Valve Gland Nuts and Bolting: Torque Specifications and Anti-Seize

Proper gland nut torquing ensures adequate packing compression to prevent leakage while avoiding over-compression that increases stem friction and accelerates wear. Using anti-seize on packing gland studs extends fastener life and simplifies future maintenance.

Gland Nut Torque

Valve manufacturers publish gland nut torque values based on packing type, stem diameter, and packing ring count. Torque values typically range from 10 to 150 N·m depending on valve size. Initial torque after new packing installation is followed by a reduced maintenance torque after the packing seats.

Never use impact tools on gland studs—use a calibrated torque wrenchApply torque in equal increments on dual-stud glands to avoid cocking the followerRe-torque after first few thermal cycles on new packing installationsDocument as-found and as-left torque values in maintenance records

Anti-Seize Compounds

High-temperature anti-seize (nickel, copper, or moly-based) on gland stud threads prevents galling and seizure, particularly in high-temperature steam and hydrocarbon service. Apply anti-seize to threads and under the nut bearing face, not inside the packing box.

Stud and Nut Material

Gland studs in high-temperature service use B7/2H (chromium-molybdenum steel). For sour service per NACE MR0175, hardness-controlled B7M studs with 2HM nuts are required. Austenitic stainless steel studs (B8M) suit cryogenic and corrosive service.

Check stud hardness compliance with NACE MR0175 in H2S serviceReplace studs showing pitting, thread damage, or stretchingVerify nut material matches stud for galvanic compatibilityUse flat washers to distribute load on soft bonnet materials