This article gives detailed information regarding the annular chambers and related piping leak test. During
this test, tightness of D/F and Ex/Ra internal circuits, including annular chambers, piping, flexible hoses and
welding’s is checked. This is also related to Internal Piping Leak Test in Vessel and Internal Towers for Refinery and Plants.
What is Annular Chamber?
Annular chambers are spaces that exist between two concentric pipes or casings in a well or pipeline system. These chambers are designed to provide various functions and serve specific purposes in different applications. Here are some key points about annular chambers:
- Definition: An annular chamber is the annular space between an outer pipe or casing and an inner pipe or casing. It forms a ring-shaped cavity between the two pipes.
- Purpose: Annular chambers serve several purposes, including:
- Primary Containment: In well construction, annular chambers provide a barrier between the wellbore and the surrounding formations, preventing the migration of fluids or gases.
- Secondary Containment: In pipelines, annular chambers act as a secondary barrier, containing any leaks or spills that may occur in the primary pipe.
- Fluid Management: Annular chambers can be used for fluid circulation, injection, or extraction, depending on the specific well or pipeline operation.
- Insulation: Annular chambers can provide thermal insulation, helping to maintain the temperature of the fluid inside the inner pipe.
- Construction: Annular chambers are typically created during the installation of the pipes or casings. The outer pipe is usually larger in diameter than the inner pipe, leaving an annular space between them. Various sealing materials, such as cement or grout, may be used to fill and stabilize the annular chamber.
- Monitoring and Maintenance: Annular chambers require regular monitoring and maintenance to ensure their integrity and functionality. This may involve periodic inspections, pressure testing, and remedial actions if any issues are identified.
- Well Control: In well drilling and completion operations, annular chambers play a crucial role in well control. By maintaining the pressure balance between the wellbore and the annular space, they help prevent blowouts and maintain well stability.
- Environmental Considerations: Annular chambers in pipelines should be designed to prevent the escape of fluids or contaminants into the environment. Proper sealing and monitoring systems are essential to minimize any potential environmental impact.
Pressure Test for Annular Chamber Tightness
Safety Precautions
Personal protective equipment required (gloves, long sleeve working suit, protection glasses etc…)
Manpower
• 1 Supervisor
• 2 helpers for checking of leaks
Material
► 2 leak test devices (see next picture) equipped with (for each)
o 1 pressure gauge (calibrated precision gauge, range: 0-5 bar g, precision 0.1 bar)
o 1 release valve
o 1 quick connection to Instrument Air network
► Two special blinds with an adapted diameter (3 % or 4″ for example) to which leak test device can be connected easily (refer to next picture for typical leak test device installed on special blind).
► Final gaskets for all Annular Chambers nozzles and bridges to panels.
► Temporary blinds (already used as temporary gaskets during piping fitting) for all connections of the
piping to the tray panels or to bridge.
Pressure Test for Adsorbent Tower Annular Chamber Tightness
Test method for one annular chamber and associated piping, to be performed for adsorbent beds 1 to 11 and 13 to 23.
Preparation of the test
► On only one quadrant install
0 the special blind with leak test device on one of the D/F nozzles at the connection of a 6A/6B/3A/3B tray type,
0 the special blind with leak test device on one of the Ex/Ra nozzles at the bridge flange linked to a 6A/6B/3A/3B trav tvoe .
•
Pressurization of Annular Chambers
► Slowly pressurize the Ex/Ra annular chamber and related piping with instrument air to a pressure of 1 bar g and disconnect the air supply.
► Check all the Ex/Ra nozzles, including the external nozzle, with soapy water to make sure there are no leaks.
► Slowly pressurize the D/F annular chamber and related piping with instrument air to a pressure of 0.5 bar g and disconnect the air supply.
► Check all the D/F nozzles, including the external nozzle, with soapy water to make sure there are no leaks. At this intermediate stage piping tightness is considered satisfactory when:
► Pressure loss of the Ex/Ra circuit is less than 0.05b/h over 2 hours.
► Pressure loss of the D/F circuit is less than 0.025b/h over 2 hours.
► No pressure transfer is visible from one circuit to the other (means no increase of D/F circuit while decrease of the pressure in Ex/Ra circuit).
► Depressurize slowly the Ex/Ra annular chamber until completely depressurized.
► Depressurize slowly the D/F annular chamber until completely depressurized.
Preparation of the internal piping for final inspection
► Disconnect the Leak test devices.
► Remove the temporary blinds from the piping to bridge/panel connection and insert the sleeves around the pipe.
► Install all the final gaskets (to be checked by Axens before installation).
This procedure ensures a complete tightness of the D/F and Ex/Ra internal circuits, including annular chambers,
piping, flexible hoses and wildings.
Read Also:
Recommendations for Tower and Vessel Internals Operation in Plants & Refinery