Daglio joked that there are many terms in use now to attempt to convey just how important valves are. Whether they’re called “supercritical” or “ultracritical” or just “critical,” the bottom line is that valves are essential to the operation of many systems. They must also function in increasingly high pressures and temperatures, as well as in unconventional and extreme environmental conditions, while being robust enough to stand up to highly corrosive chemicals and meet end-user requirements for near-zero leakage, especially valves in gas service.
There is a global need to raise the quality levels of the products made by valve manufacturers and to meet qualification requirements it is important to understand what constitutes failure modes. As outlined in the chart below, Daglio listed three types of failure: Failure to Operate, Leakage and Catastrophic Failure.
“They can all lead to probability of failure on demand and the reduction of time between failures,” said Daglio. “We need to decrease the probability of failure and increase the mean time between failures… to achieve these goals, countries, standards organizations and the major end-user players in the industries have developed their own codes and standards and the tests that must be passed to meet them.”
Daglio offered the following definitions of tests as per British Standard EN736, Part Three.
- Type Test: This is carried out on one or more valves representative of the design and the manufacturing process to confirm performance of the product with specified requirements.
- Production Test: This is carried out on valves during the manufacturing process to confirm conformance of the product with specified requirements.
- Acceptance Test: This is carried out in accordance with the technical specifications agreed upon in the purchase order.
The problem, according to Daglio, is that qualification means different things to different people and organizations, and each product must pass performance and quality assurance tests and meet criteria stipulated in contracts, codes and regulations. “Every qualification program at every latitude in every document aims to confirm the ability to seal, to confirm the suitability of the material selection, both metal and non-metal, and the ability to withstand certain temperatures, pressures or chemical condition. Generally, environmental containment is the primary goal for companies, countries and standards organizations.”
Laws of the Land
“You can’t get away without meeting these [laws of the land],” said Daglio. “When you are determining qualifications that customers need, there is room for a certain degree of negotiation, but not so with laws of the land.
“As far as I know, the U.S. is the only country that regulates methane release, from wellhead to outside the fence,” he said. “And it must be below 500 ppm.”
The Bureau of Safety and Environmental Enforcement (BSEE) also has regulations, including those concerning how subsea valves and boarding valves must be monogrammed for deep water and very high pressure situations. To apply for the monogramming is a very difficult process, and the need for this is reflected in customers asking for PR2 or 6AV1 (sand service) monogramming. Even the military, including the United States Coast Guard, has special requirements, including that valves must be Fire Tested to API 607. Many grey areas exist, and there must be agreement between the user specifications and the laws of the lands.
The regulations are somewhat convoluted and the sheer number from different agencies can make it difficult to know whether they are being met or not. Daglio suggested that what flexibility is allowed should be written in the codes to eliminate uncertainty.
(Editor’s Note: At the time of Daglio’s presentation, the EPA had new fugitive emissions regulations. Whether they will be enforced in the future is yet to be determined.)
Australia has very strict quarantine requirements (40 days), which must be considered when evaluating delivery times. Additionally, the equipment shipped to Australia must be re-tested there. “And, if you think about difficulties, think about European requirements,” Daglio said. “You must have a CE mark for top side valves plus pressure equipment directive (PED) and ATEX and others.”
PED provides a series of essential safety requirements that must be met for equipment under pressure and there is a series of modules that define the standard of inspection and third-party involvement. This may also require manufacturer certification (H1).
ATEX certification is required to prove that equipment is designed to prevent the generation of ignition sources such as electric sparks, electrostatic discharges, electromagnetic waves and mechanically generated sparks.
According to Daglio, API6D, 24th edition, is the first edition where quality levels are defined. For a given product, you will assign a quality level that will dictate which ND (non-destructive) test you need to pass in order to have that quality level. When you get to quality level 3 or 4, you must do extended FAT (factory acceptance testing) and longer-lasting tests: more cycles and more tests. Some of these requirements were inspired by 6A. Most of the players on 6D are on the 6A committee and are working to keep things consistent. A new edition will be released in 2017.
Historically, PR2 is the most demanding qualification program in the API world for non-subsea products. API 6A is for high pressure and also has an annex for high temperature. 6A drives material selection and many other things that 6D does not. “If you have a product that is PR2 approved, it’s a good selling point and it is sometimes the only way you can sell something to an end user,” said Daglio.
A 6AV1 (specification for validation of wellhead surface safety valves and underwater safety valves for offshore service) monogram can only be acquired at Southwest Research Institute in San Antonio.
17D is 6A for subsea applications, so they have their parallel PR2. Daglio noted that one of the differences is that the number of cycles as per 17D is double and you may be required to do some of those cycles in an hyperbaric chamber to assess the pressure outside the boundary, to mimic the deep-water installation.
API591 is process valve qualification procedures. “One of the curious things is that it is mandatory to have the testing run at a third-party facility and it requires ND and FAT as per 59A. So, it is a downstream valve code and qualification program together,” said Daglio.
End User Specifications
“While most other major players do, Exxon Mobil doesn’t really have a clearly stated qualification program,” noted Daglio. “But it does have a specification called elastomer and thermoplastic selection and qualification guidelines for oil and gas production.”
All valve manufacturers must pass Shell’s EVADOC, Technical Audit and Design Validation Testing (DVT) to be registered on the company’s Technically Approved Manufacturer’s and Products List [TAMAP]. If you are not on that list, you cannot bid. “You must show design evaluation as per their specifications, post a technical audit, and there are many other testing requirements,” said Daglio.
BP’s requirements are very strict, and engineers there are actually writing addenda to API codes. Daglio noted that, in the specific case where you are using one valve to achieve isolation, you must pass a specific test with pressure increments inside the body cavity.
Chevron has its own definition of a “major capital project,” and to bid on these, you are most likely required to have a PF2 and ISO fugitive emission qualification.
Manufacturers are required to jump through many layers of approval hoops to obtain certification for products across the three groups of requirements. Daglio posed this question: “Is it possible, some time in the future, for all levels to agree on something that achieves the qualifications and pleases everyone?”