Tuesday, February 21, 2017

Case Study From CSB: Industrial Plant Heat Exchanger Explosion

large shell and tube heat exchangers at industrial chemical plant
Primary and secondary heat exchangers, similar to the setup
in the re-enactment video
Industrial accidents, whether minor or catastrophic, can serve as sources of learning when analyzed and studied. Operators, owners, and technicians involved with industrial chemical operations have a degree of moral, ethical, and legal responsibility to conduct work in a reasonably and predictably safe manner without endangering personnel, property, or the environment. Part of a diligent safety culture should include reviewing industrial accidents at other facilities. There is much to learn from these unfortunate events, even when they happen in an industry that may seem somewhat removed from our own.

The U.S. Chemical Safety Board, or CSB, is an independent federal agency that investigates industrial chemical accidents. Below, find one of their video reenactments and analysis of an explosion that occurred at a Louisiana chemical processing plant in 2013. A portion of the reenactment shows how a few seemingly innocuous oversights can combine with other unrecognized conditions that result in a major conflagration.

Check out the video and sharpen your senses to to be aware of potential trouble spots in your own operation.

Wednesday, February 15, 2017

Trunnion Mount Ball Valves

stainless steel trunnion mount ball valve flange connections
One example of many variants for
trunnion mount ball valves
Courtesy HS Valve
A ball valve is generally a well understood industrial valve design. Its simple quarter turn operation, bidirectional sealing, compact form factor, and tight shutoff capability make the ball valve a preferred choice for many applications. The many variants of industrial ball valves can be grouped into two categories, distinguished by a primary design feature, the mounting of the ball.

The two designs are known as floating ball and trunnion mounted ball. Floating ball valves use the seats and body to hold the ball in place within the fluid flow path, with the force of directional flow pushing the ball against the downstream seats. The floating nature of the ball limits the applicability of this design to smaller valve sizes and pressure ranges. A some point, the fluid pressure exerted on the ball surface can exceed the ability of the seats to hold the trim effectively in place.

Trunnion mount ball valves employ the stem shaft and, you guessed it, a trunnion to support the trim. The shaft and trunnion, connected to the top and bottom of the trim, establish a vertical axis of rotation for the ball and prevent it from shifting in response to flow pressure. A trunnion is a pin that protrudes from the bottom side of the ball. It sits within a bearing shape, generally cylindrical, in the base of the body.

Because of their structural design, trunnion mount ball valves are suitable for all pressure ranges and sizes.They are used by many manufacturers as a basis of design for their severe service ball valve offerings. A trunnion mount ball valve can also be advantageous for applications employing valve automation. Since the ball is not held in place by a tight fitting seal arrangement, operating torque tends to be lower for comparably sized trunnion mount valves, when compared to floating ball valves.

Whatever your valve application challenge, share it with an industrial valve expert. The combining of your process expertise and experience with their product application knowledge will yield an effective solution.


Wednesday, February 8, 2017

Floating Ball Valves

exploded view of floating ball valve
Exploded view of floating ball valve
Courtesy HS Valve
Ball valves are used throughout fluid based applications, from residential to heavy industrial. The compact and rugged design of this valve type provides superior service when properly applied. There are many variants of the basic design, with manufacturers providing builds that meet very specific and stringent requirements posed by certain types of industrial process control applications.

Ball valves are named for the spherically shaped element encased in the valve body directly in the fluid flow path. The ball has a hole, or port, through it’s center, permitting fluid to pass when the port is aligned with the direction of flow. A stem is attached to the ball and extends to the exterior of the valve body, providing a mechanical means of rotating the ball between open and closed positions. Ninety degrees of rotation moves the ball from the fully open to fully closed position. Ball valves are generally suitable for manual or automated operation.

In the basic design of ball valves, there are two groups which exhibit an essential structural difference that is worth mentioning. There are two ways in which the ball in a ball valve is held in place. A floating ball valve has its main trim element held in place by the shape of the valve body and the seats. It is essentially suspended in the flow path by its surrounding parts. A very small amount of lateral movement of the ball is imparted by the fluid flow, pushing the ball tightly against the seat on the downstream side. This attribute enables a floating ball valve to provide tight shutoff of bidirectional flow. The floating ball design proves less effective as the nominal bore size increases. The added weight of the larger ball, coupled with the larger surface area exposed to fluid forces, can overcome the ability of the seals to properly support the ball and maintain good performance. The maximum size can vary among manufacturers.

Enjoying all the benefits of ball valve design, plus being comparatively simple to disassemble and service, floating ball valves are a solid choice for many industrial applications. Selecting the right valve design or type is an important step toward effective control of fluid operations. Share your fluid process control challenges with a valve expert, combining your process knowledge with their product application expertise to develop effective solutions.