BRIEF HISTORY OF HIGH PRESSURE EQUIPMENT 

    Vessels used to contain high pressures (greater than 70 MPa) have been used for many years in many industries such as cannons and small arms, processing polyethylene, materials processing and high pressure water jet cutting for example.  Most high pressure commercial applications use vessels that operate at pressures no greater than about 400 MPa.  Some of these vessels such as those used in polyethylene processing and water jet cutting are subjected to high cycle fatigue loading.  Some weapons and some metals processing operating pressures are as high as and even greater than 700 MPa.  This later group of high pressure vessels is not usually subjected to high cycle fatigue loading. 

FOOD INDUSTRY EQUIPMENT REQUIREMENTS

    ERI has developed equipment with the ability to provide a production plant that meets the following demands of the food processing industry.  

1)        The idealized process will require 700 MPa at between 40 and 50°C, with a two minute hold time.

2)        The equipment will be utilized as much as 20 hours per day, 360 days per year and have an economic life of at least seven years.  This requires a durability life of the major components of about 1,000,000 cycles.

3)        Minor components and parts such as closures, seals, piping, etc. are considered consumable and need not meet the above durability requirements, however, maintenance cost must be minimized.

4)        The equipment will use stainless steel food contacting parts and designs that allow ease of maintenance and cleaning of the equipment on the food processing floor. Stainless steel allows the use of pure water as the compression media and eliminates the need for lubricants.

5)        Target per pound added costs are $0.05 or less to no more than $0.20 depending on product 

    The technologies developed to meet these requirements can be extended to higher pressures as well.  High durability vessels have been designed to operate at pressures up to 850 MPa.  However, food processing systems at this pressure must be considered developmental until reliability and maintainability issues are addressed. 

ERI BATCH ISOSTATIC EQUIPMENT 

    The ERI solution to the high pressure technology requirements is shown in the figure below.  The system incorporates numerous innovations including patent pending vessel technology.  It is the first integrated system that was developed exclusively for the food processing industry from scratch.  The system is not a modified isostatic press or other high pressure processing equipment converted for use in food processing. 

    The system consists of several components including: the process vessel assembly, the yoke assembly, the vessel integration system assembly, the high pressure hydraulic supply and a material handling system.  For ease of explanation, many of the details of the equipment have been removed from the figure.

DESCRIPTION OF THE OPERATION OF THE SYSTEM 

    The process vessel is operated in the vertical position.  The high pressure water is injected into the process vessel from the high pressure hydraulic power supply through high pressure tubing.  There is a movable section of tubing that connects between the top or bottom closure of the vessel and a coupling on the exterior of the yoke.  

    When the pressure is relieved, the movable section of tubing is extracted from the vessel end closure.  This frees the vessel to move within the yoke and the vessel is rotated clockwise to its load/unload.  In this position, the closures are removed and the product carrier is released by gravity.  The bottom closure is replaced and the next product carrier and water charge are feed into the vessel.  The top closure is replaced and the vessel is rotated to the process position.  The high pressure tubing attachment is placed inside the vessel and the pressure is applied and held for the required holding time.  At this point the pressure is relieved and the entire cycle is repeated. 

    The vessel size can be as large as 250 mm to 300 mm (10 in. to 12 in.) to accommodate large size food products.   The length of the vessel determines the vessel volume and 100 liter size vessels are common.  The system is modular and can be easily changed to fit the specific needs of the food product and processing requirements for maximum efficiency.  Several vessels can be integrated into a single system that incorporates a single hydraulic power supply. 

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Last modified: October 09, 2007