C-1075A
DEEPWELL CARGO PUMPS
FOR LIQUEFIED GAS CARRIERS
STN
STN DEEPWELL CARGO PUMPS
Shinko STN deepwell centrifugal pumps have been
designed and manufactured as cargo pumps for liquefied
gas such as LPG, liquefied ammonia, vinyl chloride mono-
mer, ethylene, etc. It has the following features:
⃝The prime mover is installed on top of the cargo tank and the impel-
lers are submerged in the liquid which is driven through the long
intermediate shaft. Therefore, priming equipment is unnecessary.
⃝As it is a multi-stage pump, any head can be applied by changing the
number of stages.
⃝The inducer has excellent suction performance at the bottom end.
Thus, it can reduce the residual liquid to a minimum.
⃝The discharge pipe is used as support for the casing and intermediate
shaft. Hence, extra piping in tank is unnecessary, reducing the setup
cost.
⃝Our most reliable mechanical seal has been equipped as the stuffing
box seal. It can be replaced safely and easily without removing the
pump from the tank, even if the mechanical seal is damaged.
⃝For the prime mover, a pressure-resistant and explosion-proof motor
is employed.
■ GENERAL CHARACTERISTICS
Model
STN 125 STN 150 STN 200 STN 202
Item
Type Deepwell multi-stage type with inducer
Handling liquid LPG. Liquefied ammonia. VCM. Ethylene
Liquid temperature（℃） －110～＋45
Number of stages 4, 5, 6 3, 4, 5 3, 4, 5 3, 4, 5
Speed （min ）
‒1
1750
Discharge bore （mm） 125 150 200 200
Direction of rotation Clockwise when viewed from the prime mover
Thrust bearing Ball bearing
Lubrication Grease
Stuffing box seal Mechanical seal
1
■ PERFORMANCE CHART
Ethylene
SG：0.57
Propane, Butane
SG：0.61
Butadiene, Ammonia
SG：0.65
VCM
SG：0.94
2
■ DESIGN & MATERIALS
The pump casing is attached to the bottom end of the
long discharge pipe. And, the impellers are driven
through a long intermediate shaft, which is supported
by submerged line bearings.
At the pump inlet, an inducer is equipped in order to
improve the suction performance and a mechanical seal
is utilized where the shaft passes through a casing of
the pump support.
As the pump is equipped with a split discharge pipe, it
is possible to carry out maintenance in the tank with-
out lifting out the pump.
The following table should be referred to when han-
dling liquids at temperature between −110℃ and
−10℃. When handling liquids above −10℃, the follow-
ing materials must be changed:
Suction casing, stage casing, and inducer
：Ductile cast iron（FCD600）
Volute and impeller ：Cast iron（FC200）
Pump support ：Cast steel（SC450）
Discharge pipe ：Steel（SGP）
Shaft ：Stainless steel（SUS 403）
REQ. MATERIAL
PART NO
NAME OF PART
NO. FOR ASTM
1PUMP NAME JIS
EQUIVALENT
A296-77
1 SUCTION CASING 1 STAINLESS STEEL SCS13 CF 8
2 VOLUTE 〃 〃 〃
3 STAGE CASING 〃 〃 〃
4 DISCHARGE CASING 1 〃 〃 〃
5 PUMP SUPPORT 1 〃 〃 〃
6 MOTOR BED 1 STEEL SS400 A6-71
A276-77
7 DISCHARGE PIPE STAINLESS STEEL SUS304L 304L
8 BEARING HOUSING 1 CAST IRON FC200 A48-76
A296-77
15 INDUCER 1 STAINLESS STEEL SCS13 CF 8
16 IMPELLER 〃 〃 〃
A276-77
18 SHAFT 〃 SUS304 304
22A SLEEVE 〃 〃 〃
22B SLEEVE 〃 〃 〃
23 BALANCE BUSH 1 SPECIAL CARBON
A276-77
24 BALANCE PISTON 1 STAINLESS STEEL SUS304 304
35 BALL BEARING 1 SPECIAL STEEL
38 MOUTH RING SPECIAL CARBON
41 LINE BEARING 〃
42 LINE BEARING 〃
A276-77
49 COUPLING 1 STAINLESS STEEL SUS304 304
A536-77
50 COUPLING 1 DUCTILE CAST IRON FCD400 60-40-18
50A SPACER COUPLING 1 〃 〃 〃
A276-77
52 SLEEVE COUPLING STAINLESS STEEL SUS304 304
53 ADJUSTING NUT 1 STEEL SS400 A6-71
A276-77
54 MECHANICAL SEAL 1 SET STAINLESS STEEL SUS316 316
3
●Pump Casing ●Impeller
The pump casing has quadruple chambers, consisting The impellers are a single suction type. And, the
of several volutes, stage casings, and a discharge cas- inside passages are finished with great care to
ing, where the kinetic energy of the handling liquid dis- improve pump efficiency.
charged from the impellers is converted into the pres- The impellers are located on the shaft and firmly
sure energy. secured by means of keys, sleeves, and split rings.
The pressure induced on the exterior of the impellers Hence, the shaft does not bend and is free from axial
is distributed symmetrically to the shaft center. The expansion and shrinkage.
radial thrust acting on the impellers is balanced at
each stage. And, no shaft deflection occurs in any oper-
ating ranges.
As the volute is an open type, internal finishing, clean-
ing, and inspection can be carried out easily. And, it
can be assembled inside the stage casing.
Each stage casing is tightened with rigid bolts along
with a suction cover and a discharge casing.
●Balance Piston
In order to balance the downward thrust that occurs on
the impellers, a balance piston acting against the discharge
pressure is employed on the upper side of the pump.
●Inducer
To minimize the NPSH level of the pump, an inducer
is employed at the inlet of the 1st stage impeller.
The inducer is a booster, having two spiral blades,
improves suction performance.
4
a safe location.
●Thrust Bearing
When it is necessary to inspect or replace the seal,
A single row deep groove ball bearing (63 type), hav- the following method should be carried out:
ing sufficiently long service life, is fitted on the upper
side of the pump.
As the grease-sealed ball bearing is used, it is not nec- DURING OPERATION DURING REPLACEMENT
essary to pour out the grease. And, the pump can be
maintained easily.
●Line Bearing
Line bearings are used in the pump casings and in the
discharge pipes as radial bearings, and they are lubri-
cated by the handling liquid.
Generally, the handling liquid tends to achieve lower
lubricating performance in the case of low viscosity.
For this reason, special high wear-resisting carbon is
employed as material for the bearings. Therefore, the
dry running is possible during the stripping process.
⑴ Left and right side of the figure above show con-
ditions during normal operation and during replace-
ment of the seal. First, the balance piston is pushed
down by tightening the jack bolt to prevent gas
leakage from the tank.
⑵ After removing the spacer coupling, the pump-
side coupling can be removed along with the ball
bearing and the bearing housing.
●Stuffing Box Seal ⑶ Next, the mechanical seal can be pulled out along
with the sleeve after removing the sleeve nut.
A reliable mechanical seal has been attached to the
stuffing box.
⑷ The seal can be reassembled by following these
It is quite difficult to completely prevent leakage from
steps in reverse order. The mechanical seal can be
the mating face when a single mechanical seal is fit-
fastened properly by attaching the sleeve with the
ted in the pump while handling liquefied gas.
set plate.
Therefore, double mechanical seals have been
equipped to stop the liquefied gas from leaking into
the atmosphere directly through the seals.
The gas leaked from the lower seal is gathered into
the oil tank through the upper seal box and the cool-
ing tube, and then is released into the atmosphere in
5
●Stuffing Box Seal Customized for Cryogenic Liquid (Option)
When handling liquid at temperatures of about −100℃, it is quite difficult to keep the temperature of the stuffing
box the same as the handling liquid since there is such a big temperature difference with the atmosphere.
Ethylene can be explosive when it becomes the mixed with oxygen at a rate of 1 part oxygen to 2 parts ethylene.
Therefore, leakage of these liquids must be avoided at all costs.
With consideration to the above, the stuffing box seal of the cargo pump, which handles the cryogenic liquid, has
the following design:
1．A large vapour chamber is located between the 3．To detect abnormal seal liquid leakage, the follow-
pump case and the stuffing box. The upper part of ing measures are taken:
the vapour chamber is designed as a buffer zone
and a double mechanical seal has been equipped at a．When the leak comes from the upper mating face
the stuffing box. of the double mechanical seal, the piston in the
equalizer descends, and the conditions can be
2．Refrigerating machine oil or methanol is used as a judged by the level gauged attached to the equal-
sealing liquid for the double mechanical seal. izer.
Pressure in the buffer zone is added to the sealing
liquid via an equalizer which has a piston and is b．When the leak comes from the lower mating face
able to adjust to the variation in pressure in the of the double mechanical seal, sealing liquid
buffer zone, and continuously applies a slightly high- enters the vapour chamber and the piston equal-
er pressure to the stuffing box side, consequently izer descends from the loss of sealing liquid, and
preventing any gas leakage. the conditions can also be judged by the level
When operating the pump in a cold zone, heating is gauge.
applied to the stuffing box. The flinger is equipped to prevent the leaked
sealing liquid from entering from the pump side.
6
Dimensions：mm
Model A B C D E F G H
STN 125 480 1330 260 925 330 700 450 45
STN 150 480 1330 260 925 330 700 600 55
STN 200 515 1360 260 925 330 700 650 70
STN 202 515 1390 260 925 330 740 700 85
Printed in Japan 2017-11-50 N.H.
