Engineering Standard

SAES-K-402 30 April 2012

Centrifugal Compressors
Document Responsibility: Compressors, Gears and Steam Turbines Standards
Committee

Saudi Aramco DeskTop Standards

Table of Contents

1 Scope............................................................ 2
2 Conflicts and Deviations................................ 2
3 References.................................................... 2
4 Design........................................................... 4
5 Installation................................................... 15
6 Shop Testing and Inspection....................... 16
7 Field Testing................................................ 17
8 Life Cycle Cost Evaluation.......................... 17

Previous Issue: 11 August 2009 Next Planned Update: 30 April 2017

Revised paragraphs are indicated in the right margin Page 1 of 18
Primary contact: Khateeb, Eyad Mohammed on 966-3-8809704

Copyright©Saudi Aramco 2012. All rights reserved.

Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

1 Scope

1.1 This Standard covers the minimum mandatory requirements governing the
design and installation of centrifugal compressors in process air or gas service.
This Standard may not be attached to or made part of purchase orders.

1.2 Centrifugal compressors in utility air service shall comply with Specification
31-SAMSS-006 and are excluded from the requirements of this Standard.

1.3 Compressor vendors shall be given a minimum of eight (8) weeks for the
preparation of bids/proposals after receiving the official request for quotation.

2 Conflicts and Deviations

2.1 Any conflicts between this Standard and other Saudi Aramco Engineering
Standards (SAESs), Materials System Specifications (SAMSSs), Standard
Drawings (SASDs) or industry standards, codes, and forms shall be resolved in
writing by the Company or Buyer Representative through the Manager,
Consulting Services Department, Saudi Aramco, Dhahran.

2.2 Direct all requests to deviate from this Standard in writing to the Company or
Buyer Representative, who shall follow internal company procedure SAEP-302
and forward such requests to the Manager, Consulting Services Department,
Saudi Aramco, Dhahran.

3 References

Material or equipment supplied to this Standard shall also comply with applicable
sections of the latest edition of the references listed below or in the body of this
document.

3.1 Saudi Aramco References

Saudi Aramco Engineering Procedure

SAEP-302 Instructions for Obtaining a Waiver of a
Mandatory Saudi Aramco Engineering
Requirement

Saudi Aramco Engineering Standards

SAES-B-058 Emergency Isolation, Shutdown and
Depressurization
SAES-G-116 Field Cleaning and Flushing of Lube/Seal Oil

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
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SAES-J-700 Control Valves

SAES-L-350 Construction of Plant Piping

Saudi Aramco Materials System Specifications

01-SAMSS-017 Auxiliary Piping for Mechanical Equipment
31-SAMSS-001 Centrifugal Compressors
34-SAMSS-625 Vibration, Axial Position and Bearing
Temperature Monitoring Systems

Saudi Aramco Forms and Data Sheets

SA-2812 & Centrifugal Compressors
SA-2812-M
SA-7305 Equipment Noise Data Sheet

Life Cycle Cost Sheets

LCC-005 Centrifugal Compressor
LCC-006 Motor Driven Centrifugal Compressor

Saudi Aramco Library Drawings

DC-950041 Pressure Indicators and Switches, Panel or Wall
Mounted - Instrument Piping Details
DC-950061 Instrument Piping Details, Flow Meter
Installations, Gas and Vapor Service
(Non-Corrosive)
DC-950062 Instrument Piping Details, Flow Meter
Installations, Gas and Vapor Service
(Corrosive)

3.2 Industry Codes and Standards

American Petroleum Institute

API STD 617 Centrifugal Compressors for Petroleum,
Chemical, and Gas Service Industries
API RP 686 Recommended Practice for Machinery Installation
and Installation Design

American Society of Mechanical Engineers

ASME PTC 10 Power Test Code for Compressors and Exhausters

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

4 Design

4.1 General

4.1.1 Centrifugal compressors in process air or gas service shall comply with
31-SAMSS-001.

4.1.2 The Normal operating point shall be stated in the datasheet and shall be
the performance requirement at which the machine will operate most of
the time (for example, Summer conditions). Other operating points, if
necessary, may also be stated in the datasheet if the machine will be
required to operate under these conditions based on validated process
data or simulations. The Rated point shall not be specified in the
datasheet by the Purchaser (unless approved by the Compressors, Gears
& Steam Turbines Standards Committee Chairman) but shall be
selected by the compressor manufacturer based on the operating points
specified in the datasheet. Over-sizing the compressor and the use of
over-design margins are not allowed.

4.1.3 Unless otherwise approved by the Standards Committee Chairman, a

single-lift packaged unit shall be specified, with the compressor, gear
and driver mounted on a single baseplate completely aligned, piped
and wired under controlled conditions at the point of manufacture.
The oil system shall be separated from this single-lift package. If the
compression train cannot be accommodated on a single baseplate, a
segmented skid (e.g., joint by bolting to form a single skid) may be
used to minimize site work.

4.1.4 Unit responsibility for the entire equipment train (including

compressor, driver, gear, auxiliary systems,…etc.) shall be assigned to
the compressor manufacturer.

4.1.5 When mezzanine mounting is used, the piping connections shall be

bottom mounted.

4.16 If seawater cooling is to be used, an inlet design temperature of 35°C

(95°F) shall be used.

4.1.7 Unless otherwise specified, the equipment shall be designed for

outdoor installation in a desert area, with relative humidity from zero
to 100% (condensing) and ambient temperatures from 0°C to 50°C
(32°F to 120°F). Metal temperature can reach 70°C (158°F) when
exposed to direct solar radiation.

Additionally, equipment which is not enclosed or hermetically sealed

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

and is situated offshore or near shore (i.e., within ½ km of the

shoreline) shall be protected against failure due to windborne seawater
spray and the accumulation of wetted salts.

4.2 Noise

New equipment should be designed not to generate noise in excess of 90 dB(A)

at a distance of one meter. If this noise level limit cannot be met, the Project
Manager shall submit a letter for concurrence to Environmental Protection
Department with a completed Equipment Noise Data Sheet Form SA-7305.

4.3 Shaft Seals

4.3.1 Seal gas shall be free from condensation and polymerization and shall
be conditioned via a filtration system and pressure reduction provided
by either the seal vendor or the compressor vendor. If the process gas
is dirty, seal gas shall be taken from an external clean and dry source.
The actual supply location shall be determined based on gas
temperature, pressure and cleanliness requirements for the seal and
shall be the joint responsibility of the Vendor and Saudi Aramco.
In all cases, an external clean and dry seal gas must be provided by the
Contractor during compressor startup and shutdown, unless otherwise
approved by the Compressors, Gears & Steam Turbines Standards
Committee Chairman.

4.3.2 The seal gas system provider must show on phase maps, for all seal gas
supply compositions and conditions, that the seal gas will be a
minimum of 15°C (27°F) above condensation (dew point) when
expanded down to the secondary seal vent pressure while accounting
for the Joule–Thomson cooling effect. This may require adding
heaters to the seal gas conditioning system to ensure condensation is
avoided under all conditions.

4.3.3 Except for air services, a positive internal gas pressure at the seals shall
be maintained under all start-up and operating conditions.

4.4 Magnetic Bearings

The use of an active magnetic bearing system for the compressor and driver shall
be considered, based on an economic evaluation, when the lube oil system can be
totally eliminated, resulting in a “dry” train. This will typically occur when the
driver can be an expander, a variable speed motor, or a turbine. The magnetic
bearing system shall be designed per the requirements of 31-SAMSS-001.
Rejection of any proposal, which can meet this criterion, requires the approval of
the Compressors, Gears & Steam Turbines Standards Committee Chairman.

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

4.5 Drivers

Specified power margins for drivers shall apply to newly purchased equipment
only. Re-rate proposals reducing the power margin to meet changed process
conditions shall be submitted through the Company or Buyer Representative for
review and approval by the Compressors, Gears & Steam Turbines Standards
Committee Chairman. Motor starting torque versus compressor suction throttled
torque demand at site conditions, shall be reviewed in all cases by the Vendor
and Consulting Services Department to verify start up capabilities of the train.
The start-up capabilities of fixed speed motor driven trains shall be verified in
writing by the compressor Vendor and motor Vendor for any train with a normal
suction pressure below 50 psig.

4.6 Baseplates

4.6.1 Baseplate design shall be reviewed for good access to all components
for operation and for maintenance. This applies particularly to
packaged units where accessibility of valves, reservoirs, pumps, etc., is
of prime importance. A 3-D CAD model or large detailed 3-D
drawings shall be provided by the compressor Vendor to permit review
of piping, conduit runs, location of valves, etc.

4.6.2 Three (3) point supported baseplates shall be considered for offshore
platforms where significant deck deflection is expected.

4.7 Control and Instrumentation

4.7.1 Controls and instrumentation shall be adequate to control the

compressor at all specified operating conditions. The control method
shall be determined by the process startup, shutdown and normal
operation requirements. For variable speed drives, the primary process
control shall be by means of variable speed operation of the
compressor. For compressors with variable guide vanes, the primary
process control shall be by means of varying guide vanes angle.

4.7.2 Suction throttling shall not result in sub-atmospheric pressure and risk
of air ingestion into the process stream. The valve disc must, therefore,
be undercut. Mechanical travel stops are not permitted. The suction
throttling control valve (when required to control the suction pressure
or the motor BHP) shall be located upstream of the recycle line tie-in
to the compressor suction piping.

4.7.3 The anti-surge control system shall automatically maintain a flow

through the compressor at a safe margin in excess of the surge flow
during all operating conditions, whether the controller is in automatic

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

or manual mode, by means of an anti-surge recycle valve and recycle

line. The anti-surge system shall always be required except in the case
of a recycle compressor application. In this case, the need for a recycle
loop shall be evaluated by the Engineering Designer, the Plant
Engineering Manager and the Rotating Equipment Unit of Consulting
Services Department.

4.7.4 The selection of recycle valves shall be reviewed and approved by the
Process and Control Systems Department. Recycle valves shall meet
the requirements of SAES-J-700 and shall be selected as follows:
a. The valve trim characteristic shall be equal percentage or linear
(as recommended by the compressor or control system vendor);
b. The response time from fully closed to fully open shall be a
nominal 2 seconds or less (accomplished by using volume
boosters and close tubing connections, in accordance with the
valve vendor's recommendations);
c. The ratio of the maximum selected valve capacity to the valve
capacity demanded by the compressor surge curve (worst case
scenario) shall fall between 1.8 and 2.2.

4.7.5 For compressor casings in series or parallel operation, individual anti-

surge recycle lines shall be provided for each compressor casing.
For compressor with multiple inlets or outlets, an individual recycle
line for each section shall be provided as necessary.

4.7.6 For applications where quench valves are used to cool hot recycle
gases, the valves must be installed as close as practical to their
downstream mixing tees. The mixing tees should be installed just
upstream of the suction knock-out drum, or may be located on the
recycle line downstream of the recycle valve if approved by the
Rotating Equipment Unit of Consulting Services Department and by
Process and Control Systems Department.

4.7.7 The final design of anti-surge and performance control system shall be
reviewed in detail for each individual application by the compressor
vendor and Rotating Equipment Unit of Consulting Services Department
and by the Process Control Division of Process and Control Systems
Department. A hot gas bypass (hot recycle) shall not be used unless
approved by the by the Compressors, Gears & Steam Turbines
Standards Committee Chairman. A transient, dynamic process
simulation shall be performed for each compressor system by the
Contractor, to confirm the functionality of the compressor system under

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

all start-up, operating and shutdown conditions. During machine

shutdown, the simulation shall show that surge does not occur above
75% speed. The Recycle or Anti-Surge valve opening stroke time used
in the transient dynamic simulation shall be 2 seconds, excluding all
delays (e.g., dead time).

4.8 Piping, Valves and Inter-stage Cooling

4.8.1 Contractor shall be responsible and shall consult the Compressor

Vendor machinery and piping engineers in order to confirm and
document in conjunction with control system engineers or control
systems vendors that the following piping and hydraulic parameters are
satisfied for proper compressor operation, control and protection:
a. Lag (dead) time is kept to an absolute minimum by minimizing
recycle gas piping captured volume, (i.e., the volume of gas
between the compressor discharge port, the discharge check
valve and the recycle valve).
b. Recycle piping must be self-draining (i.e., the piping is sloped
downward on both sides of the surge control valve).
c. The anti-surge recycle line shall join the compressor discharge on
a piping tee branch, located as close as possible to the compressor
discharge. The anti-surge recycle line shall join the compressor
suction line at the suction knock-out drum or suction piping
upstream or downstream of knock-out drum in a 45° angled
connection directing the recycle flow towards the compressor.
d. A non-slam internal-spring assisted type check valve shall be
located in the discharge piping of each compressor section
immediately downstream of the piping tee for the anti-surge
recycle line.
e. Compressor inter-stage coolers and after coolers shall be located
as close to the compressor discharge as possible, using minimum
connecting piping volume.

4.8.2 Compressor auxiliary piping shall be in accordance with

01-SAMSS-017.

4.9 Compressor Field Sensors and Instrumentation:

4.9.1 Field instrumentation shall comply with paragraphs 4.9.2 to 4.9.5.

4.9.2 The control systems designer in conjunction with the compressor

manufacturer shall be responsible for validating and confirming the type,

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

and range of all process sensors and instrumentation used to monitor and
control the compressor based on the following requirements:
a. Low loss venturi meters are the preferred means of flow
measurement. However, orifice meters may be used for flow
measurement. The minimum output signal from the flow (dP)
transmitter at the actual surge limit line and minimum compressor
speed shall not be less than 10% of the transmitters' range.
b. Smart transmitters shall be used to measure all process variables
except for suction flow measurements that are used as inputs to
anti-surge algorithms. Process activated switches shall only be
used within the compressor skid on an exception basis when a
transmitter is incapable of performing the same function. Process
activated switches must be fail safe devices, incorporating
hermetically sealed or encapsulated switch elements and
configured to de-energize to trip.
c. Transmitters used to measure either suction or discharge flow must
have a response time of 100 milliseconds or less (rise time from
process measurement to 63% of transmitter calibrated range).
d. Transmitters used to measure suction or discharge pressure,
temperature or differential pressure (except for flow
measurement) shall be ‘smartʼ digital devices, compensated for
ambient temperature and static pressure changes. Suction
temperature sensors and transmitters shall be located in the
suction piping downstream of the suction knock-out drum and
any piping tees. Discharge temperature sensors and transmitters
shall be located close to the compressor discharge flange and
upstream of any discharge cooler.

4.9.3 Vibration detectors, key phasors, shaft axial position detectors, and
bearing temperature detectors and their associated monitors shall
comply with 34-SAMSS-625 and 31-SAMSS-001. As a minimum,
each compressor shall be fitted with two (X & Y) radial relative
displacement (non-contacting) sensors, located at each journal bearing,
two axial thrust position probes (one axial thrust probe for Integrally
Geared Compressors) and one key phasor. Settings for alarm and
shutdown shall be recommended by the compressor and driver vendors
and, where applicable, the gear vendor.

4.9.4 Process connections for process pressure indicators, switches and

transmitters should be in general compliance with drawing DC-950041.

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Commentary Note:

Where possible, impulse lines between process taps and transmitters

shall be close coupled.

4.9.5 Process connections for differential pressure transmitters should be in

general compliance with drawing DC-950061 and DC-950062.
Commentary Note:

Where possible, impulse lines between primary sensors and

transmitters shall be close coupled and self draining.

4.10 Compressor Performance and Anti-Surge Control Requirements

4.10.1 All centrifugal compressors, with the exception of recycle compressors

where an anti-surge loop may not be required (paragraph 4.9.3), shall
have a pre-engineered, stand-alone or compressor train integrated, fail-
safe and fault tolerant digital anti-surge and performance control
system (a DCS anti-surge controller is not acceptable). This anti-surge
and performance control system shall optimize compressor operation
and load, but act to decrease network resistance whenever the
compressor operating point moves too close to its pre-defined surge
limit. The decrease in network resistance shall be accomplished by
modulating a properly sized recycle or spill-back valve which has a
nominal stroking time from the closed to full open position of
2 seconds. Anti-surge controllers must execute their respective
algorithms within 100 milli-seconds (which includes sampling inputs,
executing logic, and initiation of output change). The sampling time
shall be less than 40 milli-seconds.

4.10.2 Each compressor casing or section provided with a recycle line

(paragraph 4.7.5) shall have an anti-surge control system. Anti-surge
control systems for multiple stages/sections may reside in a single
controller.

4.10.3 Where compressors are operated in parallel arrangements, a load

sharing controller shall function to distribute the load by keeping each
machine equidistant from its surge curve or surge control margin.

4.10.4 The control system shall be able to respond to all required process
parameters and dynamics (i.e., startup, normal operation, normal
shutdown, and emergency shutdown) in automatic mode. The control
system shall satisfy the compressor manufacturer's operational
requirements for performance and surge avoidance whether in
automatic or manual modes of operation.

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4.10.5 Anti-Surge Controller Action

4.10.5.1 The anti-surge controller shall be capable of building,

constructing or inputting a surge curve (d/P, pressure ratio,
or polytropic head vs. suction flow), based on the
compressor manufacturer's predicted surge curve data, and
maintaining control at a user selectable surge control line
which usually is 10% margin away from the actual
operating surge curve of the compressor in its safe
operational zone.

4.10.5.2 The anti-surge controller shall be capable of incorporating

incipient surge detection logic, or functionally similar types
of detection schemes to evaluate potential instability in
compressor operation. Such schemes should be capable of
initiating action to drive the recycle valve towards its full
open position upon validation of an incipient surge
condition. Several potential schemes or combinations
thereof are rate of change of flow or pressure.

4.10.5.3 The compressor's actual surge limit line shall be determined

for one or more operational conditions during factory
acceptance or site acceptance testing of the compressor.
Based on actual process testing and process parameters, the
surge control line shall be reconstructed within the anti-
surge controller and the surge control margin revalidated.

4.10.5.4 The anti-surge controller shall act to maintain the recycle

valve in a closed position during normal operation and
normal loads.

4.10.5.5 In the event of abnormal loads or process upsets which

cause the compressor's operating point to rapidly approach
or cross over the surge control line towards its actual surge
curve, the controller shall measure the rate of change in the
operating point, and respond by driving the recycle valve to
its full open position.

4.10.5.6 Control strategies for safe operating regions shall include

proportional, integral and/or derivative (if necessary).
Control strategies for potentially unsafe regions (i.e.;
between the surge control line and actual surge curve) shall
include non-linear or exponential gain, open loop (step)
response or similar strategies.

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4.10.5.7 Control action for all algorithms, including transfer from

automatic to manual, and back to automatic, shall be
smooth and bumpless.

4.10.5.8 Recycle valve shall follow a user configurable closure rate

which is nominally in the range of 30 to 60 seconds.

4.10.5.9 Anti-surge controllers shall be configured to initiate an

alarm and increment a surge counter when an actual surge
cycle has been detected. The surge count accumulator
contents shall be protected from being accidentally reset by
password, keylock or similar methods of security.

4.10.5.10 The anti-surge control algorithms shall incorporate

functionality to automatically evaluate operation of the
controller at or near the surge control line and to
automatically increase the surge control margin to prevent
unstable compressor operations. Automatic adjustments of
the surge control margin shall be alarmed to the operators.
The system shall maintain a record of the previous margin
settings on hard-disk or non-volatile memory.

4.10.5.11 Anti-Surge and Performance Controller Algorithms and

Configuration
a. The anti-surge and performance control system shall
consist of one or more controllers with a pre-
engineered menu of algorithms designed to perform
surge control, coordination, load-sharing and de-
coupling between multiple sections or multiple
compressors in series or parallel configurations.
Commentary Note:

Individual control algorithms for multi-stage or

multiple compressors may be installed within a single
multifunction or programmable controller, provided it
incorporates a fault-tolerant, backup scheme (e.g.,
dual or triplicated controllers and I/O) with bumpless
transfer. All controllers shall incorporate safety and
security features that prevent their unauthorized
alteration.

b. The pre-engineered menu of algorithms shall as a

minimum consist of the following, applicable to all
compressor stages:

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1. Suction flow (volumetric) vs. compressor head

or dP (Discharge Pressure - Suction Pressure).
2. Suction flow vs. compressor pressure ratio
(outlet/inlet pressure).
3. Suction flow vs. compressor polytropic head.
4. Fall-back strategies for constant or variable
speed compressors with fixed or variable gas
composition and suction flow measurement:
i. Upon failure of or invalidation of suction
flow transmitter signals, the controller
shall revert to either minimum recycle flow
or a fixed suction flow.
ii. Upon failure of or invalidation of the
suction pressure transmitter signal, the
controller shall revert to minimum recycle
flow.
iii. Upon failure of or invalidation of the
discharge pressure transmitter, the
controller shall revert to a specified
compression ratio.
iv. Upon failure of or invalidation of the
compressor rotational speed input, the
controller shall revert to a fixed speed.
v. Loss of or invalidation of any inter-stage
suction flow measurement will result in an
adjacent stage's flow computation being
used for control purposes.
5. Performance controller algorithms shall include
features for automatic startup, staging, and
shutdown of the compressor(s); including
necessary control loop de-coupling, load sharing
and compressor balancing arrangements.
c. The anti-surge control system shall be designed such
that it accounts for the following characteristics and
constraints of compressor, piping and control system:

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1. Compressor performance curves, based on

process parameters (fluid data), at the most
severe operating region (i.e., startup, shutdown,
minimum flow, or full recycle);
2. Compressor driver characteristics and speed
feedback devices (e.g., turbine or electric motor
- constant speed or variable speed);
3. Recycle (pipe) volumes (minimum acceptable);
4. Recycle gas cooling or required temperature
quenching;
5. Location of the compressor discharge check
valve;
6. Recycle valve sizing, characteristics, response
time, and fail safe modes;
7. Incipient surge algorithm (paragraph 4.10.5.2);
8. Suction measurement element, transmitter range
and response time;
9. Compressor suction and discharge, pressure and
temperature measurement ranges and locations;
10. Fall back strategy(s) upon flow transmitter,
suction or discharge pressure transmitter failure
or fault detection;
11. Bumpless transfer and fallover from primary
controller to backup controller upon the failure
of the primary controller, transfer from
automatic to manual to automatic; with
minimum flow fall-back strategies.

4.10.6 Anti-Surge and Performance Controller Support Software

Supporting software or software tools shall be provided in conjunction

with associated anti-surge and performance controllers which allow
on-line monitoring and real-time display of compressor maps and
which show current operating conditions and limits. This software
shall be capable of initiating data acquisition and archiving critical
compressor operational parameters in real-time at the controller's
sampling rate. The software shall also be capable of performing
critical event archiving, event alarming and multiple trend
building/display.

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4.11 Local and Remote Compressor Instrument Control Panels

Pressure gauges and local control instrumentation, where specified, shall be

mounted on a local gauge board.

5 Installation

5.1 Emergency shutdown and isolation systems shall be provided in accordance

with SAES-B-058 and this section of the standard. Power-operated emergency
isolation block valves shall be located upstream of the suction knock-out (K.O.)
drum and downstream of the discharge K.O. drum (if provided). The recycle
line shall tie-in downstream of the suction isolation valve and upstream of the
discharge isolation valve.
Commentary Note:

Emergency isolation valves shall not be installed within the recycle loop of a
compressor or any of its sections.

5.2 An automatic vent valve, that is actuated via an emergency shutdown (ESD)
signal, shall be located on the suction K.O. drum or on the discharge piping
between the compressor and any power actuated valve.

5.3 If a fire detection system is required, it shall be provide by the project

Contractor. The need for such a system and its specifications and selection shall
be reviewed with Saudi Aramco's Chief Fire Prevention Engineer.

5.4 The installation of the compressor train and its components shall be in
accordance with API RP 686. The compressor skid shall be epoxy grouted fully
beneath the skid, in contact with all load bearing structural members, and
covering the entire surface of the foundation. Additionally, the ingress of any
dirt or liquids into the skid voids shall be prevented.

5.5 All compressor suction piping between the suction drum and the compressor
inlet shall be cleaned by high pressure hydrojetting following fabrication.
All field fabricated piping forming any part of the buffer gas system to
compressor dry gas seals or tertiary shaft seals shall be manually cleaned or
cleaned by high pressure hydrojetting, or chemically cleaned and neutralized.
Lube oil systems shall be cleaned in accordance with SAES-G-116.

5.6 A permanent stainless steel strainer shall be installed, in the compressor suction
line upstream of the pressure sensor used for performance measurements or anti-
surge control. Alternatively, if approved by the by the Compressors, Gears &
Steam Turbines Standards Committee Chairman, a temporary stainless steel
conical strainer of adequate strength designed by the compressor Vendor and
mounted into a drop-out pipe spool may be provided in lieu of the permanent

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strainer. In all cases, the strainer holes shall be 1/8 in. (3 mm) minimum and
shall not be fitted with fine mesh.

5.7 All compressor pressure and temperature sensors used for performance or surge
control monitoring shall be installed at a maximum distance of ten pipe
diameters and a minimum of two pipe diameter from the compressor flanges;
except for suction temperature sensor which shall be installed upstream of the
suction strainer. In addition, pressure measuring points located downstream of
devices that can cause flow disturbance which could result in measurement
inaccuracy, such as valves, orifices, strainers, elbows, shall be at least three pipe
diameters distant from them. Pressure and temperature measuring devices shall
be oriented 90 degrees apart.

5.8 Piping connections to the compressor nozzles shall be made in accordance with
SAES-L-350, taking into account the specific flange fit up and bolting
tolerances. No piping supports or support structure shall be placed over upward
facing compressor nozzles that would restrict access for maintenance of the
complete equipment skid. Each compressor nozzle shall be provided with an
individual, removable, final piping spool. Allowable forces and moments on the
compressor nozzles shall be per API STD 617, when the forces and moments are
resolved to the largest nozzle.

6 Shop Testing and Inspection

6.1 Hydrostatic Tests

Hydrostatic tests shall be required for all pressure containing parts as listed in
the Inspection & Testing Plan (ITP).

6.2 Mechanical Running Test

A mechanical running test shall be mandatory and always witnessed.

6.3 Performance Test

A performance test shall be specified and witnessed for each compressor duty.
For a series of identical units, only one compressor requires performance testing.
Tests shall be in accordance with ASME PTC 10. Tests shall be to Type II
unless otherwise specified. Where rotor instability due to high gas densities
could be encountered, either a Type I test or, as an alternative, Type II test plus a
“Similar Density” test shall be considered. The Rotating Equipment Unit of
Consulting Services Department shall be consulted concerning advisability of
Type I full load, full pressure tests in these circumstances. The extra costs of
such tests, compared to a Type II test, shall be weighed against the cost (and
delay) to correct any mal-performance after the compressors are installed.

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

6.4 String Test

A string test requires the approval of the Compressors, Gears & Steam Turbines
Standards Committee Chairman. The mechanical running test is not required for
the string tested machines.

6.5 Shop Noise Level Test

A noise level shop test shall be conducted for reference only.

7 Field Testing

7.1 Performance Test

As soon as possible after the installation is completed, a field performance test

shall be conducted on the compressor. The performance shall be checked at a
minimum of five points and shall include design, surge and overload points.
For variable speed drivers the test shall be conducted at normal speed.
The vendor shall be present for the test and shall verify that the data is taken in
an acceptable manner.
Commentary Note:

Field test data is subject to inaccuracies of up to 10% due to location and

calibration of critical instrumentation. To minimize these inaccuracies, the
instrumentation should be calibrated and checked just before and just after the
tests. Gas samples should be taken for each test point.

7.2 Mechanical Test

Overall vibration levels in the field shall not exceed 125% of the maximum
factory acceptance limits of API STD 617 when the machine is operating within
its operating range.

7.3 Noise Level Test

The noise level test shall be conducted in the field.

8 Life Cycle Cost Evaluation

Quotations for compressors of 1000 HP and larger shall be evaluated on the basis of a
Life Cycle Cost (LCC). This cost is composed of initial cost of the compressor plus the
present worth of the consumed power cost over an operating period of 20 years.
The Life Cycle Cost of the compressor shall be determined using the life cycle cost
spreadsheet LCC-005 or LCC-006.

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Document Responsibility: Compressors, Gears and Steam Turbines Standards Committee SAES-K-402
Issue Date: 30 April 2012
Next Planned Update: 30 April 2017 Centrifugal Compressors

Revision Summary
30 April 2012 Revised the “Next Planned Update.” Reaffirmed the contents of the document, and reissued
with minor changes.

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