concentric valves


Suction and Discharge Valves are critical components for the performance and reliability of reciprocating compressors. Their floating internals produces continuous opening and closing cycles, reaching up to 1.5 million per day in compressors that operate at 1,000 rpm. Should the operational dynamics not be ideal, these parts will be subject to premature breakage, leading to valve failure. According to several studies, in over a third of the reciprocating compressors, non-programmed stops are related to valve problems.

Our valve projects consider an ample array of advanced thermoplastics and special steels.

Why Selco?

Selco valves are recognized for their performance and reliability across many industries. They are resistant to high temperatures and pressures, as well as to different acidity and humidity conditions.

Selco is proficient in valve-performing calculations. They run simulations are run on the sealing components’ movements, thus providing diagrams of pressure-volume, load and power losses, gas passage speeds, impact, and isentropic and volumetric efficiencies. The efficiency of every valve under different compressor operational conditions is anticipated during its project development.

Valve projects consider an ample array of last-generation thermoplastics and special steels.

Selco’s portfolio of exclusive projects includes Sc-Disc, Sc-Convex, Sc-Plus, Sc-Convert, Sc-Modular, Sc-VR, and Sc-Trust.The company also supplies any existing valve models

Piston Rings

Reciprocating compressors use Compression Rings to seal gases in their compression chamber. These components are critical and require high performance and a long lifespan, for their sealing efficacy is essential to the compressor performance.

Guide Rings guide the piston movement inside the cylinder. They are essential components since project errors may cause piston wear onto the cylinder liner, damaging the compressor.

Why Selco?

Selco holds the knowledge of the processing and sintering of thermoplastic materials applicable to producing sealing components for reciprocating compressors. Internal production has advantages in its total control and traceability of raw materials.

The company uses various thermoplastic materials (PTFE with loads and PEEK) applicable to multiple production processes. Depending on material choices, the rings are adequate to operate at average piston speeds from up to 6m/s, maximum pressures of 350 bar, and operating temperatures of up to 200°C (392°F). The rings support humid and dry gases over various molecular weights, contaminated or corrosive.


Packings (sealing elements) perform the dynamic seal of gases compressed inside the cylinder. They also direct waste and purge gases to safe areas or back to the pipeline to be compressed again.

Packings are either primary or secondary (pre-packing). Primary ones are mounted on cylinders near the compression chamber, while secondaries are mounted on intermediate housings.

Why Selco?

A complete line of packing elements is designed and manufactured for reciprocating compressor’s rod sealing systems, all done in conformity with specific (API618) norms or as per client request. All packings with additional lubrication, cooling, vent, and other systems are subjected to final inspection and quality tests. The company also develops conversions of existing packings to projects with purge control for applications requiring emissions control or using toxic or corrosive gases.

For compliance, a diverse array of packing rings is made of materials specific to each application. The ring design considers a compensation of wear caused by rod movement and temperature changes. The packing rings are made of different metallic and non-metallic materials and come in various models for either standard or specific projects.

Modern machining centers are used in production processing and equipment and fixtures specifically developed by Selco’s technical team, allowing the assurance of adequate sealing conditions.

Selco is knowledgeable in the processing and sintering of thermoplastic materials applicable to producing sealing components for reciprocating compressors. The company uses various thermoplastic materials (PTFE with loads and PEEK) applicable to multiple production processes. Internal production has advantages in its total control and traceability of raw materials.

Pistons, Rods, and Liners

Pistons are located at one of the Rod extremes and operate inside the reciprocating compressor cylinder as a moving barrier. Light materials such as aluminum or steel may be produced with a hollow interior to reduce weight.

Rods convey reciprocating movements of crossheads to pistons.

Liners allow the compression of gases and prevent cylinder wear. They must be resistant to support high pressures and temperatures.

Why Selco?

Selco develops and supplies compressor pistons, rods, and liners for various applications and operational conditions. The products are made of a complete array of special metals such as aluminum, gray and nodular cast irons, stainless steels, and alloy steels, among others.

The company’s knowledge of reciprocating compressors – conceptual and operational – allows an understanding of all mechanical demands. An experienced technical team works in the development and specification of those components. Through finite element analysis (FEA), adequate safety factors are assured, minimizing costs while holding no parts at risk.

All products and services are developed to meet or re-establish original compressor conditions and new working conditions (REVAMPs). The international technical requirements and specific standards, such as API 618, DIN, and NR 12, are applied during project execution.

Pistons, rods, and liners are critical compressor components that require specific tests and trials to assure integrity and reliability. A team of engineers and quality control inspectors is fit to execute and follow up on non-destructive, chemical, and mechanical trials of these components during the manufacturing process.

Oil Scrapers

Oil Scrapers prevent oil contained in the force system (from the carter region) empty through the rod. This type of leakage can generate problems, among which excess oil consumption, contamination of the compressed air and work environment, and packing sealing malfunctioning. Specific reciprocating compressor components require constant and abundant lubrication.

Why Selco?

Oil Scraper conventional designs may present low efficiency, leading to excessive lubrication oil consumption. Additionally, damages that reduce the rod life span may surge. Selco scrapers offer good profiles and compositions to prevent such risks.

Selco offers a great variety of single and double-effect oil scrapers. Metallic and thermoplastic materials are adequate for different mechanical and operational compressor conditions. Its products are used in several industries, presenting high field-proven efficiency.

The company develops oil scrapers for particularly demanding applications and solves specific problems, including vertical compressors.


    Contact Us



    Our Concentric Valve Brands

    © 2024 Website Developed by MacRAE'S