Valves are used in a wide range of applications for gases and liquids. They are essential in controlling the flow of a liquid or gas in a given direction. Compressor valves are particularly important as they require precision engineering and excellent reliability. They are often used in high-pressure applications. Today we are going to look at the different types of compressor valves and explain how each is used.
What is a Valve?
At its most basic, a valve is simply a device that controls the flow of a liquid or gas in a given direction. It generally has three positions.
- Fully open – Where an element can flow in both directions
- Fully closed – where no liquid or gas can move in any direction
- Partially open – The valve creates an obstruction that only permits flow in one direction
Understanding Pressure Differentials
As a general rule, for a gas or liquid to flow, there needs to be a difference in pressure across a given medium. This is referred to as a differential. If the pressure on either side of a valve is equal, there will be no flow.
When trying to understand pressure differentials, it is vital to understand that high-pressure elements will always flow towards low pressure.
If you envisage squeezing a bottle filled with water, you increase the pressure inside the bottle while the pressure outside remains the same. Across the bottle, the opening is a pressure differential, and the high pressure flows towards the low.
If you placed a valve across this opening, you could accurately control the flow. In essence, this is what compressor valves do, only at much higher pressures.
What Are Compressor Valves Used For?
Just as with our bottle analogy above, a compressor increases the internal pressure of a liquid or gas in a cylinder. Compressor valves allow the movement of this gas or liquid in a given direction based on a set differential. With a strong enough pressure on one side of the valve, it will open until such time as the differential closes the valve again.
Because compressor valves deal with very high pressures, it is vital that they are created and serviced to very precise tolerances and need to be consistently reliable. Any failure could be dangerous, and as valves will operate millions of times each day, they need to be durable.
The Three Types of Compressor Valve
As we have seen, valves are simply a way to control the direction and pressure of an element. There are some common parts that are specific to all of the following types of compressor valves.
The common parts:
- A valve seat – this forms the bulk of the valve housing and is what the other two parts are mounted upon
- A moveable valve part – this valve part can take many forms. Its movement is what regulates the flow of a liquid or gas. It can be closed using spring pressure or reverse flow from the opposite side of the valve in certain cases.
- A stop plate – as the name would suggest, this element is attached to the valve seat utilizing a fastener or bolt and limits how far the valve can move. You’ll find all of the above or similar in all of the following types of compressor valves.
Plate valves are, in essence, exactly as we have described above. Due to their simple construction and high-pressure durability, they are perfectly suited to gas applications.
Another key benefit of plate valves is that they can be constructed using different materials to withstand the corrosive effects of certain gases, such as hydrogen sulfide.
You’ll find that some plate valves contain damping discs. This is because the valve may seal and unseal at a rapid speed and frequency. The damping disc will slow this effect and reduce the stress and strain placed on the plate.
Radiused Disc Valves
Radiused disc valves are utilized in compressors in the petrochemical and air separation industries. They are ideal for high-pressure and high-temperature applications.
Again, envisage the plate sandwiched between the valve seat and stop plate. In the case of Radiused disc valves, the stop plate allows liquid or gas to travel through holes bored in circles (or radii).
The valve plate is formed by a connected series of rings forming a seal between the stop plate holes. Due to their shape, they are self-aligning and will still work even if slightly deformed due to heat or pressure.
Unlike plate valves, radiused disc valves are nearly always produced using thermoplastics specific to the application of the compressor. Thermoplastic valves are considered much more durable as they don’t nick or scratch as readily as metal parts.
High Flow Valves
High flow valves are most commonly used in applications where debris and particles may be present in the gas or liquid being compressed. Whereas radius disc valves have radii (or circular) shaped valve seals and seats. In the case of high flow valves, these are shaped in a pointed or “V” shape.
Why does this “V” shape help?
A point is aerodynamic and hydrodynamic, meaning the gas and liquid flow resistance is greatly reduced when the valve closes, leading to fewer pressure drops across the valve.
Also, due to the slope of the valve, particles are more likely to be ‘shed’ as the valve moves, increasing durability.
Due to the nature of their operation, high flow valves and components are engineered to extremely tight tolerances.
All of the above valves can be provided, serviced, and repaired by Samco Enterprises. Based in Houston, Texas, Samco has provided valve and compressor solutions for over 40 years and supplies compressor valves and parts to the petrochemical industry over the entire Gulf Coast.
With rapid exchange programs, valve design and manufacturing, and expert analysis of valve failures offered, we are the go-to solution for compressor parts and service. Contact Samco today to find out what we offer!