Illustrated Sourcebook of Mechanical Components Part 13 ppt

This means that less than an 8- times die opening must be used if a smaller radius is desired-requir- ing higher tonnage.. When the punch radius is greater than the plate thickness, t

required In no case should the cor-

ner radius be less than thickness of

material for a one-operation draw

When the ratio of “height divided

necessary i n most cases to reduce

the flat blank to the finished shell

by using two or more draw dies of

proportionately decreasing diame-

ters In some cases, one or more an-

nealing operations will be necessary

between first and finish draw opera-

tions The necessity of annealing de-

pends to a large extent on the work-

ability of the metal being drawn

Determination of the number of

reductions necessary to draw a shell

with ratios (height divided by diam-

by hard and fast rules In general,

for ductile materials, with generous

corner radius in the shell, the re-

quirements are:

1 Height equals % to 1Y’ times

the diameter of the shell-two

reductions will be required

2 Height equals 1% to 2 times the

ductions will be required

3 Height equals 2 to 3 times the

ductions will be required

It may be necessary to anneal the

shell when more than two reductions

are required When corner radius is

less than four thicknesses of mate-

rial, add one or two flattening dies

and operations, depending on corner

radius desired

more difficult to predict the number

of operations required In general,

terial (percent of elongation or per-

ine the maximum reduction possible

in one operation

Finish of edge depends on the

“height divided by diameter” ratio

and on the material being drawn

the “height divided by diameter”

ratio is not over 1/3, it’is possible to

produce an edge within commercial

tolerances without requiring finish-

and uniformity of the edge depends

on the size of blank used For higher shells it is not possible to do

this, and one of the following finish- ing operations will be required:

2 Pinch trim (Fig 2 )

3 Machine trim (Fig 3 )

(not suitable for small quanti- ties)

A “Draw Reduction Table” offers

a simple means of determining per- cent of draw reduction and flat- blank diameter By dividing the in- side shell height by the mean shell diameter, a height-diameter ratio is

(Fig 1)

of the table Directly opposite in Col I1 find the percent of reduction

in drawing the flat blank into a shell) Directly opposite in Col 111, find the Blank-Draw ratio Multiply the mean shell diameter by this fac- tor to obtain the approximate flat blank diameter

It must be understood that this table can only be used with round straight-sided shells or cups Shells

or cups with flanges must be inves- tigated by other methods Care must

be used when attempting to predict the number of operations required to produce a flanged shell or cup

EDGE-TRIMMING METHODS

Partly Drawn Shell Flange Trim Die Finish Drawn Shell

Fig 1 -FLANGE T R I M AND FINISH DRAW This method is satisfactory for most shells, particularly diameters greater than 2 in Only one additional die-a trimming die-is required

Draw with Flange Flattening Die Pinch Trim Die

Fig 2-PINCH TRIM DIE This method will produce a shell with uniform height, but the inside edge is considerably rounded The flange must be flat- tened to a sharp corner, which will require one or two dies

Finished Draw Machine Trim, Lathe o r Grind Finished Shell

Fig 3-MACHINE OR BOX TRIM Tooling cost i s generally low, but this method is slow The best-appearing edge is produced, and sometimes this method is the only practical one

Tonnage for Air Bends

Capacity ratings of press brakes are based in air bends in which dies do not strike

solidly on the metal All pressure is used in forming-none in coining or squeezing

Roy F D e h n

Air-bend dies produce a bend

with an inside radius approximate-

ly 15% or 5/32 of the die opening

This means that less than an 8-

times die opening must be used if

a smaller radius is desired-requir-

ing higher tonnage

Press ratings are based on die

openings of 8 times the material

thickness up to about 36 in plate

Die openings up to 10 or 1 2 times

are used for forming heavier thick-

nesses of plate

If the die opening is too large,

an excess amount of metal is drawn

into the die, causing a curve to

form in the metal each side of the

point radius

If the metal is formed over a die

opening less than 8 times the plate

thickness, there is danger of frac-

turing the metal in the heavier

thicknesses, unless a small amount

of preheat is applied

Effective width of die opening

When the punch radius is equal

to or less than the material thick-

ness, the effective width of die

opening to use with the tonnage

table, page 99, i s die width W

When the punch radius is greater

than the plate thickness, the ef-

fective width of die opening to use

with the tonnage table is 2 times

X shown on sketch

Pressure per foot

Check tonnage required from

table to be sure it is within the

capacity of the machine, making

allowance for coining and drawing

forces required on other than air-

bend dies

Bending pressure is proportional

to the ultimate strength of the ma-

terial for the same thickness and

die opening

The inside radius of a bend is approximately 5/32 of the die opening and is about the same for varying thicknesses of material bent on the same die set

Heavier thicknesses of plate con- tain higher carbon content in or- der to maintain full ultimate strength This results in more bending fractures which can be reduced by 10 or 1 2 times die open- ing or the use of special flanging steel

High tensile steel plates are usu- ally formed over 10 to 12 times die opening

The manufacturers of special steels usually recommend the radi-

us of die opening to use with their materials

Bends across grain will show less breakage than when bent in line with the grain of the plate, es- pecially in the thicker plates

It helps to avoid cracks by rounding the edges of thick plates

a t each end of the bend, on the outside of the bend

Approximate spring back:

Low carbon steel, l o to 2'

0.40 to 50 carbon steel, 3" to 4 O

Spring steel annealed, l o o to 15O The same size of press brake, as formerly used for bends of 8 times plate thickness in mild steel, is suitable for 12-times bends in the popular low-alloy steels

If less flange width is required,

a smaller die opening must be con- sidered, and this will affect the tonnage rating needed

Forming practice

Material bent on too wide a die opening may not come square Re- hitting with dies set closer in trying

to square up the bend frequently overloads the press The forming

of channel or offset bends may require more than six times the load needed for a single right angle bend in the same material

To adjust a mechanical press

Effective width of die opening

2 Run both screws down to- gether until left hand end bottoms

in die and stalls adjusting motor

3 Release adjusting clutch on cross shaft and run right hand screw down until it stalls Ram and bed are then parallel under pressure and it is only nec- essary to back up adjustment for the thickness of the material Another method is to use a short test piece under each end of the press, adjusting until equal results are obtained on both ends Use wide enough test pieces so that the unit pressure will not be high enough to indent the dies Another method is to start with a shallow bend and run the adjustment down between strokes, until the desired angle is formed However, one must check for equal angles at both ends of the bend

Dies should preferably be of a closed height so that the adjusting screws project about one to three inches

If a load is put on one end of the press so that it is substantially performed by one pitman, it should

be limited to half the press ca- pacity to avoid overloads

Tips

Tonnage v s Stroke of Press Brakes

available at different points in the stroke

Roy F Dehn

Data are based on a die opening sult the press-brake manufacturer work to be done on mechanical width W , and are correct for the with regard to the limiting effect press brakes rated with a bottom usual Drcmortions of width of die - - of the available flywheel energy stroke capacity equal to 150% of opening to material thickness

Distance A is punch travel re-

quired to make the bend, and

equals 40% of die width W Full

tonnage to make the bend is re-

quired at 0.7 A above bottom,

where W, or width of die opening

= 8 or more Also, under these

conditions, 0.7 A = 0.28 W

Problem:

What length of % in mild steel

plate can be bent on a 320-ton

brake with a 5-in stroke?

Solution:

A 3-in die opening would nor-

mally be used Therefore the height

above bottom for full tonnage

= 3 x 0.28 = 0.84 in

Percentage of stroke abcve bot-

tom stroke = 0.084 -+ 5 = 16.8%

Enter the chart at 16.8% of

stroke above bottom stroke and

draw a dash line to the stroke-ca-

pacity curve

Drop down a dash line and read

the tonnage available at 16.8% of

stroke equals 1.3 times full capac-

ity, or 1.3 X 320 = 416 tons

From the chart “Tonnage for air

bends,” (AM-March 28, ’66, p99)

find that the pressure to bend 3/s-

in plate in a 3-in wide die equals

24 tons per foot

Then, 416 +- 24 = 17 f t , or maxi-

mum length of air bend that can

be made on the 320-ton brake,

using %-in mild steel plate

This value would have to be ad-

justed upward or downward for

other materials

If alloy-steel plate is to be bent

on extra-wide die openings, con-

This chart may b e used also-for mid-stroke capacity

Tonnage vs stroke

50 r“ 45

,E 35

e +

40

0

+ +

Tonnage Chart for

Various Bend Angles

Roy F Dehn

terial must be bent to less than

a 90' bend angle, and then the accompanying chart provides a means of estimating the tonnage in relation to that required for a 90°

air bend

The chart published earlier (AM Example: What is the percentage

-March 28, '66, p99) gives the of tonnage for a 90° bend t h a t i s

tonnage per foot to produce 90' required to bend plate to an inside

air bends in various plate thick- bend angle of 1 7 5 O ?

nesses and using various die open- According to the tabulation, the

ings In many cases, however, ma- percentage is 50% Now cross

check this by using the curve AEP Solution:

Follow the 175O inside bend an- gle to the right until the dash-

line extension cuts curve AEP

Drop down to the scale for 100%

air bend tonnage, and read that 50% of that tonnage is required

If the full 90° bend in 2 in plate requires 171 tons per foot, a 175' bend will require 50% of it, or

85 tons per foot

Values given are based on punch

radius not greater than plate thickness,

and for material with up to 65,000 psi

ultimate tensile

For higher strength materials, in-

crease tonnage values in direct gro-

Press Tools for Bending

Don R King

signing press tools for parts that require bending Often,

for a given shape, there are several possible methods

To select the one best suited to your job, we give here

schematic drawings of press tools to serve as a refer-

ence guide These are classified according to standard

arrangements to produce basic bend configurations

advantages o f the particular design

I n most cases, the bend is shown as accomplished at the last station of a progressive die, in order to indicate

may apply to intermediate stations, wh,ere the bend includes only part of the strip, or is turned parallel

sketches are likely to be critical in respect to part di- mensions They should be checked for limitations of die wall thickness or space

RIGHT-ANGLE BENDS

No 1

Good location and alignment

Inclined ejection possible

Slight tendency for part to creep

No scrap waste

No 3

Alignment may depend on stock fit in stripper

Push-through ejection i s possible

Some tendency to creep

Scrap slug wasted

long cut-off punch required

No 2

Good location and alignment Inclined ejection preferred Scrap slug wasted

No creep if other punches are engaged large spring space needed i n punch holder

RIGHT-ANGLE BENDS continued

No 5

Requires inverted pierce and notch operations

N o creep if other punches are engaged

More complicated and costly than other designs

Eliminates scrap slug, when farming downward i s necessary

No creep occurs

Stroddle - - - - ' '-stock

No 6

For bends with short legs only

N o creep if other punches are engaged

No scrap l o s s More difficult to reshorpen Large spring space needed in punch holder

Distortion of stock and creep are possible

spring stop

No 11

No scrap waste Not suited to parts of all proportions Resharpening may cause some difficulty Distortion of stock b i d creep are likely

Slide

I

No 12

Widest adoptability

- Good-quality bend; are produced

More costly than other dies

Inversion of design i s possible

Inclined ejection i s desirable

Scrap slug wasted

Some difficulty in resharpening

No 16

Good-quality bends produced on short legs and sharp corners

Stock distortion occurs on long legs or when

angle i s close to 90'

no 1 3

Inclined ejection i s required Some difficulty in resharpening Special backup heel may be needed Large spring space required in punch holder

OBTUSE-ANGLE BENDS - Continued

Distorted' cut

No 18

Good design only when angle is close to 90"

Bends of good quality produced regardless of

leg length or radius

No 19

Good-quality bends when legs are short Push-through ejection i s possible Scrap slug i s wasted

large spring space needed in punch holder

CHANNELS

No 20

Good location and alignment of bends

Inclined ejection is desirable

Scrap slug i s wasted

l o n g cutoff punch i s required

I

spring sfop Possible to cbm ouf ond continue

progressive operotbns

No 21

Good design for cross-transfer operation

Inclined ejection i s desirable

Large spring spoce needed in, punch holder

Closely fitted guides or nest are required on 2nd operation

moy help operation may be employed

2nd Operation I st Operation

No 24

Good quality bends produced; even 90” bends Not used f o r heavy stock or extreme acute angles Special ejection means are required

Bends usually of poor quality, but die cost i s low

Distortion remains from “slip forming” unless

Not suited to pdarts of all proportions

straightened by spanking

‘Pivoted

die members

No 20

Bends of fair quality

Do not use for heavy stock

Die more difficult to construct, but

useful for odd angles

No 25

limited to small parts Fair-quality bends produced, but wings will not large spring space may be required in punch holder

be square unless spanked

n Oper or i o n

I st 0 p e r o t i o n

RETURN FLANGES

No 30

Two operations a r e required, but method

Special ejection means required, but Piece may be cross transferred or made in

produces good-quality bends inversion may aid ejection cut-and-carry progressive die

Z-BENDS AND OFFSETS

No 32

Fair quality bends

Slipp'age of stock will cause some

Die is low in cost

variation in, bend location

Spring ejector possible

I

Final S t a t i o n t,,j S t a t i o n

No 34

Good quality bends

Special ejection requirements

Inverted piercing and notching required

by balancing spring pressures

Wing Bending methods

Tangent and stretch bending methods and folding techniques are opening up new economies

in making sheet-metal products by wrap-around instead of multi-panel construction

Edward P Schneider

Wing-type and stretch-bending

equipment are used in the metal

working industry for the produc-

tion folding, tangent bending, and

stretch bending of preformed sheet

stock, bars, tubes, structurals, and

extrusions with sections like those

shown in Fig 1 The greatest pro-

portion of these jobs is done on

the tangent bender due to the

capabilities of the machine, its rel-

atively high production rate, and

the quality of work attainable

Material-Use of wing-type and

stretch bending machinery involves

processing parts made from vari-

ous grades of these materials:

(1) Low carbon steel

( 2 ) Stainless steel

( 4 ) Copper and brass

( 5 ) Aluminum

( 6 ) Magnesium (in heated dies)

Material properly selected and

prepared for bending operations

meets these conditions:

(1) Sufficient elongation

able for proper dies and insert

support during bending

( 3 ) More complicated preform

designs can be supported by man-

drels, or mechanically actuated die

inserts during bending

(4) A preformed section prop-

erly dimensioned for the tangent

bending process is illustrated in

Fig 2 In this typical section, as

dimensioned, it is understood that

mill tolerance of + 0.005 in.,

acceptable

The bending methods illustrat-

ed are normally used for making

up to 90" metal folds or radius

bends in flat or preformed metal

Metal folding is a wing-type

bending method by which com-

Typical preformed sheets To n g en t- bent sheets

h

Extrusions

Tongent- bent structurals and extrusions

1 These preformed sheets and tangent-bent parts are only a few of the many shapes that lend themselves to wrap-around construction of products

paratively sharp bends are made

in flat or preformed sheet metal

to produce cabinet shells and parts with sheer or well-defined corn- ers Where preformed material is processed through a metal-folding operation, corner notching is util- ized so that no side flange upset- ting or stretching is done, as in the case of tangent bending

Tangent bending is a metal-form- ing process in which flat or pre- formed material is precision-bent

to a specified radius This type of

bending is accomplished by a con- trolled rocking movement of a straight block-type 'rocker die' around a properly positioned 'ra- dius die.' The bending takes place

in small, progressive increments, always at the tangent point of

rocker die application At this tan- gent point the material is confined

so tightly between the die elements that each stage of progressive met-

al movement causes continuous flow into a wrinkle-free bend

The rocker die component in a properly designed tangent bend-

to the material being processed is positively controlled by mechani- cal means

The bending methods illustrated are normally used for making up

to approximately 100" bends in flat

or preformed metal Variations in design of a product and the bending machine result in bends up to 180' for the wing-type bending meth- ods shown in Figs 5 and 6 on special applications

The pivot point in each of the four bending methods shown cor- responds to the swing center of the bender wing in a properly designed

and efficiently maintained setup

For either of the fold-action

bending methods in Figs 3 and 4,

the pivot point is exactly in line

with the top surfaces of clamp and

wing dies, and is at a distance of

MT (or slightly less) from the

nose of the radius die

Right angle bend-fold action

This wing-type bending, or fold-

ing method, Fig 3, is usually em-

ployed in leaf-type sheet metal

bending brakes or plain wing type

folding machines where a ‘sharp’

corner is desired Although the

nose on the radius die may be ma-

chined to get a small inside radius

in a fold, actual production will

check between MT and 2 MT in-

side radius

For ‘sharp’ folds in sheet metal

having inside radius = MT (or

less) it is always advisable to con-

sider coining them on a press

brake

Radius bend-fold action

Technically this is the same ac-

tion, Fig 4, as utilized in Fig 3,

differina mainly in that a greater

uniformity of forming from end

to end of the bend is possible This

method cf fold-action radius bend-

ing requires a much greater over-

bending allowance as well as a

means of checking the unwinding

of the bend when the bender wing

swings down

Radius bend-wipe action

In this type of wing-action ra-

dius bending, Fig 5, the pipot

point, or wing swing center, cor-

responds exactly with the center

of the radius on the nose end of

the radius die

The wing die pushes the part

metal against the radius die and

skids on the outer surface of the

bend area as the bender wing

swings up This action Lwipes’ a

bend in the part metal Overbend

requirements are less and more

positively predicted in this method

of radius bending of flat sheet met-

Fig 3 Right - angle-

Tangent bending action

scribed under Figs 4 and 6 The wiping pressure is readily varied

by shimming or spring loading the wing die to give desired setting effect to the bend as it is made

Radius bend-tangent bending action

In this type of wing-action ra- dius bending, the pivot point, or wing swing center corresponds ex- actly with the center of the radius

on the nose end of the die

Die space distances are at stan- dard 3-Dlace decimal dimensions, plus 0 000 in., minus 0.002 in., for:

(1) Bolster to pivot point, verti- cal direction

beam in clamping position

( 3 ) Pivot point horizontally away from wing to beam

In this method of wing-type bending, the rocker die applies canti-lever-beam type bending forces to the material in progres- sive increments, always tangent to the radius die during the comple- tion of a bend

Normally there is no skidding of

a rocker die on part material as a tangent bend is made or as bender wing returns This feature makes the process ideal for bending pre- coated or pre-finished stock

Spring-Back Control

Don R King

The problem of springback occurs

in almost every bending operation

Even with dead-soft materials,

springback may become serious

where accuracy of the bend is re-

quired

The pressure-pad type of wiped

bend, Fig 1, is usually considered

superior, but it is not always the

complete answer A point often

overlooked is the rather high pad

pressure required This may be dif-

ficult to obtain unless a cushion is

available in the press

Standard formulas will give the

approximate holding pressure, but

in all cases the die should be tried

out in “slow motion” If at any

point in the bending stroke, a sepa-

ration can be detected between the

stock and the punch, more spring

is needed A relief angle on the

punch, as shown, and a tight wiper

setting are of some help

“SPANKING THE BEND

Another means of giving a more

definite “set” to the material is il-

lustrated in Fig 2 Here “spanking”

of the bend area occurs at the bot-

tom of the stroke Careful stroke

adjustment is required to prevent

abnormally high pressures S6me

improvement may be gained by al-

tering the spanking radius to re-

duce the area of contact, but this

partially defeats the purpose, and

does not set the entire bend area

One of the most satisfactory con-

trol methods is shown in Fig 3a

Here the pad and punch are con-

structed on an angle to compensate

for the amount of springback Uni-

formity of bends is good and not

affected by the mess stroke As an-

FIG 1 FIG 2

FIG 3a FIG 3b

plied to channels, Fig 3b, this meth- terial is ironed or stretched It

od is limited to combinations of seems doubtful that the friction in- channel width and material thick- volved can produce stretching, and ness that will not be permanently ironing mostly takes place after the overformed by the compensation bend is complete A more likely The usual explanation offered for explanation is that the wiper block the superiority of the pressure-pad, or the entire die yields, and after

FIG 4 FIG 5

covery takes place and produces a

small amount of overbending

Extension of this reasoning led t o

the construction shown in Fig 4

Controlled movement of the wiper

is introduced by means of springs

and stops The amount of move-

ment required is very small A few

thousandths past tangency will cor-

rect a considerable angle of spring-

back, and the simple spring-hinged

wiper will be satisfactory in most

cases On light material, auxiliary

springs may not be required

Until now, we nave considered

only cases where the wiper is close-

ly fitted, with stock clearance only,

and have ignored the wiper-nose

radius, as it has little effect under

this condition In Fig 5, a small

clearance is provided between

wiper and punch, in addition to

stock thickness, and the wiper

radius (actually length L ) plays

an important part in controlling

spring back When length L is in proper proportion, a small amount

of “air bending” takes place at some point in the bending cycle

This is added to the formed bend, resulting in an overbend sufficient

to counteract springlback The amount of overbend increases with

an increase in L It is also affected

by the clearance, but it is easier to maintain this at about 5 % of stock thickness and alter the nose radius

Exact dimensions will usually have

to be determined by experiment

For a starting point, Table 1 shows the approximate dimension that will produce a slight overbend

When the benld radius is large in proportion to stock thickness, the wiper radius becomes rather large

If space is limited, the nose contour shown in Fig 6 may be substituted

With this arrangement, L may be

about 60% of the dimension for a plain radius

table I LENGTH OF 1 TO OVERBEND

BEND RADIUS LENGTH L

Long U-shaped pieces are often

troublesome to make when close

tolerances are required across the

means are used in die design to

compensate for spring back And

usually strip-stock tolerances are

required in production

The method described in this

article, in the author's opinion,

is the most efficient way to control

spring back when the inside bend-

ing radius is less than three times

the stock thickness Stock with

a close thickness tolerance is not

required Regular sheet-stock tol-

part production It is also possible

to overbend a piece 2" to 3" when

required

The set corner on the die block

-

and is stopped at Yzt, as shown in Fig 1 For soft and '/4 hard CRS or aluminum, the punch is made square (without back taper) for

a 90" bend Back taper is allowed

on the punch side when overbend

is required Clearance between

to maximum stock thickness

(t,,, ) In calculating the dimen- sion h, use minimum stock thick-

plifies the calculation of h

shown in Fig 2, may be used to

set corner Dimensions are filled

in after all calculations are made

Usually it is difficult to hold

a close-tolerance bend in one bending operation for a part as shown in Fig 3 For example, a

piece with a large radius (say 8 to

10 times stock thickness) on one side and a smaller bending radius (say less than 3 times stock thick- ness) on the other side By using the set corner described, it is pos- sible to bend this part in one op- eration, The punch face and pad are ground at an angle to compen- sate for the spring back of the longer leg, Fig 4 For the shorter leg the punch side is ground with

a back taper to over-bend the shorter leg for the amount needed

Punch radius R' for the longer

leg usually is smaller than R on

the finished part It may be cal- culated* once the angle of spring back is determined by tryout

*Refer to BAO Stamping Calculator sold

by BAO Slide Co, P.O Box 7902, Chicago

80, 111

for dimensioning the die

S E C T I O N 25

7 c _

c

-

011 L S U E R PRESSURE SflOWN

Fig 5-Reuersing value This valve

direcrs oil flow in and out of either end

of an operating cylinder .4 separate

pilot value, Fig 6, controls the oil pres-

sure The reuersingwulue spool main-

mins a central position and f l o a r ~

between tur, springs Pilot ralue action

moves the spool W h e n the spool is az

one end of the valve, oil under pressure

flows from the pump through the valve

into one end of the operating cylinder,

and at the same time, oil i n the oth'er

end of the operating cylinder is dis-

clcorged into the reservoir

FROM M A I N OIL LINE

' - M I I N OIL LINE OIL T O ' FROM PUMP PILOT VALVE

FROM REVERSING VALVE ,

L!NE

I

are thrown by cams or dogs, or may be moved magnet-

ically by solenoids Oil pressure from t h e p u m p is di-

rected alternutely io both ends by means of a reversing

snlre Fig 5

Figs 7 and d -DweU and throttling values These

spring-loaded valves are actuated by cams or oil

pressure Cam action nwves the spool and shuts

o# this free oil delivery permitting only a

restricted oil flow through throttling adjustment

I n the pilot valve line, thrk d u e decOys action of

the reversing valve and permits a period of dwell

at the end of the stroke of the operating piston

The change f r o m free to restricted flw may be

abrupt or gradual, depending upon the spool em

pluyed In pressure actuated calves, Fig 8, the

talce i s no'mally held closed by the spring

Delivery of oil is restricted b y a throttling adjust-

ment as long as the valve is closed W h e n flow is

reversed, oil pressure l i f t s the valve and permits

free delivery of the oil

THROrTLlNG TO PILOT

FROM 81

MAIN

OIL LINE

LIP-SEAL SEAT requires smaiest force

to be bubble-tight Large forces flatten lip,

so design works best when differential

across seat is low Example is a relief valve

where fluid pressure opposes spring force

PLASTIC POPPET cannot stand shock loading Accurate machining for a good seal is easy because poppet guide and seat are in the same piece Best angle between cone and seat is 20 to 30"

Diaphragm

wafer and presses it to contour of the

cone This compensates for irregularities

common on large valves Wafer must be

thin enough not to wrinkle when deformed

BALL forces plastic diaphragm against spherical seat Vent will keep pressure

from building up behind the ball which is

not a force-fit in socket Spring strength determines cracking pressure

< , ,

< , , ~ .

EXISTING 6‘PIPE TO DOSING TANK-BEDS I # 2

PLAN VIEW-EXISTING METERING MANHOLE W/MODIFICATIONS

EXISTING F L O W RECORDER: STEVENS M O D E L 61 R

REPLACE EXISTING ENCLOSURE v/NEW STAINLESS STEEL,WEATHERPROOF ENCLOSURE

s ECTI o N u~ - C”

Vulve

Vblve refuiner Orifice

P uncture

pin

GO2 Cartridge

B

G