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Mechanical Seals
- Mechanical seals and dry gas seals
- New manufacture
- Repair and refurbishment
- Seal support systems
- Reverse engineering
UNEW Industries manufactures, repairs and reverse engineers shaft seals for every rotating machine in the plant — pumps, compressors, turboexpanders, agitators and reactors, mixers, extruders and pelletizers, blowers and fans. We supply both families of seal: the contacting, liquid-lubricated mechanical seal and the non-contacting dry gas seal. All makes, all sizes, all services.
A seal that fails is rarely a bad seal. It is the wrong seal for the service, the wrong face material, or a support system that is not doing its job. We look at the seal, the machine and the piping plan together, and we fix the cause.
What We Do
| Line | Scope |
|---|---|
| Mechanical seals | Single and dual cartridge and component seals — pusher, metal bellows, high-temperature, high-pressure, slurry, split and agitator seals — to API 682 and to the machine's original seal envelope |
| Dry gas seals | Single, tandem and double dry gas seals with separation seals for centrifugal compressors and turboexpanders; repair, dynamic testing and exchange units |
| Seal support systems | API 682 piping plans, seal pots and reservoirs, coolers, cyclone separators and dry gas seal supply panels — new, refurbished and upgraded |
| Repair and refurbishment | Seals of any make restored to as-new condition, tested and returned with a refurbishment report per serial number |
| Reverse engineering | Replacement seals for obsolete, discontinued or OEM-only designs, manufactured to UNEW technical data |
Equipment We Seal
| Machine | Seals |
|---|---|
| Process pumps | API 610 and ANSI/ISO pumps — overhung, between-bearings, vertical, multistage, high-speed integrally geared |
| Centrifugal compressors and turboexpanders | Dry gas seals and separation seals; oil-film seals on older machines |
| Agitators, reactors and mixers | Top-entry and side-entry seals, dry-running and lubricated, with barrier fluid systems |
| Extruders and pelletizers | Screw shaft seals, melt seals, pelletizer rotor and water-box seals |
| Blowers, fans, screw and reciprocating compressors | Shaft seals to the machine's envelope |
| Steam turbines and boiler feed pumps | High-temperature, high-pressure seals and gland seal packages |
Seals are supplied to replace or interchange with John Crane, Flowserve, EagleBurgmann, AESSEAL, Chesterton, Vulcan, Latty and the seals fitted by pump, compressor and extruder makers, including Sulzer, Ebara, Elliott, Kobelco and JSW. Any other make is quoted on request.
Mechanical Seals
We supply the full range of liquid-lubricated seals, organized as API 682 organizes them, with the special seals the standard does not cover.
| Family | Types | Typical service |
|---|---|---|
| Single seals (Arrangement 1) | Pusher seals with O-ring secondary; rotating and stationary metal bellows; balanced and unbalanced; component and cartridge | Water, hydrocarbons, chemicals, general process duty |
| Dual unpressurized (Arrangement 2) | Tandem seals with buffer fluid or dry-running containment seal | Light hydrocarbons, toxic and flammable fluids, emission control |
| Dual pressurized (Arrangement 3) | Face-to-back, back-to-back and face-to-face seals with pressurized barrier fluid | Hazardous fluids, slurries, crystallizing and polymerizing fluids, vacuum |
| High-temperature | Metal bellows seals with flexible graphite secondaries; cooled seal chambers | Hot oil, hot hydrocarbons, boiler feed water above 200 °C |
| High-pressure and high-speed | Balanced pusher and bellows seals with engineered face geometry | Multistage and high-speed pumps, hydrocracker and pipeline duty |
| Slurry and abrasive | Heavy-duty seals with hard faces, large springs and quench | Slurries, catalyst, coke fines, crystallizing fluids |
| Split seals | Fully split mechanical seals installed without dismantling the machine | Large pumps, mixers and vertical pumps |
| Agitator and reactor seals | Top-entry dry-running and lubricated seals with bearing support and barrier systems | Reactors, polymer vessels, fermenters |
| Extruder and pelletizer seals | Screw shaft seals, melt seals, pelletizer water-box and rotor seals | PP, PE and compounding lines |
Dry Gas Seals
Dry gas seals are a different technology from mechanical seals — a non-contacting gas film between spiral-grooved faces, with a gas supply system that is part of the seal. We repair, test and manufacture them for centrifugal compressors and turboexpanders of every make.
| Configuration | Application |
|---|---|
| Single | Non-hazardous gases, air and nitrogen compressors |
| Tandem | Hydrocarbon and process gas compressors — primary seal with a secondary seal as backup |
| Tandem with intermediate labyrinth | Sour and toxic gases where the primary vent must be isolated from the secondary |
| Double | Low-pressure and toxic services with pressurized inert barrier gas |
| Separation seals | Labyrinth, carbon ring and segmented carbon seals between the dry gas seal and the bearing oil |
Every repaired or new dry gas seal is dynamically tested at speed and pressure on a seal test rig before it leaves our workshop, with the leakage and temperature record in the report. Seal gas panels, filtration, heaters and boosters are supplied and refurbished as part of the seal scope.
Seal Support Systems
Half of seal failures are support-system failures. We supply, refurbish and upgrade the piping plans and the hardware that keep the seal faces cooled, flushed and pressurized.
| Plan | System |
|---|---|
| Plans 11, 13, 14 | Recirculation from discharge or to suction through orifice |
| Plans 21, 23 | Cooled flush — heat exchanger in the recirculation loop; Plan 23 with pumping ring |
| Plans 31, 41 | Cyclone separator flush for abrasive fluids |
| Plan 32 | External clean flush from a plant source |
| Plans 52, 53A / 53B / 53C, 54 | Buffer and barrier fluid systems — reservoirs, bladder and piston accumulators, external circulation |
| Plans 62, 65, 66 | External quench; leakage detection and collection |
| Plans 72, 74, 75, 76 | Buffer gas, barrier gas and leakage collection for containment and dry gas seals |
Seal pots and reservoirs, coolers, cyclone separators, gas panels, instrumentation and level and pressure switches are supplied new, refurbished, or upgraded from the plan originally fitted to the plan the service actually requires.
Materials
| Element | Materials | Selection |
|---|---|---|
| Seal faces | Silicon carbide (sintered and reaction-bonded), tungsten carbide, carbon graphite (resin- and antimony-impregnated), diamond-coated SiC | Hard/hard for abrasive, crystallizing and high-pressure duty; hard/soft for general duty and dry-running tolerance |
| Metal parts | 316 / 316L, Alloy 20, Hastelloy C-276, Duplex and Super Duplex, Inconel 718, Monel, titanium | By fluid corrosivity, chlorides, sour service and temperature |
| Bellows | AM350, Hastelloy C-276, Inconel 718 | Temperature, corrosion and fatigue life |
| Springs | Hastelloy C-276, Alloy 20, 316 | Corrosion and clogging resistance |
| Secondary seals | Viton (FKM), Kalrez and other FFKM, Aflas, EPDM, Nitrile, PTFE, spring-energized PTFE, flexible graphite | By fluid compatibility, temperature and explosive decompression |
Repair and Refurbishment
We repair seals of any make. The removed seal is the best information there is about the service — the inspection reads it before anything is replaced.
Incoming Inspection
| Finding | What it tells us |
|---|---|
| Heat checking, blistering of carbon faces | Loss of lubricating film — dry running, vapor at the faces, insufficient flush or cooling |
| Coking and deposits on faces and springs | Hot fluid without adequate cooling or quench; wrong piping plan |
| Face wear, grooving and edge chipping | Abrasives in the flush; face material not suited to the service |
| Swollen, hardened or extruded elastomers | Chemical attack, over-temperature or explosive decompression — wrong elastomer |
| Fretting of sleeve under the dynamic O-ring | Excessive shaft movement, vibration or misalignment in the machine |
| Hang-up and clogged springs | Crystallizing or polymerizing fluid at the atmospheric side |
| Dry gas seal face scoring, groove contamination | Seal gas contamination or reverse pressurization — supply system |
Refurbishment Process
| Step | Operations |
|---|---|
| 1. Receipt and inspection | Serial record, disassembly, dimensional and visual inspection, failure analysis, repair classification |
| 2. Clean and strip | Chemical and ultrasonic cleaning, removal of deposits and coatings |
| 3. Repair | Face lapping to flatness within light bands; face replacement; sleeve, gland and drive collar restoration by machining, weld build-up and plating; bellows and spring replacement |
| 4. Reassembly | New secondary seals and springs from UNEW stock; set to the original working length and face load |
| 5. Test | Hydrostatic and gas test for mechanical seals; dynamic test at speed and pressure for dry gas seals |
| 6. Release | Refurbishment report per serial number, test record, certificate of conformance; return in protective packing or holding on exchange |
Critical seals are held on an exchange program: a refurbished seal from UNEW inventory is delivered at the outage and the removed seal is repaired afterwards, so the plant is not waiting on a repair during a shutdown.
Reverse Engineering
We hold the technical data for every seal we supply. Where a seal is obsolete, discontinued, available only from one maker, or simply not yet in our library, we reverse engineer it from a used sample and make it a UNEW product.
| Step | Scope |
|---|---|
| Envelope capture | 3D optical scanning and CMM measurement of the seal chamber, shaft, sleeve, gland and every seal component |
| Face and geometry analysis | Face flatness and geometry, spiral groove pattern of dry gas seals, balance ratio, spring load and working length |
| Material analysis | Composition of metal parts, faces and bellows; identification of elastomer and carbon grades |
| Engineering | UNEW drawings, datasheet and bill of materials; material and elastomer upgraded where the failure history calls for it |
| First article | Manufacture, assembly and test; UNEW part number cross-referenced to the original |
From the first order onward the seal is manufactured to UNEW data, and repeat orders, spares kits and repairs are all made to the same data. The plant is no longer dependent on one seal maker for one old machine.