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Sep. 28,2026
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Pipeline owners often face the same problem: a valve that passes a factory pressure test can still create installation delays, coating failures, difficult maintenance, or leakage risk in the field. A fully welded ball valve for pipeline projects can reduce external leakage paths because the body is welded rather than assembled with a bolted body joint, but only when its bore, materials, end connections, actuation, coating, and test records match the pipeline design. This checklist helps engineers, procurement teams, and contractors choose a pipeline isolation valve for aboveground, buried, gas, liquid, or sour-service applications and avoid paying for an unsuitable buried service ball valve.
A welded-body construction removes the conventional bolted body joint from the pressure boundary. This can be useful where the valve will be buried, exposed to weather, installed in a restricted right of way, or subjected to repeated pressure and temperature changes. It does not mean that every welded-body valve is automatically safer or maintenance-free. The pressure boundary, stem sealing system, seat design, weld quality, coating, and field-weld procedure still determine performance.
For a gas transmission or liquid pipeline, the buyer should define the valve as part of the complete piping system rather than as an isolated catalog item. ISO 14313, Petroleum and natural gas industries - Pipeline transportation systems - Pipeline valves, provides requirements for pipeline valves, while API Specification 6D is widely used for pipeline valve design, manufacturing, inspection, and testing. ASME B16.34 is commonly referenced for valve pressure-temperature ratings, materials, and design requirements. The project specification should state which standard governs when requirements differ.
Start with operating conditions, not the nominal pipe size. Record the fluid, normal pressure, maximum and minimum design pressure, normal and design temperature, flow direction, shutoff frequency, pressure-drop limit, installation elevation, and expected service life.
For buried installations, specify the depth of cover, soil conditions, groundwater exposure, cathodic protection arrangement, stem-extension length, access-box requirements, and field-joint coating system. A surface coating designed for aboveground ultraviolet exposure is not automatically suitable for permanent soil contact.
Specify nominal pipe size and the required internal bore separately. A full-bore ball valve is often selected in lines that require pipeline inspection gauges or cleaning pigs, but the valve should be checked against the actual pig geometry. Confirm bore diameter, bore transitions, seat-pocket profile, internal weld protrusion, and allowable misalignment with the pipeline operator and pig supplier.
Reduced-bore construction may be acceptable where pressure drop, pigging, or solids handling does not control the design. It can reduce valve size, mass, and cost, but it must not be selected solely from a general catalog description.
End connections should match the pipeline welding procedure and the applicable dimensional standard. Define one of the following where appropriate:
For butt-welded valves, ask the supplier for the weld-end material, chemistry, wall thickness, bevel dimensions, allowable preheat, interpass temperature limits, post-weld heat-treatment requirements, and minimum distance between the valve body weld and the valve internals. The final field-weld procedure remains the responsibility of the pipeline contractor and must be qualified for the actual pipe and valve materials.
Do not specify only a nominal pressure such as class 600 without checking temperature derating and material group. Pressure class is not the same as a guaranteed operating pressure at every temperature. The purchase specification should require a pressure-temperature rating table for the complete valve, including body, seats, seals, and end connections.
State the design pressure and test pressure in the data sheet, then identify the governing standard. API 6D and ISO 14313 contain pipeline valve requirements, while ASME B16.34 is used for pressure-temperature ratings and related valve requirements. The manufacturer should confirm that the selected body material and trim combination is within the applicable rating at the minimum and maximum design temperatures.
Also request the allowable pressure differential for opening and closing. A ball valve may have a suitable body rating but still need a specific actuator torque or pressure-balancing arrangement to operate at maximum differential pressure.
Material selection should be based on fluid chemistry, temperature, pressure, corrosion mechanism, weldability, and sour-service requirements. A typical carbon-steel pipeline body may be suitable for many hydrocarbon services, but the exact grade, toughness, weldability, and impact-test requirements must be specified by the project.
Ask for the following information:
For hydrogen sulfide or other sour environments, specify NACE MR0175 or ISO 15156 as applicable to the production environment. These standards address material selection and qualification for cracking resistance in hydrogen-sulfide-containing environments; they do not replace the project fluid analysis or corrosion assessment. Provide the supplier with hydrogen sulfide partial pressure, chloride level, pH, water content, temperature, pressure, and expected exposure conditions.
Seat selection should reflect the medium, temperature, solids, pressure direction, fire risk, and required shutoff class. Common seat materials include reinforced PTFE, nylon, PEEK, and other engineered polymers, but their pressure and temperature limits vary by formulation and design.
Define whether the valve requires soft seats, metal-seated construction, or a combination. For clean gas and liquid pipelines, soft seats may provide tight shutoff within their rated range. For abrasive service, high temperature, or severe contamination, a metal-seated design may be more appropriate, although it requires careful control of ball and seat finish, clearances, and test acceptance.
Specify seat leakage acceptance according to the governing standard and project requirement. API 6D and ISO 14313 include valve testing requirements, but the purchase order should still identify the test medium, test duration, pressure, allowable leakage, test direction, and whether low-pressure gas testing is required.
Ask whether the design provides single piston effect or double piston effect seating, automatic cavity pressure relief, cavity drain, and sealant injection. These functions affect pressure management and maintenance. Do not assume that a double piston effect seat means the valve provides double block and bleed; the project specification must define the required isolation function and verification method.
The stem is a dynamic penetration through the pressure boundary, so stem sealing deserves the same attention as the body. Specify the number and type of stem seals, anti-blowout construction, emergency sealant injection, stem bearing materials, and allowable operating cycles.
Where the pipeline carries volatile organic compounds or toxic gas, include a fugitive-emissions requirement. ISO 15848-1 provides a classification and test system for fugitive emissions from industrial valves. The purchase specification should state the test temperature, number of mechanical cycles, leakage class, and whether the requirement applies to the complete valve and actuator assembly or only the valve.
Emergency sealant injection can help control leakage after seal wear, but it is not a substitute for correct seal design. Define injection-port material, connection size, check-valve arrangement, compatible sealant, and safe access position.
Actuator sizing must use the worst-case torque or thrust across the full operating range, including maximum differential pressure, low temperature, seat friction, packing friction, deposits, and an agreed safety factor. The supplier should submit a torque calculation rather than selecting an actuator from valve size alone.
Define:
For emergency shutdown or pipeline sectionalizing service, perform a dynamic hydraulic review before setting the actuator speed. A faster closure is not automatically better; it can increase transient pressure and cause an avoidable surge event.
If the valve is installed in a hydrocarbon or other fire-risk service, specify fire testing according to the project standard. API 6FA is a commonly referenced fire-test standard for valves, while API 607 applies to certain soft-seated quarter-turn and other valve designs within its scope. The buyer should confirm the applicable standard with the owner and regulator because fire-test applicability depends on valve design and service.
Also define anti-static continuity, electrical grounding, cavity pressure relief, anti-blowout stem design, and external fire exposure assumptions. These features should be supported by design documentation and inspection records, not only by a marketing statement.
External coating is a major factor in the service life of a buried service ball valve. State the coating system, surface preparation, dry-film thickness, holiday-test voltage, adhesion requirement, repair procedure, and inspection standard. The coating must be compatible with soil, groundwater, cathodic protection, field-joint coating, and installation handling.
For buried valves, include protective measures for the stem extension, drain and vent piping, actuator support, lifting points, and access box. Request coating inspection reports and repair records. A valve body with a good factory coating can still fail prematurely if lifting chains damage the coating or if the field joint is not repaired correctly.
A reliable purchase order identifies hold points, witness points, review documents, acceptance criteria, and the responsible party. The inspection and test plan may include:
Factory acceptance testing should record valve serial number, body heat number, test medium, test pressure, test duration, leakage result, actuator settings, opening and closing time, and any corrective action. Generic certificates without traceability to the supplied valve should not be accepted as a substitute for a project dossier.
Why: A supplier cannot correctly size the valve, seat, body, or actuator from line size and pressure class alone.
How: Issue a data sheet containing fluid composition, design pressure, temperature range, pipe wall thickness, bore requirement, operating frequency, installation location, pigging requirement, emission limit, actuator function, and applicable standards. Mark unknown values as pending rather than allowing the supplier to make undocumented assumptions.
Best for: New pipeline projects, EPC packages, and procurement teams comparing multiple manufacturers.
Why: Mixing essential safety requirements with optional conveniences makes technical bid evaluation inconsistent and can increase cost without improving risk control.
How: Divide the specification into mandatory compliance items, scored technical preferences, and optional alternatives. Treat pressure rating, material compatibility, fire safety, sour-service compliance, testing, and end dimensions as mandatory where the design requires them. Treat drain arrangements, special coatings, and online diagnostics as project-specific options.
Best for: Competitive tenders and projects where several valve sizes or service classes are purchased together.
Why: A valve described as full bore may still be unsuitable for a particular cleaning or inspection pig because of bore transitions, seat pockets, or internal geometry.
How: Request certified dimensional drawings showing the minimum bore, transition angles, internal weld profile, face-to-face length, weld-end details, and valve orientation. Compare these dimensions with the pig manufacturer's clearance requirements and the pipeline alignment drawings.
Best for: Gas transmission lines, crude-oil lines, product pipelines, and any system using regular pigging.
Why: Traceable records reduce the risk of receiving a valve with the wrong material grade, incomplete testing, or documentation that cannot support commissioning and future maintenance.
How: Require a manufacturing data book index before production. Match the valve serial number with material certificates, weld maps, non-destructive examination reports, pressure-test charts, actuator test records, coating reports, calibration certificates, and final inspection release notes.
Best for: Regulated pipelines, sour-service systems, high-consequence areas, and projects with strict turnover documentation.
Why: A lower purchase price can be offset by field-weld modifications, actuator changes, coating repairs, special lifting equipment, or missing documents.
How: Compare valve price, actuator and control accessories, transportation weight, welding preparation, coating system, inspection, spare parts, commissioning support, training, warranty, and lead time. Ask each bidder to identify exclusions and deviations in a compliance matrix.
Best for: Long-distance pipelines, remote sites, buried valves, and projects with limited access after installation.
When evaluating Yongsheng or any other manufacturer, review evidence in the same order that the valve will be used in the project. First, confirm the product design against API 6D or ISO 14313 and the project pressure-temperature requirements. Next, check manufacturing capability for body welding, heat treatment, machining, non-destructive examination, coating, and actuator assembly. Finally, review the supplier's quality system, test equipment calibration, traceability process, spare-parts support, and record of delivering valves for comparable pressure, size, temperature, and fluid conditions.
Request a technical offer that includes a compliance statement, marked-up data sheet, general arrangement drawing, cross-section drawing, material list, pressure-temperature table, actuator sizing calculation, inspection and test plan, quality certificates, proposed delivery schedule, spare-parts list, and deviation list. If the supplier cannot identify a deviation clearly, the bid should not be treated as fully compliant.
These two values do not define fluid compatibility, seat performance, actuator torque, buried-service protection, or pigging suitability.
The actual internal geometry must be compared with the selected pig. Obtain drawings and written confirmation rather than relying on the product name.
NACE MR0175 and ISO 15156 material decisions depend on the service environment. Provide the relevant hydrogen sulfide, chloride, water, pH, pressure, and temperature information.
Confirm that the tested design, seat material, size range, pressure class, and sealing arrangement correspond to the supplied valve.
Weld-end dimensions, material chemistry, heat input, preheat, post-weld heat treatment, and coating repair must be coordinated before the valve reaches the site.
Before approving the purchase, confirm that the valve has a defined service envelope, documented pressure-temperature rating, correct bore and end connections, compatible body and trim materials, suitable seats and stem seals, correctly sized actuation, required fire and emission performance, coating suitable for the installation environment, and a traceable inspection dossier.
The most effective procurement process is not simply choosing the lowest quoted price. It is matching the valve design to the pipeline duty, checking the evidence behind each compliance claim, and controlling the interface between the valve, field weld, actuator, coating, pigging system, and commissioning plan. Whether the selected supplier is Yongsheng or another qualified manufacturer, this approach gives project teams a clearer technical comparison and reduces avoidable site work, documentation gaps, and premature leakage risk.
Use this checklist when learning how to specify a fully welded ball valve, especially for a fully welded ball valve for buried pipeline service. Pay particular attention to pigging, double block and bleed requirements, pressure-temperature rating, and fugitive emissions because these professional terms describe functions that must be verified by drawings, calculations, and test records rather than assumed from a product label.
The technical guidance in this article is aligned with the published scopes and commonly used requirements of API Specification 6D, ISO 14313, ASME B16.34, NACE MR0175 and ISO 15156, ISO 15848-1, API 6FA, API 607, and EN 10204. The project engineer should obtain the current editions and confirm contractual applicability before issuing a purchase order, because standard editions, owner specifications, and local regulations can impose additional requirements.
