Frequently Asked Questions

A full bore valve matches the ball bore to the pipeline ID, giving near-zero pressure loss, pigging capability and passage for inline inspection tools, but it is larger, more expensive and needs higher operating torque. A reduced bore valve steps down one size, reducing weight, cost and torque, but introduces pressure loss and prevents pigging. Valve stations on long-distance pipelines, pig launching/receiving and pigging stations must use full bore (also a common API 6D pipeline valve requirement); reduced bore is acceptable for general isolation where space and budget are constrained. When both are mixed in one system, calculate the pressure loss and flow velocity at the reduced-bore section.

Decide by temperature, medium and fire-safety requirements. For clean media, temperatures ≤200℃ and zero-leakage duty (ISO 5208 Rate A), choose a soft seat (EPDM/PTFE/PEEK): cost-effective and suitable for water treatment, HVAC and general chemical service. For temperatures >200℃, abrasive particle-laden media, fire-risk areas or long service life, choose a triple-offset metal seat: the leakage class is typically Rate C/D, but the metal secondary seal provides inherent fire-safe behaviour (API 607). Provide the medium, temperature and required leakage class, and we will give a specific recommendation.

Select materials per NACE MR0175 / ISO 15156. Carbon and low-alloy steels require controlled hardness and heat treatment; stems and trim are typically sour-service stainless steel or duplex. Bolting should be A193 B7M / A194 2HM (not standard B7/2H). Materials must undergo hardness testing and batch material verification (PMI), and NACE-compliant material certificates must be requested with the shipment. Specific steel grades and maximum hardness must be assessed against H₂S partial pressure, pH and temperature; we can provide a sour-service material selection proposal based on the operating conditions.

NPT (US tapered pipe thread, 60° thread angle) and BSP (British pipe thread, 55°, including BSPT tapered and BSPP parallel threads) differ in thread angle and pitch and are not interchangeable. North American projects commonly use NPT; European and Commonwealth markets use BSP. Choosing the wrong one leads to field assembly failure or leakage. State the thread standard in the RFQ and specify the sealing method: tapered threads seal on the thread itself, while parallel threads require a gasket or sealing face.

Choose by pressure class and medium hazard. RF (raised face) with spiral-wound gaskets suits Class 150/300 and general service; RTJ (ring joint) uses a metal ring gasket for hard sealing and suits Class 900 and above, high pressure and high temperature and flammable or explosive media, with higher reliability. Flange standards follow ASME B16.5/B16.47 or EN 1092-1. RF and RTJ are different sealing-face forms and must not be mixed or interchanged.

DBB (double block and bleed) means the valve has two independently sealing seats with a bleedable cavity, used where the cavity must be drained or sampled. DIB (double isolation and bleed) is more stringent, with two independent isolation functions, available in bidirectional (DIB-1) and unidirectional (DIB-2) versions. Both share the same bleed function; the difference lies in the independence of isolation and the sealing direction. DIB is used for strict isolation of high-pressure or hazardous media.

They correspond nominally but are not interchangeable (per EN 1759-1). Nominally, Class 150≈PN20, 300≈PN50, 400≈PN68, 600≈PN110, 900≈PN150, 1500≈PN260 and 2500≈PN420. The conversion is approximate only; the actual allowable pressure must be taken from the pressure-temperature rating tables — the same Class has different allowable pressures at different materials and temperatures. Selection should follow the ASME B16.34 pressure-temperature ratings and must not simply apply the nominal values.

API 6D (identical to ISO 14313) covers ball, gate, check and plug valves for pipelines and piping systems, including pigging and DBB requirements, and is common on transmission and gathering pipelines; API 600 covers cast steel gate valves (alongside API 602 forged steel gate valves and API 603 corrosion-resistant gate valves) and is widely used in refining and power plants; API 609 covers butterfly valves (centered, double-offset and triple-offset). Their scopes differ, while the pressure boundary is normally still based on ASME B16.34. State the product standard and edition year in the RFQ.

API 607 is the fire test for soft-seated and quarter-turn valves (ball, butterfly and similar); API 6FA is the fire test for general valves. After 30 minutes of fire exposure, the test checks whether internal and external leakage remain within the allowable limits, verifying that the metal secondary seal, graphite packing and anti-blowout stem still maintain sealing after the soft seat has burned away. Fire-risk areas (oil & gas, refining) normally require fire-safe type approval. It is a type test, not a unit-by-unit factory inspection.

ISO 15848-1/-2 is the valve fugitive emission standard: -1 covers type testing and -2 production testing. It characterizes stem-seal emissions under extreme temperature and pressure and repeated cycles using leakage classes A/B/C and temperature classes (e.g. AH/BH/CH), serving compliance with European and North American environmental regulations (VOC, EPA methane, German TA-Luft). Low fugitive emission is achieved mainly through flexible graphite packing with live loading and an anti-blowout stem, and is a common requirement for petrochemical and natural gas projects.

BS 6364 is the general requirements standard for cryogenic valves, covering cryogenic material selection, design (extended bonnet) and cryogenic type testing; it is used for LNG (−162℃) and deep-cold service, with ISO 21010 and China's GB/T 24925-2019 cryogenic valve standard as references. The core requirements are: pressure-containing parts must pass low-temperature impact tests at the corresponding temperature, the extended bonnet keeps the packing and actuator away from the cryogenic medium, and operation and sealing cycle tests at low temperature must be performed per the standard.

Under PED 2014/68/EU: use the fluid group (Group 1 hazardous / Group 2 non-hazardous), maximum allowable pressure PS (applicable above 0.5 bar) and DN/volume to determine Category I–IV from the Annex II charts. Category II and above normally require a notified body; Category I can be self-declared by the manufacturer. Prepare technical documentation, material certificates (EN 10204 3.1/3.2), pressure testing (EN 12266-1), a risk assessment and the Declaration of Conformity (DoC), and affix the CE mark.

3.1 is issued by the manufacturer's own authorized inspector (steel mill or forging/casting plant), with the heat/batch number and records of chemical composition, mechanical properties and heat treatment — a self-declaration. 3.2 requires an authorized inspector independent of the manufacturing department or a third-party body (LR/DNV/TÜV/SGS/BV) to witness and sign, giving higher credibility and often mandated by tenders. Critical high-pressure parts, sour-service parts and EU export projects generally require 3.2 certificates, with correspondingly higher cost and lead time. Specify the certificate level before ordering.

It can be performed by bodies such as SGS, BV, TÜV (Rheinland/SÜD), LR and DNV, with witness points agreed in the ITP (inspection and test plan): material verification, dimensional inspection, shell pressure test, seat leakage, functional cycling, nameplate verification and final document review. H hold points require attendance and approval before work continues; W witness points allow attendance after notification. Third-party inspection suits EPC projects and high-risk orders, is usually at the buyer's cost, and the scope and witness points should be locked at contract stage.

Medium- and high-pressure valves are mostly custom-engineered, with a standard lead time of 4–10 weeks depending on material, pressure class, certification and pressure-test requirements; more exotic materials (duplex, alloy, sour service) and more certification or third-party inspection extend the cycle. Sampling or first articles typically take 2–4 weeks. State the target lead time in the RFQ and whether ITP and third-party witnessing are required, and allow document approval time for EPC projects — an honest lead time builds trust faster than an optimistic one.

Yes, OEM/ODM: nameplates, logo, packaging, painting and shipping documents (material test certificate MTC, pressure test report, operation manual) can be customized to the customer's brand, with private-label options and first article inspection (FAI). MOQ depends on the category and material; standard valve types can start from small batches (generally a few units per size), while special materials and certified orders have a higher MOQ. Drawing-based customization and drawing-upload inquiries are both supported; volume production follows sample approval.