Conveyors: fluid current – Ambulant or portable – Vehicle mounted
Reexamination Certificate
2000-06-05
2002-02-05
Walsh, Donald P. (Department: 3651)
Conveyors: fluid current
Ambulant or portable
Vehicle mounted
C406S034000, C406S198000
Reexamination Certificate
active
06343896
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATION
(none)
FIELD OF THE INVENTION
The invention relates generally to a pressure control system for a pneumatic offload. More particularly, the invention relates to a pressure control system for accurately controlling the air pressure in a discharge line during a pneumatic offload of a dry bulk good from a tank truck.
BACKGROUND OF THE INVENTION
A dry bulk good, for example cement powder or plastic pellets, is often loaded into the tank of a tank truck and transported from the manufacturer to a customer. At the destination, the dry bulk good is unloaded from the tank utilizing a pneumatic offload process. The dry bulk good, also referred to herein as the product, is offloaded from the tank truck through a discharge line attached to a coupler provided on the underside of the tank. A blower positioned upstream of the coupler is used to initiate, facilitate and expedite the pneumatic offload process. Specifically, the blower directs ambient air into the discharge line, and thereby produces a positive pressure in the discharge line. The positive pressure of the air in the discharge line moves the product out of the tank through the discharge line to a receptacle, such as a silo, for receiving the dry bulk good.
Accurate control of the pressure of the air in the discharge line is required to optimize and maintain the flow of the product through the discharge line. If the pressure of the air in the discharge line is less than the optimum pressure, the time required to offload the product from the tank will be excessive or the product may plug the discharge line. A slow offload is inefficient and results in increased operating costs to the manufacturer and the customer. A plug in the discharge line requires manpower and results in down time to clear the discharge line and to restart the pneumatic offload process, which likewise results in increased operating costs to both the manufacturer and the customer. If the pressure of the air in the discharge line is greater than the optimum pressure, the back pressure in the discharge line can damage the blower, resulting in unnecessary manpower, expense and down time to remove and replace the blower. The product may also be damaged if the temperature or the velocity of the air in the discharge line becomes excessive during the pneumatic offload process.
As a result, the operator of the tank truck must pay careful attention to the pressure of the air in the discharge line. The pressure of the air is primarily a measure of the amount of restriction to the flow of the product through the discharge line. As such, the pressure of the air in the discharge line is a function of several variables including the operating speed of the blower, the temperature of the air in the discharge line, altitude, and the velocity of the air in the discharge line (i.e., the rate at which the product flows through the discharge line). Tank trucks are typically equipped with pressure gauges to assist the operator to monitor the pressure in the discharge line. However, if the operator does not continuously monitor the pressure gauges during the pneumatic offload process, or if any of the gauges provides a false reading, the time required to complete the offload process can be unacceptably extended, the blower can be damaged or the product can be compromised, as previously described. At present, the operator of the tank truck attempts to control the pressure of the air in the discharge line by constantly monitoring the pressure gauges, adjusting the operating speed of the blower and diverting the airflow of the blower into the tank truck or discharge line or venting the airflow to the ambient air through the blowdown line. However, the operating speed of the blower is relatively constant. Thus, adjusting the speed of the blower is an insufficient method of accurately controlling the pressure of the air in the discharge line.
In an attempt to protect the blower from damage, most tank trucks are equipped with a valve, commonly referred to as a “pressure relief valve,” for relieving the air pressure in the discharge line. The pressure relief valve relieves the air pressure in the discharge line by venting the air in the discharge line to the ambient atmosphere when the pressure of the air exceeds a predetermined pressure. Conventional pressure relief valves are commonly referred to as “pop-off” valves because the valve opens suddenly when the predetermined pressure is exceeded. However, there are at least two common characteristics of conventional pop-off valves that can cause serious problems during a pneumatic offload of a dry bulk good from a tank truck. First, because the valve opens suddenly, a large volume of air is rapidly vented from the discharge line to the ambient atmosphere. The rapid loss of a large volume of air causes the air pressure in the discharge line to drop significantly and quickly. As a result, the discharge line is susceptible to becoming plugged with the product. As previously mentioned, a discharge line that becomes plugged with product requires manpower and is time consuming to clear, thereby resulting in increased operating costs to the manufacturer and the customer, along with a corresponding loss of productivity.
Second, conventional pop-off valves are activated mechanically, and therefore, are not particularly accurate. As a result, the pop-off valve does not always open at a pressure that is sufficiently close to the predetermined pressure. The pop-off valve may open when the air pressure in the discharge line is actually less than the predetermined pressure, thereby resulting in a slower offload or a discharge line that becomes plugged with the product. In both instances, the manufacturer and the customer suffer increased operating costs, along with a corresponding loss of productivity. Conversely, the pop-off valve may not open until the pressure in the discharge line is actually greater than the predetermined pressure, thereby resulting in damage to the blower and the unnecessary expense and loss of productivity suffered to remove and replace the blower. Although adjustable pop-off relief valves are commercially available, they have a limited adjustment, and furthermore, cannot be readily or accurately adjusted in the field. Pressure control systems of the type commonly used in industrial manufacturing and laboratory environments utilize more accurate, electronically and mechanically activated pressure relief valves. However, the more accurate pressure relief valves currently available are not cost effective, reliable or durable enough for use in the field, and in particular, on a tank truck.
Presently, there is no commercially available pressure control system for accurately controlling the pressure of the air in a discharge line during a pneumatic offload, and in particular, during a pneumatic offload of a dry bulk good from a tank truck. Furthermore, there is no commercially available pressure control system for accurately controlling the pressure of the air in a discharge line during a pneumatic offload that is cost effective, reliable and durable enough for use in the field. Still further, there is no commercially available pressure control system for accurately controlling the pressure of the air in a discharge line during a pneumatic offload that can be automatically activated and initialized from a remote location.
Thus, it is apparent that there exists a specific need for a pressure control system for accurately controlling the pressure of the air in a discharge line during a pneumatic offload, and in particular, during a pneumatic offload of a dry bulk good from a tank truck. It is further apparent that there is a specific need for a pressure control system for accurately controlling the pressure of the air in a discharge line during a pneumatic offload that is cost effective, reliable and durable. It is further apparent that there exists a specific need for a pressure control system for accurately controlling the pressure of the air in a discharge line during a pneumatic offload that can be
Canary James M.
Goodier Peter C.
Dillon, Jr. Jose
Dremann Christopher C.
Syltone Industries, LLC
Walsh Donald P.
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