11
MATWELD, INC. PHONE:(270) 444-0085 FAX:(270) 443-6180
Matweld reserves the right to change parts, features, or specifications without notice.
11/99
REVIEW OF HYDRAULIC PRINCIPLES
A. TOOL CIRCUIT
1. HYDRAULIC FORMULAS:
CID X RPM GPM X PSI
GPM =
231
HP = 1714 (.85)
1456.9
Example: HP required to deliver 10 GPM at 1500 PSI.
10 GPM X 1500 PSI = 15000 = 10.3 HP
1456.9
1456.9
(subtract back pressure for tool HP)
Estimated HP delivered by pump or used by tool.
PSI
GPM
500
1,000
1,500
2,000
2,500
3,000
3
1.03
2.06
3.09
4.12
5.15
6.18
5
1.72
3.43
5.15
6.86
8.58
10.30
10
3.43
6.86
10.3
13.70
17.20
20.60
15
5.15
10.30
15.40
20.60
25.70
30.90
2. BACK PRESSURE
BACK PRESSURE MEASURED AT THE TOOL RETURN PORT MUST NOT EXCEED THE MANU-
FACTURERS BACK PRESSURE RATING. MOST MANUFACTURERS LIST THE MAXIMUM BACK
PRESSURE FOR THEIR HYDRAULIC TOOLS AT 250 PSI. BACK PRESSURE MEASURED ON THE
RETURN SIDE OF THE TOOL IS THE FORCE REQUIRED TO GET THE OIL BACK TO THE TANK.
IN ALMOST ALL CASES THE LOWER THE BACK PRESSURE THE BETTER THE TOOL PERFOR-
MANCE. FIRST, THE BACK PRESSURE IS SUBTRACTED FROM THE MAXIMUM TOOL PRES-
SURE TO ARRIVE AT A MAXIMUM TOOL OPERATING PRESSURE. FOR EXAMPLE, TOOLS WITH
2000 PSI OPERATING PRESSURE ARE INSTALLED ON A SYSTEM WITH 250 PSI BACK PRES-
SURE. THIS LEAVES1750 PSI AS A MAXIMUM TOOL PRESSURE. IMAGINE A SYSTEM WITH 500
PSI BACK PRESSURE. 2000 MINUS 500 PSI BACK PRESSURE LEAVES ONLY 1500 PSI FOR THE
TOOL. SECOND, TOOLS ARE DESIGNED FOR PRESSURE TO BUILD ON THE PRESSURE SIDE
OF THE TOOL. IF TOO MUCH PRESSURE BUILDS ON THE RETURN SIDE, NOT ONLY IS PER-
FORMANCE EFFECTED, BUT SEALS MAY BLOW. THIS IS WHY IT IS VERY IMPORTANT TO
DIRECT THE FLOW INTO THE TOOL CORRECTLY. REVERSING THE HOSES TO TEST MAY
RESULT IN BLOWN SEALS, DAMAGE TO THE TOOL, AND PERSONAL INJURY.
REV.8/04