Fireproof Assurance: Severn’s OCT TOV Butterfly Valves Exceptional Fire Safety Design and Testing Credentials
As part of a safety-first approach Severn incorporates into its innovative Oblique Cone Technology (OCT) Triple Offset (TOV) Butterfly valve, fire safety is a critical part of that safety first objective. Fire testing standards state the minimum requirements the valve must achieve in order to receive fire safe certification. The standards dictate the setup & parameters required to simulate the conditions a valve may be subjected to during a fire, and test to ensure the valve can operate satisfactorily afterwards.
To summarise, the test consists of a valve being mounted in a fire test rig to flow water through the valve, and measure leakage both internally past the seal as well as externally through the packings and gaskets. The valves are then pressure tested at ambient temperature, once the valve has passed this element of the test, any leakage is recorded. The valve is then subject to a simulated fire by use of gas burners, with average temperatures of between 750°C & 1000°C recorded by thermocouples for the 30-minute burn time. Once complete, the flames are extinguished, and the valve is subjected to a forced cooldown using water to simulate the fire being extinguished on site.
The leakage during fire is measured and recorded. The valve is then subject to a re-ambient temperature and operational test, with the maximum leakage requirements being defined within the relevant standard. The tests are carried out in both the preferred and reverse directions and are witnessed by a 3rd party approval body to give added confidence that the valve will perform as required in either flow direction.
By investing in and developing their own on-site fire test facility, Severn can understand and interpret the results to re-design & develop the fire safe valve technology for the OCT TOV Butterfly Valve, to further exceed the requirements set out in the standard. By doing this, Severn have been able to achieve up to Zero seat leakage, even after fire testing, giving further confidence to the capabilities of the valves when installed and further ensuring safety first is achieved for the end user and their operations.
The key to Severn’s success lies in their patented Oblique Cone Technology (OCT), which received approval from the UK Intellectual Property Office in 2018. This innovative design uses an ‘infinite circle’ geometry that allowed the research and development team to develop the circular sealing geometry, which gives the flexibility to use the valve for both isolation and control duties with the option of interchangeable seals and control trims.
Utilising its over 60 years of engineering heritage, Severn have designed and developed the innovative OCT TOV Butterfly Valve, a valve that meets the requirements of API 6FA, API 607, and ISO 10497 fire testing standards. These bi-directional isolation & control valves offer repeatable zero leakage, providing peace of mind for operators while ensuring safety is at the forefront.
Severn’s certification for fire test covers the OCT Laminate, Hybrid (OCT-HS) and Seawater (OCT-SW) seals, achieving the required leakage rates in accordance with the relevant international standards. By designing, developing, and testing the hybrid seal (OCT-HS) Severn have been able to understand how the hybrid polymer metallic seal acts under extreme temperatures, which has enabled them to develop a graphite free, firesafe seal, that works even after being exposed to the extremes of a fire test. By using this knowledge, the OCT-SW utilises the hybrid seal technology and prevents any graphite from contacting with the line media, therefore on seawater service eliminates galvanic effects and extends the service life of the valve.
By meeting stringent fire test standards, they have provided customers with a reliable and efficient solution to fire safety. With their patented oblique cone technology, Severn have set a new benchmark for future valve designs and innovative technology and further ensure the end user achieves its core remit of safe operations and reduced downtime.
Exploring the innovative features and engineering principles of Severn’s OCT TOV Butterfly Valve that puts safety first.
At Severn, safety is paramount in the design of our products. With our background in safety-critical industries, Severn understands the importance of safety first for both our customers and employees.
As well as adhering to the strictest industry standards, Severn have identified that shaft blowout prevention was paramount to our end users and the wider industrial and process industries for improved valve performance and reduced operational downtime.
Butterfly Valve shafts are designed to connect to the disc with either dowel pins, taper pins, or keyways. The separation of the shaft and disc in service can be catastrophically dangerous. If any of these parts fail, the shaft may be ejected from the valve body. Shaft blowouts can occur when a coupling mechanism fails, therefore, disconnecting the shaft from the disc. With the pressures in the system, it may eject the unrestrained drive shaft through either end of the valve.
Not only is this projectile a huge safety concern but has the potential to compromise the pressure envelope of the valve allowing process to escape into the atmosphere.
Severn has designed all their Triple Offset Butterfly Valves as standard with anti-blowout incorporated at both ends of the valve. This negates any chance of the shaft blowing out if the pins were to fail. The reduced shaft diameter at the drive end ensures the shaft cannot blow out through the packing follower.
On the blank end of the valve, Severn have multiple features which prevents shaft blowout. The anti-blowout ring on the threaded shaft end ensures positive engagement without the need for additional fasteners. The blank end plate is locked in place and is designed to withstand full rated test pressures.
Dual anti-blowout devices are standard on the OCT TOV Butterfly Valve, meaning that even if the gland is removed, the secondary internal anti-blowout device will stop ejection of the shaft under the pressure, thus increasing both operator and plant safety.
Severn have designed their Triple Offset Valves to exceed the minimum wall thicknesses stated in ASME B16.34. Instead of just using the minimum allowance, Severn have gone above and beyond to ensure the safety of our products in the field for our customers.
Within Severn’s Triple Offset Butterfly Valve is a corrosion allowance. This means that the valve can afford to concede material to corrosion over time without affecting the pressure containing integrity or safety of the valve. The amount of corrosion may vary depending on the environment the valve is working in, but due to Severn’s engineering heritage and excellence, the OCT TOV Butterfly Valve has been designed to withstand changes in working environments and process conditions.
High MAST figures and safety factors are key when designing the Triple Offset Butterfly Valve. MAST is the Maximum Allowable Shaft Torque a quarter turn valve shaft can withstand during operation without mechanical failure. With Severn using higher MAST figures on their Triple Offset shafts, this helps maintain the structural integrity of the valve.
Sizing actuators correctly is a credit to Severn’s engineering excellence. Actuators, gearboxes, or any form of obturator that drives a quarter turn valve must be sized correctly by using the correct input and output torques. By torque testing the physical products prior to final inspection, we can compare the physical torques against our theoretical torques to maintain accuracy and consistency across the range.
Safety has always been at the forefront of Severn’s designs, and this is paramount in the 8500 Butterfly Valve range.