Valve Technology Glossary

A reference guide to the technical terms used across this website. Definitions reflect common industry usage and the standards referenced by Valland products.

Ball valve. A quarter-turn valve whose obturator is a sphere with a bore; rotating the ball 90° opens or closes the passage.

 

Trunnion mounted. Ball valve design where the ball is anchored by upper and lower trunnions and the spring-loaded seats move against it. Standard for large sizes and high pressure classes.

 

Floating. Ball valve design where the ball is held by the seats and line pressure pushes it against the downstream seat to seal. Compact and economical for small bores.

 

Top entry. Valve with a single-piece body accessed from the top through a bolted bonnet or pressure seal: internals can be maintained with the valve in line.

 

Rising stem ball valve. Ball valve in which the stem lifts and tilts the ball away from the seat before rotating it, eliminating rubbing between sealing surfaces — suited to frequent cycling and abrasive media.

 

Through conduit gate valve. Gate valve whose gate has a full circular bore: in open position the passage is unobstructed and piggable.

 

Slab gate. Through conduit gate valve with a single-piece gate sealing by line pressure against floating seats.

 

Expanding gate (single/double). Through conduit gate valve with a gate-and-segment assembly that wedges mechanically at closure, sealing independently of line pressure — on one seat (single) or both (double).

 

Check valve. Self-acting valve preventing flow reversal. Swing check: hinged disc. Dual plate check: two spring-loaded half-discs in a compact body.

 

DBB — Double Block and Bleed. Single valve providing two seat barriers against pressure with a means of venting the cavity between them (API 6D definition).

 

DIB — Double Isolation and Bleed. Valve providing two seats each capable of sealing independently (DIB-1: both bidirectional; DIB-2: one bidirectional, one unidirectional).

 

SPE / DPE seats. Self-relieving (single piston effect) seats vent cavity overpressure automatically; double piston effect seats seal in both directions, enabling DIB configurations.

 

Back seat. Stem/bonnet configuration that allows replacing the stem sealing with the valve in line and under pressure.

 

Face-to-face. The end-to-end dimension of a valve, standardized (e.g. ASME B16.10) or custom (“short pattern”) to fit existing piping.

 

Piggable. A line (or valve) whose full bore allows the passage of pigs — devices for cleaning and inspecting pipelines.

 

API 6A / API 6D / API 6DSS. American Petroleum Institute specifications for wellhead and christmas tree equipment (6A), pipeline and piping valves (6D) and subsea pipeline valves (6DSS).

 

PSL. Product Specification Level per API 6A: increasing levels of quality control requirements (PSL 1 to PSL 3G/4).

 

PR2. API 6A performance requirement level: qualification testing with pressure/temperature cycling and endurance cycles.

 

PED. European Pressure Equipment Directive 2014/68/EU, governing pressure equipment sold in the EU.

 

SIL. Safety Integrity Level per IEC 61508: a measure of the risk reduction provided by a safety function. Valland valve designs are certified up to SIL 3.

 

Fire safe. Design qualified by fire type testing (ISO 10497, API 6FA, API 607) to remain essentially tight during and after a fire.

 

Fugitive emissions. Unintended leakage of process media to atmosphere through stem seals and body joints, qualified per ISO 15848-1/2.

 

NACE MR0175 / ISO 15156. Materials standard for H2S-containing (sour) environments, preventing sulfide stress cracking.

 

Hydrogen embrittlement. Degradation of metal toughness caused by atomic hydrogen absorption; drives dedicated material selection for hydrogen valves.

 

Cryogenic service. Service at very low temperatures (typically below -50 °C, down to -196 °C for LNG/liquid nitrogen), requiring dedicated materials, design and testing (BS 6364).

 

Hyperbaric testing. Testing under external pressure simulating subsea installation depth.

 

FEA — Finite Element Analysis. Numerical simulation of stresses, deformations and contacts, used by Valland to verify every new valve design.

 

Additive Manufacturing (AM). Production of parts by adding material layer by layer from a digital file (“3D printing”).

 

L-PBF / DMLS. Laser Powder Bed Fusion: AM process melting metal powder layer by layer with a laser — the core metal technology of Valland3D.

 

FDM / FFF. Fused Deposition Modelling / Fused Filament Fabrication: polymer AM process extruding thermoplastic material layer by layer.

 

DNVGL-ST-B203 / API 20S / API 20T. Standards governing qualification of additively manufactured metallic (B203, 20S) and polymeric (20T) parts for the energy industry.