Cryogenic Pumps, Seals & Valves: Repair and Maintenance
Why Surface Finish Matters in Cryogenic Applications
Extreme cryogenic temperatures cause materials to contract and become brittle, which challenges seal integrity. Rough surfaces that seal at room temperature can develop leak paths when cooled to −196 °C. Precision lapping creates smooth, uniform surfaces that help maintain more consistent contact and evenly distribute stress. This contributes to improved sealing performance and can reduce wear in cryogenic service.
Kemet's Cryogenic Lapping Solutions
Kemet provides a process for precision diamond lapping of cryogenic valves, seals, and pump components, achieving surface finishes down to Ra 0.025 µm and flatness tolerances of 0.001 mm. Each project begins with a component evaluation to determine the appropriate lapping strategy based on material, geometry, and application requirements. Diamond compounds ranging from 0.1 to 25 microns are used, with coarser grades for controlled stock removal and progressively finer grades to produce the mirror finishes required for cryogenic sealing.
Our precision flat lapping equipment uses cast iron or composite plates filled with alumina, selected to suit the workpiece material and required finish. Plate flatness is maintained within 0.0005 mm. We can achieve surface finishes between Ra 0.025 µm and Ra 0.1 µm on valve seats and mechanical seal faces, with matched seal pairs held to parallelism within 0.0005 mm for uniform contact pressure.
For complex geometries, we offer spherical and annular groove lapping. Our automated match-lapping systems produce mated spherical surfaces for cryogenic ball valves. Specialized fixtures allow lapping of annular groove seals while maintaining the required profile and surface finish.
Kemet also supplies portable lapping kits for on-site refurbishment of valves and mechanical seals, reducing downtime by eliminating the need for full system disassembly. Supported by training, these kits enable maintenance teams to achieve quality results in the field. For unique applications, our technical laboratory provides component evaluation and process development.
Materials Expertise
Kemet has experience lapping materials used in cryogenic service, with processes developed for each material family to achieve the surface finish and flatness required for low temperature applications.
Stainless Steel (300 Series)
Grades 304, 316, and 347 are widely used in cryogenic valves. Our lapping processes produce mirror finishes while controlling work hardening to maintain surface integrity.
Tungsten Carbide
Commonly used for mechanical seal faces, tungsten carbide's hardness requires diamond lapping to achieve cryogenic-quality finishes. We tailor our processes for straight, nickel-bonded, and cobalt-bonded carbides, achieving surface finishes in the Ra 0.025–0.05 µm range.
Silicon Carbide
Both reaction-bonded and sintered silicon carbide are lapped using controlled parameters. Specialized diamond compounds and techniques produce quality sealing surfaces despite the material's hardness and brittleness.
Stellite and Hard-Faced Components
Valve seats with Stellite 6 or 12 hard-facing require careful lapping to remove the rough overlay finish while preserving seal geometry. Our processes create precision sealing surfaces without edge rounding or distortion.
Advanced Ceramics
Alumina, zirconia, and silicon nitride seal faces are lapped using fine diamond compounds and specialized plates to achieve high flatness and surface quality. Carefully sequenced processes help prevent microcracking while delivering consistent results.
PTFE and Composite Materials
For soft materials such as PTFE and filled PTFE, light lapping can improve surface uniformity and sealing performance without damaging the polymer structure.
Common Cryogenic Components We Process
Ball Valve Seats and Seals
LNG ball valves require spherical seats to maintain sealing under temperature cycling. Our KemTech SpheriMatch II system produces matched ball and seat assemblies. The lapping process creates a spherical radius on both the ball and the seat for contact around the full sealing circumference.
Gate Valve Sealing Surfaces
Gate valve seats used in liquid oxygen, nitrogen, and argon service require both flatness and surface finish precision. We process valve discs and seats for metal-to-metal sealing capability at cryogenic temperatures. Our flat lapping process maintains flatness within 0.001mm while achieving Ra 0.05µm surface finish.
Mechanical Seal Faces
Cryogenic pump mechanical seals demand high surface quality. We lap both rotating and stationary seal faces to matched specifications. The faces are finished flat and parallel to within 0.0005mm to help ensure uniform face contact pressure. Our matched lapping process creates seal face pairs with improved sealing performance.
Check Valve Components
Spring-loaded check valves in cryogenic transfer systems require precision-lapped seats to prevent backflow. Our processes help ensure consistent sealing performance. Check valves experience repeated impacts as they open and close. A precision-lapped surface helps the valve withstand operational cycles, and the improved surface finish helps distribute contact stress more uniformly.
Relief Valve Seats
Safety relief valves protecting cryogenic vessels and piping must reseat after discharge. We lap both the valve disc and seat to help ensure reliable resealing at cryogenic temperatures. The precision sealing surfaces we create support the proper function of these safety devices. We've processed relief valve components for LNG facilities, liquid hydrogen systems, and liquid oxygen plants.
Why Choose Kemet for Cryogenic Applications?
With over 85 years in precision lapping, we've processed components for a wide range of applications. Our customer list includes global energy companies, industrial gas producers, aerospace manufacturers, research institutions, and valve manufacturers. When you work with Kemet, you benefit from accumulated knowledge and proven processes. Our team understand the challenges of cryogenic sealing and can recommend appropriate approaches for your specific components.
With distributors worldwide and portable equipment available for rental or purchase, we can support your operations in many locations. We ship equipment and consumables globally and provide technical support. For projects requiring on-site assistance, we can arrange training and commissioning support at your facility. From equipment and consumables to training and refurbishment services, Kemet provides lapping solutions for cryogenic applications.
