POWER PLANT REQUIREMENT.
STEAM MAKING EQUIPMENT -- USES OF PUMPS -- TYPES OF PUMPS -- PUMPS
FOR BRINE -- WATER SUPPLY -- PUMPS FOR WELLS -- WATER DISTRIBUTION
SYSTEMS -- PUMPS FOR BOILER FEEDING -- HEATING BOILER FEED WATER
-- WELLS -- COOLING TOWERS -- ECONOMIZERS -- SUPERHEATERS -- STEAM
ENGINES -- EXHAUST STEAM -- ADVICE AS TO EXHAUST STEAM -- BOILERS --
CONCLUSION.
=Steam Making Equipment.=--The quantity and type of boilers needed for
a plant is entirely dependent upon the quantity of steam required and
its economical or uneconomical use. The refrigerating and electric
producing apparatus in the average packing house are usually looked
upon as the chief using elements, but they each frequently require less
steam than is used for pumping purposes, and less than is used for
cooking and kindred operations. It would be well to discuss the uses of
steam and return to the boilers.
=Uses of Pumps.=--Pumps are used for water circulating, brine
circulating, boiler feeding and pumping products. These are named in
the order of their steam consuming demand as it usually occurs. They
consume from 40 to 120 pounds of steam per horse power hour based
on the kind of pump used and the skill in its operation. The most
economical are electrically operated centrifugal pumps provided the
current is economically generated, steam turbine centrifugal pumps,
next if in good condition, and reciprocating simplex or duplex pumps
third and fourth.
=Types of Pumps.=--The types chiefly used in packing house work are
simplex and duplex reciprocating, centrifugal single and multi-stage
operated by motor or steam turbine directly attached to the motive
power, also power pumps of triplex type and rotary or impeller pumps
for fats and oils. There are endless varieties of each type.
=Pumps for Brine.=--For brine pumping chiefly reciprocating and direct
connected horizontally set motor driven centrifugal pumps of one or
more stages are used. At times power operated triplex pumps are used
but the most satisfactory are the second named.
Pumping brine for refrigerating purposes is a never ending process
since it must be constantly performed. The common practice of an open
brine tank with submerged coils is being fast superseded by the use
of shell and tube type closed coolers which superseded double pipe
coolers. The use of either the latter two types enables the operator
to take advantage of hydraulic head by installing a balanced system
described in this work which very greatly reduces the power necessary
to exert to pump brine. The friction in an eight to twelve pass brine
cooler is from ten to fifteen pounds, and this with the pipe friction
on a balanced system will total to perhaps thirty pounds on large
systems, but less than the ordinary open system--depending upon the
building height.
=Water Supply.=--The water demand for packing house operation is quite
an important element in relation to steam consumption. The quantity
required for ammonia condensing, steam condensing (if done), and for
plant purposes, washing, etc., is, in the aggregate, quite a large
amount. For example: For ammonia condensing, from 1¹⁄₄ to 1¹⁄₂ gallons
per minute is required per ton of refrigeration developed; for steam
condensing for steam engine from 32 to 40 pounds per pound of steam
condensed; for boiler operation about four gallons per horse power per
hour; for plant purposes from 250 to 3,000 gallons or more per hour,
depending upon the size of plant and its intelligent use. It will be
readily seen that those quantities will mount in power consumption if
the head or pressure pumped against is high.
=Pumps for Wells.=--Water pumped from wells is usually pumped by one of
four methods:
(1) Suction type reciprocating pumps.
(2) Deep well heads with low set pumping barrel.
(3) Submerged centrifugal pumps.
(4) Compressed air.
For small plants where one or two wells will supply the water, the
first named pump is usually used owing to cheapness of cost for
installing and particularly if the water rises in the well to a height
reachable by a suction type pump, viz: 23 to 25 feet. Power operated
suction pumps are also available for this service. If the water be too
low for the above named type to handle, deep well pumps with steam head
serve pretty well and usually cost less than air pumped wells.
For larger plants, larger wells are installed and submerged centrifugal
pumps or compressed air is used, the latter always as a last resort
from a cost of pumping standpoint, although its simplicity and
reliability appeals to many.
Submerged centrifugal pumps can be operated with steam turbine or motor
set on top of shaft above ground. The motor operated set is the more
economical, particularly if the current be generated at low cost.
=Water Distribution Systems.=--The intelligent laying out of water
systems and the pressure pumped against is a factor worth great
attention. It is far better to have pumps of proper proportions for the
service intended, even though it involves the use of a separated piping
system.
Taking advantage of water once raised to a high level in its return to
service is a power saving. For example: It is usual to locate ammonia
condensers at a point where there is a good circulation of air. This
is done to permit the winds to carry away the moist air from about the
condensers, together with the heat delivered up through it and to the
air by the discharged gas from the ammonia compressors. From the catch
pan beneath the ammonia condenser the water can be diverted through
the steam condenser and if the shell be bought sufficiently strong
in the case of a closed condenser, the water can be delivered to the
suction side of a pump which in turn will deliver it for house use for
cleansing purposes. If a barometric condenser is used, the water is
delivered to a hot well from whence it can be pumped or flow to sewer.
=Pumps For Boiler Feeding.=--Dependent upon the size of plant and the
pressure carried pumps are usually provided as follows:
Small boiler plant up to 500 H. P. low pressures. Steam 80 to 125
lbs. simplex or duplex piston packed reciprocating pumps.
Medium Boiler Plant up to 1,000 to 1,500 H. P. steam 125 to 150
pounds simplex or duplex outside piston packed reciprocating pumps.
Over 1,500 H. P. the same or centrifugal type multi-stage pump motor
or steam driven.
=Heating Boiler Feed Water.=--Every plant, large or small, should be
equipped with boiler water heating devices. These are so common and the
practice so usual that it is scarcely necessary to mention it but the
writer has seen plants where the exhaust steam from pumps and engines
was being thrown to the air and feed water pumped into boilers at low
temperatures. There are two types: closed and open. In the first named
the water is circulated through tubes enclosed in a vessel, the tubes
surrounded by steam. In the open type the steam is brought in direct
contact with the water and performs the heating in this manner. The
closed types are used on the principle that no oil carried in the steam
is passed to the boilers, but the latter type are usually equipped with
an oil separator that eliminates the oil and prevents danger from this
source.
=Wells.=--In most instances wells of various depths from 80 to 2,000
feet will find water. A few localities, however, do not yield water via
wells and this is a poor situation from a packing house standpoint.
The water from surface or shallow wells is, at times, improper for use
on meats owing to contamination, in which case, resort must be made
to other sources. In some localities the neighboring streams yield
suitable waters but in this case sewage contamination must be guarded
against. The quality of boiler supply water is an important factor in
the boiler operation in its bearing to shutdowns for cleaning, blowing
down, repairs, etc., all of which contribute to or impair economy.
=Cooling Towers.=--Where it is necessary to husband water for
condensing ammonia or steam the use of cooling towers comes into play.
These function by the cooling of water by evaporation, the evaporation
abstracting the heat. There are various kinds--sprays over ponds, water
dripping over spatter boards made in various ways, such as brush piled
loosely; a checker work of wood slats; screen wire, etc. These usually
depend upon the circulation of air in a natural way. There are various
patented types, depending upon fans, to pass air through falling water.
The efficiency is dependent upon the fineness of the water and the
quantity of air passing through it, the relative humidity of the air
controlling greatly the cooling effect.
=Economizers.=--Where the utmost economy of fuel is striven for and on
larger plants, these are installed. An economizer is a bank of cast
iron flues placed in a position between the boilers and the smoke
stack. Water is circulated through the tubes and the furnace gases
pass about them. They are usually calculated upon to decrease the
stack temperatures from 100 to 150 degrees--dependent upon its initial
temperature and to heat the feed water one hundred degrees. This is a
saving from a wasted source, since it is impossible to take up this
heat in any boiler yet designed.
=Superheaters.=--In an earlier chapter reference was made to
superheated steam. The office of this apparatus is to heat the steam to
a higher point than it rises to, under ordinary boiler conditions. For
instance, steam as delivered from the nozzle of a boiler is spoken of
as “saturated” steam, but, if before use this is subjected to a further
heating before it is used, it is said to be “superheated.”
Superheaters are of two types. They can be described as follows: A bank
of coils located in the flame pass in the boilers, the steam within the
coils and the flame on the outside; or a bank of coils in a separate
furnace, the flame or heat generated in the furnace passing over the
coils.
Steam superheated beyond 450° F. total sensible temperature requires
especial pipe fittings, type of valves, and engines for reasonable safe
operation, and renders an economy that a small plant cannot afford, due
to the expenditure, to take advantage of.
=Steam Engines.=--Owing to the cheapness of fuel in the United States,
users have been satisfied with equipment at a low initial cost and in
consequence pay bills continually by using uneconomical prime movers,
viz.: ordinary steam engines of the simple Corliss type, using from 26
lbs. to 35 lbs. of steam per horsepower hour, or compound condensing at
15 lbs. to 18 lbs. of steam per horsepower hour or high speed direct
connected slide valve engine generator sets using from 35 to 50 lbs.
steam per horsepower, depending upon load.
European engineers, where fuel costs are double and triple American
fuel costs, have of necessity paid more attention to the subject of
steam economy and have outstripped this country in design and use of
economical steam engines, notably of the so-called “uniflow,” “drop
valve,” “poppet valve,” or “Lentz” type and with the use of superheated
steam, have reached much higher efficiencies. The fast increasing costs
of fuel in this country have necessitated American builders resorting
to high steam pressures with independent or integral superheaters in
conjunction with steam boilers, and as a result American manufacturers
are offering simple uniflow engines for high speed (say 200 r. p. m.)
direct connection to electric generators. Also compound drop valve or
poppet valve or Lentz types for slowly moving engines, viz.: 60 r. p.
m. for connecting to ammonia compressors and in either case with steam
at an initial pressure of 160 lbs. and ordinary superheat of 100°
operating condensing, engines of the above types under the conditions
named can be readily bought under guarantees to produce an indicated
horsepower with the use of 12 lbs. of steam per horsepower hour.
The uniflow engine is now offered by several builders and is adaptable
to most any service, atmospheric exhaust, condensing or against a back
pressure using the exhaust for cooking or heating. There is but little
advantage, however, in a uniflow engine under this circumstance unless
it be the flexibility as to conditions of operation.
=Exhaust Steam.=--The practice of using exhaust steam, that is steam
which has passed through engines, for heating and cooking is considered
economical. It is based upon the theory that the quantity of heat
contained in a pound of steam that has been reduced in pressure from
its initial or high pressure, say 100, to a low one--example 5 lbs.,
and then used for heating, etc., contains almost as many heat units as
it did originally.
There are many places where this low pressure or exhaust steam can be
used advantageously, but if extensively used, the likelihood will be
to have long mains into which certain equipment will pass its exhaust
and from which the demand will be spasmodic for cooking purposes and
intermittent for heating, except during winter seasons, and as a result
there is a considerable quantity of steam passed to the air at most
times.
A careful analysis is necessary for intelligent use of this idea,
since the maintaining of a balance owing to business fluctuations and
changing seasons makes an almost unmatchable combination. During one
season live steam will be used for make up, and at other times there is
a surplus.
=Advice As To Exhaust Steam.=--Aside from heating feed water and drying
where the requirement is constant, a better practice is probably to
limit the extent of exhaust steam systems and use live steam for most
purposes.
The sources of exhaust steam, engines or pumps, are operating usually
twenty-four hours daily and constantly pouring steam into the exhaust
mains, which is constantly radiating, leaking and the accumulated
moisture is being trapped away to a sewer or feed water heater. The
traps are usually just a little out of order, and the little leaks in
multiple mount up fast.
Again the apparatus in almost any department used for cooking and
manufacturing is irregular in its use and an actual record will show
hardly to exceed six hours’ demand or use. Why operate engines and
pumps at a disadvantage all the time for the sake of a supply six or
eight hours daily? The engine and pump requirement increases rapidly
with the exhaust steam pressure and requires larger production from the
boiler.
Any power like that needed for pumping can be transmitted on a wire
with far less loss than as steam through a pipe.
The recommendations then are: Produce electricity as cheaply as
possible; if electricity is made, use high class equipment operating
condensing and take advantage of superheat if possible; produce
refrigeration or compress air with the same intelligence; perform all
pumping with electrically operated pumps; distribute steam for all uses
at high pressure, at high velocity through small pipes, well insulated
and have the heat at the process when needed; fit boilers so they
can arise to a demand when needed with ample stack and draft; install
stokers, if the plant will justify it; insulate the boiler walls and
generate steam as cheaply as possible--and don’t waste it.
=Boilers.=--The common types of boilers in the United States are the
fire tube boiler and the water tube boiler. The first named kind is
that which suggests itself to the reader when a boiler is mentioned
and consists of a shell cylindrical in form with a head in each end
into which tubes are expanded. In operation the water surrounds the
tubes and the fire passes through them. The water tube boiler is the
opposite of this. There are variations of these and boilers that are
built using both principles in part. There are also Cornish, Lancashire
and Yorkshire types used in England which are fire tubes using only
one or two tubes. Where a plant requirement is up to 500 horsepower,
the fire tube is the usual installation owing to its cheaper cost, and
more units which enables more continuous operation, especially if a
unit is out of service for cleaning, 100, 125 or 150 horse-power being
the standard size units. If a plant requires 750 horse-power or more,
installation of the water tube is preferable owing to their requiring
less floor space, higher pressures are usually carried and they are
regarded as more safe under these conditions. They can be forced to
a higher output if demanded, which is an advantage in times of rush
business.
=Conclusion.=--The mounting costs of fuel prompts the writer to say
that the management of a power plant of any packing house demands
intelligence in the selection of equipment and in its operation.
The losses that occur are silently passing on perpetually and are
immeasurable to the proprietor since they are intangible in dollars and
cents. In these days of educated engineers, a mixture of education and
common sense is obtainable and it takes this training or the practical
man who has augmented his practice with ability to use a pencil to
figure out his conditions, and suggest remedies that will stop a leak
of no inconsiderable consequence. It is a usually neglected department
by the proprietary interests.