Chipper casing design

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Background

Chipper casings designed for drop feed, blow discharge chippers are subject to considerable abrasion, particularly if the feed timber is felled in coastal plantations and hence has a high silica content.

As the casing wears away on the inside, the gap between the blow wings and casing increases, reducing the efficiency of the blow discharge. Blow lines block at the slightest provocation, leading to unnecessary downtime to free the blockages. Blow wings can be replaced, or the casing can be lifted to adjust the clearance, and improve the blow discharge efficiency. Once the casing wears through, the result is more blockages associated with circulation air loss, chip damage and unnecessary spillage.

Casings are fabricated from quench and tempered wear resistant plate, in order to extend service life, and are generally of welded assembly. Since the wear damage is found predominantly on the bottom circumferential plate and areas of the bottom side walls, much plate is undamaged. Sadly it is difficult to recondition such a worn casing as the variation in wall thickness and welded assembly generates unacceptable distortion.

This observation prompted Heskheath Ltd to develop a reconditionable chipper casing.

Casing specification

The casing is of bolted assembly, with the critical wear areas fabricated in chromium carbide overlay welded plate, the balance of the bottom casing from quench and tempered plate, and the top casing entirely from boiler plate.

The design of the assembly is complex as there is generally little space provided within the existing foundations and framework.

A reconditionable casing will cost 40% more than a conventional quench and temper plate casing, but the casing will remain in service for three times the life of a conventional casing, before reconditioning is necessary.

By accurately following the casing thinning, the casing can be reconditioned at 50% the cost of a new conventional casing. The design is such that if need be, the casing can be removed, reconditioned and replaced during a 48 hour shutdown.

Heskheath Ltd can design and produce such a casing for most blow discharge chippers, providing supervision where necessary.

We look forward to being of help.


	Heskheath Ltd \| home Hardwood log unscrambler \| Conveyor pulley standard \| Effluent channel screens \| Chipper casing design \| Log chain design Chipper casing design Background Chipper casings designed for drop feed, blow discharge chippers are subject to considerable abrasion, particularly if the feed timber is felled in coastal plantations and hence has a high silica content. As the casing wears away on the inside, the gap between the blow wings and casing increases, reducing the efficiency of the blow discharge. Blow lines block at the slightest provocation, leading to unnecessary downtime to free the blockages. Blow wings can be replaced, or the casing can be lifted to adjust the clearance, and improve the blow discharge efficiency. Once the casing wears through, the result is more blockages associated with circulation air loss, chip damage and unnecessary spillage. Casings are fabricated from quench and tempered wear resistant plate, in order to extend service life, and are generally of welded assembly. Since the wear damage is found predominantly on the bottom circumferential plate and areas of the bottom side walls, much plate is undamaged. Sadly it is difficult to recondition such a worn casing as the variation in wall thickness and welded assembly generates unacceptable distortion. This observation prompted Heskheath Ltd to develop a reconditionable chipper casing. Casing specification The casing is of bolted assembly, with the critical wear areas fabricated in chromium carbide overlay welded plate, the balance of the bottom casing from quench and tempered plate, and the top casing entirely from boiler plate. The design of the assembly is complex as there is generally little space provided within the existing foundations and framework. A reconditionable casing will cost 40% more than a conventional quench and temper plate casing, but the casing will remain in service for three times the life of a conventional casing, before reconditioning is necessary. By accurately following the casing thinning, the casing can be reconditioned at 50% the cost of a new conventional casing. The design is such that if need be, the casing can be removed, reconditioned and replaced during a 48 hour shutdown. Heskheath Ltd can design and produce such a casing for most blow discharge chippers, providing supervision where necessary. We look forward to being of help.