The safe and efficient operation of industrial processes relies heavily on valves performing their functions with precision. Consequently, valve testing is essential to ensure that these valves meet design specifications throughout their operational life.

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Generally, valve testing simulates operating conditions in a controlled environment to ensure valves are fit for service. Additionally, testing occurs periodically after installation as part of standard practices.

This article provides an overview of common types of valve testing and industry standards that guide these processes.

Various tests can be performed on valves; the required test depends on the application, manufacturer standards, and customer specifications. The following sections explore common tests, along with an overview of each procedure and the applicable industry guidelines.

General Pressure Testing

This test involves filling a valve body with a testing fluid, typically water mixed with a corrosion inhibitor. Technicians then apply pressure for a specific duration. The time and pressure level vary based on factors such as valve material, size, and pressure test category. Generally, the pressure level exceeds the operational or working pressure of the valve. The procedures for pressure testing differ based on the type of valve being tested. Overall, pressure tests aim to ascertain the integrity of the valve shell, seat, and seals against leakages. A valve fails the test if:

• There is distortion affecting valve operation due to the test.
• Visible leaks are present anywhere in the valve body or bonnet assembly.
• Leakage occurs via static seals (packing) and gasketed joints, unless permitted by the design test standard.

Common industry guidelines for pressure testing valves are defined in ASME B16.34, API 598, MSS-SP-61, API 527, and ISO. Many tests are recorded on paper wheel charts or manually, although digital options are becoming more common.

Hydrostatic vs Pneumatic Pressure Testing

While water (hydrostatic) is the most common test medium, pneumatic pressure testing is preferred in certain situations. Pneumatic testing typically employs air or an inert gas such as nitrogen. Hydrostatic testing is ideal for high-pressure applications where moisture sensitivity is not a concern.

In cases where moisture can damage equipment—typically through corrosion—or disrupt the chemical balance in the system, pneumatic testing is recommended. Industry guidelines suggest using pneumatic testing for cryogenic and low-temperature valves because it is challenging to remove all water after testing. The following table outlines the differences between hydrostatic and pneumatic testing according to relevant standards and practices.

Hydrostatic Testing Pneumatic Testing

Typically, the system is pressurized to at least 1.5 times the maximum operating pressure for shell testing and 1.1 times for seat testing.

Pneumatic testing is usually conducted at 10% above the maximum operating value or a maximum of 100 psi.

Pressure-relieving devices are recommended.

The use of pressure-relieving devices is mandatory.

Extensive post-test cleaning is necessary to avoid damage to components or system disruption upon starting operations.

Little or no cleaning is needed after testing.

Hydrostatic testing generally records low rates of equipment failure.

Pneumatic tests often see common equipment failures.

This process is straightforward, posing minimal dangers; thus, semi-skilled personnel can oversee it.

Due to the associated dangers, an experienced operator must supervise pneumatic testing. For example, nitrogen leakage can displace air in the test lab, risking personnel safety. Furthermore, the consequences of overpressure can be catastrophic.

Shell Testing

The valve shell refers to the main body of the device. Its testing is primarily driven by guidelines from API 598 and ASME B16.34. The valve is typically mounted on a test bench and partially opened. During testing, the shell is pressurized, with ASME B16.34 recommending a minimum of 1.5 times the valve pressure rating at 100 °F (38 °C) for hydrostatic testing. Pneumatic seat testing requires a pressure of 1.1 times the maximum allowable pressure, conducted at 80-100 psi. Both API and ASME standards suggest varying test durations based on the valve size, summarized in the table below.

Valve Size (Inches) Test Duration (Seconds)

2.0 15

2.5 to 6.0 60

8.0 to 12.0 120

14.0 300

The testing water temperature should range from 41 °F (5 °C) to 122 °F (50 °C). The pressure gauge used for measurements must have a calibration between 1.5 and 4 times the test pressure. For a valve shell to pass the test, there must be no visible leakage throughout the duration.

A valve stem seal (packing) is also monitored during shell tests. For adjustable stem seals, leakage during testing is NOT a cause for rejection, provided the manufacturer demonstrates the seal’s ability to retain at least the maximum allowable pressure without visible leakage. Adjustments to packing are allowed to eliminate leakage. In contrast, no leakage is permissible for non-adjustable stem seals during shell tests.

Seat Testing

Typically conducted after shell testing, the valve seat test follows the same API and ASME standards as the shell test. The recommended pressure for seat testing is 110% of the maximum allowable pressure at 100 °F (38 °C), with test durations varying with size in accordance with ASME B16.34.

Valve Size (Inches) Test Duration (Seconds)

2.0 15

2.5 to 8.0 30

10.0 60

20.0 120

API 598 provides similar test duration recommendations and outlines allowable leakage rates from the seat.

Valve Size (Inches) Hydrostatic Leakage Rate (Drops Per Minute) Pneumatic Leakage Rate (Bubbles Per Minute)

2.0 0 0

2.5 to 6.0 12 24

8.0 to 12.0 20 40

For valve sizes exceeding 14 inches, the hydrostatic test leakage rate should not exceed two drops per minute per inch, while the pneumatic test leakage rate should be less than four bubbles per minute per inch.

Fire Testing

Industrial valves require reliable fire protection, especially in sensitive applications such as oil and gas, refineries, and petrochemical industries. Valves in these sectors must provide dependable and safe shut-off in the event of a fire.

During a fire test, a valve is pressurized and subjected to high-temperature flames between 750 °F (400 °C) and 1,500 °F (800 °C) for thirty minutes. Throughout this period, temperature intensity and leakage—both internal and external—are monitored. After extinguishing the flames and allowing the valve to cool, technicians test its pressure-retaining capacity. All leakage levels must remain within acceptable limits for the valve to be deemed “fire-safe.” Important points concerning fire testing include:

• Leakages from the piping to valve end connections do not factor into acceptance criteria.
• Technicians must measure temperature from at least two points: one at 1 inch (25 mm) from the upper stem packing box on the horizontal centerline and another at 1 inch below the valve.

Standards such as API 607, API 6FA, ISO, BS, and BS determine fire testing guidelines. Based on these guidelines, numerous companies have established their own fire safety valve testing procedures. Among these, API 607 and API 6FA are the most commonly referenced. API 607 sets testing criteria for valves with non-metallic seating and quarter-turn valves, while API 6FA establishes criteria for metal-seated valves.

Note: Most metal-to-metal seated Gates, Globes, and Swing checks are NOT tested to API 607 due to their inherently Fire Safe Design (as there are no soft parts to melt during a fire).

Fugitive Emissions Testing

Fugitive emissions testing evaluates gas or vapor leakage from a valve. Although leakage can occur anywhere along the piping system, statistics show that approximately 60% of fugitive emissions originate from valves, highlighting the importance of this test. The implications of these emissions can be significant, including:

• Increased risk of fire and explosion.
• Economic losses from commodity leakage.
• Long-term health risks to workers and surrounding communities.
• Environmental damage.

Common test gases for fugitive emissions tests are helium and methane. The valve is pressurized with the test gas at varying temperatures, while technicians monitor for leakages using either the sniffing or vacuum method. International standards such as API 622, API 624, API 644, ISO-1, and ISO-2 provide guidance on performing this test, but most organizations tailor their specifications to ensure suitability for their applications.

Cryogenic Testing

Cryogenic testing applies to valves used in low-temperature or cryogenic services. The procedure entails placing the valve within an insulated tank filled with liquid nitrogen at temperatures as low as -320 °F (-196 °C).

During testing, helium pressurizes the valve to the specified operating pressure for its class. Technicians closely monitor the temperature inside the valve and any leaks. After depressurizing the valve, it is warmed up to ambient temperature, and a detailed report is generated summarizing the valve's performance and whether any leakages were within acceptable limits. Several international standards offer guidelines for cryogenic valve testing, including ISO-1, ISO-2, EN, and BS.

Apart from the standards mentioned earlier, there is a variety of standards that provide recommendations for various valve types and testing procedures. The table below lists these standards and the specific testing areas they cover for quick reference.

Applicable Standard Valve Type and Test Procedure

API 598 Valve inspection and testing. Applicable to cast iron gate, plug, check, and globe valves, as well as steel gate, globe, check, ball, and butterfly valves. Also includes cryogenic valves.

API 527 and ASME PTC 25 Pressure relief valves.

API 6D Pipeline valve testing.

ASME B16.34 Pressure seal valves and steel valves larger than NPS 24 inches. Applicable to flanged, threaded, and welded end valves.

MSS SP-80 Testing of bronze gate, globe, angle, and check valves.

MSS SP-70, MSS SP-71, MSS SP-78, and MSS SP-85 Testing of cast iron valves, flanged, and threaded ends.

ISA S-75, ISO, and MSS SP61 Hydrostatic testing of valves.

FCI 70-2, ISA S-75 Control valve testing.

Valve Passing at Site

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Valve Passing at Site

If you are looking for more details, kindly visit Valve Passing Test.

Dear members,

Based on API 589 closure test requirements, some passing (leakage) is permitted during manufacturer shop closure tests.

However, what about passing at construction sites during line hydrotests?
Is there any international code or standard for that case?

Keep in mind that the test pressure during line hydrotests at sites may be lower than that during shop closure tests.

Thanks in advance..

 

Replies continue below

Recommended for you

RE: Valve Passing at Site

NGiLuzzu

(Mechanical)

I'm not aware of any International Standards dealing with line hydrotests of newly constructed plants (and I would be curious to read one...). However, I believe every Engineering and End-User Company has its own specifications.

You may not find an answer to your specific question, but you might discover some useful insights related to the same subject within the discussion thread408-: "Zero Leakage" concept and EN std... Regards,      'NGL

RE: Valve Passing at Site

BillBirch

(Mechanical)

You should not perform hydrotesting against valves during line hydrotesting. This testing is meant to verify welds and other joints, meaning valve performance is not the focus. Typically, valves are removed or partially opened during this process. In general, valves are only required to pass a test during the manufacturing process. Years ago, an experienced ball valve designer shared that his business only needs to pass once (during the works test), after which their performance should consistently be assumed to be satisfactory.

RE: Valve Passing at Site

onrush

(Aeronautics)

(OP)

Thanks, BillBirch.

These valves are block valves meant for installation at the inlet of spare pumps. This means they are typically closed. What should be done in this case? Should a blank be used instead of the valve?

RE: Valve Passing at Site

BillBirch

(Mechanical)

Yes, blinds should be used because the test pressure exceeds the capabilities of the valve seats.

RE: Valve Passing at Site

benensky

(Mechanical)

BillBirch is correct. I design valves and we test and build our products to seat at 110% of rated pressure (MSS SP 61 section 4). The valve shell is engineered to meet or exceed 150% of rated pressure. ANSI B16.5 also mandates that the "flange fittings" pass a 150% rating test (section 8.3), but this pertains only to the shell testing.

Many system hydro tests are conducted at 150% rated pressure, which can lead to the seats of most of our valves lifting (some are over-designed). Similarly, other valves from different manufacturers built to the same standards may also experience seat lift or opening.

RE: Valve Passing at Site

gerhardl

(Mechanical)

I echo the previous comments regarding EN standards and confirm the presented viewpoints.

There is always a limit to the maximum pressure a valve manufacturer will allow during a line test. This limit is partially determined by the valve standard, which typically requires higher testing for the housing (open valve housing should test at 1.5 times pressure class or higher, depending on pressure class, dimensions, and manufacturer type) than for the seat (operating pressure usually equals pressure class with an additional multiplier of 1.1, which may also vary by valve type—with smaller valves often over-qualifying).

During line pressure tests, there is always a risk of malfunctions, leading to water hammer, which can permanently damage the valve sealing or the valves themselves due to overflowing the pressure on the seats.

In summary, blinds should be used and all valves left open during line tests.

Alternatively, when that is not possible, it is crucial to obtain written permission from the valve manufacturer allowing the specified pressure. Additionally, it is important to note that for certain types of resilient seated gate valves, a slightly higher seat pressure may have a lesser impact than for other constructions. However, any failures or leaks occurring after a test that exceeded the allowable pressure will place responsibility for the incident on the entity conducting the test, along with the burden of proof that all procedures were followed correctly.