COVER STORY: CDI PRODUCTS
LESSONS IN LEAKAGE RATES
A valve’ s leakage performance is measured through a rating system: Class C, Class B, and Class A. These classes represent the allowable leakage rates. Class C is attributed to typical graphite seals. Graphite does not seal quite as tightly as polymer so there is a particular allowable rate. Class B is geared more towards polymer seals and falls into an even tighter class of sealing, so less emissions are allowed to be detected during testing. Lastly, Class A is the tightest of all allowable emissions, and this specification is typically reserved for metal welded bellows. Metal bellows have many undulations, so they can compress and decompress and can be welded in place. This specification enforces how much a gas like methane can permeate through that metal.
Measuring Cycles
During the ISO 15848-1 test, the valve is opened and closed many times to approximate actual performance in the field. The endurance class sets the requirement for the number of mechanical cycles the valve must endure while leakage is measured. CDI’ s seal tested at CC1, which equates to 20,000 mechanical cycles at pressure, with 10,000 cycles at high temperature and 10,000 cycles at low temperature. Leakage detection occurs continuously throughout the test, so it is crucial that CDI’ s seals maintain their integrity throughout the 20,000 cycles, not just at ambient temperatures but during the extreme temperatures as well.“ We stepped up our cycle count and lowered our leakage rate. We made it to the next tier of our product line offering, and that is why this is so monumental for us,” enthused Ward.
Executing the Process
The CDI process typically begins with a customer’ s request for a solution.“ We work collaboratively with our customers to ensure we fully understand all of their application details before we begin working,” said Ward. CDI then uses that information to design seals, bearings, functional components or other elastomer, thermoplastic, or other polymer-based material product that will meet their customer’ s requirements. Using their in-house knowledge of seal design and simulation tools like Finite Element Analysis( FEA), CDI determines the best seal geometries, component configurations, and materials that best meet the application and testing requirements. CDI’ s manufacturing team becomes involved at this stage, working in design for manufacturability mode, or DFM, to ensure design elements are repeatable and manufacturable.“ At this point in the project, we validate that the product we are offering is manufacturable, repeatable, and delivers on all our criteria success points,” explained Ward.“ Our in-house engineers and material scientists ensure we are offering the correct material for the application. We enlist our design experience from previous successful sealing applications to make sure the whole system works together.” The team at CDI creates drawings which the company then shares with its customers to convey how they intend to solve the application.
Collective Testing
Testing can often be performed by multiple parties to ensure CDI’ s seals will meet their requirements. CDI can perform in-house testing before shipping the product to the customer to simulate how the seals perform in a test fixture that approximates the customer’ s equipment. The customer typically tests CDI’ s seals in its equipment to industry specifications which are driven by the end user. Additionally, often a third-party can be contracted to perform testing when the customer is unable to perform the test themselves.“ We conduct incremental improvements in our seal designs at our internal test facilities, so we are
8 FUGITIVE EMISSIONS JOURNAL • JUNE 2025