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Posted on September 30th, 2016 by vapro

Below are some of the most common questions and answers about ClausTemp Products. Please reference this FAQ for quick answers to common questions about our products. Contact us if you have any questions about ClausTemp products that are not addressed in this FAQ.

Thermocouple Models HTP and HTX FAQ

Does the flush gas through the HTP/HTX Thermocouple junction have a cooling effect?

Field tests indicate that there is nearly no loss of temperature due to the low flow of the flush gases. The normal flush flow (approx. 10 lph) is simply too low to create a measureable cooling effect. To verify this, close the flowmeter needle control valve on the Model HFS Flush Gas Station coupled to the thermocouple in service and observe the increase in the temperature indication. Wait a few minutes and return to the proper flow rate and again observe the temperature reading. If flow rates higher than that controlled by the Model HFS are used, the cooling effect would become quite noticeable.

Delta recommends a 6” nozzle be utilized for installation of the HTP/HTX. Why not a 4” nozzle or smaller?

It is a matter of maximizing the annular space around the collar of the outer Refractory Well and the Inner Diameter of the nozzle and for ease of installation of the nozzle insulating components.

A 6" Sch 80 nozzle provides 1.5 inches of annular space between the Refractory Well collar and the I.D. of the nozzle. This allows plenty of space for installation of the packing material around the collar of the Refractory Well.

A 4" Sch 80 nozzle leaves a 0.5 inch space between the Refractory Well collar and the I.D. of the nozzle, adequate space but not optimum.

The 6" nozzle size is preferred. 4" nozzles are acceptable.

What is the recommended nozzle projection height?

Nozzle projection height should be as short as possible.  Ideally, the mounting flange should be positioned below the external thermal management system (weather shield), keeping the temperature of the nozzle closer to that of the vessel shell design temperature. It is recommended that the weather shield be fabricated in a manner to cover or surround the nozzle and flange with removable panels to gain access to the mounting flange whenever necessary.

A 6.0" (152 mm) nozzle projection is ideal.

Delta recommends that installations be vertically down on the top centerline of the vessel. Why not off center?

Time and our experience has proven that vertical installations on the top centerline prove to be most reliable over the long term.

The top centerline usually places the thermocouple nozzle in the external thermal management system (weather shield) vent along the top centerline of the vessel. This is ideal since the thermocouple and mounting nozzle temperature is kept closer to that of the vessel shell design temperature, minimizing corrosion. If the top works of the thermocouple interfere with a vent roof, it is perfectly acceptable to make a provision for the thermocouple terminal housing to extend through it.

The top centerline location simplifies the physical installation.  

Are the HTP/ HTX Thermocouples ATEX certified?

The HTX model carries the ATEX certification Ex II 2 d IIB + H2T3.

Does a thermocouple always indicate lower than an adjacent Infrared pyrometer?

No. But rarely do they indicate the same temperature unless the IR device is adjusted to do so (which is sometimes recommended). A thermocouple is inherently accurate; its output is directly related to temperature and it can never read erroneously high. An Infrared device measures the intensity of infrared energy and infers temperature. There are many factors involved in the accurate measurement of temperature in a Claus Thermal Reactor. The thermocouple, however accurate, is intended to measure the temperature of the hot face of the refractory. The vessel shell is constantly losing heat through convection and radiation. The HTP/HTX’s Refractory Well conducts heat up towards the nozzle. The inner Element Well also conducts heat up into the HTP/HTX body. This conductance of heat slightly lowers the temperature of the thermocouple junction located inside of these thermowells.

Another factor (for both Thermocouple and Infrared Pyrometer) is the mounting location of the measurement devices. Currents and vortices within the vessel may create very large disparities in temperature at differing locations within the vessel. To assure that temperatures are properly monitored, it may be wise to obtain a CFD modeling of the vessel.

Thermocouples accurately measure the temperature, but in only one small spot. Due to light reflections, pyrometers tend to provide more of an average temperature in the region of the vessel where it is positioned but with some emphasis of the point to which the lens is aimed.

Is it necessary to constantly supply the flush gas through the HTP/HTX?

Yes. Failure to maintain the proper flush flow and pressure will, in time, result in failure of the HTP/HTX. Temporarily stopping the flush flow will not cause immediate harm.  Without proper flow over many months, it could begin to exhibit a declining signal vs. temperature due to corrosive reaction gas elements that migrate through the wall of the Alumina ceramic Inner Element Well and slowly attack the thermocouple wires. The DModel HFS Flush Gas Control Station eliminates this problem by providing a simple and proper installation that conveniently monitors the pressure and flow rate.

Must the flush gas be Nitrogen?

Nitrogen is preferred. If not available, clean dry instrument air may be used. It is very important that there be no moisture or hydrocarbons in the flush gas.

Nitrogen has proven to be the superior flush gas.

Why is it necessary to have thermocouples in addition to Infrared measurement devices?

Thermocouples are inherently accurate and require no maintenance. However, in some installations where the IR devices measure the gas temperature only, thermocouples may be slower to respond to temperature changes. Thermocouples may be damaged under certain abnormal conditions as such improper installation, excessive thermal shock, severe over-temperature conditions, stopping the purge for long periods of time or shifting of refractory. Traditional IR units in Claus service historically require periodic maintenance while in service including cleaning of lenses, rodding out the sight bore and verification of the temperature via an inserted thermocouple. In addition, the traditional IR manufacturer normally recommends the units be returned to the factory annually for a complete checkout and re-calibration, a costly process requiring the installation of a “back-up” IR unit. By maintaining a comparison of the readings of the thermocouples and IR devices, the requirement for maintenance, be it more or less frequent than normally recommended, is easily determined. (The Delta Controls HIR Infrared Pyrometer, designed exclusively for Claus service, solves the maintenance problems required of traditional IR devices).

The advantage of the thermocouple vs. the infrared device is that the thermocouple, properly installed and operated, does not require regular maintenance or periodic calibration. It will maintain its accuracy over a long period of time.

In an application as severe, demanding and potentially hazardous as a sulphur reactor, redundant measurements are highly desirable. Using two different technologies also eliminates common-cause failures.

Then why is it necessary to have Infrared Pyrometers in addition to Thermocouples?

Thermocouples are vulnerable to different upset conditions and can fail under different conditions as explained in “What can cause the HTP/HTX to fail in service?” shown below. This being the case, if a severe upset condition occurs that caused damage to a thermocouple, the condition will not likely cause a failure of an IR device. If the IR device signal is continually and frequently compared to the thermocouple measurement, a pattern can be established and can show the comparative readings over time. This data can then be used to determine the time interval for the need for IR maintenance and cleaning. Adhering to the maintenance schedule developed with the thermocouple, the SRU can remain in service.

Ideally, both Thermocouples and IR devices should be employed. And all elements of the thermocouples should be monitored as well, since this makes use of the thermocouple’s “self-monitoring” feature.

Why is the thermocouple so slow to respond to temperature changes as compared with IR?

This is not necessarily true. If an IR device is set up to read the refractory hot face temperature (as most installations are), the thermocouple may be slightly faster to respond to temperature changes. The reason is that the solid thick ceramic refractory materials contain a tremendous amount of heat. The result is that in conditions where the gas temperature changes, the refractory must dissipate the stored heat, normally outward to the vessel shell. The thermocouple, on the other hand, has relatively thin wall thermowells that are attached to the mounting flange and more readily conduct heat to the cooler areas. IR devices set up to measure the gas temperature will respond much faster than the thermocouple, but such IR devices are easily upset by changes in absorption due to changing gas compositions.

What can cause the HTP/HTX to fail in service?

In order of frequency:

  1. Improper installation
    1. Improper dimensions specified or vessel/refractory not installed to specified dimensions
    2. Failure to utilize proper installation components:
      1. Model HNP Nozzle Packing Kit
      2. Model HRW Refractory Well
  2. Failure to maintain purge flush pressure and flow over extended periods
    1. Improper piping of pressure regulator and flowmeter/flow control valve resulting in no back pressure of purge path
    2. Loss of flush gas supply for extended periods
  3. Significant movement of the refractory relative to the vessel shell or movement of the firebrick layer relative to the back up (insulating) lining (may be caused by severe over-temp conditions or improperly installed refractory)
  4. Accidental dropping or damaging the HTP/HTX during handling or installation
  5. Sudden insertion into a very hot reactor
  6. Thermal shock, quench (in severe overheat conditions)
In what way can “Improper Installation” result in failure of the HTP/HTX?

Attention to dimensional detail is important in realizing the benefits of the HTP/HTX. The primary reason for early failure is caused by undue physical mechanical forces, primarily because of improper installation resulting in improper clearances. It is important that the thickness of the refractory, the height of the nozzle and the I.D. of the nozzle be furnished to Delta Controls prior to ordering. Each HTP/HTX is custom built to the exact dimensions of the vessel. Building a unit to incorrect dimensions may cause failure or inaccurate measurement.

The bore through the refractory must be of the proper I.D., on center and perpendicular to the mounting flange face. If the vessel is to be relined with refractory, it is recommended that the Delta Controls Model H6G Refractory Drilling Kit be utilized to provide the proper bore. Prior to installation, it is important to check the inside of the nozzle to make certain that no refractory material is forced up into the nozzle beyond the inner surface of the vessel shell. If this occurs, the large outer Refractory Well (model HRW) will not seat to the proper depth, leaving insufficient clearance for the tip of the inner Element Well. It has been observed that this condition can cause the Element Well to break through the tip of the outer Refractory Well during installation of the HTP/HTX.

More often, failure is caused by improper re-installation after the unit is removed for vessel maintenance. It has been reported many times that during re-installation, the installer does not have a replacement Refractory Well or the nozzle insulating materials. In several cases, insulating castable or wool has been placed in the nozzle around the Element Well instead of the proper insulating rings. Installation in this manner will sometimes result in failure within a month or two as solid sulfur accumulates inside the nozzle. This sulfur build up is physically very hard and strong; if subsequent expansion/contractions occur, this solid sulfur may break the Element Well. The solid insulating rings supplied with the Delta Model HNP Nozzle Packing Kit are used to take up space in the upper cooler area in the mounting nozzle, preventing the accumulation of large volumes of sulfur. The rings are not strong enough to break the well.

With improper installation, failure may occur as the vessel is brought up to operating temperature, Improper refractory installation combined with severe over temperature conditions may cause significant movement of the refractory relative to the vessel shell, to which the HTP/HTX assembly is mounted and rigidly connected. As the refractory shifts, the Element Well could be forced against the side of the outer refractory well that rests in the refractory and the element well could then become broken, allowing the vessel gases to come in direct contact with the thermocouple junction; failure is then imminent, but usually not for a month or two. This problem has nearly been eliminated as refractory technology has improved and with the use of the Installation tools supplied by Delta Controls (i.e., Model H6G Refractory Drilling Kit)

How can improper piping of the flush gas components cause failure?

Long term reliability requires that the thermocouple be properly flushed, maintaining both the proper back pressure and flow rate throughout the thermocouple flush passages. Delta Controls offers the Model HFS Flush Gas Control Station for this purpose.

In order to maintain the positive pressure in the purge path through the HTP/HTX, a pressure regulator is connected to the upper inlet port of  the HTP/HTX thermocouple. The pressure is set to approximately 5 PSI (0.34 Bar) above the maximum expected vessel operating pressure. In order to maintain this pressure through the HTP/HTX, a flowmeter/needle control valve assembly is piped to the thermocouple’s lower outlet vent port. Controlling the flow rate by the needle valve creates sufficient back pressure through the thermocouple element. The flow rate must be maintained at approximately 10 lph, which assures that excessive purging does not cool the thermocouple elements.

Incorrectly placing the flowmeter/needle valve assembly upstream of the HTP/HTX would leave the purge path in the HTP/HTX at atmospheric pressure. This would then encourage the vessel gases to leak into the purge path through any tiny cracks or voids, since the vessel operates at an elevated pressure compared to atmosphere. 

If the HRW Refractory Thermowell is broken, will the thermocouple element always fail?

No. The outer Refractory Well merely protects the inner Element Well from physical harm (flying debris and thermal shock). Breakage of the Refractory Well, however, leaves the element well unprotected and subject to possible damage.

If the HTP/HTX inner Element Well becomes broken, will the thermocouple element always fail?

A failure of the inner Element Well will always result in thermocouple failure, although it may take a month or two to notice the drop in temperature signal. However, the thermocouple may fail even with the Element Well intact if either the flush gas flow or pressure has been lost for a long period of time. The loss of the flush gas permits the reactor gases to migrate through the wall of the inner element well and contaminate the element wire.

What will occur if the inner Element Well becomes broken? Will reactor gases escape to atmosphere?

The question frequently arises regarding what occurs if there is a failure of the inner Element Well. The Element Well is a pressure containment component of the HTP/HTX. If it becomes broken, vessel gases are free to travel into the purge outlet vent cavity.

If and when this occurs, the reactor gases will immediately begin to flow to the outlet vent port leading to the flowmeter/valve of the HFS. In Claus service, the exiting leaking gases will immediately be cooled as they pass to the outlet purge port and begin to precipitate into liquid/solid sulfur, which over a short time will clog the outlet purge port orifice as it flows towards the downstream flowmeter/needle valve assembly. Prior to the sulfur totally clogging the outlet port, this flow of sulfur gas remains limited to the low flow purge rate set by the flowmeter needle control valve located downstream of the outlet vent port. The proper flow rate is approximately 10 lph. Actually, if the Element Well has failed, this flow rate will be much lower than the set purge flow rate since the gas pressure is now equal to the lower operating pressure of the vessel, not the elevated purge pressure set at the regulator.

If there is evidence of element well failure, manually close the needle valve on the flowmeter to stop the gas flow.

How can it be determined if the Element Well has failed?

If flush gas pressure is properly set and the flowmeter is reading the proper flow rate then the Element Well, a pressure-containing component, is intact.

A sudden decline of the thermocouple output signal indicates that it is likely that the inner Element Well has failed. Breakage of the Element Well immediately permits the highly corrosive vessel gases to come in direct contact with the thermocouple wires and hot junction. Corrosion immediately begins to attack the thermocouple wires and corrosion failure begins. It is likely that the HRW Refractory Well has failed permitting physical damage to the inner Element Well. The Refractory Well failure is usually the result of severe thermal shock such as from a steam or liquid injection or physical damage to significant shifting/breakage of the refractory.

Slow degradation of the thermocouple output indicates that over time, the reactor gases have corroded and poisoned the thermocouple element. This slow degradation is a result of the reaction gases entering the Element Well either through a small crack in the well or in its seal. For this to have occurred, the purge pressure and/or the purge flow probably were not operating properly for many months. And, it is probable that the Element Well is intact.

The purge itself is an indicator of the condition of the Element Well as follows:

  1. If the purge flow has ceased and cannot be restored, it is likely that the outlet purge path has become clogged with solid sulfur. This sulfur has likely precipitated from the sulfur gases that have leaked into the purge pathway through a fault in either the Element Well or the Element Well seal. This may happen if the purge pressure is not maintained. Sulfur and other gases slowly migrate in through the wall of the Element Well over a period of time by diffusion. This is a normal phenomenon and normally causes no harm since the purge flow constantly carries these corrosive elements away from the T/C before any corrosion occurs. Failure due to this migration of corrosives is likely to have occurred if the purge flow or the purge pressure has not been maintained.
  2. If the purge pressure can be maintained and there is no flow (i.e., valve closed), the Element Well is probably intact.
  3. If the purge pressure reads approximately the same as the vessel pressure and cannot be effectively elevated, the Element Well has failed and purge gas is flowing into the reactor. In this case, there will be no purge flow to the flowmeter since the outlet vent port will be clogged by sulfur (see below). In this case, repair of the HTP/HTX will have to be withheld until the reaction is shutdown, and the HTP/HTX assembly removed and repaired.
How can the accuracy of the Thermocouple element be verified?

Normally, a thermocouple can only be effectively checked with the use of another thermocouple. Delta HTP/HTX thermocouples are normally furnished with multiple elements, continuously providing redundant output signals. It is not possible to directly verify the accuracy of a thermocouple with an Infrared device (Delta Model HIR or any other.) Since the thermocouple is a spot temperature measurement, and an infrared device measures an average temperature of the surrounding area (due to reflections), it is possible that a properly working thermocouple will read a different temperature than a pyrometer that is pointed directly at the thermocouple.

However, if the thermocouple is compared to the pyrometer over time, a trend can be noted. Changes in the trend can indicate developing problems. For example, a decreasing thermocouple indication relative to the pyrometer can indicate that the thermocouple is becoming corroded. A decreasing pyrometer indication relative to the thermocouple can indicate that the pyrometer window is being coated with sulfur.

A simple and convenient means to check either the HTP/HTX thermocouple or the HIR Pyrometer is via the use of the CLAUSTEMP® Model HIP Handheld Infrared Pyrometer.

Can the HTP/HTX Element Well be replaced while the HTP/HTX is in service?

No. The entire assembly must only be removed when the reactor is not in service.

Pyrometer Model HIR FAQ

How does the HIR eliminate problems associated with build-up on the viewing window and in the nozzle?

The insulated steam jacketed lens assembly, along with the heat from the vessel, keeps the pyrometer viewport at a temperature above the condensing point of the gases in the reactor, eliminating the possibility of them depositing on the viewport. It is also essential that the vessel nozzle not be purged, as this would cool the nozzle and lens assembly, encouraging the formation of sulfur that could build up in the nozzle and form a thin layer of sulfur on the viewport window glass. With either of these conditions, the IR energy pathway would be attenuated, causing a deterioration of accuracy.

What is so important about some routine occasional maintenance to clean a window or a nozzle?

Beyond the man-hours, logistical and permitting issues, it requires that the block valve be closed and tested, the lens assembly removed, the lens glass cleaned and re-assembly.

If the nozzle is blocked with sulfur debris or frozen sulfur, the lens assembly must be removed as above, a “pushrod / packing gland assembly” installed and the debris pushed though the hole in the refractory into the vessel to open the port. The lens assembly is then re-installed.

More than one refinery has announced that they prohibit these maintenance routines whereby the nozzle must be opened.

The Delta Controls HIR is designed to be operated at high temperature with no nozzle purge which eliminates the need for this type of maintenance.

The HIR uses a fiber optic cable to connect the lens to the remote sensor. Why is this preferred to an integrally mounted unit?

This remote mounting removes the sensor from the rigors of the nozzle mount, excessive heat and vibration, assuring years of trouble free, calibration free, accurate operation. In addition, this design eliminates the need to purge or cool the nozzle and permits use of the steam jacketed heated lens assembly. Cooling of the nozzle is undesirable for two basic reasons:

  1. It is recommended that the shell temperature (as well as nozzles) be maintained ideally at between approximately 175°C and 315°C (350ºF and 600ºF) to minimize corrosion.
  2. Cool purge gas encourages the condensing of sulfur from the reaction gases as they circulate in the nozzle, eventually coating the viewport glass and/or obstructing the IR energy pathway between the reaction furnace and the sensor.
Infrared Pyrometers are normally purged in Claus service. Why does the HIR not require a nozzle purge?

The traditional reason has been to dilute the reaction gases in the cool nozzle to lessen the problem of sulfur condensing and building up in the nozzle and coating of the lens window (requiring periodic maintenance to clean the window and restore accuracy). However, the nozzle purge cools the nozzle and encourages condensing of the reaction gases forming trace amounts of sulfur. In addition, the cooling also creates an environment whereby corrosion to the nozzle will occur. The vessel shell of a Claus Furnace is normally designed to have a shell temperature of between approximately 175°C to 315°C. The refractory and shroud are designed to uniformly maintain this temperature to minimize corrosion and prolong the life of the vessel. The same issue occurs with nozzles and they, too, should be kept at a temperature as close to the shell temperature as possible. The HIR utilizes three methods to maintain this temperature: 1. Steam jacket the lens housing. 2. Install short nozzles (ideally position the mounting flange beneath the shroud). 3. Insulate the nozzle, block valve and lens housing. And no nozzle purge should be used. A nozzle purge produces a cooling effect and defeats the attempts to maintain adequate heat.

Also, purging the nozzle produces a cool environment at the base of the nozzle and in the refractory bore which the IR device detects and which causes a lower than actual temperature measurement (the IR device cannot totally ignore this cool area). The more the purge flow, the more the cooling effect. The Delta HIR does use a very low flow purge in the lens assembly that is directed through small ports at the lens window to prevent dust or ash from collecting on the window surface. This low flow purge is preheated by the steam chamber to prevent cooling.

Why does Delta offer different temperature ranges?

The usable measurement range is determined by the wavelengths of light that the instrument measures, with longer wavelengths allowing lower temperature measurements. There are only a few wavelengths where the reaction gases are transparent enough to not interfere with the refractory temperature measurement. Originally, the HIR was offered only with the “C”-range of 800°C to 1700ºC (1472°F to 3092°F). This is considered the useful range in a Claus furnace. Some customers wished to have a wider range that offered some readability for refractory dry-out, so the optional “D”-range of 300°C to 1700ºC (572°F to 3092°F) was made available at additional cost. In 2014, the “F”-range HIR was introduced which measures light at both the “C”-range and “D”-range wavelengths. By doing so, errors caused by partial occlusion of the sight path can be minimized or eliminated (for temperatures above 800°C only; below 800°C there is not enough infrared energy to activate the “C”-range sensor and the “F”-range transmitter reverts to “D”-range performance.)

Delta optionally offers an extended maximum range of up to 1925°C (3500ºF) to enable operators to measure higher than normal temperatures during an upset condition to assess the possibility of damage to the vessel.

It is claimed that the HIR does not require periodic calibration. How is this possible?

Delta Controls uses a sensor that exhibits very low drift due to aging.

How far can the sensor electronics be mounted from the lens?

The armored fiber optic cable is 3 M in length (approximately 10 feet), and so the electronics should normally be mounted within this cable distance from the vessel-mounted lens. If a longer distance is desired, it is possible to mount the fiber optic adapter within 3 M distance of the lens and extend the electrical wiring between the electronics and the fiber optic adapter (using suitable flameproof conduit) up to 30 M. Further extension may even be possible, but has not been tested. Delta recommends the standard 3M fiber Optic cable length be used.

Does the HIR require purging?

No purge to the electronics module or into the vessel nozzle is needed or recommended. (See Paragraph 4). However, the “Hot-Lens” assembly is fitted with a small purge port for the purpose of preventing dust or ash from clinging to the inside surface of the viewport window. The purge rate is approximately 28 LPM. This purge is pre-heated in the steam chamber prior to entering the view port area so that it does not cool the glass or the lens body.

How is the bore hole in the refractory and nozzle cleaned?

Cleaning of the bore through the refractory is normally never necessary providing the steam supply to the lens body is maintained. Over the years, experience has proven that the HIR’s steam jacketed design along with the recommended insulating of the entire nozzle, valve and lens assembly effectively keeps the bore through the refractory clean. This is accomplished by providing sufficient heat to keep the reaction gases from condensing sulfur and hardening in the nozzle.

What can cause the HIR to become inaccurate?

In order of frequency:

  1. Buildup of material in the nozzle bore through the refractory. This may result over time if there is a failure of the steam supply to the lens body or if the insulation is removed from the nozzle/lens assembly. Normally, the heat from the steam jacket of the lens assembly and pre-heated purge along with the reaction furnace temperature keeps the nozzle and valve hot enough to prevent collection of sulfur and debris in the nozzle. Also, the entire nozzle, block valve and lens body is insulated.
  2. Failure to maintain steam on the lens body permitting the view port to cool down and collect a thin coating of condensed sulfur.
  3. Misalignment of the fiber optic lens through the view port. Requires re-alignment of the lens, a simple procedure.
  4. In some installations, particularly those incorporating supplemental O2 may exhibit a tendency to “carbon block”, whereby carbon can concentrate in the nozzle and block the IR energy pathway. If this occurs, a N2 nozzle purge must be established.
  5. Build-up of material in the block valve and/or nozzle due to environmental cooling. While the “Hot-Lens” steam body can keep the lens at a high enough temperature to discourage sulfur build-up, rain, snow, wind, etc. can cause enough cooling of the block valve (and the mounting nozzle if it is a long one) to allow build-up. Delta Controls recommends that insulation be installed over the nozzle, block valve and “Hot-Lens” assembly to assure that sufficient heat is maintained along the optical path under all conditions.
In what way can improper installation result in failure of the HIR?
  1. Failure to provide 50–100 # steam to the lens assembly. Without the steam, expect that manual cleaning of the viewport glass and possibly the bore through the refractory may be required periodically.
  2. Failure to properly locate the hole through the refractory will cause interference with the infrared energy path to the lens. Delta Controls offers the tools to properly locate this pathway (drilling equipment (Model H3G) or mandrel (Model HRM).
  3. Excess bending or kinking of the armored interconnecting fiber optic cable in a manner that damages the inner core.
Can the HIR be installed without the use of steam?

Yes. However, the viewport window will become occluded as other manufacturer’s models do over time causing a degradation of accuracy. It will then be necessary to close the valve, remove and clean the lens assembly. Also, without the steam heated lens and nozzle, condensed sulfur and debris may accumulate in the bore through the nozzle and may partially block the IR energy pathway. To remove this blockage, it is necessary to remove the lens, mount a “rod-out” assembly, open the block valve and physically push the obstructing debris into the reactor. Using the recommended steam solves these problems.

What will occur if the viewing window becomes broken? Will reactor gases escape to atmosphere?

If the lens cable assembly remains tight in the body, there will be only trace leakage. If leakage is detected, the block valve is then closed and the leak site repaired.

Is the HIR available in any other configuration than measuring the temp on the hot face of the refractory?

Normally, no. Measurement of the refractory was chosen because it is least affected by changes in gas composition. The Primary objective of the HIR is to monitor the hot face of the refractory, reliably and with freedom from costly maintenance. If desired, however, Delta can provide other configurations.

Is there a viewing port for the operator?

No. In the interest of minimizing cost and maximizing safety, this feature was not included in the design. Delta recommends the use of a conveniently located auxiliary view port (which may be equipped with a Delta Controls “Hot-Lens” to prevent coating of the glass.) If necessary, the fiber optic cable lens may be removed from the alignment collar and the interior of the vessel may be viewed through the lens window.

Is the HIR explosion proof?

Yes. The standard unit is ATEX certified Ex ‘D’ 2C T6 IP65 and is CSA approved for Class 1, Div 1, Groups B,C,D and NEMA 4. NEMA 4X is available with either all stainless steel construction or epoxy coated cast aluminum. It does not require a purge.

Is the HIR available with alarm contacts?

The “F” range HIR does provide an alarm output. The output is an optoisolated phototransistor output (30v 100mA max). The normally closed output opens on alarm. Conditions that will trigger alarm are: High Temperature, Low Temperature, Sight path occlusion detected and Loss of Loop Power.

What power is required for the HIR?

24 VDC (Loop Powered). There is no requirement for AC voltage unless an optional thermostatically controlled heater is installed in the electronics for very cold installation sites. Also, a low temperature model of the Model HFS Gas Control Station is also available.

How can the accuracy of the HIR be verified?

It is strongly recommended that the HIR (or any other Infrared Pyrometer, for that matter) be installed and operated in conjunction with the Delta Controls Model HTP or HTX Thermocouple This provides a continuous accurate comparison with the Infrared Pyrometer.

For spot checks, the Delta Model HIP handheld pyrometer) can be used in any unobscured sight glass window or through the Model HIR’s sight port. Least desirably, accuracy can be checked with the use of an “insertion” thermocouple (same procedure as with other Infrared Temperature Transmitters).

Why should the HIR be used in conjunction with the Delta Controls Thermocouple?

The thermocouple provides a continuous accuracy standard to which the performance of the IR device may be continuously verified. The thermocouple measures heat whereby the IR is an inferential measurement (measures infrared energy which is calibrated to report temperature). Thermocouple technology measures heat directly and is the temperature measurement standard of the world.

However, thermocouples may be damaged by certain conditions that generally have no adverse effect on an IR. Such things as severe thermal shock, excessive mechanical shifting of refractory or sudden heavy quenching may damage a thermocouple’s ceramic components. None of these normally would damage an IR.

And vice versa, thermocouples are not compromised in any way by build-up of contaminants or changes in gas composition, emissivity or smoke as Infrared units may be.

Since traditional IR devices may suffer from accuracy problems (they may drift, the lens window may become occluded or the nozzle port can become filled with matter blocking the view), periodic maintenance must not only be done to correct these problems, it also must be done to detect any inaccuracy that has developed. A thermocouple, designed for use in Claus Thermal Reactors, provides the means to continuously monitor the accuracy of an IR temperature device. Also, a thermocouple, either an insertable one placed into the Infrared mounting port or the permanently mounted Delta unit fitted with the “dry-out” Thermocouple element, accurately and effectively measures the critical low temperatures required during “refractory dry-out”. However, Delta recommends that dry-out temperature monitoring be done via the use of multiple “K” thermocouples placed in the furnace prior to gas firing. This provides an inexpensive means to safeguard the new refractory at key locations and can provide some heat profile data.

Infrared devices cannot accurately measure the very low temperatures required for proper initial refractory curing.

Thermocouples (Model HTP or HTX) designed exclusively for Claus Thermal Reactor service provide the unique ability to “self-check” and warn if a failure is detected.

Using both IR and Thermocouple technology provides the utmost in accuracy, reliability, response and safety. Using both also provides better control while reducing the overall cost of maintaining the Claus Thermal Reactor and maximizing operating time between turnarounds.

What is the warranty on the Model HIR Pyrometer system?

The owner may return an HIR system for any reason of dissatisfaction, for full credit of the original purchase price within two years from the date of purchase. The purchaser must return the equipment prepaid to Delta Controls factory and be free from physical damage beyond normal wear and tear.


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