Clippard GNV-3R Bidirectional Needle Valve, 1/8 NPT

The Clippard GNV-3R is a compact bidirectional needle valve in the 1/8 inch NPT GNV-3 size, used to set the speed of pneumatic actuators by restricting flow in both directions. The needle and body are electroless nickel plated brass in an anodized aluminum housing, the needle is stainless steel in the GNV-3 series and the adjustment is a recessed slotted needle (the part page lists a screwdriver slot).

Setting actuator speed with a restriction

A needle valve controls the rate of flow by sending media through a variable orifice. The data sheet explains that screwing the threaded needle in blocks flow, so air not only decreases but backs up inside the actuator, preventing it from generating more pressure through resistance. Because flow is allowed in both directions, the GNV can slow an extend stroke, a retract stroke or both, and the same restriction can reverse the flow of a system or hold a constant flow rate. The ports rotate through 360 degrees, which makes the body easy to orient, and Clippard notes it works well with its Push-Quick fittings.

Technical specification

The same bulletin lists the larger GNV-4 at 45 scfm and GNV-5 at 60 scfm at 100 psig, and a flow-versus-turns curve for all three sizes showing GNV-3 as the smallest.

Picking a GNV suffix

The bulletin shows mounting as direct, in-line or cartridge style and adjustment as recessed slotted needle or knurled knob. The part list on Clippard’s site carries GNV-3K, GNV-3KC, GNV-3KI, GNV-3R, GNV-3RC and GNV-3RI, which suggests R and K select the adjustment and the C and I suffixes the cartridge and in-line bodies; this reading is derived from the listing, so confirm the code. For finer settings below this valve’s range, the same bulletin points to the MNV series with #10-32 ports and up to 5 scfm at 100 psig.

Fitting it correctly

Thread the valve directly into the actuator port using its 1/8 inch NPT thread and orient the side port by rotating it before locking. Fit a flow-control valve in the exhaust path to meter-out, or in the supply path to meter-in, depending on whether you want to control the load. Stay below 300 psig. Check which direction the fluid flows relative to the needle, since the valve restricts both ways and is not a one-way speed controller.

Applications and environments

Slowing small cylinders on packaging and assembly machines, damping pilot lines and setting purge rates are typical. Clippard cites plant and vegetable misting as an application of its needle valves. The nickel-plated brass resists corrosion in humid coastal sites, but the data sheet gives no approvals for hazardous areas. See also the Instrument Valves & Fittings range.

Related flow-control parts

Where the GNV-3 flow rate is too high for fine metering, Clippard’s MNV series needle valves offer #10-32 ports with different needle configurations for coarse or fine adjustment, at air flows up to 5 scfm at 100 psig, in in-line, direct or thread mounting. At the larger end, the GNV-4 handles 45 scfm and the GNV-5 60 scfm at 100 psig, with the 1/4 inch and 3/8 inch NPT styles. The bulletin’s flow chart plots flow against turns of the needle over ten turns, so the needle position can be used for repeatable settings once calibrated on your own circuit.

When you select between sizes, note that every flow figure in the bulletin is taken at 100 psig and that the flow-versus-turns chart plots GNV-3, GNV-4 and GNV-5 over ten turns of the needle, with the GNV-3 curve the lowest of the three. The GNV-3 is therefore the choice for small actuators and pilot lines, while the larger bodies suit bigger cylinders. Nitrile seals are standard and FKM is optional, so check the optional seal if the air supply carries oil or other aggressive media, and confirm the mounting style (direct, in-line or cartridge) before ordering.

GNV-3R questions

What port size does the GNV-3R have?

The GNV-3 size has 1/8 inch NPT with direct mounting and 360 degree rotating ports.

Does it control flow in both directions?

Yes, the data sheet describes bidirectional flow control.

What are the maximum pressure and flow?

300 psig input and 310 l/min at 100 psig, equal to 11 scfm.

What materials is it made of?

Nickel plated brass body and needle (stainless needle in GNV-3), anodized aluminum housing, nitrile seals.

Can it be used with water or oil?

Yes, the medium is listed as air, water or oil.

Using it in Oman and the GCC

Needle valves of this type are used in the region on packaging machines, automation equipment and test rigs to set actuator speed. Supply clean, dry, filtered air, as water and dust are common in compressed air in hot and humid coastal plants. Lock the setting after adjustment and record it, so replacement valves can be set the same way.

Fit a small filter upstream where the air quality is uncertain, because particles can block the fine needle setting.

Information to send with an enquiry

• Port size and needle type
• Quantity

Related Clippard products: Clippard SCPV-1-3 Stepper-Controlled Proportional Needle Valve, Clippard E2S10F-4W024 Media Isolation Solenoid Valve, 24 VDC, Clippard NPV3-1C-05-24 Solenoid Pinch Valve, 24 VDC, Clippard EC-P-10-09A0 EVP Proportional Valve, 2.7 l/min, Clippard EV-3M-12 3-Way Miniature Solenoid Valve, 12 VDC and Clippard MAR-1PK-3 Miniature Pressure Regulator, 10-30 psig.

Documents and quotation

The GNV data bulletin can be downloaded here. Seven Star LLC supplies Clippard valves from Muscat; send the part number and quantity for a quotation.