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API 598 Test Parameters at a Glance
| Test | Purpose | Typical Pressure and Medium |
|---|---|---|
| Shell test | Prove that the body, bonnet and joints can withstand pressure without leakage | Water at 1.5 x the 38 °C rating |
| Back seat test | Prove that the back seat can seal the stem when the valve is fully open (gate and globe valves) | Water at 1.1 x the 38 °C rating |
| High-pressure closure test | Prove that the closed valve seals under high pressure | Water at 1.1 x the 38 °C rating |
| Low-pressure closure test | Prove that the closed valve seals at low pressure, which is harder for some seats | Air or inert gas at about 4 to 7 bar |
| High-pressure gas test (optional) | Extra check when specified by the customer | Gas at 1.1 x rating, with safety precautions |
Minimum test durations (typical, by nominal size)
| Valve Size | Shell Test | Seat (Closure) Test |
|---|---|---|
| Up to 2 inch (DN50) | 15 seconds | 15 seconds |
| 2 1/2 to 6 inch (DN65 to DN150) | 60 seconds | 60 seconds |
| 8 to 12 inch (DN200 to DN300) | 120 seconds | 120 seconds |
| 14 inch and above (DN350 and above) | 300 seconds | 120 seconds |
Durations above are typical minimums from the standard, and the exact values depend on the edition that applies. We confirm the edition on your order and apply the times specified. Some customers specify longer hold times, which we can follow.
Leakage criteria: for resilient-seated valves, such as ball valves with PTFE seats, no visible leakage is allowed in the seat test. For metal-seated valves, a small allowable leakage rate is given per size in the standard. We state which criterion applies to each valve on the test report.
Valve Range Supplied with API 598 Test Reports
API 598 is a test standard that sits behind many valve design standards. Because of that, a single order can contain several valve types, each with its own design standard, but all tested to the same procedure. We prepare one test report format for the whole order, so your document control is simpler.
| Valve Type | Design Standard Often Paired with API 598 | Size Range |
|---|---|---|
| Flanged and threaded ball valves | API 608, ISO 17292, MSS SP-110 | 1/2 inch to 12 inch |
| Bolted bonnet gate valves | API 600 | 1/2 inch to 24 inch |
| Small forged gate, globe and check valves | API 602 | 1/2 inch to 2 inch |
| Globe valves | BS 1873, ASME B16.34 | 1/2 inch to 12 inch |
| Swing and lift check valves | BS 1868, API 594 | 1/2 inch to 24 inch |
| Wafer and lug butterfly valves | API 609 | 1.5 inch to 24 inch |
| Plug valves | API 599 or manufacturer standard | 1/2 inch to 8 inch |
| Strainers | Manufacturer standard with shell test | 1/2 inch to 12 inch |
Why buyers ask for API 598 specifically
- Clear acceptance rules: test pressure, hold time and leakage are all defined, so there is no argument about what "tested" means.
- Common language: engineers, inspectors and purchasers in many countries know the standard.
- Easy comparison: valves from different suppliers can be compared on the same test basis.
- Audit support: test reports can be filed in the project quality dossier without translation.
If your project uses ISO 5208 or EN 12266-1 instead, we apply those, and explain the differences in leakage classes.
Related Standards and How They Fit Together
API 598 is part of a network of standards. A purchase order might say "API 598" and also mention design, flange, material and marking standards. Knowing how they connect makes specifications clearer and avoids conflicting requirements.
| Role | Standard Reference |
|---|---|
| Inspection and testing | API 598 (Valve Inspection and Testing) |
| Equivalent international test standards | ISO 5208 (pressure testing of metallic valves), EN 12266-1 and EN 12266-2 |
| Gate valve design | API 600 (bolted bonnet), API 602 (compact, forged) |
| Ball valve design | API 608, ISO 17292, API 6D |
| Butterfly valve design | API 609 |
| Check valve design | API 594, BS 1868 |
| Pressure-temperature ratings | ASME B16.34 |
| Flanges | ASME B16.5, ASME B16.47 |
| Marking | MSS SP-25 |
| Fire safe and emissions | API 607, ISO 15848-1 |
Edition matters. API 598 has been revised several times, and details such as test durations, acceptable leakage and test media change between editions. If your specification names an edition, we follow it. If it does not, we apply the current edition and state it on the test report.
API 598 is not the same as the API monogram. Testing a valve to API 598 means it was tested by the procedure of the standard. The API monogram is a licence held by specific manufacturers for specific products. We state clearly which one is meant when we quote.
Buyer tip: write the test requirement in your purchase order as "tested to API 598, edition and year", together with the required report type, for example individual reports by serial number. A short and exact line in the order avoids later arguments about what was tested, how long the valve was held under pressure and what documents should arrive with the goods.
Test Reports and Documents Provided
A test is only valuable when it is documented. A good test report lets your inspector see exactly what was done, with what equipment, and with what result. Our API 598 documentation is designed for that purpose, and it can be adapted to your own report format on request.
- Pressure test report: valve serial number, size, class, material, test type, pressure, duration, medium, result, date, operator and inspector signature.
- Gauge calibration record: gauge serial number and calibration date, so your inspector can confirm the instrument was valid.
- Test medium record: water quality note, including chloride control for stainless steel valves.
- Material certificate: EN 10204 3.1 for pressure-containing parts.
- Dimensional report: face-to-face, flange drilling and end dimensions, where specified.
- Marking record: body marking and nameplate data, per MSS SP-25.
- Fire safe and emission reports: available for selected designs.
- Quality management: ISO 9001 style system with batch records.
- Third-party witness: SGS, BV, TUV, DNV or the buyer's inspector can attend the test.
Individual or batch report? We can issue one report for each valve serial number, or a batch report listing all valves of one lot. Individual reports take more time, so please state your preference when placing the order.
A sample test report can be sent for approval before the order is confirmed.
Audit tip: file the test report, the gauge calibration record and the material certificate together for each valve lot. Inspectors often ask to see all three, and a matched set shows that the pressure test was carried out with valid instruments and on material that was verified. We can number the documents to match your purchase order lines.
Linking Test Results to Each Valve
A test report is useful only if it can be matched with the valve in your hands. We therefore link test results to serial numbers, heat numbers and production dates, so every valve can be identified and every result can be found again.
- Serial numbering: each valve receives a number, stamped, engraved or on a nameplate.
- Traveller sheet: the sheet follows the valve through machining, assembly and testing, with a space for each test result.
- Test bench record: the operator logs valve number, test type, pressure and time on the bench sheet.
- Inspector review: a quality inspector checks the record and signs it, before the valve moves to painting or packing.
- Report compilation: test reports are compiled by serial number and attached to the shipment documents.
- Retention: records are kept for several years, so duplicates can be issued on request.
| Item | Record | Purpose |
|---|---|---|
| Valve serial number | Stamp or nameplate | Unique identity |
| Material | Heat number and certificate | Proof of grade |
| Test | Pressure, time, medium and result | Proof of tightness |
| Gauge | Serial number and calibration date | Proof of instrument validity |
| Inspector | Name and signature | Accountability |
If a valve fails a test, it is tagged, repaired or scrapped, and then fully retested from the start. The first failed test remains in the record, so you can see our real quality history and not only the final pass.
Why the first failure stays on record: hiding failed tests would make a quality system meaningless. We keep the full history, including repairs and retests, so we can find patterns, such as a particular casting batch or seat lot, and take corrective action before problems reach customers.
Our Test Facilities and Procedure
Good testing needs the right equipment and the right discipline. We use hydraulic test benches with quick-clamping fixtures for each valve size, calibrated gauges with suitable range, and a clean test water system that is monitored for quality.
| Item | What We Use or Do |
|---|---|
| Test bench | Hydraulic pumps and clamping fixtures for sizes from 1/4 inch to large diameter |
| Pressure gauges | Calibrated gauges with range suited to the test pressure, with calibration dates recorded |
| Test water | Clean water with controlled chloride content for stainless steel valves |
| Air test | Compressed air or nitrogen at low pressure, valve submerged or soap solution applied |
| Drying | Valves drained and dried after testing to avoid staining or trapped water |
| Operator training | Trained operators following written procedures |
| Inspector witness | Quality inspector verifies readings and signs the record |
Procedure in brief
- Shell test: the valve is partly open, filled with water, pressurised to 1.5 times the rating and held for the required time, while the body, bonnet and joints are checked for leaks.
- Back seat test: for gate and globe valves, the valve is fully opened, the stem packing relieved if required, and the back seat pressurised to check sealing.
- Low-pressure closure test: the valve is closed, air is applied on one side, and the other side is checked for bubbles.
- High-pressure closure test: the valve is closed, water at 1.1 times the rating is applied on one side, and the other side is checked for leakage.
- Drying and cleaning: the valve is drained, dried and capped before painting and packing.
We welcome witnessed tests, and can provide photos or video of the pressure gauge and the valve during testing.
Frequently Asked Questions about API 598 Tested Valves
Q: What does API 598 cover?
It covers inspection, examination, pressure testing and acceptance criteria for gate, globe, check, ball and plug valves. It defines the shell test, back seat test and closure tests, including pressure, duration and leakage.
Q: Is API 598 a design standard?
No. It is a test standard. Design is covered by other standards such as API 600, 602, 608 and 609, which refer to API 598 for testing.
Q: What is the difference between API 598 and ISO 5208?
They are similar in purpose, and ISO 5208 and EN 12266-1 give leakage rates from A to G. API 598 defines leakage in drops or bubbles per minute by size. The results are comparable but not identical, so the standard should be named in the order.
Q: Why is there both an air test and a water test?
A low-pressure air test detects tiny leaks at low pressure, where the seat is not pressed hard. A high-pressure water test checks that the seat holds at working conditions. Doing both gives better confidence.
Q: Why does chloride in the test water matter?
Stainless steel can pit or crack if left wet with chloride-bearing water. Test water is therefore limited in chloride, and valves are drained and dried after the test.
Q: Can you test at a higher pressure than API 598?
Yes. Some customers specify 2 times the rating or longer hold times. We follow the specification and note it on the test report.
Q: Do you provide a test report for every valve?
We can provide individual reports by serial number, or batch reports by lot. Please say which you need when placing the order.
MOQ and Pricing for API 598 Tested Valves
All of our industrial valves are pressure tested before shipment, so API 598 testing does not normally add cost. The cost increase comes from extra reports, witnessing and special requirements, and we state them clearly in the quotation.
| Item | Typical Terms |
|---|---|
| Standard shell and seat test per API 598 | Included in standard price |
| Individual test report by serial number | Included for most project orders; small charge for very large quantities of small valves |
| Third-party witness | Charged at cost, plus our preparation time |
| High-pressure gas test or extended hold time | Quoted separately |
| Sample order | 1 to 3 pieces per model |
| Standard MOQ | 20 to 50 pieces per size; larger valves from 1 piece |
| Pricing basis | EXW, FOB Ningbo, CFR or CIF in USD |
| Payment | 30% T/T deposit, 70% before shipment; L/C at sight for approved accounts |
What affects the price
- Valve type and size: the main cost driver, not the test itself.
- Material: 316L and duplex cost more than 304.
- Reports: individual reports and extended documents take extra time.
- Witnessing: inspector visits need scheduling, and may add waiting time.
- Special tests: gas tests, fire safe tests and cycle tests are priced separately.
When comparing quotations, check that the supplier is actually testing every valve and not just a sample. Some low-price offers test only a percentage of valves, which can produce hidden failures in the field.
Ordering advice: if your project involves many valves of different types, ask us for a single test plan covering all of them. A common plan, with agreed hold times, media and report format, saves time at the order stage and avoids later confusion when inspectors review the documents and compare the results.
Lead Time, Customisation, Packaging and Trade Terms
Lead time and stock
Testing is part of normal production, so it does not extend delivery time for standard valves, which usually ship in 20 to 30 days. If your order needs witnessed testing, allow extra days to arrange the inspector. Large valves and special test requirements may need 35 to 60 days.
Customisation
We can customise test pressure, hold time, test medium, report format, marking, serial numbering, colour coding and documents. If your company has its own test report template, send it, and we will complete it for each valve.
Packaging
- Valves drained and dried after testing, with protective caps on ends
- Test status tag or label on each valve, when requested
- Cartons with dividers for small valves, wooden cases or pallets for large valves
- Reports packed in a document envelope inside the carton, and copies sent by email
- Neutral or customer-specified marking
Shipping and trade terms
| Term | Details |
|---|---|
| Incoterms | EXW, FOB Ningbo, CFR, CIF, DAP |
| Port | Ningbo-Zhoushan; Shanghai as an alternative |
| Transport | Sea freight, air freight for urgent items, express courier for samples |
| Documents | Invoice, packing list, bill of lading, origin certificate, material and test certificates |
We can send scanned copies of test reports before the goods leave our factory, so your inspector can review them while the shipment is in transit.
Handling advice: keep end caps on until installation, since valves are drained and dried after testing and should stay clean. Do not apply extra pressure to the valve before installation, and keep the test status label on the valve until it is fitted, so that site inspectors can see that testing has been completed before the system is commissioned.
