More C The numerical values in this specification are not presented in inch-pound units, but rather, in metric or SI units only. All rubber gaskets shall meet the dimensions, tolerances, and physical requirements of both standard gasket and oil resistant gasket requirements. Assembled joints should pass the following performance test without leakage at the joints: pipes in straight alignment, and pipes in maximum deflected position.
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However, a recent addition to ASTM standards for pipe and gasket design means precasters who use pipe gaskets in their products need to be aware of coming changes. While the standard has been around for several years, it is now reaching the point where it may appear as a project specification requirement, and precasters need to be ready. The new standard introduces a different way of thinking about joint and gasket design. The old understanding is pipe and gaskets are related but separate components.
Joint designs have been a compromise between ease of manufacturing and product precision. The new thinking is the pipe joint and gasket form a system and minimize variation by providing sufficient inspection efforts at the proper process points to reduce or eliminate problems. As a result, a higher level of overall quality is achieved and everyone benefits.
Overall, costs could be reduced for both the precaster and the customer. ASTM C introduces new thinking about joint and gasket design. Photo courtesy of Press Seal Gasket Corp.
Some precasters will discover many products and processes are compliant or can easily be made compliant, while others will discover compliance challenges. Legacy equipment may need to be replaced, inspection gauges and processes may need improvements, gaskets may need to be changed or a new supplier may need to be found. Additionally, staff may require extra training.
While the changes are numerous, some of the key differences for precasters and suppliers to know include: Scope. This is what defines which products are included within the standard. Gasket physical properties. However, the classes are different and the requirements for ASTM C are considerably more stringent. Gasket dimensional tolerances.
Joint design. An important change in ASTM C is it limits joint tapers to no more than 2 degrees, 3 degrees if testing proves adequate. ASTM C allowed taper angles up to 3. Precasters with equipment having a taper in excess of 3 degrees will need to re-equip to meet the new standard.
Test methods gaskets. ASTM C requires the precaster to sample gaskets and perform several quality checks. Performance requirements. ASTM C also requires a structural shear test. As a convenience to the testing producer, there is an option to conduct all the C hydrostatic and structural testing as a single test to the worst case condition.
ASTM C requires that the bell and spigot of every pipe be measured. Whether this means every size, every type or every individual stick of pipe is open to interpretation. ASTM C provides a suggested checklist to assist owners and designers responsible for reviewing joint design and geometry submittals. This checklist shows a Joint Data Form that includes important details needed for a complete joint submittal analysis.
These changes represent a push for improvement in the performance of products that comply and will likely face some setbacks.
Pipe & Gasket Design: Separate Components or a System?