Quick answer
What is the difference between soft-seated and metal-seated ball valves?
The distinction concerns the sealing interface between the ball and seat, not whether the valve body is metal. A soft-seated ball valve uses a non-metallic sealing element; a metal-seated ball valve uses metal-to-metal contact at that interface. Identify the actual construction instead of approving a quotation that says only soft seal or hard seal.
Updated: — Clarified product-link labels for seat and support comparisons; no service limits or leakage claims added.
Prepared by KEHUA VALVE for procurement review. External references explain general principles, not KEHUA product ratings or certifications. Approve the exact offered configuration against the project specification and manufacturer documents.
| Selection question | Soft-seated proposal | Metal-seated proposal |
|---|---|---|
| Sealing interface | Identify the non-metallic sealing element and exact grade. | Identify ball/seat base materials and any coating or hardfacing. |
| Temperature and pressure | Obtain limits for the specified seat and complete valve. | Check the complete valve, including packing, seals and coating. |
| Particles or abrasive duty | Require application review; fluid name alone is insufficient. | Require application-specific trim evidence; metal contact alone is insufficient. |
| Leakage acceptance | Agree the standard, conditions, direction and acceptance limit. | Agree the same items; do not assume a universal leakage class. |
| Actuation | Request torque data at the specified differential pressure. | Request torque data for the offered trim and actual duty. |
Review the sealing interface separately from ball support
Seat selection is separate from floating versus trunnion support. KEHUA lists soft-seated and metal-seated options in both families. Use the following series as candidates, then request model-specific data before deciding.
Which seat should enter your shortlist?
Start with the required shut-off duty, fluid composition, operating envelope and acceptance criteria. Emerson describes soft-seated designs for sealing duties and metal-seated designs for severe conditions; Valmet likewise relates construction choice to the process and medium. These are shortlist principles, not approval of a particular KEHUA valve.
Ask each supplier to explain why its configuration meets your duty. Record assumptions, exclusions and missing evidence. Neither a metal seat that sounds more robust nor a soft seat offered for an apparently clean fluid should bypass technical review. Compare documented proposals against the same requirements.
Check temperature, chemistry and particles together
Include normal operation, start-up, shutdown and credible upset conditions in the RFQ. Obtain the exact seat material and complete valve pressure-temperature limits. A body pressure class is not a seat-material approval; switching to metal seats does not establish limits for packing, other seals or actuation.
For fluids containing solids, describe concentration, particle size and available process data. Emerson identifies these, chemistry, pressure and temperature as slurry selection factors. Treat abrasive or slurry duty as an application review: neither a generic soft-seated nor a generic metal-seated ball valve is automatically suitable.
Metal seats: review the complete trim system
Valmet's coating bulletin explains why ball/seat contact, friction and galling matter. It also cautions that a coating cannot compensate for unsuitable base material. Use this principle to request a documented trim proposal, not to copy another manufacturer's coating specifications into your order.
Recommended questions: what are the ball and seat base materials; is coating or hardfacing included; what supports compatibility with the actual medium; and what restrictions apply? Obtain torque data for the offered configuration and agree actuator sizing responsibilities. Do not infer these details from a product photograph.
Does a seat label define the leakage class?
No seat label alone defines complete leakage acceptance. Specify the test standard and edition, medium, pressure, duration, direction, relevant temperature and acceptance limit. Distinguish the shell test from the closure or seat test. Request results tied to delivered valve identification or a documented batch scope.
Avoid unbounded terms such as zero leakage or bubble-tight. A result needs test conditions and an acceptance basis; it does not guarantee unchanged performance in every process condition. Where fire testing or fugitive-emission evidence is required, review those records and applicable scope separately.
A copyable buyer checklist for a ball valve RFQ
This is a recommended purchasing template, not a claim that every standard mandates all fields. Mark unknowns as pending and resolve engineering hold points before approval.
- Duty: isolation or another specified function, operating frequency and required closing time.
- Fluid: composition, phase, contaminants, solids concentration and particle size where relevant.
- Conditions: operating/design temperature and pressure, maximum differential pressure and transient conditions.
- Valve: size, bore, pressure designation, connection standard, floating/trunnion support and drawing requirements.
- Materials: body, ball, stem, seat element, packing, other seals and coatings; identify exact grades.
- Acceptance: standard/edition, seat configuration and direction, leakage limit and report traceability.
- Actuation: breakaway/running/closing torque, available power or air supply and sizing responsibilities.
- Offer: quantity, inspection scope, spare-seat availability, maintenance instructions, delivery and explicit deviations.
Compare KEHUA configurations before ordering
Wenzhou Kehua Valve Co., Ltd. presents soft-seated floating, metal-seated floating, soft-seated trunnion and metal-seated trunnion series on this website. Share the checklist so the team can review a candidate model and identify missing information. The family name does not replace the final datasheet.
Keep a technical deviation register. Confirm that seats, trim, tests, actuation and document scope match before comparing price. Final selection and installation requirements should be approved by the responsible project engineer.
Compare valve families
Use this guide together with the relevant valve family and project operating data.
Primary technical references
Confirm the edition required by the contract. The project specification and purchased standard remain controlling.
More technical notes