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Premier Product Manufacturing & Craftsmanship

Segmented Seal Rings

Graphite is an ideal material for steam turbine packing rings, secondary containment seals, and blower rings. Our rings feature precision manufacturing and spacial material grades for optimum sealing performance and long service life. 

Materials

Graphite grades used are from our Group C graphite, Group B and Group A materials (see page 8). These grades have a fine-grain structure with excellent mechanical properties. Retaining (or “garter”) springs are made from lnconel (for temperatures above 700° F) or stainless steel. Stops are made from stainless steel, cadmium-plated steel, or bronze.

Availability

Over the past 40 years, we have compiled a comprehensive database of 20,000 cross reference part numbers. If you can supply model number or OEM part number, we can quickly determine the correct ROC part number and provide a quote or ship the part immediately if stock is available.

Precision Manufacturing

Sealing effectiveness of ROC Carbon turbine rings is achieved by a combination of careful design and painstaking craftsmanship in manufacturing. Shaft clearance calculations take into account the coefficient of thermal expansion of both the shaft material and the selected carbon/graphite grade as well as the exact operating temperature. Typical segment ends are either overlap or light-tight butt joints, and each joint is matched and marked. Ring faces are given a commercial lap finish.

Technical Services

ROC Carbon’s engineering staff is available to help you evaluate seal problems and to recommend solutions involving seal geometry and material. For nonstandard parts on modified machines, we will recommend the proper turbine ring ID if you furnish steam conditions and shaft size.

For original Equipment Replacement Parts, Please Furnish

The OEM part number or the specifications of the machine. For custom-designed parts, furnished engineered. Drawings can be made available. If you wish, we will design a seal for you.

ROC Carbon manufactures carbon/graphite seal faces to OEM specifications, working from your drawings or samples and using the same high-quality materials and tolerances that original equipment manufacturers use. ROC is experienced in machining intricate details, such as flow channels and ports. Our lapping capabilities encompass both carbon and hard faces up to 17 inches in diameter and flatness as tight as 2 helium light bands. We can insert the carbon seals in metal housings (machined by us or furnished by you) by heat shrink fitting or by using specialty adhesives.

ROC Carbon’s engineering staff is available to help you evaluate seal problems and to recommend solutions involving seal geometry and material.

Piston rings are used in reciprocating compressors, control valves, poppet valves, and other similar applications. The primary sealing surface is the contact between the OD of the seal and the cylinder wall. For some designs, a separate spring expander is required on the ID of ring to energize (push) the segments to the cylinder wall. The secondary sealing surface is the contact of the face of the ring and the face of the piston ring groove. Multiple rings are usually needed to seal the high pressure in the cylinder.

ROC Carbon self-lubricating bearings and bushings are available as standard. replacement styles or custom-designed parts for specific operating problems. Parts range from simple sleeve bushings to complex styles incorporating notches, grooves or metal reinforcing sleeves.

High-Performance Materials

Carbon/graphite grades selected should be compatible both with the fluids being handled and the operating parameters. The typical grades used are as follows:

  • Material Group A is resin-impregnated for abrasive & food applications
  • Material Group B with anti-oxidant impregnation is used for higher operating
  • Both Material Group C and Material Group F are used in general purpose applications temperatures
  • Material Group E is metal-impregnated for improved heat dissipation, wear, and strength characteristics. Depending on the application, various types of metal-impregnation can be used. 

Press fitting & shrink fitting

For metal-reinforced styles, the method used to assemble the carbon into the metal housing depends on the carbon grade used, the metal selected, and the operating temperature.

Cold Press fitting is generally used for low-temperature applications, where relatively low interference is needed to keep the carbon from rotating independently. Heat shrink fits are used for high temperature applications requiring greater interference to prevent carbon rotation.

ROC Carbon’s engineering staff can help you evaluate bearing and bushing problems and recommend solutions involving seal geometry and material. For nonstandard parts used for modified machines, we can recommend the proper bore sizes and materials for optimum performance.

ROC Carbon Type MB carbon/graphite compressor seal rings are typically double-face seals that provide a critical seal to prevent fugitive emissions. The seals are installed over the shaft, sandwiched between the rotating seal face and stationary face. Carbon’s hardness and graphite’s lubricating properties combine to deliver long service. Type MB compressor seal rings have an outer metal ring to reinforce the carbon/graphite and preserve seal geometry at high speeds, while maintaining a constant gap between the shaft and the ID of the seal.

ROC metal-backed seals are available in both standard replacement styles and in custom configurations to solve specific operating problems.

Precision Manufacturing

Seal geometry is extremely important to service life. The two seal faces must be identical so that the seal rotates at one-half speed relative to the rotating seal ring, subjecting both seal faces to the same wear rate. If not identical, one seal face will wear excessively, shortening seal life. ROC seal surfaces are lapped and polished to within 1 helium light band (less than 12 millionths of an inch) for optimum sealing performance. Precise machining also produces perfectly round seals, preventing vibration that causes premature seal failure.

Shrink-Fitting and Stress Relieving

To prevent stress buildup that can shorten seal life, ROC Carbon follows a proprietary procedure that shrink-fits the metal ring over the carbon/graphite followed by re-stabilizing the seal before final machining. To further assure optimum geometry, larger ROC Carbon Type MB seal rings are shipped with a carbon/graphite plug that helps prevent seal damage during storage and handling. The plug is removed prior to seal installation.

Materials

Carbon/graphite grades are chosen to be compatible with the fluids being handled and with the mating seal surfaces. Typical carbon grades used are in our Materials Group A, with Shore Scleroscope hardnesses ranging from 77 to 95 (see page 8). For operating temperatures above 500° F, metal-impregnated carbon/graphite is used. The metal also has the appropriate corrosion resistance for the intended service.

ROC Carbon offers bronze bushings with graphite plugs, ideal for applications requiring self-lubrication and wear resistance. The bronze provides strength, and embedded graphite acts as a solid lubricant. These bushings excel in high-load, low-speed scenarios where traditional lubrication methods are impractical. They demand minimal maintenance, offer some corrosion resistance, and function in wet and dry conditions and across a broad temperature range.

ROC manufactures labyrinth seals up to 12 inches OD for all makes and models of turbines. Our CNC machining capabilites include the full range of tooth configurations: straight, stepped, angled, staggered, and more. We work from your drawings or samples. Custom sizes and fast delivery are our specialty.

These seals (typically two-piece) are precision-machined at our Houston facility. To match virtually any application, we offer the following materials:

  • bronze
  • aluminum
  • nickel-silver alloy

ROC Carbon can help you with your stator bushing repair jobs. We offer 2 types of services for these types of parts. 

One option is to have us install new carbon bushings in to the original housings. We will remove the old worn bushings, inspect for damage, and then clean/sand blast the metal housings and install new bushings.

A second option is to have us supply complete new parts (metal housing with carbon bushings). We can reverse engineer the parts from a sample, or work directly from your drawing.

ROC Carbon offers custom-machined bronze bushings and bearings for applications where bronze alloys are more suitable than carbon-graphite for impact strength, resistance to corrosion, and durability against abrasives. Numerous bronze alloys are available. We machine bushings for pumps, sumps, turbines and other equipment. Our CNC manufacturing center can machine straight or spiral ID grooves, and we also offer two-piece bushings with milled split lines.

To get started, supply your drawing and specifications or send samples so that we can reverse engineer replacement parts.

Waterjet cutting is a versatile, high-precision cold-cutting process that uses a high-velocity (Mach 2 to Mach 3) stream of water to efficiently cut a wide range of materials, producing parts in a wide range of sizes, down to tiny pieces.

The waterjet with entrained garnet abrasive cuts stone, concrete, glass and metals, including titanium, stainless steel, lnconel, and ceramics including alumina.

Waterjet cutting is ideal for short-run part production, just-in-time manufacturing, tooling, and prototype part development.

Advantages of Waterjet Cutting

  • Materials can be conserved by nesting parts on the cutting layout
  • Little material loss from cutting
  • No heat-affected zones or mechanical stresses on cut objects
  • Cuts extremely fine details
  • Little or no burr
  • Efficiently cuts extremely hard materials

One of ROC’s waterjet cutting machines is an OMAX
Model 5555, which has a 55 in. x 55 in. work envelope.

Ball valve seats are the primary seal in a ball valve. Typically the seats are made from PTFE for lower temperatures, carbon for higher temperatures, and metal for the highest temperatures. The valve seats support the ball during the open/partially open position. When the valve is closed, fluid pressure in the pipe pushes the ball toward one of the seats. This action creates a seal since the seat has been lapped to the ball during the manufacturing process.

Manufacturing

With PTFE, the seat is machined as a single component. Because PTFE conforms to the ball surface, lapping the seat and ball is not necessary. 

Blower systems typically employ various types of seals to ensure effective operation. These include labyrinth seals, which use intricate channels to obstruct the passage of air or gases. Segmented carbon seals utilize segments of carbon material to create a tight barrier. Mechanical face seals rely on two precisely engineered faces to prevent the escape of fluids or gases. Each type serves a specific purpose in maintaining the integrity and efficiency of blower systems.

Segmented blower seal