Needle Valves Β· Lower Packing Needle Valves
Straight Lower-Packing Needle Valves
Straight lower-packing needle valves place the packing below the stem threads, so line media never contacts the threaded stem and cannot wash the lubricant out of it - the reason this execution is specified on sampling and instrumentation lines where stem scoring would destroy shutoff. The benchmark catalog execution is built in 316 SS with instrumentation tube-fitting connections at 1/8 in, a 0.172 in (4.4 mm) orifice, a vee-type shutoff stem and PTFE packing, listed in the manufacturer catalog as a 31-part straight-pattern lower-packing range.
Part of the Lower Packing Needle Valves family
Last updated: 2026-11
Specifications
| body materials | 316 SS |
|---|---|
| end connections | manufacturer tube fitting (both ends) |
| end connection size | 1/8 in |
| orifice size | 0.172 in (4.4 mm) |
| stem type | Vee type shutoff |
| packing materials | PTFE |
| stem type options | Vee Type Shutoff, Soft Seal Shutoff |
| end connections | Duolok Tube Fitting, MNPT, FNPT |
| orifice options | 0.172 in (4.4 mm), 0.250 in (6.4 mm) |
| connection size range | 1/8 in to 1/2 in |
| model series | 400/406/436/438 series in 316 SS (K suffix = soft seal shutoff); 31 orderable models in the catalog table |
Application & selection guidance
Select this execution where the medium is dirty, dry or corrosive enough to attack conventional top-packed stems - lower packing keeps the threads out of the flow entirely. It suits small-bore sample, bleed and instrumentation takeoffs: the benchmark execution is a 1/8 in tube-fitting valve with a 0.172 in orifice and vee-type shutoff stem in 316 SS with PTFE packing. Confirm the connection system against the instrumentation tubing standard in use before ordering.
Frequently asked questions
Why does packing position matter on a needle valve?
In a conventional top-packed valve the stem threads sit above the packing but still see media migration; dry or dirty media then washes lubricant from the threads and scores the stem, degrading shutoff. Lower packing sits below the threads, so the flow path never reaches them - the threads stay lubricated and the stem stays true over far more operating cycles.
What is the benchmark execution rated for in size and flow?
The catalog straight execution is a 316 SS valve with 1/8 in instrumentation tube fittings at both ends, a 0.172 in (4.4 mm) orifice, a vee-type shutoff stem and PTFE packing. It is listed within a 31-part straight-pattern lower-packing range, so other connection and orifice combinations exist in the same family - state the tubing standard and flow with the inquiry to confirm the matching part.
When should this execution be preferred over a locked bonnet needle valve?
Both serve instrumentation duty; the choice is media-driven. Where thread washout or stem scoring is the dominant risk - dirty, dry, abrasive or crystallizing media - lower packing wins because the threads are out of the flow. Where bonnet back-off under vibration at very high pressure is the dominant risk, the locked bonnet execution is the better match.
Ordering & documentation
Documents
Ask for the documentation set you need with the inquiry β typical items for this execution (material certificates, test reports to the listed inspection standard, dimensional drawings) are confirmed and supplied with the quotation.
Quotation
A quotation-ready inquiry states: nominal size and pressure rating, body and seat material preference, end connection, operation, and the service medium with temperature. Typical values on this page are benchmark reference ranges; the binding values are confirmed at quotation.
Sample & supply
Supply terms, order quantities and lead time are agreed per order β state the destination country and required schedule with the inquiry.
Storage & shipping
Store valves with seats and seals protected from UV, ozone and deformation, keep end-face protectors on until installation, and for elastomer- or PTFE-seated executions avoid prolonged outdoor storage β seat compounds age fastest in direct sunlight and freezing conditions.
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