FITOK GVSS-NS8-FNS8 Gauge Valve with Bleed, 1/2 in. NPT

GVSS-NS8-FNS8 is a FITOK ball-tip gauge valve in 316 stainless steel. It has a 1/2 in. male NPT process connection, a 1/2 in. female NPT instrument port and a 1/2 in. female NPT vent or test bleed port closed with a plug. The catalog lists 6,000 psig (414 bar) from -65 F to 450 F (-54 C to 232 C).

Isolating a pressure gauge with a bleed port

A gauge valve sits between the process and a pressure gauge or transmitter so that the instrument can be isolated, vented and removed without shutting down the line. This model has a ball-tip stem that closes on a seat, with a separate vent port for releasing trapped pressure before the instrument is taken off.

The code reads as GV for gauge valve, SS for 316 stainless steel, NS8 for the 1/2 in. male NPT process end and FNS8 for the 1/2 in. female NPT instrument end. The orifice is 0.157 in. (4.0 mm).

Catalog features

• Process, instrument and vent ports in a single compact body.
• Ball-tip stem for repeatable shut-off.
• Working pressure of 6,000 psig and temperature of -65 F to 450 F with PTFE packing.
• Vent plug supplied in the 1/2 in. FNPT test bleed port.

Technical specification

Specification of GVSS-NS8-FNS8

Gauge valve or manifold

Use a gauge valve when a single instrument needs isolation and a bleed point. Use a manifold when a differential pressure transmitter needs equalizing as well; the 3-valve manifold in this range does that. A gauge valve with a vent port is a lower-cost step above a plain isolation ball valve.

The vent port allows trapped pressure to be released safely before the gauge is disconnected. Pipe the vent to a safe place when the process fluid is toxic, hot or flammable, and replace the plug after use.

Size the connection to the gauge: many gauges have a 1/2 in. NPT back or bottom thread, but check the actual gauge and instrument thread before ordering.

Installation notes

Seal NPT threads with a sealant compatible with the fluid and tighten the male process end with a wrench on the body hex. Do not hold the valve by its handle when tightening.

Close the stem hand-tight. Use the vent port to confirm zero pressure on the instrument side before loosening the gauge. Support heavy gauges so that vibration does not load the valve body.

When the valve is used on a pulsating line such as a reciprocating pump discharge, fit a snubber or damper between the valve and the gauge. The valve passes the pulsation to the instrument, and an undamped gauge wears quickly.

Keep a spare vent plug and the stem packing in the maintenance stock, since the plug is a small part that is easily lost during instrument removal.

GCC applications

General engineering note: gauge valves with bleed ports are fitted at pump discharges, compressors, separators and pressure vessel nozzles in oil, gas, power and water treatment plants. Where salt air is present, a stainless steel body is preferred. Confirm process compatibility and the instrument connection against your datasheets.

Related FITOK items

The same catalog lists 2-valve, 3-valve and 5-valve manifolds. FITOK needle valves, ball valves and check valves in 316 stainless steel can be quoted for the impulse line.

Related FITOK products: FITOK 3DSS-FNS8-A 3-Valve Direct Mount Manifold, 1/2 in. NPT, FITOK NUSS-FNS2-7 Union Bonnet Needle Valve, 1/8 in. NPT, FITOK PVSS-FL2-02 2-Way Plug Valve, 1/8 in. FITOK Tube and FITOK NGSS-FL4-7-Y Panel Mount Needle Valve, 1/4 in. FITOK.

Documents and quotation

For quotation, send your required quantity and destination. The FITOK datasheet and user manual for GVSS-NS8-FNS8 are provided below the description on this page. Seven Star LLC works as an independent supplier from Muscat. Please compare code, ratings and options with the documents before you place an order; see also the category listing.