Top Hat Assembly for Viscous Service Reduces Product Buildup

Situation

In viscous service applications where viscous fluids are flowing, product buildup between the process and the rupture disc is a concern. In some cases, this buildup can interfere with the proper operation of the disk during an overpressure event. Viscous service holders are typically designed with diaphragm valve bodies to allow for the installation of a rupture disk. These valve bodies are machined to divert the flow and “sweep” it past the rupture disc to minimize product buildup. However, the diaphragm valve body design presents a number of challenges. The valve body must have the same size and pressure rating as the rupture disc. If the right valve body is not be available, the only alternative is to custom machine or cast a body to suit a particular application. Additionally, the diaphragm valve body design has many bolted joints, which create additional leak paths for the assembly. The custom machined or cast body is also much more expensive due to the increased amount of raw material and capital cost for tooling up for each configuration. OsecoElfab was tasked to find a way of overcoming these challenges while still providing a cost-effective solution.

Goals

1. Quantitative: Design an affordable rupture disc assembly for viscous service applications.
2. Quantitative: Reduce the resistance to flow of the viscous service holder.
3. Qualitative: Reduce possible leak paths present in viscous service holders

Solution

The Oseco Top Hat Assembly has been specifically designed for viscous services where product buildup between the process equipment and the rupture disc is a concern. It solves three specific challenges:

1. ‍Product pockets or buildup: The Top Hat Assembly's design places the disc as close to the flow of media as possible to eliminate product pockets and buildup.
2. Leakage around the rupture disc seating area and rupture disc body: In the Top Assembly the disc is welded directly to the top hat, creating a single-piece tee design that eliminates leakage.
3. Torque of flange studs creates challenges: As a single component, the Top Hat Assembly removes the need for additional bolted joint or multiple components, and it is not sensitive to torque.

Types of process media where a Top Hat Assembly can add value include slurry (typically in mining), sulfur recovery units, emulsions (including paint), and chocolate, as well as oils, resins, and syrup or sauces in the food and beverage industry.

Design Comparison

Viscous service holder

The geometry of the body creates a higher resistance to flow compared to a straight pipe. Diaphragm valve bodies must be used but they can be expensive and difficult to procure. Multiple components means this assembly can be difficult to maintain and install.

Top Hat Assembly

The Top Hat Assembly eliminates the curve in the valve body. This reduces the assembly’s resistance to flow while still providing flowing fluid over the rupture disc surface. Standard piping and flanges replace the diaphragm valve body, making the top hat more affordable to implement. Leakage at the seating area of the rupture disc assembly is eliminated as the disc is welded to the end of the top hat (shown in blue).

Tank Service

The top hat rupture disc assembly is also suitable for pressure vessels in viscous fluid applications. Here, it can eliminate the blockages that occur with typical rupture disc and valve technology caused by polymerization in the dead head space between the rupture disc and vessel.