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How to meet the challenges of sealing chemical applications and comply with the amended TA Luft.

Environmental and climate protection in conjunction with safety and sustainability are top priorities at Garlock. Not only should our sealing solutions meet the high demands that science and legislation place on us and our products, we also see it as our duty to do the corresponding educational work and offer our know-how to our customers. After all, regulations and directives are anything but light fare and demand measures from companies in the chemical industry that must be met.

After seven years of discussions on drafts and votes on bills in the Cabinet and the Bundesrat, the time had come on 1 December 2021 and the new Technical Instructions on Air Quality Control (TA Luft) came into force. These essentially set ambient exposure and emission requirements for old and new plants. With the amendment, current Best Available Techniques were integrated and adjustments and additions to the state of the art were made.

What are the effects of the new regulation with regard to sealing and sealing material?

Basically, chapter 5.2.6 ff of the new TA Luft states that flange connections with welded metallic gaskets are to be regarded as technically tight by design. For other flange connections, reference is made to VDI2290 (June 2012 edition), in which all metallic flange connections below 400°C, which carry media listed in TA Luft, must provide proof of tightness according to tightness class L0,01 by means of mathematical proof of technical tightness in accordance with DIN EN 1591-1 calculation. If this is not possible, e.g. because no characteristic sealing values are available in accordance with EN13555, a new, modified component test or an equivalent method must be used, whereby the described “new” component test also specifies changes compared to the “old” component test.

The most important difference, apart from the changed test criteria, is now that the assembly must be tested in the real flange assembly from the field, under the real operating conditions of the plant (fastening, temperature, pressure, bolts, actual flange assembly, etc.).

In addition to a significantly increased number of different flanges to be tested, different pressure and temperature testing is now also necessary depending on the pipe class, as the materials do not behave uniformly.

Garlock GYLON^® sealing solutions – tested to EN13555.

Garlock GYLON^® Style 3504 requires only a minimum surface pressure of 9 MPa at 2 mm initial thickness within EN13555 testing to achieve a tightness of 1.0 x10^-2 [mg/(s×m)]. GYLON^® Style 3504 gaskets belong to the third generation of PTFE gaskets and, in addition to being calendered to stop cold flow and maintain surface pressure, have a modification with aluminosilicate spheres (also known as hollow glass micro spheres) to allow good conformability to the flange surface at low surface pressures.

GYLON^® Style 3504 has already passed tests according to the “new” component test with polypropylene (PP) flanges using a short welding neck and grooved sealing surface as well as using PVDF flanges, also with grooved sealing surface, without retightening.

GYLON^® Style 3504 was also able to achieve the new required limit value of 1.0 x10^-2 [mg/(s×m)] with a sufficiently high residual surface pressure in repeat tests.

Consultations with the chemical and petrochemical industry showed that GRP flanges can often withstand much higher surface pressures and are often mounted with up to 30 MPa. The tests were therefore repeated using a still conservative approach of 20 MPa mounting surface pressure. The result was consistently positive.

GYLON^® Style 3504 was also able to achieve the required limit value of 1.0 x 10^-2 [mg/(s×m)] in repeat tests with an excellent residual surface pressure for GRP flanges. Subsequent tests with a GYLON EPIX^® Style 3504 gasket material not primarily advertised for GRP also produced positive results.

Effects of TA Luft on “static” flange connections.

In the future, plant operators will have to pay more critical attention to the purchase of their components. If the flange connections are made of metallic material and are according to DIN EN 1092-1 or AMSE B16.5, for example, they are not difficult for TA Luft because they can easily provide proof of tightness using EN13555 characteristic values for sealing materials according to VDI2290 (June 2012 edition) with a DIN EN 1591-1 calculation.

In the case of “low-load” flange systems, where the flange assemblies are e.g. made of PP, PE, PVDF or FRP, testing will be necessary in accordance with the “new” component test (which is still to be agreed) and will involve the flange manufacturers and the provision of effective proof of strength by the manufacturers which will require validation in the subsequent testing.

In future, plant operators will have to ensure that their work standards include many types of gasket, if possible, when they are designed, also in cooperation with the flange manufacturer who produces the purchased part.

If entire systems are purchased, it must be ensured that the corresponding calculations are available and the strength verifications are provided by the manufacturers.

If you have any questions on the subject of TA Luft, please contact Garlock Application Engineering – our specialists will be happy to provide you with application-related and specialist advice.