Chapter XI: Part 11

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_b._ The rock shaft bearings must be bushed with bronze and the bushings pinned firmly in place. The length of each of these non-corrosive bearings must be not less than 4 inches.

_c._ Rock shaft cranks, valve rod heads, valve rod links, and piston rod spools or crossheads may be wrought iron or steel forgings, or steel castings. If of a heavy, strong pattern, these parts, with the exception of valve rod links, may be of semi-steel or cast iron.

_d._ The sectional area of all connections between rock shaft cranks and valve rod must be such as to give a tensile or compressive strength substantially equal to that of the valve rod.

17. VALVE MOTION LEVERS.

_a._ The valve motion levers must be steel, wrought iron, or steel castings. Cast iron is not acceptable. Steel castings, if used, must be deeply stamped with the name of the makers, with letters one-eighth inch high, near the upper end of each lever, where it can easily be seen,—thus “....._Steel Castings_.”

Cast-iron arms, if bulky enough to be safe against external blows,
are awkward in shape. The sectional area necessary for any arm
depends upon the means provided for preventing a sidewise strain on
the lever, due to rotation of piston or friction of its connection
to piston rod. The spool or crosshead on the piston rod should be so
designed that no sidewise strain can be thus produced on the lever.

_b._ The levers must have a double or bifurcated end at crosshead.

The double end is less likely than a single end to put an undue
strain on the lever as the rod turns, and is also likely to give
trouble from lack of lubrication or from a loosening of any small
parts, and has proved to be the most satisfactory arrangement.

18. VALVE MOTION STAND.

_a._ The valve motion stand must be securely dowel-pinned to the yoke castings, to prevent any movement after being once adjusted.

19. CUSHION VALVES.

_a._ Cushion-release valves regulating the amount of cushion steam retained at ends of stroke must be provided.

_b._ The cushion release must be through an independent port as shown in Figs. 2 and 3, so located as to positively retain a certain amount of cushion steam.

The old form of cushion release through bridge between ports is
not acceptable. This form while leading into the exhaust passage
as formerly, differs by starting from a small independent port
(about 1/2-inch wide × 2-1/2 inches long) through the cylinder wall,
located about 3/8 or 1/2 inch back from the cylinder head. (The
exact position for affording the best action has to be determined by
experiment with each different make of pump, as it depends somewhat
on the extent of clearance space and on the point of closure
of exhaust by piston and somewhat on the weight of reciprocating
parts.)

This style of cushion port makes the pump safer in case cushion valves are unskillfully left open too wide and tends to prevent a pump from pounding itself to pieces in case of a sudden release of load, as by a break in suction or delivery mains, or by a temporary admission of air to suction pipe.

Pumps made with this form of cushion release, have given very satisfactory results, and if the ports are properly located, there will be no re-bound of piston.

_c._ Cushion valves must be always provided with hand-wheels marked as per sketch, for the reason that very few men in charge of fire-pumps are found to clearly understand or to remember their use.

The lettering must be very open, clear and distinct, not liable to be obscured by grease and dirt, and of a permanent character.

It is desirable that spindle or wheel be so formed that a monkey
wrench can get a grip to open a jammed valve. Fig. 5 shows the stem
flattened for this purpose.

_d._ The valve and stem of cushion valve must be in one piece without any swivel joint.

Swivel joints are apt to come apart and make it impossible to operate
the valve.

20. PISTON RODS.

_a._ Piston rods for their entire length must be of solid Tobin Bronze, and the distinguishing brand of the manufacturers of this metal must be visible on at least one end of each rod.

_b._ The sizes must be not less than in table below.

_c._ The size and form of connection of rod to piston plunger and cross-head must be such that the stress in pounds per square inch at bottom of screw thread, or at such other point of reduced area as receives the highest tensile strain, shall not exceed 8,000 lbs. per square inch, when the steam pressure acting on the piston is 80 lbs. per square inch.

_d._ Piston rod nuts, in both steam and water ends, must be tightly fitted, and preferably of a finer thread than the United States Standard. This is to avoid as much as possible the unnecessary weakening of the rod at the bottom of the thread, and to reduce the tendency of the nut to work loose.

In practice 8 threads per inch has been found to give good
satisfaction.

_e._ In addition to a tightly fitting nut, some reliable device must be provided, in both steam and water ends, for absolutely preventing these nuts from working off.

Fig. 6 shows one form of such a locking device and illustrates the
kind of security desired.

This device combines the advantage of a taper key and a split pin,
and the elongated key-slot gives sufficient leeway to always insure
that the key can be driven up tight against the nut and thus prevent
it from even starting to work off. Other methods will be approved in
writing, if found satisfactory.

21. VALVE RODS.

_a._ Valve Rods for their entire length must be of solid Tobin Bronze, with sizes not less than in table below.

_b._ The net area of valve-rod at its smallest section subject to tensile stress, must not be smaller than at bottom of U. S. standard screw thread on rod of diameter given above.

The construction of this rod as affecting lost motion at slide valve
is specified under Article 15.

22. STUFFING BOXES.

_a._ All six stuffing boxes must be bushed at the bottom with a brass ring with suitable neck and flange, and the follower or gland must be either of solid brass, or be lined with a brass shell 3/16-inch thick, having a flange next the packing, as shown in the sketch.

The bottom of stuffing boxes and the end of glands should taper slightly towards the center as per sketch.

_b._ These glands should be strong enough to withstand considerable abuse, so as not to break from the unfair treatment of unskilled men.

23. PRESSURE GAUGE.

_a._ A pressure gauge of the Lane double tube spring pattern with 5 inch case must be provided and attached to the steam chest inside the throttle valve.

The dial of gauge should be scaled to indicate pressures up to 120 lbs. and be marked “STEAM.”

This kind of gauge is used on locomotives and is the best for
withstanding the vibration which causes fire-pump gauges to be often
unreliable. Moreover, this double spring is safer against freezing.

24. DRAIN COCKS.

_a._ Four brass drain cocks, each with lever handle and of one-half inch bore, are to be provided, and located one on each end of each steam cylinder.

Care should be taken to select a pattern of cock whose passageway is
the full equivalent of a 1/2-inch hole. Some patterns of 1/2-inch
commercial cocks although threaded for 1/2-inch pipe thread have but
a 1/4-inch hole through them. Such are not acceptable.

25. OILING DEVICES.

_a._ A one-pint hand oil pump, to be connected below the throttle, and a one-pint sight feed lubricator, to be connected above the throttle, must be furnished with each pump.

_b._ Oiling holes must be provided for all valve motion pins, and for each end of both rock shafts.

26. STROKE GAUGE.

_a._ A length-of-stroke-index must be provided for each side of pump. These must be of simple form for at all times rendering obvious the exact length of stroke which each piston is making, and thus calling attention to improper adjustments of cushion valves or stuffing boxes.

_b._ The gauge piece over which the index slides must have deep, conspicuous marks at ends of nominal stroke, and also light marks at extreme positions; it need contain no other graduations.

_c._ This stroke index must be rigidly secured to cross-head in such a way that it cannot get loose or out of adjustment.

THE WATER END.

27. WATER CYLINDERS.

_a._ These must be of hard close iron with metal so distributed as to ensure sound castings, and freedom from shrink cracks.

_b._ The design should be along lines best calculated to resist internal pressure so as to avoid as much as possible the need of ribs for stiffening.

_c._ They must be capable of withstanding, without showing signs of weakness, the pressures and shocks due to running under the conditions mentioned in Chapter “Tests for Acceptance,” Art. 48-54.

The suction chamber should be able to withstand a water pressure of 100 lbs.

Although suction chambers are not regularly subject to a pressure, it
is sometimes desired to connect them to public water supplies, and
where foot valves are used there is a chance of getting pressure on
the suction, so that ample strength is necessary.

Foundry finish may be permitted on the joints at water cylinder heads
and at hand-hole plates, provided surfaces are so true that a rubber
packing not over 1/16 of an inch in thickness is sufficient to secure
perfect tightness.

_d._ Conveniently placed hand-holes of liberal size must be provided for the ready examination and renewal of valve parts at the yoke end of water cylinders and in the delivery chamber.

This will necessitate holes not less than 6 × 8 inches, or its
equivalent, for the two largest-size pumps, and holes proportionately
as large for the 500 and 750-gallon pumps. The easy access to
the valve parts is of vital importance, and must receive careful
attention.

_e._ The thickness of metal for cylinder shell, valve decks, partitions, ribs, etc., will depend largely upon the form of construction, but, in a general way, to establish safe minimums for the average water cylinder, of nearly cylindrical form, whose flat surfaces are stiffly ribbed, we submit the table below:

=========================+==========+==========+============+============
=Size of Pump.= |=500 gal.=|=750 gal.=|=1,000 gal.=|=1,500 gal.=
-------------------------+----------+----------+------------+------------
Thickness of cylinder | Inches. | Inches. | Inches. | Inches.
shell when of nearly | | | |
cylindrical form | 7/8 | 1 | 1-1/8 | 1-1/4
| | | |
Thickness of valve decks | | | |
when well ribbed | 1-1/4 | 1-1/4 | 1-1/4 | 1-1/4
| | | |
| | | |
Thickness of transverse | 1-1/4 | 1-1/4 | 1-1/2 | 1-1/2
partition, depending | to | to | to | to
on ribbing | 1-1/2 | 1-1/2 | 2 | 2
| | | |
Thickness of longitudinal| 1-1/4 | 1-1/4 | 1-1/4 | 1-1/2
partition, depending on| to | to | to | to
ribbing | 1-1/2 | 1-1/2 | 2 | 2
| | | |
Thickness of ribs | 3/4 | 7/8 | 1 | 1
| | | |
Thickness of suction | | | |
chamber | 5/8 | 3/4 | 3/4 | 7/8
| | | |
Thickness of delivery | | | |
chamber | 7/8 | 1 | 1-1/8 | 1-1/4
| | | |
-------------------------+----------+----------+------------+-----------

Lighter construction than herein specified will not be regarded as satisfactory, and any construction will be finally passed upon on examination of drawings.

_f._ The bolting of all parts of the water end is to be of such strength that the maximum stress at bottom of screw thread will not exceed 10,000 lbs. per square inch (disregarding for the moment the initial stress due setting up nuts) for a water pressure of 200 lbs. per square inch, computed on an area out to centre line of bolts.

No stud or bolt smaller than 3/4-inch should be used to assemble parts subject to the strain of water pressure, as smaller bolts are likely to be twisted off.

Although these pumps are not expected to be designed for a regular
working water-pressure of 240 or 320 lbs., it is expected that bolts,
shells, rods, etc., will be figured to stand this comparatively
quiet, temporary, high pressure, exclusive of further allowance for
initial strain due setting up of bolts, with a factor of safety of at
least four.

This high test pressure is analogous to the custom of proving all
common cast-iron water pipes to 300 lbs. and all common lap-welded
steam pipes to 500 lbs. per square inch, and common water-works gate
valves to 400 lbs., even though these are to be regularly used at
much less pressure.

We are assured that castings no heavier than at present used by the best makers will stand this test, _if properly shaped and liberally bolted_.

_g._ For requirements for stuffing boxes, see Art. 22.

28. WATER PLUNGERS AND BUSHINGS.

_a._ The “inside plunger and bushing” is preferred for all situations where the water is free from grit or mud.

_b._ Water-plungers must be of solid brass or bronze, and the bushing in which they slide must also be of brass or bronze. The composition of the plunger and its bushing should be of very hard, though dissimilar alloys, to ensure good wearing qualities.

For material and size of piston rods and lock for nuts, see Art. 20.

With poor alignment or bad workmanship or lack of skill in mixing the
alloys, brass plungers are liable to score and give trouble; but with
proper selection of alloys and true cylinders accurately aligned,
they can be made to run all right wherever iron ones can. It is quite
a fine point to get these wearing surfaces just right; and _this
is wherein the experience, skill and shop practice of one maker is
likely to be much superior to that of another working under the same
specification_.

_c._ The length of machined cylindrical bearing within the partition must be not less then 2 inches. The plunger bushing must have a faced seat transverse to its axis against partition, forming a water-tight ground joint not less than one-half inch wide.

Any rubber gasket or other compressible packing for making this joint water-tight is not acceptable.

_d._ The construction of bushing and hole in partition must be such that a cylindrical shell for use with a packed piston can be interchangeably inserted in its place and secured by the same bolts.

This can readily be arranged and enables a packed piston to be
inserted in place of a plunger subsequent to the installation of the
pump with a minimum of expense, should this become desirable from
change of conditions at any future time.

_e._ Small transverse grooves cut within the sliding surface of the plunger bushing, with a view to lessen the leakage, are not acceptable.

Although a slight advantage in this respect for clean water, they are
a disadvantage on the whole, as dirt catches in them in the ordinary
situation and cuts the plungers.

29. STANDARD DIMENSIONS OF PLUNGERS AND PLUNGER BUSHINGS.

_a._ To bring all these expensive parts to the same standard of weight and bearing surface, the following dimensions are specified as the least that will be acceptable. These are based on a length of plunger which uncovers the bushings one inch at end of nominal stroke.

SOLID BRONZE PLUNGERS AND BUSHINGS.

===============+==============+==========+================+===========
=Size of Pump.=| =500 gal.= |=750 gal.=| =1000 gal.= |=1500 gal.=
---------------+--------------+----------+----------------+-----------
=Plunger.= | | | |
Diameter |7 or 7-1/4-in.| 9-in. |10 or 10-1/4-in.| 12-in.

Length | 17-in. | 17 „ | 18-in. | 24 „
Thickness of | | | |
transverse | | | |
partition | 5/8 „ | 5/8 „ | 3/4 „ | 3/4 „
Thickness | | | |
next to | | | |
partition | 1/2 „ | 1/2 „ | 5/8 „ | 3/4 „
Thickness | | | |
next to end| 5/16 „ | 3/8 „ | 3/8 „ | 1/2 „
Number | | | |
of ribs | 4 | 4 | 6 | 6
Thickness | | | |
of ribs | 5/16 „ | 5/16 „ | 3/8 „ | 3/8 „
| | | |
=Bushing.= | | | |
Length | 7 „ | 7 „ | 8 „ | 10 „
Thickness | | | |
at end | 5/16 „ | 3/8 „ | 3/8 „ | 1/2 „
Thence | | | |
tapered | | | |
evenly to | | | |
a thickness| | | |
next to | | | |
bearing of | | | |
not less | | | |
than | 1/2 „ | 5/8 „ | 5/8 „ | 3/4 „
Thickness at | | | |
the center| | | |
bearing | | | |
not less | | | |
than | 3/4 „ | 3/4 „ | 3/4 „ | 13/16 „
---------------+--------------+----------+----------------+-----------

30. WATER PISTONS AND BUSHINGS.

_a._ The “water piston with fibrous packing” is preferred for many situations in the West or South, or for water containing grit or mud, like that of the Ohio River; and, for the comparatively few cases where pump pressure governors are used, the packed piston will give better service and longer wear.

_b._ The removable bushing or cylinder in which this piston works must be of solid bronze.

_c._ As stated in Art. 28 _d_, this bushing should be so constructed as to be readily interchangeable with the bushing of the inside plunger type.

_d._ The length of bushing must be such that the ends of piston will barely come short of the edges of cylinder at contact stroke and not uncover.

_e._ The thickness of the cylindrical bushings must be not less than is given in the following table:

BUSHINGS FOR PACKED WATER PISTONS.

====================+========+=======+=======+========
=Size of Pump.= | =500= | =750= |=1000= | =1500=
| =gal.= | =gal.=|=gal.= | =gal.=
--------------------+--------+-------+-------+--------
=Solid Bronze.= | | | |
| | | |
Thickness at |7/16-in.|1/2-in.|1/2-in.|9/16-in.
extreme end | | | |
| | | |
Tapered evenly from |9/16 „ |5/8 „ |11/16 „|3/4 „
end to a thickness | | | |
next to bearing | | | |
of not less than | | | |
| | | |
Thickness at center |3/4 „ |3/4 „ | 3/4 „|13/16 „
bearing at least | | | |
--------------------+--------+-------+-------+--------

_f._ In other respects, the specifications for plunger bushings, already given in Art. 28, will apply to the above.

_g._ The water piston used in the shell described above must expose not less than 2 inches in width of fibrous packing, and must be of bronze, with disc and follower accurately turned to a sliding fit, so that the leakage past it will be a minimum, even when no fibrous packing is in place. There must be at least 2 inches in length of metallic bearing on both disc and follower.

The follower must be accurately centered and fitted to hub of piston, so that alignment will not be disturbed if taken apart.

_h._ The water piston must be of simple and strong construction, with follower bolts tightly fitted, and with fibrous packing so cut as to prevent by-passing.

_i._ All materials used in construction of piston, except packing, must be brass, bronze, or other non-corrosive metal.

_j._ Bushing studs must be of Tobin Bronze, and of such size and number, that the maximum stress at the bottom of the screw thread shall not exceed 10,000 lbs. per square inch, in the event of plunger becoming fast in the bushing with 80 lbs. of steam in the steam cylinders.

_k._ For each bushing stud there must be provided a composition nut and check nut.

_l._ All minor parts exposed to the action of water in water cylinder, that are not herein specified, must be of brass, bronze, or other non-corrosive material.

31. PUMP VALVES.

_a._ All the suction and discharge valves in any one pump must be of the same size and interchangeable.

_b._ There must be a clear space around each rubber valve, between it and the nearest valve, equal to at least one-fourth of the diameter of the valve, or between it and the wall of the chamber of at least one-eighth of the diameter of the valve.

_c._ These valves must be of the very best quality of rubber, of medium temper, with a face as soft as good wearing quality will permit.

They must be double-faced, so they can be reversed when one face is worn.

The quality of rubber is almost impossible of determination by brief
inspection or by chemical analysis. The relative amount of pure gum
and of cheaper composition may vary, or good material may be injured
by defective vulcanization. The only safe way to secure excellence
and uniformity is for the pump manufacturer to test samples of each
new lot under severe duty (as by a week’s run in a small special
pump, with say 150 pounds pressure and heavy water hammer, or by some
equivalent means) and to furthermore require the rubber manufacturer
to mould a date mark as “(Name of pump manufacturer, lot 201—April 3,
1904.)” on the edge of every valve, by which the pump manufacturer
can keep track of those which prove defective.

32. SIZE AND NUMBER OF PUMP VALVES.

_a._ The diameter of the disc of rubber forming the valve must not be greater than 4 inches or less than 3 inches. Three and a half inches diameter is probably the most favorable size, but is not insisted upon.

There is some confusion between different shops about designating
size of valves. The practice is here adopted, which is much the most
widely used, of naming the diameter of the disc of rubber which
covers the ports, and it is hereby specified that this shall be about
1/2-inch greater than the diameter of the valve-port circle which
it covers, thus affording about 1/4-inch overlap or bearing for the
rubber disc all around its edge.

If valves are larger than 4-inch there is an increased tendency to
valve-slam at the very high speed at which the pump is designed to
run, and if valves are smaller than 3 inches diameter the greater
number tends to unnecessary multiplication of parts, and the ports
being so small are a little more liable to become obstructed by
rubbish.

_b._ The thickness of the rubber valve must in no cases be less than 5/8-inch.

33. SUCTION VALVE AREA.

_a._ The total lift of suction valves must not exceed 1/2-inch.

_b._ The net suction valve port area and the total suction valve outlet area under valves lifted 1/2 inch high must not be smaller than the figures given in the table below.

By “valve-outlet area,” we mean the vertical cylindrical surface over
the outer edge of the valve ports, _i. e._, the distance L multiplied
by the circumference at the outer edge of the valve ports _C_, Fig.
8. Thus for a 4-inch valve, with ports inscribed in a 3-1/2-inch
circle, whose circumference is 3·5 × 3·1416 = 11 inches; the valve
“outlet area” for 1/2-inch lift would be 5-1/2 inches.

The actual velocity of piston during the middle portion of stroke is
from 2.0 to 2.4 (average 2.2) times as great as the piston travel per
minute (as determined in experiments by Mr. J. R. Freeman on several
duplex pumps of different manufacture). This is because each piston
stands still nearly half the time, or while its mate is working,
and, moreover, moves more slowly near start and finish of stroke.
The words “piston speed” are commonly incorrectly used and refer to
“piston travel.” A clear understanding that the actual piston speed
is _more than twice as great_ leads to more generous valve design.

Large aggregate valve areas are necessary for pumps designed to run
as fast as these, and experience has shown that to prevent valve slam
at high speed and to accommodate high suction lifts, it is just as
important to have a large “valve outlet area” as to have a large area
of valve port.

It is valve slam or water hammer which commonly limits the highest
speed at which a pump can be run. This water hammer may originate
from the pulsations in a long or small suction pipe. The vacuum
chamber lessens it, but there is commonly some point of high water in
the vacuum chamber that will give much smoother action than any other.

Valve slam in this style of pump is caused chiefly by the short
rebound of the steam piston against the elastic steam cushion at the
end of the stroke. This in turn snaps the valves down with a jump
when the speed is high. Dividing this impact or slam on numerous
valves of low lift, tends to break up and lessen the shock, therefore
with valves of the size and style used in fire-pumps, other things
being equal, the less they have to rise and drop to let the water
through them, the less will be the valve slam. This height of rise
and drop is governed by the circumference rather than the port area.
Experience and practice has shown that a 1/2-inch limit of lift is
reasonable and does ensure a smooth working pump under all ordinary
conditions.

_c._ The following table gives minimums for aggregate valve port area and aggregate valve outlet area, for the different size plungers, figured on a basis of 56% of plunger area for a 12-inch stroke, and 64% for a 16-inch stroke.

===+=======================+=========+========+=======+========
| =Size of Pump.= | =500= | =750= |=1000= |=1500=
| | =Gal.= | =Gal.= | =Gal.=| =Gal.=
+-----------------------+---------+--------+-------+--------
=1=| Diameter of plunger. | | | |
| Inches | 7-1/4″ | 9″ | 10″ | 12″
+-----------------------+---------+--------+-------+--------
=2=| Area of plunger in | | | |
| sq. inches | 41·28 | 63·62 | 8·54 | 113·10
+-----------------------+---------+--------+-------+--------
| 56% of plunger area, | | | |
| or Minimum aggregate | | | |
=3=| valve port area | | | |
| allowed per section. | | | | 64% =
| Square inches | 23·11 | 35·63 | 43·98 | 72·38
+-----------------------+---------+--------+-------+--------
| Minimum aggregate | | | |
=4=| valve port | | | |
| circumference, allowed| | | |
| per section. Inches | 46·22 | 71·26 | 87·96 | 144·76
+-----------------------+---------+--------+-------+--------
| Minimum aggregate | | | |
| valve outlet area | | | |
=5=| allowed per section | | | |
| for valves lifted | | | |
| 1/2 inch high. | | | |
| Square inches | 23·11 | 35·63 | 43·98 | 72·38
---+-----------------------+---------+--------+-------+--------

_d._ If we consider using any one of the three sizes of valves below, whose port areas may be assumed approximately as

=========+================+===========+================
Diam. | Diam. of Valve | Circ. of | Valve Port
Valve. | Port. Circ. | V. C. | Area (Net).
| | Circle. | Square inches.
---------+----------------+-----------+----------------
3″ | 2-1/2″ | 7·85″ | 3·5
3-1/2″ | 3″ | 9·42″ | 4·7
4″ | 3-1/2″ | 10·99″ | 6·3
---------+----------------+-----------+----------------

given, then the necessary number of valves per section will be as in the table following:

=================+============+============+============+=============
=Size of Pump.= | =500= | =750= | =1000= | =1500=
| =gal.= | =gal.= | =gal.= | =gal.=
-----------------+--+------+--+--+------+--+--+------+--+--+------+---
=Size of Valves.=|3″|3-1/2″|4″|3″|3-1/2″|4″|3″|3-1/2″|4″|3″|3-1/2″|4″
-----------------+--+------+--+--+------+--+--+------+--+--+------+---
Necessary number | | | | | | | | | | | |
of valves | | | | | | | | | | | |
to satisfy | | | | | | | | | | | |
(4) under _c_ | 6| 5 | 5| 9| 8 | 7|11| 10 | 8|19| 16 |14
-----------------+--+------+--+--+------+--+--+------+--+--+------+---
Necessary number | | | | | | | | | | | |
of valves | | | | | | | | | | | |
to satisfy | | | | | | | | | | | |
(3) under _c_ | 7| 5 | 4|10| 8 | 6|13| 10 | 7|21| 16 |12
-----------------+--+------+--+--+------+--+--+------+--+--+------+---

The exact number and size of valves will, however, not be insisted upon provided the aggregate valve area and the aggregate valve outlet area for each section is not less than that given in the table under _c_ for the limiting lift of 1/2 inch.

Manufacturers will note that with the established lift of 1/2
inch, the 3-1/2-inch valve will permit a valve outlet area more
nearly equal to its port area than will either the 3-inch or 4-inch
valves, and a _relatively_ less number of valves will satisfy the
specifications.

34. DELIVERY VALVES.

_a._ The total lift of delivery valves must not exceed one-half inch.

This is to avoid valve slam, as explained in Art. 33.

_b._ The aggregate valve-port area should be restricted to about two-thirds the suction-valve area.

A small restriction of water-way through the delivery valves steadies
the action of the pump and tends to prevent undue pulsations of
pressure in the delivery pipe or fire hose. Fewer delivery valves
than suction valves are, therefore, preferred, and if extra holes
in the delivery deck are cast for shop purposes these had better be
plugged than fitted with valves.

The suction valves require more generous port-circumference and
port-area than delivery valves because when a pump has to suck its
supply through a considerable height or through a long pipe there
should be the least practicable waste of the atmospheric pressure in
getting the water into the plunger chamber, or in retarding it from
following the plunger in full contact. With the water once into the
plunger chamber there is plenty of steam pressure available to force
it out through the delivery valves.

35. VALVE SPRINGS, GUARDS AND COVERS.

_a._ All valve springs must be of the best spring brass wire, and must be coiled on a cylindrical arbor.

Conical valve springs are not approved because the strain is not
uniform throughout spring, thereby increasing the liability to
breakage and the chance of their getting out of center and becoming
“hooked up.”

_b._ The valve spring must be held centrally at its top by resting in a groove in valve guard, substantially as shown in Fig. 9.

_c._ A light, rustless metallic plate must be interposed between the bottom of the spring and the rubber valve, and must be the full area of the valve. This plate must also be formed with a raised bead to guide the spring at the bottom.

The weight of this plate should be small, for the inertia of the
lifting parts of the valves should be the least possible, to permit
quick action and to avoid pounding.

_d._ For the average condition of a 10 or 15-foot lift, the stiffness of suction valve springs should be such that a force of about one pound per square inch of net port area will lift valve 1/4 inch off its seat.

The springs on the delivery valves should ordinarily be from two to three times as stiff as just specified, but any other reasonable degree of stiffness which is proved to work well in practice will not be objected to.

For suction under a head, the greater snap with which water enters
the plunger chamber when thus pushed in by say twice the atmospheric
pressure renders it difficult to avoid water hammer at high speed.
Extra stiff suction valve springs will commonly aid in controlling
this and should be used wherever pumps are to work under a head.

An approved type of indicator water gate on the suction pipe near the
pump, which can be partly closed, will enable the pump to run quietly
at high speed. Such a gate is an extra not included in price of the
pump.

36. STICKING OF VALVES.

_a._ Steam fire-pumps should be started, to limber them up, _at least_ once a week.

Although vulcanized India-rubber is much the best material yet used
for fire-pump valves, unfortunately the brass is sometimes corroded
by the free sulphur contained in the rubber, so that if the pump is
left standing for several weeks the rubber valve discs may become
stuck to their brass seats, and, if suction has a high lift, there
may not be vacuum enough to tear all the suction valves open when
pump is started.

37. VALVE SEATS.

_a._ All water valve seats must be of bronze composition. They may be either screwed into the deck on a taper or forced in on a smooth taper fit. With either arrangement, the seat must be either flanged out on the under side all the way round or be provided with a substantial lug opposite each rib, these lugs being expanded out after the valve is inserted.

If the valve seats are not expanded after being put in place, there
is a possibility that now and then a valve seat will work loose and
come out, thus crippling the pump.

_b._ The under side of the valve deck must be rounded over to give good bearing for the expanded part of the seat.

_c._ Three-inch valves must have four or five ribs, three and a half inch valves five or six ribs, and four inch-valves six ribs.

Enough ribs must be provided to give proper support to the rubber
valve, but too many are objectionable, as small ports would be liable
to obstruction by refuse.

_d._ The edges of the valve-seat ports must be moderately rounded over, to remove such sharp edges and points, as would be liable to cut, or damage the rubber valve when under pressure.

38. VALVE STEMS.

_a._ All valve stems must be of 3/4-inch Tobin bronze and of the fixed type, and must have the guard fastened on by one of the methods shown in Figs. 9 and 10.

Other methods may be approved, in writing, if found by test and
experience to have especial merit.

_b._ These stems must be screwed into the seats on a straight, tightly fitting thread, and the lower end then well headed over into a countersink. The valve guard and nut must be of composition.

In Fig. 9 the upper part of the stem is slabbed off on two opposite
sides and fits a corresponding hole in the guard.

The guard, therefore, cannot turn. The outside of the special nut is
fitted on a taper to the inside of the guard, and the nut tapped out
to fit the 5/8 U. S. thread on the stem.

The action of the valve, whether with the spring or without, tends to
drive these taper fits together, producing a frictional lock similar
to that of a friction clutch; and although the nut may be loose on
the thread, it cannot possibly work off.

It will be apparent that the taper fit on the nut must be so made as
to always bear on the taper fit in the guard, and not bottom in the
guard.

It is believed that with the present screw machine practice in shops
of to-day these small parts can readily be turned out accurately and
cheaply in large quantities. The nuts and guards made in any one
shop must be exactly of standard dimensions, so that the product of
different periods will be interchangeable.

The taper should be about one inch to one foot. With this taper the
nut can be readily turned in or out, but there is friction enough to
hold the guard and nut together even if the spring is off.

In Fig. 10, the top of the guard is recessed in the form of a hollow
inverted pyramid of six sides, to correspond to a hexagonal nut. The
angle of two opposite sides of this recess, which should be about 75
degrees, will both surely lock the nut and still permit of its being
turned with a wrench.

The guard is kept from turning by slabbing off the stem, in the same
manner as described and shown in Fig. 9.

To facilitate the removal of the nut, the edges should be slightly
chamfered. An unfinished nut simply drilled and tapped is all that is
desired. Any hexagonal or square nut within the size of the tapered
recess will be locked.

With this construction, the nut cannot turn in either direction without compressing the spring and is therefore locked, and, in the event of the spring breaking or being left off, the nut is well protected in its recess from the possible turning effects of water currents, and experiments have shown that it will still stay in place.

With machine molding it will be possible to make these guards complete in foundry, requiring no machine work further than a possible broaching out of hole to fit the stem, as a fairly good fit is necessary.

While both of these devices are effective even though not tightened down to a shoulder, they should be so tightened for greater safety and to fix the lift at the half-inch limit.

39. PIPE SIZES.

_a._ Water and steam pipe connections must have standard flanges to connect with pipes of the sizes given below.

=============+==============+===============+========+========
Size of Pump.| Diameter of | Diameter | Steam | Exhaust
Gal. Per Min.| Suction Pipe.|Discharge Pipe.| Pipe. | Pipe.
| Inches. | Inches. | |
-------------+--------------+---------------+--------+--------
500 | 8 | 6 | 3 | 4
750 | 10 | 7 or 8[C] | 3-1/2 | 4
1,000 | 12 | 8 | 4 | 5
1,500 | 14 | 10 | 5 | 6
-------------+--------------+---------------+--------+--------

[Footnote C: Eight-inch preferred, this being the more common size for valves, fittings, and pipes.

These suction pipe sizes, although larger than common for trade pumps of the same size, are believed to be amply justified by experience, and exert a powerful influence toward enabling the pump to run smoothly at high speed with water cylinders filling perfectly at each stroke. No defect is more common than restricted suction pipes.]

_b._ A single suction entrance at the end of the pump is to be provided unless otherwise specified by the purchaser.

Some situations render desirable side suction entrances, for
permitting drafting water from two different sources of supply. These
additional openings are to be considered as extras. Ordinarily, the
purchaser can provide for such situations by proper piping at the
single end suction entrance.

If there is to be but one suction opening on casting, this had best
be at center, for the reason that, if suction pipe ever gets to
leaking air, this air stands a better chance of being distributed
equally to the two plungers, and has less tendency to make the pump
run unevenly.

_c._ Standard flanges and standard bolt layouts as adopted by the Master Steam Fitters, July 18, 1894, must be used on all the above pipe connections, as per table given below.

SCHEDULE OF STANDARD FLANGES.

==============+==============+========+==============+=========
Size of Pipe ×| Diameter | Number | Size | Flange
Diam. | of | of | of |Thickness
of Flange. | Bolt Circle. | Bolts. | Bolts. | at Edge.
| | | |
Inches. | Inches. | | Inches. | Inches.
--------------+--------------+--------+--------------+---------
3 × 7-1/2 | 6 | 4 | 5/8 × 2-1/2 | 13/16
3-1/2 × 8-1/2| 7 | 4 | 5/8 × 2-1/2 | 7/8
4 × 9 | 7-1/2 | 4 | 3/4 × 2-3/4 | 15/16
4-1/2 × 9-1/4| 7-3/4 | 8 | 3/4 × 3 | 15/16
5 × 10 | 8-1/2 | 8 | 3/4 × 3 | 15/16
6 × 11 | 9-1/2 | 8 | 3/4 × 3 | 1
7 × 12-1/2 | 10-3/4 | 8 | 3/4 × 3-1/4 | 1-1/16
8 × 13-1/2 | 11-3/4 | 8 | 3/4 × 3-1/2 | 1-1/8
9 × 15 | 13-1/4 | 12 | 3/4 × 3-1/2 | 1-1/8
10 × 16 | 14-1/4 | 12 | 7/8 × 3-5/8 | 1-3/16
12 × 19 | 17 | 12 | 7/8 × 3-3/4 | 1-1/4
14 × 21 | 18-3/4 | 12 | 1 × 4-1/4 | 1-3/8
--------------+--------------+--------+--------------+---------

Do not drill bolt holes on center line, but symmetrically each side of it.

On steam and exhaust openings loose flanges threaded for wrought-iron pipe must be provided.

Where the situation will not permit of a standard flange on exhaust
opening for lack of room, a special flange threaded to fit the proper
size wrought-iron pipe may be used.

40. AIR AND VACUUM CHAMBERS.

_a._ Air and vacuum chambers in accordance with the sizes given in the following table must be provided with all pumps. If the air chamber is cast iron, the pump manufacturers must warrant that it has been subjected to a hydraulic test of 400 lbs. per square inch before it is connected to pump.

It is to be thoroughly painted inside and out to diminish its porosity.

SIZE OF VACUUM AND AIR CHAMBERS.

====================+===================+================
| Vacuum Chamber is | Air Chamber is
| to contain:— | to contain:—
--------------------+-------------------+----------------
500-gallon pump. | 13 gallons. | 17 gallons.
750 „ „ | 18 „ | 25 „
1,000 „ „ | 24 „ | 30 „
1,500 „ „ | 30 „ | 40 „
--------------------+-------------------+----------------

The air chamber, combined with connections for discharge pipe, relief
valve, and hose valves, should be carefully designed to make the
whole weight as small as possible. Keeping this weight down makes
the pump run steadier and brings less strain on the flanges at high
speeds.

An air chamber of hammered copper and warranted tested under a
hydraulic pressure not less than 300 lbs. per square inch is a little
better than cast iron as it holds air better, and being lighter it
wrenches and strains the pump less when running fast and shaking, but
because it costs from $25 to $50 more than cast iron, it is not often
adopted.

_b._ The vacuum chamber must be attached to the pump in the most direct way practicable, but provision must be made for attaching it in such manner as not to prevent readily taking off the cylinder heads.

_c._ Every vacuum chamber should be provided on one side near the top with a 1/4-inch pipe hole plugged. This to be used for attaching a vacuum gauge if desired.

41. PRESSURE GAUGE.

_a._ A pressure gauge of the Lane double tube spring pattern with 5-inch case, must be provided with the pump, and connected near to inboard side of air chamber, as shown in Fig. 12, by a 1/4-inch cock, with lever handle.

The dial of this gauge should be scaled to indicate pressures up to 240 lbs. and be marked “WATER.”

This kind of gauge is used on locomotives and is the best for
withstanding the vibration which causes fire-pump gauges to be often
unreliable. Moreover, this double spring form is safer against
freezing.

42. HOSE VALVES.

_a._ Hose valves must be attached to the pump (and included in its price) as follows:—

For the 2 stream or 500-gal. pump, 2 hose valves.
For the 3 stream or 750-gal. pump, 3 hose valves.
For the 4 stream or 1,000-gal. pump, 4 hose valves.
For the 6 stream or 1,500-gal. pump, 6 hose valves.

These are to be 2-1/2-inch straightway brass valves, without cap,
and similar and equal in quality to those made by the Chapman Valve
Company, the Ludlow Valve Company, or the Lunkenheimer Company.

The hose-screw at end of these valves is to be fitted to a hose
coupling furnished by the customer, or where this cannot be procured
may be left with the thread uncut.

To accommodate locations where all the lines of hose must lead off
from one side of the pump—makers can furnish a spool piece or special
casting to which the hose valves can be attached—but this is an extra
not included in the regular price.

43. SAFETY VALVE.

_a._ A safety or relief valve of the Ashton, Crosby, American, or other make agreed upon in writing with this office, is to be regularly included in the price, and is to be attached to each pump; preferably extending horizontally inboard from base of air chamber, as shown in Fig. 12, so that its hand-wheel for regulating pressure is within easy reach. This hand-wheel must be marked very conspicuously as shown in Fig. 11.

_b._ This valve is to be set ordinarily at a working pressure of 100 pounds to the square inch, and is to be of such capacity, that when set at 100 pounds it can pass all the water discharged by the pump at full speed, at a pump pressure not exceeding 125 pounds per square inch.

For 500-gallon pump a 3 inch valve.
For 750-gallon pump 3-1/2 inch valve.
For 1,000-gallon pump 4 inch valve.
For 1,500-gallon pump 5 inch valve.

The relief valve must discharge in a vertical downward direction into a cone or funnel secured to the outlet of the valve. (See Art. 44.)

The valve must be so attached to the delivery elbow and discharge cone by flange connections as to permit of its ready removal for repairs without disturbing the waste piping.

44. DISCHARGE CONE.

_a._ This cone should be so constructed that the pump operator can easily see any water wasting through the relief valve, and its passages should be of such design and size as to avoid splashing water over into the pump room.

_b._ The cone must also have a one-inch tapped connection for the air-vent pipe required by Art. 45, and the arrangement must be such that the pump operator can easily tell whether water is coming from the air pipe or is wasting through the relief valve.

_c._ The cone should be piped to some point outside of the pump house where water can be wasted freely, the waste pipes being as below.

===============+====================
SIZE OF | DIAMETER OF WASTE
PUMP. | PIPE FROM CONE.
---------------+--------------------
500-gallon. | 5 inches.
750 „ | 6 „
1,000 „ | 7 „
1,500 „ | 8 „
---------------+--------------------

The waste pipe can pass down to floor between the yokes at middle
of pump. It should be piped in such a way that steam and gases from
other drains or waste pipes will not work back through it, and, by
being troublesome in the pump room, suggest the covering of the cone
in any way, as it is desirable that the pump operator should always
be able to see instantly any waste from the relief valve or air vent.

This cast-iron cone, connected to the safety valve and air vent, is included in price of pump, but the waste pipe beyond it is not.

45. AIR VALVE.

_a._ An air vent with a brass gate valve and brass pipe for connecting up, must be provided and connected with delivery elbow and discharge cone.

_b._ The size of this air vent should be one inch for 500-gallon and 750-gallon pumps, and one and one-fourth inches for the 1000-gallon and 1500-gallon sizes.

_c._ The hand wheel of this valve must be marked as per Fig. 13. The lettering must be very open, clear and distinct, not liable to be obstructed by grease and dirt, and of a permanent character.

The object of this valve is to reduce the pressure above force valves
and secure a prompt riddance of all air that may come through the
water cylinders when first starting up.

This valve, of course, should be closed when once pump is under way,
to prevent waste of water.

46. PRIMING.

_a._ Each pump must be fitted with a set of brass priming pipes and valves, according to either one or the other of the following methods:

_b._ For 1,000 and 1,500 gallon pumps, the priming pipes must be 1-1/4 inches. For the 500 and 750 gallon pumps, the pipes must be 1 inch. Pump-makers are to furnish these pipes and the fittings called for below, and are to connect them up providing a 2-inch outlet, looking upwards, ready for the supply from the priming tank.

The pipe from the priming tank to this outlet should be at least
2-inch, and may be of iron, and is to be furnished by the purchaser.
All parts furnished by the pump-maker are to be of brass, and are to
be included in the price of the pump.

CONTROLLABLE VALVE ARRANGEMENT.

_c._ Four 2-seat controllable valves, one for each pulsation chamber, and of the general type illustrated in Fig. 14, must be provided. In these the inlet of water and outlet of air are simultaneously opened and closed by the pump operator.

Objection has been raised to this double-seated valve from the
possible difficulty of keeping both seats tight. If desired, the
valve may be fitted with a flange instead of a screw connection, and
the stem between the two seats somewhat enlarged and provided with a
suitable spring, thus giving flexibility between the two seats and
preventing all trouble from uneven wear.

_d._ The hand-wheel of each of these valves must be marked as per Fig. 15, so that the pump operator I may clearly understand their use. The lettering must be very open, clear and distinct, not liable to be obscured by grease and dirt, and of a permanent character.

_e._ There must be provided and fitted to each combined valve a check and umbrella-top air vent, as shown in Fig. 16. This fitting must have a clear passageway through it, the full equivalent of a 1/2-inch bore.

The check-valve is to permit the outflow of air, but to prevent the
influx when the plunger is sucking.

This method is preferred to the one using rubber priming checks, as
now and then a rubber valve will stick on its seat and thus prevent
priming of one of the chambers. In this arrangement the pump operator
has absolute control over the priming water into each chamber.

Another advantage is that the connection of the air-vent with the
priming valve ensures that the air-vents will be opened; and further,
by the vigorous spurting out of water as soon as the pump is primed,
the pump operator is reminded that the priming valve should be closed.

Should the pump operator, however, through a mistaken idea of
the proper method of operation, think that the priming should be
continued until all air was exhausted from the suction pipe and the
pump running in normal condition, there would be some by-passing
between chambers, but as there is a free vent for the air, the main
result would be simply to limit the amount of air exhausted per
stroke, from the main suction, by the amount of water which entered
a chamber in this way. The amount of water thus entering, however,
would not be appreciably greater than that which would enter from the
priming-tank with the check-valve arrangement.

If, even in spite of the warning given by the spurting air-vents,
the pump operator should neglect to close the priming-valves when
the pump was running normally, the priming-tank would eventually
be overflowed; but this would not be as serious as the drawing in
of air from an exhausted priming-tank, which would result with the
check-valve method, were the main 2-inch valve similarly neglected.

RUBBER CHECK VALVES.

_f._ Four rubber check valves, one for each pulsation chamber, and similar to ordinary pump valves, must be provided. The chambers for these should preferably be made as a part of the pump cylinder, thus securing a compact arrangement.

Figure 12 shows this arrangement in outline.

_g._ The valve seat should have three ribs to the central hub, supporting the rubber valve. The net port area through the valve should be not less than 1-1/2 square inches.

This valve seat should rest in an inverted position, and can be so
fitted up as to be readily removed. The valve stems can be of the
removable type screwing into the seat, but must be made long enough
to receive a check nut on the opposite side of seat. This will
effectually lock the stem in place.

_h._ Care must be taken to arrange the water passages through and about these priming checks, so as to avoid all air pockets and so as to reduce to a minimum the possibility of the valves becoming choked up by refuse.

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Pumps and Hydraulics, Part 1 (of 2)Chapter XI: Part 11

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