Recycling

plastic bottles 115082 1280

Foto by Hans on Pixabay

 

Efficient, durable, and resistant: In the recycling process, from disposal through processing to reuse, various aggressive chemicals are used in varying concentrations. An additional challenge is the frequently occurring corrosive air generated by waste incineration. In this demanding environment, reliability, safety, and high resistance to corrosive conditions are essential for the extraction of valuable secondary raw materials.

Robust measuring and monitoring instruments play a crucial role in ensuring the continuous and safe operation of recycling plants. These must be designed not only to provide precise measurements but also to withstand harsh conditions. Effective monitoring of process parameters such as temperature, pressure, and level is crucial for optimizing recycling processes and minimizing downtime.

In addition, advanced filtration systems and special coatings for plant components and sensors are required to mitigate the influence of corrosive substances and extend the equipment’s lifespan. By relying on such reliable and robust technologies, the recycling industry can not only increase safety for operators but also make a significant contribution to environmental protection by maximizing material recovery and reuse.

The level transmitter PASCAL Ci4 LEVEL is suitable for the
measurement of level, tank capacity and pressure in
atmospheric and pressurised vessels. The transmitter is
suitable for pressure measurement of aggressive, corrosive,
viscous, high-temperature or solidifying media



Datasheet

  • Reliable and cost-effective
  • Design per EN 837-1 or ASME B40.100
  • Nominal size 40 [1 ½"], 50 [2"], 63 [2 ½"], 80 [3"], 100 [4"] and 160 [6"]
  • Scale ranges to 0 ... 400 bar [0 ... 6,000 psi]
Datasheet

  • Long service life, robust
  • Cost-effective and reliable
  • To combine with WIKA diaphragm seals
  • German Lloyd approval
  • Scale ranges up to 0 … 1,000 bar
Datasheet
User Manual
User Manual

  • Good/bad indication through parameterisable digital display (red/green)
  • Compact size enables easy installation in narrow spaces
  • Optimised design makes OEM machine integration easier
  • Designed for rough demands of up to 50 g shock and -40 ... +125 °C [-40 ... +257 °F]
Datasheet
User Manual

  • Adjustable switch hysteresis
  • Setting ranges: 0.2 … 2 bar [3 ... 30 psi] to 30 ... 320 bar [450 ... 4,600 psi] and -0.85 ... -0.15 bar [-25 inHg ... -5 inHg]
  • Non-repeatability of the switch point: ≤ 2 %
  • Switching functions: Normally closed, normally open or change-over contact
  • Media: Compressed air, neutral and self-lubricating fluids and neutral gases
Datasheet

  • Zero point setting in front
  • Special connection location on request
  • Low scale ranges from 0 ... 25 mbar
Datasheet
User Manual

  • Measuring ranges from 0 … 0.05 to 0 … 1,000 bar
  • Non-linearity 0.25 % or 0.5 %
  • Output 4 ... 20 mA, DC 0 ... 10 V, DC 0 ... 5 V and others
  • Electrical connection: Angular connector form A and C, circular connector M12 x 1, cable outlet 2 m
  • Process connection G ¼ A DIN 3852-E, ¼ NPT and others
Datasheet
User Manual

  • Wetted parts from stainless steel
  • Resistant to all common refrigerants
  • Special case design for the best possible condensation tightness
  • Private labelling possible
Datasheet
User Manual

  • Industry 4.0-ready IO-Link sensor improves connectivity and diagnostics
  • Designed for rough demands of up to 1,000 g shock and -40 ... +125 °C [-40 ... +257 °F]
  • Optimised design makes OEM machine integration easier
  • Multicolour 360° LED status display simplifies troubleshooting and localisation
Datasheet
User Manual

  • Measuring ranges from 0 ... 6 bar to 0 ... 600 bar
  • Non-linearity 0.5 %
  • Standard industrial signals
  • Electrical connection: Angular connector form A and C, circular connector M12 x 1, Metri-Pack series 150, cable outlet 2 m unshielded or shielded
  • Many internationally customary process connections
Datasheet
User Manual

  • Measurement ranges 0 ... 3 kg up to 0 ... 250 kg
  • Made of aluminum alloy
  • High accuracy
  • High side load tolerance
  • Simple structure, easy to install
Datasheet
User Manual

  • Measuring ranges 0 … 20 kg up to 0 ... 500 kg
  • Made of aluminum
  • High accuracy
  • Insensitive to side and corner loads
  • Simple structure, easy to install
Datasheet
User Manual

  • Measuring ranges 0 … 0.3 kg up to 0 ... 10 kg
  • Made of aluminum alloy
  • High accuracy
  • Insensitive to side and corner loads
  • Simple structure, easy to install
Datasheet
User Manual

  • Measuring ranges 0 … 500 kg up to 0 ... 10.000 kg
  • Steel/stainless steel
  • High long-term stability
  • High side load tolerance
Datasheet

  • Measuring ranges 0 … 5 kg up to 0 ... 500 kg
  • Completely welded bellows
  • Protection class IP68
Datasheet

  • Measuring ranges 0 ... 2 kN up to 0 ... 100 kN
  • Corrosion-resistant stainless steel design
  • Integrated amplifier
  • High long-term stability, high shock and vibration resistance
  • Good reproducibility, simple installation
Datasheet
User Manual

  • Accuracy class 2 per EN 13190
  • Nominal size 63, 80, 100 and 160
  • Scale ranges from -30 ... +200 °C
Datasheet
User Manual

  • Measuring ranges from -50 ... +200 °C [-58 ... +392 °F]
  • Electrical connection via plug connection
  • Output signal 4 … 20 mA or 0 … 10 V
  • Factory configured
  • Measuring insert exchangeable
Datasheet
User Manual

  • Very compact design, high vibration resistance and fast response time
  • With direct sensor output (Pt100, Pt1000 in 2-, 3- or 4-wire connection) or integrated transmitter with 4 ... 20 mA output signal
  • Integrated transmitter is individually parameterisable with free-of-charge WIKAsoft-TT PC configuration software
  • Sensor element with accuracy class A per IEC 60751


Datasheet
User Manual

  • Scale ranges from -30 ... +500 °C
  • Large choice of nominal sizes from 25 ... 160 mm
  • Case and stem from stainless steel
  • 5 different connection designs
Datasheet
User Manual

  • Measuring ranges from -50 ... +250 °C [-58 ... +482 °F]
  • Very high vibration resistance
  • Compact design
  • Electrical connection via plug connection
Datasheet
User Manual

  • Loud internal audible alarm
  • Clear system integrity indication
  • Accepts industry standard 4-20mA inputs
  • Multiple units can be daisy-chained
  • Variable alarm configurations
  • Integral alarm outputs
  • Simple installation
  • Minimum maintenance
  • One button operation
Datasheet
User Manual

Crowcon’s enhanced Gasmaster gas detector control panel has a modular design meaning users only need purchase the required number of input modules. It can easily be extended by adding more modules at a later date.



Datasheet
User Manual

  • All day-to-day functions are available from the front panel – push buttons for simple operation
  • Unique bar-graph display per channel – provides instant representation of gas concentrations
  • Common alarm LEDs on the display card – the whole rack status can be checked at a glance.
Datasheet
User Manual

There are 3 addressable gas detection controller options, all with identical functionality but with different channel input capabilities.

  • GM16: 1-16 Channel inputs
  • GM64: 1-64 Channel inputs
  • GM128: 1-128 Channel inputs
All available as 19” rack mounted, with enclosure options available for GM16 & GM64. All of our addressable gas detection controllers are modular, so the controller can be configured exactly to requirements. Only include what is needed for the application to reduce complexity and cost.



Datasheet
User Manual

The Multiscan++MED control panel has been purposely designed and certified to meet with the requirements of the marine industry and can manage and monitor up to 64 gas detectors.



Datenblatt

The Multiscan++S2 is a SIL2 certified, advanced multifunction gas detection control panel designed to meet the need for highly flexible systems. The system can manage and monitor up to 256 gas detectors.

Datenblatt

Vortex is our most flexible gas controller package that can be customised to meet your site requirements, however complex, without the need for extensive cabling.

Datasheet
User Manual

Vortex FP and Vortex FP Compact are ATEX certified Exd Flameproof gas detector control panels for use in Zone 1 or Zone 2 hazardous areas such as on offshore production platforms or within refineries.

Datasheet
User Manual
User Manual

The SMART 3G-C2 is a SIL2 certified fixed gas detector ideal for a variety of industrial applications, capable of monitoring toxic, flammable and refrigerant gases in harsh environments and classified areas. Optionally available with ModBus RS485.



Datasheet

The SMART S-MS 3A is a SIL2 certified fixed gas detector ideal for flammable and toxic gas detection.

Datasheet

The SMART 3G-D2 is a SIL2 certified fixed gas detector ideal for  a variety of industrial applications, capable of monitoring toxic, flammable and refrigerant gases in harsh environments and classified areas.

Datasheet

The SMART S-MS MED is an MED approved and SIL2 certified fixed gas detector, designed to meet with the harshest conditions of marine environments.

Datasheet

  • Independently tested to EN50379. Meets the requirements of BS7967 and Gas Safe TB143
  • Longlife sensors lasting up to 6 years
  • Dilution to 30,000ppm CO
  • Optional NO sensor upgrade
Datasheet

  • Intuitive Messmenüs mit reaktionsschnellem Smart-Touch-Display
  • Inkl. O2- und CO H2-kompensiertem Sensor bis 8.000 ppm
  • Integrierte Feinstdruck-Messung
  • Dokumentation vor Ort und Protokollversand per E-Mail
  • Vielseitige Sonden und schneller Sondenwechsel durch Anwender
  • Magnethalterung zur Gerätefixierung
  • Effiziente, kabellose Parallelmessung von bis zu vier testo Smart Probes gleichzeitig
  • Praktische Second Screen Funktion und einfache Datenintegration in nutzerspezifische Software
Datenblatt
Bedienungsanleitung

  • Little installation effort
  • Minimum maintenance requirements
  • Extremely rugged design
  • High long-term stability through built-in, maintenance-free reference gas cell, field calibration is unnecessary
  • Real-time measurements
Datasheet

  • Process control (chemical industry) 
  • Process optimization (steel industry)
  • Safety monitoring, e.g. measuring minimum or maximum concentration limit for oxygen in explosive proof environment
  • Suitable for use in SIL 1 safety systems to 61508/IEC 61511
  • Combustion control (boilers, municipal waste incinerators)
User Manual

The Crowcon FGard IR3 flame detector is an explosion proof multi spectrum IR flame detector. FGard delivers superior performance, responding to hydrocarbon liquid fuel and gas fires at long distances.

The FGard IR3 delivers first-in-class flame detection with intelligent heated optics for clearer results and advanced optical verification to greatly reduce false alarms

Datasheet
User manual
User manual

Our new and improved portable multi gas monitor you can take almost anywhere.

Now with added industry leading sensor technologies to improve worker safety and cost you less over time.

Datasheet
User manual

  • Simultaneous measurement of NO and NO2 with subsequent compilation.
  • NO2 converters or CLD analyzers are therefore not required. This means:
    - Lower maintenance effort (no converter function check)
    - Reduced operating costs because no additional equipment is required, such as an ozone generator and the like 
  • Measurement in the UV range
    - Measurement not effected by H2O and CO2
    - Very low SO2 and NO measuring ranges possible 
  • UV Resonance Absorption Spectrometry (UVRAS)
    - Measurement of very low NO concentrations: Measuring range 10 ppm
    - Very low cross-sensitivity to other gases 
  • Very long service life of the UV light source
  • Low drift and high stability through four-channel measuring method with double quotient calculation
  • True reference measurement for drift-free, stable measurements
  • All modules “temperature controlled,” regardless of ambient temperature fluctuations
  • Optional calibration device
    - Filter wheel with test cells that can be swiveled into the beam path for calibration; no test gases required
    -Calibration: manual or automatic
Datasheet

  • Highly cost-effective because calibration gases are not required (AUTOCAL with ambient air, depending on the measuring component)
  • High selectivity due to multilayer detectors e.g. low cross-sensitivity to water vapor
  • Cleanable cuvettes: Cost savings through further use in case of contamination
  • Menu-guided operation in plain text
  • Open interface architecture (RS 485, RS 232; PROFIBUS, SIPROM GA): Simplified process integration; remote operation and control
Datasheet

  • Wide range of applications: in up to 100% H2O steam, for ultra-pure gas applications, for high-boiling components (up to 200 °C), in the presence of corrosive gases (with prefilter)
  • Extremely low cross-sensitivity to interfering gases 
  • Low consumption of combustion air 
  • Low influence of oxygen on measured value 
  • Warning and fault messages; in case of combustion gas failure, flame extinction, and pump and filter faults
Datasheet

  • Universally applicable hardware basis 
  • Integrated correction of interference gas, no external calculation required 
  • Open interface architecture (RS 485, RS 232, PROFIBUS) 
  • SIPROM GA network for maintenance and service information (optional) 
  • Electronics and analyzer part: gas-tight separation, purging is possible, IP65, long lifetime even in harsh environments (field device)
Datasheet

  • Short T90 time thanks to micromechanical Si sensor 
  • Universally applicable hardware basis, highly dynamic measuring range (e.g., 0 to 1%, 0 to 100%, 95 to 100% H2)
  • Integrated interference gas correction, no external calculation required 
  • Open interface architecture (RS 485, RS 232, PROFIBUS) 
  • SIPROM GA network for maintenance and service information (optional)
Datasheet

  • High degree of linearity 
  • Compact design 
  • Open interface architecture (RS 485, RS 232, PROFIBUS) 
  • SIPROM GA network for maintenance and service information (optional)
Datasheet

  • Integrated pump for reference gas delivery (optionally for ambient air, for example) 
  • High degree of linearity 
  • Compact design 
  • Physically suppressed zero point possible
Datasheet

  • Paramagnetic alternating pressure method: Small measuring ranges (0 to 0.5% or 99.5 to 100% O2), absolute linearity
  • Detector element has no contact with the measuring gas: can be used under “harsh conditions,” long service life 
  • Physically suppressed zero point by suitable reference gas selection (air or O2), such as 98 to 100% O2 for purity monitoring / air separators
  • Open interface architecture (RS 485, RS 232, PROFIBUS) 
  • SIPROM GA network for maintenance and service information (optional)
Datasheet

  • Corrosion-resistant materials in the gas channel (optional): Measurement possible in highly corrosive measuring gases 
  • Cleanable measuring chambers: Cost savings thanks to further use in case of contamination 
  • Open interface architecture (RS 485, RS 232, PROFIBUS) 
  • SIPROM GA network for maintenance and service information (optional)
Datasheet

  • High selectivity thanks to two-layer detector and optical coupler: reliable measurements even in complex gas mixtures
  • Low detection limits: Measurements at low concentrations
  • Corrosion-resistant materials in the gas channel (optional): Measurement possible in highly corrosive measuring gases
  • Cleanable analysis cuvettes: Cost savings thanks to further use in case of contamination
  • Electronics and physics: Gas-tight separation, purging is possible, IP65: Long service life even in harsh environments
Datasheet

  • Ideal for binary gases
  • Integrated interference correction, no external calculation necessary
  • High measuring range dynamics
  • Low detection limits in the measuring range of 0 to 0.5% with hydrogen
  • T90 time < 2.5 seconds
  • Maximum ambient temperature 50 °C
  • Easy-to-use, thanks to Plug & Measure
  • Ready for Industry 4.0
Datasheet

  • Long service life, since the microflow sensor does not come into contact with the sample gas and therefore cannot corrode
  • Low susceptibility to faults
  • Vibration compensation
  • T90 time 1.9 seconds
  • Maximum ambient temperature 50 °C
  • Small measuring ranges (0 to 0.5% or 99.5 to 100% O2)
  • Physically suppressed zero point, such as 98 or 99.5 to 100% O2
  • Easy-to-use, thanks to Plug & Measure
  • Ready for Industry 4.0
Datasheet

  • High measuring precision in complex gas mixtures
  • Low detection limits
  • Low maintenance costs thanks to on-site cleaning of the analysis chambers
  • Simplified interfering gas measurement
  • Preventive maintenance function
  • High selectivity due to two-layer detector
  • Easy-to-use, thanks to Plug & Measure
  • Ready for Industry 4.0
Datasheet

In addition to flexible modules, the innovative SIPROCESS GA700 series also includes a new housing type: the Ex d field device with pressure-resistant enclosure. It contains a field operating device consisting of an Ex d casing with attached Ex e connection housing plus a connected Ex d field module.



The new SIPROCESS GA700 series of gas analyzers makes it possible to combine up to two modules in one housing: in either a wall-mounted housing or in a 19" rack housing with three different height units, depending on individual requirements.

Datasheet

Meet the next generation of flammable gas detection. 

Xgard Bright is a versatile platform offering flammable and toxic gas detection and oxygen monitoring, while providing ease of operation and reduced installation costs. Providing analogue 4-20mA and RS-485 Modbus signals as standard, Xgard Bright comes with an Alarm and Fault relay as standard as well as optional HART communications. Lowering the cost of installation, the 4-wire addressable implementation drastically reduces cabling requirements. The large OLED display allows users to easily work with Xgard Bright during install, calibration and routine maintenance without the need to open the housing. The Xgard Bright is now available with MPS (Molecular Property Spectometer™) technology. Wide range of new gases and sensor types are now available and have been added to the configurator. If you cannot see your gas or range required, please contact Crowcon to discuss options



Datasheet

TXgard-IS+ is a Intrinsically Safe (I.S.) toxic and oxygen gas detector with local LCD display. A very wide choice of sensors are available for use in a variety of applications. TXgard-IS+ is ATEX certified for use in Zone 0,1 or 2 hazardous areas and also UL and cUL certified for use in Division 1 or 2 hazardous areas.

Datasheet

A flameproof (Ex d) pellistor based detector with display & 4-20mA output, for hydrocarbons, hydrogen & petrol vapours.

Datasheet

TXgard Plus is a flameproof (Ex d), ATEX, IECEx certified toxic or oxygen gas detector with local LCD display. A choice of sensors are available enabling use in a wide range of applications, including water treatment, oil and gas exploration, chemical plants and steel production.

Datasheet

IRmax is an ultra-compact infrared (IR) gas detector that delivers rapid, fail-safe detection of hydrocarbon gases and vapours. The IRmax gas detection system offers the choice of a detector only, a local gas/status display, a remote gas/status display or non-intrusive calibration via an I.S. calibration tool or hand-held HART communicator.

Datasheet

The new XgardIQ, our most intelligent fixed-point gas detector, increases safety by minimising the time operators must spend hazardous areas. This versatile transmitter and gas detector has a range of features that protect engineers and support facilities managers of oil, gas, chemical & petrochemical plants to name a few. Available fitted with a variety of flammable, toxic or oxygen gas sensors. (SIL-2) Safety integrity level 2 certified gas detector.

Datasheet

The Xgard range is a comprehensive selection of fixed point gas detectors that meet the diverse requirements for gas detection in industries throughout the world. This includes many water treatment, oil and gas, power, research facility and manufacturing installations.

Datasheet

Available for detecting a range of different refrigerant gases and also sulphur hexafluoride (SF6), the F-Gas Detector can be connected to any control system that accepts an analogue signal.

Datasheet

I-Test is Crowcon’s fully automated solution for testing and verifying that your Gas-Pro and T4 are in a compliant state to carry out your daily work. Bump testing standards are getting tighter in all regions and the need for controlled bump and calibration records is a must. I-Test and the accompanying I-Test manager software makes this as easy as can be. It takes less than 1 minute to complete a bump test!

Datasheet

With regulations driving tighter calibration routines and the requirement for daily bump testing, there is a real need for test gas. Gas detectors play a key part for people and plant safety so equipment cannot afford to be out of service.

Datasheet

The LaserMethane mini (LMm) is an innovative long-range portable detector which allows methane gas to be detected at distances of up to 100m. This enables easy access to hard-to-reach locations, such as elevated piping or locked premises, and helps keep the operator away from potential leak sources. Latest development – LMm is now available with Bluetooth connectivity. Previously only available in a ‘safe-area’ version, Bluetooth is now an available option for the ATEX approved LMm. This allows connection to an Android device using the GasViewer app delivering data storage functionality. This means that important survey data including gas level, time, date and location can be combined, saved or emailed to a central point.



Datasheet

Detective Wireless is a module that can replace interconnecting cables for Detective+. Detective Wireless will transmit gas alert signals and other alarms wirelessly between Detective units using a 433MHz signal up to 100 metres in distance.



Datasheet

Detective+ is a multi-gas temporary area monitor for use in turnaround/shutdown procedures, hot work maintenance, confined space entry work and many other utility, construction and oil and gas industry applications. Go solo or link together using Detective Net to form a perimeter, Detective+ gives a loud and clear alarm providing effective warning of gas hazards. The rugged, water and impact resistant design make Detective+ the ideal choice for your transportable gas detection needs.



Datasheet

Clip Single Gas Detector (SGD) is designed for use in hazardous areas and offers reliable and durable fixed life span monitoring in a compact, lightweight and maintenance-free package. Clip SGD has a 2-year life and is available for hydrogen sulphide (H2S), carbon monoxide (CO) or oxygen (O2). Clip SGD is designed to withstand the harshest industrial working conditions and delivers industry leading alarm time, changeable alarm levels and event logging as well as user-friendly bump test and calibration solutions.



Datasheet

The Gasman full function personal single gas monitor is compact and lightweight yet is fully ruggedised for the toughest of industrial environments. Featuring simple single button operation, it has a large easy-to-read display of gas concentration, and audible, visual and vibrating alarms.



Datasheet

The Tetra:3 multigas monitor is a compact, robust and easy-to-use diffusion based detector. Single button operation, small size and clear top-mounted display make it a favourite in the market amongst those working in demanding industrial environments, such as those in the water, telecoms, food, brewing or hydrocarbons sectors.



Datasheet

Portable 4 gas detector provides effective protection against 4 common gas hazards: carbon monoxide, hydrogen sulphide, flammable gases and oxygen depletion. Now with improved detection of pentane, hexane and other long chain hydrocarbons. Offering you compliance, robustness and low cost of ownership in a simple to use solution. T4 contains a wide range of powerful features to make everyday use easier and safer.



Datasheet

Gas-Pro is a confined space entry monitoring solution for workers and fleet managers, and is now supported by the I-Test bump test and calibration station.



Datasheet

The Gas-Pro IR is ideal for the oil and gas industry. This personal multigas monitor can detect methane, pentane or propane using infrared (IR) sensor technology. The Gas-Pro IR is ideal for detecting potentially explosive gases where traditional, ”pellistor”, catalytic sensors will struggle – especially in a low oxygen environment.



Datasheet

Gas-Pro PID utilises the Photo Ionization Detection technology to allow you to detect hundreds of Volatile Organic Compounds (VOCs). If you are working in an environment that is high in levels of solvents, glues, paints and general VOCs, the Gas-Pro PID will monitor your safety. With its dual-coloured display, the monitor will alert the user with its 95db audible alarm and its dual-coloured visual alarm bars.

Datasheet

Gas-Pro TK dual range portable monitor measures the concentration of flammable gas in inerted tanks. Available for methane, butane and propane, Gas-Pro TK uses a dual IR sensor – the best technology for this specialist environment, which means Gas-Pro TK dual IR:

  • Isn’t inhibited by high hydrocarbon concentrations unlike catalytic bead sensor;
  • measures gas in high %vol as well as %LEL concentration, which single IR sensors can’t;
  • auto-ranges switch between %vol and %LEL measurement, so always operating to the correct parameter.
Gas-Pro TK keeps you up-to-the moment with oxygen concentrations in the tank; telling you when the oxygen levels are;
  • low enough to load and store fuel safely;
  • high enough for safe tank entry.
Datasheet

Air flow measurements in ducts, temperature measurements in laboratories, humidity measurements in production, pressure difference measurements in clean rooms. The testo 480 digital temperature, humidity and air flow meter comes with a wide range of optional sensors that allow you to measure, analyse and log these and a variety of other parameters with only one device

Datasheet

  • In combination with testo 330-2 LL, the innovative complete solution for solid fuels, oil and gas systems.
  • Unrestricted TÜV test for the limit value levels 1/2 and according to VDI 4206 Sheet 2
  • Parallel measurement of fine particles, O2 und CO
  • Graphic presentation of all measurement values in real time
  • Especially economic in operation and maintenance
  • Effortless handling and easy transport
  • High-tech in a case: Measurement of all relevant values with only one probe
Datasheet

  • Handy and robust Easily possible to carry to the desired application site
  • Determination of soot concentration (mg/m3) as well as Filter Smoke Number (FSN) or Bosch number
  • Easy one-handed operation
  • Direct analysis and display of measurement values, optional on-site printout of data with Testo fast printer
Datasheet

teste 308 smoke tester, incl. rech. battery, mains unit and calibration protocol. Measuring range - 0 to 6 RZ Accuracy - 0.2 RZ Resolution - 0.1 RZ

Datasheet