The EN 10204 3.1 mill test certificate and other screen quality documents

Quality documents for a wedge wire screen

A wedge wire screen can look correct on arrival and still be wrong in grade or slot. A screen in the wrong grade can pit in chloride service, and a screen with an oversized slot loses resin, gravel pack or filter media. The quality documents are the record that the material, the dimensions and the slot match the order.

Most disputes over a screen come back to what the purchase order asked for. The sections below describe each document a buyer can specify, what a complete one contains, and how to word the order so that each document is supplied. Documents that are not written into the order are rarely supplied in the form the buyer expects.

What an EN 10204 3.1 mill test certificate is

EN 10204 is the European standard for the types of inspection document supplied with metallic products. Mills, stockists and fabricators use it worldwide, including in India. It defines four types, which differ in who checked the product and what was checked.

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Type 3.1 is the normal requirement for the stainless wire, rod, plate and pipe in a screen, because it reports results for the heat supplied rather than for a typical heat. Type 3.2 is used where a third party must witness the material tests.

Mill test certificate, material test certificate, mill test report and MTC all describe the same document in practice. It should be specified by its EN 10204 type, since the name alone does not say who checked the material.

How to read a mill test certificate line by line

Layouts differ from mill to mill, while the content is the same. The table below shows an illustrative 3.1 certificate for 316L wire; the values are an example of a typical entry, not data for any real heat.

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Heat number traceability

The heat number, also called the cast number, links the certificate to the steel. The heat number on the certificate should match the tags or marking on the material, and the manufacturer should be able to trace it to each finished screen. A certificate whose heat number cannot be traced to the screen carries little weight.

Stockist certificates

Wire and rod often pass through a stockist, which may reissue the certificate on its own letterhead. A reissued certificate is acceptable when it carries the mill's original results and heat number unchanged and states the original document type. Where the application is critical, the mill's original certificate should be requested as well.

Checking chemistry against the grade

The grade box on a certificate is confirmed only by the analysis beneath it. Each element is compared with the limits in the material standard named on the certificate. The 316L limits from ASTM A240, the standard for stainless plate, sheet and strip, are as follows.

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ASTM A240 also sets minimum mechanical properties for 316L: tensile strength 485 MPa, 0.2 percent proof strength 170 MPa and elongation 40 percent. Three checks deserve particular attention.

1. Carbon defines the L grade. Carbon at 0.030 percent or below is what allows 316L to resist sensitisation at welds, so a certificate showing 0.04 percent carbon describes 316 regardless of the grade box. Dual-certified 316/316L material meets both sets of limits.
2. Molybdenum defines 316. Molybdenum between 2.0 and 3.0 percent gives 316 its pitting resistance over 304, and material below 2.0 percent does not qualify as 316.
3. The named standard governs. Wire and bar standards such as ASTM A580 and ASTM A276 set limits close to A240 but not always identical. EN 10088-2 grade 1.4404, the European equivalent, has a narrower molybdenum range of 2.00 to 2.50 percent, with chromium 16.5 to 18.5 and nickel 10.0 to 13.0 percent.

For duplex and super duplex grades, nitrogen is checked as well and PREN is calculated as %Cr + 3.3 x %Mo + 16 x %N. The material selection guide explains how PREN relates to chloride service.

Other quality documents for a fabricated screen

A mill test certificate covers the material only. The screen is a fabricated product, so its own records come from the screen manufacturer.

Dimensional inspection report

A dimensional inspection report compares each dimension on the approved drawing with the measured value. A complete report shows:

• the drawing number and revision;
• each dimension with its nominal value, tolerance and measured value;
• the instrument used and its calibration status;
• the inspector, the date and the screen identification.

For a cylinder, the key dimensions are outside diameter, ovality, length, straightness and end connections. For a panel, they are length, width, flatness and squareness, since ovality prevents a screen fitting the vessel and poor flatness leaves gaps through which media can bypass.

Slot record

The slot is the working dimension of the screen, so it is recorded separately. A slot record states the nominal slot and its tolerance, the number of readings, where they were taken and the method, followed by the minimum, maximum and mean values. Readings should be taken at set points along the length and around the circumference rather than at a single location.

Slot tolerance is usually stated on the drawing as a percentage of nominal slot. Feeler gauges are the standard method, with optical measurement used where a physical gauge cannot be inserted, for example on very fine slots.

PMI test report

Positive material identification (PMI) checks the alloy of the actual part rather than relying on the certificate. A PMI test is quick and non-destructive; ASTM E1476 is a guide to metal identification methods, and API RP 578 describes material verification programmes for piping. The method should be chosen with the grade in mind.

• Handheld XRF reads chromium, nickel, molybdenum and most alloying elements. It cannot measure carbon, so it cannot distinguish 316 from 316L.
• Spark optical emission spectrometry (OES) measures carbon but leaves a small burn mark, which matters on a finished slot surface.

A PMI test report lists each item, the reading, the expected grade and the result, together with the instrument and the operator.

Dye penetrant report

Dye penetrant testing detects surface-breaking cracks and porosity in fabrication welds such as flange, end ring and frame welds. The methods are set out in ISO 3452-1 and ASTM E165, while acceptance criteria come from the governing code or specification, for example ISO 23277 for welds. A complete report names the procedure, the penetrant system, surface preparation, dwell time, operator qualification, the welds tested, the indications found and the result.

Hydrostatic test certificate

A hydrostatic test applies only to a pressure-retaining part such as a strainer housing, a resin trap body or a vessel, because the screen element itself does not retain pressure. The certificate states the test medium, test pressure, hold time, gauge identification and calibration, the result and the witness. Test pressure and hold time are taken from the design code or the purchase specification.

Passivation certificate

Fabrication can leave free iron, scale and oil on stainless steel, and passivation removes them so that the protective oxide layer forms evenly. ASTM A380 covers cleaning, descaling and passivation of stainless steel parts, and ASTM A967 specifies chemical passivation treatments and the tests that verify them. A passivation certificate names the standard, the treatment (for example nitric or citric acid), the parts treated and the verification test, such as water immersion, high humidity, salt spray or copper sulphate.

Quality assurance plan and data book

A quality assurance plan (QAP), or inspection and test plan, lists each inspection stage with its method, acceptance criteria, record and any customer or third-party inspection (TPI) hold and witness points. A data book, also called a manufacturer's data record, collects every document for the order in one indexed file. A typical index is:

1. Purchase order and approved drawings.
2. Approved QAP, signed at each point.
3. Material certificates and a traceability matrix from heat number to item.
4. Welding procedures and welder qualifications for fabrication welds, where specified.
5. Dimensional inspection report and slot record.
6. NDT, PMI, hydrostatic and passivation reports, as applicable.
7. Certificate of conformity and release note.
8. Packing list.

The index, format and number of copies should be agreed before manufacture starts, since a data book assembled after dispatch is often incomplete.

Purchase order clauses for quality documents

Requirements are most reliable when they are written into the purchase order rather than a later email. Clauses such as these leave little room for interpretation.

1. Material certificates. "Inspection certificates to EN 10204 type 3.1 for all wire, rod, plate, pipe and flanges."
2. Traceability. "Heat numbers traceable to each item, with a traceability matrix."
3. Dimensional inspection. "Dimensional inspection report against the approved drawing for every item."
4. Slot record. "Slot measured at stated points along and around each screen, reporting minimum, maximum and mean against the drawing tolerance."
5. PMI. The scope (items and percentage) and the method, with OES specified where carbon matters.
6. NDT. "Dye penetrant testing of all fabrication welds to ISO 3452-1," with the required acceptance level.
7. Pressure test. For housings only: the code, test pressure, hold time and witness.
8. Passivation. "Cleaning and passivation to ASTM A967, with certificate."
9. QAP. "QAP to be submitted for approval before manufacture, with hold and witness points marked."
10. Data book. Contents, format, number of copies and due date.

The RFQ checklist covers the technical side of the same order.

SIMO Screens quality documentation

SIMO Screens supplies the Mill Test Certificate with every order as standard, and heat numbers are traceable from the MTC to the finished screen. Every screen is inspected dimensionally before dispatch, and the other documents below are supplied on request when they are listed in the enquiry.

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Our standard slot tolerance is plus or minus 5 percent of nominal slot, stated on the drawing. The slot is checked with feeler gauges at welding set-up, during the run and at the end of each screen, and optical measurement is used where physical measurement is not possible. Each screen is identified by a QR-coded tag carrying the job number, item and slot, and is laser marked on the screen where the client requires it.

The stage-by-stage plan is set out on the inspection and testing page, and the quality system on the quality page. List the documents you need with your enquiry and we will confirm each one in the quotation. Request a quote.