valves, valve testing, fugitive emissions, check valve, control valve, quarter turn valve, valve engineer

ISO 15848-1 vs. API 624 Testing for Valves: Which One & Why?

Fugitive emission testing for valves in refining and upstream is mandatory, and stringently regulated. However, in the midstream processes the role fugitive emission standards play is vague for end users and manufacturers alike. Without clear regulation on midstream valves, operators are forced to make their own logical decisions regarding emission control and abatement, loosely based on standards like ISO 15848-1 and API 624. What is the difference?
Fugitive emission testing for valves in refining and upstream is mandatory, and stringently regulated. However, in the midstream processes the role fugitive emission standards play is vague for end users and manufacturers alike. Without clear regulation on midstream valves, operators are forced to make their own logical decisions regarding emission control and abatement, loosely based on standards like ISO 15848-1 and API 624. Many end users are unaware of the differences between the two, and arbitrarily request fugitive emission standards that may not even be applicable to the application at hand.

Fugitive Emissions Journal was pleased to speak with John Brennan IV, Product Development Manager and Dustin Thompson, Engineering Supervisor of Franklin Valve about the difference between API 624 and ISO 15848-1 fugitive emission testing for valves, and what the midstream valve market can expect in years to come.

What is the Difference Between ISO 15848-1 and API 624?

There are several major differences between these two standards, though both are considered the most widely accepted fugitive emission standards for valves internationally.


One of the biggest differentiators be-tween API 624 and ISO 15848-1 standards is the temperature at which the test is carried out. API 624 mandates three thermal cycles ranging from room temperature to 500 degrees Fahrenheit, whereas ISO 15848-1 gives the manufacturer the option to choose from a number of different temperature classes.

“With soft seated valves, temperature becomes a problem if it exceeds our operating range. Our operating range goes up to 400 degrees Fahrenheit, so theoretically our valves would have trouble passing an API test API’s temperature requirements make it non-applicable to us at that point,” said John.

Midstream applications such as tank farms lend themselves to soft seated valves due to the criticality of isolation, and relatively low maximum operating temperatures. A tank farm may have 50-75 units each holding different products from crude oil to jet fuel that cannot be mixed. “Jet fuel mixed with crude is no longer jet fuel and will result in lost revenue. These are the applications where isolation is key and you want soft seated valves to maintain zero leakage,” said John.

“If you could, all valves would be zero leakage, but the reality is when you reach certain temperatures, or you run out of funding you will end up with an allowable leakage rate as a necessity to prioritize other goals. In midstream, there is emphasis on zero leakage, so we use soft seats that cannot reach higher temperature requirements. For that reason, as a manufacturer we gravitate toward the ISO standard,” said John.

Focus of Measurement

Another important difference is the focus of measurement. API 624 dictates focus on the performance of the packing in the valve whereas ISO 15848-1 is focused on the whole valve as a package. The general definitions are as follows:

• API 624 is a valve-type test meant to evaluate the performance of the valve’s stuffing box/stem interface while using packing sets previously qualified to API 622, only measuring leakage at other joints to correct them and note their potential impact on leakage detected at the stem.

• ISO 15848-1 specifies testing procedures for evaluation of external leakage of valve stem seals and body joints of isolation and control valves, intended for application in volatile air pollutants and hazardous fluids.

Test Pressure

API 624 has a maximum test pressure of 600 psi, or at the maximum operating pressure of the ANSI class. For example, an ANSI 150 with an operating pressure of 285 psi would be tested at such. The ISO standard would test at the max allowable operating pressure, for the selected temperature class, of the test valve’s ANSI class. For instance, an ANSI 900 class at a given material grade would be tested at 2220 psi, which is significantly higher than 600. From that perspective, ISO 15848-1 can be considered more stringent, but it is important to have a look at the multitude of variables between the tests – is the leakage rate comparable to the leakage allowance of API 624?


Another important differentiation to note between API 624 and ISO 15848-1 is the scope of the standards. The ISO 15848-1 standard is for isolation valves and control valves, is very broad and is used to categorize a performance class for valves in the realm of fugitive emissions. The API 624 scope is much more narrow – it is specifically for valves that use graphite packing. Graphite packing is generally rated to function in excesses of 500 degrees Fahrenheit.

So, why would manufacturers certify to one standard and not the other? It depends on where your valve falls in the scope of these standards. “Our valves fit into the scope of the ISO 15848-1 standard, rather than API 624. In refining, operating temperatures are much higher than midstream, so that is where the API 624’s temperature comes into play,” said John.

Mechanical Cycles

A difference that also exists between the two standards is the number of mechanical cycles the valve must go through. API 624 requires a flat, 310 cycles to pass the test. On the other hand, ISO 15848-1 defines three en-durance classes in which a valve can qualify to depending on the type and application. “For isolation valves, the first endurance class is 205 mechanical cycles, the second is 1500 and the third 2,500 cycles. Looking at the variation between ISO’s 2500 cycles versus API’s 310 cycles, ISO is more stringent, but API offers the simplicity of a singular pass or fail point. ISO’s 15848-1 re-quires end users to be cognizant of the differences between the performance class designators, ” said Dustin.

Thermal Cycles

The thermal cycles themselves are also quite different. ISO offers different temperature ranges, as well as corresponding thermal cycles, so this means while performing mechanical cycles, you will be prescribed a number of thermal cycles that the valve has to go through. API 624 requires 310 mechanical cycles including three thermal cycles. ISO has two thermal cycles per endurance class for a total of six – if testing was fully completed.

“As far as ISO endurance classes go, the further you can go, the better, as it demonstrates superior quality,” commented John. “For a customer, this translates to reduced maintenance. If they do not hit a certain ppm air quality target, the U.S. EPA can issue fines, and penalties. By reaching a higher threshold, it means end users have to spend less time maintaining it. The higher the endurance class, the higher the presumed quality. As a manufacturer you should aim for the highest endurance class possible,” continued Dustin.

Test Fluid

The test medium used differs de-pending on the standard process. API 624 uses methane, as that is the only allowable test fluid. ISO allows for methane or helium, and as far as allowable leakage rates ISO does differentiate limits for each, dependent on stem size and tightness class. To that end, the acceptance criteria for API 624 and ISO 15848-1 are also different. API 624 sets an allowable flat volumetric limit of 100 ppmv per measurement for the entirety of the test, “As opposed to API’s more pass/fail style approach, ISO’s intent ap-pears more about defining a fugitive emissions metric by which your valve can be measured and then compared, the testing simply catalogs it’s performance in this range.”, said Dustin.

As the valve industry is centered around hydrocarbons, and methane is readily available, it is widely considered standard as it is what has al-ways been used. Considerations for test fluid include knowing the end user’s preference and safety precautions, as methane holds explosive properties not found in helium.

Though helium is not explosive, the issue with helium testing is that as such a small molecule, it will get out of escape from cracks and crevices that methane would not as a larger molecule. Taking this into consideration, the ISO standard defines leak-age rates for each test medium independently. “Methane better simulates real world applications.

How Does This Translate to the End User?

The best way to educate about standards is effective communication between the manufacturer and the end user.

“A lot of the times end users are focused on what they do best, so they will send out specifications calling out what they know to be a fugitive emission standard, often API 624. As a manufacturer, I will help them understand how these two standards apply to our valves,” John continued. However, helium testing is a safer option and is easier to handle,” said John.

Which Standard Should you Choose?

In midstream, fugitive emission standards for valves are so new that there is no right answer, it depends on the application. “For our products, ISO 15848-1 makes sense. We are working together with distribution and end users to educate them on the applicability between the two options,” said John.

If the EPA intends to start heavily regulating parts of the industry that it has not in the past, the industry needs to come together with de-fined standards meeting those requirements. “If the current ISO or API standards do not meet the EPA’s requirements, they need to be updated it. If they are enough, both the manufacturer and customer need to adopt that standard, along with the industry,” said Dustin.

Image Courtesy of RFS Compliance Solutions.
Image Courtesy of RFS Compliance Solutions.
Looking Forward

Eventually, API fugitive emissions requirements will creep their way into midstream. “We rarely see any mid-stream applications that stipulate fugitive emissions requirements, but they do come in. When we do see them, the requirements are all over the board,” said John. “We will slowly start to see fugitive emissions standards be-ginning to work their way into valve standards like API 6D and 598. You will start to see callouts for fugitive emission requirements for the industry as a whole, not just for refining.”

“The API 624 standard originated in refining and upstream, but companies now are beginning to start pushing those initiatives down the process line. As there is no universally accepted API fugitive emissions standard for mid-stream valves right now in the United States, we receive a wide array of re-quests from customers including, ISO 15848-1, API 624, TALUFT, EPA Method 21, or custom in-house specifications. This lack of agreement in the industry makes it difficult for manufacturers to proactively prepare their product lines to meet customer need,” said Dustin.

“It started with the biggest piece of the pie in refining, and it will slowly make its way to the gas pump. Whether or not these standards become more stringent will depend on the U.S. Administration and changes to environmental policy, but you can expect these fugitive emissions requirements to appear more frequently in the future,” said John.

More packing companies will come out with products catered to fugitive emission abatement, valve manufacturers will have to improve focus on their finishes, machine goods, and work on qualifying entire product lines as end users demand this of their manufacturers. This will come at an increase in cost to both the manufacturer and end user.

From a design standpoint, valve manufacturers have already begun standardizing off the shelf products to meet fugitive emissions requirements for higher end valves. “Rather than waiting for customer specifications, manufacturers are moving in this direction because it is much easier to start with a design that is already built for fugitive emission requirements, than to update an existing design to fit. When you are designing a stuffing box to have certain compression rates with specific packing sets for example, there is a decrease in cost to the manufacturer if you can standardize on the fugitive emissions packing and buy in volume versus purchasing to order,” said Dustin.

Initially, it is going to be very turbulent until the industry collaborates to reach a consensus, and that will take some time. “I do not feel it will ever be homogenous one way or the other. Bigger operators will continue to pro-duce their own in-house documents,” commented John.

In the future, will API create a complete-ly new standard for midstream valves for fugitive emission abatement, or modify the existing API 624 to be more broad and reach a wider scope? “My guess is that it will be a new API standard, similar to the ISO 15848-1, in the sense that its scope encompasses a broader range of products and applications. In the next ten years, fugitive emissions standards will be implemented throughout the industry and we aim to be ahead of the curve rather than behind it,” concluded John.


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