Absolutely Leak-Proof – HOERBIGER solves the
Leakage Problem of Reciprocating Compressors
Conventional packings for compressor piston rods tend to suffer from latent gas leakage. The new sealing system HOERBIGER XperSEAL marks an innovative technological turning point. The zero leakage technology of HOERBIGER XperSEAL is based on a known principle: a pressurized volume of oil completely surrounds the reciprocating rod, forming an insurmountable barrier for the gas compressed in the compressor. This creates reliable, no-leak sealing for the entire service life of a compressor. The radically new sealing system is fail-safe, easy to retrofit in all existing compressor models, and requires no more oil than conventional lubricated packings.
A conventional compressor packing consists of cut sealing elements, which are movable and surround the piston rod. HOERBIGER XperSEAL replaces these functional elements with a pressurized oil barrier. The volume of oil conforms exactly to the surface of the piston rod, making it impossible for gas to escape as long as the oil pressure exceeds the gas pressure.
Leak-free operation is ensured throughout the entire service life of the compressor. Compared to conventional packings, HOERBIGER XperSEAL even remains tight when the compressor is shut down, allowing no gas to escape.
The oil needed for this new packing technology is supplied by a specially developed HOERBIGER unit, which is included in the scope of delivery of HOERBIGER XperSEAL. This hydraulic unit continuously measures the oil pressure, temperature, and volume in the system, always ensuring the optimal oil temperature due to integrated cooling. As a result, no water cooling system is required for the packing directly in the compressor, eliminating complex cooling channels and gas impurities in the cooling circuit. If the oil pressure should drop unexpectedly, the system automatically switches to an emergency function, which is a vented or rinsed and cleaned mode of the packing.
The idea behind HOERBIGER XperSEAL is simple, and its successful use is based on HOERBIGER's comprehensive hydrodynamics knowledge. The sealing rings are made of specially developed high-performance polymers which keep the oil in place and minimize oil loss. At the same time, design engineers were faced with the challenge of oil escaping from the packing with every stroke.
They solved the problem by employing the hydrodynamic principle, which was previously known for hydraulic cylinders, but had never before been used in compressor packings. HOERBIGER developers designed seals that pump the oil volume back into the packing with the return stroke. As a result, HOERBIGER XperSEAL does not consume any more oil than conventional packings during operation.
The company has intensively tested HOERBIGER XperSEAL in the field, in addition to conducting long-term tests on in-house test benches. Field testing took place in a natural gas collection and treatment plant in the Netherlands, in a natural gas and biogas compressor station within a gas filling station for a municipal city bus operation in Sweden, and in a propane cooling plant in Egypt. The test units have now reliably run for more than 43,000 hours, showing no signs of leakage whatsoever, in all three field applications, and the oil consumption is less than that measured previously in conventional sealing systems. On average, HOERBIGER XperSEAL units consume 0.5 to 1.5 liters of oil per day and packing.
Background: why is HOERBIGER concerned with gas leaks? There are a variety of reasons why operators of reciprocating compressors generally want to prevent gas leakage. There is the cost effectiveness aspect: gas costs money and is too valuable a resource to be wasted through leaks. There is the environmental aspect: natural gas has a very high global warming potential (GWP). And there is the safety aspect: gas that leaks uncontrolled poses an explosion and poisoning hazard.
Modern packings for piston rods are durable because they are made of high-performance materials. Still, since they are wear parts, they form a weak spot in every reciprocating compressor.
A typical oil-lubricated packing for piston rods on a large compressor loses 300 to 1500 liters of gas per hour, which equates to more than six tons a year in a four-cylinder compressor used to compress methane. Experience has shown these losses to be even higher in worn or damaged packings. Close to the end of the life cycle of conventional packings, leakage rates are unacceptably high for equipment operators.
Efforts are made today to reduce the impact of leakage gas on safety and the environment by rinsing the system with nitrogen or burning off the gas. In terms of the environment, however, these are not sustainable solutions for the leakage problem. On the contrary: they create added costs, and the complexity of the plant is increased. Sealing compressors that must be kept under pressure even when not operating results in additional technical challenges and costs.