The Importance of Compressor Cylinder Sizing
Does compressor cylinder sizing matter? Indeed it does. Read all the details on the importance.
Compressors in chemical, petrochemical, and gas industrial processes are composed of multiple components. Each of these components provides a specific function that supports the functionality of the equipment. For example, some of these components help manage heat, narrow gas flow, boost the equipment’s durability, aid in rotation, etc. All these enable other aspects to perform their tasks as efficiently as possible.
One of the essential components of a reciprocating compressor is cylinders. Cylinders are pressure vessels containing the gas that is to be compressed by the machine during the compression cycle. Two basic types of cylinders for compressors exist:
- Single-acting cylinders
- Double-acting cylinders
The primary function of single-acting cylinders is to compress gas in one direction of piston travel. They can be the crank end or head end. On the other hand, double-acting cylinders work by compressing gas in both directions of piston travel. Most active reciprocating compressors make use of double-acting cylinders for more efficient output.
The function of reciprocating compressor cylinders is to assist in cooling the temperature of the equipment during its compression cycle. This action often generates heat, hence the need for cooling during operation.
The best way to reduce the compressor’s temperature is by using a water jacket or fins in the cylinder that provides cooling air.
Cylinder Materials
Cylinders are generally made of different types of materials. But in many cases, cast iron is the material used in making cylinders designed to operate under pressures ranging from 1,000 to 1,200 psi.
Nodular cast steel or iron is the material used in fabricating cylinders that function with operating temperatures that range from 1,000 to 2,500 psi. In contrast, forged steel is used in crafting cylinders operating with pressures greater than 2,500 psi.
Compressor cylinders have a maximum allowable working pressure, just like every pressure vessel you know. However, the maximum permissible working pressure of a particular cylinder greatly determines the overall setting of the relief valve downstream of the cylinder.
A compressor cylinder’s maximum allowable working pressure should be at least 10 percent or 50 psi greater than its typical operating pressure.
Cylinder liners can be used to extend a compressor cylinder’s life span and boost its operating flexibility. However, any damage that occurs due to the heat generated during the compression cycle or the action of the piston will significantly affect the cylinder liner.
The cylinder liner is a removable item, meaning a damaged one can easily be replaced. Damage to the cylinder liner is evident when its surface starts wearing out. It is quicker or easier to repair or replace a damaged cylinder liner than the cylinder itself.
In addition, cylinder liners enable the variation of the diameter of the piston with zero changes to the cylinder itself, thereby providing much-needed flexibility in order to respond swiftly to different flow rates and pressure conditions.
Why Compressor Cylinder Sizing is Important
In order to specify a particular unit, it is essential to provide vital information such as:
- The suction and discharge pressures
- Inlet temperature
- Gas properties
- Capacity (MMscfd)
The manufacturer is primarily responsible for determining the actual sizing of the compressor cylinder as a result of specified combinations of pistons, liners, and standard cylinders.
However, it is highly recommended to check the cylinder sizing even after receiving a proposal from your manufacturer. This is to ensure the compressor cylinder is as designed or intended.
You may need to size a brand-new cylinder for an existing reciprocating compressor or verify that an existing machine performs remarkably well for a different service.
The capacity of a compressor cylinder is a primary function of volumetric efficiency and piston displacement. This is, in turn, a function of compression ratio, cylinder clearance, as well as gas properties.
Reciprocating Compressor Cylinders and Cooling Systems
As power passes through a reciprocating compressor, it converts to heat during compression cycles. This heat needs to be eliminated from the entire system or compressor. This is where a cooling system comes in.
The cooling system in a reciprocating compressor helps to get rid of the heat from the equipment. It also boosts the efficiency of multistage reciprocating compressors by increasing air density between every compression stage.
The cooling system also ensures that the numerous compressor components and compressed air or gas don’t reach extremely high temperatures.
For these reasons, compressor cylinders are generally cooled by passing seawater or freshwater through them. The water absorbs the heat and is circulated through several cooling water passages within the cylinder block. This is why cooling systems are vital in compressors’ proper or appropriate functioning.
Water-Cooled and Non-Cooled Compressor Cylinders
As mentioned in the previous section, conventional compressor cylinders are cooled using cooling water jackets. These help in the uniform distribution of the heat generated during compression cycles.
The immense benefits of this action include:
- Prolonging life span of components
- Reducing suction gas preheat
- Cylinder lubrication
- Minimizing maintenance time
However, there’s another way of cooling heated compressor cylinders. These cylinders don’t require water for cooling; hence they are known as non-cooled compressor cylinders.
Non-cooled compressor cylinders have been in action over the last 30 years and have performed remarkably well without the need for cooling water jackets. Every operation that non-cooled compressor cylinders have undergone within this period – and in several natural gas compression applications – has been massively successful.
Using non-cooled compressor cylinders has several benefits. However, the most significant advantage of a non-cooled compressor cylinder is its simplified design, which brings about a hugely minimized cost of setting it up.
The design of non-cooled compressor cylinders also offers lower initial system costs due to reduced weight, enhanced valve accessibility, and considerable reductions within the cooling water system.
Conclusion
Compressor cylinders are vital pressure vessels that hold the gas to be compressed during compression cycles. Therefore, it is one of the crucial components in a reciprocating compressor.
The importance of compressor cylinder sizing cannot be overstated. The peak performance of a reciprocating compressor is ensured when the cylinder is of the ideal or appropriate sizing. Conversely, anything more or less than the correct cylinder size can negatively impact the overall performance of the equipment.
From industry standards like Ariel compressor parts to Ingersoll Rand and Cooper Bessemer compressor parts, we carry compressor parts you can trust and the service you can count on.