Emerson’s Andrea Sutti presented Cryogenic Valve Designs to Meet Demand for Higher Capacity, Emission Compliant LNG Infrastructure at the 2024 Emerson Exchange Conference in Düsseldorf, Germany. Here is his presentation abstract:
LNG demand is forecast to grow due to its role in global energy security and its part in the journey to net zero as a cleaner transitional fossil fuel. This is triggering the construction of liquefaction trains with significantly larger capacity, operating at higher pressures to generate higher outputs. Producers aiming to meet future LNG demand must exhibit robust sustainability credentials, with valve technology being a key area to enhance sustainable performance. As the primary source of fugitive emissions in facilities, valves will face increased scrutiny. Discover how advanced valve technology can overcome this obstacle, boost process efficiency, ensure compliance and safety, and reduce operating costs.
Vanessa TOV 72″ Class 300 Cryogenic Testing
Andrea opened by describing the LNG process which begins with natural gas liquifying at approximately -162°C, reducing its volume by 600 times. It is suitable for easier, safer storage and shipping overseas while natural gas needs huge pipeline infrastructure. LNG is transported by truck or by LNG carriers in thermally insulated tanks to the receiving terminal where is temporarily stored before being re-gasified. Once, re-gasified, the natural gas is used to supply the gas pipeline network for households, as fuel for ships and for road transport.
The LNG production process includes water & condensate removal, acid gas (H2S, CO2) removal, dehydration to remove other remaining impurities, and mercury removal. Once the natural is purified, it is pre-cooled for heavy natural gas liquids removal and then liquefied and stored before shipping.
Some of the challenges in the LNG industry include the severity of cryogenic conditions and potential troubles during plant commissioning. The valve under these conditions may experience issues with seal tightness, fugitive emissions, operability, and installation & maintenance costs.
Traditional rising stem isolation valves have issues in containing fugitive emissions with the linear rising stem movement that tends to extrude the packing and bring dirt and particles inline. Fluctuating temperatures may also affect tight shutoff and increase the risk of jamming.
Conventional ball valves have design limitations for this application. In a floating ball valve, the ball is held between two seats and compressed by them. Performance and reliability are extremely limited. For a trunnion-mounted ball valve, the ball is supported by a trunnion (and not the valve seats) which allows much higher pressure and temperature ratings. They rely on polymeric lip-seals invalidating the inherently fire safety. Polymeric materials are subject to relevant contractions at cryogenic temperatures, negatively affecting the valve sealing performances.
Traditional ball and gate valves generate high total installation cost (due to their large footprint, heavy weight and high torque actuation required) and significant maintenance cost as well. A gate valve requires larger distance between packing and actuation and features extra space in the body to accommodate the wedge when the valve is open. They are comparatively more expensive than Triple Offset Valves on bigger diameters with larger weight and footprint.
The Vanessa Triple Offset Valve (TOV) was the first to provide bidirectional zero leakage performance, creating a new industry category using a technology not previously available with other quarter turn valves.
It’s available with universal cryogenic trim for a variety of piping connections with a solid seal ring in Nitronic 50 and an integral body seat overlayed with Stellite 21. No rubbing rotation and metal to metal torque seating ensure the operability & tightness remain unaffected by cryogenic temperatures.
The Vanessa Series 30,000 Triple Offset Valve meets the needs for LNG producers, including:
The LNG industry is progressively moving away from traditional gate and ball valves to TOV to fulfill increasingly challenging needs.
Unlike ball valves, the Vanessa Series 30,000 TOV is cavity-free eliminating cavity related risks and limitations.
While traditional valves have difficulty sealing at low temperature due to differentials of contraction and materials losing sealing ability, the Vanessa TOV with integral seat, non-rubbing design and metal to metal torque seating, offers long lasting tight shutoff at cryogenic temperatures.
From a fugitive emissions perspective, losses of raising stem valves can be significantly reduced by switching to quarter turn designs. Piping connections on valves represent another relevant source of fugitive emissions. These emissions can be eliminated by specifying a buttweld valve body design.
The Vanessa Series 30,000 TOV minimizes the risk of external emissions with its quarter-turn rotation and a two-piece packing gland solution.
The LNG industry has been increasingly turning to triple offset design for Safety Integrity Level 3 and higher applications, in view of the intrinsic advantages derived by its asymmetric geometry and its quick and easy operation over time. The asymmetry of the TOV design triggers different behavior depending on the installation. This increases the reliability of the valve when actuation fails. TOV is increasingly being selected to handle several functions within emergency systems.
From an installation and maintenance perspective, TOVs are significantly lighter than comparable ball and gate valves (for medium and large sizes) due to lower material use. They also feature significantly more compact valve bodies, which positively affects the overall plant design. They are unaffected by piping loads with no need for external supports. The non-rubbing rotation, metal-to-metal and torque seating reduce the need for actuation and make Vanessa Series 30,000 TOV virtually maintenance free for cryogenic LNG applications.
Visit the Vanessa valve section on Emerson.com for more on these valves as a solution for cryogenic and other demanding applications.
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