COVER STORY 2

CUSTOMER SOLUTIONS 4

INNOVATIONS 5

INSIGHT 6

Flow Solutions DivisionBW Seals

Durametallic SealsPacific Wietz Seals

Pac-Seal

Flow Solutions DivisionBW Seals

Durametallic SealsPacific Wietz Seals

Pac-Seal

T H E S E A L I N G T E C H N O L O G Y M A G A Z I N ET H E S E A L I N G T E C H N O L O G Y M A G A Z I N E

VOL. 13, NO. 3

Lasermachining

technologyimproves the

micromachiningof mechanical

seals

evolution

2 www.flowserve.com Face to Face

Flowserve leads the wayFlowserve leads the way

The Dallas, Texas-headquarteredFlowserve Corp. is pioneering newdimensions of micromachining formechanical seal faces through the

use of laser machining technology.“Although we manufacture several different

types of microfeatures for mechanical sealfaces, there were limitations on what we couldproduce. So, about three years ago, we set outto explore the use of laser technology,” explainsLionel Young, specialized technology managerat Flowserve’s Temecula, Calif. facility.

The company did considerable research onthe many types of laser technology available,then chose one closest to its needs. It thendesigned and built, in-house, a complete man-ufacturing system around the laser at 1/10ththe cost of an outside vendor to do the work.

“The laser technology allows us to do a num-ber of things we could not do before,” saysYoung. “For instance, we can now produce veryuniform patterns. A laser pattern is repeatable,so any number of repetitions is exactly thesame.” The laser significantly improves surfacefinish, is capable of making novel patterns, andis not limited to the kinds of microfeatures thatcould be made before. “Finally, the timeneeded to move from pattern concept to pro-totype is much shorter,” Young says. “Before,this process could take weeks. But now with in-house developed computer code, we can makenew patterns within minutes.” The variety oflaser-machined faces includes T-Groove, APGS,GSL /GTS/GSS with OD waves, SLM 6200 withID waves,and GSG with HST features.

The real worldTo turn to some case histories, consider first aCanadian Pipeline application in which bothcrude oil and NGL run in batch mode.“Normally you design a seal for one service orthe other,” says Young. “It’s very difficult tohave the same seal work for crude and a light

hydrocarbon, such as NGL.”“This is a particularly harsh environment for a

mechanical seal, explains Young. “The crude oilhas abrasive properties; there are frequent startsand stops (well over 200 to date); and there iswide pressure variation, from 100 to 1,400 psi.”

This application depends on the FlowserveHDHW 4500 seal, with a GSL 4437 backup,and uses silicon carbide against silicon carbidewith waves on the primary face. Young saysthat conventional seals performed poorly. Butthis laser variation, when last checked inAugust, had lasted two years without a prob-lem. At year end, 12 seals were in operation inCanada, and 18 in the U.S.

In another Canadian Pipeline application,which runs a crude oil/ethane batch, the sealsendure abrasive conditions and pressures rang-ing from 400 to 1,000 psi. A special problem is thespecific gravity, which has a wide range from 0.85to 0.44. “Ethane is hard to seal because it tends togo into a gaseous form between the faces,” says

Young. When that happens, the pumped fluid nolonger provides lubricity. The Flowserve HDHW5500, with a GSL 5250 backup, also features sili-con carbide against silicon carbide, with lasermachined waves on the stationary face. Four suchseals are in operation at four stations. “They’vejust pulled one set of seals out after more than5,000 hours of operation, and the faces are in

Flowserve Corp. is pioneering new dimensions ofmicromachining for mechanical seal faces.

Face to Face www.flowserve.com 3

evolution

excellent condition,” Young reports.

Multiphase sealsYoung describes a multiphase application inVenezuela, which pumps crude oil directlyfrom the ground, as an extremely tough oper-ation. The crude oil contains gas, water andsand, which makes it hard to pump and hardto seal. “Previously we had not been able tobuild seals for this application,” says Young.

The process temperature on this twin screwpump, 90 to 125˚ F (32 to 52˚ C) is not thatbad, and uses a low shaft speed of 900 rpm.The problem is the pressure; not so much the90 psi steady-state pressure, but rather the 750psi at start-up. “This is a big problem becausethe crude is so viscous,” says Young. Again, thewavy seal faces from the laser machining oper-ation solved the problem. The first seals wereinstalled in December, 2001, and are still oper-ating. “Our competitors are still having diffi-culty putting seals on similar work,” says Young.

BoilersFlowserve also has designed and tested seals forboiler circulation and boiler feed applicationsin power plants. “In boiler circulation applica-tion, the difficulty is the high pressure, 2,800 psi,and because the fluid is water, it’s a tough serv-ice,” says Young. “What most vendors try to dois put carbon against silicon carbide. What we’vedone is run silicon carbide against silicon car-bide, with the addition of wavy face technology.This seal is a Tandem DHTW 4250. Ordinarily,running silicon carbide against silicon carbidetears up faces rather quickly under these condi-tions. With wavy hydrodynamic features, oursrun so the faces don’t touch—which means theycan run for a very long time.”

The boiler feed application is difficultbecause it requires good performance at mod-erately high pressures (600 psi) but highspeeds (5,000 to 6,000 rpm) and temperaturespotentially greater than 400˚ F. The proposedseal was a DHTW 6750, (again with wavy SiCagainst SiC). Test results showed successfuloperation at pressures to 585 psi, water tem-perature to 400˚ F and speeds to 5,555 rpm.

GearboxesNew at Flowserve is its GSG seal (patent pend-ing), a non-contacting zero-leakage gearbox sealfor integrally geared API pumps and compres-sors. “API pumps and compressors equippedwith integral gearboxes, have had variousdegrees of success when it came to performanceof gearbox seals,” says Young. “One problem isthat the carbon face can develop blisters result-ing in oil leakage.”

Studies done in the Temecula test facility and

verified through research at University ofWestern Michigan have shown that blistering isthe result of sudden starts in an oil environment.Under usual conditions, when a carbon faceruns against a tungsten carbide face, oil impreg-nates itself into the carbon. As the faces rotatesays Young, “the shear of the oil develops enor-mous forces that cause carbon blistering.Themore viscous the oil, the more severe the blister-

ing. The GSG gearbox seal features a silicon car-bide stationary face that incorporates lasermachined HST features (Hydrodynamic SurfaceTension) and a tungsten carbide rotating face.

Another Flowserve innovation is Hydro-dynamic Surface Tension Technology. “It’s thecombination of two principles,” Young says.“One involves the use of wave technology to cre-ate non-contacting face operation, and the otheris a series of concentric face grooves that takeadvantage of surface tension principles to elimi-nate leakage. The grooves cause gas to separatefrom the oil and form liquid bands at the landregions between grooves. Surface tension allowseach band of liquid to support a pressure drop.The amount of pressure drop is a function of thefluid type and film thickness. For oil in this appli-cation, a proprietary computer code has calcu-lated the pressure drop capability to beapproximately three psi per liquid band. Whenthe seal is in static mode, leakage is eliminatedbecause of intimate contact of the faces.”

“When we run the laser machined HST faceagainst the tungsten carbide, the faces don’ttouch,” says Young. “In conventional terms, hav-ing seal faces not touch with zero leakage is anoxymoron. If they don’t touch, there is no seal-ing and you have leakage. What we have now is anon-contacting seal with zero leakage and itwould not have been possible without the adventof laser micromachining.” The GSG was tested atspeeds ranging from 8,000 to 40,000 rpm for aslong as 1,700 hours with no measurable wearand no measurable oil leakage. Almost 200 GSGseals have been installed since its introduction.

“Laser machining is a growing part of ourbusiness and we are exploring the use of HSTtechnology as well as other unique face micro-features in various applications,” says Young. ●

Laser technology has helped Flowserve develop anumber of new seals.

4 www.flowserve.com Face to Face

customer solutions

From extreme job securityto extreme reliabilityYou see, seals are the key to moving crude oil

Sinclair Pipeline is the business unit thattransports crude oil its parent companypurchases. The flow suffers frictionallosses during every inch of its travel

through the long pipelines moving it to thecompany’s refineries. Spaced every 80 to 100miles, pumping stations boost pressure tokeep the black gold flowing.

In each station, multi-stage, high-pressurepumps boost pressure as high as 2,000 psibefore returning it to the eight- or ten-inchpipelines. Pressure in the pump’s two sealchambers regularly runs 500 to 1,000 psi.

The person behind the pumpsAlan Dean, Sinclair’s mastermechanic, keeps theoil moving. In 1990,he was in charge ofmaintenance forfive pumping sta-tions in Wyoming.

“We were averag-ing between fourdays and two weeks ofseal life,” reports Dean.Each seal failure shut thepipeline down from four toeight hours. “If both seals wentout, I was looking at a 10- to 12-hour day,” he adds.

Dean had job security, but hiswas a life of long hours behind thewheel. As soon as one station was up andrunning, a seal three hours away would fail. Offhe would go. Drive and repair, drive andrepair. For years, his was a never-ending, full-time job that kept him away from home toomany weekends.

The causeDean realized the root cause was grit. Severalpumps originally had been used for diesel fueland gasoline, both very clean liquids. Now, thereliability was not stellar. The OEM seals for lighthydrocarbons can’t handle the harsher crude.

At each station, Dean kept component partsfor rebuilding seal cartridges. After a repair, hesent the failed components to be refaced. Dean

also experimented with combinations of facematerials, ever searching for the Holy Grail.

Then Dean met Howard McDonald,Flowserve’s representative covering the territoryin which Sinclair operated. McDonald sug-gested using a Flowserve UC seal, a canned sealfeaturing an encapsulated graphite gasketed sil-icon carbide rotating face against a tungsten car-bide stationary face. It’s designed, McDonaldexplained, to minimize the probability of hang-up from packed solids. It’s rated at 1,000 psi andcan be modified to handle 1,500 psi.

Field testingMcDonald offered Dean a pair of seals to test.He also offered a six-month warrantee, pro-

vided that Sinclair could guaranteethat certain process conditions

would always be met andthat Dean used only fac-tory-assembled seal car-tridges. “That’s betterfor me,” says Dean,who arranged formanagement approvalto test the seals on that

lone pump.The seals shipped

in mid-winter toSinclair’s Station I in

Casper, Wyo. Assisted byTom Rice from Flowserve’s

facility in Oklahoma, McDonaldand Dean started installing the seals.

In mid-process, an adjacent pump started leak-ing. With the performance test not evenbegun, Dean asked McDonald to provide aseal set for his newest leaker. Four days later,the second set was delivered and installed.

Within six months, another pump in Caspersuffered four seal failures. That’s whenSinclair management said “Go” and startedusing Flowserve UC seals. “We’re getting oneand one half to two years life from the newhigh-pressure seals,” says Dean. “As of now,every crude unit we have has Flowserve sealson it.” Incidentally, the original set of UC sealsSinclair installed to verify the performance arestill in operation, five years later. ●

Face to Face www.flowserve.com 5

innovations

Presenting...Flowserve’s Circpac MD and Circpac HP seals

The Circpac family of dry runningseals are segmented circumferentialseals designed for low gas consump-tion using pressure balanced rings

and hydrodynamic surface features. Standarddesigns consistently outperform packing,bushings, labyrinths, and similar seals over arange of operating conditions. Although theyshare the same basic seal technology, CircpacMD and Circpac HP seals compliment eachother to satisfy a diverse range of equipmenttypes and application conditions. The CircpacMD—Multiple Duty—runs in many types ofservices and combinations of conditions. TheCircpac HP—High Performance—runs at thehighest pressure and speed limits.

Features/benefits...Floating circumferential rings are engineeredfor long-term, reliable performance. Their?hydraulically balanced rings with hydrodynamicsurface features extend the maximum pressure,temperature and speed limits beyond conven-tional circumferential seal designs.

Robust carbon rings are designed withfoul-resistant joints and large bearing pads to

maintain integrity duringoff-design operation includ-ing oil-flooded conditions.

Materials of construc-tion are selected for appli-cation compatibility. Variousmaterial grades are availableto meet temperature and corro-sion resistance requirements.

Lower gas consumption allowssimplified gas control system.Circpac operating cost is lessthan typical circumferentialor labyrinth seals.

Control panel...An engineered control paneldistributes filtered buffer andbarrier gas with pressure con-trol and flow monitoring. Flow-serve offers standard configurationsthat provide reliable, economical sup-port for seals and will custom engineer panels tomeet customer specifications. ●

Contact Flowserve for extended conditions, alternatematerials or custom configurations.

Seal Circpac MD Circpac HP

Equipment Fans, blowers, dryers, turbines, Screw and centrifugal compressorscentrifuges, refiners, augers

Industries Petrochemical, waste water, Petrochemical, refining, pipelinepower, pharmaceutical, refining

Standard operating parameters...

Pressure Vacuum to 100 psi Vacuum to 150 psi

Temperature to 1,100˚ F to 350˚ F

Speed to 150 fps to 300 fps

Sizes 1.375 to 18.000 in. 1.000 to 11.000 in.

Materials of construction...

Ring Carbon graphite Carbon graphite

Housing Stainless steel or Ni Cr alloy Stainless steel, Ni Cr alloy,or NACE-compliant

Garter spring Ni Cr alloy Ni Cr alloy or NACE-compliant

Axial springs None Ni Cr alloy or NACE-compliant

Sleeve None Hard coated stainless steel,Ni Cr alloy or NACE-compliant

Gaskets Elastomer, fiber, graphite Elastomer, fiber, graphite

Configurations Single, double, triple Multiple custom variationswith modular ring units

Split housing Standard Optional

Leakage rates Estimated Guaranteed

Radial clearance As much as 0.25 in. 0.032 in.

Upgrade to… Circpac HP Gaspac (face seal)