WOOD'S POWR-GRIP POWER TILT Guida di riferimento

TST-020 PT-AIR –REV. 2017-246

LEAK TEST

PROCEDURE

POWER TILT [PT] MODEL LIFTERS WITH AIR POWER SYSTEMS

TESTING AND MAINTENANCE MUST BE

DONE BY A QUALIFIED PERSON

KEEP FOR FUTURE REFERENCE

TST-020 PT-AIR –REV. 2017-246

TST-020 PT-AIR –REV. 2017-246 
TABLE OF CONTENTS 
LEAK DETECTION 
SYMPTOMS OF VACUUM LEAK 1 
DETERMINING LEAK EXISTENCE 1 
ADDRESSING LEAK 1 
BASIC REPAIR TIPS 2 
PRELIMINARY TEST 3 
VACUUM GENERATING SYSTEM TEST 4 
PAD SYSTEM TESTS 8 
SYSTEM CONFIRMATION 10 
DIAGNOSTICS 
AIR POWERED PUMP [VENTURI] DIAGNOSIS 11 
ACTUATOR TILTS AFTER STOPPING 12 
ADDITIONAL INFORMATION 14

TST-020 PT-AIR –REV. 2017-246 Page 1 of 14

SYMPTOMS OF VACUUM LEAK

A severe leak is evidenced by a lifter’s inability to draw full vacuum while attached to a clean,

smooth, nonporous surface. In such cases, the vacuum level shown on the vacuum gauges will be

less than 16" Hg [-54 kPa], the red zone of the vacuum gauge.

A moderate leak is indicated if the lifter loses more than 4" Hg [-13.5 kPa] in 5 minutes during a

vacuum test when the power is off. This amount of lost air is serious enough to warrant repairing

the lifter’s vacuum system.

DETERMINING LEAK EXISTENCE

To determine if lifter has a vacuum leak, perform the Vacuum Test as described in the Maintenance

section of lifter’s instruction manual.

During vacuum test it is recommended that you take notes on amount of air lost in time increments

(i.e. “Lost 5" Hg [-17 kPa] in 5 minutes”). This assists in diagnosing the location of the leak because

there may be more than one component leaking vacuum. For example, if an isolated section tests

positive for a leak but the leak rate is less than that of the whole lifter, then there is still one or more

vacuum leak elsewhere in the system.

ADDRESSING LEAK

If the leak is sufficient to warrant repair:

Locate the cause of leak beginning by inspecting the vacuum pads, fittings and hoses of the entire

vacuum system. Look for contamination, cuts or abrasions on pad faces, cracks in the pad suction

stem, cracks, abrasions or cuts in hoses, damaged fittings and loose hoses at connection points.

If leak is severe, the cause is often a visibly damaged part.

Caution: Do not apply soapy water to fittings or vacuum hoses in an attempt to find leaks, since it

will only be drawn inside the vacuum system.

If the leak’s source is not immediately evident, the various sections of the entire vacuum system

must be systematically isolated and tested to determine the leakage point. The process to

accomplish this is described in the tests to follow.

Note: The information gathered when performing a vacuum test is only valid if the tools used to

perform the test are accurate. Be sure that the tools used are capable of completely sealing the

isolated parts of the vacuum system when tested.

Recommended tools

: Plugs for hoses and fittings, ball valve with vacuum gauge attached,

appropriate hose adapters and extra vacuum hose.

If needed, test equipment is available from Wood’s Powr-Grip. Contact us for additional information.

Procedure assumes operator has access to appropriate tools

TST-020 PT-AIR –REV. 2017-246 Page 2 of 14

BASIC REPAIR TIPS

1) When removing a hose from a barbed fitting, avoid damaging the barbs of the fitting to which

the hose is attached. Cuts or nicks in fitting barbs can create a leak that did not previously

exist.

2) If a hose is removed from a barbed fitting, cut approximately 1/8" to 1/4" [3 to 6 mm] off the

end of the hose before reinstalling it on the fitting, in order to remove damaged hose ends.

Note: In release mode, the vacuum system of this lifter provides quick release using a “blow off”

feature, where air is pumped into the pad system for faster load release. When testing for leaks, it

is often necessary to seal off the system by capping off, plugging fittings and lines, or closing all

pad shut-offs. Due to this, the use of the release function is not recommended during the

repair process. Release mode will cause pressure to build in the sealed off section and may

damage components.

3) To release the lifter when testing with capped or closed off sections: Remove or open the item

used to close off the vacuum system. Do not use the lifter’s release mode.

TST-020 PT-AIR –REV. 2017-246 Page 3 of 14

PRELIMINARY TEST

Note: The following assumes operator has access to suitable plugs to seal off the section being

tested.

This test determines whether leakage is located in the vacuum generating system or the pad

system.

1) Remove the hose from the vacuum filter that attaches to the

vacuum pad system. Using a cap plug (1A) cap off the fitting

of the vacuum filter as shown in FIGURE 1.

Note: The size plug needed may vary with lifter model.

2) Repeat the vacuum test with the filter capped-off.

If the vacuum level of the lifter’s vacuum gauge holds

steady and does not drop, this indicates that the leak is

located in the vacuum pad system between the filter and

vacuum pads.

Proceed to Pad System Tests.

If the vacuum level of the lifter’s vacuum gauge starts

and continues to drop, this indicates that the leak is

located in the vacuum generating system.

Proceed to Vacuum Generating System Test.

FIGURE 1

TST-020 PT-AIR –REV. 2017-246 Page 4 of 14

VACUUM GENERATING SYSTEM TEST

Note: The following assumes operator has access to suitable plugs, a

ball valve with vacuum gauge, and additional hose and adapter fittings

for connecting the ball valve to the lifter’s vacuum lines and fittings.

The most likely leak points in the vacuum generating system are the

check valve, the filter, or the control valve. Leave the filter disconnected

(capped-off) from the pad system and test:

1) Isolate the check valve from the system.

The check valve (2A) is attached to the venturi assembly.

See FIGURE 2.

2) Remove the hose (2B) from the venturi assembly connected to the

fitting with the check valve.

Using the ball with vacuum gauge and appropriate hose adapters,

attach the ball valve (end with vacuum gauge attached) to the

fitting where the hose was removed. Attach the other end of the

ball valve to the hose that was removed from the fitting.

See FIGURE 3. 3) With ball valve in the open position (handle in-line

with valve), apply vacuum. When a sufficient level

of vacuum is reached, close the ball valve (turn

handle perpendicular to the valve) and close the air

supply valve to the venture air pump.

4) Observe both the lifter’s and ball valve’s vacuum

gauges:

If the vacuum level of the lifter’s vacuum gauge

starts and continues to drop, a leak is located in

either the vacuum filter or control valve assembly.

Proceed to step 5.

If the vacuum level of the ball valve’s vacuum

gauge starts and continues to drop, or if both the

vacuum gauges hold steady and do not drop, this

indicates that the check valve leaks.

Note: The check valve may leak intermittently, so

if both vacuum gauges hold steady and do not

drop, the check valve is indicated as the cause.

If the ball valve’s vacuum gauge did drop and

indicates a leak: Check the attached fittings and

line connecting to the vacuum tank for loose

connections or indication of damage or cracks to

the fittings or lines. If there is no visible damage

or neither vacuum gauge indicates a leak during

the test, replace the check valve.

FIGURE 2

FIGURE 3

TST-020 PT-AIR –REV. 2017-246 Page 5 of 14

If the vacuum level of both the lifter and ball valve’s vacuum gauges start and continue to

drop: The check valve leaks and needs to be replaced and there is a leak located in either

the filter or control valve assembly.

First, replace the check valve then proceed to step 5.

5) If it is determined that a leak exists in either

the filter or control valve assembly: Remove

the ball valve from the hose and reinstall it so

that the vacuum gauge is now in the line

connected to the control valve.

6) Remove the hose that connects the control

valve to the vacuum filter and cap off the

fitting (4A). See FIGURE 4.

7) With the ball valve in the open position

(handle in-line with the valve), apply vacuum.

When a sufficient level of vacuum is reached,

close the ball valve (turn handle

perpendicular to the valve) and close the air

supply valve to the venturi pump.

8) Observe the ball valve’s vacuum gauge:

If the vacuum level of the ball valve’s

vacuum gauge starts and continues to

drop: The control valve assembly is the source of the leak.

Examine the hose connection to the control valve and the fittings for any indications of loose

connections, cracks or damage. If there is no visible damage, replace the control valve.

If the vacuum level of the ball valve’s vacuum gauge holds steady and does not drop: The

vacuum filter is the cause.

Proceed to step 9.

FIGURE 4

TST-020 PT-AIR –REV. 2017-246 Page 6 of 14

9) To individually test the filter, leave the ball valve

connected to the venturi pump. Connect the end of the

ball valve connected to the control valve directly to the

hose of the vacuum filter assembly.

Cap off the fitting of the filter that was connected to the

vacuum pads if it is not capped-off. See FIGURE 5.

10) Move the handle of the control valve to the apply

position and open the air supply valve.

11) When a sufficient level of vacuum is reached, close the

ball valve and the air supply valve.

12) Observe the lifter’s vacuum gauge:

Based on the previous tests it is expected that the

vacuum level of the lifter’s vacuum gauge will start

and continue to drop, verifying that the vacuum filter

assembly does leak.

If confirmed, examine the hose connection to the

vacuum filter and the fittings for any indications of

loose connections, cracks or damage.

The twist drain plug located at the base of the filter

bowl should never be used when the filter is used on

a vacuum system.

Verify that the drain plug is tight and has not been

used. If the twist drain has been used it will need to

be removed and cleaned before reinstalling.

oRemove the filter bowl from the filter and remove

the plastic nut that attaches the drain plug to the

filter bowl.

oRemove the drain plug and the O-ring located in

the bottom of the filter bowl.

oClean out the bottom of the filter bowl where the

O-ring is located.

oClean the O-ring and apply a light film of rubber compatible grease.

oReinstall the drain plug and secure it with the retaining nut.

Note: Do not over-tighten the retaining nut; this is a plastic nut and part. It is the O-ring that

creates the seal to the bowl.

Service the filter according to the lifter’s maintenance instructions, giving particular attention to the

O-ring located between the filter bowl and body.

Re-test the filter assembly.

If the leak continues, replace the filter.

Repair or replace any parts identified to leak and repeat the Preliminary Test.

FIGURE 5

TST-020 PT-AIR –REV. 2017-246 Page 7 of 14

Once the vacuum generating system is confirmed to hold (no significant leaks noted per the

vacuum readings), re-connect the pad system, proceed to system confirmation and retest the

vacuum system as described.

Indice

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