Dry-Process Equipment Overview
Since the introduction of the first Cement Gun at the New York Concrete Show in 1910, Allentown has been the leader in design, engineering and manufacturing of innovative and effective dry-process equipment for construction refractory and geotechnical applications. Allentown Gunning Machines and Pre-dampeners are ideal for dry-process shotcrete applications.
DRY-PROCESS FREQUENTLY ASKED QUESTIONS
- When was the dry-process developed?
- How does the dry-process work?
- What are the advantages of the dry-process?
- What are the disadvantages of the dry-process?
When was the dry-process developed?
The dry-process was developed in the early 1900's, culminating in patents granted in 1909 and the process being commercialized in 1911.
How does the dry-process work?
Pre-blended dry or semi-dampened materials are placed into the shotcrete equipment and metered into a hose. Compressed air conveys material at high velocity to the nozzle, where water is added. Material is consolidated on the receiving surface by the high-impact velocity. The dry-process can be used for any shotcrete application, from the smallest patching and sealing projects up to the largest, such as tunnel linings, pools, canals or reservoirs.
The maximum production achievable with dry-process equipment is 10 -12 yd³/hr of dry mix, depending on conditions. To achieve this ultimate capacity, it is necessary to use 2" or 2-1/2" hose and a 900 cfm or larger compressor. Most applications have production rates of 2 - 6 yd³/hr of mix, using 1-1/4" or 1-5/8" hose and a 450-600 cfm compressor. Patching and sealing are done at even lower rates with 1" or 1-1/4" hose and a 250-350 cfm compressor. Rebound (rejected components of a mix) is an inherent part of the shotcrete process. Skill and expertise is required for control of rebound and overspray and must be a consideration when calculating in place volume.
What are the advantages of the dry-process?
- Easy setup, shutdown and cleanup.
- On-site control of materials.
- Nozzleman can be up to 1,000 ft horizontally or 500 ft vertically from the gun.
What are the disadvantages of the dry-process?
- The large amount of compressed air required for high-volume placement.
- Control of rebound.