WCB vs LCB vs WC6 valve materials: selection guide
WCB, LCB and WC6 are pressure-containing casting grades with different strengths. A material choice should follow the minimum and maximum design temperature, pressure-temperature rating, process fluid, welding plan and project material specification.
TAZ Engineering & Export Team · · 10 min
Use WCB for defined carbon-steel service
WCB is widely specified for general carbon-steel valve bodies where the applicable standard and pressure-temperature rating cover the design case. It is not a universal answer for low-temperature impact duty or elevated-temperature alloy service.
Confirm the material specification edition, heat treatment, chemistry and mechanical results. The valve rating, trim, bolting, packing and gaskets must also suit the same pressure and temperature envelope.
Use LCB when low-temperature toughness governs
LCB is selected where low-temperature service requires controlled toughness. The purchase specification should state the minimum design metal temperature, impact-test temperature, specimen requirements and acceptance criteria.
A low-temperature body does not make the complete valve suitable by itself. Bonnet, closure member, stem, bolting, welds, seals, lubricant and actuator components need compatible limits.
Use WC6 for applicable elevated-temperature duty
WC6 is a chromium-molybdenum alloy steel casting used in suitable elevated-temperature services. Selection depends on the governing code, material group and pressure-temperature table rather than a generic steam label.
Control heat treatment, weld procedures, preheat or post-weld heat treatment where applicable, hardness and repair records. Review thermal cycling and oxidation together with mechanical strength.
Compare the whole valve configuration
Build a material schedule for body, bonnet, wedge or disc, seats, stem, bolting, packing and gaskets. Check galvanic compatibility, corrosion allowance, erosion, process contamination and maintenance practice.
For replacement work, verify flange standard, face-to-face dimension and rating. Similar body dimensions do not establish material or operating equivalence.
Make the purchase record auditable
State grade, product form, standard, impact requirements, heat treatment, NDE, repair restrictions and certificate type in the datasheet. Map heat or cast numbers to the delivered serial numbers.
Close any proposed substitution through a documented deviation. The supplier should show the applicable rating and test route for the final material and valve design.
Checklist
- minimum and maximum design temperature
- design pressure and rating standard
- body and bonnet grade
- impact-test requirements
- heat treatment
- welding and repair controls
- trim, bolting and sealing materials
- material certificates
- heat-to-serial traceability
- approved substitutions