Walk through any working refinery, power plant, or desalination train and you will see hundreds of industrial valves doing five very different jobs. Some are sitting fully open, just letting crude or steam pass. Others are half-closed, trimming the flow to a delicate setpoint. A few slam shut the moment flow reverses. Pick the wrong geometry for the wrong service and you get pressure ｄｒｏｐ you did not budget for, water hammer, or a maintenance call you did not want. After three decades of shipping pipe, fittings, and valves to projects from the West-East Gas Pipeline to offshore shipyards, EZ STEEL INDUSTRIAL has learned that the cheapest valve on the quote sheet is rarely the cheapest valve on the job. This guide maps the seven valve types you will see on most inquiry documents and shows how they fit into a complete piping package.

The five jobs a valve is asked to do

Before a buyer ever looks at a part number, it helps to know which job the valve has been hired to do. Almost every industrial valve on a process line falls into one of these functions:

• Isolation – fully open or fully closed. Maintenance, section shutdowns, and emergency block.
• Throttling – modulating position to hold a flow, pressure, or temperature setpoint.
• Backflow prevention – stopping reverse flow that could damage a pump, compressor, or prime mover.
• Overpressure protection – opening at a set pressure to keep vessels, headers, and lines within their design envelope.
• Diverting or mixing – multi-port designs that route flow between headers or blend two streams.

That function list, more than the brand or the price, drives every choice that follows: body geometry, material, end connection, and the standards that govern the test package.

The seven valve types you will see on most RFQs

1. Gate valves

The workhorse of crude, gas, and steam isolation. A gate valve slides a wedge fully out of the flow path for full-bore, low-pressure-ｄｒｏｐ service. It is built for on/off use only – leaving a gate valve half-open will erode the seat in a matter of weeks. Buyers specify API 600 or API 603 for refinery service, and API 6D for cross-country pipelines.

2. Ball valves

A quarter-turn ball with a bored-through port. Ball valves are the go-to for fast shut-off, piggable lines, LNG, and sour service. Soft-seated designs give bubble-tight shutoff at moderate temperatures; metal-seated variants handle high-temp boiler duty. For abrasive slurry, consider a fully lined ball or step up to a different geometry.

3. Globe valves

The throttling specialist. A globe valve raises or lowers a plug against a horizontal seat, giving accurate flow control on fuel gas, chemical dosing, and cooling water. The trade-off is a higher pressure ｄｒｏｐ than gate or ball designs, so you size the pump or compressor accordingly.

4. Check valves (non-return)

No handle, no actuator – just a disc that opens with forward flow and snaps shut when flow reverses. Check valves protect centrifugal pumps from backflow on shutdown and keep compressor discharge from feeding back into a tripped line. Swing, lift, dual-plate, and axial (nozzle) designs cover most line sizes; water-hammer risk dictates which one is appropriate.

5. Butterfly valves

A disc that rotates a quarter turn inside the bore. Butterfly valves shine on low-pressure water, air, and fire-protection mains where their light weight and low cost matter more than ultimate shutoff. Concentric (resilient-seated) designs work for utility water; high-performance double-offset or triple-offset designs extend into hydrocarbon and higher-temperature service.

6. Plug valves

A tapered or cylindrical plug with a straight-through port. Plug valves give bubble-tight shutoff on slurry, viscous fluids, and multi-port manifold service – common on wellheads, tank farms, and chemical dosing skids. Lubricated and sleeved-plug designs reduce the operating torque on larger sizes.

7. Safety and relief valves

The last line of defense on a pressure system. A spring-loaded safety relief valve pops open at a set pressure, bleeds off the overpressure, and reseats. These are mandatory on fired heaters, boiler drums, compressor stations, and any vessel that can be blocked in with a heat source. Each one is capacity-certified and stamped – do not substitute a generic ball valve here.

Quick comparison of the seven types

Material selection: matching the body to the fluid

Picking the geometry is only half the job. The body, trim, and seat material decide whether the valve survives its first year in service. A few rules of thumb that line up with what our mill-direct inventory supports:

• WCB carbon steel covers the bulk of hydrocarbon service between -29 °C and 425 °C.
• LCB and LCC extend carbon steel down into low-temperature duties (-46 °C).
• CF8 / CF8M (304 / 316) stainless grades handle most chemical, food, and seawater-adjacent service.
• Duplex and super-duplex are specified for offshore, chloride-rich, and high-pressure sour gas service.
• Alloy 20, Monel 400, Inconel 625/825 come in for sulfuric acid alkylation, hot chloride brine, and wet sour gas.

If the valve ties into a heat exchanger or boiler, the same corrosion logic should drive the trim. Stainless heat efficiency tubes paired with a stainless body valve and PTFE or graphite seats is a proven combination for utility and chemical plants.

Valves never ship alone: the supporting cast

A valve on a P&ID is one symbol, but on a real bill of materials it pulls a stack of companion products with it. Getting them from one supplier, in one shipment, with one set of MTRs is the easiest way to keep a project on schedule.

• Pipe fittings – elbows, tees, reducers, and caps that route the line into and out of each valve. Material and schedule must match the line pipe.
• Pipe flanges – sized to the same ASME class as the valve body so the gasket and bolting line up on site. RF for water and utility, RTJ for high-pressure hydrocarbon.
• Gasket stud bolt nut – spiral-wound gaskets for refinery service, ring-joint gaskets for high-pressure headers, and the matching stud bolt / nut sets in the right ASTM or A193/A194 grade.
• Line pipe – ASTM A106, A53, A312, and API 5L grades in the right schedule, all traceable to the same mill heat.

Sourcing the full package from a single vendor reduces the risk of mismatched facing, mixed certificates, and the consolidation delays that hit schedules hardest. EZ STEEL stocks the eight supporting categories – carbon and stainless steel pipe, copper-nickel alloy, fittings, flanges, gaskets, and valves – so a single RFQ can cover an entire line class.

The standards and test package behind every shipment

A datasheet is only as good as the documents that back it. The codes that come up most often on inquiry documents, and the tests that go with them, are:

• API 6D – pipeline gate, ball, check, and plug valves.
• API 600 / API 602 / API 603 – bolted-bonnet and forged gate valves for refinery and high-temperature service.
• API 598 – the valve test procedure referenced on almost every MTR.
• ASME B16.34 – pressure-temperature ratings for steel valves.
• ISO 14313 / ISO 10434 – international equivalents for cross-border projects.
• NACE MR0175 / MR0103 – mandatory for sour (H₂S) service.
• EN 593 – European butterfly valve standard.

The minimum test package any serious supplier should ship with each valve includes a body hydrostatic test at 1.5× rated pressure, a seat leakage test per API 598, a backseat / stem seal test, an operation torque check, and NDT on critical welds. For LNG, fire-safe, and low-emission service, add cryogenic testing (BS 6364), API 607 / API 6FA fire exposure, and ISO 15848 / API 624 fugitive emissions certification. EZ STEEL's ISO 9001 lab runs all of these in-house, and the certificates travel with the shipment so QA can close out the file without chasing paperwork.

A short checklist before you send the RFQ

1. State the fluid, including trace H₂S, CO₂, chloride, and water content.
2. Confirm design pressure, design temperature, and the required ASME class.
3. Decide the function – isolation, throttling, check, or safety relief.
4. Pick the standard set (API 6D, API 600, ASME B16.34) and any project add-ons (NACE, fire-safe, low-emission).
5. Choose body, trim, and seat material based on corrosion data, not just price.
6. List the test certificates and third-party inspections you need to receive with shipment.
7. Bundle pipe, fittings, flanges, gaskets, bolting, and valves where possible to simplify logistics.