• CASE STUDY •
Ball Valves for Naval Applications
" To guarantee the first batch of enhanced valves would be onsite for the maintenance window, the upgrade had to be designed, analyzed, tested, and customer verified within nine months."
months. The engineering team brainstormed various concepts to eliminate post shock leakage. Considering the cost, retrofit, and timescale constraints, enhancement of the valve seats was the Prime Candidate.
Floating ball valve seats are typically one-piece polymer designs, where material selection is influenced by numerous variables, including line media compatibility, operating temperature, and operating torque expectations. For this application, it was crucial for the ball to be in contact with a PTFEbased polymer to meet the original operating torque throughout normal conditions.
This would facilitate the use of the originally supplied actuators. The objective by the Worcester team was to house the PTFE element within a resilient polymer housing, carefully engineered to absorb energy and protect it during shock loading conditions( see figure 2).
During normal operation, a floating ball valve is reliant on elastic deformation of the seat to provide the bubble-tight seal to the ball. Low pressure sealing depends on the compressive force applied during assembly to the ball and seat‘ stack.’ This is achieved by building the components into a cavity shorter than their combined height( see figure 3).
Figure 2: One piece PTFE seat photo and cross section showing the ball, seat, and valve body.
Figure 3: Two-piece or hybrid seat photo and cross section showing the ball, hybrid seat, and valve body.
At higher operating pressures, it is the line pressure itself that causes the valve to seal. Since the pressure differential increases, the ball‘ floats’ and is forced into the downstream seat forming the seal.
To enable the ball‘ float,’ it is restrained only by the seats, which is not a concern during normal operation. However, in a shock event, the seats will absorb all the inertial energy from the valve ball acceleration resulting in unwanted permanent deformation.
It is the preservation of this floating mechanism in normal operation and protection from shock impact that must be achieved by the resilient polymer housing.
The defence industry is very attuned to safety critical applications and actively seeks tried and tested solutions to mitigate risk to assets and personnel. With history of supply into defence applications, Flowserve engineers assessed multiple polymers used throughout similar applications to test for a resilient housing. Material testing was commissioned for the shortlisted polymers to enable comparison, along with PTFE to act as a baseline.
Design of the housing was completed by the engineering team. It was further refined using Finite Element Analysis( FEA), improved via the use of the material test results to provide accurate mechanical and physical property data within the FEA software.
Valve World Americas | November 2025 | www. valve-world-americas. com 29