Dryer section performance monitoring · 2020. 1. 9. · TAPPI.Dryer section performance monitoring...

TIP 0404-33 ISSUED – 1986

REVISED – 1992 REVISED – 1998 REVISED – 2003 REVISED – 2007 REVISED – 2012 REVISED – 2017

2017 TAPPI

The information and data contained in this document were prepared by a technical committee of the Association. The committee and the Association assume no liability or responsibility in connection with the use of such information or data, including but not limited to any liability under patent, copyright, or trade secret laws. The user is responsible for determining that this document is the most recent edition published.

TIP Category: Automatically Periodically Reviewed (Five-year review)

TAPPI

Dryer section performance monitoring Scope Dryer section performance has a major effect on production rates, energy efficiency, and sheet quality. Regular performance monitoring can help ensure that dryer section operation is optimized and can direct maintenance and troubleshooting efforts before minor problems become major problems. Monitoring can be done by mill operations, technical, engineering or maintenance personnel; clothing and equipment suppliers; corporate technical groups; and/or independent consultants. Note that this TIP does not cover Yankee dryers. Information on the importance of techniques for measurement and equipment suppliers for several measurable drying parameters are included. Safety precautions Follow normal safety precautions when working around paper machinery. Do not allow loose clothing or equipment to contact rotating machinery. Beware of thermal and slip hazards around the dryer section, on the operating floor, and in the basement. Take precautions when working in the hot environment around the dryer section to avoid dehydration, heat exhaustion, and heat stroke. Avoid contact with hot steam piping, valves, tanks, flanges, thermocompressors, and pumps. Tag, disconnect, and lock out all dryer drives and steam systems and follow vessel-entry procedures before entering dryers.

Discussion A good knowledge of dryer section equipment, design criteria, and operating conditions is important for understanding and troubleshooting the dryer section. A list of important dryer section information is shown in Table 1, including data on the dryer arrangement, felting, steam and condensate system, siphons, steam and condensate piping, doctors, dryer bars, and hood and air systems. It is recommended that this information be compiled for each machine and kept in a file for easy access. The information will be useful for anyone who works to optimize or troubleshoot the dryer section. In addition to a completed information sheet, the following dryer section drawings should be kept on file: • Dryer Layout Drawings • Records of Pressure Vessel (dryer) Code Documentation • Steam and Condensate System P&IDs • Hood Air System P&IDs • Sketches of the Rope Runs • Fabric Tension Charts

TIP 0404-33 Dryer section performance monitoring / 2

Table 1. Dryer section information

General Information Mill Machine Number of Dryers Dryer Diameter Dryer Pressure Rating Felt roll diameter Size press/breaker location

Each Drive Group Section Dryers Felting (unorun, top/bottom, unfelted) Fabric suppliers, design, length and width Fabric permeability (top and bottom) Fabric tension (top and bottom) Gearing configuration or drive source

Steam and Condensate Sections Section Dryers Separator number and size Type (thermocompressor, cascade, individual control) Maximum operating pressure Minimum operating pressure

Siphon and Joint Information Joint size and design Siphon type (single, dual, rotary, stationary) Supplier Position in dryer Clearance Upleg diameter Horizontal pipe diameter

Dryer Bars Type (full width, profiling) Supplier Dryers

Steam Drops (header to joint) Pipe size Pipe schedule Sight glasses or drain lines installed

Dryer Section Hoods Supplier Type (open, closed) Design (tongue-in-groove, high performance) False ceiling (half-width, full-width, none) Basement enclosure

Pocket Ventilators

Supplier Type

Hood Supply and Exhaust Fan Information

Fan Manufacturer Size/Design Airflow Fan speed Static pressure Motor horsepower Heat recovery Temperature Supply air source Filter presence and condition

Individual Dryers Dryer number Felting Doctoring Dryer bars Air system component (pocket ventilator, blow box) Grooved, blind-drilled, or vacuum rolls Dryers with steam disconnected

Operating conditions A sample data sheet for dryer section operating conditions is shown in Table 2. Sheets specific for each machine should be developed and filled out to provide baseline data on critical grades to allow for effective troubleshooting and problem solving. The top portion identifies the grade being produced and the time and date that data was collected. Weight and moisture profile information is obtained from the machine gauging system. Steam pressure and differential pressure data can be obtained from steam system controllers (local controllers or DCS). Areas that indicate problems with system sizing, operation, or maintenance should receive particular attention. Such areas include controllers unable to maintain setpoint, supply valves or thermocompressors more than 80% or less than 20% open during normal operation, differential pressure or flow control signals that are out of range, steam venting to the atmosphere or to a condenser, and controllers operated in “manual.”

3 / Dryer section performance monitoring TIP 0404-33

Table 2A. Dryer section operating conditions (SI units) Mill ____________ Reel Speed mpm _____________ Machine ____________ Production tph _____________ Date ____________ Trim m _____________ Time ____________ Press Moisture % _____________ Grade ____________ Size Solids % _____________ Comments ____________ Starch Pickup kg/tonne _____________

Weight and Moisture Profiles Units Average Maximum Minimum Shape Basis Weight gsm Reel Moisture % Bone Dry Weight gsm Size Press Moisture %

Pressure and Differential Pressure Control Section Dryers Pressure Setpoint Output DP/Flow Setpoint Output No. kPa kPa %, a/m kPa/kg/hr kPa/kg/hr %, a/m Lead 1 Lead 2 Lead 3 Lead 4 1 2 3 4 5 6

Control Valve Positions Expected Actual Section Make-up Thermo Vent Make-up Thermo Vent Lead 1 X X Lead 2 X X Lead 3 X X Lead 4 X X 1 2 3 4 5 6


Table 2B. Dryer section operating conditions (customary units) Mill ____________ Reel Speed fpm _____________ Machine ____________ Production tph _____________ Date ____________ Trim in. _____________ Time ____________ Press Moisture % _____________ Grade ____________ Size Solids % _____________ Comments ____________ Starch Pickup lb/ton _____________

Weight and Moisture Profiles Units Average Maximum Minimum Shape Basis Weight lb/ream Reel Moisture % Bone Dry Weight lb/ream Size Press Moisture %

Pressure and Differential Pressure Control Section Dryers Pressure Setpoint Output DP/Flow Setpoint Output No. psig psig %, a/m psi/pph psi/pph %, a/m Lead 1 Lead 2 Lead 3 Lead 4 1 2 3 4 5 6

Control Valve Positions Expected Actual Section Make-up Thermo Vent Make-up Thermo Vent Lead 1 X X Lead 2 X X Lead 3 X X Lead 4 X X 1 2 3 4 5 6


Dryer section operation should also be observed during sheet breaks, paying particular attention to pressure and differential pressure control response, system venting, condenser operation, and sheet threading. Operator rounds Routine operator rounds are an essential part of a complete monitoring program. These rounds are particularly helpful in identifying problems before they become severe. In addition to the steam control and production information included on the sample operating conditions report, a number of areas are recommended to be included in backtender rounds, as shown in Table 3. Where possible, targets and acceptable ranges should be provided on operations checklists so that operators can recognize problems when they occur. Table 3. Suggested dry end operator rounds

• Any Valved-Off Dryers

• Draws for Each Section

• Drive Amps for Each Section

• Dryer Fabric Tensions

• Felt Guides

• Felt Stretchers

• Doctors Engaged or Disengaged

• Doctor Oscillators

• Rope Condition

• Rope Stretchers

• Lube Oil System

• Any Steam Leaks

• Flow in Condensate Sightglasses

• Levels in Separator Sightglasses

• No Condensate Being Sewered

• Supply and Exhaust Fans Turning, Coils

not Plugged, Filters Okay, Dampers Set

Correctly

• Supply Fan Temperatures

• Steam Pressures, Differential Pressures,

Controller Outputs

• Header Pressures

• Desuperheater Temperatures

• Confirm Controller and Actual Valve

Positions for One Steam Section Each Shift

• Hood and Basement Doors Closed.

Process historian data Process historian data provides information on dryer section performance for a range of basis weights and operating conditions. It is valuable for assessing the operation of the dryer drainage system and identifying operating conditions that lead to excessive energy use or poor dryer performance. The suggested process historian data collection method is shown in Table 4. The process variables that should be monitored will depend on the configuration of the dryer drainage system and the field instrumentation available. The process historian data should be collected in a spreadsheet where the data can be filtered, plotted, and analyzed. The data should be filtered by the sheet break signal. The differential pressure or blow-through steam valves that discharge to the condenser, or atmosphere, are important in assessing energy efficiency. These valves should remain closed under all operating conditions. The system is wasting steam if these valves are open. If thermocompressors are used, they should be in control within a 20% to 80% range for all operating conditions with the sheet on the dryers. The differential pressures should be maintained at proper levels over the entire pressure and speed range. TIP 0404-31 Recommended Dryer Differential Pressures should be used to determine if differential pressures are at proper levels.


Table 4. Process historian data collection method Data Acquisition

Time Stamp Include

Format Excel spreadsheet

Frequency One hour

Duration Three months

Data Values Snapshot not averages

Production Data

Grade Number or Name

Basis Weight

Reel

Before Size Press (if applicable)

Before Coater (if applicable)

Reel Speed

Sheet Width Reel

Production Rate Ton / hour

Moistures

Reel

Before Size Press (if applicable)

Before Coater (if applicable)

Sheet Break Status Break / Run

Steam Supply

Steam Flows For all steam supply headers

Steam Header Pressure For all steam supply headers

Steam Header Temperature For all steam supply headers

For Each Dryer Pressure Group

Pressure Process value

Pressure Controller Output

Make-up Valve Position

Differential Pressure Process value

Blowthrough Flow (if present) Process value

Differential Pressure Controller Output

Blowthrough Flow Controller (if present) Output

Differential / Blowthrough Vent Valve Position

Thermocompressor (if present) Position

Vacuum Condenser (if present)

Vacuum level Process value

Water Valve To Heat Exchanger Position

Cooling Water Outlet Temperature (if present) Process value

Cooling Water Inlet Temperature (if present) Process value

Hood & Pocket Ventilation

Pocket Ventilation Temperature Process value for each fan system.

Exhaust Fan Speed Or Damper Position (if controlled) Process value for each fan system.

PV Fan Speed Or Damper Position (if controlled) Process value for each fan system.

Hood Exhaust Humidity (if measured) Process value for each humidity sensor.


Calculations can be built into the spreadsheet of the process historian data to assess dryer energy efficiency. The water evaporation can be calculated using the basis weight, speed, sheet width, and sheet moistures. It is necessary to input a value for the press moisture to complete this calculation. TIP 0404-07 “Paper Machine Drying Rate” describes the method for calculating the water evaporated. The steam consumption per pound of water evaporated can be calculated for each operating condition. The target steam consumption for the dryer cylinders is 1.2 to 1.4 kg of steam / kg of water evaporated and 0.15 to 0.18 kg of steam / kg of water evaporated for the hood supply and pocket ventilation systems; less if heat recovery is present. If a vacuum condenser is present, monitoring the vacuum level and water valve position can provide insight into condenser operation and energy consumption. The water valve should be at a low percent open (10% to 25% typical) during normal operation. A water valve that operates at a higher opening would indicate a potential problem. Energy loss, a dirty heat exchanger, air leakage, or an improper control set-point are possible causes. The vacuum level should be maintained at the control set-point for all operating conditions. An operating condition where the vacuum set-point cannot be maintained could indicate a high energy loss from the steam system. State-of-the-art condenser monitoring systems include measurement of flow, inlet temperature, and outlet temperature for the cooling water, which allows calculation of heat load to the condenser and dryer section losses. The pressure control valves for each pressure control sections should be in a good control range of 20% to 80% open for all operating conditions. Valves that are fully open or closed indicate poor control. Performance measurement In many ways, it is easier to measure and troubleshoot dryer section performance than other portions of the paper machine. Measurements and good performance indicators are well defined and can be obtained by mill or corporate personnel, equipment suppliers, and fabric suppliers. Dryer section performance indicators and second quartile performance levels for fine paper, linerboard, corrugating medium, and bleached board grades are shown in Table 5 for reference as benchmark indictors. Moisture content An accurate indication of moisture content of the web entering and exiting the dryer section is critical to dryer section analysis since the primary function of the dryer section is to evaporate water from the sheet. A history of press moisture levels is critical for optimizing both the press and the dryer sections. Press moisture samples should be taken as the machine goes down for each maintenance outage. TAPPI TIP 0404-01 “Determination of water removal by wet presses” provides a procedure to determine water removal. As many cross-machine samples as is convenient should be taken to provide profile information. Note that a 1% error in press moisture yields a 4%–5% error in estimating drying load. Sampling errors, rewetting of the sheet in getting samples, or edge effects can cause grab samples to be inaccurate. Recent advances in measuring devices have allowed use of microwave or near-infrared gauge to measure moisture levels out of the presses and, in some cases, throughout the dryer section. Care should be taken in the interpretation of results, as some error may be inherent in the measurements, particularly on lightweight grades. It may not be possible to take these measurements in all sections due to limited access. On multi-ply grades there is the danger of not penetrating well through the measured top layer into the middle plies. Dryer section steam consumption and press section water balances can also be used to calculate sheet moisture out of the press section. A uniform reel moisture profile is critical for uniform sheet properties. The moisture target depends on end-use requirements, but in all cases uniformity is needed. Moisture profile problems can result in operational and quality problems including reel building, “soft” rolls, “corrugated” rolls, calender blackening, converting difficulties, and rejected paper. Many machines over-dry the sheet to compensate for moisture profile problems. This practice results in higher steam consumption and reduced drying capacity. TAPPI TIP 0404-57 “Troubleshooting cross-machine direction moisture profile problems” discusses CD profiles in more detail.


Table 5A. Dryer section second quartile performance levels (SI units)

Index Units Fine Paper Main

Fine Paper After

Liner-board

Corrugating Medium

Bleach Board

Moisture in % 60 38 54 57 60 Exiting Moisture CD Range

% range @ % avg

0.2 @ 2.0

1.0 @ 5.0 2.0 @ 7.0

2.0 @ 7.0 1.0 @ 5.0

TAPPI Drying Rate

kg water/hr/m2

@ kPa

27 @ 515

32 @ 450 28 @ 965

24 @ 965 25 @ 825

Steam-to-Surface Temp. Difference

°C 22–28 19–25 22–28 22–28 19–25

CD Temperature

°C 2.8 2.8 2.8 2.8 2.85

Condensing Load

kg cond/hr/m2

29 17 36 32 32

Dryers in Prime Zone

% of total 75 80 75 75 70

Average Pocket Humidity

kg water/kg dry air

0.20 0.20 0.20 0.20 0.20

CD Humidity Range

kg water/kg dry air

0.05 0.05 0.05 0.05 0.05

Peak Pocket Humidity

kg water/kg dry air

0.25 0.25 0.30 0.30 0.30

Average Hood Exhaust Humidity

kg water/kg dry air

0.13 0.10 0.13 0.13 0.13

Peak Exhaust Humidity

kg water/kg dry air

0.14 0.11 0.14 0.14 0.14

Hood Balance % supply to exhaust air

70 60 70 70 70

PV Temperature

°C 82 82 93 93 93

Fabric Tension kN/m 1.75 1.75 2.1 2.1 2.1 Energy Consumption

kg steam/kg water

1.3 1.0 1.3 1.3 1.3

Streaky CD moisture profiles most often originate at the wet end of the machine and are caused by and coupled to bone-dry weight variations, non-uniform press nip loads, and/or poor press felt condition. Typically, gentle “frown” or “smile” profiles originate in the dryer section or in the press section from misadjustments in press roll crowns. Proper press crowns, close-clearance siphons, full-width dryer bars, proper pocket ventilation, and clean fabrics with uniform tension help to ensure uniform profiles through the dryer section. Steam showers, remoisturizing showers, and profiling infrared dryers can be used to correct non-uniform moisture profiles, although sheets using these corrections are more likely to have non-uniform sheet properties than sheets that have uniform profiles throughout the process. Profiling infrared dryers are expensive to operate and are primarily used when non-contact drying is required such as for early coating drying. Infrared is sometimes used for incremental drying, but is generally not recommended


Table 5B. Dryer section second quartile performance levels (customary units) Index Units Fine

Paper Main

Fine Paper After

Liner-board

Corruga-ting

Medium

Bleach Board

Moisture in % 60 38 54 57 60 Exiting Moisture CD Range

% range @ % avg

0.2 @ 2.0 1.0 @ 5.0

2.0 @ 7.0 2.0 @ 7.0 1.0 @ 5.0

TAPPI Drying Rate

lb water/hr/ft2 @ psig

5.5 @ 75 6.5 @ 65 5.7 @ 140 5.0 @ 140

5.2 @ 120

Steam-to-Surface Temp.Difference

deg F 40-50 35-45 40-50 40-50 35-45

CD Temperature Range

deg F 5 5 5 5 5

Condensing Load

lb cond/hr/ft2 6.0 3.5 7.4 6.5 6.5

Dryers in Prime Zone

% of total 75 80 75 75 70

Average Pocket Humidity

lb water/lb dry air

0.20 0.20 0.20 0.20 0.20

CD Humidity Range

lb water/lb dry air

0.05 0.05 0.05 0.05 0.05

Peak Pocket Humidity

lb water/lb dry air

0.25 0.25 0.30 0.30 0.30

Average Hood Exhaust Humidity

grains/lb dry air

900 700 900 900 900

Peak Exhaust Humidity

grains/lb dry air

1,000 800 1,000 1,000 1,000

Hood Balance % supply to exhaust air

70 60 70 70 70

PV Temperature deg F 180 180 200 200 200 Fabric Tension pli 10 10 12 12 12 Energy Consumption

lb steam/lb water

1.3 1.0 1.3 1.3 1.3

Controlling moisture content into the size press is critical for uniform starch pickup and main section drying capacity. Wetter areas of the sheet tend to pick up more starch, so it is important to have a uniform profile, particularly for puddle-type size presses. Over-drying the sheet to below 2% average moisture significantly decreases main section drying capacity because a disproportionately large number of dryers are required to remove the last portion of water from the sheet. It can be difficult to measure moisture contents below 2% accurately. In cases of suspected loss of main section drying capacity, every attempt should be made to verify that moisture level is accurate. Significant capacity loss can occur in the case of severe over-drying and inaccurate moisture indication. While this is a difficult application for moisture gauges, sheet temperature has been used successfully to control over-drying. Moisture content of the sheet exiting the size press is a function of the sheet moisture and temperature entering the size press, as well as starch solids, viscosity, and pickup. Increasing starch solids (for a given amount of starch solids pick-up) reduces the amount of water to be evaporated after the size press. Metering-type size presses typically have much less water to evaporate and have higher drying rates than puddle size presses (for equal solids and pick-up). Note that typically, due to lower solids, a puddle-type size press leaves more water in the sheet, thus


requiring more water to be evaporated. This, in turn, requires higher steam pressures (and therefore higher drying rates) for an equal number of dryers. Sheet moisture content at the reel, into a size press or coater, and in some cases into the dryer section can be monitored by on-line total mass sensors and infrared and microwave units. Portable moisture meters include infrared and microwave sensors. Drying rates TAPPI drying rate provides a good indication of overall dryer section performance. The rate is obtained by dividing the mass of water evaporated/hr by total surface area of effective dryers. TAPPI TIP 0404-07 “Paper Machine Drying Rate” shows the calculations required. Programs are available to simplify the calculations. Note that dryers that do not contact the sheet (such as bottom unorun dryers) and dryers that are shut off are not included when calculating drying area. TAPPI has compiled drying rates for various grades in TAPPI TIP 0404-07 “Paper Machine Drying Rate.” Drying rate is plotted versus average steam temperature for the dryer sections. Note that temperatures used are saturated temperatures at operating steam pressures. Superheat is not included in the calculations. Excessive superheat is not normally a factor in loss of drying unless the steam temperature into the dryers is significantly higher, for example, 55 °C (100°F), above saturation temperature. Some mills have noted drying loss when superheat is at this level. Equipment degradation is known to occur at excessive superheat. TAPPI drying rate curves should be used with care. The plots show data points from a number of machines making similar grades, with average and 2-sigma lines drawn on the curves. A machine’s position on the curve provides a relative indication of dryer section performance and can provide a first step towards more detailed analysis of capabilities and limitations of the machine. A number of factors determine the efficiency of a dryer section. Several of these are listed in Table 6. Table 6. Factors affecting drying rates Factor Effect Entering Moisture Content A wet sheet into the dryers can result in high drying rates since this leaves

more “easy water” for the dryers. Changing entering moisture by 1 percentage point affects the amount of water to be evaporated in the dryer section by 3-5%.

Sheet Furnish Bleached grades dry easier than unbleached. Recycled fiber dries easier than virgin.

Sheet Smoothness A smoother sheet has better sheet-to-dryer contact and better drying rates. This is why a smoothing press or a breaker stack increases machine speeds.

Steam Pressure Higher steam pressures result in higher drying rates. A 5.6 °C (10°F) increase in average steam temperature increases the drying rate by 1.0 kg/hr/m2 (0.2 lb/hr/ft2).

Dryer Fabric Tension Higher fabric tension increases sheet-to-dryer contact and increases drying rates. The increase is most pronounced on wet end dryers, particularly on lighter weight grades.

Dryer Fabric Wrap Dryer section arrangements that have high felt wrap area ryer have higher drying rates than those that have low felt wrap area, both for dryers in a dryer group and for dryers next to open transfers.

Pocket Ventilation High pocket humidities restrict mass transfer from the sheet and restrict drying rates.

Condensate Evacuation A thick, rimming condensate layer insulates the inside dryer surface from the steam inside the dryer and reduces drying rates.

Dryer Bars Dryer bars improve heat transfer between the steam and the dryer shell and increase drying rates.

Exiting Moisture Content Over-drying reduces drying rates. Size Press Design Metering size presses have 10–20% higher after-size drying rates than


conventional size presses at equal starch solids and pickup. Further, metering size presses typically have much higher starch solids and therefore much lower drying requirements.

Dryer Section Layout Single-tier drying sections have higher drying rates than two-tier dryers. Increased sheet wrap and longer areas for evaporation to occur and low ambient humidity levels all contribute to higher rates.

Condensing loads Dryer section condensing loads provide an indication of drying efficiency. Condensing rates are measured by rate-of-rise tests on separator tanks with the procedure described in TAPPI TIP 0404-18. Some machines have flowmeters installed on condensate return lines to provide continuous monitoring. Relative condensing loads can be seen by monitoring the level control valve position from a condensate separator. A level control valve opening to maintain level during steady-state conditions indicates that condensing rates have increased. High condensing loads typically indicate good heat transfer to the sheet. Establishing baseline condensing rates for key grades can provide valuable information when troubleshooting problem conditions. Accurate condensing rate information is also essential for proper steam and condensate system sizing. Condensing loads typically range from 17 kg/hr/m2 (3.5 lb/hr/ft2) of dryer surface for fine paper after-size sections to 39 kg/hr/m2 (8.0 lb/hr/ft2) for linerboard. The total steam condensed in the dryers should be approximately 1.2-1.4 kg steam/kg water evaporated (1.2-1.4 lb steam/lb water evaporated). Condensing rates are highest in the prime drying zone and are significantly lower in the falling-rate drying zone at the dry end of the machine. Figure 1 shows calculated condensing loads and sheet moisture through the main section of a fine paper machine. Steam is disconnected from dryers 1, 3, and 5. Condensing load increases step-wise with higher steam pressures at dryers 7 and 15. In this example, dryers 1–6 are in the warm-up zone, dryers 7–27 are in the “constant-rate” drying zone, and dryers 28–31 are in the falling rate zone.

Fig. 1. Condensing rate calculations Condensing loads can also be used to establish differential pressure or flow control set-points. Differential pressure can be adjusted and condensing loads monitored to determine the maximum condensing load for particular operating conditions.


Surface temperatures Dryer surface temperatures provide a good indication of condensate removal and heat transfer efficiency. Surface temperature depends on a number of factors with steam pressure being the most important. Differences between steam and dryer surface temperatures should be in the range of 15–40°C (30–75°F) in well-performing dryer sections. Surface temperatures should be analyzed in conjunction with condensing loads to fully evaluate the drying process. High condensing loads result in thicker condensate layers within the dryers. In dryers lacking dryer bars, thicker rimming condensate layers can insulate the dryers and reduce surface temperatures. Poor sheet-to-dryer contact, on the other hand, can also reduce heat transfer and condensing loads resulting in high surface temperatures. Table 7 summarizes possible combinations of condensing load and surface temperatures. Figure 2 shows a typical plot of dryer surface temperatures versus dryer number (1). Surface temperature at the wet end of the machine should be graduated (on most grades) to prevent picking from the sheet. Steam-to-surface temperature differences will usually be higher at the wet end than on the rest of the machine.

Fig. 2. Typical plot of dryer surface temperatures Temperatures through the constant-rate drying zone (also called the prime drying zone) should be consistent from dryer to dryer. Inconsistent temperatures may be indication of marginal dryer drainage. Top-to-bottom temperature differences can indicate dryer fabric tension problems or significant wire side/felt side sheet property differences. Top-to-bottom temperature differences have been noted on dryer sections on multi-ply board grades, dryer sections without bottom felts, dryer sections with different top and bottom felt tensions, and dryer sections with unorun dryers.


Dryer surface temperatures tend to increase at the dry end of the machine as the sheet enters the falling-rate drying zone. Table 7. Dryer surface temperatures and condensing loads Condensing Load

Steam-to-Surface Temp. Difference

Analysis

Low High Very poor condensate removal is restricting drying rates.

High High High evaporation rates are making the dryers work hard. Dryer bars or siphon improvements will help drying rates.

Low Low Poor sheet-to-dryer contact is indicated. Extreme examples include bottom unorun dryers and unfelted dryers. Increasing fabric tension or improving sheet smoothness will help drying rates. This condition also exists in the dry-end falling-rate drying zone.

High Medium Optimum conditions. The dryer section is working hard and evacuation is not restricting drying.

Surface temperatures should be measured prior to each shutdown to determine which dryers have condensate removal problems and should be inspected and repaired on the outage. Accurate temperature measurement can be difficult. Contact pyrometers and infrared sensors are often used. Thermocouples mounted in Teflon blocks or roller-types supplied by Swema are probably the most commonly used. A contact pyrometer developed by Electronic Development Laboratories is also widely used. This sensor consists of a stainless steel strip with thermocouples mounted on the back of the strip. Temperature readings are shown on a battery-operated digital display. These thermocouple mountings are designed to minimize frictional effects on the reading, but rough dryer surfaces, especially those caused by dryer picking, can result in inaccurate measurements. Temperature sensors can be mounted on aluminum conduit or a fiberglass pole to permit dryer temperature measurements inside the sheet run. Often it is necessary to make a custom unit by making the mounting bracket and pole assembly for any of the sensors available. Care must be taken to have a secure design that will not come apart inside the dryer pocket. . TAPPI TIP 0404-39, “Dryer Surface Temperature Measurement,” provides a thorough discussion of dryer surface temperature measurement. Many mills use infrared sensors to indicate the temperature of dryer heads. Dryer head temperature may not change between a hot dryer and one that is partially water logged. Head temperatures are a good indication of problems only when a dryer is nearly completely filled with water. Infrared sensors are affected by light emitted from incandescent bulbs, surface emissivity, and the viewing angle. Accordingly, they should be used for relative readings rather than absolute temperatures. Surface temperature profiles Cross-machine surface temperature measurements provide a good indication of siphon performance and possible effects on sheet moisture profiles. CD measurements can be taken on the tending and drive sides with hand-held temperature probes. One-foot increments are generally adequate, although closer spacing can be taken if necessary. These hand-held measurements are limited by safety and the length of mounting pole. True temperature profile measurements can also be performed across the full width of the pockets (1). Figure 3 shows a uniform cross-machine surface temperature profile of an average of six dryers with good drainage.


Fig. 3. Cross-machine dryer surface temperature profile of good dryer

Fig. 4. Cross-machine dryer surface temperature profile of poorly draining dryer


In dryers lacking dryer bars and running at “rimming” speeds, condensate layer thickness has a significant effect on surface temperature profiles. The classic profile of a poorly evacuated dryer is a “smile” with the edges hotter than the center. This results in a “frown” sheet moisture profile with a wet center and dry edges. An example is shown in Figure 4. Turbulence in the condensate layer near the head inside the dryer breaks up the otherwise stagnant layer. Poorly draining dryers may also be hotter near the siphon than further away. Non-uniform dryer fabric tension or misaligned dryers can also result in poor surface temperature profiles. Internal grooves at dryer edges or dryer bars that do not extend the full sheet width can result in wet edges. Well-drained dryers should have less than 2.6°C (5°F) CD temperature variation. Sheet temperatures Sheet temperature measurements provide a quick and effective indication of dryer section performance. The measurements show the effects of wet-end and warm-up dryers, cold dryers, and any over-drying ahead of the size press or reel. Reliable sheet temperature measurements can be taken with an infrared sensor at a 0.92–0.95 emissivity setting. Measurements should be taken on the side of the sheet leaving the dryer, 0.6–1.0 m (2–3 feet) from the edge of the sheet, at the midpoint between top and bottom dryers. On heavyweight sheets, temperatures can be measured on both sides of the sheet. Care should be taken that humidity from the dryer section does not fog the lens of the infrared gun. A plot of temperature versus dryer number for a top-performing machine is shown in Figure 5 (2).

Fig. 5. Typical Plot of Sheet Temperatures Wet end dryers bring the sheet up to evaporation temperature. Sheet temperature rise should be as quick as possible without causing picking or quality problems. Top-performing machines increase sheet temperatures approximately 8–17°C (15–30°F) per dryer at the wet end. Note that high initial dryer surface temperatures do not necessarily lead to high sheet temperatures. Good


ventilation, low thermal contact, high sheet moisture, and low fabric wrap angles tend to decrease sheet temperatures. The best method to optimize the warm-up zone is to start at low steam pressures and graduate upward towards the constant-rate drying zone. Sheet temperatures following the warm-up section normally remain constant through the prime drying zone. Any dips in temperature normally indicate cold dryers (or section splits). Temperature level through the prime drying zone is a function of steam pressure (higher surface temperatures normally result in higher sheet temperatures) and pocket humidity (high humidities restrict mass transfer and require higher sheet temperatures for evaporation to occur). On board and some heavyweight grades, sheet temperatures gradually increase throughout the dryer section and there is no constant rate drying zone evident in sheet temperatures. The falling rate drying zone typically occurs when sheet moisture content reaches approximately 10%. The water left in the sheet at this point is more difficult to remove from the fibers, so higher sheet temperatures are needed for evaporation. This point is normally easy to identify on a plot of sheet temperatures, because the sheet temperatures increase rapidly after the prime drying zone. Sheet temperatures at the end of a section can give a relative indication of exiting moisture content, although temperature that can be achieved is also a function of the dryer surface temperatures and pocket humidities. Once essentially all water has been evaporated from the sheet, sheet temperature will level out until the end of the section. Such extreme over-drying wastes steam and limits drying capacity. An example is shown in Figure 6.

Fig. 6. Sheet temperature plot with extreme over-drying into the size press Percent of dryers in the prime drying zone provides a good indicator of drying strategy and correlates well with drying rates. Prime dryers are determined by taking the total number of effective dryers (excluding bottom unorun cans) and subtracting out the number of dryers in the warm-up and falling-rate sections. The percentage is calculated by dividing this number by total effective dryers. A plot of drying rate (corrected for steam pressure) versus the percent of dryers in the prime drying zone for fine paper machine main sections is shown in Figure 7 (2). Top-performing machines have 70–80% of the dryers in the prime zone.


Fig. 7. Percentage of prime dryers vs. drying rates Infrared sensors are the most common way to measure sheet temperatures. These sensors provide more accurate readings on the sheet than on metallic dryer cylinders. They are affected by emitted light, radiant energy from


nearby steam lines, sheet thickness, and free steam around the sheet. Suppliers of portable infrared sensors include Fluke, LumaSense, Omega, Wahl, and Testo. Use of contact pyrometers such as a Swema unit to measure sheet temperature requires practice and a steady hand and is generally unnecessary because of the effectiveness of infrared gauges. Contact sensors should not be used on wet, lightweight sheets. Cross-machine temperature profiles Infrared thermography provides a good tool for identifying the source of moisture streaks and poor profiles. Scanning systems can be used at the reel and at other areas where the full sheet can be observed. Areas with higher moisture show up as cool areas in dryer section thermography profiles. Cool areas in the press or former may be drier since the sheet can be cooled by vacuum sources. Thermography does a good job shooting profiles of the sheet and fabrics, but varying emissivity prevents accurate measurement of dryer surface temperature profiles. FLIR Systems, Ircon, Land Infrared, and Mikron supply thermography systems. Thermography measurements require interpretation. Thermography displays differences, and there can be different causes for these differences. For instance, is a wet sheet causing a cool indication on a hot dryer or is a cool dryer causing the effect on the sheet? Pocket humidities Dryer pocket humidities provide another indication of dryer section performance. Humidity levels are a function of pocket ventilation performance, dryer fabric permeability, evaporation rate, and machine geometry. High humidities restrict mass transfer of water vapor from the sheet and limit drying and production rates. TAPPI provides a guideline that absolute humidities should be less than 0.20 kg water vapor/kg dry air (0.20 lb water vapor/lb dry air), but this is not an absolute guideline. Lower humidities allow better mass transfer while higher humidities can restrict mass transfer. High capacity board machines operate effectively with humidities of 0.25-0.30 kg water/kg dry air. Machines with good pocket ventilation have low and uniform pocket humidities, like those plotted in Figure 8 (2). Poorly ventilated machines have humidity plots more like those shown in Figure 9 (2) with higher humidities over bottom dryers than under top dryers and increasing humidities through each fabric section. Potential drying increase available from reducing pocket humidities is inversely proportional to basis weight. The lighter the sheet the greater the potential for increasing drying capacity by reducing pocket humidity. Further, pocket humidity tends to be a more impactful variable on machines with low dryer steam pressures versus those with high dryer steam pressures. Wet and dry bulb thermometers or solid-state psychrometric measurement devices can be used for measuring pocket humidity. EDL, Vaisala, and others market psychrometers. Often commercial sensors or test units need to be modified to make measurements in the paper machine dryer section. Humidity profile It is critical that humidities be uniform in the cross-machine direction. A typical profile of a poorly ventilated pocket has a “frown” shape with higher humidities in the center than at the edges of the pocket as shown in Figure 10 (2). This humidity profile contributes to a “frown” sheet moisture profile with a wet center and dry edges. It is highly unlikely that wet edges and a dry center come from a poor pocket humidity profile due to the nature of air flow within and around a machine. Humidities can be measured at various points across the width of the pocket to provide an indication of profiles. Traversing probe sensors can also be used to measure CD humidity profiles (1). Pocket air velocities Airflows into or out of a dryer pocket can be measured with a small anemometer held near the edge of the dryer pocket. The air velocity and direction can affect sheet flutter and ventilation efficiency. Ideally, each pocket would be perfectly balanced with air pumped into the pocket by the pocket ventilation system with the air exiting the pocket through the fabric. In practice, this seldom happens. Most suppliers recommend a slight outflow of air from the pockets to ensure proper ventilation. Sheet flutter can result if this outflow is too high. An inflow of air


from the edges is an indication of low supply air volumes. This can result in sheet folds and wrinkles. Davis, , Testo, TSI, and others supply anemometers for measuring pocket airflows.

Fig. 8. Typical plot of dryer pocket humidities


Fig. 9. Pocket humidities with poor pocket ventilation

Fig. 10. Cross-machine pocket humidity profile with poor ventilation


Hood exhaust humidities Hood exhaust humidities provide an indication of exhaust fan performance. There must be enough exhaust to isolate the dryer air systems from the building ventilation systems. Too little exhaust air results in sweating and condensation on hood panels, humid air spilling into the machine room, equipment deterioration, and hot, uncomfortable conditions. Too much exhaust air wastes energy and can cause sheet flutter. Exhaust humidities also affect pocket humidity levels and profiles (especially on the edges) on machines with poor pocket ventilation. Exhaust air humidity is measured with wet bulb/dry bulb thermometers and calculated from psychometric charts or tables, or can be measured with sensors like those used for pocket humidity. Conventional units for exhaust humidities are grains water vapor/lb dry air. There are 7,000 grains in a pound of water vapor so an absolute humidity of 0.10 kg water vapor/kg dry air (0.10 lb water/lb dry air) equals 700 grains/lb da. Some machines utilize permanent hood exhaust humidity sensors. Hood exhaust airflow requirements are a function of evaporation rates and hood design. Table 8 shows recommended average and peak exhaust humidities for various hood designs. Open hoods have no front panels, rear sliding panels, or basement enclosure, while closed hoods have all of the above. Table 8A. Hood exhaust humidity guidelines (SI units) Type

Design

Average humidity kg water/kg d. a.

Peak humidity kg water/kg d. a.

Open Uninsulated 0.050 0.064 Open Insulated 0.064 0.079 Closed Tongue-in-groove 0.13 0.14 Closed High Performance 0.17 0.19 Table 8B. Hood exhaust humidity guidelines (customary units) Type

Design

Average humidity grains/lb da

Peak humidity grains/lb da

Open Uninsulated 350 450 Open Insulated 450 550 Closed Tongue-in-groove 900 1,000 Closed High Performance 1,200 1,300 Air flows Checking dryer section supply and exhaust air flows confirms proper system performance and helps diagnose problems that can affect drying capacity, sheet runnability, and machine efficiency. High pocket humidities and sweating inside the dryer hood can signal that the air system is out of balance and that fan flow measurements are warranted. Airflows are measured by an anemometer through supply coils or duct outlets or with a pitot tube inside ducts. Davis, Dwyer, Testo, Omega, and others supply pitot tubes and vane anemometers. Davis, Dwyer, Testo, and TSI provide thermal anemometers. If hood airflows are not close to design volumes, there are a number of additional measurements that should be taken to determine the source of problems, including: Fan amp readings. Amp readings can be measured by mill electricians at the motor control center. Airflow is proportional to brake horsepower under normal conditions. Low amp readings should correspond to low airflows.


High amp readings and low flow can indicate mechanical problems with the fan or plugged filters, steam coils, or ductwork. Inlet static pressure before the fan. Static pressures before the fan can be measured by a pitot tube and manometer. High inlet static pressures (greater than 0.4 kPa (1.5 in. water gauge) in most applications without heat recovery) can indicate plugged filters, steam coils, or ductwork, or closed dampers before the fan. The airflow is reduced when static pressure that the fan must overcome is increased. Outlet static after the fan. Fan outlet static pressure can also be measured by a pitot tube and manometer. Pocket ventilation systems are typically designed for 1.5 to 4.5 kPa (6 in. to 18 in. water gauge). High outlet static can mean that the outlet ductwork, blow boxes, or PV nozzles are plugged, or that an outlet damper is closed. Low outlet static pressures can indicate a clearance problem with fan wheel or holes in ductwork after the fan. Temperature. Temperatures after fans can be measured with thermometers. Low supply fan temperatures can indicate steam coil drainage problems or leaks in the fan inlet casing or ductwork. Excessively high supply fan temperatures can result in high pocket humidities when the air is heated before the fan. Fans are designed to pull a given volume of air. Since air expands when heated, the actual mass of air distributed to the hood is lower at high temperature than at room temperature conditions. For example, an 85,000 m3/hr (50,000 cfm) fan delivers 15% more air mass at 82°C and 1.04 m3/kg dry air (180°F and 16.64 cu ft/lb dry air specific volume) than at 138°C and 1.20 m3/kg dry air (280°F and 19.23 cu ft/lb dry air). Increasing ventilation air temperatures over 93°C (200°F) usually does not produce an appreciable increase in ventilation capacity. Fan speed. Fan speed can be measured by a mechanical (when drive guards allow) or strobe tachometer. Fan flow is approximately proportional to rotational speed. Low rpm can indicate loose or missing belts or that the wrong drive sheaves are installed. Improper electrical connections can result in the fan turning backwards and greatly reduced airflow. Hood balance Hood balance is defined as the ratio of heated supply air to hood exhaust. The ratio is calculated using mass flow or scfm (standard cubic feet per minute–equivalent air flow at 21°C (70°F), no humidity, and a specific volume of 0.83 m3/kg dry air (13.33 cu ft/lb dry air) instead of acfm (actual cubic feet per minute at actual temperature and pressure conditions). Typical design balances are 35%–40% for an open hood and 65%–75% for a closed hood. The rest of the air exhausted from the hood infiltrates into the dryer section from the machine room. Too high of a hood balance results in spill from the hood into the machine room. A low balance results in sweating, runnability problems, and poor CD profiles. Conditions around the machine may become uncomfortable and troubleshooting, broke cleaning, and operation may become difficult. Zero level The hood zero level (also called the null point) is the elevation where the hood becomes pressurized and heat and moisture tend to spill into the machine room. Dryer section hoods operate with a chimney effect with cool air from the basement being heated and picking up humidity as it rises through the dryer section. Air expands as it heats, so pressure relative to the machine room aisles increases at higher elevations. Below the zero level (in the basement and lower levels above the operating floor), air infiltrates into the hood from the machine room through doors or other openings. Above the zero level, hot air spills to the machine room from the hood. The zero level is generally measured in feet above the operating floor at various machine-direction positions along the tending-side and drive-side of the hood. It can be detected at hood openings by observing where a vane anemometer changes directions, feeling with your hand or face where the air begins to blow out (provided air temperatures or pressures are not high enough to cause safety issues), using a smoke source to see the stagnation level, or physically measuring static pressures or temperatures. Some machines have permanent zero-level sensors tied into a DCS computer.


Zero-level affects comfort levels in the machine room and sheet runnability. The recommended level is at the top of the hood doors for a closed hood and above the hood side panels (to prevent spill) with an open hood. Level is affected by hood balance (ratio of supply to exhaust air) and hood closure. Opening hood or basement enclosure doors will lower zero-level and pressurize the hood. High pocket flows can mask zero levels by making them appear artificially low. Fabric tension Dryer fabric tension is used to hold the sheet in tight contact with the dryers to increase the rate of heat transfer. Increasing tension will increase drying rates, until an asymptote is reached where further tension provides a much smaller gain. Increased fabric tension can also reduce CD shrinkage and cockle and prevent slippage of felt-driven dryers. Excessive tension can affect dryer fabric dimensional stability by causing weave distortion and fabric narrowing, as well as contributing to premature failure of felt roll bearings and/or journals. Seam straightness can be used as an indication of uneven tension and closed fabrics. Recommended tension on older machines is typically 1.4–1.7g kN/m (8–10 pli) while modern machines are designed for tensions over 3.5 kN/m (20 pli). Fabric tensions are further discussed in TAPPI TIP 0404-04, “Recommended Tensions in Dryer Fabrics.” Tension is provided by stretch rolls and either hanging weights (older machines) or pneumatic cylinders (modern machines). Some have air motors or electric motors to provide tension. Machinery builders provide curves to convert cylinder pressure (kPa or psi) to tension (kN/m or pli). Mechanical advantage needs to be calculated when using hanging weight systems. It is an important safety item that all stretch rolls are operating in proper ranges and that fabric stretch rolls are not tied down. Bypassing the tensioning system can result in damage to the machine. A Honigmann Tensiometer can be placed directly on the dryer fabric to obtain a reading proportional to dryer fabric tension. Cross-machine fabric tension profiles can be checked with the tensiometer. Feltest has two types of tensiometers – one static and one on-the-run. Care must be taken in interpreting the results from the tension device readings as they are somewhat subjective in nature. Fabric permeability Dryer fabric permeability plays an important role in pocket ventilation and runnability. The proper permeability is a compromise between runnability and ventilation. In general, fabrics should be as open as possible to allow air to flow into and out of the dryer pocket, but to remain in balance to avoid creating excessive sheet flutter. Design permeabilities are typically 1,370–1,650 m3/hr/m2 (75–90 cfm) in unorun sections and 2,740 m3/hr/m2 (150 cfm) (on high-speed fine paper machines) to 12,800 m3/hr/m2 (700 cfm) (on low-speed board grades) in conventional double-felted sections. Actual permeability can be measured during machine outages by a permeability tester that will report the results in m3/hr/m2 at 125 Pa (cfm/ft2 at 0.5-in. water gauge) pressure. Valmet and TexTest supply these testers. Advanced Testing Instruments, Frazier, and TexTest provide bench-type permeability testers that are used in laboratories by many fabric suppliers. Permeability tests can indicate fabric filling, the effects of cleaning, and CD variations that can affect moisture profiles. Energy consumption The dryer section is the highest thermal energy consumer on the paper machine, so optimizing drying energy efficiency can help to cut operating costs. Dividing total dryer steam consumption by water evaporated provides a good energy indicator (except for PV air heating). Top machines utilize approximately 1.2-1.4 kg steam/kg water evaporated (1.2-1.4 lb steam/lb water evaporated). One of the reasons for variation is utilization of flash steam on high-pressure machines. If flash steam can be used in low-pressure dryers, specific steam consumption in the dryers will be lower. If flash steam is utilized (instead of high pressure steam) for pre-heating process air, the specific dryer steam consumption will be higher. In either case, the total steam consumption (including air systems) may be equal.


Table 9 shows a breakdown of where energy is consumed in the dryer section (3) on a good-performing machine. Sheet heating is a function of entering sheet temperature and any over-drying at the end of the dryer section. Press section steam boxes that heat the sheet and improve water removal ahead of the dryer section can significantly reduce dryer section energy consumption (but sometimes have negative effect on total specific energy use even though they may provide an incremental production increase). The energy required for evaporating water from the sheet is essentially constant and cannot be easily changed. Air heating requirements are a function of PV air volume and temperature. Temperatures of 82–93°C (180–200°F) are recommended for optimum performance. Some paper machines producing containerboard grades have reduced PV supply air temperatures as low as 49 to 66oC (120 to 150oF) to reduce steam consumption without adversely affecting production rates. Dryer hood design and air movement can restrict potential to lower PV supply air temperature. The biggest potential energy waste in the dryer section is venting steam (including flash steam, that is, steam generated by self-evaporation when hot condensate is discharged into a lower-pressure collection tank) to the atmosphere or to a heat exchanger. Steam and condensate systems should be designed so that no venting occurs during normal operation. Sheet reheating can require a greater percentage of total energy on a machine with open draws or no bottom fabrics. Table 9. Typical dryer energy consumption kJ/kg water evaporated Btu/lb water evaporated Sheet heating 200 85 Evaporation 2,300 990 Air heating 420 180 Noncondensable bleed 45 20 Venting 0 0 Total 2,965 1,275

Vacuum condenser Vacuum condensers are used on many paper machines. They are an especially important component on machines with the need to operate dryers at low (less than approximately 69 kPa, or 10 psig) pressures. Most high pressure board machines lack vacuum condensers. The energy efficiency of the steam and condensate system can be assessed by measuring the heat flow through the vacuum condenser heat exchanger. Blow-through steam and condensate from the wet end dryers is typically discharged to the vacuum condenser. Vent valves from the differential pressure or blow-through flow control loops are typically discharged to the vacuum condenser. Some systems will send flash steam from high temperature condensate to the condenser. These flows represent energy loss from the system. Measuring the energy flow through the vacuum condenser heat exchanger provides an indication of the energy loss from the system. The energy loss from an efficient system will be less than 3% of the total steam supply to the dryers. The energy flow through the condenser heat exchanger can be calculated by measuring the water flow and cooling water inlet and outlet temperatures. The water flow rate can be measured with a portable water flow meter or using a permanently installed water flow meter. The water temperatures can be measured by a temperature probe inserted into the water flow if there is a convenient location. An infrared device can be used to measure the inlet and outlet pipe temperature if a convenient location is not present. An energy loss greater than 3% of the steam flow to the dryers would indicate an opportunity for improving energy efficiency. A complete evaluation of the dryer drainage system is recommended. Other variables There are other variables that affect dryer section performance that should be noted and considered in a dryer section evaluation. These variables include steam and condensate system design, dryer configuration, dryer


diameter, dryer shell thickness, dryer fabric design, machine speed, basis weight, dryer surface contamination, sheet density, sheet thickness, and sheet smoothness. Test equipment suppliers A summary of dryer section process measurements and some test equipment suppliers are shown in Table 10. Addresses and phone numbers for the equipment suppliers are included in the supplier directory. Table 10. Dryer section process measurements Parameter Measurement Units Available

Instrument Type Instrument Suppliers

Dryer surface temperature Temperature Contact Pyrometer

Dwyer, EDL, , Swema, custom built

Dryer pocket humidity Wet/dry bulb temperature, absolute humidity

Psychrometer Thin-film capacitor

custom-built Vaisala,

Dryer fabric tension Force per unit length Tensiometer Honigmann, Feltest, Tensometric

Dryer fabric permeability (portable)

Volume of air per unit of time

Permeability tester Valmet, Frazier TexTest, ATI

Air flows/hood balances Length per unit time Volume per unit time

Thermal Anemometer Pitot Tube Vane Anemometer

TSI, Davis, Dwyer Testo, others

Sheet moisture content/profile

Percent Moisture Portable Finna, MoistTech, Cristini, L&W

Sheet temperature Temperature Contact pyrometer IR Sensor

, Wahl, LumaSense, , Omega, EDL, Testo, many others

The supplier directory listing (Appendix A) was prepared from information available to the committee at the time of publication. Suppliers wishing to be listed or de-listed in the next issue should so inform the Standards Department at TAPPI in writing ([email protected]), referring to TIP 0404-33. Keywords Dryers, Dryer Sections, Drying, Humidity, Temperature, Performance Literature cited 1. Rosenberger, G. Walter and Jeffrey R. Reese, “Profile Testing Improves Dryer Section Diagnostics,” Tappi

Journal, Vol. 73, No. 8, August 1990. 2. Reese, Jeffrey R. “Observations from Testing Dryer Section Performance,” 1992 TAPPI Engineering

Conference Proceedings, p. 629. 3. Hill, Kenneth C., “Paper Drying,” Chapter XII, Pulp and Paper Manufacturing, Volume 7, Paper Machine

Operations, Third Edition, The Joint Textbook Committee of the Paper Industry, 1991, p. 286. Additional information Effective date of issue: April 10, 2017.

Working Group: Jeff Chaloux, Chairman, Kadant Johnson Pekka Kormano, International Paper

mailto:[email protected]


Ray Krumenacker, Ray Krumenacker & Associates Jim Maggard, Kadant Johnson Dick Reese, Dick Reese and Associates Tom Rodencal, Tom Rodencal & Associates Greg Wedel, Kadant Johnson


Appendix A. Supplier directory Advanced Testing Instruments 203 Southpark Drive Greer, SC 29651 864-989-0566 www.aticorporation.com (Fabric permeability) AMETEK Land Inc. 150 Freeport Road Pittsburgh, PA 15238 (412) 826-4444 www.landinst.com (Thermography) Cristini North America 700 Cristini Blvd LaChute, Quebec J8H 4N3 www.cristini.com (microwave moisture) Davis Inotek Instrument 625 East Bunker Court Vernon Hills, IL 60061 (800) 358-5525 www.davis.com (Pitot Tubes, Vane Anemometers, Thermal Anemometers, Pyrometers, Thermometers) Dwyer Instruments, Inc. 102 Indiana Hwy. 212 Michigan City, IN 46360 (219) 879-8000 www.dwyer-inst.com (Pitot Tubes, Hot Wire Anemometers) Electromatic Equipment Co. Inc. 600 Oakland Ave. Cedarhurst, NY 11516 (800) 645-4330 (516) 295-4300 www.check-line.com (Strobes, tension) Electronic Development Labs, Inc. 244 Oakland Drive Danville, VA 24540 (434) 799-0807 www.edl-inc.com (Surface Pyrometers, Infrared Thermometers, Humidity Sensors)

Feltest Equipment BV PO Box 205 6960 A E, Eerbeek Netherlands 31 313 652 215 www.feltest.com (Fabric Tension) Finna Group 1500 W Hampden Ave, Suite 5F Englewood, CO 80110 (720) 963-6500 www.finnagroup.com (portable moisture meters) Flir Systems (AGEMA, Inframetrics, Hughes) 25 Esquire Road North Billerica, MA 01862 (800) GO-INFRA (978) 439-4400 www.flir.com (Thermography) Fluke Corporation 6920 Seaway Blvd. Everett, WA 98203 (800) 44-FLUKE - (800) 443-5853 (425) 347-6100 www.us.fluke.com (Infrared, Thermography) Frazier Precision Instrument Co. 925 Sweeney Drive Hagerstown, MD 21740 (301) 790-2585 www.frazierinstrument.com (Permeability Sensors) Honigmann GmbH Krebsstrasse 2-8 42289 Wuppertal Germany 49-202-870-9720 www.honigmann.com Available in U.S. through Electromatic Equipment Co. (Tension Sensors) Ircon Inc. See Fluke Corporation www.ircon.com (Infrared, Thermography)

http://www.aticorporation.com/

http://www.landinst.com/

http://www.cristini.com/

http://www.davis.com/

http://www.dwyer-inst.com/

http://www.check-line.com/

http://www.edl-inc.com/

http://www.finnagroup.com/

http://www.flir.com/

http://www.us.fluke.com/

http://www.frazierinstrument.com/

http://www.honigmann.com/

http://www.ircon.com/


Lorentzen & Wettre (an ABB Company) 1055 Windward Ridge Parkway Suite 160 Alpharetta, GA 30005 (770) 442-8015 www.lorentzen-wettre.con Luma Sense Technologies 3301 Leonard Ct. Santa Clara, CA 95045 (408) 727-1600 www.lumasenseinc.com (Infrared, Thermography) MoistTech Corporation 199 Tallevast Road Sarasota, FL 34243 (941) 351-7870 www.moisttech.com (NIR moisture) Omega Engineering, Inc. One Omega Drive Stamford, CT 06907-0047 (203) 359-1660 www.omega.com (Infrared, Surface Temperature, Humidity Temperature, Strobe lights) Palmer Wahl Instruments, Inc. 234 Old Weaverville Road Asheville, NC 28804 (828) 658-3131 www.palmerwahl.com (Infrared, RTD thermocouples) Raytek, Inc. See Fluke Corporation www.raytek.com (Infrared) Swema AB Pepparvagen 27, Hokarangen Stockholm, Sweden 46 8-94 00 90 www.swema.com (temperature, humidity, pitot tube Hot wire anemometer)

Tensometric-Mestechnik GmbH Derken 7 42327 Wuppertal Germany 49-202-705214900 www.tensometric.com (Fabric Tension) Testo, Inc. 40 White Lake Road Sparta, NJ 07871 (862) 354-5001 www.testo-international.com (Thermometers, Humidity, Vane Anemometers, Thermal Anemometers) Testing Machines Inc. 40 MCullough Drive New Castle, DE 19720 302-613-5600 www.testingmachines.com (Swema Contact Pyrometers, Moisture) TexTest AG Sonnenbergstrasse 72 CH-8603 Schwerzenback, Switzerland +41 (0)44 321 21 41 www.textest.ch (Fabric Permeability – portable and bench-type) TSI, Inc. 500 Cardigan Rd Shoreview, MN 55126 (800) 876-9874 (651) 490-2811 www.tsi.com (Thermal Anemometer, Vane Anemometer) Unilux, Inc. 59 N. 5th Street Saddle Brook, NJ 07663 (201) 712-1266 www.unilux.com (Strobes) Valmet LTD 400 Memorial Ave. Thunder Bay, ON P7B 3Y5Canada (807) 346-7100 www.valmet.com (Fabric Permeability

http://www.lorentzen-wettre.con/

http://www.moisttech.com/

http://www.omega.com/

http://www.palmerwahl.com/

http://www.raytek.com/

http://www.swema.com/

http://www.tensometric.com/

http://www.testo-international.com/

http://www.testingmachines.com/

http://www.textest.ch/

http://www.tsi.com/

http://www.unilux.com/

http://www.valmet.com/


Vaisala, Inc. 10-D Gill Street Woburn, MA 01801 (781) 933-4500

www.vaisala.com (Humidity) TAPPI has made an effort to ensure that listing of manufacturers in this Technical Information Paper is complete and accurate. If you know other manufacturers that should be included in this listing, please contact the Quality and Standards Department of TAPPI

http://www.vaisala.com/

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