1 Scope

NOTE This specification covers field-mounted level measurement instruments — continuous-level transmitters and point-level switches — that sense the surface elevation or interface position of a liquid (or, for some technologies, a solid) in a vessel and convert it to a standardized signal for monitoring, control, alarm, and safety shutdown. (1.1)

NOTE The measured variable is stored volume or surface elevation within a tank, wet well, clarifier, sump, day tank, or bulk storage vessel. Level inferred from a primary flow element over a weir or flume is a flow measurement, owned by Flow Measurement, and is excluded here. (1.2)

NOTE Equipment covered includes the sensing element (antenna, probe, float, displacer, diaphragm, or transducer), the transmitter electronics, point-level switch electronics, local indicators, mounting hardware, process connections, and the wetted materials that contact the measured medium. (1.3)

NOTE Both continuous transmitters (4-20 mA with HART, and digital fieldbus) and discrete point-level switches are addressed, as is liquid-liquid interface detection. (1.4)

NOTE This standard goes deeper than Process Instrumentation on the level-specific technology decision tree — dielectric constant, blocking distance, antenna and probe style, foam and vapor mitigation, and SIL application. The shared transmitter platform (power, HART, hazardous-area concepts, tagging, loop identification) lives in Process Instrumentation; the two standards are intended to be read together. (1.5)

NOTE Where a project applies both this standard and Process Instrumentation to the same instrument, the more specific level requirement in this standard governs the technology, probe, and installation; the platform requirement governs the shared electrical and identification provisions. (1.6)

2 Referenced Standards

2.1Equipment, materials, and installation shall comply with the latest adopted edition of each of the following unless a specific edition is cited.

2.2Where referenced standards conflict, the more stringent requirement shall govern unless the Engineer of Record directs otherwise in writing.

Standard	Title
ANSI/ISA-5.1	Instrumentation and Control — Symbols and Identification
ISA-5.4	Instrument Loop Diagrams
ISA-TR20.00.01	Specification Forms for Process Measurement and Control Instruments, Primary Elements, and Control Valves
IEC 61511-1	Functional Safety — Safety Instrumented Systems for the Process Industry Sector — Part 1
IEC 61508-1	Functional Safety of Electrical/Electronic/Programmable Electronic Safety-Related Systems — Part 1
API RP 551	Process Measurement Instrumentation — Field Instrumentation
API 2350	Overfill Protection for Storage Tanks in Petroleum Facilities
ASME B16.5	Pipe Flanges and Flanged Fittings: NPS 1/2 Through NPS 24
ASME B1.20.1	Pipe Threads, General Purpose (Inch)
IEC 60529	Degrees of Protection Provided by Enclosures (IP Code)
NEMA 250	Enclosures for Electrical Equipment (1000 Volts Maximum)
NFPA 70	National Electrical Code (Articles 500, 501, 504, 505)
ANSI/UL 60079-0	Explosive Atmospheres — Equipment — General Requirements
UL 913	Intrinsically Safe Apparatus for Use in Class I, II, and III, Division 1 Hazardous (Classified) Locations
ANSI/UL 60079-11	Explosive Atmospheres — Equipment Protection by Intrinsic Safety "i"
NSF/ANSI/CAN 61	Drinking Water System Components — Health Effects
NSF/ANSI 372	Drinking Water System Components — Lead Content
ANSI/ISA-50.00.01	Compatibility of Analog Signals for Electronic Industrial Process Instruments

NOTE API 2350 is listed as a governing reference even on non-petroleum projects because its independence requirements are the accepted industry model for any bulk-storage overfill-prevention design. (2.3)

3 Submittals

3.1 Action Submittals

3.1.1The Contractor shall submit the following action submittals for review before fabrication or procurement:

Product data sheets for each level instrument type, completed on the ISA-TR20.00.01 specification form, identifying technology, measurement range, accuracy, wetted materials, process connection, output, and area classification.
A level instrument schedule cross-referencing each tag to its vessel, service, range, technology, and P&ID.
Manufacturer installation drawings showing nozzle size and orientation, stand-pipe or stilling-well dimensions, probe length, and required clearances to vessel walls and internals.
Loop diagrams per ISA-5.4 for each transmitter, showing power, signal, intrinsic-safety barriers, and I/O termination.
Dielectric constant verification for each radar and guided-wave-radar application, confirming the process fluid meets the instrument minimum.
Hazardous-area certification documentation (intrinsic safety, explosion-proof, or non-incendive) for each instrument in a classified location.
NSF/ANSI/CAN 61 and NSF/ANSI 372 certification for instruments in potable-water service.
Functional safety (SIL) certificate and PFD data for each instrument used in a safety instrumented function.

Action submittals requiredcheckbox

☑ ISA-TR20.00.01 product data sheet (per instrument)

☑ Level instrument schedule (tag / vessel / service / range)

☐ Manufacturer installation drawings (nozzle, probe, clearances)

☑ Loop diagrams per ISA-5.4

☐ Dielectric constant verification (radar / GWR)

☐ Hazardous-area certification

☐ NSF/ANSI/CAN 61 and 372 certification (potable service)

☐ SIL certificate and PFD data (safety functions)

3.2 Informational Submittals

3.2.1The Contractor shall submit the following informational submittals:

Factory acceptance test (FAT) records showing zero and span verification for each transmitter.
Certificate of conformance for each SIL-rated device.
Material certifications for wetted parts in aggressive chemical or potable service.
Manufacturer calibration certificates traceable to national standards.

Informational submittals requiredcheckbox

☑ Factory acceptance test (FAT) records

☐ Certificate of conformance (SIL devices)

☐ Wetted-material certifications

☑ Manufacturer calibration certificates

3.3 Closeout Submittals

3.3.1The Contractor shall submit the following closeout submittals before substantial completion:

Field loop check records for each loop, verified end-to-end from transmitter to DCS/PLC I/O card.
As-configured parameter reports captured by HART communicator (tag, range, damping, blocking distance, alarm setpoints).
Calibration certificates for all field-calibrated instruments.
Operation and maintenance manuals, including the SIL proof-test procedure and interval where applicable.

Closeout submittals requiredcheckbox

☑ Field loop check records (end-to-end)

☑ As-configured HART parameter reports

☑ Field calibration certificates

☑ O&M manuals (incl. SIL proof-test procedure)

4 Quality Assurance

4.1Each level instrument shall be the product of a manufacturer regularly engaged in the production of process level instrumentation, with documented application support for the selected technology.

4.2Each transmitter shall be factory zero- and span-verified before shipment, with a calibration record traceable to national measurement standards.

4.3Instruments used in a safety instrumented function shall carry a SIL certification from an accredited body, and the certificate shall state the achieved SIL capability and probability of failure on demand (PFD).

4.3.1The PFD and proof-test interval stated in the SIL certificate shall be consistent with the safety requirement specification for the function; an instrument whose certified PFD does not satisfy the target shall not be accepted.

4.4Tagging and identification shall follow ANSI/ISA-5.1 conventions (LT for level transmitter, LI for indicator, LS for switch, LIT for indicating transmitter, LAH/LAL for high/low alarms, LSHH for high-high switch).

4.4.1Each instrument shall bear a permanent stainless-steel nameplate showing tag number, service, range, and supply requirements.

4.5Wetted materials in potable-water service shall be certified to NSF/ANSI/CAN 61 and NSF/ANSI 372 (lead content).

5 Technology Selection

NOTE Selecting the measurement technology is the single most consequential level-instrument decision; it is driven by the process fluid (dielectric constant, conductivity, corrosivity), vessel geometry, the presence of foam, vapor, condensation, or agitation, and the required accuracy. The wrong technology generates RFIs at startup and, in the worst case, an unmeasurable loop. (5.1)

NOTE Non-contact free-space radar (FMCW or pulse) is the default continuous technology for most clean and moderately dirty liquids in tanks and vessels, because it does not contact the fluid, tolerates wide temperature and pressure ranges, and is unaffected by changing density. It requires a fluid dielectric constant at or above the instrument minimum and a clear signal path free of obstructions. (5.2)

NOTE Guided-wave radar (GWR/TDR) guides the microwave pulse along a probe, which concentrates the signal and allows measurement of lower-dielectric fluids, foamy surfaces, turbulent surfaces, and liquid-liquid interfaces that defeat free-space radar. It is the preferred choice where free-space radar signal return is marginal. (5.3)

NOTE Ultrasonic non-contact level is a lower-cost option for clean-water utility service (sumps, basins, wet wells) where moderate accuracy is acceptable; it is degraded by foam, steam, vapor, and extreme temperature, and is not suitable where high accuracy or harsh vapor conditions exist. (5.4)

NOTE Hydrostatic level (submersible or side-mounted) infers level from head pressure and is well suited to open wet wells and lift stations; it is sensitive to fluid density variation and, in sealed gas-blanketed tanks, requires vented-reference or differential-pressure compensation. (5.5)

NOTE Differential-pressure (DP) level measures the head between two taps and is the established choice for pressurized and closed vessels, including those with a vapor blanket; it requires careful impulse-line or remote-seal design and density compensation. (5.6)

NOTE Magnetostrictive, displacer, float-and-cable, and capacitance technologies serve specific niches — high-accuracy interface, external-cage displacement, simple float switching, and conductive/coating-tolerant insertion sensing respectively — and are selected where the dominant technologies are unsuitable. (5.7)

Primary measurement technologyradio

● Non-contact free-space radar (FMCW)

○ Non-contact free-space radar (pulse)

○ Guided-wave radar (GWR/TDR)

○ Ultrasonic (non-contact)

○ Hydrostatic (submersible)

○ Differential-pressure (DP)

○ Magnetostrictive float

○ Displacer

○ Float-and-cable

○ Capacitance (RF admittance)

Instrument functionradio

● Continuous transmitter (4-20 mA control/trend)

○ Point-level switch (discrete alarm/shutdown)

○ Both (independent transmitter + safety switch)

Measured quantityradio

● Single-phase level (surface elevation)

○ Liquid-liquid interface (e.g. oil-water)

5.9 Dielectric Constant and Signal Return

NOTE The Engineer shall confirm the process fluid dielectric constant against the instrument minimum before specifying radar or guided-wave radar; a fluid below the minimum yields weak or lost signal. (5.9.1)

NOTE Standard rod-antenna free-space radar and standard GWR rod probes require a fluid dielectric constant (εr) at or above 1.6 to 1.8; specialized low-dielectric models reach εr ≥ 1.4. (5.9.2)

NOTE Water has a dielectric constant of approximately 80, hydrocarbons 1.8 to 2.5, and slurries 5 to 20; light hydrocarbons and some solvents fall near or below the standard threshold and require a low-dielectric model, a guided-wave probe, or an alternative technology. (5.9.3)

5.9.4The transmitter datasheet shall state the minimum acceptable dielectric constant, and the selected model shall satisfy it for the worst-case (lowest-εr) process condition.

Minimum process fluid dielectric constant (εr)range

εr (relative)

1.480

Default: 1.8 εr (relative)

5.10 Blocking Distance and Dead Zones

NOTE The blocking distance (blanking zone) is the region immediately below a radar or ultrasonic antenna where measurement is invalid; if the empty (lowest) level falls within this zone, the instrument reports a false reading and loses the bottom of the range. (5.10.1)

5.10.2The instrument range shall be configured so that the lowest measured level remains outside the manufacturer's blocking distance, with margin; the blocking distance shall be recorded in the as-configured parameter report.

NOTE Free-space radar blocking distance is typically 0.3 to 0.5 m below the antenna; guided-wave radar is 0.1 to 0.3 m at the probe top; ultrasonic blanking is 0.25 to 0.5 m. (5.10.3)

NOTE Where the vessel geometry would otherwise place the empty level inside the blocking distance, the instrument shall be raised, a stand-pipe used, or a technology without a top dead zone (hydrostatic or DP) selected. (5.10.4)

6 Continuous Transmitters

NOTE Continuous level transmitters convert the sensed level across the measurement span to a 4-20 mA analog signal, optionally with superimposed HART, or to a digital fieldbus value. The span runs from the lower range value (LRV, minimum detectable level) to the upper range value (URV, full span), and is sized from the vessel operating window with allowance for blocking distance and bottom dead-band. (6.1)

NOTE The accuracy required of a transmitter shall be matched to the application: high accuracy for inventory and metering service, modest accuracy for utility sumps and basins. Over-specifying accuracy for utility service drives unnecessary cost; under-specifying for chemical dosing or inventory drives startup RFIs. (6.2)

6.2.1The transmitter range shall be selected so the normal operating level falls within the middle 60 to 80% of span, providing headroom for high and low excursions.

6.2.2The 4-20 mA output shall comply with ANSI/ISA-50.00.01.

6.2.3Where HART is used, it shall be HART revision 7 unless host-system compatibility requires HART 5.

6.2.4Multidrop HART (digital only, current fixed at 4 mA) shall not be used for continuous level control; it is restricted to diagnostic and asset-management use because it disables the analog control signal.

Output signal protocolradio

● 4-20 mA with HART 7 (point-to-point)

○ 4-20 mA with HART 5 (point-to-point)

○ 4-20 mA only (no HART)

○ FOUNDATION Fieldbus H1

○ Profibus PA

Transmitter wiringradio

● 2-wire loop-powered (24 VDC, 4-20 mA)

○ 4-wire separately powered

Supply voltage (2-wire loop)range

VDC

1642

Default: 24 VDC

Continuous transmitter accuracyselect

±1 mm (high-accuracy radar/GWR)

±3 mm or ±0.1% of span (radar default)

±0.1% FS (hydrostatic WTP/WWTP default)

±0.075% of span (DP default)

±0.25% of span (ultrasonic clean-water)

6.3 Measurement Range

NOTE The measurement range shall be set from the vessel geometry and process operating window, not from the instrument's maximum capability; an oversized range degrades resolution. (6.3.1)

NOTE Free-space radar covers 0.3 m to 70 m depending on model; guided-wave radar reaches 45 m with a cable probe or 6 m with a rigid rod probe; ultrasonic spans 0.3 m to 15 m; submersible hydrostatic ranges from 0 to 0.5 m WC up to 0 to 200 m WC. (6.3.2)

6.3.3For submersible hydrostatic sensors, the pressure range shall be selected at 1.5 to 2 times the maximum expected depth, and the cable length shall suit the suspension depth.

Measurement span (LRV to URV)range

m

0.370

Default: 6 m

6.4 Radar Antenna and Probe Selection

NOTE The radar antenna or probe style shall be selected for the dielectric, vessel geometry, and mounting nozzle, and coordinated with the vendor before vessel fabrication. (6.4.1)

NOTE Free-space radar horn antennas suit large vessels and liquids and require a minimum nozzle inside diameter (often 4 inches) and a defined stand-pipe length; rod antennas suit smaller vessels; parabolic and cone antennas serve low-dielectric or long-range duty. (6.4.2)

NOTE Guided-wave radar single-rod probes suit liquids with εr above 1.6; twin-rod probes suit solids; coaxial probes suit low-dielectric fluids and foam; cable probes suit tall vessels over 6 m. (6.4.3)

NOTE Nozzle orientation, size, and stand-pipe length, and the probe clearance to vessel walls and internals, shall be coordinated with the instrument vendor before the vessel is fabricated; flanged GWR probes require centerline clearance of at least one nozzle diameter from the vessel wall. (6.4.4)

Free-space radar antenna styleselect

Horn antenna (large vessel, liquids)

Rod antenna (small vessel)

Parabolic dish (low dielectric / long range)

Cone antenna

Guided-wave radar probe styleselect

Single-rod (liquids, εr > 1.6)

Twin-rod (solids)

Coaxial (low dielectric / foam)

Cable (tall vessels > 6 m)

7 Point-Level Switches

NOTE Point-level switches provide a discrete on/off output when the level reaches a fixed point, and are used for high and low alarms, pump start/stop, and safety shutdown. Vibrating-fork (tuning-fork) switches are the robust default for liquids because they are unaffected by coating, density, and conductivity; float and capacitance switches serve simpler or coating-sensitive duties. (7.1)

7.1.1Vibrating-fork switches shall be the default point-level technology for liquid alarm and shutdown duty unless the service requires float, displacer, or capacitance sensing.

7.1.2The switch output type (relay, transistor, or NAMUR) shall be coordinated with the receiving I/O; safety-shutdown switches shall provide a fail-safe output that de-energizes on fault.

7.1.3A point-level switch used for safety shutdown shall be independent of the control transmitter and shall be mounted on a separate nozzle.

Point-level switch technologyradio

● Vibrating-fork (tuning-fork)

○ Float-type (SPDT)

○ Capacitance (RF admittance)

○ Displacer-type

Switch output typeselect

Relay (SPDT, dry contact)

Transistor (PNP/NPN)

NAMUR (intrinsically safe)

Direct load switching (DPDT)

8 Safety Instrumented Functions

NOTE Where a level instrument is part of a safety instrumented function — high-high shutdown or overfill prevention — it shall be specified, installed, and tested per IEC 61511, with the underlying device certified per IEC 61508. The function's required SIL drives device selection, independence, and proof-test interval. (8.1)

NOTE API 2350 establishes the accepted independence model for bulk-storage overfill prevention: the overfill detection element must be independent of the basic process control system's level instrument. This model shall be applied to any bulk-storage overfill design, petroleum or not. (8.2)

8.2.1A single transmitter shall not serve as both the basic process control instrument and the safety shutdown device; functional independence per IEC 61511 requires a separate SIL-rated switch or a second transmitter on its own nozzle.

8.2.2SIL 1 shall be the minimum rating for a single high-level alarm function; SIL 2 shall be required for high-high shutdown and overfill protection per the safety requirement specification.

8.2.3The SIL proof-test interval shall be stated in the O&M requirements; SIL 2 level switches typically require proof testing every one to three years, and the interval shall be consistent with the certified PFD.

8.2.4Loop calibration tolerance for SIL applications shall be ±0.25% of span, tighter than the ±0.5% applied to general process measurement.

Functional safety ratingradio

● Non-SIL (monitoring/control only)

○ SIL 1 (single high-level alarm)

○ SIL 2 (high-high shutdown / overfill)

Independent overfill protection (API 2350 model)radio

○ Required (separate SIL device, own nozzle)

● Not required (no bulk-storage overfill risk)

9 Wetted Materials and Process Connections

NOTE The wetted material shall be selected against the process fluid chemistry, temperature, and concentration. 316L stainless steel is the default, but chlorinated water above roughly 50 ppm and aggressive chemical service require an upgraded alloy or lining. (9.1)

9.1.1The wetted material and process connection schedule shall be stated explicitly on the instrument datasheet; a 316 SS flange may be inadequate for aggressive service and a nickel-alloy or PTFE-lined version must be called out where required.

9.1.2nickel-molybdenum-chromium alloy (UNS N10276), PTFE-lined, or ceramic wetted parts shall be specified where the process fluid chemistry exceeds the corrosion limits of 316L stainless steel.

9.1.3The process connection type and size shall be coordinated with the vessel nozzle and rating: threaded NPT for smaller vessels and utility service, flanged for larger vessels, and hygienic tri-clamp for food and pharmaceutical service.

9.1.4Threaded connections shall conform to ASME B1.20.1; flanged connections shall conform to ASME B16.5 and shall match the vessel flange rating and facing.

Wetted materialradio

● 316L stainless steel

○ nickel-molybdenum-chromium alloy (UNS N10276)

○ PTFE-lined

○ Ceramic

Process connection typeradio

○ Threaded NPT (ASME B1.20.1)

● Flanged (ASME B16.5)

○ Hygienic tri-clamp

○ Direct vessel-nozzle mount

Flanged connection ratingselect

ANSI Class 150

ANSI Class 300

Process connection sizeselect

3/4 in NPT

1 in NPT

1-1/2 in flanged

2 in flanged

3 in flanged

4 in flanged

6 in flanged

10 Environmental and Service Conditions

NOTE The instrument housing and electronics shall be rated for the installed environment — wet, corrosive, submerged, or hazardous — and for the process temperature and pressure at the connection. (10.1)

10.1.1The transmitter enclosure shall be rated NEMA 4X / IP66 for standard outdoor wet locations.

10.1.2Submersible hydrostatic sensors shall be IP68 rated for the actual submersion depth.

10.1.3Splash-only applications may use IP67 where submersion is not possible.

10.1.4The standard ambient temperature range shall be −40 to +70°C; extended-range electronics shall be specified where the outdoor climate is more severe, to −50 to +85°C.

10.1.5The process temperature and pressure rating shall cover the worst-case service; standard transmitters are not rated for steam-jacketed or cryogenic vessel temperatures, which require a high-temperature version or a remote seal.

10.1.6Foam, condensation, and vapor service conditions shall be stated on the datasheet; foam with εr below 2 absorbs radar, and condensate on a radar antenna scatters the signal, so a high-gain antenna, a purge connection, or a guided-wave alternative shall be specified for these conditions.

10.1.7Submersible hydrostatic sensors in sealed or gas-blanketed tanks shall include a vented reference tube or differential-pressure compensation; without it, blanket-pressure variation produces a systematic level offset.

Enclosure ratingradio

● NEMA 4X / IP66 (outdoor wet)

○ IP67 (splash-proof)

○ IP68 (submersible — specify depth)

Process temperature ratingselect

Standard (−20 to +85°C ambient, fluid to 150°C)

High-temperature (to +450°C, remote seal)

Cryogenic (to −196°C)

Ambient temperature rangerange

°C

-5085

-50-407085

Default: -40 °C

Special service conditions presentcheckbox

☐ Foam on liquid surface

☐ Heavy vapor or steam

☐ Condensation on antenna

☐ Surface agitation/turbulence

☐ Sealed/gas-blanketed vessel

11 Hazardous Area Classification

NOTE Instruments installed in classified locations shall be certified for the area and protected by the appropriate concept — intrinsic safety, explosion-proof (flameproof), or non-incendive — per NFPA 70 Articles 500, 501, 504, and 505, and the relevant UL 60079 series. (11.1)

11.1.1The area classification (general purpose, Division 1, Division 2, or ATEX/IECEx Zone 0/1/2) shall be stated for each instrument location and shall determine the housing, protection concept, and barrier requirements.

11.1.2Intrinsically safe instruments in Division 1 / Zone 0/1 locations shall be certified per UL 913 and ANSI/UL 60079-11, and shall be installed with a certified intrinsic-safety barrier; the entity parameters of instrument and barrier shall be verified compatible.

11.1.3Explosion-proof (conduit-and-seal) installations in Division 1 shall include a conduit seal fitting within 18 inches of the instrument per NEC Article 501.15; the seal location shall be shown on the installation drawing.

11.1.4Equipment for explosive atmospheres shall comply with ANSI/UL 60079-0 general requirements in addition to the selected protection concept.

Hazardous area classificationradio

● General purpose (non-classified)

○ Class I Division 1 — intrinsically safe

○ Class I Division 1 — explosion-proof

○ Class I Division 2 — non-incendive

○ ATEX/IECEx Zone 0/1/2

12 Local Indication

NOTE Most field locations require a local display so an operator at the vessel can read the level without a control-room reference. The display shall be an integral LCD unless the location is remote-only by design. (12.1)

12.1.1Each field transmitter shall provide an integral LCD showing the measured level in engineering units unless the datasheet specifies remote indication only.

12.1.2The local display shall be loop-powered on 2-wire transmitters and shall not require a separate supply.

Local indicationradio

● Integral LCD display

○ No local display (remote only)

13 Testing

NOTE Each instrument shall be verified at the factory and again in the field, and each loop shall be proven end-to-end before the system is accepted. Calibration and verification methods, and intervals, shall be defined for both process and safety service. (13.1)

13.1.1Each transmitter shall pass a factory acceptance test confirming zero and span; SIL-rated devices shall ship with a certificate of conformance.

NOTE Each level loop shall receive a field loop check verifying the signal end-to-end from transmitter to the DCS/PLC I/O card, using a HART communicator to confirm tag, range, and damping. (13.1.2)

13.1.3The commissioning calibration tolerance shall be ±0.5% of span for general process measurement and ±0.25% of span for SIL applications.

NOTE The calibration method — wet calibration with actual fluid, dry calibration from calculated empty-vessel geometry, or simulation via HART communicator — shall be recorded for each instrument. (13.1.4)

NOTE The calibration interval shall be 12 months for continuous transmitters in process service and 6 months for SIL-rated safety functions, per the process safety management plan. (13.1.5)

13.1.6Flanged process connections shall be hydrostatically tested at 1.5 times the maximum allowable working pressure and factory leak-tested before shipment.

Calibration method at commissioningradio

○ Wet calibration (actual fluid)

● Dry calibration (calculated empty vessel)

○ Simulation via HART communicator

Calibration intervalselect

12 months (process service)

6 months (SIL safety function)

14 Installation

NOTE Installation shall follow the manufacturer's mounting requirements and API RP 551 field practice, with attention to nozzle coordination, probe clearance, conduit sealing, and signal wiring routed per the electrical standards. (14.1)

14.1.1Radar and guided-wave instruments shall be mounted with the nozzle, stand-pipe, and probe clearances coordinated to the approved installation drawing; the antenna shall have a clear, obstruction-free signal path to the surface.

14.1.2Guided-wave radar probes shall maintain the manufacturer's minimum clearance to vessel walls and internals and shall be anchored where cable-probe sway could contact the vessel.

14.1.3Submersible hydrostatic sensors shall be suspended by their integral cable with strain relief at the top, and the vent tube (where present) shall be protected from moisture ingress with a desiccant or vent filter.

14.1.4Conduit seals required by the area classification shall be installed within the code-required distance of the instrument and shall be poured before energization.

14.1.5Signal wiring shall be installed in raceway per Raceways And Conduit, with conductors per Conductors And Cables, and instrument grounding and shield termination per Grounding And Bonding; intrinsically safe wiring shall be segregated from non-IS wiring.

14.1.6Power supplies and intrinsic-safety barriers shall be housed in panels per Industrial Control Panels, and loops shall integrate to the control system per Control Systems Integration.

14.1.7Instruments shall be located for access to the local display and for removal of the probe or sensor without draining the vessel where practical; the mounting orientation shall match the manufacturer's drawing. instrument location plan

15 Delivery, Storage, and Handling

15.1Instruments shall be delivered in the manufacturer's original packaging with protective caps on process connections and antennas, and shall be stored indoors in a clean, dry, temperature-controlled space until installation.

15.2Radar antennas and guided-wave probes shall be protected from impact and bending during handling; a deformed antenna or probe shall be rejected.

15.3Submersible sensors shall have their cable ends sealed against moisture until termination.

16 Warranty

16.1The manufacturer shall warrant each level instrument against defects in materials and workmanship for a minimum of 24 months from substantial completion or 12 months from beneficial use, whichever is longer.

16.2SIL-certified devices shall retain their certified safety performance throughout the warranty period when maintained per the manufacturer's proof-test procedure.

17 Spare Parts

17.1The Contractor shall furnish manufacturer-recommended spare parts, including spare gaskets and process-connection seals for each instrument type and size installed.

17.2One spare transmitter electronics module shall be provided for each model type where more than five identical instruments are installed, to support field replacement without long lead time.

Spare parts packagecheckbox

☑ Spare process-connection gaskets/seals (per type)

☐ Spare transmitter electronics module (per model, qty > 5)

☐ Spare display module

☐ Spare intrinsic-safety barrier

Level Measurement