Drawing legend · 27 terms defined

The legend sheet.

Every drawing set opens with a legend. These are the terms — and the drawing marks — this site uses.

HATCH = CUT METAL RED = SEAT / DATUM BLUE = FLOW

ANSWER

This glossary defines the valve and procurement terms used across the NF Teguh site — from body, bonnet, trim and seat to rising stem, wafer pattern, pressure class and material certificates. Each entry is a plain-English definition written for buyers and engineers preparing enquiries, not a standards quotation. Designations named here are reference data; the edition on your purchase order always governs.

Body: The pressure-retaining shell of a valve — the casting or forging the line bolts to. Body material (carbon steel, stainless, alloy) is specified separately from the trim inside it.
Bonnet: The removable top of the valve body, carrying the stem and its packing. On gate and globe valves the wedge or disc withdraws into it. Bolted bonnets are the maintainable norm; pressure-seal bonnets suit high pressure.
Bore: The flow passage through the valve. A full-bore valve matches the pipe's inside diameter — required for pigging; a reduced-bore valve is smaller, lighter and cheaper.

Class (pressure class): A pressure-temperature envelope — Class 150, 300, 600 — defined per material group in ASME B16.34, not a single working pressure. See the pressure class reference sheet.
Cv / K (flow figures): Published figures describing how much flow a valve passes and at what loss. K is the resistance coefficient used on this site's drawings — order-of-magnitude reference only; confirm against the manufacturer's data.

Disc: The moving element that closes against the seat — the wedge in a gate valve, the plug-shaped disc in a globe, the plate in a butterfly, the clapper in a swing check.
Double block and bleed: An arrangement — or a single trunnion ball valve rated for it — giving two seals with a vented cavity between, so isolation can be proven before work starts.

End connection: How the valve joins the line: flanged, butt-weld, socket-weld or threaded. One of the six lines every enquiry states.
EN 10204: The European standard defining material documentation types. Type 3.1: certificate from the manufacturer's own independent inspection. Type 3.2: adds an external or purchaser-appointed inspector. Ask on the purchase order.

Fire-safe: A valve that retains a defined degree of shutoff after a standard fire test — API 607 for quarter-turn soft-seated valves, API 6FA for API 6D valves. A tested property, not a marketing word.
Flange: The bolted rim joining valve to pipe. Drilling and facing follow the flange standard your line uses; the valve's class and the flange's class must agree.

Gland / packing: The sealed passage where the stem leaves the pressure boundary. Packing is the consumable seal inside it — the usual first maintenance item on a multi-turn valve.

Hard facing: Wear-resistant alloy applied to seats and wedge faces so the valve survives cycling against differential pressure. Specified as part of the trim.

Indent: Supply sourced against your order rather than from the shelf. A quotation from NF Teguh states, line by line, what is from stock and what is on indent.

Lug body: A butterfly valve body with threaded bolt lugs, so the line can be dead-ended or dismantled on one side. Compare wafer and double-flanged bodies.

NACE MR0175 / ISO 15156: The material standard for sour service — hydrocarbons carrying hydrogen sulphide. When a line names it, body, trim, bolting and welds must all comply, chiefly through hardness limits.

Operator: Whatever turns the valve: handwheel, lever, gearbox or actuator. One of the six enquiry lines — an actuated valve needs the mounting and signal stated too.
OS&Y (outside screw and yoke): Gate valve construction where the stem threads run in a yoke outside the pressure boundary: threads never touch the fluid, and the rising stem shows position at a glance.

Pigging: Sending a scraper or inspection tool through a line. Only full-bore, straight-through valves — gate, full-bore ball — pass a pig.
Pressure-seal bonnet: A bonnet design where line pressure tightens the seal — the high-pressure alternative to a bolted bonnet, common in power plant service.

Seat: The machined ring the disc closes against — drawn red throughout this site. Metal seats take temperature; soft seats give the tightest shutoff. Seat choice is trim choice.
Stem: The shaft connecting operator to disc. Rising stems show position; quarter-turn stems carry a lever or actuator pad.
Stockist: A supplier holding inventory and sourcing against specification — what NF Teguh is. One counter, six valve families, quoted from stock or on indent.

Trim: The valve's internal working parts as a set — seats, disc facing, stem, back-seat. Specified separately from the body, and the usual place a service condition (sour, abrasive, hot) is answered.
Trunnion: Fixed bearings holding a ball valve's ball in place, with spring-loaded seats riding against it — the large-size, high-class alternative to a floating ball.

Wafer body: A butterfly or dual-plate check body clamped between line flanges by through-bolts — lightest and cheapest, but the line must come apart to remove it.
Wedge: The gate valve's closing element. Solid: simple and strong. Flexible: tolerates thermal distortion — the steam choice. Split: self-aligning at moderate temperature.

A term you expected is missing? Ask the counter — contact sheet — and the legend grows.