How to Identify Valve Manufacturer and Specifications from Valve Markings: A Complete Guide

Industrial valves carry a wealth of information stamped or cast on their bodies, bonnets, and nameplates. Being able to correctly interpret valve markings is an essential skill for maintenance technicians, plant engineers, and procurement professionals. This guide explains all standard valve markings, how to decode them, and what to do when markings are illegible or missing.

Why Valve Markings Matter

Valve markings are the primary means of identifying a valve's design conditions, material of construction, manufacturer, and date of manufacture. Correct identification is critical when ordering replacement valves, spare parts, or when performing maintenance. In regulated industries, being able to trace a valve to its original data sheet and test reports is often a regulatory requirement.

Required Markings per ASME B16.34 and API Standards

ASME B16.34 and API standards specify the minimum markings that must be present on a valve body. The required markings include: valve size; pressure class; material designation; manufacturer's name or trademark; and the temperature-pressure rating. Additional optional markings may include: heat number for material traceability; serial number; and month/year of manufacture. For valves in sour service, additional markings may be required to indicate compliance.

How to Read Valve Size and Pressure Class Markings

Valve size is typically marked as NPS for inch-system valves or DN for metric-system valves. The pressure class is marked as Class followed by the rating. Occasionally, DIN-standard valves are marked with PN ratings. When replacing a valve, the replacement must have the same NPS/DN and equal or higher pressure class. Always verify the flange standard in addition to size and pressure class.

Material Grade Markings and Their Meanings

Material markings indicate the ASTM specification and grade of the valve body and bonnet. Common markings include: WCB for carbon steel; LCB for low-temperature carbon steel; CF8M for stainless steel Type 316; and CF8 for stainless steel Type 304. For the stem and trim, separate markings may be present or documented in the valve paperwork. When the body marking is illegible, material identification can be performed using portable XRF analyzers.

Manufacturer Identification and Nameplate Information

The valve manufacturer's name, logo, or trademark is typically cast or stamped on the valve body. In addition, most valves carry a nameplate that provides more detailed information: manufacturer name; valve type and model; size and pressure class; material; serial number; and sometimes the month/year of manufacture. The nameplate is the most reliable source of valve identification information.

Heat Number and Material Traceability

The heat number is a critical marking for material traceability. It links the specific valve body to the original steel melt and to the corresponding mill test report. In the event of a material quality issue, the heat number allows tracing back to the steel mill. For critical service valves, heat number traceability is mandatory and is verified during inspection.

Identifying Age of a Valve from Markings

Many valves include a date code indicating the month and year of manufacture. The format varies by manufacturer. For valves without a visible date code, the valve serial number can sometimes be cross-referenced with the manufacturer's records. Knowing the age of a valve is important for life assessment and for determining remaining service life.

What to Do When Valve Markings Are Illegible or Missing

Plant maintenance teams sometimes encounter valves with illegible markings due to corrosion or painting. In such cases: first, attempt to locate the original plant documentation; second, measure the valve dimensions to narrow down the likely size and pressure class; third, use non-destructive material identification methods; and fourth, if the valve is critical, consider removing it from service for complete identification and possible re-certification.

Using Valve Identification for Spare Parts Ordering

Correct spare parts ordering requires accurate valve identification. The minimum information needed to order spare parts is: manufacturer name; valve model or type; size and pressure class; serial number; and a description of the required part. Providing the valve serial number is particularly important because manufacturers may make design changes over time.

Contact Wenzhou Wofer Valve for Valve Identification Support

If you have a valve manufactured by Wenzhou Wofer Valve Co., Ltd. and need identification assistance, please contact our support team with the valve nameplate information or photographs. We maintain complete records for all valves we have manufactured.

Ted Wang

Wechat/Whatsapp: +86 18267833722

Email: sales@wofervalve.com

Web: www.wofervalve.com

Wenzhou Wofer Valve Co., Ltd.