Eaton Electrical Heat Pump PVE12 User Manual
Vickers®  
Piston Pumps  
Overhaul Manual  
PVE Variable Pump  
12–21 USgpm capacity at 1800 rpm  
Released 8/1/90  
M-2854-S  
 
Section I – Introduction  
A. Purpose Of Manual  
Model  
Series  
Parts  
Drawing  
Installation  
Drawing  
_____  
This manual describes operational characteristics and  
overhaul information for the PVE12, 19(*) and the  
PVE21(*)–** variable displacement piston pumps. The  
information contained herein pertains to the latest design  
series as listed in Table 1.  
M-2853-G  
PVE12  
PVE19  
PVE21  
M-2841-S  
322C  
Table 1.  
B. General Information  
2. Model Codes - Variations within each basic model  
series are covered in the model code. Table 2 shows a  
complete breakdown of the model codes covering these  
units. Service inquiries should always include the complete  
model code number as stamped on the mounting flange.  
1. Related Publications - Service parts information  
and installation dimensions are not contained in this  
manual. The parts and installation drawings listed in  
Table 1 are available from authorized distributors or sales  
engineers.  
1
3
4
5
6
7
8
9
10  
11  
12  
2
1
2
3
Pump, Variable Displacement,  
Inline Piston, E-Series  
9
Design  
10  
Control Options (Con’t)  
(** = Pressure setting in tens of bars)  
CC** - Same as C** except with  
max. adj. stop.  
CG**- Pressure compensation with  
remote control (see C**)  
Electric dual range com-  
CD - pensation  
10  
Control Options  
(** = Pressure setting in tens of bars)  
Flow Rating  
USgpm @ 1800 rpm  
C** –  
Pressure compensator  
Max. setting 207 bar  
(3000 psi)  
Shaft Rotation  
Range 02-21 bar  
(Viewed from shaft end)  
R – Right hand (clockwise)  
L – Left hand (counterclockwise)  
Same as CD except with  
CCD - max. adj. stop  
C**VP** – Pressure & load sensing  
Pressure compensating  
(see C**)  
Load sensing (see CV**)  
C**VPC** –Pressure and load sensing  
Pressure compensating  
(see C**)  
11  
12  
Control Bleed Down  
Blank – C, CC, CG, CD, CCD  
B – Bleed down orifice (CVP & CVPC)  
P – Plug (no orifice) (CVP & CVPC)  
4
Noise Level Rating  
Blank – Standard Unit  
Q – Industrial Quieter  
1800 rpm @ 207 bar (3000 psi)  
Load setting 24 bar  
(350 psi)  
Control Design  
Range 17-31 bar  
(251-450 psi)  
C**VPD** –Pressure & load sensing  
Pressure compensating  
(see C**)  
5
6
Mounting Flange  
B – SAE B 2 bolt  
Input Shaft Type  
1 – SAE B Straight keyed  
2 – SAE B Splined  
Load setting 41 bar  
(600 psi)  
Range 32-45 bar  
(451-650 psi)  
Same as C** except with  
max. adj. stop.  
Pressure compensation  
with remote control  
(see C**)  
Electric dual range com-  
pensation  
Same as CD except with  
max. adj. stop  
7
8
Port Configuration  
E – End ported, SAE O-ring  
M – End ported, metric O-ring  
(per ISO 6149)  
Shaft Seal  
S – Standard shaft seal  
N – No shaft seal  
Table 2. Model Code Breakdown  
3
 
 
1
3
4
5
6
2
6
7
8
7
8
Control Design  
1
2
Control Options  
(** = Pressure setting in tens of bars)  
Pump, Variable Displacement,  
Inline Piston, E–Series  
C-10 –  
Pressure compensated  
(PVE19, 250-3000 psi)  
(PVE21, 250-2700 psi)  
Flow Rating  
Special Suffix  
USgpm @ 1800 rpm  
19 – 19 USgpm  
21 – 21 USgpm  
CG-10 – Remote control pressure  
compensator adjustable  
from 350-3000 psi using  
and external relief valve.  
Load sensing PVE19/21  
3
4
Shaft Rotation  
CV-10 –  
(Viewed from shaft end)  
R – Right hand (clockwise)  
L – Left hand (counterclockwise)  
CVP-12 – Load sensing (160 psid)  
with pressure compensation  
PVE 19/21  
CVPC-12 –Load sensing (350 psid)  
with pressure compensation  
PVE 19/21  
Input Shaft Type  
1 – SAE B Straight keyed  
2 – SAE B 15 tooth splined  
9 – SAE B 13 tooth spline  
5
Pump Design  
Table 2. Model Code Breakdown (Con’t)  
4
 
Housing  
Yoke  
Compensator  
Shaft  
Seal  
Shaft  
Valve Block  
Piston  
Bearing  
PVE12 Section View  
Wafer Plate  
Yoke  
Compensator  
Tapered  
Roller  
Bearing  
Drive  
Shaft  
Housing  
Rotating Group  
PVE19 Section View  
Figure 1. Sectional Views of the PVE Pumps  
5
 
Section II – Description  
4. Compensator (CVP), (Load Sensing Pressure  
Limiting Type): The CVP control is a combination of the  
standard flat cut-off compensator (C) and the load sensing  
compensator (CV). The load sensing compensator controls  
flow to the load across an external valve orifice. If pressure  
build–up exceeds the flat cut-off compensator setting, the flat  
cut-off compensator overrides the load sensing compensator  
and lowers the flow to prevent excessive pressure build-up  
at the pump.  
A. General  
Assembly of a typical pump package is shown in Figure 1.  
Six types of compensator subassemblies are used with the  
PVE series pumps. Refer to Section III for principles of  
operation. See Model Code for pressure settings.  
1. Compensator (C), (Flat Cut-Off Type): A pump using  
this compensator will maintain a constant load pressure for  
all values of flow within the capacity of the pump.  
5. Compensator (CVPC), (Load Sensing Pressure  
Limiting Type): This compensator is the same as the “CVP”  
compensator except the load sensing spring is heavier. The  
heavier spring provides a slightly higher pressure differential  
(160nP vs. 350nP) across the external valve orifice. See  
Figure 5.  
2. Compensator (CG), (Remote Control Type): This  
compensator is similar to the “C” type compensator except  
the compensator is controlled by a remote hydraulic source  
such as a relief valve.  
3. Compensator (CV), (Load Sensing Type): A load  
sensing compensator provides flow at a pressure equal to  
that required by the load plus a constant value used as a  
pressure drop across a metering valve. The pump will  
change its flow with changes in size of the metering valve  
orifice. The pump and compensator together provide a  
constant flow source for the load, at a pressure established  
by the requirements of the load, hence the title “Load  
Sensing”.  
6. Compensator (CVPD), (Load Sensing, Pressure  
Limiting Type): Same as “CVPC” except with higher  
pressures.  
B. Application  
Pump ratings in USgpm as shown in the model coding are at  
1800 rpm. For ratings at other speeds, methods of installa-  
tion and other application information, contact an authorized  
distributor or sales engineer.  
CAUTION  
A relief valve must be provided in the external circuit  
to prevent excessive pressure build up at the pump.  
Wafer Plate  
Shoe Plate  
Yoke Face  
Outlet Wafer Plate  
Kidney Slot  
Piston  
Outlet Port  
Inlet Port  
Drive Shaft  
Cylinder  
Block Bore  
Intake Kidney  
Slot Area  
Figure 2.  
6
 
 
Section III – Principles of Operation  
Pump outlet flow is proportional to the control range from  
A. Piston Pump  
cracking pressure to deadhead pressure. (i.e. If cracking  
pressure is 2900 PSI (max. flow) and deadhead pressure is  
3000 PSI (min. flow), a pressure of 2950 PSI would be equal  
to 1/2 maximum flow.)  
Rotation of the pump drive shaft causes the cylinder block,  
shoe plate and pistons to rotate. See Figure 2. The piston  
shoes are held against the yoke face by the shoe plate. The  
angle of the yoke face imparts a reciprocating motion to  
each piston within the cylinder block. Inlet and outlet ports  
connect to a kidney slotted wafer plate. As the pistons move  
out of the cylinder block, a vacuum is created and fluid is  
forced into the void by atmospheric pressure. The fluid  
moves with the cylinder block past the intake kidney slot to  
the outlet (pressure) kidney slot. The motion of the piston  
reverses and fluid is pushed out the cylinder block into the  
outlet port.  
If the load decreases, pressure will decrease proportionally  
and the compensator spring will move the spool down,  
opening the yoke stroking piston to case drain. As fluid is  
metered from the yoke stroking piston, the yoke spring will  
stroke the yoke to increase flow. The increase in flow causes  
a proportional increase in system pressure. The increase in  
system pressure returns the compensator spool to a null  
position and flow from the yoke stroking position will stop;  
simultaneously, movement of the yoke will stop. The flow will  
stay constant until another change of load occurs.  
B. Compensator (Flat Cut-Off Type)  
A flat cut-off compensated pump will maintain a constant  
load pressure for all values of flow within the capacity of the  
pump providing the load is sufficient to build up pressure.  
If the load continues to decrease, pump flow will continue too  
increase, holding the outlet at compensator cracking  
pressure. When maximum flow is reached (max. stroke), a  
maximum flow and a maximum pressure condition exists. A  
further decrease in load will lower the outlet pressure until a  
final theoretical condition of maximum flow and zero  
pressure is obtained.  
A step by step description of the flat cut-off type compensa-  
tor control follows. Refer to Figure 3 throughout this  
discussion.  
C. Compensator (Remote Control - “CG”)  
When a no load condition exists, the pump will deliver  
maximum flow at zero pressure. As the actuator load  
increases, pressure will rise; however, flow will remain at  
maximum until pressure reaches the compensator spring  
setting (cracking pressure). As a further increase in load  
occurs, system pressure will cause the compensator spool to  
move against the compensator spring, metering flow to the  
yoke stroking piston. The yoke stroking piston then moves the  
yoke to reduce flow. As flow is reduced, system pressure  
reduces slightly causing the compensator spool to return to the  
null position. At null, flow to the yoke stroking piston stops.  
Movement of the yoke will stop and the flow will stabilize at a  
reduce value. If the load were to continue to increase, the  
pump flow will reduce to zero (0) and a deadhead pressure  
condition would exist. The pressure differential needed to  
cause the compensator spool to change from maximum flow  
(cracking pressure) to zero flow (deadhead pressure) is  
approximately 50 to 150 PSI.  
This compensator allows the operator to change the  
pressure setting through the use of a remote control valve.  
The “CG” compensator has the same performance  
characteristics as the “C” type compensator.  
7
 
 
Cross Hole (Open to  
Spring Area)  
Compensator Spring  
Pump Load  
Drain  
Yoke Spring  
Yoke Stroking Piston  
Compensator Spool  
Outlet  
Inlet  
Rotating Group  
Figure 3. Flat Cut-Off Compensator  
D. Compensator  
CAUTION  
(Load Sensing Type - “CV”)  
Application  
A relief valve must be used to prevent outlet pres-  
sure from exceeding pump ratings if the load is  
excessive.  
A frequent application of pressure compensator pumps is to  
supply sevo valves or mechanically operated metering  
valves, whose function is to control flow to a hydraulic  
actuator (cylinder or motor).  
Minimum Pump Pressure  
In such circuits it is often desirable that flow be proportional  
only to an external valve spool position. This requires a  
constant pressure drop across the external valve. (NOTE:  
Flow through a valve varies with pressure drop as well as  
with valve spool position.)  
The minimum outlet pressure developed by the pump (no  
load) is a function of the compensator spring force versus  
the yoke spring force, whichever is greater. (Please note that  
external valve spool position (orifice size), has nothing to do  
with the minimum outlet pressure of the pump). The orifice  
size controls pump rate of flow only. The minimum outlet  
pressure will be constant for all settings of the valve spool  
orifice and is considered the pressure drop across the orifice  
(nP).  
Pumps incorporating the load sensing feature have a  
constant flow characteristic: Flow is constant regardless of  
the load pressure.  
8
 
Actuator  
Load  
External Valve  
Spool Orifice  
Compensator Spring  
(nP-Pressure Drop)  
Drain  
Yoke Spring  
Yoke Stroking Piston  
Compensator Spool  
Outlet  
Relief  
Valve  
Rotating Group  
Inlet  
Figure 4. Load Sensing Compensator (CV).  
External Valve Spool Orifice Size Reduced  
Circuit Operation At Minimum Pressure  
Refer to Figure 4 during the following description. Assume a  
no load condition.  
If the external valve spool orifice is reduced in size, pressure  
at the pump outlet will rise proportionally causing the  
compensator spool to move against the compensator spring.  
When the compensator spool moves far enough to open the  
yoke stroking piston to pump outlet pressure, the yoke  
stroking piston will move the yoke to a lower flow setting.  
The pump load consists of the pressure drop across the  
valve spool orifice (nP), plus the pressure developed by the  
work being performed at the actuator. (In this case the  
actuator is unloaded and only the pressure drop across the  
valve spool orifice (nP) will be considered.)  
The compensator senses pressure at the downstream side  
of the external valve spool orifice and compares this  
pressure to the pump outlet pressure. The compensator then  
adjusts the yoke to a flow which holds a constant pressure  
drop (nP) across the external valve spool orifice.  
Flow is restricted through the valve spool orifice and  
develops a pressure at the outlet of the pump. This pressure  
is applied to the lower end of the compensator spool. Initially,  
the compensator spring is holding the spool in the down  
position and the yoke is at maximum delivery position. When  
the pump is started, the increasing flow increases pressure  
at the lower end of the compensator spool and the  
compensator spool opens pressure to the yoke stroking  
piston. The yoke then strokes to a lower flow, lowering the  
pressure drop across the external valve orifice. When  
pressure reaches nP, the compensator spool will null. At this  
time, the stroking piston will remain stable until the external  
valve spool orifice is changed. (See Figure 4.)  
The pressure developed at the pump outlet is a summation  
of the pressure drop across the external valve spool orifice  
and the actuator load pressure. As the actuator load  
pressure increases, the increase is reflected directly back to  
the pump outlet. Since the compensator monitors the  
difference between pump outlet pressure and actuator load  
pressure, and this difference (nP) does not change with load  
variations, flow from the pump will stay constant.  
9
 
External Valve Spool Orifice Size Increased  
The pump outlet pressure continues to increase until the flat  
cut-off compensator spool reaches cracking pressure. The  
flat cut-off compensator spool then meters flow to the yoke  
stroking piston. The yoke stroking piston starts moving the  
yoke to reduce flow while holding the outlet pressure at  
compensator cracking pressure. This action continues until  
the pump is fully compensated (zero flow and maximum  
pressure).  
If the external valve spool orifice size is increased, pump  
outlet pressure will decrease, lowering force against the  
compensator spool. (See Figure 4.) The compensator spring  
causes the spool to move, opening the yoke stroking piston  
to case drain. As fluid is metered from the yoke stroking  
piston, the yoke spring force strokes the yoke to a higher  
flow. The increase in flow through the external valve spool  
orifice establishes once again the constant pressure drop  
(nP). With differential pressure (nP) across the external  
valve orifice, the compensator spool nulls. Flow from the  
yoke stroking piston stops, and the pump flow rate stabilizes  
at a higher value.  
Standby Operation Feature  
Standby defined: When the external valve spool is shifted to  
zero flow, the circuit is placed in standby.  
The small fixed orifice located in the compensator body  
provides a decompression feature for the load circuit during  
standby operation. The decompression feature allows the  
pump to stroke to zero flow and minimum pressure (nP), if  
the load is blocked and the external valve spool orifice is  
closed. (Refer to Figure 5.)  
Operation of the load sensing compensator is such that as  
the load pressure varies, the pump outlet pressure will follow  
the variations, holding a constant pressure drop (nP) across  
the external valve spool orifice, and a constant flow through  
the external valve and actuator. Pump flow will change only  
with changes in external valve spool orifice size.  
The circuit functions as follows:  
Assume the pump is at zero flow with maximum pressure to  
the load. The flat cut-off compensator spool will be in the up  
position (compressing the spring) and the load sensing spool  
will be in the down position due to actuator load pressure  
plus the spring force. If the external valve spool orifice is  
closed at this time, fluid under pressure will be trapped in the  
load circuit and will hold the load sensing spool in the down  
position. This will keep the pump outlet pressure at flat  
cut–off compensator cracking pressure (a power loss since  
no work is being performed at this time). To prevent this  
condition from continuing, the small orifice meters the fluid  
trapped in the load back through the flat cut-off compensator  
spool to case drain. The actuator load pressure will decrease  
gradually causing the load sensing spool to open pressure to  
the yoke stroking piston, bypassing the flat cut-off compen-  
sator. As the actuator load pressure reduces, the pump  
outlet pressure will reduce until minimum pump pressure is  
obtained. When the minimum flow/minimum pressure  
condition occurs, the pump is considered to be in standby.  
During standby, the CVP(C) control reduces the input power  
well below that of a standard “C” type compensator. This  
provides an increase in system efficiency and reduces the  
cost of operation.  
E. Compensator (Load Sensing with Pressure  
Limiting “CVP”, “CVPC”, “CVPD”)  
As expected from the above title, these units are a combina-  
tion of the flat cut-off and load sensing compensators.  
The load sensing portion functions at pressures below the  
flat cut-off compensator setting and provides a constant flow  
characteristic. If pressure exceeds the flat cut-off compensa-  
tor setting, the yoke will stroke to zero flow at maximum  
pressure lowering the horsepower requirements for holding  
circuits and protecting the pump. Refer to Figure 5  
throughout the following circuit explanation.  
Assume an actuator load that is increasing gradually. Also,  
assume the pump outlet pressure is lower than the flat  
cut-off compensator cracking pressure. As actuator load  
pressure increases, the load sensing compensator spool  
senses the difference between pump outlet pressure and  
actuator load pressure. As long as the difference between  
the pump outlet pressure and the actuator load pressure  
(nP) is constant, flow to the load will stay constant. As  
pressure rises across the load, leakage will increase in the  
pump and load. The load sensing portion of the compensator  
adjusts pump outlet flow to compensate for leakage while  
providing a constant flow through the valve spool orifice.  
10  
 
 
Set Screw  
Compensator  
Spring  
Compensator  
Spool  
Actuator  
Load  
External Valve  
Spool Orifice  
Drain  
Yoke Spring  
Yoke Stroking Piston  
Load Sensing  
Spool  
Outlet  
Inlet  
Rotating Group  
Figure 5. Load Sensing Pressure Limiting Compensator (CVP, CVPC, CVPD)  
11