Let’s say you have a large order for a dry powdered food product and you need to be sure the product fits the customer’s specifications before it’s shipped, or you need to keep tabs on the moisture content of your material throughout a processing run, or you need to ensure that your chemical material doesn’t rise above a certain level of volatility. To accomplish these tasks, you’ll need to accurately sample and test the material using a sampler that can enter the material stream, capture a quantity of that material, and extract a representative sample for analysis. For the most accurate and repeatable sampling, you will need to employ a sophisticated method that allows precise samples to be taken at regular intervals, leaving no room for error – an automatic sampler.
1. How does an automatic sampler for solids and powder work?
Automatic samplers are available in three basic sampling modes and three common operating types. Sampling mode refers to how the sampler collects the sample: The spot sampler enters the material stream and takes a sample only at the point where it stops; the strip sampler enters the material stream and takes a sample from a narrow portion of the stream all the way across the stream and back; and the cross-cut sampler takes a sample from the stream’s entire cross-section. The cross-cut sampler will give the most representative sample of your material.
Operating type describes the automatic sampler’s material-collecting mechanics. The tube or tube probe sampler is the simplest and most common. Basically, it’s a tube with a hole near one end. The hole end of the tube moves into the material stream, material flows into the hole, and the tube retracts from the material stream. The tube-and-auger sampler type also is a tube with a hole in it, but an auger in the tube helps direct the flowing material into the sampler. The third type of sampler is the pelican diverter or pelican sampler, called this because of the vague similarity between the sample cutter (the component of the sampler that passes through the material stream and cuts out a sample) and a pelican’s beak: Both have an opening at the top with a “container” hanging down from the opening.
In all three operating types, a motor or pneumatic device activates the sampler, causing it to enter and withdraw from the material stream. The material flows into the sampler and then is released either by mechanics or gravity into a sample container that’s manually or automatically removed to your analysis device or quality control laboratory. All three types of automatic samplers can be used in any number of processes and on many types of equipment.
2. Why am I taking the sample?
Reasons to sample include the need to analyze material particle size, chemical, moisture, or volatile content for process and quality control and to meet regulatory compliance; control material physical appearance; and retain a sample for your or your customer’s future reference for raw material inspection or shipping authorization. Your sampling will need to be accurate and provide repeatable results.
3. What are my material’s physical properties?
Your material’s physical properties will dictate the sampler’s particular sampling mode and operating type. You need to know:
- Material flowability
- Particle size and density
- Material moisture content
- Material temperature
- Ambient temperature
- Distinctive material qualities (Is your material abrasive, corrosive, sticky, friable, or hazardous? Is it homogeneous? Does it tend to segregate?)
Knowing these qualities will help you choose the sampler’s materials of construction and any optional equipment needed for the unit to function properly in your application.
4. Where will I locate the sampler?
Space restrictions at your desired sampling location will be a major factor in your sampler choice. For example, a tube sampler is typically mounted at a 45-degree angle off your equipment, while a tube-and-auger sampler can be mounted horizontally. If either sampler will work for your application, and space is at a premium, you may want to go with the tube-and-auger sampler.
5. How do I choose a model?
A range of samplers is available in all of the basic sampling modes and operating types, in varying configurations. Once you know what mode and type you need, your representative can help you select a specific model. In addition to the factors already discussed, the following factors also will help determine which model best suits your application:
- Available utilities for powering the sampler
- Equipment the sampler will be interfaced with
- The sampler’s control method
It’s important to consider all factors before selecting your automatic sampler. Discuss your specific needs, both in terms of your application requirements and practical considerations like size and cost, with your sales representative. Together, you and your representative can determine which sampler model best fits your requirements and create and customize the proper sampler for your application.
Adapted from a white paper by Richard Bassett, Sentry Equipment Corp.
View Sentry samplers for solid & powder here.
This article was originally published on our website.