How industrial valves are made in India
Most industrial valves start as a cast or forged body and bonnet. Cast carbon steel bodies are common in larger gate, globe and check valves; small-bore valves and high-pressure classes are often forged. Many valve makers buy castings from foundries and forgings from forge shops, then machine, assemble and test in-house. That supply chain is where material mix-ups start: a CF8 casting where CF8M was ordered, or trim in a 400-series stainless where the order called for 316.
After machining, the valve is assembled with its trim (disc or ball, seat rings, stem), packing and gasket, then painted and pressure-tested on a hydraulic test bench with blind flanges or clamps. Every valve should be tested by the factory. Soft-seated ball and butterfly valves use PTFE or elastomer seats; metal-seated valves rely on lapped or hard-faced seats.
We have not found an official source naming an Indian valve cluster that we could confirm, so we name no town. Valve castings often come from the foundry clusters listed on the iron castings page.
What we check on industrial valves
| Check | How it is checked | What fails |
|---|---|---|
| Shell test | Valve partly open, body and bonnet filled with water and held at the shell test pressure for the standard's duration; inspector watches gauge, body, bonnet joint and packing | Any visible leak through the pressure boundary; gauge out of calibration |
| Seat tests | Low-pressure gas and high-pressure liquid closure tests, each side where the valve is bidirectional; leakage counted in drops or bubbles over the test time | Leakage above the rate allowed by the standard or rate named in the order |
| Backseat test | Where the design has a backseat, tested as the standard requires | Leak past the backseat |
| Material (PMI) | Handheld XRF analyser on body, bonnet, stem, disc or ball and seat rings, against the grades on the datasheet | Wrong alloy, e.g. CF8 instead of CF8M, 410 trim instead of 316 |
| Wall thickness | Measured at accessible points with a calibrated gauge and compared with the ASME B16.34 minimum for the class and size | Wall below the minimum |
| End connections | Flange drilling, facing and finish to ASME B16.5 or EN 1092-1; butt-weld bevels; face-to-face length to ASME B16.10 | Valve will not bolt or weld into the line |
| Operation | Full open to full close by handwheel, lever or actuator; torque feels even; position indicator correct | Sticking, binding or wrong indicator |
| Marking and records | Body marking and nameplate (maker, material, class, size, heat number); heat numbers traced to EN 10204 3.1 certificates | Marking that does not match the certificate |
Shell and seat tests, PMI and our role
API 598 covers inspection, examination and pressure tests for valves; ISO 5208 covers pressure testing of metallic industrial valves; EN 12266-1 is the European equivalent. ISO 5208 grades seat tightness by leakage rate, from rate A (no visible leakage) to looser rates, so the order must name the rate. API 598 sets its own allowed leakage by valve type and size. Test pressures follow the valve's pressure class; the shell test runs well above the rated working pressure.
The inspector selects valves from finished stock, checks the test bench gauges are calibrated, watches the full holding time and records valve serial number, pressure, duration and result. Many buyers require the shell test before painting, because paint can hide a weeping casting.
A handheld XRF analyser identifies most stainless and alloy grades, but it cannot measure carbon. It will not separate 316 from 316L or confirm a carbon steel grade; those need optical emission spectrometry at a lab, which we can arrange through lab testing coordination. Radiography or ultrasonic examination of castings is done by the factory's certified technicians or an outside agency; we witness it and review the reports. Where an independent NDT Level II technician is required, we arrange one and you should state it in the order.
Common defects in industrial valves
| Defect | Why it matters | Class |
|---|---|---|
| Shell leak through body or bonnet | Loss of containment in a pressurised line | Critical |
| Wrong body or trim material | Corrosion or failure in service; certificate does not describe the valve | Critical |
| Wall thickness below ASME B16.34 minimum | Valve may not hold its rated pressure | Critical |
| Heat number on body not traceable to a certificate | Material cannot be proven | Major |
| Seat leakage above the agreed rate | Valve will not isolate the line | Major |
| Flange drilling or face-to-face wrong | Valve will not fit the piping | Major |
| Fire-safe or PED claim without a covering certificate | Valve cannot legally or safely be used as sold | Major |
| Paint runs, minor casting marks on non-pressure faces | Appearance only | Minor |
Market rules and certificates for valves
- ASME B16.34. Covers pressure-temperature ratings, dimensions including minimum wall thickness, materials, testing and marking of flanged, threaded and welding-end steel valves. Marking follows MSS SP-25.
- Pressure Equipment Directive 2014/68/EU. In the EU, valves are pressure accessories. Small sizes may fall under sound engineering practice and carry no CE mark; larger ones are categorised by fluid, pressure and size, and above the lowest category a notified body is involved. We check the CE mark, notified body number and declaration of conformity against the valve; Great Britain has its own pressure equipment rules. See CE and UKCA marking.
- Fire-safe certificates. API 607 and ISO 10497 are fire type tests run on a valve design at an approved facility. We do not fire-test valves. We check that the certificate covers the design, size range, pressure class and seat material shipped.
- Material certificates. Buyers usually ask for EN 10204 3.1 certificates for body and bonnet. A 3.2 certificate needs the purchaser's or an officially designated inspector's validation; see EN 10204.
- Sour service. Where NACE MR0175 / ISO 15156 is ordered, hardness records for body, bolting and trim are reviewed.
Packing, transit and your purchase order
Valves must be drained and dried after testing, with flange faces and weld bevels covered by plastic or wooden end caps so faces are not dented. Ball valves are usually shipped in the open position to protect the seats; follow the maker's instructions for others. Stainless valves should not touch carbon steel in the crate. Crates must be ISPM 15 treated; see ISPM 15. The inspector checks end caps, valve position, tags and crate markings against the packing list.
Put these in your purchase order:
- Valve type, size, class, end connections and the design standard.
- Body, bonnet, trim, stem, seat and bolting materials, with the certificate type.
- Test standard (API 598, ISO 5208 or EN 12266-1), leakage rate and how many valves per size you want witnessed.
- PMI scope: which parts, how many valves.
- Fire-safe, fugitive emission or sour-service requirements and the certificates you expect.
- PED category and conformity documents for EU buyers.
- Marking, nameplate, paint system and end protection.
For flanges and fittings bought with the valves, see flanges and pipe fittings. Book an inspection anywhere in India.
Sources
- API Standard 598, Valve Inspection and Testing (American Petroleum Institute)
- ISO 5208:2015, Industrial valves: Pressure testing of metallic valves (iTeh catalogue)
- ASME B16.34, Valves: Flanged, Threaded, and Welding End (ASME)
- Directive 2014/68/EU on pressure equipment (EUR-Lex)
- Department of Commerce, TradeStat: commodity-wise exports (HS 8481, FY2025-26 provisional)