Principle of pump operation, Installation – Blagdon Pump B15 Metallic User Manual
Page 5
 
HG-CF-909 Rev. V - 13.11.14
Page 5
PRINCIPLE OF PUMP
OPERATION
 
This ball valve type diaphragm pump is 
powered by compressed air and is a 1:1 ratio 
design. The inner side of one diaphragm 
chamber is alternately pressurised while 
simultaneously exhausting the other inner 
chamber. This causes the diaphragms, which are 
connected by a common shaft secured by plates 
to the centres of the diaphragms, to move in a 
reciprocating action. (As one diaphragm 
performs a discharge stroke the other diaphragm 
is pulled to perform the suction stroke in the 
opposite chamber.) Air pressure is applied over 
the entire inner surface of the diaphragm while 
liquid is discharged from the opposite side of 
the diaphragm. The diaphragm operates in a 
balanced condition during the discharge stroke 
which allows the pump to be operated at 
discharge heads of over 200 feet (61 meters) of 
water. 
 
For maximum diaphragm life, keep the pump as 
close to the liquid being pumped as possible. 
Positive suction head in excess of 10 feet of 
liquid (3.048 meters) may require a back 
pressure regulating device to maximize 
diaphragm life. 
 
Alternate pressurising and exhausting of the 
diaphragm chamber is performed by an 
externally mounted, pilot operated, 2 way type 
distribution valve. When the spool shifts to one 
end of the valve block body, inlet pressure is 
applied to one chamber and the other diaphragm 
chamber exhausts. When the spool shifts to the 
opposite end of the valve body, the pressure to 
the chambers is reversed. This alternating 
movement of the spool inside the valve body is 
controlled by a pilot air pressure signal held 
against the diaphragm shaft, between seals in the 
diaphragm shaft bushes. This signal is released, 
triggering the movement of the spool, when pilot 
holes in the diaphragm shaft align with the held 
pilot signal, sending the signal to exhaust, which 
in-turn causes a pressure imbalance around the 
spool, sending it to the opposite end of the valve 
body. This simultaneously sends inlet pressure 
to the opposite chamber. 
 
The chambers are connected by manifolds with a 
suction and discharge ball valve for each 
chamber, maintaining flow in one direction 
through the pump. 
INSTALLATION
 
The typical installation shown in FIG. 1 is only a 
guide to selecting and installing system 
components. Your installation will depend on 
the type of fluid being pumped and your 
application needs. To reduce the risk of serious 
bodily injury and damage to property, never use 
fluids in this pump which are not compatible 
with the wetted components. Contact your local 
distributor or the manufacturer for system design 
assistance & compatibility if necessary. 
 
Mount the pump in an upright position. Failure 
to ensure an upright position may result in loss 
of or poor priming characteristics. Ensure the 
pump is securely mounted to avoid movement 
and possible risk of bodily injury. 
 
PRESSURE The pump delivers the same 
pressure at the discharge outlet as the air 
pressure applied at the air inlet (unless pump is 
configured as a 2:1 ratio model). 
 
NOTE: Pressure Regulator (H) should be 
installed where air supply could exceed 125 
psi. 
 
SAFETY 
 
Your BLAGDON PUMP is a high 
performance unit capable of achieving 
high outputs at high efficiencies. However, as 
is common with pneumatic equipment, the 
pump efficiencies is reliant upon the air being 
clean, dry and filtered. Failure to comply with 
these requirements may lead to loss of 
performance and reduced component life and in 
extreme cases, permanent damage to the pump. 
 
To avoid leaks, ensure that all fluid connections 
are tight. The use of PTFE thread tape correctly 
applied should be used to ensure 100% leak 
proof connections. Failure to ensure 100% 
sealability of the suction connection could 
adversely affect suction performance. 
 
If you are pumping hazardous fluids, or 
operating the pump in an enclosed area, it is 
essential that the exhaust from the pump is 
piped away to a safe location. When pumping 
hazardous fluids the above instructions must be 
adhered to in order to ensure safe operating 
procedures. (Under certain operating 
conditions the failure of internal components 
can lead to the pumped fluid being exhausted 
via the pump exhaust outlet). 
 
WARNING 
 
NEVER place your hands over or near the 
pump suction inlet. Powerful suction could 
cause serious bodily injury. 
FLUSH  THE PUMP This pump was tested 
with water containing an oil-based rust 
inhibitor. If this solution could contaminate or 
react with the fluid you are pumping, flush the 
pump thoroughly with a solvent/detergent to 
clean internal components. The solvent/
detergent must be compatible with the pump 
materials of construction. Care should be taken 
to flush the pump each time it is disassembled 
for maintenance or repair.
 
CAUTION 
All BLAGDON PUMPS are built lubricated 
with grease during assembly and need no 
further lubrication. If the use of oil cannot be 
avoided, this will not present any problems. A 
light No. 2 class lithium grease is 
recommended. Other grades may cause the Air 
Logic System to operate intermittently, thereby 
causing a loss of output and failure to operate. 
Other seals are available for “clean room” 
conditions 
 
If the pump accelerates or is running too fast 
due to a lack of fluid, then stop it immediately 
by shutting off the air supply. A dry pump will 
accelerate to a high speed causing wear to 
elastomers. 
 
If the fluid you are pumping tends to dry up or 
set when it is not moving, then flush the pump 
as often as necessary to prevent the fluid from 
drying in the pump. Drain the pump thoroughly 
before storing. 
 
If feasible, invert pump to allow any fluid to 
drain from the non-return valves
.
AIR
Exhaust
1
3
2
4
Flexible
Connection
Pipe Connection
(Style Optional)
Gauge
Shut-off
Valve
Drain Port
DISCHARGE
Pulsation
Dampener
Regulator/Lubricator
Air Shut-Off
Valve
Air Dryer
INLET
Air Inlet
Air Exhaust
Pipe Connection
(Style Optional)
Air
Gauge
Shut-off
Valve
Drain Port
SUCTION
Filter
Connection
Flexible
Installation Guide
Fig. 1
Available from
Blagdon Pump :-
1. Pulsation Dampener 
2. Filter/Regulator 
3. Lubricator 
4. Air Dryer 
CAUTION ! 
The air exhaust should be piped 
to an area for safe disposition of 
the product being pumped, in the 
event of diaphragm failure.