Air filtration for nuclear installations

What is filtered, and why

The dominant stream is air, and filtration serves an aim that is simple to state: what enters a room must not leave it laden. Ventilation creates and maintains pressure cascades between zones, and filtration treats the air before it is released.

This is done by staging, never by a single element. A first stage retains the coarse load and protects those that follow; an intermediate stage refines; a very high efficiency stage treats the most penetrating fraction. Skipping a stage does not make the installation simpler: it makes the most expensive element in the train pay for the coarse load, and shortens its service life to a degree the operator sees in the budget.

To that are added activated carbon traps, used for the species that particulate filtration does not retain, and the elements for housings and air handling units that equip the same installations on their conventional utilities.

The constraints of the environment

The first is not the medium, it is sealing. A perfectly performing very high efficiency element, fitted in a frame that leaks, lets air pass beside the medium: the performance of the installation is that of the installation work, not that of the element. That is why the in-place leak test exists, and why frame geometry, gasket type and clamping system matter as much as the filter material.

The second is mechanical integrity over time: an element working for years under a constant airflow must hold without its pleats closing up or its separators migrating.

The third is traceability. On this kind of installation, knowing exactly which element was fitted, when, and against which documentation, is part of keeping control of the installation. It is a documentary requirement before it is a technical one.

Finally, the requirements placed on a supplier belong to each operator, and they vary from one installation to another. We claim no particular standing of our own here: this page describes a sector and the product families that answer it, not an entitlement.

What outsourcing the purchasing function changes here

Requirements cover a limited number of families but a great many housing dimensions, often inherited from several generations of installation. The useful work is to recover the exact dimension, the clamping type and the stage concerned, then to hold the availability of what is replaced in campaigns.

We approach several manufacturers for the same requirement and pass on the original documentation without rewriting it: in this sector the manufacturer’s documentation is the reference, and our contribution is to deliver it with the right element.

What to tell us

The stage concerned and the function sought; the frame dimensions and its depth; the gasket and clamping type; the nominal airflow per element; the number of elements and the replacement cycle. The marking read from the element in place, even partial, often saves one exchange.