ThePipingMart Blog other Learn about valve stem packing and Fugitive emissions testing

Learn about valve stem packing and Fugitive emissions testing

Regulating organizations today cannot accept fugitive emissions. Fugitive emissions are typically noticed in valves, particularly in the stem area. The quarter-turn valve offers significantly more protection against fugitive emissions because the stem movement is substantially smaller.

Fugitive emission is also being contributed to by various piping component types, particularly those with flanged-type connections. This undesirable pollution is impacting our environment. So, all process industries now have fugitive emissions reduction as one of their top priorities.

What is Fugitive emission?

A leakage or other irregular gas or vapor release from pressurized confinement, such as storage tanks, vessels, pipes, wells, valves, etc., is a fugitive emission. These are unintentional emissions brought on by pressure, either by defective parts or an oversight.

Since emissions occur in factories, power plants, waste-water treatment facilities, and other similar plants, this is not restricted to industrial settings. This emission poses a serious risk to the environment and the corresponding industry.

Fugitive emission terms for all standards

Some common terms that everyone should need to know to understand fugitive emissions are:

A type of mixture, gases found in the atmosphere are measured in parts per million volume (ppmv). Ppmv calculates the concentration of a certain gas in a mix. Example: 1 ppmv = 1 ml/1000 ml.

For control valves and isolation valves, this term is defined variously. A mechanical stroke is the cycle of an isolation valve from fully open to fully closed to open fully. At the same time, the mechanical cycle for control valves is defined as 50% of valve travel and 10% of the whole stroke.

For control valves and isolation valves, this term is defined variously. A mechanical stroke is the cycle of an isolation valve from fully open to fully closed to open fully. At the same time, the mechanical cycle for control valves is defined as 50% of valve travel and 10% of the whole stroke.

Type Testing: This is a new procedure based on fugitive emission requirements. In this test, valves are examined at the operational pressure and temperature that the manufacturer has indicated.

Test Gas: This measures the leakage rate during fugitive emission testing. The most often utilized test gases are helium and methane.

Part per million (ppm): This technique calculates how much of a very diluted substance is present in a combination. In a 1M part mixture, one ppm equals 1 part of the specific ingredient.

Ambient temperature: The air surrounding anything or the setting in which it is stored.

Room temperature is defined as the temperature at which the majority of people in a room feel comfortable. The average room temperature is between 20 and 22 degrees Celsius.

Sealing types of Valve steam

Selecting valve stem sealing material is crucial in lowering or halting FE from valves. Every sealing material has unique benefits and pressure-holding capabilities. We often utilize 05 different forms of packing for valves, including:

Flexible graphite that has been die-formed: Flexible graphite has a minimum carbon content of 95% and an end ring made of braided carbon or graphite yarn. These die-formed rings are used for higher service temperatures between 850°F and 1200°F and pressures up to 4000 psi. It has a fugitive emission capacity of 500 ppm or less.


  • For a long time, this sealing type has offered adequate emission performance.
  • These might fall short of the low leak rates required by the strictest air-quality control districts, consent decrees, and end-user standards for plant performance.
  • Rings may need to be adjusted to achieve and maintain low Emission results because they are designed for a specific valve stem and box size.
  • Requires a multi-step installation process
  • Braided flexible graphite has a higher carbon content than die-formed flexible graphite (more than 95% carbon content). Additionally, this has flexible graphite yard wire reinforcement. This sealing has a temperature range of 850°F to 1200°F and 4500 psi pressure handling capabilities. This sealing type of valve can produce less than 500 ppm of fugitive emission.


  • Superior emission performance is provided by wire reinforcement and high-purity carbon.
  • With some adjustment, different size valves can be packed using a single size of sealing component.
  • Installation requires several steps and simple field replacement.
  • Result: low emission.

Engineered sets: This sealing is created using a mix of braided and die-formed graphite rings. Although it can withstand the same temperature range, its 10000 psi pressure handling capacity is substantially higher. Fugitive emissions in sealing range from 100 to 500 ppm.


  • Highest-performing emission results
  • Every sealing set is built specifically for a certain type of valve steam and box size.
  • In contrast to other sets, it is simple to install.

The carbon rings utilized in the three types mentioned earlier of sealing sets had a purity of at least 95%. While a metallic bellow is employed in the design of Bellow sealed valves. Additionally, several packing-type seals are used as backup seals. The metallurgy, design, and construction of a valve’s flange pressure class determine its temperature and pressure retention capabilities.


  • Nearly no emissions
  • Comparable to the price of a typically packed valve.
  • There is no possibility of a correction in the event of any sealing failure.
  • A long bonnet is occasionally needed to accommodate the Bellow.
  • Space is an issue at this point.

Live loading valves: In this sealing disc, spring washers press the gland follower against the gland stud nuts. Here, the temperature and pressure capability are determined by the type of seal used in the valve. A live-loading setup does not enhance emission-holding capabilities with an increase in pressure rating.


  • Any packing material can be used in the valve when using this.
  • Effectively boosts the energy in the gland’s stud bolts.
  • Additional costs will result from live loading.
  • This helps the valve work better throughout a range of heat cycles.
  • The preferred option for valves that are challenging to access and monitor.

Why is reducing Emissions required?

Controlling fugitive emissions in valves is a must-have agenda item for the oil and gas sectors to save money and the environment due to the adverse impacts of fugitive emissions. There are numerous reasons why reducing and eventually getting rid of fugitive emissions is important. The following are a few of the causes:

Fugitive emissions cause air pollution because they allow dangerous gases to escape.

This results in additional risks and dangers like:

Volatile organic compound emissions from chemical and oil refineries put neighboring residents and workers in danger.

There is a possibility of explosion when many flammable liquids and gases are compressed under pressure.

  1. If fugitive emission is not managed, a valve, a major part of the pipe system utilized in every sector, can produce a harmful working environment.
  2. Leakage along the shaft or stem begins due to long-term emission. This prevents the controlled gas or liquid from leaking.
  3. This raises the financial price of replacing lost or damaged goods.

Thermal leak Risk mitigation

In a chemical reaction, the thermal leak occurs after the heat cycle. A critical service situation with significant pressure and temperature fluctuations may result in a leak channel in the body.

Not every valve manufacturer discloses the results of their thermal cycle tests. Therefore, it is crucial to determine if the vendor has tested and accumulated this data. The following factors should be taken into account when choosing a valve to reduce the likelihood of a suspicious leak throughout the heat cycle:

For stable temperatures, PTFE-type body gaskets are an excellent option. However, a thermal cycle will cause the PTFE to cold flow, lower compression, and result in a leak.

At most temperatures, a body gasket made of graphite performs well. Although it can withstand several temperature cycles, this is typically necessary to achieve a valve’s fire safety rating.

The advantages of PTFE and graphite are combined in a dual material body gasket to create an inert seal that can prevent fugitive emissions and guarantee fire-safe operation.

Industry-proven spiral-wrapped body gaskets with v-shaped metal spring rings provide structural support and live to load. The majority of spiral wound gaskets are sealed with either graphite or PTFE. Spirally coiled dual material gaskets are chemically resistant, capable of self-healing after thermal cycling, and unaffected by temperature ranges.

As a result of trapped fluid in the ball valve’s chamber expanding under certain conditions to create high pressure and a potential leak, self-relieving seats are intended to release the excess tension built up there.

Fugitive Emission Testing Standards

The major standards used for fugitive emission testing are 02 standards:

  • Organization of the International Standard: There are two components to this type of testing standard’s description of the testing procedure.
  1. The qualification process is for the fugitive emission test of valves for rotating and rising steam following ISO 15848-PART 1.
  2. The testing technique in ISO 15848-PART 2 provides the acceptability requirements for fugitive emissions.
  • The 03 API valve and stem sealing emission standard is the current American Petroleum Institute standard.
  1. The term “process valve packing for fugitive emission” is defined in API 622.
  2. All rising stem valves with graphite packing are tested by API 624.

API 641: Any quarter-turn valve is subjected to fugitive emission testing by this API standard.

ISO 15848 Part-1 Testing Procedure

Helium or methane are employed as the standard testing fluids in this testing process. It is accepted only when a valve passes the tightness, endurance, and temperature class tests after the fugitive emission test.

  • Valve Testing Methods
  • Vacuum testing
  • Flushing Testing
  • Bagging testing and
  • Sniffing Method
  • Vacuum Testing Method for Fugitive Emission

The total leak rate from the stem seal is measured using this technique. A spectrometer is used to measure the helium utilized as the testing medium. A tight vacuum chamber containing the stem packing is then emptied and linked to a helium mass spectrometer.

Flushing Method for fugitive emission

When inflated with helium or methane, it measures the leak rate from stem sealing. The flush chamber leaks stem packing sealed. Here, a specific gas is introduced into the chamber and mixed with fluid leaking from the valve stem.

After that, the mixture is run through an exhaust pipe. The fluid spilled into the mix is then measured in parts per million volume (ppmv).

Bagging Method for fugitive emission

Here, the testing medium is helium. After that, the air is pushed through a bag containing the leak source. The fluid from the stem packing then leaks into the mixture. The amount of leak fluid is quantified with a spectrometer and a constant flow rate detection probe, also known as a sniffer.

Sniffing Method for fugitive emission

A helium leak detector is employed in this test procedure. This detector is equipped with a sniffer probe to determine the concentration of helium in a mixture of helium and leaking fluid.

If methane is being tested, a volatile organic compound detector is employed.

Test Pressure and Temperature

Test pressure for ISO 15848 Part-1 is typically rated at the pressure corresponding to the test temperature. For instance, the valve is tested at 20 pressure for the 150# class at room temperature.

Although valves are typically rated at room temperature, there are some exceptional circumstances when the valve must be evaluated at a particular temperature.

Procedure for ISO 15848 Part 2 Testing

This Standard primarily applies to the acceptability of valve production. To be approved, this standard valve must undergo a typing test using the ISO 15848 Part-1 testing procedure.

Method of Valve Testing

Helium is prioritized for testing under ISO 15848 Part-2 standard, with a minimum purity of 97% by volume. The sniffing method is used to test fully built valves.

Furthermore, leak measurement is calculated in line with ISO 15848 part-1 and further represented in ppmv. One ppmv equals 1 ml/m3.

Steps for measuring valve fugitive emission

  • To evaluate seal leakage using the sniffing method, open the half valve and pressurize it to a pressure of 6 bar.
  • The valve should then be fully opened, pressurized to a pressure of 6 bar, and the steam seal leakage measured using the same sniffing method.
  • After a mechanical cycle, partially open the test valve and use the smelling Method to assess the stem seal.
  • According to the table below, if the sniffer probe reading is higher than the rated ppmv value, the valve is certified as “NOT OK” by the fugitive emission testing.

  Test Pressure and Temperature

Testing pressure, set at 06 bar for all valves in the time section of the ISO standard, varies according to the definitions in part 1 of the ISO standard.

API 624 fugitive emission testing standard

This testing standard applies to rising stem valves with flexible graphite packing.

API 624 Testing’s Purpose: This API standard outlines the conditions and criteria for fugitive emission testing. Valve with rising or rising-rotating stem outfitted with packing appropriate for service temperatures between -29 and 538 degrees Celsius.

This is relevant to valves that have undergone type testing under API 622 standard. Along with the valve, an API 598 certificate is also offered.

Testing and leakage measurement: In this Standard, the test medium must be at least 97% pure methane. The sniffing technique is used to test the fully built valve.

The sniffing method determines the concentration of leaking fluid, which is then stated in parts per million volumes.

Testing pressure and temperature: This Standard’s test pressure is 42 bar at 260°C, which is low, according to B16.34. Moreover, the test temperature must be 260°C.

According to API 624’s acceptance criteria, fugitive emission testing is successful if the measured leakage is under 100 ppmv.

API 641 fugitive emission testing Standard

This Standard covers only quarter-turn valve-type testing.

The API 641 standard specifies the types and processes for fugitive emission testing and the requirements and acceptance criteria. The preferred packing material on a quarter-turn valve is first evaluated following API 622 standard.

This Standard does not apply to valves having pressure ratings at ambient temperatures less than 6.89 bar. Additionally, this Standard does not cover valves larger than 24′′ in diameter and with a 1500# pressure rating.

Like API 622, testing and measurement involve checking leakage with a sniffer detecting prob and expressing the results in ppmv.

The fugitive emission test report in the test is certified as “pass” when the observed leakage does not exceed 100 ppmv. This is one of the API 641 acceptance criteria.

API 622 fugitive emission standard

This Standard was created primarily to address fugitive valve emissions in the chemical and petroleum industries.

The first version of API 622 includes a fugitive emission test for valve packing, but it also permits the testing of valves by the valve manufacturer or company. The test devices must be used in a test facility, according to the 2011 revision of this Standard.

Testing and leakage measurement: Using a methane gas test medium, the test involves 1510 mechanical cycles across five thermal processes from room temperature to 260°C. The final ten cycles of each set, divided into 300 cycles per day, are utilized to calculate the amount of fugitive leakage.

Leakage measurement and testing pressure are performed following specifications using tensions between 0 and 600 psi. A fugitive emission test is conducted at ambient or 260°C, depending on the situation.

Acceptance Criteria for API 622: If fugitive emission leaks are below 500 ppm with just one change, the leakage limit will be considered acceptable.

Performance class factor for Fugitive emission

Any valve’s performance class is determined by combining the following three standards:

Tightness Class: This determines the maximum permitted leakage at each rating of the valve through a leak test utilizing helium or methane gas as the test fluid.

Endurance Class: The number of cycles a valve must complete with no leaks, and the lowest tightness class is regarded as the endurance class.

Temperature Class: This refers to the highest temperature at which a valve may operate without leaking.


All of the standards mentioned in the previous section, including ISO 15848 (Part-1 & 2) and API 622, 624, and 641, are used to assess the valve’s and its stem packing material’s ability to handle leaks.

Each Standard has a unique method for detecting fugitive emissions according to the end-users needs. Still, these various standards make it difficult to determine the most effective Method for testing valves for fugitive emissions.

Today, every industry seeks to harmonize and hopes that a single, superior standard will develop into a global standard for fugitive emissions testing.

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