A wide range of sample acquisition and filtration systems are available to prepare even the most difficult of samples for reliable on-line analyser measurement. The correct choice is often critical to prevent analyser blockage and optimise performance.

The PPM cross flow filter, is a simple in-line device used to protect an analyser from ingress of solids, for applications where sample quality is generally good but occasionally suspended solids may be present.

The Paper Band Filtration system has been widely installed through out industry for surface water, final discharge and process applications. Sample is filtered to a nominal 20 micron using a reel of filter paper that is continuously drawn through a delivered sample. For more demanding applications, it may also be configured with a periodical chemical wash.

The Automatic Ultra-Filter uses multi-stranded, flexible membranes in a flow through cartridge to produce a filtrate to 0.40 micron and induce filter element cleaning. Additionally, air back purging can also be fitted where sample contains significant suspended solids.

The PurCon sample preparation combines ultra-filtration with continuous coarse bubble diffusion. It is ideally suited to difficult applications such as activated sludge, supplying a quantity of filtrate for a number of analysers. The PurCon IS uses a similar principle but enables the membrane to be submerged directly in a sludge tank removing the need to install a sample pump. Instruments may thus be brought into the process.

Each application may vary in its requirements. The availability of sample, the effective sample head (vertical lift, horizontal displacement and sample pipe diameter determine this), the physical characteristics of the sample, the size and type of suspended solids and the risk from ragging are important considerations. Submersible sample pumps may be supplied with float switches where sample is intermittently available and self-priming is required. Surface mounted pumps are used with a strainer to screen sample preventing ingress of large solids and filamentacious material. Vortex pumps may be advantageous where a fast sample delivery is required to optimise analyser response times and prevent sample pipe work fouling. Industrial peristaltic pumps which can self-prime, are available for specific applications within the food and beverage industry, where sample may be intermittent and contain a significant malleable suspended solids component.

Duplex sample pumping has been designed for applications such as river monitoring and intake protection where it is critical to maintain sample especially on un-manned sites. Duty and standby pumps can be used to automatically flush each other on a regular interval or during head loss. Plastic bags, vegetation and sludge may otherwise intermittently block sample pumps and prevent supply.