A gate valve opens a pipeline by withdrawing a gate across the flow passage. A threaded stem converts repeated handwheel turns into linear travel. Explore that motion here with an ideal straight gate crossing a circular bore, and compare how its projected opening changes with travel.
Gate Valve Interactive Calculator
Explore ideal multi-turn stem travel and the projected circular bore area uncovered by a straight gate, using entered bore, assumed full-stroke turns and current turns.
Equation Used
- Full gate stroke is assumed equal to one entered bore diameter.
- Entered full-stroke turns define an effective travel per turn, not an actual thread specification.
- The gate edge is idealized as straight across a circular bore.
- No Cv, flow, pressure drop, thrust, friction, seating, torque, strength, leakage or actuator sizing.
Ideal geometry only. 'Projected open area' is not Cv, flow rate or effective hydraulic area. Full stroke is assumed equal to one bore diameter, and the inferred lead is not a specified stem thread. No pressure, thrust, friction, seating, torque, strength, leakage or actuator model is included.
Multi-turn isolation motion
AVK describes a gate valve as a multi-turn valve operated through a threaded stem; when fully open, its gate leaves the flow channel unobstructed. Velan likewise identifies rising-stem gate motion and on-off service for a through-conduit design.
This calculator isolates only the ideal rotation-to-travel and projected-aperture geometry. It does not represent a particular valve's wedge, seats, stem thread or operator.
Teaching use
The model can show why many handwheel turns produce a linear lift and how the projected circular opening changes nonlinearly with gate travel. Selecting a real gate valve requires the manufacturer data and applicable piping, valve and service standards for the identified fluid, pressure, temperature and duty.
Ideal travel and projected aperture
Assume full travel equals one bore diameter D. If N entered turns span that stroke, the effective lead is D/N. At n turns, ideal travel is clamped to h=min(D,nD/N). The uncovered frontal area is the area of a circular segment of height h: A=r² arccos((r-h)/r)-(r-h)sqrt(r²-(r-h)²), with r=D/2.
A divided by the full circular area gives projected open-area percentage. This is geometry, not Cv or flow capacity.
Example: a 12 in bore and 60 turns
Assuming a 12 in full stroke over 60 turns gives an effective lead of 0.2 in/turn. At 30 current turns, travel is 6 in and the straight gate exposes half of the projected circular area.
At 15 turns, travel is 3 in, or one quarter of the assumed stroke, but projected open area is about 19.55%. At 45 turns, travel is 9 in and area is about 80.45%. Circular-segment geometry makes area change nonlinearly with travel.
At zero current turns the ideal gate is closed. Current Turns at or above Full Stroke Turns gives the full assumed opening and zero Turns Left. That numerical clamp is not permission to continue turning a physical valve after its travel limit.
Scope and limitations
Real valves may use solid or flexible wedges, parallel slides, slab gates, rising or non-rising stems and manufacturer-specific seats and bores. Hydraulic capacity requires certified valve data. Operating torque and actuator selection require differential pressure, actual stem and thread geometry, packing and bearing friction, seating/unseating loads, service factors and manufacturer limits.
Frequently asked questions
Is projected open area the same as flow capacity?
No. It is a geometric area fraction. Flow and pressure loss require the valve’s hydraulic characteristics and fluid conditions.
Does Stem Lead specify the actual screw thread?
No. The tool infers travel per turn from bore diameter and entered full-stroke turns. Full stroke is assumed equal to one bore diameter.
Why is the area at one quarter of travel less than 25%?
The opening is a circular segment. Near the edge of the circle, each increment of travel uncovers less width than near the centre.
What happens if Current Turns exceeds Full Stroke Turns?
The calculator caps travel at one bore diameter, displays 100% projected opening and zero remaining turns. It does not calculate physical overtravel or seating loads.
Can this size a handwheel or actuator?
No. It does not calculate differential-pressure thrust, packing or thread friction, seating force, operating torque or component strength.
Manufacturer technical context
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