DEMOLITION GRAB
INSTRUCTION MANUAL
MODELS:
DG16
DG20
DG30
DG40
“Use Genuine NPK Parts”
7550 Independence Drive
Walton Hills, OH 44146-5541
Phone (440) 232-7900
Toll-free (800) 225-4379
Fax (440) 232-6294
© Copyright 2018 NPK Construction Equipment, Inc. www.npkce.com DG000-9600A
DG16,DG20,DG30,DG40 Demolition Grab Instruction Manual 6-18
1
CONTENTS
CONTENTS .............................................................................................................................................. 1
SAFETY .................................................................................................................................................... 3
OPERATION ...................................................................................................................................... 4
MAINTENANCE ................................................................................................................................. 5
INTRODUCTION ....................................................................................................................................... 7
EXCAVATOR COMPATIBILITY ................................................................................................................. 7
SERIAL NUMBER LOCATION .................................................................................................................. 8
SPECIFICATIONS ..................................................................................................................................... 9
DG16 ................................................................................................................................................. 9
DG20 ................................................................................................................................................. 10
DG30 ................................................................................................................................................. 11
DG40 ................................................................................................................................................. 12
HYDRAULIC INSTALLATION .................................................................................................................... 13
HYDRAULIC LINES ........................................................................................................................... 13
SHUT-OFF VALVES .......................................................................................................................... 13
PORT CONNECTION DIAGRAM ....................................................................................................... 14
DEMOLITION GRAB HYDRAULIC CIRCUITS ........................................................................................... 15
MOUNTING INSTALLATION ..................................................................................................................... 18
MOUNTING TO THE EXCAVATOR ................................................................................................... 19
REMOVAL FROM THE CARRIER ..................................................................................................... 19
STORAGE OF DEMOLITION GRAB ......................................................................................................... 19
OPERATING INSTRUCTIONS .................................................................................................................. 20
OPERATING TECHNIQUES AND PRECAUTIONS............................................................................ 22
GENERAL MAINTENANCE ....................................................................................................................... 25
DAILY INSPECTION AND MAINTENANCE ....................................................................................... 25
ARM MAINTENANCE ........................................................................................................................ 26
FRAME MAINTENANCE .................................................................................................................... 26
FRAME CRACK REPAIR ................................................................................................................... 26
LUBRICATION POINTS ..................................................................................................................... 27
SLEWING RING INSPECTION AND MAINTENANCE ............................................................................... 28
MEASURING MAXIMUM AXIAL MOVEMENT ................................................................................... 28
NPK ASSEMBLY LUBRICANT .................................................................................................................. 29
ROTARY JOINT MAINTENANCE .............................................................................................................. 30
HYDRAULIC ROTARY JOINT ASSEMBLY ........................................................................................ 30
LEAKAGE OF THE SEALS ................................................................................................................ 30
TESTING THE ROTARY JOINT SEALS FOR INTERNAL LEAKAGE ................................................. 30
REPLACEMENT OF THE SEALS IN THE ROTARY JOINT ............................................................... 31
TROUBLESHOOTING ............................................................................................................................... 35
DETERMINE THE TYPE OF PROBLEM ............................................................................................ 35
MEASURING OPERATING PRESSURES ......................................................................................... 35
RELIEF VALVE CHECKING AND SETTING PROCEDURE ............................................................... 35
COUNTERBALANCE VALVE LOCATION .......................................................................................... 37
TROUBLESHOOTING CHART FOR LOW POWER ........................................................................... 38
CHECKING HYDRAULIC FLOW AT RATED PRESSURE ................................................................. 39
PROCEDURE FOR CHECKING HYDRAULIC FLOW AT RATED PRESSURE .................................. 39
TROUBLESHOOTING CHART FOR SLOW CYLINDER SPEED ....................................................... 41
JAW DRIFT........................................................................................................................................ 41
TO DETERMINE IF THE JAW DRIFT IS OCCURING FROM A BAD CYLINDER OR THE CARRIER. 41
ROTATION ........................................................................................................................................ 42
MEASURING ROTATION PRESSURES ............................................................................................ 42
ROTATION PRESSURE CHECKING PROCEDURE .......................................................................... 43
TROUBLESHOOTING CHART FOR ROTATION ............................................................................... 43
FASTENER TORQUE CHART .................................................................................................................. 45
CYLINDER TORQUE SPECIFICATIONS .................................................................................................. 47
ROD NUT AND PISTON TORQUES .................................................................................................. 47
CONVERT FROM DUAL MOTOR TO SINGLE MOTOR (DG20, DG30, DG40).......................................... 48
2
CONTENTS
WARRANTY STATEMENTS ..................................................................................................................... 49
KEYWORDS FOR COMMON DEMO GRAB COMPONENTS .................................................................... 51
NOTES...................................................................................................................................................... 52
SERVICE RECORD .................................................................................................................................. 52
3
SAFETY
Safety notices in NPK Instruction Manuals follow ISO and ANSI standards for
safety warnings:
DANGER (red) notices indicate an imminently hazardous
situation which, if not avoided, will result in death or
serious injury.
WARNING (orange) notices indicate a potentially hazardous
situation which, if not avoided, could result in death or
serious injury.
CAUTION (yellow) notices indicate a potentially hazardous
situation, which, if not avoided, may result in minor or
moderate injury.
ATTENTION (blue) notices in NPK Instruction Manuals are
an NPK standard to alert the reader to situations which, if not avoided, could result in
equipment damage.
WARNING – FALLING OR FLYING DEBRIS decals are
included with each NPK Demolition Grab Attachment. The
decal (part number H100-7210) must be installed in the cab,
visible to the operator.
WARNING – STAY CLEAR decal (part number H100-7200)
is installed on all NPK Demolition Grab Attachment. Keep
them clean and visible. NPK will provide decals free of
charge as needed.
4
Warning Decal for Cab Installation
SAFETY
OPERATION
1. Operator personnel must read and understand the NPK INSTRUCTION MANUAL
to prevent serious or fatal injury.
2. FLYING OR FALLING DEBRIS CAN CAUSE SERIOUS OR FATAL INJURY.
Keep personnel and bystanders clear of the DEMOLITION GRAB while in
operation.
3. Do not operate DEMOLITION GRAB without an
impact resistant shield between the DEMOLITION
GRAB and operator. Operate with extreme caution
near walls or columns that may collapse and near
concrete debris that may fall.
4. Operate the DEMOLITION GRAB from the
operator’s seat only.
5. Use two people whenever operator visibility is
limited, one to operate the DEMOLITION GRAB,
the other to guide operations.
6. Do not leave a load suspended in air.
7. Do not pass a load over people, vehicles, etc.
8. Do not operate the DEMOLITION GRAB within
reach of power lines.
9. Do not climb, sit, or ride on the DEMOLITION
GRAB.
10. Match the DEMOLITION GRAB size to excavator according to NPK
recommendations, see page 7. The excavator must be stable during DEMOLITION
GRAB operation and during transport.
11. Do not operate without inspection (access) covers in place.
12. Be especially cautious around hydraulic lines. Hydraulic oil can be extremely HOT!
Avoid skin contact with hydraulic oil. It can cause severe burns!
13. Protect hands and body from hydraulic fluids under pressure. Escaping high
pressure fluid can penetrate the skin, causing serious injury. Avoid the hazard by
relieving pressure before disconnecting any lines. Search for leaks with a piece of
cardboard, or other object. If an accident occurs, see a doctor immediately!
Hydraulic fluid injected into the skin must be surgically removed immediately
or gangrene may result!
14. Make daily visual inspections of all fasteners, boom pins, hoses, etc.
15. When removing or installing mounting pins, beware of flying metal chips.
5
SAFETY
MAINTENANCE
1. Use only NPK supplied replacement parts. NPK specifically disclaims any
responsibility for bodily injury or DEMOLITION GRAB damage that results from the
use of parts not sold or approved by NPK.
2. Use extreme caution in handling. A fully assembled DEMOLITION GRAB can
weigh over 2 tons. Sub-assemblies range in weight from hundreds to thousands of
pounds. To avoid bodily harm, use lifting and securing mechanisms of adequate
capacity to support loads. Seek the aid of an assistant as much as possible, and
always when handling heavier sub-assemblies.
3. The supplied safety bar (t79) MUST always be installed during transport, repairs,
dismounting and mounting to the carrier, changing the cutters and all other routines
at the attachment (GZ).
4. Wear safety glasses and protective clothing when working on the DEMOLITION
GRAB. Wear thermal-protective gloves when handling heated parts.
5. Prevent exposure to hazardous fumes. Remove all paint, grease, and oil before
heating, cutting or welding on the DEMOLITION GRAB.
6. Be especially cautious around hydraulic lines. Hydraulic oil can be extremely HOT!
Avoid skin contact with hydraulic oil. It can cause severe burns!
7. Protect hands and body from hydraulic fluids under pressure. Escaping fluid
under pressure can penetrate the skin, causing serious injury. Avoid the hazard by
relieving pressure before disconnecting any lines. Search for leaks with a piece of
cardboard, or other object. If an accident occurs, see a doctor immediately!
Hydraulic fluid injected into the skin must be surgically removed within a few
hours or gangrene may result.
8. When removing or installing mounting pins, beware of flying metal chips.
6
SAFETY
MAINTENANCE
STANDARD PRACTICES
Maintenance of and repairs to the DEMOLITION GRAB should be performed by an
experienced service technician, thoroughly familiar with all standard practices and
procedures, and most importantly, all safety precautions. The following is a review of
common standard practices to be followed when working with hydraulic equipment, and
is not meant to be all-inclusive. Rather, this review is presented as a reminder as to
some of the unique characteristics of hydraulic equipment.
The prevention of foreign contaminant damage is critical when working with
hydraulic equipment. Protect exposed holes and parts to guard against entry of
contaminants. Install metal or plastic plugs/caps where applicable to prevent entry
of debris into the hydraulic system.
Mark the location and position of mating parts as an aid to re-assembly. Mark
corresponding parts uniquely to reflect their relationship, including proper location,
position, orientation, and/or alignment.
DO:
During assembly, observe all markings made during disassembly, and all
corresponding features of mating parts to ensure proper location, position,
orientation, and alignment.
During disassembly of a sub-assembly, place removed components on a clean, dry
surface, in proper relative position as an aid in re-assembly.
Always inspect threaded areas on components. Repair or replace as required.
Never apply uncured thread adhesive to a fastener that has cured adhesive on it.
Clean the fastener and the threaded bore. A tap and die may be helpful for this task.
Be sure to remove loose debris from the threaded bore.
Use care to avoid scratches, nicks, dents, or other damage to machined surfaces of
mating components.
When securing a component, always tighten cap screws gradually in an opposing
pattern, applying the specified torque.
Grease can be used to temporarily hold a part in place while the abutting part is
placed into position.
Always use common sense and exercise standard safety precautions when working
with all tools and equipment required to maintain, repair or troubleshoot the
DEMOLITION GRAB.
ATTENTION
7
INTRODUCTION
NPK prides itself on the design and manufacture of high quality products. This tradition
of quality workmanship and materials continues in our DEMOLITION GRABS. Many
years of productive service can be realized with proper operation and care of the
DEMOLITION GRAB.
The purpose of this manual is to provide you with the information and instructions
required to properly operate and maintain the DEMOLITION GRAB. This will result in
maximum DEMOLITION GRAB reliability and productivity.
Read this manual thoroughly before attempting to operate, remove, disassemble,
repair or troubleshoot the DEMOLITION GRAB or any of its components.
Follow all the safety precautions contained in this manual. Failure to do so, can
result in death, personal injury, injury to others, and property damage.
EXCAVATOR COMPATIBILITY
These excavator weight ranges are intended as a guideline only. Other factors, such as
stick length, counterweights, undercarriage, etc., must be taken into consideration.
Mounting a DEMOLITION GRAB that is too heavy for the excavator can be dangerous
and damage the machine. Verify excavator stability with the DEMOLITION GRAB
before transport or operation.
Mounting a DEMOLITION GRAB that is too small for the excavator can damage the
DEMOLITION GRAB and void Warranties. Please consult NPK Engineering for specific
detailed information.
MODEL
RECOMMENDED EXCAVATOR
CLASS
3rd member mounting
US ton
(Metric ton)
DG-16
11 – 17.5
(10 - 16)
DG-20
15 - 22
(14 - 20)
DG-30
20 - 33
(18 - 30)
DG-40
27 - 44
(25 - 40)
8
SERIAL NUMBER LOCATION
DG16, DG20, DG30, DG40
sn2 – serial number tag
9
SPECIFICATIONS
DG16
MODEL
WEIGHT
CLOSING
CAPACITY
MAXIMUM
FORCE
(volume)
HOIST LOAD
lbs.
(kg)
ton
(kN)
cu. yd.
(liter)
lbs.
(kg)
DG16
1,895
(860)
4.8
(48)
.55
(425)
7,716
(3,500)
ROTATION:
Rotation is 360°
MODEL
OIL FLOW
PRESSURE
MAIN JAWS
MAIN JAWS
gpm
(lpm)
psi
(bar)
DG16
16 - 26
(60 - 100)
3,625 - 5,100
(250 - 350)
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG16
5 - 8
(20 - 30)
1,450 - 2,030
(100 - 140)
NOTE: Specifications subject to change without notice.
10
SPECIFICATIONS
DG20
MODEL
WEIGHT
CLOSING
CAPACITY
MAXIMUM
FORCE
(volume)
HOIST LOAD
lbs.
(kg)
ton
(kN)
cu. yd.
(liter)
lbs.
(kg)
DG20
2,535
(1,150)
5.2
(52)
.65
(500)
9,920
(4,500)
ROTATION:
Rotation is 360°
MODEL
OIL FLOW
PRESSURE
MAIN JAWS
MAIN JAWS
gpm
(lpm)
psi
(bar)
DG-20
16 - 26
(60 - 100)
3,625 - 5,100
(250 - 350)
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG-20
9 - 16
(35 - 60)
1,450 - 2,030
(100 - 140)
OPTIONAL SINGLE MOTOR
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG-20
5 - 8
(20 - 30)
1,450 - 2,030
(100 - 140)
NOTE: Specifications subject to change without notice.
11
SPECIFICATIONS
DG30
MODEL
WEIGHT
CLOSING
CAPACITY
MAXIMUM
FORCE
(volume)
HOIST LOAD
lbs.
(kg)
ton
(kN)
cu. yd.
(liter)
lbs.
(kg)
DG30
3,858
(1,750)
7.2
(72)
1.05
(800)
12,125
(5,500)
ROTATION:
Rotation is 360°
MODEL
OIL FLOW
PRESSURE
MAIN JAWS
MAIN JAWS
gpm
(lpm)
psi
(bar)
DG-30
21 - 32
(80 - 120)
3,625 - 5,100
(250 - 350)
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG-30
9 - 16
(35 - 60)
1,450 - 2,030
(100 - 140)
OPTIONAL SINGLE MOTOR
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG-30
5 - 8
(20 - 30)
1,450 - 2,030
(100 - 140)
NOTE: Specifications subject to change without notice.
12
SPECIFICATIONS
DG40
MODEL
WEIGHT
CLOSING
CAPACITY
MAXIMUM
FORCE
(volume)
HOIST LOAD
lbs.
(kg)
ton
(kN)
cu. yd.
(liter)
lbs.
(kg)
DG40
4,519
(2,050)
7.2
(72)
1.18
(900)
12,125
(5,500)
ROTATION:
Rotation is 360°
MODEL
OIL FLOW
PRESSURE
MAIN JAWS
MAIN JAWS
gpm
(lpm)
psi
(bar)
DG-40
21 - 32
(80 - 120)
3,625 - 5,100
(250 - 350)
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG-40
9 - 16
(35 - 60)
1,450 - 2,030
(100 - 140)
OPTIONAL SINGLE MOTOR
MODEL
OIL FLOW
PRESSURE
ROTATION
ROTATION
gpm
(lpm)
psi
(bar)
DG-40
5 - 8
(20 - 30)
1,450 - 2,030
(100 - 140)
NOTE: Specifications subject to change without notice.
13
HYDRAULIC INSTALLATION
NPK Hydraulic Installation Kits are available for virtually all compatible excavator
models. The kits include all parts and complete instructions for the hydraulic
installation, including valving and/or controls, hoses and fittings, boom and stick tubing,
and clamps.
See your NPK dealer for details or call NPK at 1-800-225-4379.
HYDRAULIC LINES
Typically, the pressure line to close is arranged on the left side of the boom and the
open line is on the right side.
SHUT-OFF VALVES
Most NPK Hydraulic Installation Kits use two shut-off valves (k4) on the dipper stick (k1)
of the carrier. These valves control the hydraulic oil going to the close side (m3) and
the open side (m4) from the Demo Grab attachment.
Pressure test ports (k8) are located in the shut-off valves. Each shut-off valve has an
“ON” (k5) and an “OFF” (k6) position.
14
HYDRAULIC INSTALLATION
PORT CONNECTION DIAGRAM
m3
HOSE: arm close
m4
HOSE: arm open
m39a
ROTATION HOSE: for clockwise movement
m39b
ROTATION HOSE: for counter-clockwise movement
MODEL
OPEN/CLOSE
ROTATION
DG16
12 JIC
8 JIC
DG20
12 JIC
8 JIC
DG30
12 JIC
8 JIC
DG40
12 JIC
8 JIC
15
DEMOLITION GRAB HYDRAULIC CIRCUITS
CYLINDER HYDRAULIC CIRCUIT
BN
ROTARY JOINT ASSEMBLY
c11
CYLINDER
cb1
COUNTERBALANCE VALVE
m3
ARM CLOSE PORT
m4
ARM OPEN PORT
16
DEMOLITION GRAB HYDRAULIC CIRCUITS
SINGLE MOTOR HYDRAULIC CIRCUIT
BQ4
HYDRAULIC MOTOR
fr
FLOW REGULATOR
ma4
CROSS PORT RELIEF
m39a
CLOCKWISE ROTATION PORT
m39b
COUNTER-CLOCKWISE ROTATION PORT
17
DEMOLITION GRAB HYDRAULIC CIRCUITS
DUAL MOTOR HYDRAULIC CIRCUIT
BQ4
HYDRAULIC MOTOR
ma4
CROSS PORT RELIEF
m39a
CLOCKWISE ROTATION PORT
m39b
COUNTER-CLOCKWISE ROTATION PORT
18
MOUNTING INSTALLATION
NPK Mounting Installation Kits include the parts required to adapt the NPK Demolition
Grab to the stick or arm of the excavator. The kits include all necessary stick and link
pins, bolts, etc.
m1
STICK PIN (optional)
m2
LINK PIN (optional)
m3
WHIP HOSE - CLOSE
(optional)
m4
WHIP HOSE - OPEN
(optional)
m7
TOP BRACKET
m11
BRACKET BOLT
m12
HEX NUT
m13
WASHER
m27
SWIVEL TOP
m39
ROTATION HOSE
(optional)
m42
HEX NUT
m43
PIN BOLT
19
MOUNTING INSTALLATION
MOUNTING TO THE EXCAVATOR
1. Position the Demolition Grab on wood blocks (t20) as shown.
2. Align the stick pin bore (m24). Install the stick pin (m1).
3. Align the link pin bore (m25). Install the link pin (m2).
4. Clean away any dirt found on the hose connections, connect the whip hoses (m3
and m4) and the rotation hoses (m39).
5. Open the shut off valves (k4).
6. Remove safety bar.
REMOVAL FROM THE CARRIER
1. Retract the cylinder to open jaws fully.
2. Position the Demolition Grab horizontal on wood blocks (t20), as shown above.
3. Install safety bar.
4. Close the shut-off valves.
5. Shut off engine and relieve all hydraulic pressure.
6. Disconnect the hydraulic hoses before setting the Demolition Grab down. Install
plugs in the hydraulic hoses and caps on the stick tubes to keep out contamination.
STORAGE OF DEMOLITION GRAB
1. Make sure the hydraulic hoses are plugged and stick tubes capped.
2. Grease all lubrication points, see page 27.
3. If stored outdoors, cover with waterproof tarp.
The hydraulic lines must be handled carefully to
prevent contamination from entering the
Demolition Grab or the carrier hydraulic system.
ATTENTION
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