Reciprocating compressors play an essential role in many industries. Commonly applied in the oil & gas industry, they are used to compress and transport gases efficiently, for example. Another example is using them for the high-pressure hydrogen required to remove the sulfur contained in crude oil. 

They are also known as piston compressors, which gives an idea of the working principle. The machine compresses or pumps gas through the reciprocating motion of pistons powered by the rotational motion of a crankshaft. 

Fundamental in Oil & Gas 

Japanese industrial group Kobe Steel — operating globally as Kobelco — offers a wide range of products and services. Back in 1915, the company produced Japan’s first reciprocating compressor. 

Hitoshi Takagi, Manager of the company’s Reciprocating Section in the Compressor Division, says, “Reciprocating compressors are fundamental machines that form the basis of an oil refinery.” 

Kobe Steel also supplies reciprocating compressors for tankers transporting liquefied natural gas (LNG). Most conventional ships use diesel engines fueled by heavy oil. However, in recent years, dual-fuel engines that run on both heavy oil and natural gas have been put into practical use. 

A greener fuel supply system 

As air pollutants from ships are increasingly scrutinized, such dual-fuel engines can significantly reduce emissions of sulfur oxides (SOx), nitrogen oxides (NOx), and greenhouse gases to comply with stricter regulations. 

Natural gas is a clean energy source that contains almost no impurities. It is transported in significant quantities by LNG tankers, utilizing the fact that it liquefies when cooled to 162 degrees Celsius below zero, resulting in a volume 1/600th that of gas. 

However, it is challenging to prevent vaporization caused by external heat during transportation due to the extremely low temperature. As a result, the vaporized content ends up being discarded as waste. But reciprocating compressors increase the pressure of the vaporized LNG to 300 bar, so 

it can be used as fuel for such dual-fuel engines, providing an environment-friendly fuel supply system. 

Superior vibration dampening 

Although offering rugged and efficient performance, reciprocating compressors generally have a large footprint and can cause many vibrations during operation. Kobe Steel uses Nord-Lock washers as well as Superbolt and Boltight series products to tackle these issues. 

Using Nord-Lock wedge-locking washers improves safety and reliability, reducing the risk that vibrations loosen bolts. In addition, unlike many other companies, Kobe Steel performs vibration analysis and acoustic analysis in-house, resulting in high analysis accuracy thanks to the accumulated on-site data. 

Kobe Steel’s reciprocating compressors are notably quiet. Takayuki Tomochika, Section Head of the Reciprocating Section for Kobe Steel’s Compressor Division, says: “In the 15 years I have been involved in the compressor business, I have never had a customer complain about the noise.” 

More efficient in cramped spaces 

Apart from the compressor, Kobe Steel's packaging services also include the drum, gas cooler, and other equipment, as well as piping and valves mounted on a base. This enables a compact design — a significant advantage given the limited space in LNG tankers. 

These cramped conditions complicate the installation and maintenance of reciprocating compressors. Kobe Steel has found that using Nord-Lock Group tensioning solutions improves work efficiency. They use either Superbolt tensioners or Boltight hydraulic tensioning, depending on the workspace and efficiency of the fastening process. 

The Superbolt series is used to fasten the piston rod to the crosshead on the other side of the piston. Previously, a geared wrench with a long handle was used, but this proved problematic in confined spaces. With Superbolt, a regular torque wrench can fasten large diameter bolts, eliminating the need for space or heavy tools. 

Providing prompt technical support 

Kobe Steel uses Nord-Lock Group's products in machines that must keep running. “We can never stop production because it would cause serious losses,” says Kazuo Kusaba at Kobe Steel’s Machinery Business. 

As compressors continuously get more reliable, the maintenance intervals have lengthened. “But if you can only access the inside of the equipment once every few years, you will not be able to build up the maintenance experience,” Kusaba explains. “This makes it difficult for experienced technicians to pass on their skills to the next generation. 

However, with Superbolt and Boltight, we are now able to quantitatively manage the torque of bolt fastening, which is very encouraging.” 

Kusaba adds that Nord-Lock Japan is different from other companies because they provide prompt technical support, including engineers, for all kinds of issues. He is thankful that Kobe Steel can rely on them. 

With an eye to the future 

Across all industries, environmentally friendly solutions are becoming the norm. The United Nation’s Sustainable Development Goals (SDGs) are crucial for the future and driving this change. 

Kobe Steel is shifting its focus from oil refining to hydrogen energy for the next generation. Their hydrogen compressor units (HyAC® series) are already in use at hydrogen refueling stations, and product development is in progress with an eye to the future.