THE WATER END.

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 over1⁄16of an inch in thickness is sufficient to secure perfect tightness.

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 over1⁄16of 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 forthe 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 shell when of nearly cylindrical formInches.Inches.Inches.Inches.7⁄8111⁄811⁄4Thickness of valve decks when well ribbed11⁄411⁄411⁄411⁄4Thickness of transverse partition, depending on ribbing11⁄4to 11⁄211⁄4to 11⁄211⁄2to 211⁄2to 2Thickness of longitudinal partition, depending on ribbing11⁄4to 11⁄211⁄4to 11⁄211⁄4to 211⁄2to 2Thickness of ribs3⁄47⁄811Thickness of suction chamber5⁄83⁄43⁄47⁄8Thickness of delivery chamber7⁄8111⁄811⁄4

Thickness of cylinder shell when of nearly cylindrical form

Thickness of valve decks when well ribbed

Thickness of transverse partition, depending on ribbing

Thickness of longitudinal partition, depending on ribbing

Thickness of ribs

Thickness of suction chamber

Thickness of delivery chamber

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 than3⁄4-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 pipesto 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.

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 pipesto 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.

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; andthis 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.

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.Diameter7 or 71⁄4-in.9-in.10 or 101⁄4-in.12-in.Length17-in.17 „18-in.24 „Thickness of transverse partition5⁄8„5⁄8„3⁄4„3⁄4„Thickness next to partition1⁄2„1⁄2„5⁄8„3⁄4„Thickness next to end5⁄16„3⁄8„3⁄8„1⁄2„Number of ribs4466Thickness of ribs5⁄16„5⁄16„3⁄8„3⁄8„Bushing.Length7 „7 „8 „10 „Thickness at end5⁄16„3⁄8„3⁄8„1⁄2„Thence tapered evenly to athickness next to bearing ofnot less than1⁄2„5⁄8„5⁄8„3⁄4„Thickness at thecenter bearing not less than3⁄4„3⁄4„3⁄4„13⁄16„

Plunger.

Diameter

Length

Thickness of transverse partition

Thickness next to partition

Thickness next to end

Number of ribs

Thickness of ribs

Bushing.

Length

Thickness at end

Thence tapered evenly to athickness next to bearing ofnot less than

Thickness at thecenter bearing not less than

a.The “water piston with fibrous packing” is preferred for many situations in the West or South, or for water containinggrit 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. 28d, 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 gal.750 gal.1000 gal.1500 gal.Solid Bronze.Thickness at extreme end7⁄16-in.1⁄2-in.1⁄2-in.9⁄16-in.Tapered evenly from end to a thicknessnext to bearing of not less than9⁄16„5⁄8„11⁄16„3⁄4„Thickness at center bearing at least3⁄4„3⁄4„3⁄4„13⁄16„

Solid Bronze.

Thickness at extreme end

Tapered evenly from end to a thicknessnext to bearing of not less than

Thickness at center 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.

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.

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 about1⁄2-inch greater than the diameter of the valve-port circle which it covers, thus affording about1⁄4-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.

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 than5⁄8-inch.

a.The total lift of suction valves must not exceed1⁄2-inch.

b.The net suction valve port area and the total suction valve outlet area under valves lifted1⁄2inch high must not be smaller than the figures given in the table below.

(1) Length of Stroke (in inches)1216(2) Greatest No. revolutions per minute.7060(3) Corresponding Piston travel per minute.140160 ft.Approx. actual max. Piston velocityat full speed, per row (3) × 2.2.(4) Feet per minute.308352(5) Feet per second.5.15.9(6) Net Suction Valve-port area speed regardednecessary for this per cent. of Plunger area.56%64%(7) Total Suction Valve Outlet Area under Valveslifted1⁄2in. high.56%64%(8) Discharge Valve Area.2/3 of Suction Valve Area.

(1) Length of Stroke (in inches)

(2) Greatest No. revolutions per minute.

(3) Corresponding Piston travel per minute.

Approx. actual max. Piston velocityat full speed, per row (3) × 2.2.

(4) Feet per minute.

(5) Feet per second.

(6) Net Suction Valve-port area speed regardednecessary for this per cent. of Plunger area.

(7) Total Suction Valve Outlet Area under Valveslifted1⁄2in. high.

(8) Discharge Valve Area.

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 portsC,Fig. 8. Thus for a 4-inch valve, with ports inscribed in a 31⁄2-inch circle, whose circumference is 3·5 × 3·1416 = 11 inches; the valve “outlet area” for1⁄2-inch lift would be 51⁄2inches.Fig. 8.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 ismore than twice as greatleads 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 a1⁄2-inch limit of lift is reasonable and does ensure a smooth working pump under all ordinary conditions.

Fig. 8.

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 ismore than twice as greatleads 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 a1⁄2-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 gal.750 gal.1000 gal.1500 gal.1Diameter of plunger. Inches71⁄4″9″10″12″2Area of plunger in sq. inches41·2863·628·54113·10356% of plunger area,or Minimum aggregate valve port area allowed per section. Square inches23·1135·6343·9864% = 72·384Minimum aggregate valve port circumference, allowed per section. Inches46·2271·2687·96144·765Minimum aggregate valve outlet area allowed per section for valves lifted1⁄2inch high. Square inches23·1135·6343·9872·38

Diameter of plunger. Inches

Area of plunger in sq. inches

56% of plunger area,or Minimum aggregate valve port area allowed per section. Square inches

Minimum aggregate valve port circumference, allowed per section. Inches

Minimum aggregate valve outlet area allowed per section for valves lifted1⁄2inch high. Square inches

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

Diam.Valve.Diam. of ValvePort. Circ.Circ. ofV. C.Circle.Valve PortArea (Net).Square inches.3″21⁄2″7·85″3·531⁄2″3″9·42″4·74″31⁄2″10·99″6·3

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

Size of Pump.500 gal.750 gal.1000 gal.1500 gal.Size of Valves.3″31⁄2″4″3″31⁄2″4″3″31⁄2″4″3″31⁄2″4″Necessary number of valves to satisfy (4) underc65598711108191614Necessary number of valves to satisfy (3) underc754108613107211612

Necessary number of valves to satisfy (4) underc

Necessary number of valves to satisfy (3) underc

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 undercfor the limiting lift of1⁄2inch.

Manufacturers will note that with the established lift of1⁄2inch, the 31⁄2-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 arelativelyless number of valves will satisfy the specifications.

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.

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.

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 inFig. 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 valve1⁄4inch 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.

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.

a.Steam fire-pumps should be started, to limber them up,at leastonce 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.

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 roundor 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.

a.All valve stems must be of3⁄4-inch Tobin bronze and of the fixed type, and must have the guard fastened on by one of the methods shown inFigs. 9and10.

Fig. 9.

Fig. 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.

InFig. 9the 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 the5⁄8U. 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.InFig. 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 inFig. 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 recessfrom 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.

InFig. 9the 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 the5⁄8U. 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.

InFig. 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 inFig. 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 recessfrom 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.

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

Size of Pump.Gal. Per Min.Diameter ofSuction Pipe.Inches.DiameterDischarge Pipe.Inches.SteamPipe.ExhaustPipe.5008634750107 or 8C31⁄241,000128451,500141056

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