Swagelok R3A Series High-Pressure Proportional Relief Valve

Overview

The Swagelok R3A is a high-pressure proportional relief valve for liquid or gas service in instrument, sampling and small-bore process systems. Unlike a pop-action safety valve, a proportional relief valve opens gradually as system pressure rises above the set point and closes again as pressure falls, which makes it well suited to protecting regulators, analyzers, pumps, test rigs and tubing from moderate overpressure. The Swagelok R3A covers set pressures from 50 to 6000 psig (3.4 to 413 bar) by selecting one of eight color-coded springs, and it is supplied with 1/4 in. or 6 and 8 mm end connections.

Seven Star LLC supplies the Swagelok R3A, its spring kits, seal kits and factory-set versions to oil and gas, petrochemical, power, water and laboratory customers in Oman and the GCC. Our Muscat team helps confirm set pressure, spring range, seal material and end connection, and we provide model selection support from Muscat.

Design Features

• External set pressure adjustment: the cap is turned to compress the spring, and a lock nut maintains the cap position after adjustment.
• Lock wire capability: the cap can be secured with lock wire so the setting cannot be changed without evidence of tampering.
• Quad seal on the stem: prevents leakage around the stem while the valve is relieving.
• O-ring seat seal: the Swagelok R3A uses an elastomer-to-metal O-ring seal for positive shutoff at the seat.
• Label on the cap: identifies the set pressure range of the installed spring.
• Gaugeable end connections: Swagelok tube fittings, NPT and ISO pipe threads.

Pressure Ratings

According to the Swagelok R series catalog, the Swagelok R3A has an inlet working pressure of 6000 psig (413 bar), with up to 8000 psig (551 bar) permitted during relief, and an outlet working pressure of 1500 psig (103 bar). Outlet pressure should not exceed inlet pressure. The fully open orifice is 0.14 in. (3.6 mm). The maximum set pressure is limited by seal material and temperature: with FKM, Buna N, neoprene or ethylene propylene seals the valve can be set to 6000 psig (413 bar) at moderate temperatures, falling to 5580 psig (384 bar) at 150°F (65°C), 5160 psig (355 bar) at 200°F (93°C) and 4910 psig (338 bar) at 250°F (121°C). Perfluorocarbon FFKM seals carry lower maximum set pressures, so always check the catalog table for the chosen seal.

Spring Ranges for the Swagelok R3A

Each high-pressure Swagelok R3A valve is set with the spring that covers the required set pressure, and the matching label is applied to the cap. Swagelok lists the following R3A springs, ordered with basic spring kit number 177-R3A-K1 plus the designator:

The Swagelok R3A can also be ordered factory set: Swagelok sets, tests, locks and tags the valve at the specified pressure and includes a certificate of test. The ordering number then carries -SET and the spring designator, for example SS-4R3A-SETB for a valve set within the 350 to 750 psig range.

Set and Reseal Performance

Swagelok defines set pressure as the upstream pressure at which the first indication of flow occurs. After initial relief, the set pressure of each valve is repeatable within ±3.0 psig (0.20 bar) or ±5 percent, whichever is greater, between 60 and 80°F (15 and 26°C), and within ±6.0 psig (0.40 bar) or ±20 percent outside that temperature band. Reseal pressure is always below set pressure. Every R series valve is tested for set and reseal performance; for the Swagelok R3A tested between 100 and 200 psig the minimum reseal is 50 percent of set pressure, and between 850 and 1000 psig it is 84 percent. The design of the high-pressure R3A and R4 valves minimizes the effect of system back pressure.

Ordering Numbers and End Connections

• SS-4R3A: 1/4 in. Swagelok tube fitting inlet and outlet.
• SS-6R3A-MM and SS-8R3A-MM: 6 mm and 8 mm Swagelok tube fittings.
• SS-4R3A1: 1/4 in. male NPT inlet with Swagelok tube fitting outlet.
• SS-4R3A5: 1/4 in. male NPT inlet with female NPT outlet; SS-4R3A5-RT for ISO threads.

Options for the Swagelok R3A include replacement seal kits in several elastomers, a manual override handle (kit SS-R3A-K5, for the A, B and C springs) that opens the valve without changing the setting, and SC-11 special cleaning to ASTM G93 Level C for oxygen and high-purity service. The Swagelok R3A is commonly mounted downstream of a Swagelok KPR series regulator to protect low-pressure equipment, with Swagelok 40 series ball valves for isolation and Swagelok tube fittings for the vent and inlet tubing.

Important Limitations

Swagelok states that R series relief valves do not have a capacity rating at a given accumulation and are not certified to ASME or any other code. They should never be used as ASME Boiler and Pressure Vessel Code safety relief devices and are not Safety Accessories under the Pressure Equipment Directive 2014/68/EU. Where a code-certified device is required, the system designer must select an appropriate certified safety valve. As general practice, pipe the outlet of a Swagelok R3A to a safe location, especially in toxic or flammable service, and verify the setting periodically because a valve that has not been actuated for a long time may relieve slightly above its set pressure on first opening.

Technical Specifications

How to Order

To order the Swagelok R3A, send Seven Star LLC the fluid, required set pressure, maximum temperature, seal material and end connections, and tell us whether you need a factory-set valve. Our Muscat engineers will confirm the ordering number against the Swagelok catalog and prepare a formal quotation. The Swagelok R3A catalog can be downloaded from this page, and we provide model selection support from Muscat across Oman and the GCC.