Hydrostatic Testing Pipe: What Pressure and Hold Time Do You Need?

Quick Answer:

A hydrostatic testing pipe is filled with water and pressurized above normal to prove strength and prevent leaks. This tests whether it is strong enough and leak-free. For individual PTFE-lined pipes, ASTM F423 requires a hydrostatic test at 400 psi (27.6 bar) minimum. It also requires ambient temperature, with the component filled with clean water and all air bled out. YOUFUMI’s PTFE-lined pipe meets these test conditions through ASME B16.5 flanged steel shells and ASTM F423 PTFE liners.

What Is Hydrostatic Testing? Why Are They Required for Lined Pipes?

Hydrotesting involves putting water in the pipe to fill it and pressurize it at a value higher than the design pressure. The Canada Energy Regulator describes it as testing a pipeline for strength and leaks. Engineers also call it pipe pressure testing.

Water works best because it is incompressible and stores little energy. A failure releases far less force than a gas test. The hydrostatic test exposes weak spots, manufacturing flaws, and leaking flanged joints before startup.

Hydrostatic pipe pressure testing verifies that the complete lined assembly can contain fluid without leaking. However, this test is only a snapshot and cannot predict future problems.

This test also confirms that the PTFE liner seals properly where the flared liner meets the mating flange. This is because PTFE-lined pipes are used for corrosive services, so a defect can be costly and hazardous. Hydrostatic testing proves that the seal remains intact so chemicals do not infiltrate the lined pipes.

What Are the Required Settings for Hydrostatic Test Pressure?

Following a hydrostatic test pressure chart ensures a controlled proof load. Without a controlled setpoint, the result cannot be evaluated, repeated, or accepted against a specification.

Set the hydrostatic test pressure at 1.5 times the design pressure. After that, correct it for temperature using the stress ratio.

ASME B31.3 states the formula as PT \= 1.5 × P × (ST/S). PT is test pressure, and P is design pressure. ST is allowable stress at test temperature, and S is allowable stress at design temperature.

PTFE-lined pipe runs up to about 200 °C, and carbon steel allowable stress changes little in that range. The ratio therefore stays near 1.0 for most lined systems.

Use this hydro test pressure chart for a stress ratio of 1.0:

Check every value against the flange rating. A 24 bar test exceeds the 19.6 bar ambient rating of a Class 150 carbon steel flange. Confirm the liner limit with the manufacturer first.

PTFE Spacer

Different Lining Methods; High Density; High Permeation Resistance; Vacuum capability

View Product

What are the ASME Requirements for Lined Pipes?

There are different ASME code requirements for lined pipes.

ASME B31.3 is relevant to PTFE/PFA-lined pipes because they cover process piping, including non-metallic piping and non-metal lined piping. Meanwhile, B31.4 and B31.8 are for pipelines that transport liquids/slurries and gas. The latter is only relevant when lined components are used within pipelines that are governed by these codes.

Each code also sets a different test pressure and hold time, so it is best to match the code to your service.

• ASME B31.3 for process piping: The pipes should be tested at 1.5 times design pressure and held for a minimum of 10 minutes. After that, drop to design pressure for leak checks.
• ASME B31.4 for liquid pipelines: The pipes should be tested at 1.25 times maximum operating pressure and held for at least 4 hours.
• ASME B31.8 for gas pipelines: The pipelines should be tested at 1.25 to 1.5 times maximum operating pressure by location class. After that, hold for at least 8 hours.

PHMSA adds another rule for liquid lines under 49 CFR 195. If the piping is not visible, run an extra 4 hours at 110 percent of operating pressure.

Lined pipes usually fall under B31.3, because it serves corrosive chemical lines rather than hydrocarbon transport. YOUFUMI PTFE lined pipe suits acid and chloride service in these systems. YOUFUMI PTFE lined ball valves also complete the line with matching flange ratings and tested body seals.

What Are the Testing Differences Between Lined Pipes vs Bare Pipes?

There are distinct differences between lined pipes and bare pipes.

Lined pipes need slower pressurization, tighter bolt control and closer flange inspection than bare pipes. Bare pipe testing focuses on welds, so inspectors check welds and threaded joints for weeping.

Here are some testing guidelines:

1. Fill the pipes from the lowest point and keep the high-point vents open. Trapped air may distort the pressure readings.
2. Raise pressure in 25 percent steps and pause about 5 minutes at each step.
3. Use at least two calibrated gauges.
4. Torque bolts to the manufacturer’s value. PTFE creeps under load, so tighten them again after the first pressure cycle.
5. Check shell vent holes. Water at a vent hole points to a liner defect.
6. Keep test water above 5 °C. Use water below 50 ppm chloride when the line includes 300-series stainless parts.
7. Record pressure and temperature at the start and end of the hold. Temperature change can mimic a leak.
8. Release pressure gradually, drain the line and dry it with air or nitrogen.

Lined Instrment Tee

Different Lining Methods; High Density; High Permeation Resistance; Vacuum capability

View Product

Conclusion

Successful hydrostatic testing pipe work needs three controls: 1.5 times design pressure, the right hold time, and flange limits. Set each hydrostatic test pressure from the governing code, then confirm it against flange and liner ratings. Lined systems also need slow pressurizing and careful venting.

Since YOUFUMI’s beginning in 1989, quality in service and production has been the business model’s foundation. We manufacture pipe fittings, compensators, lining containers, and pumps.

Contact YOUFUMI’s engineers and send your design pressure and medium for a matched specification.

Frequently Asked Questions

1. How long should a hydrostatic test be held?

Hold at least 10 minutes under ASME B31.3, then inspect all joints. Project specifications often extend this to 30 to 60 minutes. Pipeline codes require 4 to 8 hours.

2. What pressure should a hydrostatic test be set at?

Set process piping at 1.5 times the design pressure, adjusted by the stress ratio. Pipelines use 1.25 times the operating pressure or more. Never exceed the flange or liner rating.

3. Is hydrostatic testing required for lined pipe?

Yes. ASME B31.3 requires pressure testing of process piping. Lined spools need a shop test before shipment and a field test after installation. Records should show date, system, test fluid, pressure and examiner.

4. What causes a hydrostatic test to fail?

Loose flange bolts, a damaged liner flare and misaligned gaskets cause most failures. Trapped air, water impurities and temperature swings also distort readings. Any repair needs a retest.