Authors:
Jan Kasprzyk, Technical Director SPETECH^®
Janusz Zajączek, Head of the Sealing Material Testing Laboratory SPETECH^®
 

This article describes the approach presented in ISO 15848-1 [3] and API 624 [7] as the main standards regarding the qualification of valves in terms of external sealing.

Evolution of valve emission regulations in EU

Currently, industrial emissions in the EU are regulated by the so-called IED directive [9]. It specifies the permissible emissions of various chemical compounds in different industries in detail. However, fugitive emissions from sources such as valve stuffing boxes or connections are not named in a document of this level.

At the same time, Germany has developed more detailed air protection regulations over several decades – Die Technische Anleitung zur Reinhaltung der Luft, abbreviated TA-Luft. These are federal regulations that specify permissible emissions quantitatively, pointing to specific technical solutions for industrial emissions released into the environment, including emissions from valves, pumps, compressors, and flange connections. For the sealing industry, including industrial installation operators, these regulations are valuable as they provide concrete specifics to the general requirements outlined in the IED directive. Although TA-Luft regulations are legally binding only in Germany, they are often adopted as technical guidelines or interpretations by numerous chemical, petrochemical, and refinery facilities across Europe.

In its latest edition, adopted in December 2021, TA-Luft refers to ISO 15848-1 as a document describing a qualification method for valves operating in hazardous media installations. Although this method is not mandatory per TA-Luft, its mention in this document is likely to increase its adoption both in Europe and beyond. At the same time, the use of the VDI 2440 document [2] (technical guidelines of the Verein Deutscher Ingenieure) may be limited. Until recently, VDI 2440 was the primary document for qualifying equipment such as valves, pumps, compressors, and gaskets as high-sealing, and it set quantitative sealing requirements. However, the testing methodology itself is described very generally. The practical outcome is that certification for compliance with VDI 2440 (and thus compliance with TA-Luft) can apply either to the stuffing-box packing alone (tested on a sealing test rig) or to the entire valve. The document does not provide detailed guidelines on the construction of the rig or the testing procedure itself. Consequently, certification to the standard always includes a test report detailing the construction, packing installation, and the test procedure.

Improvement provided by ISO 15848 standard

ISO 15848-1 came into force in 2006. It includes procedures for testing the external tightness of valves intended for volatile organic compounds and hazardous substances. The valve specimen is mounted on a test rig with the actuator. Helium or Methane is used as the test medium, and for both media, three tightness levels can be specified. The standard mandates separate testing of the stuffing box tightness (from which the tightness classes derive) and a separate check for acceptable (50 ppm) body leakage.

For testing the stuffing box tightness, a vacuum method using a helium spectrometer or an extraction method from a chamber surrounding the stuffing box outlet should be used. This second method can be applied to determine tightness for both helium and methane. The concentration of the leaking medium in the carrier gas can be determined using mass spectrometry, infrared absorption, or molecular scanning. For assessing body joint tightness, a method based on EPA Method 21 [8] is used. This involves measuring the concentration of leaking medium (helium or methane) with portable gas concentration detectors. For measuring this concentration, methods such as mass spectrometry, infrared absorption, or molecular scanning for helium and catalytic oxidation, flame ionization, infrared absorption, or photoionization for methane are suggested. The standard provides detailed calibration methods, instrument accuracy, and test procedures, distinguishing between control and shut-off valves with both rising and rotating shafts.

For ongoing production control of valve tightness, a related standard, ISO 15848-2 [4][5], has been created as the second part of the same standard number.

API 624 standard still the main regulation in US

API 624 [7] describes an assessment method and acceptance criteria for low-emission valves operating from -29°C to 538°C. It applies exclusively to shut-off valves with a rising or rotating-rising stem. The annex includes a list of valves recommended for testing according to this standard.
In this case, the reference medium is methane. The prerequisite for testing according to API 624 is the use of packings in the valve that have been previously qualified according to API 622 [6] (at least a report from these tests is necessary). The standard’s end users are the refinery and petrochemical industries, hence the acceptance criteria are limited to the requirements of this industry. The material selection for the packing (i.e., graphite) and the temperature requirements, as verified in the related API 622 standard, are geared towards these applications. The standard also includes requirements related to corrosion resistance, lubricant content, and inhibitors – typical requirements for the refinery and petrochemical industries.
Measurements are carried out both while the stem or shaft is stationary and while it is in motion (both static and dynamic). The test pressure does not exceed 600 psi, and the temperature is 260°C. The leak measurement method is EPA Method 21 [8], known as the “sniffing” method, which determines the concentration of volatile organic compounds in the air near the tested equipment.

Summary

The ISO 15848-1 standard is designed as a tool for qualifying valves for tightness based on criteria differentiating the quality of sealing, operating temperature, and durability of tightness. The standard can be used across the widest spectrum of valve applications, including both shut-off and control valves with either a rising stem or rotating shaft, intended for various industries and media. Tightness qualification is the sole subject of the standard.

API 624 was developed for the refinery and petrochemical industries and qualifies selected types of valves for their application by the end user. This qualification is multi-faceted; in addition to specified tightness requirements, it also imposes requirements such as specific corrosion resistance, designated materials for the packing construction, and defined thermal resistance.
Above two standards allow the suitability of valves to be defined and verified for use in areas requiring particularly high external tightness (thus, by default, such valves are used with hazardous media).
Thus, these standards are intended for different users and for different purposes. From the standpoint of tightness testing, ISO 15848-1 is much more developed, and its application is becoming more widespread.

References:
1.    Sealing Technology BAT guidance note (European Sealing Association)
2.    VDI 2440. Emission Reduction in Oil Refineries. Beuth Verlag 2000.
3.    PN-EN ISO 15848-1:2015-10. Industrial Valves - Measurement, Test, and Qualification Procedures for Fugitive Emissions - Part 1: Classification System and Qualification Procedures for Type Testing of Valves
4.    PN-EN ISO 15848-1:2015-10/A1. Industrial Valves - Measurement, Test, and Qualification Procedures for Fugitive Emissions - Part 1: Classification System and Qualification Procedures for Type Testing of Valves - Amendment to Standard [...]
5.    PN-EN ISO 15848-2:2015-10. Industrial Valves — Measurement, Test, and Qualification Procedures for Fugitive Emissions — Part 2: Production Acceptance Testing of Valves
6.    API Standard 622. Second Edition 2011. Type Testing of Process Valve Packing for Fugitive Emissions.
7.    API Standard 624. First Edition 2014. Type Testing of Rising Stem Valves Equipped with Graphite Packing for Fugitive Emissions.
8.    Method 21 Determination of Volatile Organic Compound Leaks, 8-3-2017
9.    European Parliament and Council Directive 2010/75/EU of 24 November 2010 on Industrial Emissions (Official Journal of the EU L 334, 17.12.2010, p. 1)
10.    https://www.epa.gov/emc/method-21-volatile-organic-compound-leaks