Installation and operating instructions WILO Mather and Platt – VT pumps 22
5.6 Delivery Bend
Delivery Bend/ Delivery tee which forms discharge branch
of the pump unit is a fabricated component and situated
above operating floor level. The bottom flange of the
delivery bends supports rising main pipe and pump bowl
assembly. It accommodates the stuffing box and split
gland assembly/ mechanical seal arrangement for sealing
the top shaft.
In sub-surface discharge configuration, delivery tee is
located below operating floor. If space permits, delivery
tee accommodates the stuffing box and split gland
assembly/Mechanical seal arrangement for sealing the top
shaft. Alternatively, stuffing box can be provided in bottom
flange of motor stool. Thrust Pipe, if provided, is located
opposite to delivery branch in below floor arrangement.
Tapping is provided near discharge flange of delivery bend
to accommodate pressure gauge. Delivery bend is fitted
onto a soleplate or top flange of canister when provided.
5.7 Motor Stool
It is a fabricated structure. In surface discharge installation,
motor stool rests on the top of delivery bend. The top
flange of motor stool supports the drive motor. Also thrust
bearing assembly, non-reverse ratchet assembly (when
provided) and coupling between pump and motor are
mounted in the motor stool. Openings are provided to
access the parts housed in motor stool.
When hollow shaft motor is provided with combined thrust
bearing for pump and motor, motor stool and coupling to
connect pump - motor shafts are not provided.
5.8 Thrust bearing Assembly
It consists of thrust bearing to take up axial and radial
thrust. Small vertical pumps have grease lubricated
bearings while medium to large vertical pumps have oil
lubricated bearings. Oil level should be checked prior to
starting of pump. (Fig: 13, Pg. No. 10)
5.9 Non-Reverse Ratchet Arrangement
Non-Reverse Ratchet is mechanical device to prevent the
reverse rotation of pump, motor during flow reversal
condition. It consists of a fixed ratchet and rotating pins as
shown in enlarged details.
The ratchet plate teeth allow pins to slide up during normal
direction of rotation. However, during reversal, the pins
engage with the teeth and prevent reverse rotation. A
pump could be offered optionally without Non reverse
arrangement if reverse rotation detection system and non-
return valve is provided. (Fig: 14 Pg. No. 11)
5.10 Thrust Pipe Arrangement
Thrust pipe arrangement is provided to absorb back thrust
generated in below floor discharge arrangements. Thrust
pipe is bolted to delivery bend on one side and welded to
insert plate fixed in column on other side. An adaptor pipe
may be provided in between to adjust the lengths. Insert
plate is to be fixed with anchor bolts to column. Refer Fig
13 Pg. No. 10 above.
5.11 Line Shafts
Line shaft shall be of suitable diameter and length as per
pump manufacturer’s recommendation with 30% margin
on both sides for critical speed with interchangeable
sections of standard lengths of 1, 1.5, 2, 2.5, 3m. To ensure
correct alignment shafts should be straight within
0.125mm for 3 m length total dial indicator reading. Line
shafts are coupled together with the help of rigid coupling.
Maximum permissible error in the axial alignment of the axis
with the axis of shaft shall be 0.05 mm in 150 mm. Line shaft
are provided with sleeves to be supported in line shaft bearing
at suitable intervals.
5.12 Line Shaft bearing
Line shaft bearing could be of Thordon, Cutless rubber,
Feroform, Finocot, Bronze or any other special material
depending upon application and shall be spaced at suitable
interval securely in bearing spider located between column
pipes. The bearings shall consist of grooves to allow water and
oil flow to the bearing below. In case of oil lubricated pump with
shaft enclosing tubes, bearing bronze material is to be used.
5.13 Shaft enclosing tubes
Shaft enclosing tubes are used in forced water and oil
lubricated pumps. Shaft tube is generally supported on bearing
carriers between bearing spiders with a sealing ring provided at
both ends to prevent leakage. Shaft tube should be selected
such that sufficient clearance is maintained between shaft tube
internal diameter and shaft rigid coupling outer diameter
allowing required quantity of water / oil to pass to bearing
below. Bottom most shaft tube should be located in diffuser/
casing with an adaptor.
5.14 Stuffing Box
Stuffing box may be provided either with gland packing or
mechanical seal as per client’s requirements. Gland packing of
plaited cotton and colloidal graphite is provided as standard
material, others may be provided on request. Stuffing box also
acts as a bearing support for head shaft; hence a sleeve is
provided to accommodate the rubbing. Logging ring / lantern
ring is provided in stuffing box is provided for lubrication and
bypassing additional fluid via leak off connection. Throttle bush
may be provided in stuffing box in case if high pressure pumps
to prevent mechanical seal faces from being damaged. (Refer
Fig. 15 Pg. No. 11)
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