Glossary of 4130 pipe and fitting terms

A one-line definition of each term used on this site's product pages and guides, from API 6A to XXS. Select a link to read the full explanation.

AISI 4130UNS G41300

A low-alloy steel with about 0.30% carbon, 1% chromium and 0.2% molybdenum, heat treatable to high strength and weldable with preheat. More

API 5CT

API specification for casing and tubing. Its grade L80 lends its strength and hardness limits to 4130 callouts. More

API 6A

API specification for wellhead and Christmas tree equipment: pressure ratings, material designations, temperature and material classes, PSL levels.

API 16C

API specification for choke and kill equipment: rigid, flexible and articulated lines and their connections. More

API Standard 53

API standard for blowout prevention equipment systems, including choke and kill line layout and sizing. More

ASME B16.9

Standard for factory-made wrought butt-welding fittings: dimensions, tolerances and the rule that a fitting is rated like straight pipe of the same material and wall. More

ASME B16.25

Standard for butt-welding ends: the 37.5° bevel and the compound bevel for heavy walls. More

ASME B36.10M

Standard for welded and seamless wrought steel pipe dimensions: outside diameters and schedule walls. More

ASTM A519

Specification for seamless carbon and alloy steel mechanical tubing, which includes Grade 4130. It sets chemistry and dimensions, not pressure ratings. More

Block ell or block tee

A turn machined in a solid block, with an abrupt 90° change of direction. Needs a target or cushion in choke and kill lines. More

Center-to-end

The distance from the center of a fitting, where the axes of its legs meet, to the face of an end. More

Choke line

The line that carries well fluids from the BOP stack to the choke manifold during well control. More

Cold working pressure (CWP)

The rating of flowline iron and hammer unions at ambient temperature. More

Crossover

A fitting that joins two different union figures or two sizes. More

EN 10204 3.1

An inspection certificate issued by the manufacturer's quality department, independent of production, with results of tests on the actual heat or lot. 3.2 adds an independent inspector's signature. More

Extrados

The outer wall of a bend, which thins in forming and takes the impact of solids in service. More

Figure number (FIG)

The design designation of a hammer union, such as FIG 1502, which fixes its thread, seal and pressure rating. More

Fluid cushion

A pocket of fluid in a blind end that takes the impact of flow at a turn instead of the pipe wall. More

Hammer unionWing union

A quick connection of a male sub with a wing nut and a female sub, made up by striking the nut with a hammer. More

HRCRockwell C hardness

A hardness scale. 22 HRC is the general sour-service limit for carbon and low-alloy steels. More

HV10Vickers hardness

Vickers hardness with a 10 kgf load, used for weld hardness surveys. 250 HV10 is the sour-service limit for low-alloy steel welds. More

Hydrostatic test pressureShell test

The water pressure a part is proven at before service, 1.5 times the rating for API 6A equipment at 10,000 psi and above. More

Integral fitting

A fitting whose union ends are machined from its own forged body, with no welds. More

Kill line

The line that carries kill-weight mud from the pumps into the well. More

L80

An API 5CT grade with 80 to 95 ksi yield, 95 ksi minimum tensile and 23 HRC maximum. "4130 L80" means 4130 heat treated to those limits. More

LateralWye

A fitting that joins a branch to the run at 45°. More

Long radius (LR)

An elbow with a center-to-end of 1.5 times its nominal size. More

Long sweep

A bend with a radius several times the bore, made to drawing, for erosive lines. More

Material class

API 6A classes AA to HH. DD, EE, FF and HH are for sour service and require NACE MR0175 / ISO 15156. More

Material designation

API 6A strength levels 36K, 45K, 60K and 75K, each with minimum yield, tensile, elongation and reduction of area. More

NACE MR0175 / ISO 15156

The standard for materials in hydrogen sulfide service. Part 2 covers carbon and low-alloy steels such as 4130. More

Normalizing

Heating above the transformation range and cooling in air, to refine and even out the grain. More

NPSNominal pipe size

The size designation of pipe and fittings, for example NPS 3, whose outside diameter is 3.5 in. More

OD x ID

A heavy-wall size given by outside and inside diameter, for example 5.5 in OD by 3 in ID. More

Post-weld heat treatment (PWHT)

Heat treatment after welding to lower hardness and residual stress. At least 1,150 °F (621 °C) for low-alloy steel welds in sour service. More

PSLProduct specification level

API 6A levels PSL 1 to 4, each adding tests and traceability. More

Quench and temper (Q&T)

Hardening by heating and quenching, then tempering to the strength and hardness required. More

R/d

Bend radius divided by pipe diameter. API Standard 53 treats bends at 10 or more as large-radius. More

Rated working pressure (RWP)

The maximum pressure in service of API 6A and 16C equipment: 2K, 3K, 5K, 10K, 15K, 20K. More

Short radius (SR)

An elbow with a center-to-end of 1 times its nominal size. More

Sour service

Service in fluids containing hydrogen sulfide, which can crack hard steel under stress. More

Targeted tee

A tee that turns the flow into a blanked run end, where a cushion or replaceable target takes the impact. More

Temperature class

API 6A temperature ranges, from K (-75 to 180 °F) to Y (0 to 650 °F). More

XXSDouble extra strong

A heavy pipe wall in ASME B36.10M, for example 0.600 in on NPS 3. More