Comde-Derenda GmbH

- Model PNS T-DM - Automatic Sampling System

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Automatic sampling system for continuously monitoring particulate matter (PM10, PM2.5 or PM1) without manual filter changes. The PNS T combines a low / medium volume sampler (LVS or MVS) and a filter changer in a stainless steel cabinet. It collects fine particulate matter on sampling filters according to EN 12341:2014 (PM10 and PM2.5). For this purpose, a vacuum pump draws in ambient air, and the system fractionates the airborne particles in a sampling inlet. The air containing the desired fine particulate fraction then passes through the filter, where the particles are collected and made available for subsequent gravimetric assessment or analysis. The automatic filter changer with Geneva drive and two parallel filter magazines facilitates sequential series of up to 18 or 24 sampling cycles. The volumetric flow rate is measured with an orifice plate and electronically adjusted with an accuracy of ≤ 2%. Types: PNS 18T-DM-3.1 / PNS 18T-DM-6.1 / PNS 24T-DM-3.1 / PNS 24T-DM-6.1

Design

The sampling system PNS T consists of the following principal components:

  • Stainless steel cabinet with lockable door
  • Control unit with electronic modules, SD card reader and RS-232C interface
  • Vacuum pump
  • Orifice plate
  • Temperature and humidity sensors
  • Filter changer with filter magazine holder
  • 2 filter magazines
  • Aluminum intake tube (anodized, polished inside, diameter 40 mm, length 800 mm, custom lengths available)
  • Sampling inlet (for particulate matter fractions PM10, PM2.5, PM1 or TSP; optional)
  • Peltier cooler (optional)

Type 3.1 is equipped with a 4 m³/h rotary vane vacuum pump. The volumetric flow rate for sampling PM10 or PM2.5 fractions is 2.3 m³/h; the maximum vacuum at the filter is 300 mbar. The maximum volumetric flow rate when glass fiber filters are being used is 3.5 m³/h.

Type 6.1 is equipped with a 6 m³/h rotary vane vacuum pump and can be operated with a maximum volumetric flow rate of approx. 5.5 m³/h. It is especially suitable for measuring semi-volatile organic compounds (SVOCs) and for use in conjunction with special filter materials (e.g. cellulose nitrate or Nuclepore filters). The maximum vacuum at the filter is 500 mbar.

The system cabinet is vented in order to prevent moisture condensation and icing-up of the filters. The connection between the sampling inlet and intake tube is gas-tight in order to prevent losses arising from particle deposits on the inside wall. The filter cartridges are held in the filter magazine individually by leaf springs. The spring force presses the cartridge against the top smooth wall of its compartment so that no volatile particulate matter can escape.

The filter magazines also serve as portable containers. Filter cartridges for a variety of filter sizes can be used (47 mm, 50 mm or custom-made in the factory, e.g. for ISSeP/Belgium or WINS/USA).

Operating principle

Before sampling begins, the desired settings are entered in the control unit, and the filter magazine is placed in the filter changer. Once the operating cycle is activated, sampling takes place automatically according to the set parameters. During operation the vacuum pump draws in air laden with fine particulate matter through the sampling inlet. The dust particles are fractionated by size in the sampling inlet with impactor. The particles of the desired fraction are then deposited on the sampling filter in the sampling position. At the end of the sampling period, the laden filter is automatically placed in the magazine and a new filter is transported to the sampling position for the next sampling cycle. The magazine is moved along the vertical axis, and the filter cartridges along the horizontal axis, by precision ball screws. The sampling position is opened by a linear actuator and closed by a powerful spring.

The volumetric flow rate is measured with an orifice plate and electronically adjusted with an accuracy of ≤ 2%. The ambient climatic conditions are continuously monitored by temperature and humidity sensors. The optional Peltier cooler ensures that the laden filter storage temperature in the unit does not exceed 23 °C.

The following data captured during sampling are saved in the internal memory. The data can be additionally backed up on an SD card or transferred to a PC by way of the RS-232 interface:

  • Serial number
  • Filter number
  • Sampling start and end date/time
  • Sampling duration in hours and minutes
  • Mean volumetric flow rate in m³/h and Nm³/h
  • Sampled volume in m³ and Nm³
  • Mean air pressure/temperature/humidity
  • Mean pressure difference at the filter
  • Filter storage temperature

  • Complies with EN 12341:2014 (PM10and PM2.5)
  • For 47 mm filters
  • Electronically adjusted volumetric flow rate
  • Temperature and humidity sensors
  • Magazine with 16 or 18 filter cartridges
  • RS-232 interface
  • Vented jacket pipe

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