Material Selection for Blind Valves Working at -40°C

This blind valve works between -40°C and 100°C. Its medium is low-temperature liquid propane plus light hydrocarbon mixtures. We need materials with good low-temperature impact resistance. Materials also need stable strength at normal temperature. They must not react with the flowing medium. Below is the full material plan.

1. Main Materials for Valve Body and Blind Plate

Common carbon steel WCB only works down to -29°C. -40°C is too cold for WCB. Casting valve bodies use ASTM A352 LCB low-temperature cast carbon steel. It passes Charpy V-notch impact test at -46°C. It fits the -40°C working condition perfectly. It keeps steady mechanical performance at 100°C. It costs less than stainless steel. If you build the valve body by welding plates: Pick Q355E high-strength low-alloy steel plates. Its longitudinal impact energy hits at least 34J at -40°C. It works well under low temperature. It is easy to weld. ASTM A516 Gr.70 normalized steel plates are another choice. Run low-temperature impact test before use. For pipe joint parts, use GB/T 6479 Q355E seamless steel tubes. Match welding fillers with low-temperature steel welding rods. Or use ER55-Ni1 welding wire. Weld seams and heat-affected zones stay tough at low temperature, same as base metal. If the medium carries tiny corrosive substances: Upgrade welded valve bodies to 304 or 304L stainless steel plates.

2.Sealing Pair Materials

This valve has two sealing parts: seat seal and blind plate seal. Regular nitrile rubber and fluororubber turn brittle at -40°C. They stop working in cold conditions. Main sealing uses all-metal hard seal design. Coat sealing surfaces with Stl 6 cobalt-based alloy. This alloy resists wear. It works across wide temperature ranges. It will not crack from cold. Auxiliary soft seals pick FFKM perfluoroelastomer. Or special low-temperature fluorosilicone rubber. Both stay flexible below -40°C. They can also stand heat up to 100°C.

3.Valve Stem and Fasteners

Valve stem material: ASTM A182 F304 stainless steel. Bolts: ASTM A320 L7 low-temperature alloy steel bolts. Nuts: A194 Gr.4 nuts. All fasteners pass low-temperature impact tests. They keep strength and toughness down to -101°C. No brittle breakage under cold conditions.

4.Other Internal Components

Guide sleeves and bushings: tin bronze or 304 stainless steel. Packing set: expanded graphite mixed with low-temperature asbestos packing. This combination seals tight in wide temperature ranges.

Summary For cast blind valve bodies under -40°C to 100°C: choose LCB steel. For welded valve bodies: choose Q355E steel plates. Match with metal hard seal sets and low-temperature fasteners. This full set meets all working requirements. It also controls overall project costs well.