The Basics of Check Valves
The check valve ensures that fluids travel in one direction and won’t back up and get into areas where they are not supposed to go.
Anyone working on a ship where engine rooms or other functional areas are enclosed in tight spaces knows that the check valve plays a very important role. All you need to think about is an oily fluid kicking back onto a hot engine. Properly functioning check valves, therefore are critical.
Common check valves
The Swing Check Valve contains a disk that swings away from the seat to allow fluids to flow forward and then returns to the seat to prevent backflow.
swing check valve
Lift Check Valves operate in high-pressure applications and the movement of the internal part is like a piston. The flow enters below the seat of the valve and raises the piston or ball.
When the flow stops, the piston returns to the seat preventing backflow.
lift check valve
Source: Wermac.org
A Butterfly Valve contains a wafer in the middle that twists to control the flow of fluid. A spring can be added to prevent the reverse flow of fluid when pressure drops.
Stop Valves can be opened and closed by hand or electronically depending on the product. The function of this part is pretty straight forward. There is “open” and “closed” and generally this is controlled by ship operators. For automatic operation, this is not the product you want, but for control by a person, this is it.
Tilting Disc Check Valves are found in lower pressure applications. They are built just like the name suggests. The flow of liquid causes the disc inside to tilt. It closes again when the flow disappears.
With any valve aboard a ship or service vessel, proper setup and maintenance will determine how long the part lasts and how well it performs. Understanding the construction of your check valves is only the first step.
