Pilat (U. of W.) Source Test Cascade Impactors

History:

The Pilat Mark III Source Test Cascade Impactor was developed at the University of Washington (Seattle, Washington) Department of Civil Engineering by Professor M. J. Pilat and graduate students specifically for measuring the particle size distribution in stacks and ducts at air pollution emission sources.  The Pilat Mark I Cascade Impactor was developed in 1968 in order to provide particle size distribution data needed for research projects at the University of Washington concerning the control of particulate emissions with wet scrubbers and the relationship of plume opacity to particle properties.   Using data obtained during extensive use of the Mark I and II models for particle size measurements at aluminum reduction plants and Kraft recovery boilers, the improved Mark III model was designed and constructed.  The Pilat Cascade Impactors have been have been successfully used to measure the particle size distribution and the particle collection efficiency at many emission sources including:  coal fired power boilers, Kraft pulp mill recovery boilers, sulfite pulp mill recovery boilers, hog fuel (wood-waste) boilers, aluminum reduction plants, and oil fired turbines.

Tests conducted by the Southern Research Institute (of Birmingham, Alabama) under an Envinronmental Protection Agency contract, as reported by McCain, et al, (1973) showed that this Pilat Mark III Cascade Impactor appeared to have the least particle blow-off and re-entrainment problems compared to the other impactors.  The California Air Resources Board has used the Pilat Mark V cascade impactor for ARB's Method 501 "Determination of Size Distribution of Particulate Matter from Stationary Sources".

Features of Cascade Impactors:

• Separates 0.25 to 20 micron diameter solid or liquid aerosol particles into 8 size classifications (Mark III) or 12 classifications (Mark V) for later weighing and/or chemical analysis.
• In stack sampling and particle size minimizes problems of losses of particle to the tubing walls and of water vapor condensation.
• Isokinetic sampling for a true representative particle sample.
• Separate particle collection plates which allow for obtaining multiple samples with a single cascade impactor unit.
• Lightweight disposable collection plate inserts of stainless steel foil allow imporved weighing precision and reduces need for many sets of collection plates.
• Built-in 47mm diameter filter holder in the cascade impactor outlet.
• Collection plates designed for minimal particle sample handling loss.
• Sample at 0.1 to 1.0 acfm gas flow rate (2.8 to 28 liters per minute).

Product List:

• Mark III Source Test Cascade Impactor
• Mark V Source Test Cascade Impactor
• Right Angle Sampling
• Precutter
• Mark 8 High Grain Loading Impactor
• Thimble Filter Holder
• Substrates

Pollution Control Systems Corporation
PO Box 15770, Seattle, WA 98115
FAX: (206) 523-7221  Phone: (206) 523-7220
jwpaul@earthlink.net

Mark III Source Test Cascade Impactor

A photo of the Pilat Mark III Cascade Impactor disassembled parts is presented in Figure 1.  The cascade impactor operates by separating the particles into a number of size fractions.  The number 1 jet stage is the inlet sampling nozzle (a single jet of 0.5" diameter).  The number 2 jet stage has six 0.228 inch diameter holes.   Jet stages 3, 4, 5, 6, and 7 have multiple holes of decreasing diameter. The particle collection plates are annular, or doughnut shaped.  The 47mm diameter filter holder in the outlet is shown on the righthand side of Figure 1.  The separation of the aerosol particles is accomplished by passing the sample gases and aerosol particles through jet orifices of successively lesser diameter and increasing gas jet velocities as is shown in Figure 2.  The aerosol particles of sufficient size are inertially collected on the first particle collection plate downstream of the first jet stage which is the single jet of the sampling nozzle.

Figure 1

Figure 2

Construction:

• Cylindrical casing, jet stages, inlet section, outlet section, and collection plates - all 316 stainless steel.
• Internal seals - Viton or silicone O-rings (can be omitted for high temperature applications).
• Assembled length - 10 inches (25 centimeters) including nozzle;   2.9 inches outside diameter.
• Weight - 9 pounds (4.1 kilograms)
• Weight of stainless steel foil collection plate insert - about 1 gram.

Mark V Source Test Cascade Impactor

The Mark V cascade impactor uses 11 jet stages and provides 12 particle size classifications.  It is useful in testing in higher particle mass concentrations, such as exists at the inlet of particle control devices.  The jet stages, collection plates, inlet section, and outlet section of the Mark V are interchangeable with the Mark III model and this allows for flexibility in arranging the jet stages.  The Mark V includes 12 multi-jet stages and the number 1 inlet sampling nozzle stage which can be arrange in at least 4 different jet stage configuragtions depending on the desired aerodynamic cut diameters (d₅₀'s).  It operates in the 0.1 to 1.0 acfm gas sampling flow rate range.  The gas flow rate trajectories and jet stages for the Mark III and Mark V Pilat Source Test Cascade Impactors are schematically shown in Figures 3 and 4.

Fig. 4  Pilat (U. of W.) Mark III Cascade Impactor  Fig. 5   Pilat (U. of W.) Mark V Cascade Impactor

Precutter

The PCSC Precutter attaches to the inlet section of the Mark III and Mark V cascade impactors.  It provides a similar cut diameter to the first stage of the impactors (approximately 17 microns at 100 degrees F and a flowrate of 0.5 acfm), while offering increased large particle collection capacity.  The particles are collected in the cylindrical chamber of the precutter.  A glass fiber filter liner, which fits inside the chamber, can be used as a substrate.  The filter liner can be weighed pre and post test to determine the sample weight.  These precutter liner substrates are available in boxes of 25.  Use of the precutter enables sampling in a standard 3 inch diameter test port.  Figure 5 shows the PCSC precutter with an attached nozzle and three additional nozzles.

Fig. 5 PCSC Precutter      

Right Angle Sampling Attachment

The Right Angle Sampling Attachment replaces the inlet section of the Mark III and Mark V.  With a special nozzle attached, this unit can fit into a 4 inch diameter test port.  It provides a similar cut diameter as the first stage in the standard configuration.  This attachement will accept collection plate inserts or substrates identical to the first collection plate in the Mark III and Mark V.  Figure 6 shows the Right Angle Sampling Attachment with Nozzle.  The Right Angle Sampling attachment uses either the longer Item 4-1 sampling nozzles or the shorter Item 13-2 sampling nozzles (the Item 13-2 shorter nozzles are of 3/16", 1/4", 3/8", 5/16", and 1/2" inlet diameter).  The Right Angle Sampling Attachment with a longer nozzle is shown in Figure 6.

Fig. 6  Right Angle                
Sampling Attachment

Mark 8 High Grain Loading Impactor

The Pollution Control Systems Corporation Mark 8, High Grain Loading (HGL) Impactor offers the user the ability to obtain particle size distribution information in gas streams where the high concentration of particle matter present makes sampling with our standard models difficulet, especially for longer sampling periods.

This 316 stainless steel sampler provides size information in four ranges by the use of four stages.  A description of the stages, along with the effective aerodynamic cut diameters, d₅₀'s, that would be obtained if sampling at a gas flow rate of 0.5 acfm (14.2 liters per minute) at 70 degrees F is outlined below.

The HGL Impactor offers distinct, convenient operating features.  The utilization of a 90^o inlet configuration offers ease of access at many varied sampling locations.   This precutter also features PCSC's exclusive high purity glass fiber liners to facilitate sample recovery.  The thimble filter chamber used for this instrument is the EPA Method 17 accessory offered individually by Pollution Control Systems Corporation as part of our product line.  This uses commercially available 43 X 123 mm thimble filters of either single or double thickness, made of cellulose or glass fiber media for different sampling requirements.  This thimble filter chamber can be used alone to obtain total particulate matter mass loading as well as in part of the HGL configuration.   The use of interchangeable parts also allows the user to obtain a conversion kit to convert to a standard Pilat (U. of W.) Mark III cascade impactor at a substantial savings.   Figure 7 shows the Mark 8 HGL impactor kit which includes 6 isokinetic sampling nozzles (1/8", 3/16", 1/4", 5/16", 3/8", and 1/2" inlet diameters), one precutter wrench, and two body wrenches.

Fig. 7   Mark 8 High        
Grain Loading Impactor

Thimble Filter Holder

The EPA Method 17 (in-stack filter sampling) thimble filter holder is a special inlet section to the Mark III and Mark V cylindrical casing which will hold a 43 x 123 mm diameter thimble filter.  The thimble filter fits onto a tapered inlet tube and a tapered retaining ring holds the filter in place.  The retaining rings are supplied to accomodate different thickness thimbles available.

Substrates

Substrates are available in Reeve Angle (borosilicate glass; 58% SiO₂, 11% B₂O₃) 934 AH glass-fiber filters and QM-A ultra-pure quartz (99% SiO₂) microfiber filter material.  The QM-A ultra-pure quartz microfiber filter material contains virtually no alkaline earth metals and is therefore recommended for sampling and subsequent analysis of particle samples where acidic gases such as SO₂ and NO₂ are encountered.  Artifact production of sulfates and nitrates on the filter is virtually eliminated with QM-A ultra-pure quartz filters.  The low background levels of heavy metals in the QM-A filter substrates make it suitable for X-ray fluorescence and neutron activation chemical analysis.)  These pre-cut substrates should be mounted in the stainless steel foil inserts for ease of handling and to eliminate loss of sample or substrate.

Pollution Control Systems Corporation
PO Box 15770, Seattle, WA 98115
FAX: (206) 523-7221  Phone: (206) 523-7220
jwpaul@earthlink.net

Pricing

Publications:

1. Operations Manual for Pilat (U of W) Mark 3 and Mark 5 Source Test Cascade Impactors
   
2. Pegnam, R. and M. Pilat, Airborne Particulate Emissions from a Chromic Acid Anodizing Process Tank, Air & Waste J., Vol. 42 (March 1992) Adobe Acrobat PDF File
   
3. Pilat, M. and T. Steig, Size Distribution of Particulate Emissions from a Pressurized Fluidized Bed Coal Combustion Facility, Atmospheric Environment, Vol. 17, pp. 2429-2433 (December 1983) Adobe Acrobat PDF File