August 1995, Volume 4

As many of you are aware, Process Equipment Company has been expanding its capabilities to meet the rising needs of it's customers. With the recent acquisition of Weigel Engineering Company, Inc. and the rapidly growing National Boiler Service Company, Process Equipment Company is now poised to handle turnkey responsibility for almost any improvement project to an existing power boiler.

Some of the projects that have already been successfully performed include:

A third project recently performed by Process Equipment in conjunction with Weigel Engineering and National Boiler Service was the first-ever installation of a Detroit Stoker water cooled flat Hydrograte stoker. This project included the design, fabrication and installation of the stoker foundation, support steel, sifting hoppers, electrical and control components and the independent cooling water circulating system. The flat Hydrograte stoker replaced an existing traveling grate stoker on a wood fired boiler at a Virginia paper mill that was experiencing excessive downtime and maintenance cost.

One of the many advances in technology for stoker fired wood refuse boilers has been the development of the water cooled vibrating grate stoker. In the case of the Virginia paper mill, the decision to replace the traveling grate stoker with the Detroit water cooled flat Hydrograte was based on a few unique features of the flat Hydrograte stoker.

First and foremost were the higher reliability and lower maintenance cost associated with the operation of the stoker. Because the grate surface is water cooled, the Hydrograte stoker does not experience the heat related damages that many times plague the traditional traveling grate stokers. Also, there are no bearings, shafting or parts requiring lubrication exposed to the furnace or undergrate combustion air temperatures. The drive mechanism is located outside the boiler setting and can be maintained while the unit is on line. The downtime and maintenance cost associated with the Hydrograte stoker is typically a fraction of the traveling grate stoker.

While both the traveling grate stoker and the Hydrograte stoker offer continuous ash discharge, the Hydrograte stoker moves the ash with intermittent and relatively low frequencies of vibration. Wood refuse is burned very successfully on the Hydrograte stoker due to this vibrating action. Many times it is very difficult to evenly distribute the fuel across the grate surface causing the fuel to pile up in some areas and the grate to be exposed in other areas. This problem can lead to high quantities of excess air, excessive carry-over in the boiler and unburned fuel being disposed of in the bottom ash hopper. The vibrating action of the Hydrograte stoker helps to better distribute the fuel on the grate surface by evening out the hills and valleys of the fuel on the grate.

The selection of the flat Hydrograte over the traditional sloped Hydrograte was based on the need to keep the downtime to install the Hydrograte to a minimum. The flat Hydrograte stoker was designed with an independent cooling water circulation system. The sloped Hydrograte stoker is normally tied to the boiler's natural circulation system, thus requiring pressure part modifications to the boiler. In this case, we were able to install the independent cooling system while the boiler was still on line and only had to make the tie in while the boiler was down. The downtime to install the flat Hydrograte was only 12 days.

This project is just one example of how Process Equipment Company is striving to meet the needs of it's customers by offering new technology to improve the operation of existing equipment. Our capabilities include consulting, design engineering, detail engineering, fabrication and installation of your boiler auxiliary equipment and/or your boiler pressure parts.

For additional information on articles appearing in this newsletter, contact Process Equipment Company at (205) 663-5330 or E-mail to: information@process-equip.com


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