त्वरित जवाब
API 598 is the API inspection and pressure-test standard for gate, globe, plug, ball, check and butterfly valves. It defines visual examination, shell, backseat and closure tests, but it is not a certificate and does not replace the product standard. Before release, confirm the edition, the tests performed, the acceptance values and the serial or heat number behind each result.
What Is API 598?
API 598 is an inspection and pressure-test standard for new valves. It covers visual examination, supplementary examination and pressure testing, and it sets the method, test medium, hold time and allowable leakage for each test. Testing normally takes place at the manufacturer’s plant or at another facility agreed by both parties.
It is a companion standard. API 598 supplements the product standards that reference it, such as API 600 for steel gate valves and API 6D for pipeline valves. It does not define wall thickness, face-to-face length, material grade or pressure class. Those belong to the product standard and the purchase specification.
The standard also allows application to other valve types by agreement between purchaser and manufacturer. That is why the purchase order should say plainly which standard and which edition apply.
One practical point: API 598 is written for new valves. It is not a maintenance or in-service inspection procedure, and a report from a repair shop is not the same document as a manufacturer’s release test.
Which Valves Does API 598 Cover?
Scope follows two lines: seat construction and valve type.
On seat construction, the standard covers resilient-seated valves with soft seats such as PTFE or rubber, nonmetallic-seated valves such as ceramic, and metal-to-metal-seated valves.
On valve type, it covers gate, globe, plug, ball, check and butterfly valves. That is broad enough to cover most of a project valve list, which is why buyers see the same standard quoted across very different lines.
The test mapping is narrower than the scope:
- Shell tests apply to gate, globe, plug, check, floating ball, butterfly and trunnion-mounted ball valves.
- Backseat tests apply to gate and globe valves only.
- Closure tests apply to the same broad group, with low-pressure or high-pressure versions depending on size and class.
That middle line catches people out. A supplier who offers a backseat test on a butterfly valve, or who claims a backseat result for a ball valve, is describing something the standard does not require. For गेट वाल्व, the back seat is a normal design feature. For globe valves, the same applies. A floating ball valve has no back seat in the API 598 sense, so its report should show shell and closure tests instead.
Plug valves, cast steel check valves and wafer butterfly valves follow the same logic: shell and closure, with check valves treated separately at acceptance.
What Tests Belong in an API 598 Report?
Four test families should be visible, and each answers a different question.
Visual examination
Before any pressure is applied, the body, bonnet, cover and closure element are examined against the applicable standard. Casting surfaces are usually checked against MSS SP-55. This step catches porosity, cracks, mismatch and poor finish that a pressure test can miss or mask.
Shell test
The shell test pressurises the pressure-containing boundary with the closure open, so the body, bonnet joint and end connections are proved sound. API 598 also provides a high-pressure pneumatic shell test. A shell pass says the valve contains pressure. It says nothing about whether the seat closes.
Backseat test
The backseat test checks leakage past the stem or shaft to the back seat. It applies to gate and globe valves, where the back seat allows packing to be serviced while the valve is under pressure. It is not a packing test, and a pass does not prove the gland is leak-free in service.
Closure test
The closure test checks leakage across the seat with the valve closed. It comes in low-pressure, high-pressure and double block and bleed high-pressure forms. For a चोटा सा वाल्व, this is the test that tells you whether the valve isolates. For जांच कपाट, the standard applies separate leakage acceptance, because the disc seats on flow reversal rather than on an operator.
Test media follow the test type. High-pressure tests use air, inert gas, kerosene, water or a noncorrosive liquid no more viscous than water, normally between 5 and 50 °C unless the purchaser specifies otherwise. Low-pressure tests use air or inert gas.
The standard also sets pressure, hold time and allowable leakage by size, class and test type. Those values are not repeated here on purpose. The report should show the values it applied, and the buyer should check them against the edition in the order.
Is API 598 a Certificate?
No. Three documents get confused here, and the confusion has cost buyers money.
A test report is a record: this valve, this serial number, these tests, these readings, this date. A certificate of conformity is a statement that the product meets a specification. API 598 compliance is a design and test claim tied to a product standard.
API 598 does not certify a manufacturer, a quality system or a valve design. It does not replace API 6D for pipeline valves, API 600 for steel gate valves or API 609 for butterfly valves. It does not cover material certification, non-destructive examination, fire-safe testing to API 607 or API 6FA, or fugitive-emission testing.
That matters when a supplier sends a one-page “API 598 certificate” with no readings. The paper may be genuine, but it does not tell you which tests ran, at what pressure, with what result. Ask for the report behind it.
The same applies to check valves. A swing check valve built to API 6D carries a product-standard claim and a separate closure result. One document does not cover the other.
Which Edition of API 598 Applies?
Four editions are in common circulation:
- Eighth edition, May 2004.
- Ninth edition, September 2009.
- Tenth edition, October 2016.
- Eleventh edition, February 2023, the current edition.
Edition matters because test parameters and acceptance detail can change. A report that cites the eighth edition is not automatically wrong, but it is only right for an order that named the eighth edition. Problems start when the datasheet, the purchase order and the report cite three different editions.
The web makes this worse. Several widely read summaries still describe the ninth or tenth edition as current, because the page was written years ago and never updated. That is a useful reminder: a supplier’s website is not a controlled copy of the standard.
Put the edition in the RFQ and repeat it in the purchase order. Require the report to state the edition used. If a supplier proposes a different edition, agree it in writing before the order, not after the valves are packed.
How Should a Buyer Read the Test Report?
Read in four passes, in this order.
Identification. Valve type, size, pressure class, model, tag number, serial or batch number, heat numbers and the product standard. If the report cannot be tied to the units in the shipment, stop there. A mixed order makes this harder. A 2-piece ball valve order may cover hundreds of identical units, while a 3-piece ball valve order may include several bore and end-connection variants. The report needs a reference that matches the packing list.
Conditions. Test type, medium, pressure, hold time, temperature, acceptance criterion and edition. A result without conditions is not a result.
Readings. Measured leakage against the allowable limit, pass or fail by test, instrument identification and calibration date, test date, operator and witness. Units should be explicit.
Traceability. Heat numbers that close to material certificates, and references to any supplementary examination. Material grade claims are only as good as the certificate behind them, and our guide to valve materials explains how the common grades differ.
The table turns those four passes into a field-by-field check.
| Report field | What it proves | What to challenge |
|---|---|---|
| Valve identification | The report belongs to the shipped unit | Missing serial, tag or heat number |
| Edition | The test basis matches the order | A different edition from the purchase order |
| Test type and medium | The correct test was run | Closure test omitted, or the wrong medium used |
| Pressure and hold time | The test conditions meet the standard | Values below the required class |
| Measured leakage | The result is compared with an acceptance limit | Pass or fail with no readings |
| Traceability | The result closes to material certificates | Heat numbers that do not match |
| Witness record | Required inspection points were observed | Signature missing where the order required one |
Red flags that justify holding a shipment:
- “Tested to API 598” with no values.
- No edition stated.
- Closure results for one side only on a bidirectional valve.
- The same report reused across different serial numbers.
- Pressure below the value required for the class.
- Witness signature missing where the order required one.
- An end connection on the report that does not match the end connection on the valve.
- नॉमिनल डायामीटर: 1″～42″（DN25~1050）
- दबाव: 150एलबी-2500एलबी 0.6एमपीए-42.0एमपीए
- कनेक्शन समाप्त करें: आरएफ, आरटीजे, बीडब्ल्यू, टीएचआर, एसडब्ल्यू
- तापमान: -196℃-650℃
How Should You Review Traceability and Witness Requirements?
Traceability is the chain from the report back to the metal and forward to the shipment. At minimum, the heat number on the test report should match the heat number on the material certificate and on the valve marking. Where the order calls for supplementary examination, the report should reference it rather than imply it.
Witness and hold points are commercial terms, not standard defaults. Annex A of API 598 lists the information the purchaser is expected to supply, and witness requirements belong in that list. Decide before the order whether you need:
- notification before pressure testing;
- a hold point before the valve is painted or packed;
- a third-party inspector present;
- signed witness sheets returned with the report.
For a GOWIN API 600 gate valve, the back seat is part of the design, so a backseat test can be requested and traced to the serial number. GOWIN’s globe valve range also lists a back seat, which supports the same review. On a needle valve, expect shell and closure evidence instead, and confirm the test setup for the size and end connection ordered. For check valves, ask for the separate closure acceptance and for the swing-disc orientation shown on the drawing.
None of this requires a design engineer. It requires a purchase order that names the standard, the edition, the tests and the witness points, and a supplier who returns a report that answers each line.
निष्कर्ष
Accept a report when four things line up: the edition matches the order, every applicable test is listed with conditions and readings, the identification ties to the shipment, and traceability closes to material and examination records. If any one is missing, ask for a corrected report before release. A valve is not accepted because a test happened. It is accepted because the record proves which test happened to which valve.
If you are preparing an RFQ, name the test standard and edition, the tests you require, and any witness points.
Send service media, size, pressure, temperature and the relevant drawing for a quotation.
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