John Crane's original patented mechanical seal type still in service after 40 years
Through an unrelated problem, plant operators in the Kenosha Water Utility have ended a 40-year run for one of John Crane's first patented mechanical seals - a service that endured eight US presidents, 20 summer and winter Olympic Games, and an estimated two billion gallons of treated water.
Morton Grove, IL , July 30, 2003 -- It is April 1963. John F. Kennedy is president and Jack Nicklaus has just won the 27th Masters Golf Championship. In Kenosha, Wis. on Lake Michigan, engineers at the Kenosha Water Utility have just installed two Delaval Type 100 M vertical pumps fitted with John Crane Type 1 mechanical seals on the facility's north and south backwash pumps.
Fast forward to April 2003. Plant operators in the Kenosha Water Utility discover a leak in the north backwash pump caused by a clogged flush line -- ending a 40-year lifespan of John Crane's first patented mechanical seal - a service that endured eight US presidents, 20 summer and winter Olympic Games, and an estimated two billion gallons of treated water.
What is even more remarkable is that plant personnel inspected the sister seals on the south backwash pump, also installed in 1963, and found them to be in good condition -- 40 years on the job and still running as it did when first installed. Even though longevity has always been a hallmark of John Crane's mechanical seals, 40 years of service is an aberration.
"I knew the seals hadn't been changed during my 15 years at the plant, but I assumed that the seals had been replaced sometime during their 40 year life," said David Lewis, Kenosha's Water Production Superintendent.
However, a follow-up with previous superintendents and John Crane personnel confirmed that the seals were indeed the original equipment -- Type 1 mechanical seals three-inches in diameter with flexible rubber bellows, lapped carbon seal face and ni-resist mating ring. Their retainer, disc, drive band, spring and spring holder were all constructed of brass, and during operating conditions, the seals ran in clean water at ambient temperature at 1,175 rpm. The seals had been installed on vertical pumps used to pull water from the Kenosha plant's finished water clearwell and pump it into a 250,000-gallon backwash tank while supplying pressure to assist in backwashing the plant's sand filters.
During the systematic analysis of the application and diagnosis of the failure, John Crane engineers and Kenosha plant operators discovered that the north pump's flush line had stopped working. Minerals from the water of Lake Michigan had built-up over the years, causing a blockage in the line. Without the water from the flush line to cool the seal, the rubber bellows, carbon seal face and ni-resist mating ring became overheated. The result was melting and disintegration of the rubber bellows portion of the seal and astonishing proof that the malfunction of the flush line caused the Type 1 seal's failure, not the seal itself. Further, an inspection showed the original Type 1 seal on south backwash pump to be in good condition.
According to Mike Kraus, John Crane Market Development Manager, typical life expectancy for a mechanical seal of this type balances a variety of factors, including the operating conditions and environment, though three to five years is a reasonable industry estimate. However, Kraus said he knows of seals that ran for over 20 years and does not believe the seals found at Kenosha Water Utility are an isolated case.
"The superb condition of the seal faces and other critical components indicate that this seal would still be in service today if the flush line would not have become clogged," said Kraus.
Gary Woodward, a technical trainer for the John Crane Academy, inspected the seal and concurs with Kraus.
"Although there was obvious wear and some corrosion around the seal faces," said Woodward, "this is expected with 40 years of service in water. What is even more amazing though is that the seal found on the south backwash pump is likely to last for years to come based on the condition of the seal faces."
The flush line on the south backwash pump has been replaced to prevent a similar incident from occurring in the future and a new Type 1 seal has been installed on the north backwash pump. Interestingly, with the exception of using stainless steel components instead of brass, the new and old seals are virtually the same, validating the effectiveness of the original design.
Mechanical seals serve the basic yet important function of preventing leakage by closing a gap or making a joint between two surfaces that have relative motion. In a pump, the shaft moves in relation to the housing unit, requiring a device such as a mechanical seal to dynamically fill the void between those two surfaces. In order to prevent any liquid leakage under demanding conditions, the dynamic sealing interface of a new seal is lapped flat within millionths of an inch.
The Kenosha Water Utility's maintenance division also uses John Crane mechanical seals in the wastewater facility. According to Lewis, Kenosha will use additional John Crane products in the future.
"Based on my experience working with John Crane and seeing this kind of performance," said Lewis, "they (John Crane) will be the first vendor I contact in the future when I need replacement seals for any of our applications."
About Kenosha Water Utility The Kenosha Water Utility provides water and wastewater service to more than 100,000 persons in the greater Kenosha, Wis. metropolitan area, including the City of Kenosha, Village of Pleasant Prairie, Towns of Somers and Bristol. The Kenosha Water Utility also provides a monthly Household Hazardous Waste Collection Service for City of Kenosha residents.
The Kenosha Water Utility is a municipally-owned, fiscal independent public utility organized under authority of 66.068 of the Wisconsin State Statutes and Chapter XXXII of the City of Kenosha City Ordinances. It is solely financed by water and sewer service charges.
About John Crane
A member of the Smiths Group plc, John Crane (www.johncrane.com) is the acknowledged technology leader and the world's largest manufacturer of mechanical seals and associated products. With a workforce of more than 6,000 people in 47 countries, John Crane provides an unrivalled global presence combined with personalized local service and support.
John Crane offers a comprehensive range of engineered mechanical seals and sealing support systems, mechanical packing, power transmission couplings and centralized lubrication systems under the brand names John Crane, Sealol, Safematic, Flexibox, Metastream, Powerstream, and Lemco. These products are sold widely into rotating equipment applications in petroleum, chemical, pharmaceutical, pulp and paper, power generation, food and beverage, mining and minerals, transportation, industrial, water and waste, refrigeration, automotive, as well as appliance markets.