Since the late 1950s, STÖHR ARMATUREN has specialized in the development and manufacture of fittings for gases at cryogenic temperatures for applications in predominantly five areas: industrial gases, aerospace, chemical industry, ship technology and science.
It is not just the low temperatures of 2 K or below of liquid helium that place high demands on the materials: design requirements, high quality in production, quality assurance and acceptance tests must also be mastered - no helium user understandably wants to waste this rare and expensive gas or unnecessarily add heat to the gas, which had artificially been liquefied before with high technical complexity and at high cost.
Valves from STÖHR ARMATUREN prevent the loss of expensive noble gases due to extreme tightness to the outside. Go and convince yourself!
We master high tightness and minimised heat loads
Only valve sealing by means of bellows guarantees a very high level of tightness. Bellow sealed valves achieve helium tightness to environment of 1x10E-8 mbar*l / sec and higher which corresponds to a gas loss of less than one cubic centimeter over a period of three years. The bellow is welded on both sides: downwards with the valve spindle, upwards with a cover plate and thus forms the first spindle seal. An additional seal, e.g. by means of a metal ring, the so-called second spindle seal, ensures maximum tightness even in the event of a fault, e.g. in case of bellows breakage.
At a temperature of 4K or below, working with liquid helium requires the correct use of the appropriate housing material: STÖHR only uses solid stainless steel to prevent cold leaks as well as suitable sealing material that is required to achieve tightness in cryogenic use at valve seat. We offer spindle extension for thermal decoupling to prevent the actuator from freezing and the resulting malfunction, while a vacuum housing with multi-layer insulation and a stable and high-quality vacuum prevent heat from entering into the medium.
The heat input is additionally minimized by the suitable valve body design by avoiding unnecessary mass, but at the same time all standards and regulations are being observed. The heat absorption induced by the actuator downwards into the medium via the valve spindle can be kept as low as possible by various design measures: the transfer of thermal energy from the metal spindle to the valve's outer tube by means of thermal sliding contacts, while a copper flange between the outer tube and the vacuum housing ensures the subsequent heat transfer. Convective heat absorption inside the spindle tube can e.g. can be prevented by filling with perlite powder. Non-metallic spindle material also reduces heat absorption due to its lower thermal conductivity.
STÖHR ARMATUREN optimizes effort and costs for an efficient medium transport from the storage container to the place of consumption.
We master flow coefficiency
High values for the flow coefficient (KVS) which indicate an optimized media flow also indirectly contribute to reducing the heat input into the medium. The higher the flow coefficient of a valve, the smaller ceteris paribus the required nominal size can be choosen, and thus the mass of the valve body and the associated heat input can be minimized.
Precise flow control results primarily from the design of a long valve lift of the cone between the closed and fully-open positions. Depending on the required control characteristic, different valve cones with equal percentage or linear characteristics are being offered. For this reason we provide a wide range of plug types and various control characteristica for each nominal diameter to meet the high requirements of our customers.
Series 1600 recently developed by STÖHR ARMATUREN is especially designed for use with liquid helium and fulfills all the requirements described above which the medium and its application place on a high-end valve!
STÖHR ARMATUREN – best for Helium