Gate, diverter and damper symbols
A knife gate valve is the valve bowtie with a vertical blade through it. A slide gate is a plate across a rectangular chute. A diverter is a Y with a flap that sends material one way or the other, and a damper is a duct with a diagonal blade. Unlike a motor, a gate on an HMI has two resting states, open and closed, and a third, travelling, that lives between them.
In short
- Knife gate: valve bowtie + blade, seals slurry in a pipe. Tag
XVorHV. - Slide gate: plate across a chute, stops dry solids, no pressure seal.
- Diverter: Y with a flap, two outlets, one active.
- Damper: duct + diagonal blade, modulates air or gas.
- HMI states: closed · open · travelling · fault · manual, driven by
ZSC/ZSO.
The common gate and damper symbols
These are the devices that start, stop or redirect a flow of solids or air. They sit at the outlet of every hopper and silo, under every conveyor transfer, and in every duct of a dust collection or combustion air system:
Related shapes reuse the same idea: a guillotine damper is a duct with a vertical blade, like the knife gate; a louvre damper is a duct with several short parallel blades; a pinch valve is a bowtie with a bar squeezing it. The valve guide covers the liquid families in detail.
Knife gate or slide gate?
They look similar in the field and are often both called "gates" on site, but they do different jobs and get different symbols. A knife gate is a valve: it lives in a pipe, its blade cuts through fibrous or settled material, and it seals against pressure. It is drawn with the valve bowtie and tagged like any other valve. A slide gate lives under a hopper or across a chute; it stops the column of dry solids from flowing but does not hold pressure. It is drawn as a plate across the chute outline, not as a bowtie. When a drawing shows a bowtie under a silo, check the legend: in bulk solids plants the two are frequently mixed up.
Tags and limit switches
On/off gates with an actuator take an ISA-5.1 valve tag: XV-101 for a solenoid-driven on/off gate, HV-101 for a hand-operated one, FV or LV when the gate is modulating flow or level. Dampers that modulate combustion air are usually FCV or PCV. What makes gates different from pumps on the HMI is the pair of position switches that report where the blade actually is:
ZSO-101: position switch, open. Makes when the gate reaches the fully open stop.ZSC-101: position switch, closed. Makes at the fully closed stop.ZT-101: position transmitter, for a modulating damper that reports 0 to 100 %.
Two switches give four combinations, and the HMI turns them into states.
From P&ID glyph to live HMI object
A gate is not a motor, so the nine motor states do not fit. The list for a two-position device is shorter and comes straight from the two switches and the command:
| State | ZSC / ZSO | Colour | Meaning |
|---|---|---|---|
| Closed | 1 / 0 | Gray, or the blade drawn across | Resting state, no flow. |
| Open | 0 / 1 | Green, or the blade drawn clear | Resting state, flow passes. |
| Travelling | 0 / 0 with a command active | Yellow, or a half-drawn blade | Moving between stops, within the travel time. |
| Fault | 1 / 1, or 0 / 0 after the travel time | Red | Both switches made, or the gate never arrived. |
| Manual | any | Blue | Operated locally, out of the sequence. |
| Disabled | any | Dark gray | Locked out. |
The colour is optional here. Many well-designed ISA-101 screens keep gates in neutral gray and show the position by geometry instead: blade across the chute for closed, blade lifted for open, half-way for travelling. Colour is then reserved for fault. Both approaches work; what matters is that "open" and "closed" never rely on colour alone, because a red/green pair is the first thing a colour-blind operator loses.
Diverters have two "open" states
A diverter gate does not open or close, it points left or right. Its resting states are position A and position B, each confirmed by its own switch, plus travelling and fault. Draw the flap as a separate element and show it in the outlet that is currently active. In the Symbol Builder you assign each flap drawing to its state, and the body stays the same in every state.
Geometry varies by project legend
ISA-5.1 gives the valve bowtie and the actuator marks; the chute, plate, flap and damper outlines come from ISO 10628 and company legend sheets. Some legends draw every gate as a bowtie, some draw slide gates as a rectangle with a diagonal. Read the legend sheet of the drawing set first, then match line weight and proportions when you draw your own.
Browse by category
Jump into the community library for the families on this page, or draw the set yourself:
Get gate symbols as PNG / SVG
Browse the gate and damper symbols published in the community library (CC BY 4.0) and download with a free account, 5 a month on Free, or draw a gate with its open, closed and travelling states in the builder. The builder is free to use, no account needed.
Open the builder → Browse community gate symbols →Frequently asked questions
What is the symbol for a knife gate valve?
The standard valve bowtie (two triangles meeting at a point) with a vertical line through the middle for the blade and a small rectangle on top for the actuator. It is tagged as a valve, XV-101 for an on/off gate or HV-101 for a hand-operated one.
What is the difference between a slide gate and a knife gate?
A knife gate is a valve in a pipe: it cuts through slurry and seals against pressure, and it is drawn with the bowtie. A slide gate is a plate across a chute or hopper outlet that stops dry solids without sealing pressure, drawn as a plate across the chute outline.
How many states does a gate need on an HMI?
Usually five: closed, open, travelling, fault, and manual or disabled. Closed and open come from the ZSC and ZSO switches; travelling is neither switch made while a command is active; fault is both switches made, or neither after the travel time.
What do ZSO and ZSC mean?
ISA-5.1 position switches: Z position, S switch, O open, C closed. ZSO-101 confirms gate 101 is fully open, ZSC-101 confirms it is fully closed.
Where can I download gate symbols?
Browse the community library (Gates) and download PNG or SVG with a free account, or draw one with its states in the Symbol Builder.
Keep reading
- P&ID valve symbols — bodies, actuators and fail-safe positions.
- Conveyor symbols — what feeds the gate and what it discharges onto.
- Tank, silo and hopper symbols — the vessel the gate sits under.
- Instrument symbols — the ZS bubbles around a gate.
- Build your own symbols — free online editor.
- Ask the community — a gate type your legend draws differently.