Applications
Cryogenics is the branch of physics dealing with processes and materials at very low temperatures normally below -101°C. The need to handle low-temperature liquids and gases has become a commonplace requirement with fluids such as oxygen, liquid hydrogen and nitrogen. Valves that can provide tight shut off for isolation or modulation for control requirements at temperatures down to -196°C are now an essential part of today's process plant.

Design
Valve designs of lightweight construction are advantageous for cryogenic use since the valve mass which must be cooled down from ambient to cryogenic temperatures on start up is much reduced. In addition the lower conductivity of lighter weight valves will assist in reducing heat influx which can occur in heavier design styles of valve.

Solent & Pratt's design team have paid particuler attention to these basic design principles in the product suitability of our cryogenic range of valves.

The Solent & Pratt TOSV, Triple Offset Segment Valve with its long life, high integrity on thermal cycling and low operating torques is an ideal valve for cryogenic applications.

The Solent & Pratt cryogenic TOSV utilises the well established, patented, triple offset segment valve geometry together with the field replaceable seat and seal rings. The shaft is offset from the body in two directions and whilst the disc is a segment taken from a cone where the apex is offset from the centre line of the valve. The result is that no interference (rubbing) occurs between the disc (segment) and the seat ensuring bi-directional tightness and long valve life.

Key Features

Cryogenically tested T o BS 6364 in both directions Metal/metal sealing Iinherently firesafe Zero leakage shut off Available in both directions Seat & Seal Replaceable body seat and metal laminate disc seal Triple offset design Nnon rubbing Anti-blowout stem As standard to API 609 cat B NACE Req Materials of construction available to NACE requirements Butt Welds & Top Entry Wafer lugged, double flanged, butt weld ends and top entry body designs available ANSI Specs: 3" to 88" in ANSI 150, 300, 600, 900 and 1500lb designs with fully rated trims. Larger sizes available on request Temperature Temperature range to -196°C Patents UK and foreign patents issued. Quality assurance system approved to ISO 9001. Technical Description SOLENT & PRATT, TOSV series valves are of dedicated Triple Offset geometry design. This particular feature eliminates the disc-to-seat rubbing condition, normally associated with 'HPBV' butterfly valves, which induces wear of varying degrees, even in metal seated versions. The standard valve construction has been developed and modified to create the Double Block and Bleed Valve. In the Double flanged body version it utilises the same face to face length casting , enabling a standard TOSV to be replaced by a TOSV - DBB with out alteration to the pipework. The advantages of using this innovative Butterfly Valve design rather than the use of a conventional ball valve is weight and space saving in addition to obvious economies in terms of cost. To create this design feature, it was necessary to provide a gallery into which any fluid which passed the seals would drain. This gallery, of annular form, was created by using two seals with an interposed spacing ring, allowing for fluid leak-off to pass via the interconnecting body port to a manual valve or other auto relief device. This facility allows checks to be carried out on the seat / seal integrity. The trims are all fully rated in pressure ranges from 150# to 1500#, making it an ideal PROCESS VALVE which is inherently FIRESAFE, having no soft components in it's construction. To summarise, this is an ideal replacement valve for Ball, Plug or Gate types, since it offers: Seat tightness - Zero leakage Non - jamming seat design Control & Isolation use Weight savings Easily maintained ** ** Both Seat and Seal are field replaceable Principal of Operation Cryogenic valves are easily recognisable by their long extension bonnets. The extension should protrude for at least 6" beyond any lagging on the pipework to assist a 'boil off' to occur within the bonnet extension. In order for this to occur the valve must always be installed with its extension at an angle of not less than 20° from the horizontal. The vapour pocket which results from the 'boil off' within the extension will prevent the cold media from contacting and freezing the valve stem seals in the packing gland. Materials Materials of construction are an important issue for cryogenic valve applications. The Solent & Pratt valve is available in: ASTM A351 CF8M Duplex stainless steels 6 MO stainless steel Bronze Monel Incoloy Hastelloy B & C Zirconium Aluminium Other materials available on request.

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