Gate Valve Testing Procedure: Shell Test, Seat Test & Inspection

2. Gate Valve Shell Test (Pressure Strength Test)

2.1 What Is a Shell Test?

A shell test checks the integrity and external tightness of a gate valve's pressure-containing parts under the specified test pressure.

The test mainly checks the following components:

• Valve Body
• Bonnet
• Body-Bonnet Connection
• Other pressure-containing and external sealing areas

Water is the usual shell-test medium. The valve is pressurized to the specified test pressure and checked for external leakage or abnormal deformation.

2.2 Gate Valve Shell Test Procedure

The shell test follows five basic steps:

• Step 1: Fill the Valve with the Test Medium
  Fill the valve with clean water, ensuring that no air remains trapped inside the test chamber.
• Step 2: Remove Trapped Air
  Vent the remaining air so it does not distort the result and the test pressure acts evenly on the valve's internal surfaces.
• Step 3: Apply the Test Pressure
  Gradually increase the pressure to the specified test value according to the valve's design pressure and applicable testing standards.
• Step 4: Maintain the Test Pressure
  Hold the specified test pressure for the required duration while checking for:
  Leakage
  Pressure drops
  Abnormal deformation
• Step 5: Inspect the Test Results
  Inspect the valve body, bonnet, and their connections for leakage or structural abnormalities. The valve passes the shell test when it meets the specified acceptance criteria.

 Gate Valve Shell Test 

2.3 Typical Gate Valve Shell Test Pressure

Shell test pressure is typically higher than the valve's rated working pressure. The actual test pressure depends on the applicable testing standards and project requirements.

The values above are for reference only and apply under specific test conditions.

Note: API 598, EN 12266-1, and ISO 5208 may specify different test pressures and holding times. Use the applicable standard and customer specification for the actual test.

3. Gate Valve Seat Test (Leakage Test)

A seat test checks for leakage between the gate and valve seats when the gate valve is closed.

The seat test may use water or air, depending on the applicable standard and project requirements. The result shows whether the valve meets the specified sealing requirements.

3.1 Low Pressure Air Test

Low-pressure air testing can reveal small sealing defects.Apply low-pressure air inside the valve, then check for bubbles or a pressure change that indicates leakage.

This test mainly helps identify:

• Small leaks
• Sealing surface defects
• Assembly issues

Air and water tests use different leak-detection methods, so their acceptance criteria may also differ.

The applicable standard and customer specification determine whether a low-pressure air test is required. Some gate valves do not require it.

3.2 High Pressure Water Test

High-pressure water testing checks the sealing performance of the gate and valve seats.

During the test, the valve is closed, and water pressure is applied according to the applicable testing standards to check for leakage at the valve seats.

The basic procedure includes:

• Install the gate valve on the testing equipment and close it.
• Fill the specified test side with water and remove any trapped air.
• Gradually increase the pressure to the specified test value.
• Maintain the test pressure for the required duration.
• Check for seat leakage and determine whether the valve meets the acceptance criteria.

Gate Valve Seat Test

4. Final Inspection Before Shipment

After pressure testing, inspect each gate valve against the technical specification and customer requirements before shipment.

4.1 Visual and Marking Inspection

Check the valve surface, coating, and markings for:

• No visible casting defects
• The coating meets the specified requirements
• Valve size, pressure rating, and material markings are correct

4.2 Dimension Inspection

Dimensional inspection covers:

• Face-to-Face Dimension
• Flange Drilling Dimensions
• Overall Valve Dimensions

Dimensional inspection is especially important for valve replacement projects, as mismatched dimensions can cause installation problems on site.

4.3 Material and Document Verification

Required material documents may include:

• Material Certificates
• Chemical Composition and Mechanical Property Reports
• EN 10204 3.1 Inspection Certificates

4.4 Operation Test

The operation test checks:

• Smooth opening and closing
• Proper operation of the handwheel or gearbox
• Valve operation meets the specified requirements

5. Frequently Asked Questions About Gate Valve Testing (FAQ)

Q1: What is the difference between a shell test and a seat test?

A shell test checks the integrity and external tightness of the valve body, bonnet, and other pressure-containing components.

A seat test verifies the valve's internal sealing performance when it is closed.

These tests serve different purposes and cannot replace each other.

Q2: What is the test pressure for a PN16 gate valve?

When the shell test is performed at 1.5 times the rated pressure and the seat test at 1.1 times the rated pressure, the typical test pressures for a PN16 gate valve are:

• Shell Test: 24 bar
• Seat Test: 17.6 bar

The actual test pressures depend on the applicable testing standards, valve design, and project requirements.

For water supply, wastewater treatment, HVAC, and industrial piping projects, buyers need to check the valve material, pressure rating, connection dimensions, test standard, and acceptance criteria.

UNION VALVE manufactures resilient seated and metal seated gate valves in China. Final inspections follow the product specification and project requirements.

For gate valve specifications, drawings, or a quotation, contact UNION VALVE with your piping or distribution requirements.

If you're looking for a reliable gate valve supplier for your piping projects or distribution business, contact UNION VALVE for technical specifications, drawings, and quotations.

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