The main material of ZECO cryogenic gate valve is selected. Considering from the metallographic aspect, in addition to austenitic steel, copper and aluminum with face centered cubic lattice, general steel will appear low temperature brittleness at low temperature, thus reducing the strength and service life of the valve. When the temperature is higher than -100℃, choose ferritic steel; when the temperature is lower than -100℃, choose austenitic steel; low pressure and small diameter valves can choose copper and aluminum and other materials. Stem and fastener is selected, when the temperature is higher than -100℃, stem and bolt materials adopt Ni, Cr-Mo alloy steel, through appropriate heat treatment, to improve tensile strength and prevent thread bite. Austenitic stainless steel is used when the temperature is higher than -100℃. Low hardness of 18-8 acid resistant steel will cause mutual abrasion between stem and packing, causing leakage of packing.Therefore, the stem surface must be hard chrome plated (thickness 0.04-0.06mm), or nitride and nickel-phosphorous plated to improve surface hardness.In order to prevent nuts and bolts from biting to death, the nuts are generally made of Mo steel or Ni steel and coated with molybdenum disulfide on the surface of the threads.
1. The valve body of ZECO cryogenic gate valve is able to withstand expansion and contraction due to temperature changes without permanent deformation of the seat structure due to temperature changes;
2. The bonnet of ZECO cryogenic gate valve is constructed with a long neck bonnet to protect the stuffing box.The long neck bonnet design also facilitates winding of cooling material;
3. ZECO cryogenic gate valve uses flexible wedge or open wedge. These structures maintain a reliable seal regardless of temperature;
4. The low temperature properties of the material, such as compression resilience, tightening force, tightening pressure distribution and stress relaxation, are taken into account.
ASTM A350 LF3
ASTM A276 410 + STL
ASTM A350 LF3 + STL
ASTM A182 F6
Graphite + SS316
ASTM A193 B16
ASTM A194 4
ASTM A350 LF3
ASTM A182 410