Jan Kasprzyk, Vice - Chairman of SPETECH^®

Maria Libionka, Technical Sales Engineer SPETECH^®

Reducing air pollution originating from pipelines and process pressure equipment through the professional selection and installation of static sealing systems. For more than half a century, air quality regulations have been continuously developed worldwide. Following Poland’s accession to the European Union, such regulations also became applicable to Polish industry. The issue of fugitive emission reduction gained even greater importance after the introduction of the Industrial Emissions Directive (IED 2010/75/EU) in 2010, which imposes numerous obligations regarding atmospheric emissions.

These requirements are not merely formal in nature – they directly affect the design, manufacturing, and operation of pressure equipment. In practice, this means the need for a systematic reduction of fugitive emissions, one of the significant sources of which are flange connections and the static gaskets used within them. Errors at the stage of gasket material selection, determination of assembly parameters, or inspection of flange facing conditions may result in hazardous medium leakage, economic losses, risks to personnel, and regulatory sanctions.
The following article presents how, at every stage of the installation life cycle – from design, through manufacturing and assembly, to operation and maintenance – it is possible to effectively influence emission levels by using current calculation tools, standards, and engineering best practices.

Stage 1. Design

The design stage has the greatest and, in a sense, the primary influence on the future tightness of the installation. The currently applicable design approach (according to the EN 1591-1 model) requires the designer to define the leakage class of the flange connection. This is a key change compared to the “old approach,” where either American, Russian or German and all the others ‘national calculation standards’ effectively bypassed the issue of fugitive emissions, focusing mainly on strength calculations and ensuring operational safety of the connection.
It should be recalled that during the design stage, the designer specifies:

• the flange connection design type,
• flange and bolting materials,
• gasket type and material,
• loading forces and assembly parameters required for particular flange joint connection.

However, the introduction of the “new approach” under EN 1591-1 permanently changed design principles by treating the leakage class of the connection as equally important as the other critical requirements that pressure equipment must fulfill. This is precisely why the selection of a gasket with leakage performance parameters matching the calculation requirements is of crucial importance.
The EN 1591-1 standard describes an advanced stress-strain model of bolted flange joints and takes into account, among others:

• hydrostatic end force,
• internal pressure force,
• gasket seating force generated by bolting,
• friction,
• external forces and moments.

This makes it possible to predict the tightness of the connection already at the design stage, including the assessment of emissions for hazardous media. Gasket selection should consider not only price and availability, but above all:

• the required leakage class (=tightness level),
• durability under pressure and temperature conditions,
• chemical resistance,
• assembly limitations,
• the possibility or impossibility of future maintenance activities.

The “new approach” treats the issue of sealing systems so critical, that changing the gasket type in relation to the design documentation is considered a modification of the entire pressure device.

Stage 2. Manufacturing of Pressure Equipment

It may seem that a correctly prepared design, developed in accordance with the guidelines presented above, guarantees the manufacturing of a zero-emission device.
Unfortunately, practice often shows otherwise. The most common reasons are:
1. Inadequate quality of the flange connection manufacturing (including flange facing surfaces): the connection should be manufactured in accordance with the documentation, which, however, often does not specify the basic geometric characteristics critical for sealing performance, i.e. flatness deviation and surface roughness,
2. Non-compliance of installed gaskets with the design and technical standards: gaskets should be supplied in accordance with the specification, with quality documentation, undamaged, dimensionally compliant (especially tongue-and-groove and male-and-female gaskets), clean, dry, non-aged, non-corroded, etc.,
3. Poor quality of fastening elements (most commonly bolts or studs), which may also deviate from the design documentation.
In all three cases mentioned above, plant personnel lacking appropriate training are unable to identify potentially disqualifying defects, which has a decisive impact on the increase of equipment emissions during the many years of operation.
Although a hydrostatic test is performed after equipment assembly, its purpose is to verify the strength and correctness of assembly at the manufacturer’s facility. However, it does not provide information as to whether the tightness predicted according to EN 1591-1 has actually been achieved. Only in very rare cases is a gas tightness test carried out after the hydrostatic test using nitrogen or air, while modern emission standards increasingly require helium leak tightness as the benchmark.
Due to the above-mentioned risks, personnel performing such assembly should possess qualifications for flange joint assembly, enabling them to recognize critical characteristics of flanges, gaskets and bolting, as well as to follow proper assembly procedures. EU legislation addresses this need by requiring training for assemblers and supervisory engineers of flange joints according to EN 1591-4.

Stage 3. Equipment Installation on Site

At this stage, components critical for emission reduction, such as gaskets and bolting for connection nozzles, are delivered together with the equipment.

During installation at the operating site, the following are standard requirements:

• removal of transport protection,
• cleaning of flange facings from anti-corrosion protection,
• inspection of the geometric condition of flanges and flange facings,
• verification of the compliance of connection elements with the documentation.

Very importantly, the equipment should be supplied together with an assembly instruction specifying the tightening method (torque wrenches, hydraulic tensioners), tightening sequence, and the required torque or preload values.
And once again – in practice within EU countries, especially in the gas, refinery, and petrochemical sectors, certification of assemblers according to EN 1591-4 is required. This serves as a guarantee that the low-emission solutions adopted at the design stage will not be compromised by unqualified assembly work.

Stage 4. Operation – A Systematic Approach to Emissions

At this stage, the key factors for emission reduction include periodic inspections, response to leakages or damage, and the use of monitoring and early detection systems.
Taking the widely known “EU Methane Regulation” as an example – it imposes leak inspection cycles, including for flange connections, and requires repairs to be carried out within specified deadlines if permissible methane emission levels are exceeded. Although such procedures are not yet fully codified at national or European level for all media, similar approaches are increasingly applied to other hazardous or environmentally burdensome media.
However, an increasingly common approach is the implementation of a proceduralized LDAR system (Leak Detection and Repair) including:
1. identification of potential emission sources,
2. quantitative leak measurement,
3. corrective actions,
4. documentation and reporting.
A professionally implemented LDAR system significantly reduces fugitive emissions and medium losses. Due to its very high effectiveness, it is becoming increasingly popular in the chemical, refinery, gas, and mining industries.

Stage 5. Maintenance and Modernization

During maintenance shutdowns, a significant number of flange connections are dismantled. Reassembly requires the use of new gaskets and often also new bolting.
Reminder! Before every assembly, the condition of flange facing surfaces must be checked, as wear may require their regeneration or replacement.
Unfortunately, damage to flange facings caused during gasket removal by the use of tools such as chisels and hammers is still a common problem.
The identification of defects disqualifying flange facing surfaces is a competence of trained assemblers and supervisory engineers, enabling plant personnel to systematically reduce pollutant emissions.
If the condition of flange facings disqualifies them for gasket installation, such facings should be machined, for example using mobile “in situ” portable machining equipment, or, as a last resort, the flange should be replaced.
Maintenance shutdowns are also an opportunity for modernization – for example, by implementing higher tightness gaskets, adapting materials to new regulatory requirements (e.g. methane regulations), extending maintenance intervals, or unifying the gasket assortment within the plant.

Summary

Both from the formal regulations perspective and from the standpoint of engineering awareness, the issue of emission reduction is becoming increasingly important. In industrial pressure installations, this is additionally a multi-stage process involving:

• design,
• manufacturing,
• assembly,
• operation,
• maintenance and modernization.

The greatest influence on emission levels is exerted at the design stage, where – using calculation tools such as EN 1591-1 – it is possible to predict tightness performance and optimize flange connection construction.
However, manufacturers, installation operators, and maintenance services also contribute significantly to emission minimization. In this case, the qualifications of personnel (assemblers and supervisory engineers), the correctness of assembly procedures, and the systematic use of leak monitoring during operation are of crucial importance.

Reducing fugitive emissions is in the interest of operators (safety, reduction of medium losses, regulatory compliance) as well as the environment. Professional gasket selection, calculation-based verification, and proper installation of static sealing systems are key elements in achieving these objectives.

SPETECH^® Laboratory supports manufacturers and operators in verifying whether pressure devices and flange connections achieve the required emission performance levels. Advanced helium, methane and hydrogen leak detection methods, emission testing according to international standards, and engineering analysis allow the verification of sealing performance under real operating conditions.