Finite Element Analysis: Filter Press Stress Test
Using Finite Element Analysis, M.W. Watermark is able to provide the highest quality, safest, and cost-effective filter press available.
M.W. Watermark is committed to providing equipment that is both reliable and cost-effective. A critical factor of filter press design is the steel frame. Because of the magnitude of the stresses created within the frame during pressure filtration, detailed analysis is necessary to engineer equipment with an acceptable service life while minimizing weight and cost.
During pressure filtration, tens of thousands of pounds of force are produced within the filter plate stack. That force is trying to push the filter plates apart. The frame of the filter press must be designed to counteract that force in order to maintain a seal on the filter plate stack. A typical 800 mm filter press has a closing force of 104,000 pounds and is cycled 4,000 times, or more, each year of service.
A filter press may not fail under initial stress, but may fail due to fatigue caused by normal operation – the repeated opening and closing of the press. Detailed structural analysis is required to identify and eliminate areas subject to fatigue in order to maximize the life of the press.
We always recommend equipment that most appropriate for the application without exceeding the project requirements and incurring additional expense. This isn’t guesswork.
Once an order is placed, M.W. Watermark’s engineering team draws upon their experience in the field as well as 3D design and analysis tools to generate a safe and reliable filter press design. We use Finite Element Analysis (FEA) to validate our designs and identify potential structural deficiencies to avoid failure in the field. This way, even one-off custom filter press designs can be reliably built to provide decades of service.
Typical Design Question
Can a filter press follower be designed to be lighter, stronger, and still provide maximum safety and functionality? What is the required thickness of the stiffeners? Can non-essential material be removed to reduce weight?
More steel does not necessarily result in a stronger or more fatigue-resistant filter press. In fact, excess steel increases the cost and results in a heavier piece of equipment that may still experience failure.
M.W. Watermark engineers focus on safe and functional equipment designs, including safety factors that meet or exceed industry standards, without including excess material.
Recently we had a customer in the market for a new filter press who was very interested in follower design. The company had recently had an expensive repair on their existing filter presses due to inefficient design.
The box construction of their current follower allowed for a permanent deformation where the cylinder load is concentrated. When the cylinder was serviced they found the deformation so great they could not unbolt the follower. This lead to a production shut down – a major operational expense.
When visiting our facilities, they shared this design concern with us and we were able to demonstrate that our filter press would not experience this deformation using finite element analysis. See the video below.
Video: Finite Element Analysis & Follower Design
This is our follower design. Using Finite Element Analysis (FEA) our engineers can check its anticipated stress and displacement to guarantee against failure and to calculate the maximum cycle expectancy.
First, they determine the maximum load size the steel can handle. In this case, it’s 384,000 pounds.
The arrow indicates where the force is being applied. The 384,000 lbs. of pressure will want to bend the steel as it is sandwiched between the cylinder and the filter plate stack.
Next, they determine the safety factor, which is the ratio of the actual load within the steel members to their yield point. We also look to see that this load ratio is uniformly distributed throughout.
We then focus on areas of high stress (indicated by the color red). High stress areas must have a minimum safety factor of 1.6 to be acceptable.
Using animation we can see how the follower reacts to stress as the load ranges from 0 to 384,000 lbs. of force.
On the face of the follower, we’re looking for uniformity of stress, which has been achieved.
Finite element analysis is one of the tools we use to design and build the safest, highest quality equipment at the right price.
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