Method and apparatus for converting a sootblower from a single motor to a dual motor drive

A single motor rack and pinion driven sootblower is converted to a dual motor version. The single motor version includes a lance tube which is advanced and retracted transversely on a carriage and is further rotationally driven by a translational mechanical drive which rotates the lance tube as it is being axially driven. The conversion is accomplished by disengaging the translational drive by removing the original drive hub within the drive housing of the carriage and this original drive hub is substituted with a tubular rotary drive hub which is not in driving engagement with the translational drive when installed. A second rotational motor is then mounted on the carriage assembly and connected to externally exposed portions of the substitute hub through a gear drive for independently rotating the substitute hub and thereby independently rotating the lance tube about its axis. The two motors are then independently controlled through the use of a microprocessor to provide infinite indexing possibilities for the lance tube.

BACKGROUND OF THE INVENTION

This invention generally relates to boiler cleaning. More specifically, the invention relates to a retracting sootblower having a mechanism for articulating the sootblower and lance tube so that the lance tube can be inserted over multiple insertion axes through a single access port in a boiler.

Sootblowers are used to project a stream of blowing medium, such as water, air, or steam, against the heat transfer surfaces of the tube bank located within the boiler. The blowing medium is used to dislodge various combustion byproducts, including slag and ash, which becomes deposited on the heat transfer surfaces. If the encrustations are not removed, boiler efficiency significantly decreases. By using the blowing medium to dislodge the encrustation, the thermal and mechanical shock provided by the medium fractures the encrustations, breaking them free, and dislodges them from the heat transfer surfaces. Through effective and consistent sootblowing, the efficiency of the boiler can be maintained.

The present invention pertains to sootblowers of the type or category which are retractable. A retractable sootblower is located outside of the boiler and its lance tube is periodically advanced into and withdrawn from the boiler to perform cleaning. One or more nozzles are located on the end of the lance tube and project jets of the blowing medium. While being inserted and retracted, the lance tube is rotated so that the jets trace helical paths across the heat transfer surfaces.

The present invention pertains to the modification of a retractable sootblower of the type illustrated in U.S. Pat. No. 5,605,117 which is articulable so that the lance tube can be inserted into and retracted from a boiler over multiple insertion axes, but through a single or common access port. The sootblower includes an exteriorly located frame mounted adjacent to a wall box or access port in the boiler wall. A carriage assembly is supported by the frame and coupled to a lance tube which has at least one nozzle at its distal end. The lance tube generally defines the axes along which it will be inserted into and withdrawn from the interior of the boiler. As the lance is inserted, retracted or both, it is also rotated by the carriage assembly through a mechanical translational drive.

An advantage of this type of single motor rack and pinion driven sootblower is that it is economical to manufacture. The single motor is used not only for translational drive of the carriage assembly, but also used to rotationally drive the lance tube through the mechanical translational gear drive. This single motor is generally driven through the use of a programmable controller.

However, a disadvantage of such a single motor rack and pinion driven sootblower is that the mechanical translational drive provides fixed indexing of the rotational drive for the lance tube and the lance tube rotation is a function of the traversing speed. Accordingly, as is taught, for example, in the disclosure of U.S. Pat. No. 5,579,726, it is preferable that such retractable rack and pinion driven sootblowers have separate independent motors for transverse drive of the carriage assembly and rotational drive of the lance tube. This permits independent driving of the two motors through the use of a microprocessor which permits infinite indexing for both reverse helix cleaning and cross helix cleaning and the ability to switch the pitch during sootblower operation and to change the oscillating mode.

Accordingly, it is a principal object of the present invention to provide a method and apparatus for converting a retractable single motor driven sootblower of the type disclosed in U.S. Pat. No. 5,605,117 to a dual motor drive for independently controlling the traversing motor and the rotary motor for thus enhancing the cleaning ability of the sootblower by allowing the motion of the lance tube to be infinitely changed or varied.

SUMMARY OF THE INVENTION

The novel method and apparatus of the present invention is provided for converting a sootblower from a single motor to a dual motor drive version. Such single motor drive sootblowers have a movable lance tube with a hollow interior for ejecting a cleaning fluid under pressure from a distal end of the tube, and they have a detachable proximal end portion configured as an original tubular rotary drive hub. The rotary drive hub is received in a rotary bearing housing which is secured to the carriage assembly. The carriage assembly is driven by a traversing motor for driving the lance tube axially to both extend and retract the lance tube. A termination end portion of the original drive hub is exposed at a proximal end of the bearing housing for connection to a source of cleaning fluid under pressure to the hollow interior of the lance tube. A translational drive is provided on the carriage assembly to translate the transverse movement of the carriage assembly into a rotational drive for the lance tube. The translational drive is connected for, causing rotational driving of the original tubular rotary drive hub for the lance tube in the bearing housing as the lance tube is being axially driven for thereby rotating the lance tube about its axis.

The conversion technique of the present invention is accomplished by disengaging the translational drive by removing the original drive hub and replacing it with a substitute tubular rotary drive hub which is not in driving engagement with the translational drive when installed. A second rotational motor is then mounted on the carriage assembly and connected through a gear drive to exposed portions of the substitute hub for independently rotating the substitute hub and thereby independently rotating the lance tube about its axis. The traversing motor and the rotary motor are independently driven, preferably through the use of a microprocessor, for thereby creating custom traversing and rotational movement patterns for the lance tube.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT

Referring now toFIG. 1, a sootblower is generally designated at10and illustrates a single motor rack and pinion sootblower of the prior art to be converted by the teachings of the present invention. This prior art sootblower is described in U.S. Pat. No. 5,605,117 and accordingly the same description and numeral designation are followed for conformity. The sootblower10principally comprises a frame12, a lance tube14, a feed tube16, and a carriage assembly18.

The sootblower10, shown in its retracted horizontal position is located adjacent to a boiler wall20so that the lance tube14is aligned with an axis port22. The port22permits the lance tube14to enter into the boiler to perform cleaning of the heat exchanger surfaces located within. Upon actuation, the carriage assembly18will cause transverse movement of the lance tube14along its axis for extending into and then retracted it from the boiler.

The carriage assembly18is capable of causing transverse movement of the lance tube14because it includes a transmission and drive system located within the carriage housing31. The transmission and drive system move the carriage assembly18along a pair of rack assemblies24located on opposite, interior sides of the frame12. The rack assemblies24are made up of sections of angle iron26, welded or otherwise secured to the interior sidewall of the frame12, which support downwardly toothed racks28. A pair of carriage rollers30are mounted to the carriage housing31so as to rest on top of the angle iron26and support the carriage assembly18. Beneath the carriage rollers30are pinion gears32which engage the toothed racks28. The pinion gears32are coupled through the transmission (not shown and located within the housing31) to a motor33which is in turn connected to a programmable controller (not shown) that will initiate a cleaning cycle as needed and according to the operational characteristics of the boiler itself. The transmission not only causes transverse movement of the lance tube14, but it also includes a mechanical translational drive which simultaneously causes rotational movement of the lance tube14as well as the lance tube14is being axially driven.

The frame12of the sootblower10includes an outboard end wall34, and inboard end wall36and a pair of opposed sidewalls38, to which the rack assemblies24are mounted as described above. Additionally, the top of the frame12may be covered with panels40to enclose and protect both the carriage assembly18and the lance tube14. While only one variety of sootblower frame12is shown in the figures, it should be well understood that there are many alternative frame designs.

The feed tube16is coupled at the rear end of the sootblower10to a poppet valve42which is typically mounted to a support bracket52which is secured to the outboard end wall34of frame12. The feed tube16conducts a blowing medium whose flow is controlled through the action of the poppet valve42. Linkages44actuate the poppet valve42and are triggered by the carriage assembly18as it begins to move forward and insert the lance tube14into the boiler. Upon retraction of the lance tube14and rearward movement of the carriage assembly18, the carriage assembly18again triggers the linkage44to shutoff the flow of blowing medium. The lance tube14over fits the feed tube16and a packing gland (not shown) creates a fluid seal between them. In this manner, the blowing medium is conducted from the feed tube16into the lance tube14for discharge from nozzles46located at the distal end of the lance tube14.

A coiled electric cable60provides power to the drive motor33as the motor33moves with the carriage assembly18during insertion and retraction. A front support50includes bearings which support the lance tube14during its longitudinal and rotation movements. For longer lance tube14lengths, an intermediate support (not shown) may be provided to prevent excess of bending or deflection of the lance tube14. Additional details of the construction and operation of this well known design may be found in U.S. Pat. No. 5,605,117.

As previously explained, the translational drive contained within housing31is connected for causing rotational driving of lance tube14as the lance tube14is being transversely inserted into and retracted from boiler wall20. This is accomplished because the mechanical translational gear drive within housing31rotates original tubular rotary drive hub59in a known and conventional manner. The proximal end61of lance tube14is connected to the forward end of original rotary drive hub59on the forward face of housing31so that as original tubular rotary drive hub is rotated within housing31, so also is lance tube14for thereby rotating lance tube about its axis.

The conversion method and apparatus of the present invention for converting a single motor rack and pinion driven sootblower to a dual motor version is illustrated inFIGS. 2 and 3. In order to carry out the conversion, the translational drive contained within housing31is disengaged by removing the original drive hub59from the housing31and replacing it with substitute tubular rotary drive hub59′ which is not in driving engagement with the translational drive when the new substitute rotary drive hub is installed. In fact, one or more internal gears (not shown) for the translational drive may also be removed. Then a second gear motor designated as rotational motor62is installed on the carriage assembly18and connected through gear drive63(FIG. 3) to exposed exterior portions of substitute hub59′ for independently rotating substitute hub59′ and thereby independently rotating lance tube14about its axis, as lance tube14will be connected at its proximal end61to the forward face64of substitute hub59′ in the same manner that it was previously connected to the forward face of original hub59. Motors33and62are thereafter independently driven for thereby creating custom traversing and rotational movement patterns of lance tube14through the use of microprocessor65.

Rotational motor62is fastened to cover plate66with stud and nut combinations67. The cover plate66is then bolted to the rotary motor adapter68by stud and nut combinations69. Motor gear70is attached to rotational motor62by the combination of machine screw72, washer73and spacer74which secures gear70to motor shaft75with key76. Gear70in turn drives idler gear assembly77and this idler gear assembly in turn drives hub gear78which rotationally drives hub59′. Gear78is keyed to hub59′ by key79. The proximal end61of lance tube14is connected to the face64of substitute hub59′ and the feed tube16is connected through a packing gland to the termination end portion80of substitute drive hub59′, exposed at the proximal end81of bearing housing31for connection to the source of cleaning fluid under pressure.