B.3.4_Level Inst Spec

7/31/2019 B.3.4_Level Inst Spec

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STANDARD SPECIFICATION FOR

LEVEL INSTRUMENTS

DOCUMENT NO : 44-LK-5100-00/J.02/0007-A4

Rev No. Issue Date Pages Rev Description Prepared

By

Checked

By

Approved

By

A 12.08.08 8 Issued for Comments /Approval

NSA SPM BSP


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JACOBS ENGINEERING INDIA PRIVATE LTD

DOCUMENT NO :44-LK-5100-00/J.02/0007-A4 Date : 12.08.08STANDARD SPECIFICATION FOR LEVEL INSTRUMENTS Page 2 of 8

Revision No. : A

TABLE OF CONTENTS

1.0 PURPOSE

2.0 SCOPE

3.0 TECHNICAL REQUIREMENTS

3.1 LEVEL GAUGES3.2 LEVEL TRANSMITTER3.3 LEVEL SWITCH3.4 TANK LEVEL INSTRUMENTS3.5 MISCELLANEOUS3.6 FIELDBUS DEVICES GUIDLINE

4.0 RELATED DOCUMENTATION

5.0 ATTACHMENTS


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JACOBS ENGINEERING INDIA PRIVATE LIMITED

_________________________________________________________________________


Revision No. : A

1.0 PURPOSE

The purpose of this specification is to define the minimum requirements of design andmanufacture of Level Instruments.

2.0 SCOPE

The scope of work shall include design, manufacture, testing and supply of LevelInstruments. The inspection requirements shall be as per the inspection and test plan.

3.0 TECHNICAL REQUIREMENTS

3.1 LEVEL GAUGE

3.1.1 Float operated magnetically coupled gauges with 2" (50 mm) flanged end connections,shall be used, for level gauging in very viscous liquids, liquids with crystals, sourservices, toxic services and shall be of Bi-Colour rolling Cylinders/Balls. In generalmagnetically coupled level gauges shall be preferred over gauge glasses.

3.1.2 Bi-colour type level gauges shall be used on steam drums. Large chamber gaugeglasses and an expansion loop between the top of the gauge and the top gauge valveshall be used. Level gauges on steam / boiler drums shall be in accordance with thelatest requirements of the IBR code.

3.1.3 The Level gauge shall provide visible coverage of complete level transmitter / controllerrange and the alarm / trip level switches. In the case of differential pressure leveltransmitters where large spans are involved, a gauge located at the top, centre, andbottom of the installation with overlap in visible area shall be acceptable.

3.1.4 Magnetic coupled level gauges shall be preferred over gauge glasses. Where magneticlevel gauges are not suitable for services such as high temperature etc steel armouredreflex or transparent type shall be considered. Wherever gauge glasses are considered,they shall be with body & cover material of forged steel and shall have mechanical &thermal shock resistant type toughened borosilicate glass with suitable gasket. Boltingshall be of SAE 4140 steel. Transparent type of gauges shall be provided with integralilluminators operating at 240 V 50 Hz supply and suitable for electrical area classificationspecified. Illuminator shall be of the plastic solid wedge type designed to give an evendiffusion of light over the entire length of the gauge glass. All gauge glasses must havea rating equal to or more than the vessel design pressure and temperature and shall beprovided with suitable metal guard.

3.1.5 Reflex type shall be used for clean and colourless liquids like water and hydrocarbon

service, except liquids interface level. For low temperature, low boiling point service,foaming liquids, large chamber type will be used. Transparent type will be used for lightfluids, acids, caustic, dirty or viscous liquids, coloured liquids and liquids interface level.Transparent type with Mica or Kel-F shields shall be used for treated water, boiler andcondensate services and for corrosive liquids which will attack glass. Tubular gaugeglasses shall, in general, not be used. They may be used for non-hazardous services atambient temperature and low pressures.

3.1.6 All gauges shall have top and bottom chamber connections, unless otherwise specified.Vent and Drain valves shall be fitted, as applicable. Vent and drain valve shall beprovided with nipple and end caps. Drain and vent shall be of welded construction.Level


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Revision No. : A

gauges with side-side connections shall be avoided. Each gauge shall be provided withball check valves & pipe union.

3.1.7 Large chamber gauges with frost shields shall be provided for cold services below 0C.Frost shield shall be transparent plastic type covering full width of vision slot and suitablysealed to the glass.

Depth of Block Design Temperature38 mm above 19 C75 mm -20C to 49C150 mm -50C to 99C200 mm below -100C

Heating jacket shall be provided for viscous liquids.

3.1.8 The minimum readable liquid level from bottom tangent line for level gauge with top &

bottom connections and when both the nozzles are from the side shall be 300mm with /without standpipe.

3.1.9 In general, the visible length of the level gauges shall be selected from the following:

Visible length (mm) Centre to Centre Length (mm)220 470470 720720 970980 1230

The maximum visibility length shall not exceed 1500 mm for a single gauge. Multiplegauges with overlapping range shall be used for such cases. For a given section, thevisible length shall not be less than 90% of the total length of section.

3.1.10 Gauge glass cocks shall be forged offset type with integral ball check and back seatingstem. Primary isolation valves are normally required in addition to the gauge glasscocks, except on vented tanks containing harmless liquids. Where the process fluidtends to foul the cocks internals and create plugging or where leakage is a problem,gauge valve may be eliminated. On low temperature service with liquids having veryhigh vapour pressure at ambient temperature safety valve shall be provided at the ventconnection of the gauge glass. Gauge cocks may be deleted or ball checks omittedwhen the fluid is not toxic / corrosive / inflammable / at high pressure and when there is apossibility of sluggish action. If ball checks are used, it shall be checked that the processpressure is high enough to drive the ball in case of breakage.

3.2 LEVEL TRANSMITTER

3.2.1 External displacer type instruments with side-side connections and rotatable head shallnormally be used for level measurement upto 1219 mm. Side-bottom connections arepreferred where RTJ flanges are required. Internal displacer type of level transmittersshall be avoided unless application necessitates its use. Stilling well shall be providedfor internal displacer.

3.2.2 Conventional Electronic transmitters shall be two wire, 24 VDC, 4-20 mA output with'HART' Protocol. Specifications for DP type level transmitters shall be as elaborated inStandard Specification for Pressure/DP Instruments.

3.2.3 A separate Hand held communicator with necessary software for communication loadedshall be provided along with displacer level transmitters.


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Revision No. : A

3.2.4 All displacer type level transmitters shall be of torque tube type with torque tube materialof inconel, as a minimum. Accuracy of displacer type level transmitters shall be +/- 0.5%.

The standard materials shall be as a minimum: -

Displacer : 316 SSTorque tube : InconelChamber : Carbon Steel

Finned torque tube extensions shall be provided as necessary for high or lowtemperature service conditions.

3.2.5 In general, displacer type instruments shall be used with displacer lengths of 356 mm,

813 mm and 1219 mm. For interface level measurement, displacer type instrumentsshall only be used.

3.2.6 Differential pressure transmitter shall be used for level measurement above 1219 mm forservices requiring purge or where liquid might boil in external portion.

3.2.7 Differential pressure transmitters for use on corrosive or fouling service shall generallybe diaphragm wafer with filled capillary type. Flush or extended diaphragm typedifferential pressure transmitter shall be considered for special applications only.Diaphragm material shall normally be stainless steel or any other special alloy.Transmitters for closed vessels shall have correction for suppression or elevation.

3.2.8 Dip Tube type level transmitters may be used on corrosive, congealing, slurry serviceswhere suitable diaphragm seal type transmitter is difficult to obtain or where accuracy is

not of prime importance.

3.2.9 For Hot service applications Radr type level transmitters shall be consideredwhen suitable.

3.3 LEVEL SWITCH

3.3.1 In general level switches shall be avoided. However, when specified, level switches shallgenerally be external ball float type with flanged head. External displacer type levelswitches can be considered for lighter fluids where specific gravity is less than 0.5.Internal float / displacer type level switches shall only be used if external ball float /displacer type is not possible, like in viscous services and in underground tanks /vessels.

3.3.2 The low-level switch shall be mounted directly on the column when the set point is notless than 630mm. When level gauge and level switch are on the same standpipe, theminimum allowable low level set point shall be 480mm on the column.

3.3.3 Switch shall be sealed micro type with contact rating suitable for the specific application.Level switches with reed switch shall not be used.

3.3.4 Level switch shall be furnished with SPDT contacts with adjustable differential, unlessotherwise specified.


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Revision No. : A

3.3.5 Tuning fork, capacitance, displacer or paddle type level switch may be used whereverapplication calls for such device.

3.4 TANK LEVEL INSTRUMENTS

3.4.1 Mechanical float type gauge shall be used for atmosphere tanks and vessels where levelmeasurement accuracy requirement is of the order of 2 mm. Liquid seal chamber shallbe used where tank contents are toxic or tank is blanketed. The float shall be of 316stainless steel as a minimum. Cages shall be carbon steel as standard unless serviceconditions demand a higher specification.

3.4.2 Servo controlled gauges shall be used for level measurement of pressurised tanks /vessels / spheres requiring remote signal transmission and better level measurement

accuracies. Level / data transmission signal shall be digital only. Servo type instrumentsshall have 6" process connection with 12" dia still well. The accessories for servo-controlled level gauge shall include calibration chamber, operator keys for moving thedisplacer and isolation ball valves for pressurised tanks.

3.4.3 The tank side indicator for both types of gauges shall have hoisting facility. All tank levelgauges shall have side mounted indicator - counter type for mechanical float type andsolid state digital for servo controlled level gauge.

3.4.4 RADAR type tank gauges shall be used for storage tanks handling viscous fluids,pressurised tanks or as specified in job specification.

3.4.5 Hydrostatic tank gauging system can be used for high accuracy measurement if theapplication calls for same.

3.4.6 The wetted material like float, displacer, tape, wire etc. shall be minimum 316 SS.

3.5 MISCELLANEOUS

3.5.1 Other special type of level instruments like RADAR, ultrasonic, hydrostatic, nucleonic,capacitance, conductivity and magnetostrictive type shall be used as necessitated byapplication requirements.

3.5.2 For high-pressure steam drum application, conductivity type (Hydrostatic or equivalent)level instrument shall be preferred.

3.5.3 For solid level measurement, type of instrument shall be ultrasonic / RADAR / paddle /electromechanical / capacitance / nucleonic. The actual type selection shall be carried

out based on the provenness of the selected type for the similar type of application.

3.5.4 Standpipe shall be used for clean, non-viscous and non-crystallising services if morethan 4 nozzles are required for level instruments, e.g. one displacer instrument and onelevel gauge can be mounted directly on the equipment.

The maximum number of nozzles on the standpipe shall be limited to: -8 nos. with no displacer type level instrument on it6 nos. with displacer type level instrument on it.

The size of standpipe shall be 2 NB minimum and valved at the instrumentconnections.


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Revision No. : A

Trip level switches should be directly mounted on vessel / column and not onstandpipe. Connection of standpipe from the bottom of vessel should be avoided.

On horizontal vessels with boot, separate standpipe shall be used for boot interfacelevel measurement in addition to standpipe used for horizontal vessel.

3.5.5 Level co-ordination sketches shall be produced showing all pertinent details includingnozzle locations, alarm levels, shutdown levels, normal liquid levels and dimensionaldetails.

3.5.6 All displacer and float type instruments shall have provisions for on-site calibrationsimulation check.

3.5.7 Differential pressure type transmitters used for level measurement shall be calibratedusing wet leg. A provision shall be made for liquid filling during installation.

3.6 FIELD BUS DEVICES GUIDELINES

3.6.1 The Field bus transmitter shall be 2 wire system and shall have minimum facility as- Foundation fieldbus output compliant to ITK 4.6 or above.- Shall employ device description to facilitate interoperability.

3.6..2 It shall not be sensitive to the polarity of the wiring connection.

3.6.3 It shall operate on 9 to 32 V dc, with current draw capacity of 17mA maximum. This lowpower consumption shall allow more devices to be connected to a segment.

3.6.4 The digital integral LCD display shall be capable of displaying any other variable from anydevice on same segment.

3.6.5 Vendor to specify Response time (including dead time, time constant and min damping)

3.6.6 The foundation fieldbus transmitter must have the following essential facilities to facilitatecomplete FF functionality including control in the field as and when required.

- Shall have multiple FF compliant analog input (AI) blocks (2 Nos with execution rateof 30 ms or below) and VCRs (at least 12 Nos or above) to allow control in the fieldMultiple AI blocks shall provide flexibility in using transmitter data for calculations andalarming, while VCRs used for communication between function block both within adevice as well as amongst different devices shall be sufficient to execute all interblock data transfers.

- Shall have a characterizer block for strapping tables.- Shall have a integrator block for totalisation.

-

Shall have a arithmetic block for functions such as level or density calculation.- Shall have a input selector block for voting or averaging applications.- Shall have a PID function block with PID.- Shall provide a back up link active scheduler ( LAS) so as to improve the reliability

and security of the FF network.- Shall have software download capability for upgrades or product enhancement via

fieldbus segment with the segment in operation.- Shall have guided routine (methods) for calibration and restoration of sensor

defaults.- Shall have block execution times less than 45ms.


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Revision No. : A

3.6.7 Diagnostics

The transmitter shall perform continuous self diagnostics, be capable of self test functionsand be able to provide specific diagnostic information locally on the LCD meter andremotely via digital FF communications protocol. The diagnostic capabilities shall includethe following features-- Shall detect and alert or alarm during process abnormal situations using statistical

methods.- Shall provide a variety of standard statistical monitoring configuration defaults for

detection such as plugged impulse line detection and flame instability.- Shall have an easy system for alerts and understanding of faults, failures and

anomalies either in the sensor, electronic circuits or process.

4.0 RELATED DOCUMENTATION

Nil

5.0 ATTACHMENTS

Nil

B.3.4_Level Inst Spec

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Transcript of B.3.4_Level Inst Spec