion due to unexpected upstream pressure in the line.

What is the temperature rating of the Urethane Seals, and will the close proximity to the heat transfer area compromise the seals during the welding process?

The temperature rating for the Urethane seals is 180°F (82°C). When the plug is installed 12” (305 mm) from the weld, the distance between the weld and the Double Block and Bleed Isolation Plug allows the heat to dissipate and decrease to a temperature that is within the rating of the seals.

Will the Double Block and Bleed Isolation Plug accommodate slight weld intrusion?

The Double Block and Bleed Isolation Plug is designed with increased clearance (up to 3/8” on larger size plugs) to allow the plug to be positioned over the weld for testing even when slight weld intrusion is present on the Inner Diameter of the pipe.

What is the average amount of time required to install a Double Block and Bleed Isolation Plug and achieve a pressure test?

After the weld area has cooled to an appropriate temperature, the Double Block and Bleed Isolation Plug can be used to complete pressure tests in as little as 10 minutes from insertion to removal.

What upkeep and storage conditions are required to preserve the quality and performance of the Double Block and Bleed Isolation Plug?

The Double Block and Bleed Isolation Plug require periodic inspection of the O-Rings and Seals prior to testing. The compression shafts should be inspected, and anti-seize should be applied as needed. After a test has been completed, the compression nuts should be retracted so the seals can fully relax, allowing the Urethane Seals to return to their original size, preventing any permanent swelling and/or deformation.

Curtiss Wright EST’s Double Block & Bleed Isolation Plug will enable you to positively isolate and monitor potentially explosive vapors during “hot work”.