Fighting Energy Losses & Maintenance Costs

Publication Date01 May 1982
DOIhttps://doi.org/10.1108/eb057256
Pages22-22
SubjectEconomics,Information & knowledge management,Management science & operations
Fighting Energy Losses & Maintenance Costs
In a climate of intense economic pressure, more and more
companies are examining ways of conserving energy and
reducing maintenance costs. Apart from insulation
methods and materials one of the critical areas being
studied is heat and service medium losses through leaking
valve glands. In process industries for example, the cost of
lost heat and service mediums can not only be enormous
but failure to rectify the problem could incur further finan-
cial penalties through damage to buildings, fittings etc, in
addition to creating a possible danger to operating staff
and pollution of the atmosphere.
The cost problem was highlighted recently by valve
manufacturers Hattersley Heaton Ltd. In their Research
and Development Department a series of tests were carried
out which clearly show how wasteful a leaking conven-
tionally glanded valve can be.
A steam entrapment device was designed whereby an in-
duced leakage of saturated steam at 150 lbf/in2 was allow-
ed to escape from known stem/gland clearances of
0.001in, 0.0015in and 0.002in. The escaping steam was
then condensed and the water measured over a period of
time.
The result was that even the smallest clearance
resulted in losses of
11.1
litres or 24.51b of steam per hour.
The 0.0015in clearance produced losses of 26.7 litres or
58.8 lb of steam per hour, and the 0.002in leakage path
rate was a staggering 32.4 litres per hour or 71.3lb of steam
an hour. Working on a minimal cost of £2.50 per
1,000lb
of steam it was revealed that the cost of a 0.002in leakage
was £30 a week, £120 per month and an enormous £1,440 a
year from one valve alone!
The cost of a 0.002in leakage of
escaping steam from the gland of a
valve can well be £1,440 a year!
Hattersley Heaton have been aware of this growing pro-
blem for a number of
years.
As early as 1956 the company
developed a bellows sealed valve to meet the stringent re-
quirements of the nuclear power industry where the
prevention of gland leakage to atmosphere is critical. Since
then the valve has been installed in nuclear power plants all
over the world.
Basically the HH Bellows Sealed valve
is
a simple gate or
globe valve with a flexible metallic bellows replacing the
conventional, often troublesome, gland packing. The
bellows is seal welded at its top end to the bonnet assembly
and its bottom end to the stem. This prevents the fluid
escaping between the steam and bonnet, and as the other
valve joints are seal welded the whole valve assembly is
completely leak tight to atmosphere. In addition, the back
seat of the valve is fully protected from the line fluid by the
bellows and by the steam baffle which prevents moisture or
foreign matter entering the bellows chamber, maintaining
it in a new condition and providing a consistently high
standard of sealing in an emergency.
With its unique construction the HNH Bellows Sealed
valve creates cost savings in other areas too, in reducing
maintenance costs for example. The valve seatings are hard
faced and the operating gear contains thrust bearings to
reduce maintenance. Under normal circumstances the
valve should only need occasional lubrication of the
operating gear to keep it in perfect condition.
Although it was originally designed for nuclear applica-
tions,
many oil and petro-chemical companies were quick
to appreciate its cost saving characteristics and today many
thousands of these valves are installed in refineries and on
critical process lines in the chemical industry.
Now, with energy costs still rising, design engineers are
seriously evaluating this type of valve for application in
commercial heating systems. Although its initial cost is
higher than for conventional valves, some design engineers
are already convinced that energy conservation plus reduc-
ed maintance costs will make the bellows sealed valve cost
effective in the long term.
22 INDUSTRIAL MANAGEMENT + DATA SYSTEMS

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