Packing density – Describes the density of a knitted wire mesh used as demister. Classic packing densities are 145 / 192 / 240 kg/m³ for stainless steel and 80 kg/m³ for plastic. Depending on the packing density, this results in a free volume (%) and the specific surface (m²/m³).
Packing specification – The term packing specification is also known as knitted fabric specification. The packing specification is made up of the packing density, the material and the wire diameter. At STRIKO for instance, it is specified in the following form: 9192-ss-0,28. The degree of separation, the diameter of the minimum droplet size, the density and viscosity of the liquids as well as the flow speed, they all have an impact on the specification and the dimensions of the knitted fabric. The decisive variables are the packing density and the wire diameter. Knitted fabrics with high packing density and low wire diameter exhibit a high separation efficiency but have a low flooding point. Via the continuity equation, the surface area of a knitted wire and the prevailing volume flow lead to an optimal surface area cross-section and in turn to an optimal flow speed. This results in the best-suited packing specification and an optimal surface area for each specific application. The height of the knitted fabric has a comparatively small influence both on the separation efficiency and the pressure loss. It serves much more as a reserve, for instance if any remaining solid content is not known or has not been precisely defined.
Pre-loaded holder – STRIKO standard bursting disc holders in intermediate flange design only reach a fixed and dense clamping of the bursting device after tightening the flange screws. This means that after loosening the flange connection also the metallic seal between the bursting disc and the holder is removed. With STRIKO pre-loaded holders PRO for bursting discs of the series SZ and SU however, the required tightening torque for secure and dense installation of the bursting disc is already applied by the high-strength preloading screws when installing the bursting disc into the holder. Thus it is possible during machine downtime to loosen the flange connection and perform a visual inspection, to clean or even carry out the required replacement of the flange seals without the need to insert a new bursting disc. This shortens downtimes following a reaction of a bursting disc by up to 80%. The use of pre-loaded holders is particularly recommended for sensitive steel-enamel / glass and plastic pipes, polymerisation processes, in case of a tendency towards caking, unfavourable installation positions and frequent replacement of bursting discs.
Pressure equipment directive 2014/68/EU – The pressure equipment directive PED (German abbreviation DGRL) is a harmonisation guideline for aligning pressure equipment to the regulations of the EU member states specified by the European Parliament and Council in May 1997 according to article 95 of the EG treaty for the free movement of goods. It regulates the requirements for bringing pressure equipment onto the market within the European economic area and must be put by each and every member state into national legislation. The pressure equipment directive has been binding in the entire European Union since 2002. According to the directive, pressure equipment are to be classified in terms of pressure and volume (for piping in terms of nominal size DN) as well as fluid group and state of aggregation. On June 27th, 2014 the Official Journal of the EU L 189 published a new pressure equipment directive (German abbreviation DGRL). The directive 2014/68/EU replaces the old DGRL 97/23/EG. To a large extent, the fundamentals of the DGRL remain preserved. With regard to the scope and the conformity assessment diagrams there are just a few small changes. Existing certifications retain their validity. With respect to the updates two pieces of information are decisive: Parts of the new DGRL 2014/68/EU have already been effective since June 1st, 2015. Other points have been binding since July 19th, 2016. Since this reference date the use of the old directive is no longer permissible. Updates since June 1st, 2015: a) Alongside manufacturers, importers and distributors, the DGRL now also affects “representatives for manufacturers from third party countries”. b) The danger classification of the operating media takes place in accordance with the new DGRL and therefore the GHS/CLP regulation 1272/2008 and no longer in accordance with directive 67/548/EWG. c) The declaration of conformity must also be carried out in accordance with GHS/CLP regulation 1272/2008. Article 13 (classification of pressure equipment) is decisive. Updates since July 19th, 2016: a) The new directive has been adjusted to the legislative framework (New Legislative Framework – NLF). In front of this backdrop, manufacturers of pressure equipment must check their CE marking procedures and the documentation again after 2015 and adjust them to the new structure of the directive. b) Everyone bringing pressure equipment into circulation in Europe must be able to prove to the market supervisory authorities over a period of ten years from which company he/she has procured which pressure equipment or to whom he/she has supplied it. c) Manufacturers must conduct a risk assessment instead of a hazard analysis. d) New definition of several terms, module descriptions and contents. The detailed updates to the DGRL 2014/68/EU for manufacturers, distributors, representatives and importers as well as new participants, as well as updates to the obligatory documentation requirement can be found at netinform.de in the guide for the new DGRL 2014/68/EU.
Pressure loss – The pressure loss constitutes the pressure differential generated between two defined points through wall friction and internal friction in static mixers, pipes, moulded parts, fittings, etc. With static mixers, these points are the intake and outlet of the mixer. In engineering, a resistance coefficient ζ is used for elements installed in a pipe (mixing elements, valves, baffles, etc.) which can be taken from tables. The pressure loss generated by the wall friction is determined by the friction factor for pipes λ. In case of laminar flow the friction factor for pipes depends on the Reynolds number. The surface roughness plays a role especially with turbulent flows.
The equation for pressure losses in passed through flows with the prerequisite of a constant density is:
This is the Bernoulli’s energy equation, whereby the term of the static height is not taken into account because it does not represent a pressure loss.
Design criteria ρ density in kg/m3
u medium flow velocity in m/s
λ friction factor for pipes
l length of the tubing in meters
d diameter of the tubing in meters
ζ resistance coefficient
Pulsation – Latin for “periodic fluctuation”. In technical systems such as pumps and compressors, as well as in tubes, pulsation is a pressure surge designating the dynamic pressure change of a liquid. Pulsating work pressures, if the wrong type of burst protection is chosen, can lead to premature failure of the bursting disc. This is an ideal application for the STRIKO reverse acting rupture disc as this is the most uncritical disc with respect to pulsating work pressures of medium to high strength.