Flowserve HED Worthington - Manual (Page 13)

HED/HED-DS USER INSTRUCTIONS ENGLISH 85392695 – 06/14
Page 13 of 64
3 PUMP DESCRIPTION
3.1 Configurations
HED pumps are horizontal two stage, radially split,
top/top flanged, between bearings centerline
mounted for heavy duty process services in full
compliance with API 610 standard. All sizes are
suitable for both 50 and 60 cycle operation. To
reduce NPSH requirements the HED can be fitted
with an inducer in front of the first impeller (HED-I) or
with a double suction first stage (HED-DS).
3.2 Nomenclature
The pump size will be engraved on the nameplate
typically as below:
6-HED-17-A
Nominal discharge branch size
Pump type
Nominal full size impeller diameter
Casing pattern type
The typical nomenclature above is the general guide
to the HED/HED-DS description. Identify the actual
pump size and serial number from the pump
nameplate. Check that this agrees with the applicable
certification provided.
3.3 Design of major parts
3.3.1 Pump casing
The casing is radially split with top suction and
discharge nozzles integrally cast.
This construction simplifies piping layout reducing
space requirements. Side/side or side/top
arrangements are available on request for particular
applications.
The mounting is centerline to retain alignment even at
elevated temperatures, permitting equal expansion in
all directions, and to give positive support to the
pump.
The first and second stage single volutes are
opposed to reduce hydraulic radial thrust and shaft
deflection, and the liquid is conveyed from the one to
the other by an integral cast crossover. The
interstage diaphragm too is integrally cast with the
casing. All the flow passages are accurately designed
to minimize efficiency losses.
3.3.2 Impeller
The standard impellers, single suction of the closed
type, are keyed to the shaft and secured by positive
locking devices. They are mounted face to face to
balance the hydraulic axial forces.
Impellers first and then the complete rotor are
dynamically balanced to avoid vibrations and assure
long trouble free life to seals and bearings.
Ceramic core castings are used to assure smooth
passages and the highest efficiency. Large eye areas
and low-entrance velocities give the pump very low
NPSH requirements, when extremely low NPSH
requirements are encountered, HED pumps can be
fitted with an inducer or with a double suction first
stage impeller.
Some pump sizes have more than one impeller
design, with differentiated B.E.P. capacities, for
maximum flexibility and operation with high
efficiencies throughout the coverage.
3.3.3 Wearing Rings
The casing and the impellers are fitted with
replaceable wear rings of hardened material. The
rings are held in place by a press fit with locking pins
on the casing and with threaded dowels on the
impellers.
3.3.4 Rotors
Rotors are of the stiff shaft design.
Shafts are of ample diameter, combined with the
minimum bearing span to minimize shaft deflectors
especially when the pump is operating at off peak
conditions.
Shafts are designed to meet API 610 deflection and
vibration requirements. Fully assembled rotors are
dynamically balanced can accommodate a wide
variety of single or dual seal arrangements as
standard.
3.3.5 Casing Covers
Two covers, one full size at the outboard pump end
which permits rotor removal and one reduced size
cover at inboard end provide circular type joints and
easy pump sealing with confined gaskets.
The metal to metal fit with confined controlled
compression gasket insures proper alignment
between casing and cover.
3.3.6 Bearing Housings
HED/HED-DS pumps are fitted as standard with
antifriction bearings. The radial bearing is a deep
groove type, while the thrust bearings are dual single
row angular contact type.
Lubrication is provided by an oil slinger in conjunction
with a TRICO constant level oiler, both provided as
standard. In case of particularly severe operating
conditions sleeve line with antifriction or tilting pad
thrust bearing are available with self-contained or
external lube system.