Safety & Relief Valves – SRVL and SRVH Instrument Series
R-LOK safety and relief valves protect instrument tubing, gauges, analysers, sampling lines and small-bore hydraulic circuits from overpressure. SRVL covers 10 to 250 psig (0.69 to 17.2 bar); SRVH covers 225 to 6,000 psig (15.5 to 414 bar). Bodies are ASTM A182 F316 stainless steel, with ends from 1/4 in (6.35 mm) tube to 1/2 NPT. We supply them as your sourcing partner.
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Key features
- SRVL covers 10-250 psig (0.69-17.2 bar); SRVH covers 225-6,000 psig (15.5-414 bar).
- Orifice 4.8 mm (0.19 in) on SRVL and 3.6 mm (0.14 in) on SRVH.
- Body to ASTM A182 F316; trim to ASTM A479; spring in S17700 stainless steel.
- Set pressure adjusts externally; lock nut and wire-lock hole secure the setting.
- Viton O-rings; PTFE seat gasket on SRVL; polypropylene adjuster plug.
- Ends: 1/4-1/2 in and 6-12 mm tube, 1/4-1/2 NPT male or female.
Specifications
| Parameter | Value |
|---|---|
| Set pressure, SRVL | 10 to 250 psig (0.69 to 17.2 bar); maximum 300 psig (20.6 bar) |
| Set pressure, SRVH | 225 to 6,000 psig (15.5 to 414 bar) |
| Orifice diameter | 4.8 mm (0.19 in) SRVL; 3.6 mm (0.14 in) SRVH |
| Spring codes | blank 10-225 (SRVL), Y, P, O, B, W, R, G |
| Body | ASTM A182 F316 stainless steel (code SS); spring S17700 (17-7 PH) |
| Internals | 316 stainless steel to ASTM A479; polypropylene plug |
| Seals | Viton O-rings; PTFE seat gasket on SRVL |
| End connections | 1/4, 3/8, 1/2 in and 6, 8, 12 mm tube; 1/4, 3/8, 1/2 NPT |
How these valves work
Both series are direct-acting, spring-loaded relief valves. System pressure acts on a small poppet held closed by a spring. When pressure reaches the set point, the spring compresses, the poppet lifts and overpressure vents through the outlet port.
Opening pressure is adjusted externally with the spring adjuster and held by a lock nut. A wire-lock hole secures the setting on vibrating skids. Re-test the valve after any field adjustment, because the set point moves with the spring position.
SRVL and SRVH pressure ranges
SRVL is the low-pressure valve: 300 psig (20.6 bar) maximum working pressure, set pressure 10 to 250 psig (0.69 to 17.2 bar), one adjustable spring covering the 10 to 225 psig band, 4.8 mm (0.19 in) orifice.
SRVH is the high-pressure valve: 6,000 psig (414 bar) maximum working pressure, set pressure 225 to 6,000 psig (15.5 to 414 bar), 3.6 mm (0.14 in) orifice. Eight spring codes cover the range in bands.
Materials, seals and connections
The body is 316 stainless steel to ASTM A182 F316 (code SS); internal parts are 316 stainless steel to ASTM A479; the spring is S17700 (17-7 PH). Sealing uses Viton O-rings, and SRVL adds a PTFE seat gasket.
Ends are ferrule tube fittings, male or female NPT, in mixed combinations. Standard sizes are 1/4, 3/8 and 1/2 in tube, 6, 8 and 12 mm tube, and 1/4, 3/8 and 1/2 NPT.
Standards referenced: Body material specified as ASTM A182 F316 stainless steel.; Internal parts specified to ASTM A479 (316 stainless steel bar).; NPT ends threaded to ASME B1.20.1; tube ends use the R-LOK ferrule system..
Typical duties: Instrument air and gas distribution panels; Gauge, transmitter and analyser protection; Sampling systems and chemical injection skids; Small-bore hydraulic and pneumatic circuits; Blocked-in liquid lines needing thermal relief; High-purity and specialty gas panels.
Safety and relief valve model selection guide (SRVL / SRVH series)
| Series / model | Size | Connection | Working pressure | Body material | Seat / packing | Notes |
|---|---|---|---|---|---|---|
| SRVL low-pressure safety valve (S4) | 4.8 mm bore (SRVL) | 1/4" tube fitting in / 1/4" tube fitting out (code S4) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 38.7 mm x L2 37.3 mm x H 104.6 mm; one spring covers the full 10-250psig adjustment range; spring colour blue |
| SRVL low-pressure safety valve (S6M) | 4.8 mm bore (SRVL) | 6 mm tube fitting in / 6 mm tube fitting out (code S6M) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 38.7 mm x L2 37.3 mm x H 104.6 mm |
| SRVL low-pressure safety valve (S8M) | 4.8 mm bore (SRVL) | 8 mm tube fitting in / 8 mm tube fitting out (code S8M) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 38.7 mm x L2 37.3 mm x H 104.6 mm |
| SRVL low-pressure safety valve (S6) | 4.8 mm bore (SRVL) | 3/8" tube fitting in / 3/8" tube fitting out (code S6) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 44.4 mm x L2 44.4 mm x H 111.7 mm |
| SRVL low-pressure safety valve (S8) | 4.8 mm bore (SRVL) | 1/2" tube fitting in / 1/2" tube fitting out (code S8) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 46.7 mm x L2 46.7 mm x H 114.0 mm |
| SRVL low-pressure safety valve (S12M) | 4.8 mm bore (SRVL) | 12 mm tube fitting in / 12 mm tube fitting out (code S12M) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 46.7 mm x L2 46.7 mm x H 114.0 mm |
| SRVL low-pressure safety valve (M8N x S8) | 4.8 mm bore (SRVL) | 1/2 NPT male thread in / 1/2" tube fitting out (code M8N-S8) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 46.7 mm x L2 35.7 mm x H 103.0 mm |
| SRVL low-pressure safety valve (M8N x S12M) | 4.8 mm bore (SRVL) | 1/2 NPT male thread in / 12 mm tube fitting out (code M8N-S12M) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 46.7 mm x L2 35.7 mm x H 103.0 mm |
| SRVL low-pressure safety valve (M4N x F4N) | 4.8 mm bore (SRVL) | 1/4 NPT male thread in / 1/4 NPT female thread out (code M4N-F4N) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 30.0 mm x L2 32.2 mm x H 99.5 mm |
| SRVL low-pressure safety valve (M6N x F6N) | 4.8 mm bore (SRVL) | 3/8 NPT male thread in / 3/8 NPT female thread out (code M6N-F6N) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 34.5 mm x L2 32.2 mm x H 99.5 mm |
| SRVL low-pressure safety valve (M8N x F8N) | 4.8 mm bore (SRVL) | 1/2 NPT male thread in / 1/2 NPT female thread out (code M8N-F8N) | Max. working pressure 300psig(20.6bar); opening pressure 10psig to 250psig(0.69bar to 17.2bar) | SS = ASTM A182 F316 stainless steel | Sealing washer PTFE; valve seat 316 stainless/A479; O-ring VITON | Dimensions L1 38.0 mm x L2 35.7 mm x H 103.0 mm |
| SRVH high-pressure safety valve – spring code Y | 3.6 mm bore (SRVH) | Same body / end-connection options as the shared SRVL-SRVH size table (codes S4 to M8N-F8N) | Max. working pressure 6000psig(414bar); opening pressure 225psig to 6000psig(15.5bar to 414bar) | SS = ASTM A182 F316 stainless steel | Valve seat 316 stainless/A479; O-ring VITON; seal ring VITON; stem 316 stainless/A479; no packing material published | Spring code Y covers 225-750psig; order code format SRVH-M8N-S8-Y-SS; set pressure locked by a socket set screw |
| SRVH high-pressure safety valve – spring code P | 3.6 mm bore (SRVH) | Same body / end-connection options as the shared SRVL-SRVH size table (codes S4 to M8N-F8N) | Max. working pressure 6000psig(414bar); opening pressure 225psig to 6000psig(15.5bar to 414bar) | SS = ASTM A182 F316 stainless steel | Valve seat 316 stainless/A479; O-ring VITON; seal ring VITON; stem 316 stainless/A479; no packing material published | Spring code P covers 750-1500psig |
| SRVH high-pressure safety valve – spring code O | 3.6 mm bore (SRVH) | Same body / end-connection options as the shared SRVL-SRVH size table (codes S4 to M8N-F8N) | Max. working pressure 6000psig(414bar); opening pressure 225psig to 6000psig(15.5bar to 414bar) | SS = ASTM A182 F316 stainless steel | Valve seat 316 stainless/A479; O-ring VITON; seal ring VITON; stem 316 stainless/A479; no packing material published | Spring code O covers 1500-2250psig |
| SRVH high-pressure safety valve – spring code B | 3.6 mm bore (SRVH) | Same body / end-connection options as the shared SRVL-SRVH size table (codes S4 to M8N-F8N) | Max. working pressure 6000psig(414bar); opening pressure 225psig to 6000psig(15.5bar to 414bar) | SS = ASTM A182 F316 stainless steel | Valve seat 316 stainless/A479; O-ring VITON; seal ring VITON; stem 316 stainless/A479; no packing material published | Spring code B covers 2250-3000psig |
| SRVH high-pressure safety valve – spring code W / R / G | 3.6 mm bore (SRVH) | Same body / end-connection options as the shared SRVL-SRVH size table (codes S4 to M8N-F8N) | Max. working pressure 6000psig(414bar); opening pressure 225psig to 6000psig(15.5bar to 414bar) | SS = ASTM A182 F316 stainless steel | Valve seat 316 stainless/A479; O-ring VITON; seal ring VITON; stem 316 stainless/A479; no packing material published | Spring code W 3000-4000psig, R 4000-5000psig, G 5000-6000psig |
Selection notes: Model selections and figures are taken from the catalogue ordering table (订购信息, page 11-22) and the size table (尺寸表, page 11-21) of the safety valve section that begins on catalogue pages 11-19 and 11-20. The catalogue prints these valves in one shared size table for the low-pressure SRVL series (bore 4.8 mm) and the high-pressure SRVH series (bore 3.6 mm); every size code listed there can be ordered in either series.
Catalogue reference 11-19, 11-20, 11-21, 11-22. Confirm the final rating against the data sheet issued with your order.
See also: Ball Valves · Check Valves · Diaphragm Valves · Gauge Valves Manifolds · Needle Valves · Plug Valves · Pressure Regulators · Purge Bleed Valves
Frequently asked questions
Can the set pressure be adjusted after installation?
Yes. Opening pressure is adjusted externally with the spring adjuster and locked with a lock nut; a wire-lock hole secures the setting. Re-test the valve after adjustment, because the set point moves with the spring position.
How do I choose between SRVL and SRVH?
Choose from the set pressure. SRVL covers 10 to 250 psig (0.69 to 17.2 bar), 4.8 mm orifice; SRVH covers 225 to 6,000 psig (15.5 to 414 bar), 3.6 mm orifice. Send set pressure, reseal pressure, fluid and connections; we confirm the series and code.
What documents come with the valves?
Material certificates for the body and internal parts can be supplied with the shipment on request. Tell us the certificate type, the standard you work to and any third-party inspection requirement in your enquiry so we can confirm it before we quote.
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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