Ultra-High-Purity Diaphragm Valves (LD and HD Series)
Ultra-high-purity diaphragm valves isolate the process fluid from the actuator with a metal diaphragm and an enclosed seat, so no stem packing can leak. R-LOK supplies two families: the LD range to 250 psig (17.2 bar) and the HD range to 3,000 psig (207 bar). Bodies come in SS316L, ASTM A479 or SS316L VAR to SEMI F20-0305, with PCTFE, PFA or Vespe seats.
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Key features
- Metal diaphragm isolates the media; no stem packing to leak or wear.
- LD rated to 250 psig (17.2 bar), HD to 3,000 psig (207 bar).
- Body materials: SS316L, ASTM A479 bar or SS316L VAR to SEMI F20-0305.
- Diaphragm in SS316L or Hastelloy C-22; seat in PCTFE, PFA or Vespe.
- Leakage specified at 1 x 10-9 std cm3/s helium, internal and external.
- Wetted finish Ra 0.25 um (10 uin) BA or 0.13 um (5 uin) EP.
Specifications
| Parameter | Value |
|---|---|
| Series and sizes | LD and HD manual or pneumatic, B23 manifold; ports 1/4 to 3/4 in |
| Working pressure | LD 250 psig (17.2 bar); HD 3,000 psig (207 bar) |
| Flow coefficient (Cv) | LD 0.27, 0.7 and 1.7; HD 0.27; B23 manifold 0.22 and 0.7 |
| Body material | SS316L, ASTM A479 or SS316L VAR to SEMI F20-0305 |
| Diaphragm and seat | SS316L or Hastelloy C-22 diaphragm; PCTFE, PFA or Vespe seat |
| Temperature | PCTFE -40 to 80 C (-40 to 176 F); PFA/Vespe -26 to 177 C |
| Finish | BA/EP Ra 0.25/0.13 um (10/5 uin); SEP on SS316L VAR |
How it works
A metal diaphragm is clamped between the body and the actuator bonnet. Turning the handwheel or pressurising the pneumatic actuator pushes the diaphragm onto the seat and closes the flow path. The diaphragm is the only moving wetted part, so valves stay helium leak-tight.
The seat is fully enclosed by the body, so the shut-off area is protected from line contamination. Internal volume is small, which shortens purge and evacuation cycles on gas panels, sampling systems and analytical lines.
Materials and seating
Bodies are supplied in SS316L, ASTM A479 bar or SS316L VAR to SEMI F20-0305. Diaphragms are SS316L or Hastelloy C-22, and seats can be PCTFE, PFA or Vespe. Material certificates for body and diaphragm heat numbers are available.
Three finish grades are offered. BA gives a ground and polished internal surface at Ra 0.25 um (10 uin) with single-layer packing. EP adds electrolytic polishing at Ra 0.13 um (5 uin) with double-layer packing. SEP is the highest grade.
Pressure, temperature and sizes
The seat material sets the service envelope, so pressure and temperature cannot be quoted independently. PCTFE seats cover -40 to 80 C (-40 to 176 F). PFA and Vespe seats cover -26 to 177 C (-15 to 350 F).
LD and HD valves take 1/4 in, 3/8 in and 1/2 in ends; LD also extends to 3/4 in. Four end connections are offered: VCR male (code V), VCR female (code VF), GBO-LOK fitting (code T) and butt weld (code BW).
Standards referenced: SS316L VAR body material referenced to SEMI F20-0305; Bar stock material to ASTM A479; Pressure ratings referenced to ASME B31.3 for the stated temperature.
Typical duties: Semiconductor gas sticks and bulk specialty gas panels; High-purity gas and chemical delivery in energy plants; Pharmaceutical clean utilities and sterile process lines; Analytical and process sampling systems; Hydrogen service and test benches; Petrochemical analyser and instrument air systems.
Ultra-high-purity diaphragm valve model selection guide
| Series / model | Size | Connection | Working pressure | Cv | Notes |
|---|---|---|---|---|---|
| LD4MS-VC | 1/4" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.27 | LD series; manual; low pressure |
| LD8MS-VC | 1/2" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.7 | LD series; manual; low pressure |
| LD12MS-VC | 3/4" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 1.7 | LD series; manual; low pressure |
| LD4MS-VFC | 1/4" | VCR female thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.27 | LD series; manual; low pressure |
| LD8MS-VFC | 1/2" | VCR female thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.7 | LD series; manual; low pressure |
| LD12MS-VFC | 3/4" | VCR female thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 1.7 | LD series; manual; low pressure |
| LD4CS-VC | 1/4" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.27 | LD series; pneumatic (air-operated); low pressure |
| LD4OS-VC | 1/4" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.27 | LD series; pneumatic (air-operated); low pressure |
| LD8CS-VC | 1/2" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.7 | LD series; pneumatic (air-operated); low pressure |
| LD8OS-VC | 1/2" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.7 | LD series; pneumatic (air-operated); low pressure |
| LD12CS-VC | 3/4" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 1.7 | LD series; pneumatic (air-operated); low pressure |
| LD12OS-VC | 3/4" | VCR male thread | 250psig (17.2bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 1.7 | LD series; pneumatic (air-operated); low pressure |
| HD4MS-VC | 1/4" | VCR male thread | 3000psig (207bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.27 | HD series; manual; high pressure |
| HD4MS-VFC | 1/4" | VCR female thread | 3000psig (207bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.27 | HD series; manual; high pressure |
| B23V | 1/4" | VCR female thread | Low pressure: 250psig (17.2bar); high pressure: 3000psig (207bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.22 | B23 series; two-valve three-way manual manifold; B23V flow pattern |
| B23V | 1/2" | VCR female thread | Low pressure: 250psig (17.2bar); high pressure: 3000psig (207bar); -40 to 80 degC (-40 to 176 degF) with PCTFE seat, -26 to 177 degC (-15 to 350 degF) with PFA/Vespel seat | 0.7 | B23 series; two-valve three-way manual manifold; B23V flow pattern |
Selection notes: Body material is printed identically on pages 4-01, 4-05, 4-11 and 4-19 as SS316L / A479 or SS316L VAR / SEMI F20-0305, so it is not repeated per row; the grade table shows SS316L for BA and EP and SS316L VAR for SEP – confirm which grade each model code ships as standard. Seat / packing is printed as PCTFE or PFA or Vespel and diaphragm as SS316L or Hastelloy C-22 or cobalt-based superalloy – confirm the standard seat and diaphragm per model, since the published temperature range differs by seat material.
Catalogue reference 4-01, 4-02, 4-05, 4-06, 4-11, 4-12, 4-19, 4-20. Confirm the final rating against the data sheet issued with your order.
See also: Ball Valves · Check Valves · Gauge Valves Manifolds · Needle Valves · Plug Valves · Pressure Regulators · Purge Bleed Valves · Safety Relief Valves
Frequently asked questions
How do I choose between PCTFE, PFA and Vespe seats?
Temperature drives the choice. PCTFE covers -40 to 80 C (-40 to 176 F) and suits low-temperature gas service. PFA and Vespe cover -26 to 177 C (-15 to 350 F), so use them above 176 F. Send the media and operating temperature.
Can you supply VCR and GBO-LOK ends instead of butt weld?
Yes. VCR male, VCR female, GBO-LOK compression and butt weld are all catalogue options, so the same body takes the end that matches your panel. Send your end detail and face-to-face dimension when replacing an existing valve.
Which documents come with the shipment?
Each valve is helium leak tested before dispatch, and the shipment includes the material certificate covering body and diaphragm heat numbers, a dimensional inspection report and the leak test record. If your QA team reviews documents before shipping, tell us at order stage.
Request a quote or technical clarification
Send us the model, size, material and quantity you need — or a photo of the existing part. We reply with a quotation, availability and the applicable documents, usually within one working day.
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