API · ASME · DIN · EN standard industrial valves
Locked Bonnet Needle Valves
Locked bonnet needle valves clamp the bonnet to the body through a machined metal joint held by a locking ring, so vibration, packing adjustment or an over-rotated stem cannot disassemble the bonnet — severe-service isolation and metering for oil and gas, chemical and power installations. The range covers LN service up to 6000 psig (413 bar) from -73°C to 648°C with 316 SS, Alloy 400 or C-276 bodies, and the HLN 10K line up to 10000 psig (689 bar) in 316 SS, with per-size orifice/Cv tables, live-loaded PTFE/flexible-graphite/PEEK packing and non-rotating, regulating or metering stems. Selection turns on the pressure class (6K versus 10K), the orifice/Cv point the loop needs, and packing choice against temperature. Multi-source references add the operating frame: severe-service design intent spanning high vibration, abrasive/corrosive media and frequent cycling, lock-ring bonnet retention secured by a separate screw in contrast to single-nut union bonnets, live-loaded chevron packing with in-line packing adjustment in pressurized systems, hardened 17-4 PH stem threads retaining lubricant, non-rotating lower stems protecting seat and stem tip across cycles, back seating isolating packing when fully open, union/screwed/locked bonnet taxonomy, reference alloy derating (Alloy 400 about 5,000 psig, titanium about 3,500 psig), flexible-graphite packing to 1,200°F with pressure reduced at temperature, and family Cv spans of about 0.3 to 3.6 by orifice size.
Part of the Needle Valves family
Last updated: 2026-10
Family specifications
| temperature range | -73°C to 648°C (-100 to 1200° F) |
|---|---|
| pressure class | up to 6000 psig (413 bar) |
| pressure class | up to 10000 psig (689 bar) |
| ln orifice cv | LN4: 0.156 orifice (0.34), LN6: 0.250 orifice (0.85), LN8: 0.437 orifice (2.18) |
| hln orifice cv | HLN4: 0.156 orifice (0.34), HLN6: 0.250 orifice (0.85) |
| patterns | Straight, angle, gauge, block and bleed |
| body materials | 316 SS, Alloy 400, C-276 |
| packing materials | PTFE (Standard) and flexible graphite. PEEK packing is available for LN6 and HLN6 valves only. |
| stem types | Non-rotating vee, soft seal (PCTFE), regulating, metering |
| severe service design intent | LN Series Locked Bonnet Needle Valves are designed for severe service applications having pressures up to 6000 psig (413 bar), temperatures from -100 to 1200°F (-73 to 648°C), high vibration, abrasive/corrosive media, and frequent cycling. |
| lock ring construction | the bonnet is screwed into the valve body then locked in place with a lock ring secured with a separate screw. |
| union bonnet weakness | There is nothing to prevent the nut from accidental disassembly or from loosening due to vibration, and there is no positive visual indication that the nut is tight. |
| reliability feature set | LN Series features including live loaded chevron packing, non-rotating lower stem, and stem threads that are isolated from system media work together for leak-tight reliability, high cycle life, low torque operation and low maintenance. |
| non rotating stem benefit | Reduces packing maintenance because the stem does not rotate within the packing |
| in line packing adjustment | Allows in line packing adjustment in pressurized system |
| stem thread material | Reference stem threads in hardened 17-4 PH stainless steel |
| thread lubrication benefit | Retain lubricants for easy operation and longer cycle life |
| severe applications ref | LN Series valves are used in oil & gas exploration and refining, high pressure instrumentation, test stands, steam systems, high pressure control systems and many other applications. |
| code basis ref | Meets ASME B31.1 and B31.3 design pressure calculations |
| bonnet taxonomy | a union bonnet is joined to the body by a union nut, a screwed bonnet is threaded into the body, and a locked bonnet is threaded and then retained by a separate locking device. |
| alloy derating ref | Alloy 400 is rated lower (about 5,000 psig / 345 bar) and titanium about 3,500 psig (241 bar) on selected ranges. |
| graphite temp ref | Flexible graphite packing raises the upper limit to 1,200°F (649°C) on selected configurations, with the pressure rating reduced at temperature |
| cv span ref | Approximately 0.3 to 3.6, by orifice size (approximately 0.16 in. to 0.44 in., or 4 mm to 11 mm); larger on some designs |
| family disclaimer ref | Family ranges for comparison only, not simultaneous ratings. Exact pressure, temperature and flow are confirmed against the selected model, size, material and end connections. |
| union bonnet repack ref | The bonnet resists loosening under vibration and pressure pulsation, and the valve can be repacked without removing it from the line. |
| vernier principle | The virtue of the needle valve is from the vernier effect of the ratio between the needle's length and its diameter, or the difference in diameter between needle and seat. |
Scope & source notes
| cv span | Cv span: reference locked-bonnet families reach Cv approximately 0.3 to 3.6 with orifices to 0.44 in., while the tenant LN tables top out at Cv 2.18 (LN8) - the reference envelope exceeds the tenant top orifice/Cv point. |
|---|---|
| alloy derating | Alloy derating: reference guidance derates Alloy 400 to about 5,000 psig and titanium to about 3,500 psig on selected ranges, while the tenant page states LN service up to 6000 psig across 316 SS, Alloy 400 and C-276 - the tenant band does not split pressure by body material. |
| temperature pressure coupling | Temperature/pressure coupling: reference flexible-graphite 1,200°F ratings carry an explicit pressure reduction at temperature, while the tenant -73°C to 648°C band is stated without a derating curve. |
| code basis | Code basis: reference executions declare ASME B31.1/B31.3 design pressure calculations, while the tenant page states no design-code basis. |
Ordering & documentation
Documents
Ask for the documentation set with the inquiry — typical items (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
Send the medium, temperature, pressure, size and connection for a quotation-ready inquiry. Lead time, MOQ and price are confirmed at quotation, together with the documents to be supplied with the order.
Sample & supply
Supply terms, order quantities and lead time are agreed per order — state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, and keep end-face protectors on until installation; storage limits and shipping arrangements for the selected materials are confirmed at quotation.
Frequently asked questions
What sizes and pressure ratings are available for locked bonnet needle valves?
the published pressure ratings are up to 6000 psig (413 bar). Availability of a specific size and rating is confirmed at quotation.
What materials are locked bonnet needle valves available in?
The published specification lists body materials: 316 SS, Alloy 400, C-276. Material availability for a specific size and rating is confirmed at quotation.
What working temperature range do locked bonnet needle valves cover?
The published working temperature range is -73°C to 648°C (-100 to 1200° F). For a medium at the edge of the range, confirm the suitability of the selected seat and body materials at quotation.
What should a quotation inquiry for locked bonnet needle valves include?
The governing standard and class, nominal size, body and seat materials, the service medium with temperature, and the destination — anything missing is confirmed during quotation.
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