Why is Water Pressure Testing Necessary After Overhauling the Heat Exchanger?
The purpose of conducting a pressure test after maintenance is to verify the heat exchanger's ability to safely withstand the design pressure, ensuring compressive strength, tightness, interface or joint quality, welding integrity, and sealing structure tightness. Additionally, the test allows for the observation of residual deformation in the base metal weld of the vessel and pipeline to identify any existing material problems promptly.
Here is a brief description of the sequence and requirements for the pressure test and maintenance of the heat exchanger:
Pressure Test and Maintenance Sequence:
Preparation Stage:
Prepare the purge tool.
Remove the outer head, tube box, and flange at the float end.
Remove the inner head at the float end.
Remove the tube bundle.
Inspect and clean.
Pressure Test (I):
Prepare gaskets, blind plates, and pressure testing tools.
Install the tube bank.
Install the tube box and a false float head (temporary head) with a blind plate on the shell flange.
Inject water into the shell side.
Assemble pressure testing pipeline.
Test pressure (I) to check tube mouth expansion and heat exchange tube.
Remove false float head and install inner float head and blind plate cover.
Pressure Test (2):
Add a blind plate to the box flange.
Inject water into the pipe side and assemble pressure test line.
Test pressure (2) to check gaskets and tubes at the float end.
Install the outer head at the float end.
Inject water into the shell side.
Test pressure (3) to check the seal of the shell.
Remove the blind plate and fill in the inspection card.
Pressure Test Details:
Pressure Test (1):
Purpose: Check for tube breakage and expansion interface leaks.
Actions: Plug or replace broken pipes; perform supplemental expansion for leaky expansion joints (not exceeding 3 times); replace a new tube if needed.
Pressure Test (2):
Purpose: Check installation quality, focusing on inner head gasket and tube bundle of the floating head.
Action: Analyze and handle any identified leakage issues.
Pressure Test (3):
Purpose: Overall pressure test, checking the installation quality of the outer head of the floating head.
Additional Sequence and Requirements:
For Test Pressure on Pipe Side Higher than Shell Side:
Follow the specified test pressure value according to drawings or an agreed-upon method.
For Threaded Locking Ring Heat Exchanger:
Conduct shell side pressure test and step pressure test for tube side and shell side, checking relevant parts.
After Pressure Test:
Drain accumulated water inside the heat exchanger and dry if necessary.
Sequence and Requirements for Different Heat Exchanger Types:
Fixed Tube Plate:
Shell pressure test and pipe pressure test, checking relevant connections.
U-shaped Tube Heat Exchanger, Kettle-type Reboiler, and Packing Box Type Heat Exchanger:
Shell side pressure test (with a test pressure ring) and pressure test in the piping process, checking related parts.
Floating Head Type Heat Exchanger and Kettle Type Reboiler (with Floating Head Type Tube Bundle):
Use the test pressure ring and special tools for the floating head to test the pressure of the pipe and tube plate joint. Conduct pressure test in the pipeline and shell side pressure test, checking relevant joints and parts.
Here is a brief description of the sequence and requirements for the pressure test and maintenance of the heat exchanger:
Pressure Test and Maintenance Sequence:
Preparation Stage:
Prepare the purge tool.
Remove the outer head, tube box, and flange at the float end.
Remove the inner head at the float end.
Remove the tube bundle.
Inspect and clean.
Pressure Test (I):
Prepare gaskets, blind plates, and pressure testing tools.
Install the tube bank.
Install the tube box and a false float head (temporary head) with a blind plate on the shell flange.
Inject water into the shell side.
Assemble pressure testing pipeline.
Test pressure (I) to check tube mouth expansion and heat exchange tube.
Remove false float head and install inner float head and blind plate cover.
Pressure Test (2):
Add a blind plate to the box flange.
Inject water into the pipe side and assemble pressure test line.
Test pressure (2) to check gaskets and tubes at the float end.
Install the outer head at the float end.
Inject water into the shell side.
Test pressure (3) to check the seal of the shell.
Remove the blind plate and fill in the inspection card.
Pressure Test Details:
Pressure Test (1):
Purpose: Check for tube breakage and expansion interface leaks.
Actions: Plug or replace broken pipes; perform supplemental expansion for leaky expansion joints (not exceeding 3 times); replace a new tube if needed.
Pressure Test (2):
Purpose: Check installation quality, focusing on inner head gasket and tube bundle of the floating head.
Action: Analyze and handle any identified leakage issues.
Pressure Test (3):
Purpose: Overall pressure test, checking the installation quality of the outer head of the floating head.
Additional Sequence and Requirements:
For Test Pressure on Pipe Side Higher than Shell Side:
Follow the specified test pressure value according to drawings or an agreed-upon method.
For Threaded Locking Ring Heat Exchanger:
Conduct shell side pressure test and step pressure test for tube side and shell side, checking relevant parts.
After Pressure Test:
Drain accumulated water inside the heat exchanger and dry if necessary.
Sequence and Requirements for Different Heat Exchanger Types:
Fixed Tube Plate:
Shell pressure test and pipe pressure test, checking relevant connections.
U-shaped Tube Heat Exchanger, Kettle-type Reboiler, and Packing Box Type Heat Exchanger:
Shell side pressure test (with a test pressure ring) and pressure test in the piping process, checking related parts.
Floating Head Type Heat Exchanger and Kettle Type Reboiler (with Floating Head Type Tube Bundle):
Use the test pressure ring and special tools for the floating head to test the pressure of the pipe and tube plate joint. Conduct pressure test in the pipeline and shell side pressure test, checking relevant joints and parts.
