Abbreviation & Mill Tolerance

BB Bolted bonnet 

OS&Y Outside screw spindle and yoke 

BE Beveled end 

PE Plain end 

Br Bronze 

PTFE Teflon 

BW But welding 

RB Reduce Bore 

CS Carbon steel 

RPTFE Reinforced Teflon 

Cu Ni Copper - Nickel 

RF Raised face

Cr Chromium 

RJ Ring joint 

EFW Electric fusion welded 

RP Regular Pattern 

ERW Electric resistance welded 

SAW Submerged arc welded 

ENP Electro Nipple Plating 

SMLS Seamless 

FB Full Bore 

SO Slip-on 

FF Flat face 

SP Standard practice (MSS) 

F6 Stainless steel, 13% Cr 

SP Short Pattern 

Gr. Grade SS Stainless steel 

GRP Glass fiber reinforced plastic 

STD Standard 

LJ Lap joint 

SW Socket welding 

LP Long Pattern 

TE Threaded end 

LTCS Low Temperature Carbon Steel 

TPE Top entry 

Mo Molybdenum 

WN Welding neck 

NPT Threading as per ASME B1.20.1

Mill tolerance 

The mill tolerance on wall thickness shall be as follows: 

- minus 8% for API 5 LX grades in diameters 20” and above 

- minus 12 ½% for all other materials or diameters