Due to the elliptical design of the port and sealing areas being most difficult to hold the most stringent sealing, even most triple offset valves will not allow for zero leakage. 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, means there can be a very small window where a valve can seal perfectly. A quadruple (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 TOVs have begun a process of increasingly leaking beyond acceptable levels. A four offset construction and state of the art manufacturing technology has resulted in a design which offers 100% compliance even with the highest tightness and extreme temperature requirements.
Have you read this Valve World Americas article yet? Read it here.