OPW Counterbalance 788, Counterbalance 790, Counterbalance 789 Series Manual

Manual - Loading Arm

April 2011

Equipment: Torsion Balance Type: 790A,B,C

Balance Unit for balancing Loading Arms

Suitable for: Loading Arm Balancing

• Easy, Precise Adjustment

• No special tools required

Specications

Right-Hand: 790A-0020 (White),

Type

790B-0030 (Yellow), 790C-0050 (Red)

Left-Hand: 790ALH-0025 (Black),
790BLH-0035 (Gray), 790CLH (Orange)

790 Series Counterbalance

Working
Temperature Range

-4°F to 176°F (-20°C to +80°C)

Installation

Spring Unit Assembly

1. Position balance unit on the bosses at back of swivel joint.

2. Fix balance unit with Bolts and Lock Washers.

3. Attach backside of Link Arm [17] to Spring Arm [15] with Pin [16] and 2 Retaining
Rings [14].

4. Remove the 4 Socket Head Screws [18] and take Snubber Block [26] off.

5. Raise loading arm to highest position (as vertical as possible).

6. Attach front side of Link Arm [17] to mounting ears on loading arm with Pin [16] and
2 Retaining Rings [14].

7. Check balancing action by pulling down the arm. If adjustment is necessary,

follow adjustment instructions below.

8. Install lock-down unit 788-L, if used, by following 788-L installation instructions.

9. Replace Cover [21] using alignment pins [1] and latches [22].

Adjustment

When to adjust torque

A. To raise loading arm higher or for more lifting action INCREASE torque.
B. To decrease loading arm vertical travel or to slow the rate at which the arm rises,

DECREASE torque.

C. Note: Prior to any disassembly, Spring balance tension should be completely relieved to allow

safe disassembly of level arm.

Torque For more lifting action increase torque. For less lifting action decrease torque.

Place ¾" socket wrench on worm gear hex drive.

NEW: Easy-to-use

Spring Cover Latch

To INCREASE torque rotate the worm gear hex drive
counterclockwise (to the left).

To DECREASE torque rotate the worm
gear hex drive clockwise (to the right).

Release wrench and test loading arm
lifting action.

Note: Prior to any loading arm
disassembly, spring tension should be
completely relieved.
Tip: Spring coil will be loose in housing
when completely relieved of tension.

Worm Gear Hex Drive

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Manual - Loading Arm

April 2011

790 Series Counterbalance

Parts List: 790 Series Counterbalance

Index Qty Part # Description

1 4 H-31396-M Spirol Pin, 1⁄4 x 13⁄4

2 1 C-20185-BW Spring Regulator, R.H. Worm Gear

3 1 H-30744-M Dowel Pin .25 x 1.25

4 2 H-01490-M

5 2 H-32283-M Retaining Ring, CST ZP

6 2 H-32282-M Bearing, Cylindrical, Bronze

7 1 H-30743-M Washer, Thrust, ZP, 7⁄8"

8 1 C-20184-EW Drive Worm, Torsion Spring

9 2 H-30741-M Screw, Drive #10 x 3⁄8"

10 1 H-30740-M Worm Cover Plate, Spring Balance

11 1 H-30018-M Bolt, 1⁄2"-13 x 31⁄2

12 1 H-30049-M Jam Nut, Hex, CST, ZP, 1⁄2"-13

13 1 E20074D1 790 Support Bracket, D1

14 2 H-30321-M Retaining Ring, CST,

15 1 D-00350-D1 Spring Arm, PTD, D1

16 1 H-30320-RE Pin, Torsion Spring, SST

Flange, Bearing, BRZ. 11⁄2" DIA x
11⁄4" LG

5

⁄8"

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Index Qty Part # Description

17 1 E-20041-D1 Link Arm, D1

18 4 H-31278-M Socket Head Screw, ZP, .31-18 X 1"

19 2 H-02507-M Lockwasher, CP, 5⁄8"

20 2 H-05910-M

21 1 E20116P 790 Spring Balance Cover, RH

22 2 H32321M Spring Cover Latch (SouthCo)

23 4 H32322M Screw, Thread Forming, 8-32

24 1 C-00626-M Spring, Torsion, C

25 1 H-30742-RS Bar, Safety

26 1 H-01489-D1 Snubber Block, RH, D1

27 4 H-03563-M Washer, Lock, ZP, 5⁄16"

28 1 H-01486-RB

29 1 H-01487-RE

30 1 H-01502-M Spring, Compression, ZP

31 1 C00635D1 Support, RH Side, D1

Screw, Hex Cap, CST, ZP, 5⁄8"-11
x 13⁄4"

Snubber Retainer, Brass, 11⁄8-12
x 1⁄2"

Snubber Plunger, SST, 15⁄16" DIA x
19⁄16" LG

Manual - Loading Arm

April 2011

788, 789, 790 Series Counterbalance

Travel Stop 788, 789, 790 Series

Upward Downward

Remove the (4) socket head screws in snubber block, then rotate
snubber block toward pivot pin to allow for more upward travel or
away from pivot pin for less upward travel.
Replace the (4) screws and tighten.

Loosen Jam Nut (located below lever arm) and turn
stop bolt in for more downward travel or out for less
downward travel. Then hold bolt and tighten jam
nut securely.

Pivot Pin

Snubber Block

Jam Nut

Stop Bolt

Adjustment 788, 789 Series

NOTE: Left hand spring balance shown.
NOTE: The worm gear adjustment mechanism provides signicant mechanical advantage during adjustment.

Under high load conditions (790) it is recommended that the loading arm be raised to approximately 45° above horizontal.
Under low load conditions it is possible to adjust the spring torque without raising/supporting the loading arm.

For more lifting action increase torque.
For less lifting action decrease torque.

1. Raise loading arm to highest position and secure.

2. Hold Adjusting Nut of Spring Regulator [2] with

a large wrench.

3. Loosen lower Bolt of Spring Keeper and remove upper one.

Using a large screwdriver push Spring Keeper forward.
With Spring Keeper disengaged turn Spring Regulator
Adjusting Nut clockwise for more or counter clockwise
for less torque.

Spring Keeper Bolts

788, 789 Series

4. With spring tension in desired position press Spring Keeper

back into position on Spring Regulator. While holding Spring
Regulator Adjusting Nut, tighten Spring Keeper Bolts [3].
Be sure Lock Washers [4] are in place.

5. Minor adjustment can be achieved by turning the Spring

Keeper ½ position. This is done by removing the 2 Keeper
Bolts [3] and turning the Spring Keeper end for end, so that
the “teeth” of the Spring Keeper will be reversed.

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788, 789 Series

Spring Keeper

Manual - Loading Arm

April 2011

788, 789 Series Counterbalance

Parts List: 788, 789 Series Counterbalance

4 5

3

7

8

6

9

10

No. Part

1 Torsion Spring

2 Spring Regulator

3 Bolt

4 Lock Washer

5 Spring Keeper

6 Spring Arm

7 Lever

8 E-ring

9 Pin

10 Support Bracket

11 Bearing Flange

12 Side Support

No. Part

13 Snubber Block

14 Lock Washer

15 Bolt

16 Bolt

17 Nut

18 Screw

19 Cover (NOT SHOWN)

20 Spring Compression

21 Snubber Retainer

22 Snubber Plunger

23 E-ring

24 Pin

2

23

24

15

14

13

11

19202122

1231

16

17

3

18

Maintenance 788, 789, 790 Series

Lubrication The torsion balance is provided with a self-lubricating Cylindrical Bearing. Only when operating under

severe conditions, a little oil may be applied to Bearing [7]. Pins [13] on Spring Arm [23] and Link Arm [9]
should have some oil quarterly.

Safety

Danger! Before performing any maintenance, always secure the Loading Arm and remove
all tension from the counterbalance -- a torsion spring. The Loading Arm counterbalance
spring contains a substantial amount of stored energy. You must relieve this energy before
any disassembly. Failure to remove all tension from the counterbalance spring of the

Loading Arm before maintenance may cause serious personal injury or death.

WARNING! While installing and using the Loading Arm, always wear adequate personal
protection, including hard hats, gloves, and steel-toed work boots. Failure to wear
adequate personal protection may cause serious personal injury or death.

WARNING! Always follow the procedures prescribed in this Document. Failing to follow
the procedures prescribed may damage the Loading Arm and cause serious personal
injury or death. Consult Loading Arm Installation, Maintenance & Safety Manual for
more details.

PHONE: [phone] • [phone] • Fax: [phone] • [phone]

2726 Henkle Drive • Lebanon, OH 45036 • www.opw-es.com