Scott Moreland, QUADAX Valves, USA, outlines the design considerations of valves to be used in applications with extreme temperature requirements.
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s most piping specialists know, LNG applications can be very difficult to control flow, and it takes a special design with specific materials to work in temperatures ranging down to -454˚F/-270˚C. A design and materials which cannot be utilised in most valve types. While both gate valve and ball valve designs have been utilised, they do not always provide the very best of results – zero leakage in on/off applications. Even most triple offset valves will not allow for zero leakage, due to the elliptical design of the port and sealing areas being most difficult to hold the most stringent sealing. That, coupled with fabricated designs which will be made worse whenever there is any deflection of sealing surfaces caused by pinned disc or inferior stem designs, mean there can be a very small window where a valve can seal perfectly. A four offset design valve allowing for a circular sealing surface, along with very low friction on the seals, will comply with the desired effect of allowing for zero leakage at low temperatures. This is true especially after a high number of cycles at very low temperatures while most other TOV’s have begun a process of increasingly leaking beyond acceptable levels. As a result of a four offset construction and state of the art manufacturing technology, QUADAX® Valves are designed to offer 100% compliance even with the highest tightness and extreme temperature requirements. Now take those extreme applications and add the requirement to the reliability of functioning time and again sporadically in the unique application of refuelling a rocket with LNG/liquid hydrogen in less-than-ideal weather conditions, i.e. coastal locations. The frequency of the loading at the very low temperatures, the rough handling of the equipment given the surroundings and circumstances of quickly turning on/off the process, along with the outside temperatures and corrosive atmosphere of the coastal locations for launching pads, all give rise to very extreme conditions in which a valve has to operate without failing time and time again – high cycling. The leading aerospace companies in the US have found a strong business partner for their valve requirements and therefore the solution to maintaining zero leakage on/off operation in QUADAX Valves.
Figure 1. US aerospace group launching latest rocket with payload.
Space travel In order to meet the constantly growing demand for the economic transportation of medium and heavier satellites for civilian purposes, the launching stations for orbital missiles are 29
