But there is one key exception: The primary stage of sampling takes place using a vertically oriented auger, and the sample increments are typically removed from some sort transportation unit (e.g. truck, railcar, shipping container) of predefined size.
Common applications for sampling augers
A common application for auger sampling equipment is an as-received system where material is received on a per-unit (e.g. truck) basis. In an as-received system, it is important to monitor the material that is received in each truck, or in all trucks that are received from a common supplier.
Another common application is an as-shipped application where material produced is stockpiled prior to being loaded and shipped to customers on a per-unit basis (e.g. shipping container). In these situations, it is important to monitor what is being sold in each individual container and track this information by customer.
Auger Sampling Systems often appear different due to the configuration of a particular system layout, but since many of the system sub-components are similar to other sampling systems, many of the maintenance tasks are also the same as other types of sampling systems.
Auger Sampling System layout example.
Common inspection and maintenance tasks that are unique to auger-based systems are generally focused on the sample auger itself and the means used to maneuver the auger in a particular application.
Three common wear areas in auger based sampling systems are:
- The auger spiral (flights)
- The auger barrel
- The hydraulic hoses/fittings on the auger or the crane arrangement used to maneuver the auger
Sampling auger maintenance
When a sample auger collects an increment, it drills into the material being sampled. This drilling action draws sample material upward through the auger.
Once sample material reaches the top of the auger, it is diverted into a sample collection hopper. As sample material moves on and along the auger spiral, wear occurs.
This wear can appear as a reduction in the thickness of the auger spiral or a narrowing of the overall diameter of the auger spiral due to wear along the outer edges.
Wear to the thickness of the spiral is not easily identified without removing the spiral from the auger tube. Fortunately, this mode of wear typically takes a relatively long period of time to develop.
An auger spiral usually wears more quickly along the edges, so it is usually replaced because the edges have significantly worn before wear to the thickness of the spiral becomes a major issue.
As wear to the auger increases, the efficiency of the augering action decreases. This is seen primarily in the clearance between the outside of the spiral and the inside of the auger barrel.
A small clearance in this area is necessary for proper auger operation, but as this clearance increases due to wear, more material (especially fine material) begins to fall between the spiral and the barrel.
Eventually, this gap opens to a point where too much fine material is being lost from the sample or the auger no longer functions efficiently. A new auger will typically have 3/16” [4.5mm] clearance between the spiral and the auger barrel. In applications where finer particle sizes are present, a spiral may need to be replaced when this clearance reaches 5/16” (8mm).
Applications with larger particle sizes generally can tolerate a larger wear gap without issue.
As a sample auger drills downward, the outer barrel of the sample auger is in sliding contact with the material being sampled. The wear is greater at the end of the barrel since it has more contact with material. This wear requires periodic replacement of the barrel.
Fortunately, the auger barrel is easily inspected. If the auger barrel has worn to the point where it can be bent inward against the spiral and interfere with operation of the auger, it should be replaced.
A standard auger design often has a one-piece auger barrel arrangement that is fabricated as part of the whole auger assembly. This design requires that the auger barrel be cut off and a new section of barrel welded back in place.
A modified design also exists where a flange connection is installed above the wear point on the auger that allows for the lower section of barrel to be easily removed and replaced. This design is beneficial for applications with abrasive material or frequent use.
The wear life of an auger barrel is dependent on the application. A heavily used auger that is sampling abrasive material may last one to two years, whereas an application where the auger is used less often or with less abrasive material could last five or more years.
Hydraulic hoses and fittings
Many sample augers are hydraulically operated, though electrically actuated augers are becoming more popular in certain applications.
If your application does involve an electrically actuated auger, this will not apply.I If your application includes the commonly used hydraulic arrangement, it is necessary to inspect hydraulic lines and fittings on a regular basis to ensure proper function and minimize the potential for a failure.
Hydraulic hose or fitting failures not only render the auger and system inoperable, they can also cause issues when oil escapes into the environment.
Hydraulic hoses and fitting should be inspected one or two times per month. This inspection should involve:
- Checking the whole length of the hose for signs of wear
- Checking the hose ends where they terminate into the fittings
- Checking the tightness of the fittings where they connect with other fittings, cylinders, etc.
Any questionable hoses or fittings should be replaced, and all loose interconnections should be adequately tightened.
A sample auger presents some maintenance considerations that are different from other types of samplers. That said, the sampler auger is a relatively simple machine and, with some auger-specific inspection, these maintenance considerations can be easily managed.