Section 12 — Instruments and Controls

Surge Control Systems

IPE Engineering Practice IPE-EP-12-1-23

Document number: IPE-EP-12-1-23 · Section: 12 — Instruments and Controls

SCOPE

• Compressor Anti–Surge Control requirements shall be supplied in strict accordance with this Practice, and the referenced standards and publications.
• Where special features or improvements over the Practice are required as determined by the Owner, or Owner’s Engineer, these shall be specified and adhered to by the Vendor.
• Vendor shall provide a proposal based on furnishing all necessary control room instruments, documentation and engineering services to provide anti–surge protection for a centrifugal compressor in accordance with the requirements listed below. (All necessary components and equipment which are not mentioned in this specification but which are necessary to form an operating system as described herein, shall be identified and supplied by the Vendor. This includes all hardware and software.)
• Vendor’s compressor control system shall be designed to meet the following control objectives.
• Protect each stage of the compressor from surge.
• Save energy by minimizing recycle flow.
• Any deviation from this Practice must be approved by the procedure described in EP 1–1–3.

2.0 REFERENCES

The following codes and standards shall be considered as part of this Practice. All documents shall be the latest editions in force on the date of issuance of this Practice.

STANDARDS AND PUBLICATIONS

DEFINITIONS

• Contractor - Company or business that agrees to furnish materials or perform specified services at a specified price and/or rate to the Owner.
• Inspector - A Refining Company appointed engineer or inspector.

• Manufacturer - The recipient of a direct or indirect purchase order for materials and/or equipment. In this context, a direct order is one issued to a manufacturer by a contractor or the Owner. An indirect order is one issued to a manufacturer by a vendor (recipient of a direct order) for materials, fabricated components, or subassemblies.
• Owner - Refining Company.
• Owner’s Engineer - A Refining Company appointed engineer.
• Purchaser - The party placing a direct purchase order. The purchaser is the Owner’s designated representative.

VENDOR GENERAL RESPONSE

• The Practice requests technical data. The Vendor shall respond by producing either a special document or, when necessary, by attaching relevant technical data. If documents are attached, the data must be referenced in the response by page number and paragraph number.
• The Vendor may propose alternate system features other than those specified in this document.

• job number and purchase order number shall be identified in all documents.

DESIGN AND MATERIALS

• General
• All instruments shall be calibrated for use with a transmitted signal of 4 to 20 mA DC unless otherwise specified. They shall be capable of being used with ISA S50.1 2U Type (two wire) or 4 (four wire) transmitters.
• Control room type instruments designated at 4 to 20 mA input shall be used with field transmitters and shall be capable of powering 2–wire transmitters. Control room instruments designated as 1–5 V will be parallel wired across the input of another receiver.
• Unless otherwise specified on the Instrument Data Sheets, all instruments shall be miniature type suitable for panel mounting in multiple unit shelves furnished with the instruments.
• All instruments shall have a high input impedance of at least 50,000 ohms at balanced or unbalanced pen scale positions. The receiver shall be suitable for parallel wiring of inputs across a common dropping resistor.
• All instrument cases shall be equivalent to general purpose NEMA Type 1 in accordance with NEMA ICS 6 unless otherwise specified on the Instrument Data Sheets.
• All instruments shall be identified with a permanently attached tag bearing the devices’ item tag number. Identification tag shall be located so as to be visible when the instrument is in its normally installed position.
• Design and materials not specified shall be in accordance with the Manufacturer’s standards. Minimum design shall conform to the National Electrical Code (NEC) (NFPA 70) with applicable listing by either Underwriters laboratories (UL) or Factory Mutual (FM).
• Power supply for the control panel instruments shall be nominal 120 V, 60 Hz, AC.

• Scale windows shall be made of glass or clear plastic.
• Vendor shall prewire and all I/O wiring shall land on terminal blocks on their rack for field wiring. If units must be split, then Vendor shall supply a pre–fabricated cable to attach these units. Field terminations shall not land on controller terminal strips.
• Controllers
• Vendor shall supply dedicated microprocessor–based anti–surge controllers to provide anti– surge control on each stage of the process gas compressor.
• Each anti–surge controller shall be of the multi–loop type and shall be true stand alone instruments. Each controller shall include contact outputs for controller fault, controller auto/manual status. Controller shall open or partially open the anti–surge valve to prevent compressor surge. Controller fault shall also be used to indicate the loss on any analog input signal to the controller. If more than one controller is used, the Vendor shall also provide for communication between controllers.
• The microprocessor–based controller shall:
• Be started up without the assistance of any higher level devices, such as a computer.
• Perform control functions independent of any other function with which it may share intelligence.
• Be field configurable so that control strategies can be charged.
• Retain all control configuration memory in the event of a power failure.
• Each microprocessor–based controller shall have the capability to communicate to a distributed control computer system through an RS232C serial communication link. The link shall allow the DCS system to read certain parameters from each controller and monitor all analog inputs, outputs, and alarm states.
• Vendor shall wire controllers such that the vertical communication to the DCS system shall be through one serial port. If the DCS system interface unit has limitations as to the number of controllers it can interface with, Owner may provide two serial port/DCS interface units.
• Vendor shall be responsible in coordinating controller and DCS system communications interface with the DCS Vendor.
• Controllers shall be of maximum nominal size 3 inch wide by 6 inch high, unless otherwise specified.
• Controllers shall incorporate proportional, integral, derivative actions unless otherwise specified on the Instrument Data Sheets.
• Tuning constants shall be adjustable from the front of the control panel as follows:
• The proportional band from at least 5% to 500%.
• Integral action from at least 0.02 to 100 minutes per repeats.
• Derivative action from at least 0.04 to 20 minutes.
• All controllers shall be furnished with an automatic–manual control unit for “bumpless” transfer from automatic to manual operation and vice versa. Provision shall be included for manual adjustment of the controller output signal with the control mechanism by–passed.

• Controllers shall have readout displaying actual engineering unit. Controllers shall be furnished with an indication of controller output value in percent. Valve position (open–close) shall be clearly identified at each end of output scale.
• When the set point is specified as an electronic input (such as cascade), the mechanism shall be designed to maintain a linear relationship between the value of the setting signal from a primary controller and the value of the set point to secondary controller. The secondary controller shall also be provided with the following switching functions:
• Manual setting of the set point from the secondary controller is isolated from the primary controller.
• Manual adjustment of the secondary controller output signal with the control mechanism by–passed.
• Electronic setting of the set point by a primary controller.
• The secondary controller of a cascade loop shall have a remote/local/manual/auto switch.
• The controller shall be supplied with an anti–reset windup feature to prevent saturating the integral circuit when the controller is off control for long periods. The primary controller of a cascade loop shall have tracking capability (external feedback) to prevent reset windup.
• Controller program execution rate shall be a minimum of 10 times per second.
• Each anti–surge controller shall incorporate a means for automatic and manual operation of its anti–surge control valve. Such operation shall be possible at any time. The controller also shall be configurable so that manual control is only possible when the compressor operating point is outside the region in which the anti–surge controller’s overriding open loop response occurs.
• Instrument Mountings
• All instruments specified for flush mounting shall be furnished with fastenings necessary for flush mounting of the devices to an instrument console.
• Sufficient length of cable shall be furnished to allow complete withdrawal of instruments from the front of rack or panel without interrupting operation.
• Withdrawal of any one instrument shall not interfere with other instruments housed in the same shelf.

PERFORMANCE

• Accuracy
• Accuracy of measurement and set point shall be  0.05% of calibrated span.
• The indicating element of a controller shall not remain stationary when a change greater than 0.1% of the specified range occurs in the input signal.
• The output signal of a controller shall show a response when a change greater than 0.1% of the specified range occurs in the signal applied to the input at a proportional band setting of 100%.
• The effective value of the set point of a controller shall not be affected by adjustments in the width of the proportional band.

6.2 Repeatability

Repeatability shall be  0.1% of calibrated span.

ELECTRICAL SYSTEMS

• Radio Frequency Interference

All electrical equipment shall be protected against radio frequency and electromagnetic interference with a field strength of 30 volts/meter or less over a frequency range of 27 MHz through 1 GHz.

• Electrical Area Classification

Design and specifications of all system devices shall conform to applicable portions of the National Electric Code, latest edition, for installation in a general purpose area, with measurements and valves in a Class 1, Group B and D, Division 2 area.

SYSTEM DOCUMENTATION AND DRAWINGS

• Hardware Documentation

Vendor shall list the documentation that will be provided for the hardware as specified in this document. Vendor should show the number of copies to be provided with the system and the cost for each additional copy above the normal requirement.

• System Installation Documentation

Vendor shall provide an engineering manual to formally document the design review and specifications. It shall include, but not be limited to the following:

• Wiring diagrams and assembly for each controller.
• A system description of the compressor’s control scheme with anti–surge and integrated capacity control theory.
• Operating procedures for Purchaser’s specific system.
• Provisions for documenting all field configured parameters and a record of all preset values, curves, jumpers, etc.
• Field maintenance and trouble–shooting procedures.
• Instruction manuals for all system elements provide.
• P&ID’s outlining the control scheme with Owner’s instrument tag numbers.
• Rack layout drawing of the equipment.

ENGINEERING SERVICES

• Each Vendor shall provide complete engineering services in developing the optimum control strategy best suited for the Owner’s application and shall provide a control algorithm that is self– compensating for variable suction conditions, including variable gas composition. This information shall be provided with quote for review.
• Vendor shall define the surge control line for each compressor stage. The outputs of the anti– surge controllers will position recycle valves to protect the compressor from surge. Each anti– surge controller shall have standard backup control strategies in the event of input(s) failure.
• The Vendor shall have full responsibility for the operability and controllability of the anti–surge control system. The Vendor shall review the piping layout and location of equipment and instruments for compatibility with the control system.

TESTING AND INSPECTION

• General
• The Compressor Anti–Surge Controllers shall be given a complete shop and acceptance test prior to shipment.
• All electric components and circuit boards shall be tested and burned–in before installation into electronic assemblies.
• Shop Test

Manufacturer’s shall perform a complete system functional test before advising the Purchaser that the system is available for witnessed testing.

• Acceptance Test
• Tests to be witnessed by the Owner shall consist of a loop–by–loop functional test of each input, alarm, communications and control functions for proper operation. All programmed variables, tuning parameters and control algorithms shall be checked and verified. Manufacturer is to provide, for approval by Refining Company, a proposed written procedure and programming description for acceptance at least sixty days prior to factory test. Tests shall be performed using simulated inputs. Simulators shall be provided by the Manufacturer.
• Tests to be witnessed by the Owner shall consist of a loop–by–loop functional test of each input, alarm, communications and control functions for proper operation. All programmed variables, tuning parameters and control algorithms shall be checked and verified. Manufacturer is to provide, for approval by Company, a proposed written procedure and programming description for acceptance at least sixty days prior to factory test. Tests shall be performed using simulated inputs. Simulators shall be provided by the Manufacturer.
• All system hardware used for the acceptance test shall be the actual equipment to be shipped to the jobsite. The Manufacturer shall provide all necessary test equipment.
• The Owner shall assign engineers in conjunction with the client, to witness the shop test.
• Manufacturer is responsible to furnish qualified technician(s) to perform tests and debug the system during the scheduled acceptance test.

SHIPPING

• After written acceptance of shop test by the Purchaser’s personnel, Manufacturer shall disconnect all equipment and prepare system for shipment.
• All interconnecting cables shall be labeled at each end specifying instrument, terminal panel or plug–in connector to which cable is to be reconnected.

INSTALLATION

• Manufacturer shall assign qualified personnel to supervise the installation of the equipment.
• Manufacturer shall assign qualified personnel to check the system installation and supervise the initial system power–up activities.

• Manufacturer shall state the amount of time included in the proposal for the installation and shall include a rate sheet for both field and factory support by job positions.

FIELD TEST

• The extent of the field test shall be the same as outlined in paragraph 10.3, but shall be done with live inputs wherever possible.
• Field test shall be witnessed by the Owner.
• The Manufacturer shall provide technical assistance in conducting the field test.
• The Manufacturer shall be responsible for the maintenance of the system until successful completion of the field test.
• Manufacturer shall state the amount of time included in the proposal for the field test and shall include a rate sheet for field supports and factory support by job positions.

STARTUP

• Startup shall be conducted after the field acceptance test using live inputs. The Vendor’s engineer shall be responsible to monitor the control system for proper operation while the compressor is started up and operated by the Owner.
• The Vendor shall tune and calibrate the control system for proper operation.
• The Vendor shall conduct Owner approval simulated process changes and upsets to demonstrate that the control system meet all control objectives.
• The startup shall be witnessed by Refining Company .
• The startup shall be witnessed by Company.
• The Manufacturer shall provide technical support for the startup. Proposal shall include manhour rates for field and factory support by job positions.

TRAINING

• Recommended Training Courses

The Vendor shall include in the quotation charges for training of client engineers and operators on the programming, operation, and maintenance of the system. Quote shall include all costs of instruction and all training materials.

• Training Schedule

The Vendor shall supply a list of scheduled training.

• Course Outline

The Vendor shall provide an outline for each recommended training course.

MAINTENANCE/SPARE PARTS

• Vendor shall state his recommended spare parts requirements for startup and operation (one year) that Owner should maintain on hand. This recommendation, along with pricing, shall be submitted at time of bid by Vendor. The recommendation shall state the dollar value of a spare part inventory for the instrumentation system. Spare parts list shall include recommended spare parts, test equipment, and special maintenance tools.
• Vendor shall state the approximate turnaround time on defective parts.
• Vendor shall state the desirability of a maintenance contract for the system. Vendor shall state the approximate percentage of all similar systems of the Vendor that are under a maintenance contract, and shall supply a maintenance cost quotation.

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