Consulting Support, Pre-Sale
Centrifuges are difficult to specify, because so
much is nearly unknowable to the average engineer. Quality resides in the
mechanical design, the bearings, the hard surfacing, and the process
efficiency. For the most part, all manufacturers have access to the same
components, so profit goes to he who builds the cheapest. And the technical
data the vendors release? It's typically is sales fluff.
I can take you through the centrifuge specifications, and tell you what they
really mean, and where the loop holes are that will
allow the manufacturer to walk away from the job, and leave you with little
recourse. A little of my time up front will save you and your client a pot of
money later on.
me tell you two stories:
Going to Sue the Bastards!
One municipal client was thoroughly dissatisfied
with the performance of their new centrifuges. The performance was no where near what was specified, and as a result the
operating costs were way out of line. The authority's lawyer hired me look
over the specifications and the start up testing
reports to see if they had a case to sue the equipment manufacturer. The
centrifuge performance did look particularly bad, considering the sludge they
had, and better optimization might well have improved the performance.
Unfortunately, the specification was flawed. It specified a sludge that the
plant could never produce. The centrifuge manufacturer evidently saw that
specification for the sludge was wrong, and was able to cut the startup
short, announcing in effect "what you see is what you get" because
the sludge would never meet the specification, thereby relieving the
manufacturer of their liability. My evaluation was; the centrifuge
manufacturer had a loop hole big enough to drive a truck through, and if
anyone was liable, it was the engineer.
this brand a maintenance hog?
One client, during a training class, asked me to
tabulate the differences between the two brands of centrifuges, one they had
operated for twenty years, and new ones made by a different manufacturer. One
very big difference quickly apparent was that the new centrifuges recommended
main and conveyor bearing changes every year. The existing centrifuges had
bearings that lasted 5-10 years or more.
"But the specification says the B10 life of those bearings is 100,000
hours!" said the boss. Well, yes it does, but the B10 bearing life
1 Assumes a vibration
level, a load, and a speed
2 Assumes no contamination
3 Assumes no lubrication failure
In short, it doesn't predict bearing life in the
real world, unless the vibration level and speed used in the calculation are
about the same as experienced over the life of the bearings.
have experts who can tell you the questions to ask, and can also check the
calculations the manufacturers submit.
When you write a
specification, it's hard to know what, exactly, you are going to get.
Municipalities have to give deference to low price. Different manufacturers
deliberately interpret the specification to suit their convenience. Then too,
they cry proprietary if you don't use their language, which guts the specification.
In the end, did they deliver a centrifuge that in fact meets the
specification? Mostly they do, but often some have been known to take the job
on low price, and argue later, if caught, oh we made a mistake. No one can
guarantee you won't be bamboozled (to use a charming phrase), but having an
expert on your side reduces the likelihood that it will happen
Post Sale Support
The job is in trouble, the contractor and vendors are finger
pointing, and blaming others, and all seem to have a point. I have been in
this position many times, and generally was able to work it out to
everybody's satisfaction. It's not uncommon for the technicians the
manufacturer sent out to genuinely ignorant of the base cause of the problem.
It's not so uncommon for the equipment to be improperly set up, and sometimes
the problem is in the design. It helps to have an expert on your side, to cut
through the acrimony, and find the problem, and show the way forward.