ISO 10437:1993

INTERNATIONAL
ISO
STANDARD
First edition
1993-12-15
Petroleum and natura1 gas industries -
Special-purpose steam turbines for refinery
Service
Industries du phtrole et du gaz naturel - Turbines A vapeur d’usage
spkcial pour Service en raffinerie
Reference number
Foreword
ISO (the International Organization for Standardization) is a worldwide
federation of national Standards bodies (ISO member bodies). The work
of preparing International Standards is normally carried out through ISO
technical committees. Esch member body interested in a subject for
which a technical committee has been established has the right to be re-
presented on that committee. International organizations, governmental
and non-governmental, in liaison with ISO, also take part in the work. ISO
collaborates closely with the International Electrotechnical Commission
(1 EC) on all matters of electrotechnical standardization.
Draft International Standards adopted by the technical committees are
circulated to the member bodies for voting. Publication as an International
Standard requires approval by at least 75 % of the member bodies casting
a vote.
International Standard ISO 10437 was prepared by the American Petro-
leum Institute (API) (as STD 612, 3rd edition) and was adopted, under a
special “fast-track procedure”, by Technical Committee lSO/TC 67, Mate-
rials, equipment and offshore structures for Petroleum and natura1 gas in-
dustries, in parallel with its approval by the ISO member bodies.
0 ISO 1993
All rights reserved. Unless otherwise specified, no part of this publication may be reproduced
or utilized in any form or by any means, electronie or mechanical, including photocopying and
microfilm, without Permission in writing from the publisher.
International Organization for Standardization
Case Postale 56 l CH-l 211 Geneve 20 l Switzerland
Printed in Switzerland
CQ ISO
Introduction
International Standard ISO 10437:1993 reproduces the content of
API STD 612, 3rd edition, 1987. ISO, in endorsing this API document, re-
cognizes that in certain respects the latter does not comply with all current
ISO rules on the presentation and content of an International Standard.
Therefore, the relevant technical body, within ISORC 67, will review
these rules.
This Standard is not intended to obviate the need for Sound engineering
judgement as to when and where this Standard should be utilized and
users of this Standard should be aware that additional or differing require-
ments may be needed to meet the needs for the particular sen/ice in-
tended.
Standards referenced herein may be replaced by other international or
national Standards that tan be shown to meet or exceed the requirements
of the referenced Standards.
Appendices A and C to E form an integral patt of the requirements of this
Standard.
This page intentionally left blank

INTERNATIONAL STANDARD 0 ISO ISO 10437:1993(E)
Petroleum and natura1 gas industries -
Special-purpose steam turbines for refinery Service
1 Scope
This International Standard specifies the minimum requirements for special-purpose steam turbines for use in
Petroleum refinery Service.
2 Requirements
Requirements are specified in:
“API Standard 612 (Std 612), Third Edition, November 1987, Special-Purpose Steam Turbines For Refinery
Services”,
which is adopted as ISO 10437.
For the purposes of international standardization, however, modifications shall apply to specific clauses and para-
graphs of publication API Std 612. These modifications are outlined below.
Page 6
Subclause 1.5.1
The referenced Standards listed hereafter are available under the following ISO references:
API Std 611 as ISO 10436
API Std 613 as ISO 13711 (at present under study)
API Std 614 as ISO 10438
API Std 671 as ISO 10441 (at present under study)
(Blank pagd
Special-Purpose Steam Turbines
For Refinery Services
API STANDARD 612
THIRD EDITION, NOVEMBER 1987
American Petroleum Institute
1220 L Street, Northwest
Washington, D.C. 20005
ISO 10437:1-993(E)
Special-Purpose Steam Turbines for Refinery Services
SECTION l-GENERAL
1.4.2 Rated applies to the greatest turbine power specified
1.1 Scope
and the corresponding Speed. It includes all the margin re-
1.1.1 This Standard covers the minimum requirements for
quired by the specifications of the driven equipment.
special-purpose steam turbines for refinery Services. These
Maximum continuous Speed (in revolutions per min-
requirements include basic design, materials, and related 1.4.3
lube-oil Systems, controls, and auxiliary equipment. ute) is the Speed at least equal to 105 percent of the highest
Speed required by any of the specified operating conditions.
Note: A bullet ( l ) at the beginning of a paragraph indicates that a decision
by the purchaser is required. These decisions should be indicated on the
1.4.4 Maximum allowable Speed (in revolutions per min-
data sheets (see Appendix A): otherwise they should be stated in the quota-
ute) is the highest Speed at which the manufacturer’s design
tion request or in the Order.
will permit continuous Operation.
1.1.2 Steam turbines are classified general-purpose or
1.4.5 Trip Speed (in revolutions per minute) is the Speed
special-purpose according to Service requirements as
at which the independent emergency overspeed device oper-
described in 1.1.2.1 and 1.1.2.2.
ates to shut down a Prime mover. Trip Speed shall be at least
1.1.2 .l General-purpose turbines are those horizontal or
110 percent of the maximum continuous Speed.
vertical turbines used to drive equipment that is usually
1.4.6 Maximum inlet pressure and temperature refer to the
spared, is relatively small in size (power), or is in noncriti-
highest inlet steam pressure and temperature conditions at
cal Service. They are intended for applications where steam
which the turbine is required to operate continuously.
conditions will not exceed 600 pounds per Square inch gauge
(41 bar gauge) pressure or 750°F (400 “C) inlet temperature,
1.4.7 Minimum inlet pressure and temperature refer to the
or both, and where Speed will not exceed 6000 revolutions
lowest inlet steam pressure and temperature conditions at
per minute. Requirements for general-purpose turbines are
which the turbine is required to operate continuously.
defmed in API Standard 611.
1.4.8 Maximum exhaust pressure is the highest exhaust
1.1.2.2 Special-purpose turbines are those horizontal tur-
steam pressure at which the turbine is required to operate
bines used to drive equipment that is usually not spared, is
continuously.
relatively large in size (power), or is in critical Service. This
Minimum exhaustpressure is the lowest exhaust steam
category is not limited by steam conditions or turbine Speed. 1.4.9
pressure at which the turbine is required to operate con-
tinuously.
1.2 Alternative Designs
1.4.10 Maximum exhaust casing pressure is the highest ex-
The vendor may offer alternative designs. Equivalent met-
haust steam pressure that the purchaser requires the casing
rit dimensions, fasteners, and flanges may be substituted as
to contain, with steam supplied at maximum inlet conditions.
mutually agreed upon by the purchaser and the vendor.
1.4.11 Maximum allowable working pressure is the maxi-
mum pressure for which the manufacturer has designed the
1.3 Confiicting Requirements
equipment when operating at the maximum allowable tem-
perature.
In case of conflict between this Standard and the inquiry
or order-, the information included in the Order shall govern.
1.4.12 AxiaUy Split refers to casing joints that are parallel
to the shaft centerline.
1.4 Definition of Terms
1.4.13 Radially Split refers to casing joints that are trans-
Verse to the shaft centerline.
Terms used in this Standard are defined in 1.4.1 through
1.4.23.
1.4.14 v The use of the word design in any term (such as de-
1.4.1 The normul operating Point is the Point at which usual sign power, design pressure, design temperature, or design
Operation is expected and Optimum efficiency is desired. This Speed) should be avoided in the purchaser’s specifications.
Point is usually the Point at which the vendor certifies that This terminology should be used only by the equipment
Performance is within the tolerantes stated in this Standard. designer and the manufacturer.
B16.1 Cast Iran Pipe Flanges and Flanged Fittings,
1.4.15 Heat rate is a Prime mover’s energy consumption
Class 25, 12.5, 250, and 800
per unit of work. It is expressed in British thermal units (Btu)
B16.5 Pipe Flanges and Flanged Fittings, Steel, Nickel
per horsepower-hour or Btu per kilowatt-hour, based on the
AZlov and Other Special Allovs
lower heating value of the fuel.
Bl6.11 Forged Steel Fittings, Sockft-Welding and
1.4.16 Steam rate is the quantity of steam required by the
732readed
turbine per unit of power output measured at the output shaft
B 16.42 Ductile Iron Pipe Flanges and Flanged Fittings,
of the turbine. It is expressed in pounds of steam per
Class 150 and 300
horsepower-hour or in kilograms of steam per kilowatt-hour.
B17.1 Keys and Keyseats
1.4.17 Maximum allowable temperature is the maximum
Yl4.2M Line Conventions and Lettering
continuous temperature for which the manufacturer has
API
designed the equipment (or any part to which the term is re-
RP 520 Recommended Practice for the Design and In-
ferred) when handling the specified fluid at the specified
stazlation of Pressure-Relieving Systems in
pressure. -
Refineries, Part I-Design and Part II-
1.4.18 Maximum sealing pressure is the highest pressure
Installation
expected at the Seals during any specified static or operating
Std 526 Flanged Steel Safety Relief Valves
conditions and during startup and shutdown.
RP 550 Manual on Installation of Re$nery Instruments
1.4.19 Minimum allowable Speed (in revolutions per min-
and Control Systems
ute) is the lowest Speed at which the manufacturer’s design
Std 611 General-Purpose Steam Turbines for Refinery
will permit continuous Operation.
Services
1.4.20 Potential maximum power is the approximate maxi- Std 613 Special-firpose Gear Units for Rejnery Services
mum power to which the turbine tan be uprated at the speci- Std 614 Lubrication, Shaft-Sealing, and Control-Oil Sys-
fied normal Speed and steam conditions when it is furnished tems for Special-Purpose Applications
with suitable (larger or additional) nozzles and, possibly, with
Std 615 Sound Control of Mechanical Equipment for Re-
a larger governor-controlled valve or valves.
jnery Services
Std 670 Vibration, Axial-Position, and Bearing-
1.4.21 The pressure casing is the composite of all station-
Temperature Monitoring Systems
ary pressure-containing Parts of the unit, including all noz-
Std 671 Special-Purpose Couplings for Refinery Services
h
zles and other attached Parts.
Std 678 Accelerometer-Based Vibration Monitoring
1.4.22 Standby Service refers to a normally idle or idling
System
piece of equipment that is capable of immediate automatic
or manual startup and continuous Operation.
ASME2
1.4.23 Field changeable refers to a design feature that per-
Boiler and Pressure Essek Code, Section VIII, “Rules for
mits alteration of a function after the equipment has been in-
Construction of Pressure Vessels,” and Section
stalled. The alteration may be accomplished by (a) soldering
IX, ’ ‘Welding and Brazing Qualifications”
jumper leads to terminal pins especially provided for this pur-
B1.20.1 General Purpose (Inch) Pipe Threads
pose, (b) employing circuit-board-mounted switches or poten-
B31.3 Chemical Plant and Petroleum Re$nery Piping
tiometers, (c) using a shorting or diode-pin-type matrix board,
PT@ 6 Steam Turbines
or (d) using prewired shorting plugs.
ASTM3
1.5 Referenced Publications
A 53 Zinc-Coated Welded and Seamless BZack and
1.5.1 The editions of the following Standards, Codes, and
Hot-Dipped Steel Pipe
specifications that are in effect at the time of publication of
A PO6 Seamless Carbon Steel Pipe for High-
this Standard shall, to tk extent specified herein, form a gart
Temperature Service
of this Standard. The applicability of changes in Standards,
A 192 Seamless Carbon Steel Boiler Tubes for High-
Codes, and specifications that occur after the inquiry shall
Pressure Service
be mutually agreed upon by the purchaser and the vendor.
A 194 Carbon and Alloy Steel Nuts for Bolts for High-
ANSI’
Pressure and High-Temperature Service
Bl.1 Uni.‘ed Inch Screw Threads (UN and L?NR
nread Form)
?American Society of Mechanical Engineers, 345 East 47th Street, New York,
New York lOQl7.
?‘j, --y=+-y-~ ~,--+ * f-
7esh~ and Materials, 1916 Rate Street, Philadel-
y; l? / . .’
..,;: g~g:,l’i;& ‘: . x:\:<
A 269 Seamless and Welded Austenitic Stainless Steel E 125 Reference Photographs for Magnetit Particle In-
Tubing for General Service dications on Ferrous Castings
A 278 Gray Iran Castings for Pressure-Containing Parts E 709 Practice for Magnetit Particle Examination
for Temperatur-es Up to 650°F (345°C)
AWS4
A 307 Carbon Externally Threaded
Steel
Dl.l Structural Welding Code-Steel
Standard Fasteners
A 312 Seamless and Welded Austenitic Stainless Steel
NEMA5
Pipe
SM 23 Steam Turbines for Mechanical Drive Service
A 358 Electric-Fusion-Welded Austenitic Chromium-
Nickel Alloy Steel Pipe for High-Temperature
NFPA6
Service
70 National Electrical Code
A 395 Ferritic Ductile Iron Pressure-Retaining Castings
496 Purged Enclosures for Electrical Equipment in
for Use at Elevated Temperatures
Hazardous Locations
A 418
Method for Ultrasonic Inspection of Turbine and
Generator Steel Rotor Forgings
OSHA’
A 472
Test Methodfor Heat Stabil@ of Steam Turbine
Occupational Safety and Health Standards of the U.S.
Shafis and Rotor Forgings
Department of Labor
A 515 Carbon Steel Pressure Vessel Plates for
Intermediate- and Higher-Temperature Service l 1.52 The purchaser and the vendor shall mutually deter-
A 536 Ductile Iran Castings mine the measures that must be taken to comply with any
B 127 federal, state, or local Codes, regulations, ordinances, or rules
Nickel-Copper Alloy (UNS NOO4400) Plate,
that are applicable to the equipment.
Sheet, and Strip
SECTION 2-BASIC DESIGN
exhaust conditions. The purchaser will specify both the Speed
2.1 General
and torque values required.
2.1.1 The equipment (including auxiliaries) covered by this
f. Continuous Operation at conditions agreed upon between
Standard shall be designed and constructed for a minimum
the purchaser and the vendor for extraction or induction or
Service life of 20 years and at least 3 years of uninterrupted
both.
Operation. It is recognized that this is a design criterion.
g. Operation with variations from rated steam conditions per
NEMA SM 23.
a 2.1.2 The purchaser will specify the equipment’s normal
h. Operation uncoupled with maximum inlet steam condi-
operating Point on the data sheets.
tions. (Governing instability may occur and require action
2.1.3 Turbines shall be capable of the following:
such as throttling of inlet pressure.)
a. Operation at normal power and Speed with normal steam
2.1.4 Equipment shall be designed to run without darnage
conditions. The steam rate (heat rate) certified by the
to the trip Speed and relief valve settings.
manufacturer shall be at these conditions.
2.1.5 After installation, the combined Performance of the
b. Delivering rated power at its corresponding Speed with
machine and its driven equipment shall be the joint respon-
coincident minimum inlet and maximum exhaust conditions
sibility of the purchaser and the vendor. The units shall per-
as specified on the data sheets.
form on the test stand and on their permanent foundation
Note: To prevent oversizing and/or to obtain higher operating efficiency. it
within the specified acceptance criteria.
may be desirable to limit maximum turbine capability by specifying normal
power or a selected percentage of rated power instead of rated power at the
a 2.1.6 Many factors (such as piping loads, alignment at oper-
conditions specified.
ating conditions, supporting structure, handling during ship-
c. Continuous Operation at maximum continuous Speed and
at any other Speed within the range specified.
4American Welding Society, 550 N.W. LeJeune Rd. Miami, Florida 33135.
d. Continuous Operation at rated power and Speed with maxi-
5National Electrical Manufacturers Association, 2101 L Street, N.W.,
Washington, D.C. 20037.
mum inlet steam conditions and maximum or minimum ex-
6Nationai Fire Protection Association, Batterymarch Park. Quincy. Mas-
haust steam conditions.
sachusetts 02269.
l e. Continuous Operation at the lowest Speed at which maxi-
70ccupational Safety and Health Administration, U.S. Department of La-
bor. Washington, D.C. 20210.
mum torque is required with minimum inlet and maximum

4 API STANDARD 612
the requirements of NFPA 70, Articles 500 and 501, as well
ment, and handling and assembly at the site) may adversely
as local Codes specified and furnished by the purchaser.
affect site Performance. To minimize the influence of these
factors, the vendor shall review and comment on the pur-
a 2.1.13 The purchaser will specify whether the installation
chaser‘s piping and foundation drawings. and the vendor’s
is indoors (heated or unheated) or outdoors (with or without
representative shall observe a check of the piping performed
a roof), as weil as the weather and environmental conditions
by parting the flanges. The vendor’s representative shall check
in which the equipment must operate (including maximum
alignment at the operating temperature and. when specified.
and minimum temperatures and unusual humidity or dust
shall be present during the initial alignment check.
Problems). The unit and its auxiliaries shall be suitable for
operation under these specified conditions. For the pur-
2.1.9 The arrangement of the equipment, including piping
chaser‘s guidance. the vendor shall list in the proposal any
and auxiliaries, shall be developed jointly by the purchaser
and the vendor. The arrangement shall provide adequate clear- special protection that the purchaser is required to supply.
ante areas and safe access for Operation and maintenance.
2.1.14 Spare Parts for the machine and all furnished aux-
iliaries shall meet all the criteria of this Standard.
2.1.8 All equipment shall be designed to permit rapid and
economical maintenance. Major Parts such as casing com-
2.1.15 The vendor shall assume responsibility for the en-
ponents and bearing housings shall be designed (shouldered
gineering Coordination of the equipment and all auxiliary sys-
or doweled) and manufactured to ensure accurate alignment
tems included in the scope of the Order.
on reassembly.
2.1.9 Oil reservoirs and housings that enclose moving lubri-
2.2 Pressure Casings
cated Parts (such as bearings, shaft Seals, highly polished
2.2.1 All pressure Parts shall be at least suitable for oper-
Parts, instruments, and control elements) shall be designed
ation at the most severe conditions of coincident pressure and
to minimize contamination by moisture, dust, and other for-
temperature expected with the specified steam conditions.
eign matter during periods of Operation or idleness.
2.1 .lO Unless otherwise specified, cooling water Systems
2.2.2 The hoop-stress values used in the design of the cas-
shall be designed for the following conditions:
ing shall not exceed the maximum allowable stress values in
tension specified in Section VIII, Division 1, of the ASME
Velocity over heat exchange
Code at the maximum operating temperature of the material
1 .S-2 .S m/s
surfaces 5-8 ft/s
used.
Maximum ailowabie working
pressure 275 psig ~5.2 bar (ga)
2 115 psig
Test pressure ~7.9 bar (ga)
2.2.3 The maximum allowable working pressure of the cas-
15 psi
Maximum pressure drop 1 bar
ing shall be at least equal to the specified relief valve setting.
Maximum inlet temperature 90°F 32°C
For condensing turbines the maximum allowable working
120°F
Maximum outiet temperature 39 “C
Maximum temperature rise 30°F 17°C
pressure of the exhaust casing shall be full vacuum and at
20 “F
Minimum temperature rise 11°C
least 10 pounds per Square inch gauge.
0.002 hr-ft* - “F/Btu
Fouiing factor on water side 0.35 rn’ l K/kW
Note: Normaiiy a fuii-capacity safety reiief valve is required in the exhaust
Provision shall be made for complete venting and draining piping between each exhaust connection and exhaust block valve to prevent
overpressure and possible rupture of the turbine casing.
of the System.
2.2.4 The turbine casing shall be axially Split. Turbine cas-
Note: The vendor shaii notify the purchaser if the criteria for minimum tem-
perature rise and veiocity over heat exchange surfaces resuit in a conflicting ings may also be Split radially between high-pressure and low-
design. The criterion for veiocity over heat exchange surfaces is intended
pressure portions. If the casing must be Split into two or more
to minimize water-side fouiing; the criterion for minimum temperature rise
pressure levels, the vendor shall defme the physical limits and
is intended to minimize the use of cooiing water. The purchaser will ap-
prove the final seiection. the maximum allowable working pressure of each part of the
casing.
o 2.1.11 Control of the Sound pressure level (SPL) of all
equipment furnished shall be a joint effort of the purchaser 2.2.5 Radially and axially Split casings shall use a metal-
and the vendor. Unless otherwise specified, the equipment to-metal joint (with a suitable joint compound) that is tightly
furnished by the vendor shall conform to the requirements
of API Standard 615 and to the maximum allowable Sound
pressure level specified by the purchaser.
2.2.6 Esch axially Split casing shall be sufficiently rigid
l 2.1.12 Electrical components and installations shall be
to allow removal and replacement of its upper half without
suitable for the area classification (class, group, and division)
disturbing rotor-to-casing running clearances.
specified by the purchaser on the data sheets and shall meet
SPECIAL-PURPOSE STEAM ‘T~RBINES FOR REFINERY SERVICES
2.2.7 Casings and supports shall be designed to have suffi- average roughness (R,). Hold-down or foundation bolt holes
shall be drilled perpendicular to the mounting surface or sur-
cient strength and rigidity to limit any Change of shaft align-
ment at the coupling flange, caused by the worst combination faces and spot faced to a diameter three times that of the hole.
of allowable pressure, torque, and piping forces and moments,
to 0.002 inch (50 micrometers). Supports and alignment bolts
2.3 Casing Appurtenances
shall be rigid enough to permit the machine to be moved by
the use of its lateral and axial jackscrews.
2.3.1 NOZZLES AND DIAPHRAGMS
2.2.8 Jackscrews, guide rods, and casing alignment dowels
2.3.1.1 All nozzle rings shall be replaceable. Nozzle rings
shall be provided to facilitate disassembly and reassembly.
welded to the case are acceptable only when approved in ad-
When jackscrews are used as a means of parting contacting
Vance by the purchaser.
faces, one of the faces shall be relieved (counterbored or
2.3.1.2 All other stationary blading shall be mounted in
recessed) to prevent a leaking joint or an improper fit caused
replaceable diaphragms or blade carriers. Nozzles or blad-
by marring of the face. Guide rods shall be of sufflcient length
ing welded to the diaphragm is preferred (see 2.11.3.1).
to prevent darnage to the internals or casing studs by the cas-
ing during disassembly and reassembly. Lifting lugs or eye-
. 2.3.2 SENTINEL WARNING VALVE
bolts shall be provided for lifting only the top half of the
When specified, a sentinel warning valve shall be supplied
casing. Methods of lifting the assembled machine shall be
on the turbine casing. It shall be set at 5 pounds per Square
specified by the vendor.
inch gauge (0.35 bar gauge) on condensing turbines. For non-
2.2.9 The steam ehest and casing shall be provided with
condensing turbines it shall be set at either 10 pounds per
connections to ensure complete drainage. Drain connections
Square inch gauge (0.7 bar gauge) or 10 percent above the
shall be 1 inch minimum pipe size.
maximum exhaust pressure, whichever is greater.
2.2.10 Tapped holes in pressure Parts shall be kept to a
Note: A sentinel warning valve is only an audible warning device and is
minimum. To prevent leakage in pressure sections of casings,
not a pressure-relieving device.
sufficient metal, in addition to the allowance for corrosion,
shall be left around and below the bottom of drilled and tapped
2.4 Casing Connections
holes. Through bolting is preferred in areas of the casing
where the temperature may exceed 775 “F (413 “C).
l 2.4.1 Inlet and outlet connections shall be flanged or
machined and studded, oriented as specified in the data sheets,
2.2.11 Studded connections shall be furnished with studs
and suitable for the maximum allowable working pressure
installed. Blind stud holes should be drilled only deep enough
at the maximum allowable temperature.
to allow a preferred tap depth of 1% times the major diameter
of the stud; the first 1% threads at both ends of each stud
2.4.2 Connections welded to the casing shall meet the ma-
shall be removed.
terial requirements of the casing, including impact values,
rather than the requirements of the connected piping (see
2.2.12 Bolting shall be furnished as specified in 2.2.12.1
2.11.3.6).
through 2.2.12.4.
2.4.3 Casing openings for piping connections shall be at
2.2.12.1 The details of threading shall conform to ANSI
least % inch nominal pipe size and shall be flanged or
BI.1.
machined and studded. Where flanged or machined and stud-
Studs are preferred to cap screws.
2.2.12.2
ded openings are impractical, threaded openings in sizes, %
inch through 1% inches nominal pipe size are permissible.
2.2.12.3 Adequate clearance shall be provided at bolting
These threaded openings shall be installed as specified in
locations to permit the use of socket or box wr 2.4.3.1 through 2.4.3.7.
2.2.12.4 Socket-, slotted-nut-, or Spanner-type bolting shall
2.4.3.1 A pipe nipple, preferably not more than 6 inches
not be used unless specifically approved by the purchaser.
(152 millimeters) lang, shall be screwed into the threaded
2.2.12.5 ANSI B31.3, Paragraph 309, shall govern the ma-
opening.
terial limits for pressure bolting based upon the actual bolt-
2.4.3.2 Pipe nipples shall be a minimum of Schedule 160
ing temperature. Nuts shall conform to ASTM A 194, Grade
seamless for sizes 1 inch and smaller and a minimum of
2H (or ASTM A 307, Grade B, casehardened, where space
Schedule 80 for a size of 1% inches.
is limited).
2.2.13 The machined finish of the mounting surface shall 2.4.3.3 The pipe nipple shall be provided with a welding-
be 125-250 microinches (3.2-6.4 micrometers) arithmetic neck or socket-weld flange.
9-
API STANDARD 612
Tat& 1 -Finish Requirements for
2.4.3.4 The nipple and flange materials shall meet the re-
Flange Contact Surfaces
quirements of 2.4.2.
2.4.3.5 The threaded connection shall be seal welded in Finish (R,)
accordance with 3.6.1.8.
Microinches
Flange Type Service Micrometers
2.4.3.6 Tapped openings and bosses for pipe threads shall
Ring joint All <63 1.6
conform to ANSI B16.5.
03-125
Vacuum 1.6-3.2
2.4.3.7 Pipe threads shall be taper threads conforming to
Fiat and
ASME B1.20.1.
raised face All 125-500 3.2- 12.7
2.4.8 All of the purchaser’s connections shall be accessi-
2.4.4 Openings for pipe sizes of l%, 2%, 31/2, 5, 7, and
ble for disassembly without the machine being moved.
9 inches shall not be used.
2.4.9 Unless otherwise specified, Pipe-flange gaskets shall
2.4.5 Tapped openings not connected to piping shall be
be spiral-wound metal or metal-jacketed with nonhazardous
plugged w*ith solid steel plugs furnished in accordance with
filier for steam temperatures above 500°F (260°C) or steam
ANSI B16.11. Plugs that may later require removal shall be
pressures above 400 pounds per Square inch gauge (28 bar
of corrosion-resistant material. Threads shall be lubricated.
gauge). The manufacturer’s Standard gasket tan be used be-
Tape shall not be applied to threads of plugs inserted into oil
low these limits.
passages. Plastic plugs are not permitted.
2.4.6 Flanges shall conform to ANSI B16.1, B16.5, or B16.42
2.5 External Fortes and Moments
as applicable, except as specified in 2.4.6.1 through 2.4.6.6.
Turbines shall be designed to withstand external forces and
2.4.6.1 Cast iron flanges shall be flat faced and shall have
moments at least equal to the values calculated in accordance
a minimum thickness of Class 250 per ANSI B16.1 for sizes
with NEMA SM 23. In some cases, these allowable forces
8 inches and smaller.
and moments tan be increased after considering such fac-
tors as location and degree of turbine support, nozzle length
2.4.6.2 Flat-faced flanges with full raised-face thickness
and degree of reinforcement, and casing configuration and
are acceptable on cases other than cast iron.
thickness.
2.4.6.3 Flanges that are thicker or have a larger outside
diameter than that required by ANSI are acceptable.
2.6 Rotating Elements
Q 2.4.6.4 For the purpose of manufacturing mating Parts,
2.6.1 ROTORS
when connections larger than those covered by ANSI are sup-
plied, the vendor shall supply turbine flange details to the 2.6.1.1 Rotors (other than integrally forged shatts and disks)
purchaser. When specified, the mating Parts shall be furnished shall be assembled so that movement of the disk relative to
by the vendor. the shafi is prevented when operating at any Speed up to 110
percent of trip Speed at normal temperature.
2.4.6.5 The concentricity of the bolt circle and the bore
of all casing flanges shall be such that the area of the machined
2.6.1.2 Rotors shall be capable of safe Operation at momen-
gasket-seating surface is adequate to accommodate a com-
tary Speeds up to 110 percent of the trip Speed at normal oper-
plete Standard gasket without protrusion of the gasket into
ating temperature.
the fluid flow.
2.6.1.3 The purchaser’s approval is required for built-up
2.4.6.6 The finish of all steel flanges and nozzles shall con-
rotors when blade tip velocities exceed 825 feet per second
form to ANSI B16.5 except for flange finish roughness re-
(250 meters per second) at maximum continuous Speed or
quirements. The arithmetic average roughness (Ra) of flange
when Stage inlet steam temperatures exceed 825 “F (441 “C).
contact surfaces shall conform to the values given in Table
2.6.1.4 Esch rotor shall be clearly marked with a unique
1. Milled flange surfaces are acceptable with the purchaser’s
identification number. The number shall be visible, prefera-
approval;
bly on a shaft end, when the uncoupled rotor is enclosed by
2.4.7 Machined and studded connections shall conform to
the casing.
the facing and drilling requirements of ANSI Bl6.1, B16.5,
e 2.6.1.5 When specified, provisions shall be made for ready
or B16.42. Studs and nuts shall be furnished installed. Con-
access (not requiring removal of the case) for field balanc-
nections larger than those covered by ANSI shall meet the
ing between the bearings. The number and location of these
requirements of 2.4.6.4.
SPECIAL-PURPOSE STEAM TURBINES FOR REFINERY SERVICES
resonant Vibration occurs within the operating range. This
Points shall be mutually agreed upon by the purchaser and
shall be verified by Goodman diagrams or their equivalent.
t.he vendor.
Copies of Campbell and/or Goodman diagrams shall be
2.6.2 SHAFTS
provided to the purchaser. Blades shall be designed to with-
2.6.2.1 Shafts shall be accurately finished throughout their stand Operation at resonant frequencies during normal
entire length and shall be ground at coupling and bearing warmup.
areas and at sealing areas for carbon-ring packing. The fin-
Note: Excitation sources tan include but are not limited to fundamental and
ish of these ground surfaces shall not exceed 32 microinches
first harmonic passing frequencies of rotating buckets and stationary vanes
(0.8 micrometer) R . On built-up rotors, the surface finish upstream and downstream of each blade row, steam passage Splitters, irregu-
larities in vane pitch at horizontal casing flanges, the first four turbine Speed
of areas under the” wheel shrink fit shall not exceed 32
harmonics, casing openings (exhaust or extraction), partial arc diaphragms
microinches (0.8 micrometer) Ra.
or nozzle plates, internal struts and structural members in the inlet and ex-
haust casing or horizontal joints, and meshing frequencies in gear units.
2.6.2.2 The rotor shaft sensing areas to be observed by
radial Vibration probes shall be concentric with the bearing
2.6.3.2 All blades shall be mechanically suitable for oper-
journals. All shaft sensing areas (radial and axial Position)
ation (including for transient conditions) over the specified
shall be free from stencil and scribe marks or any other sur-
Speed range. The vendor shall assume that torque varies as
face discontinuity, such as an oil hole or a keyway. These
Speed squared unless otherwise notified by the purchaser.
areas shall not be metallized, sleeved, or plated. The final
surface finish shall be from 16 to 32 microinches (0.4 to 0.8
micrometer) Ra, preferably obtained by honing or burnish-
2.7 Shaft Seals
ing. These areas shall be properly demagnetized or other-
2.7.1 Outer glands shall be sealed with replaceable laby-
wise treated so that the combined total electrical and
rinth packing unless carbon-ring packing is specified by the
mechanical runout does not exceed the following values:
purchaser.
a. For areas to be observed by radial-Vibration probes, 25
2.7.2 When carbon-ring packing is specified, it shall be
percent of the maximum allowed peak-to-peak Vibration am-
used only when the rubbing Speed at the shaft-sealing sur-
plitude or 0.25 mil (6 micrometers), whichever is greater.
face is less than 160 feet per second (49 meters per second).
b. For areas to be observed by axial-Position probes, 0.5 mil
The number of carbon rings shall be determined by the Service
(13 micrometers).
and venting requirements, with 25 pounds per Square inch
2.6.2.3 Keyways shall have fillet radii conforming to ANSI (1.72 bar) being the maximum average differential pressure
B17.1. per active sealing ring. Springs for carbon packing shall be
nickel-chromium-iron alloy (heat-treated after cold coiling)
2.6.2.4 Shafts shall be protected by corrosion-resistant ma-
or equivalent material. Consideration shall be given to oper-
terial under carbon-ring packing for casing end glands; the
ating steam-temperature variations in establishing cold clear-
manufacturer’s application method, the coating materials
ances for packing rings.
used, and the finished coating thickness shall be stated on
2.7.3 Sealing of interstage diaphragms shall be by replace-
the data sheets.
able labyrinth packing.
2.6.2.5 Shafi ends for coupling fits shall conform to API
Standard 671 (see 3.1.2).
2.7.4 Glands operating at less than atmospheric pressure
shall be designed for admission of steam to seal against air
2.6.2.6 To prevent the buildup of potential voltage, mag-
netism of the rotating element shall not exceed 5 gauss (0.0005 leakage. Piping with relief valve, pressure gauges, regulators,
tesla). and other necessary valves shall be provided to interconnect
the end glands. The piping shall have one common connec-
2.6.3 BLADING
tion to the purchaser’s sealing steam supply. The admission
2.6.3.1 For each blade row, the vendor shall verify by
of sealing steam shall be automatically controlled through-
Campbell diagrams or their equivalent (corrected to actual
out the load range. The normal operating sealing steam sup-
operating temperatures and Speeds) that excitation of in-Phase
ply shall preferably come from a positive pressure section
tangential, out-of-Phase tangential, axial, torsional, and any
of the turbine.
other high-response modes by multiples of up to 15 times run-
ning Speed, by nozzle. passing frequency, and by twice noz- 2.7.5 A separate vacuum device shall be furnished to re-
zle passing frequency does not occur within the specified duce external leakage from the glands and possible contami-
operating Speed range. If this is not feasible, blade-stress nation of the bearing oil (see 3.5). The device shall be
levels developed in any specified driven-equipment opera- mounted and connected when specified. Appendix B Shows
tion shall be low enough to ensure trouble-free Operation if a typical gland vacuum System.
11.
8 API STANDARD 612
2.7.6 All piping and components of shaft seal and vacuum the purposes of this Standard, a critically damped System is
Systems shall be sized for not less than 300 percent of the one in which the amplification factor is less than 2.5.
calculated new clearance leakage.
2.8.1.4 Critical Speeds shall be determined analytically by
means of a damped unbalanced rotor response analysis and
2.8 Dynamits (See Appendix C)
shall be confirmed by test-stand data.
2.8.1 CRITICAL SPEEDS
2.8.1.5 An exciting frequency may be less than. equal to,
2.8.1.1 When the frequency of a periodic forcing phenome-
or greater than the rotational Speed of the rotor. Potential ex-
non (exciting frequency) applied to a rotor-bearing support
citing frequencies considered in System design shall include
System corresponds to a natura1 frequency of that System, the
but are not limited to the following sources:
System may be in a state of resonance.
a. Unbalance in the rotor System.
2.8.1.2 A rotor-bearing support System in resonance will
b. Oil-film instabilities (whirl).
have its normal Vibration displacement amplified. The mag-
c. Internal rubs.
nitude of amplification and the rate of Phase-angle Change
d. Blade, vane. nozzle, and diffuser passing frequencies.
are related to the amount of damping in the System and the
e. Gear-tooth meshing and side bands.
mode shape taken by the rotor. .
f. Coupling misalignment.
g. Loose rotor-System components.
Note: The mode shapes are commonly referred to as the first rigid (transla-
h. Hysteretic and friction whirl.
tory or bouncing) mode, the second rigid (conical or rocking) mode. and
the (first. second. third, . . . . 11th) bending mode.
i . Boundary-layer flow separat ion.
j. Acoustic and aerodynamic Cross-coupling forces.
2.8.1.3 When the rotor amplification factor (see Figure 1),
k. Asynchronous whirl.
as measured at the Vibration probe, is greater than or equal
2.8.1.6 Resonances of support Systems within the vendor’s
to 2.5, that frequency is called critical and the correspond-
operat-
scope of SUQD~V shall not occur within the specified
ing shaft rotational frequency is called a crifical specd. For
Operating
CRE
- 1
I
I
Speeds
I
’ SM
SM
1 ‘-
+-T+
I
s?
I 1
.- i
5 ; I
.-
’ I
F
N N
Nd mc en
Revolutions per minute
= Rotor 1 st critical, Center frequency, cycles per minute.
Ncl
N = Critical Speed, nth.
cn
N = Maximum continuous Speed, 105 percent.
mc
= Initial (lesser) Speed at 0.707 x peak amplitude (critical).
= Final (greater) speed at 0.707 x peak amplitude (critical).
N2
= Peak width at the half-power Point.
N,-N,
AF = Amplification factor
Ncl
-
- -
N2-Nl
SM = Separation margin.
CRE = Critical response envelope.
= Amplitude at N,l.
Ac1
A = Amplitude at Ncrr
cn
Note: The shape of the curve is for iilustration only and does not necessarily represent any
actual roter response Plot.
Figure 1 -Rotor Response Plot
ISO ‘I0437:‘!993(E)
ing Speed range or the specified Separation margins, unless
(1)
the resonances are critically damped.
2.8.1.7 The vendor who is specified to have unit responsi-
In SI units, this translates to:
bility shall determine that the drive-train critical Speeds (ro-
tor lateral, System torsional, blading modes, and the like) are
compatible with the critical Speeds of the machinery being
L, = 25.4JF
supplied and that the combination is suitable for the speci-
fied operating Speed range, including any starting-Speed de-
Where:
tent (hold-point) requirements of the train. A list of all
undesirable Speeds from zero to trip shall be submitted to
L = Vibration limit (amplitude of unfiltered Vibration),
1’
the purchaser for his review and included in the instruction
in mils (millimeters) peak to peak.
manual for his guidance (see 5.2.5.2).
N= operating Speed nearest the critical of concern, in
revolutions per minute.
2.8.2 LATERAL ANALYSIS
This Unbalance shall be no less than two times the un-
2.8.2.1 The vendor shall provide a damped unbalanced re-
balance limit specified in 2.8.5.2. The Unbalance weight or
sponse analysis for each machine to assure acceptable am-
weights shall be placed at the location or locations within
plitudes of Vibration at any Speed from zero to trip.
the bearing span that have been analytically determined to
affect the particular mode most adversely (for example, at
2.8.2.2 The damped unbalanced response analysis shall in-
mid span for translatory modes, or near both ends and 180
clude but shall not be limited to the following considerations:
degrees out of Phase for conical modes). For bending modes
a. Support (base, frame, and bearing-housing) stiffness, mass,
with maximum deflections at the shaft’s ends, the amount
and damping characteristics, including effects of rotational
of Unbalance shall be based on the overhung mass rather than
Speed Variation. The vendor shall state the assumed support
the static bearing loading.
System values.
c. Modal diagrams for each response in Item b above, in-
b. Bearing lubricant-film stiffness and damping changes due
dicating the Phase and major-axis amplitude at each coupling
to Speed, load, preload, oil temperatures, accumulated as-
engagement plane, the centerlines of the bearings, the loca-
sembly tolerantes, and maximum to minimum -clearances.
tions of the Vibration probes, and each seal area throughout
C. Rotational Speed, including the various starting-Speed de-
the machine. The minimum design diametral running clear-
ten& operating Speed and load ranges (including agreed- upon
ante of the Seals shall also be indicated.
test conditions if different from those specified), trip Speed,
d. For the purposes of the shop verification test (see 2.8.3),
and toast-down conditions.
an additional plot of a test Unbalance, as specified in Item
d. Rotor masses, including the mass moment of coupling
b above (based on static bearing loading for rigid modes or
halves, stiffness, and damping effects (for example, accumu-
based on overhung mass for bending modes). This test weight
lated fit tolerantes, fluid stiffening and damping, and frame
shall be at least two times and no more than eight times the
and casing effects).
Unbalance limits specified in 2.8.5.2 and shall be placed at
e. Asymmetrical loading (for example, partial arc admission,
a location determined by the vendor.
gear forces, side streams, and eccentric clearances).
e. When specified, a stiffness map of undamped rotor re-
sponse from which th
...