Pump and grinder assembly for use with a steam producing device

Details Pump and grinder assembly for use with a steam producing device Pump and grinder assembly for use with a steam producing device

2002-05-11

2004-03-23

Hong, William (Department: 3725)

Solid material comminution or disintegration

Apparatus

Including means applying fluid to material

C241S046010, C241S046170

Reexamination Certificate

active

06708910

ABSTRACT:

BACKGROUND
1.0 Field of the Invention
The present invention is directed to pump and grinder assemblies and, more particularly, to a pump and grinder assembly for use with a steam producing device, with the pump and grinder assembly being effective for pumping scale out of the steam producing device and grinding the scale into relatively smaller pieces.
2.0 Related Art
Steam producing devices such as steam generators, boilers, coffee makers and others, are well known in the art. Steam generators, which are vented to atmosphere, and boilers, which are pressurized to various gauge pressures, have a variety of applications including multiple applications in the cooking industry. For instance, steam generators and boilers are commonly used with convection-type steamer ovens such as those used in restaurants and other commercial establishments. The water supplied to these steam producing devices typically contains various minerals such as calcium, sodium, iron and magnesium. When the water is heated to its boiling temperature, the molecular bonds of the water break down causing these minerals to be deposited upon various interior surfaces of the housing of the steam producing device and components, such as water level sensors, disposed at least partially within the steam producing device. The minerals are typically deposited on any surface which is exposed to boiling water or steam, which constitutes essentially all interior surfaces of steam generators and boilers. The mineral deposits are referred to herein generically as “scale”. The buildup of scale within the steam producing device has a variety of adverse effects including increased operating costs and possible failure of the steam producing device.
Gas-fired steam producing devices typically include an outer housing and a firetube assembly contained within the outer housing. During operation, water is disposed in the space between the outer housing and the firetube assembly. Buildup of scale on the exterior walls of the firetube assembly reduces the thermal efficiency of the steam producing device, and therefore increases operating costs, by reducing the heat transfer from the metal walls of the firetube assembly to the surrounding water. The walls of the firetube assembly are heated by hot gas flowing within the assembly. The reduction in heat transfer through the water results in longer cooking times, with regard to steam producing devices used in the cooking industry, which is not desirable. The thermal efficiency of electrically-heated units is reduced when scale accumulates on the electrical resistance heating rods which are disposed within the water contained within the outer housing of the steam producing device and are used to transfer heat to the water.
Another problem with scale build up of this type is that it may lead to distortion or failure of the firetube assembly, which is typically made of stainless steel. This may occur as follows. The scale may accumulate on the exterior surfaces of the firetube assembly unevenly, with the thickness of the scale varying from top to bottom of the firetube assembly. Typically, the scale thickness increases with the temperature of the surface. The walls of the firetube assembly are generally hotter near the bottom where the gas burners are typically located, and are cooler near the top since the “hot air” cools down, due to heat transfer, as it flows through the firetube assembly from bottom to top, typically through a tortuous flowpath. Locally thicker areas of scale build up create “hot spots” in the metal walls of the firetube assembly. As an example, an average local metal temperature may be about 300° F., with a gas flame temperature of about 1000° F. under normal circumstances. As a result of scale build up, less heat is transferred to the surrounding water, so that the local metal temperature rises significantly, such as to about 700° F. by way of example. This may cause the wall of the firetube assembly to distort locally. Also, as one skilled in the art may appreciate, the presence of multiple hot spots may cause the metal wall of the firetube assembly to move to the extent that various seam or spot welds are pulled apart causing expensive repair or replacement of the unit. For instance, the spot welds attaching various interior heat transfer baffles to the walls of the firetube assembly may fail, causing water leaks into the combustion chamber of the firetube assembly. Additionally, the welds which attach the firetube assembly to the outer housing of the steam producing device may fail, which may result in water leaking externally of the steam producing device.
Operational costs may also be increased due to scale buildup on the water level sensors. When this occurs to the extent that the sensors are “limed over”, the sensors malfunction and are no longer able to detect the water level within the steam producing device. Typically, these sensors are part of a control circuit used to control water fill valves and the operation of the gas burners or electrical resistance heating elements within the steam producing device. Accordingly, when this occurs it may be necessary to shutdown and “de-lime” the device, which has been the industry standard for de-scaling water level sensors and attempting to de-scale the heat transfer surfaces within the steam producing device. A “de-liming” procedure is typically completed by pouring a chemical solution into the device, mixing it with water and running a cleaning cycle which adds to operating costs. The de-liming procedure may require the assistance of a service repairman or technician which further adds to operating costs.
Although de-liming procedures may be effective for cleaning the water level sensors and recovering thermal efficiency, by de-scaling various heat transfer surfaces such as the outer surfaces of the walls of a firetube assembly, other problems are created. During de-liming, pieces of scale, which may also be referred to as chips or chunks and vary in size and shape, are released and drop to the bottom of the steam producing device where they accumulate. Pieces of scale may also fall off during normal operation or during water filling and draining operations. When wet, these pieces tend to bond to one another forming a large mass of scale particles. When dry, the mass of scale particles is hard and brittle. Repeated de-liming procedures causes the accumulated mass of scale to grow in size which reduces the steam-generating capacity of the device due to reduced internal volume available for containing water. This also increases operating costs. Such an accumulation of scale may adversely affect water circulation within the steam producing device. As one skilled in the art may appreciate, when water boils, the water tends to rotate en masse, which mixes relatively hotter water with relatively cooler water within the steam producing device. However, the presence of significant scale build up within the unit may interrupt this natural convective flow of water, thereby reducing the efficiency of the unit.
Additionally, the buildup of scale in the bottom of the steam producing device may clog the drain system associated with the device. Steam producing devices such as a steam generator typically have a drain port extending through the housing of the device, which may be about two inches in diameter. However, a downstream drain valve, which is connected to the drain port by appropriate plumbing, may be much smaller, such as one-half inch diameter, due to cost considerations. Operators usually prefer remotely operated drain valves, such as electrically operated solenoid valves and, as known in the art, the price of these valves increases significantly with an increase in effective flow area. For instance, a nominal one-half inch solenoid valve may presently cost under one hundred dollars, whereas a nominal two inch solenoid valve may cost several hundred dollars. As may be appreciated, the presence of loose scale within the steam producing device may result in a relatively smaller flow area drain valve and associated plu

Affiliated with

Also associated with

Rating

Pump and grinder assembly for use with a steam producing device does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Pump and grinder assembly for use with a steam producing device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Pump and grinder assembly for use with a steam producing device will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3271973