Mechanical Seals Division

One of the most effective ways of sealing rotating shafts is by mechanical seals. These consist of two plane faces arranged perpendicular to the axis of the rotating shaft (which gives rise to the alternative name, "radial face seal"). One face is fixed to the equipment casing or vessel, while the other is fixed to the shaft and so rotates with it. Frictional heat generation and wear are controlled by maintaining a film of lubricant between the seal faces. As such, mechanical seals resemble thrust bearings.

Mechanical seals have replaced packings as the seal of choice in many applications, primarily because mechanical seals offer:

• reduced wear (from lower friction)
• reduced heat generation (from lower friction)
• lower energy consumption (from lower friction)
• reduced maintenance requirement (from reduced wear)
• tighter control of shaft leakage (from extremely low or zero fluid emissions)

See ... List of Division Members

Mechanical seals are precision devices, requiring in general more careful installation and higher initial investment than those of soft packings.

ATEX Directive 94/9/EC

The ATEX Directive (also known as "ATEX 95") - "Equipment and Protective Systems intended for use in potentially explosive atmospheres" - has been mandatory since 2003 July 1. Despite this, the interpretation of how this Directive applies to mechanical seals is still largely misunderstood. Consequently, the Members of the ESA Mechanical Seals Division have developed a Position Statement to act as a guidance towards clarification.

To download (as a pdf file) please click .. ESA Position Statements

Machinery Directive 98/37/EC and 2006/42/EC

Members of the ESA Mechanical Seals Division consider that mechanical seals are not covered by the original or new Directive. A Position Statement is available for clarification.

To download (as a pdf file) please click .. ESA Position Statements

Pressure Equipment Directive 97/23/EC

The ESA has sought advice from sources across Europe, including the Verein Deutscher Maschinenbau-Anstalten e.V. (VDMA, Germany) and the Department of Trade and Industry (dti, United Kingdom) regarding the implications of the Pressure Equipment Directive (PED) for mechanical seals. A Position Statement is available for clarification.

To download (as a pdf file) please click .. ESA Position Statements

Sealing Technology BAT guidance note

Sealing technology is involved in virtually all of the sectors covered by the EU IPPC Directive. Yet, only limited information and guidance on sealing options is available in most of the BREF notes which have been published. For this reason, the ESA has published a Sealing Technology BAT guidance note, with sections covering the best available techniques for sealing solutions required to meet the IPPC legislation.

Seal Forum

This document is a compilation of technical papers from leading rotating equipment engineers across the globe, providing a balanced view of mechanically-sealed and sealless systems in a wide range of applications. The user experts give unbiased reports about their own experience with the various options available for rotating equipment. This is a "must read" for all rotating equipment users!

The document is a joint ESA+FSA publication, available in English and German language versions.

Other documents

Member Companies have an ongoing commitment to research and development. This has resulted in the continually increasing performance of mechanical seals, reflecting state-of-the-art technology which has been used in the design of seals available in the marketplace today. In anticipation of increasing environmental regulations, new generations of mechanical seal products have been developed to provide cost-effective solutions for the control of emissions. Increased life of 3+ years has been attained reliably with low emission single seals and dual seals. These results have been obtained through the use of improved designs, high quality face materials, attention to manufacturing and assembly details, and enhanced seal chamber environment. These advances in seal technology go hand in hand with improved installation, maintenance and operating procedures, to enable considerable reductions in fugitive emissions and hence substantial savings for the operator.

Most of today's low emission single mechanical seals, using modern materials and advanced technology, are performing reliably with emissions typically below 1g/h under normal operating conditions in the field.

Emission from today's dual mechanical seals with barrier fluids is essentially zero, usually described as "not measurable with existing instrument technology". These seal arrangements can provide very tight emission control, meeting the requirements of the most stringent environmental legislation world-wide. These performance levels have been supported by independent users over extended periods of operation in the field.

In recognition of these developments, the Mechanical Seals Division has prepared a document to provide information and guidance on:

• performance of modern, low emission mechanical seals
• application recommendations
• achievement of environmental legislative requirements

This document is for use by original equipment manufacturers, engineering contractors and end users in the process industries. It is entitled, "Meeting emission legislation requirements with today's advanced technology mechanical seal systems"(ESA Publication No. 005/95).

Although much of this 1995 document continues to be relevant to current practice in mechanical sealing, the Sealing Technology BAT guidance note (mentioned above) covers the same subject and, in addition, brings the topic up to date. Consequently, the BAT guidance note should be used as the primary document when considering the latest technology options for managing fugitive emissions in mechanical seals.

Recommendations for safe shaft sealing from ESA Publication No. 005/95:

Area	Leak rate maximum (g/h)	Specific gravity of process fluid	Acceptable sealing solution
1	2.5 - 24	>0.4	- general purpose single seals - advanced technology single seals - dual unpressurised (tandem) seals - dual pressurised (double) seals
2	0.5 - 2.5	>0.5 - 0.7	- advanced technology single seals - dual unpressurised (tandem) seals - dual pressurised (double) seals
3	<0.5	>0.4	- advanced technology single seals vented to a closed vent system - dual unpressurised (tandem) seals vented to a closed vent system - dual pressurised (double) seals
		<0.4	- dual pressurised (double) seals