Swagelok SS-1RF4 Needle Valve, 0.73 Cv, 1/4 in. FNPT

The Swagelok SS-1RF4 is a 1 series integral-bonnet needle valve for fine throttling and shutoff of gases and liquids in instrument, sampling and analyser lines. It has a 316 stainless steel body, a regulating stem and 1/4 in. female NPT ports on both sides, and uses the live-loaded packing system that Swagelok fits to its needle valve range so that stem sealing holds up through thermal and pressure cycling.

Technical specifications

Regulating stem for repeatable throttling

A regulating stem has a long tapered profile, so many turns of the handle move the stem a small distance and flow can be set finely and repeated. With a 0.250 in. orifice and a maximum Cv of 0.73, the SS-1RF4 is the larger of the two 1 series orifice sizes; the catalog also lists a 0.172 in. orifice at 0.37 Cv under codes such as SS-1RM4 and SS-1RS4. Flow data in the catalog are given by turns open, which is useful for setting a sample flow without a flowmeter.

Cv is a flow coefficient at the fully open position, so it describes capacity rather than the setting for normal operation. For gas service, check whether the valve will be choked at your pressure drop.

Ratings, packing and testing

The catalog rates 316 stainless needle valves at 5000 psig (344 bar) from -20 F to 100 F, falling to 4295 psig at 200 F, 3875 at 300 F and 3435 psig at 450 F. These ratings assume standard PFA packing, which limits temperature to 450 F; PEEK packing options raise it to 600 F, and UHMWPE packing limits it to 250 F. Every integral-bonnet needle valve is tested with nitrogen at 1000 psig and the maximum allowable seat leak rate is 0.1 std cm3/min, with shell testing to no detectable leakage using a liquid leak detector.

Low-emissions certification to API 624 is available for the range, and this part is marked certified on the Swagelok data page. Cleaning follows Swagelok standard cleaning and packaging SC-10.

Ordering and decoding

In SS-1RF4, SS is stainless steel, 1 is the series, R is the regulating stem and F4 means 1/4 in. female NPT ends. Replace F with M for male NPT (SS-1RM4) or S for Swagelok tube-fitting ends (SS-1RS4), and the last digit with 6 or 8 for larger connections on the 18 series. Angle patterns, panel mounting and alternate handles are covered in the catalog options. Order the exact code and say if you need a bar handle, panel nut or a special packing.

Mount the valve with the stem accessible, tighten pipe threads with sealant, and tighten the packing nut only as the catalog instructs; the valve is a flow-control or shutoff device, not a pressure-relief or isolation device for high-integrity duty.

Typical applications

The SS-1RF4 is at home in the small-bore lines that surround process measurement. Common uses include setting the flow of a sample stream to an analyser, throttling a purge or bleed line, controlling the flow of a calibration gas, and providing a finely adjustable restriction in instrument tubing or pipework. The 316 stainless steel body suits a wide range of process media and plant environments, and the female NPT ends allow the valve to be fitted directly onto threaded nipples or male-threaded fittings in an existing assembly. Because the regulating stem allows the flow to be set and then repeated, the valve is particularly useful where an operator returns to the same setting after maintenance or a change of sample point.

Selection guidance

Start with the duty. If the task is to set a flow rather than simply open and close a line, the regulating stem is the right choice, and the flow data by turns open in the catalog can be used to estimate the setting. Next, compare the required flow with the Cv of the valve, remembering that a valve sized close to its fully open capacity leaves little room for adjustment. Then check the pressure and temperature at the installation point against the ratings above, taking the packing into account, and confirm that the media are compatible with 316 stainless steel and with the packing material. Finally, confirm that 1/4 in. female NPT ends match the adjoining pipework; if not, the decoding section shows which part of the code changes for other end connections.

Installation and commissioning considerations

Install the valve where the handle can be reached comfortably and the setting can be seen, and support the adjoining pipework so that the valve body does not carry piping loads. Follow the flow direction shown in the catalog if one is indicated for the pattern. After installation, pressure test the line according to site procedures before putting it into service. When the line is commissioned, open the valve slowly from the closed position and set the flow while observing the downstream instrument, then record the number of turns open so the setting can be restored after future work. Check the packing area for leaks during the first period of operation.

How to specify your RFQ

Send the part number SS-1RF4, the quantity and the delivery point. Mention the medium, the operating pressure and temperature, and whether any catalog option is required. If you are replacing an installed valve, a photo of the body marking helps us confirm the exact code before quoting.

Documents and quotation

This page links the official Swagelok integral-bonnet needle valves O, 1, 18, 20 and 26 series catalog MS-01-164 (EN), which holds the ordering tables, ratings and materials behind the figures above. Seven Star LLC is an independent supplier in Muscat; for a quotation on SS-1RF4, tell us the quantity and any option you need, such as handle, packing or special cleaning.

Confirm the full order code, including any suffix, with your piping drawing before you order; similar codes are easy to mix up. Related items: product category.