PRES 2 flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Kappa number

A measure of residual lignin in pulp, determined by permanganate consumption; approximately 0.15 × kappa equals percent Klason lignin. Targets: softwood kraft 28-32, hardwood 15-18.

H-factor

A cooking control parameter integrating time and temperature into a single number using the Arrhenius equation, allowing prediction of kappa number and pulp yield at varying temperature profiles.

Effective alkali

The alkaline charge expressed as NaOH equivalent, calculated as NaOH + ½Na2S in white liquor; typically 15-22% on wood for kraft softwood cooking.

Sulfidity

Ratio of Na2S to total active alkali (NaOH + Na2S), expressed as percent; typical kraft white liquor sulfidity is 25-35%, affecting delignification rate and pulp strength.

Oxygen delignification

Alkaline oxygen stage (85-105 °C, 0.5-1.0 MPa O2) removing 40-60% of residual lignin before bleaching; viscosity drop indicates cellulose degradation and loss of selectivity.

Causticizing efficiency

Percent conversion of sodium carbonate to sodium hydroxide in the green liquor causticizing reaction with lime; typically 80-85%, calculated as NaOH/(NaOH + Na2CO3).

Continuous digester zones

Impregnation (110-130 °C), heating, cooking (160-170 °C), and counter-current washing zones; total chip residence 90-180 minutes depending on process configuration.

Modified continuous cooking

MCC process splitting white liquor addition between co-current and counter-current cooking zones to lower kappa number while preserving pulp viscosity and strength.

Digester design pressure

Batch digesters typically 1.0-1.2 MPa at 165-175 °C; continuous digesters 1.0-1.7 MPa at up to 180 °C; design per ASME VIII Div 1 or EN 13445.

Blow tank function

Receives cooked pulp discharged from digester at pressure; flashing steam recovered for liquor heating; vented to recovery to prevent overpressure and odor release.

PREN formula

Pitting resistance equivalent number = %Cr + 3.3%Mo + 16%N. Values above 40 required for bleach plant, above 34 for digester, above 25 for neutral sulfite service.

Chloride stress corrosion cracking

Austenitic 300-series stainless steels crack above roughly 60 °C with chloride above 50 ppm; duplex 2205 or superaustenitic 254 SMO used instead in bleach plant.

Caustic stress corrosion cracking

Carbon steel cracks in concentrated NaOH above 50-60 °C; post-weld heat treatment (stress relief) required for white liquor and green liquor equipment to prevent failure.

Titanium in chlorine dioxide

Titanium Grade 2 is immune to wet chlorine and chlorine dioxide, making it standard for D-stage washers and piping; dry chlorine gas attacks titanium and must be avoided.

Graphitic corrosion

Selective leaching of iron from cast iron in buried or low-velocity service, leaving graphite; use ductile iron or HDPE for underground piping and apply cathodic protection.

ASME VIII Div 1 shell thickness

t = PR/(SE − 0.6P) + corrosion allowance for cylindrical shells under internal pressure; E is joint efficiency (1.0 full RT, 0.85 spot, 0.70 none).

Joint efficiency

Factor reducing allowable stress based on radiographic examination extent: 1.0 for full RT, 0.85 for spot RT, 0.70 for no RT, applied in ASME VIII Div 1 design equations.

MAWP definition

Maximum allowable working pressure at coincident design temperature per ASME UG-98; hydrostatic test at 1.3 × MAWP × (S_test / S_design) per UG-99.

B31.3 allowable stress range

SA = f(1.25Sc + 0.25Sh) for piping thermal expansion per ASME B31.3 Chapter II, where Sc and Sh are cold and hot allowable stresses.

Nozzle reinforcement limits

Area replacement per UG-37; reinforcement must lie within parallel limit of 2× shell diameter and normal limit of 2.5× nozzle thickness from shell surface.

Radiographic density range

Acceptable film density 2.0-4.0 for X-ray per ASME Section V Article 2; IQI essential wire selected by material thickness; acceptance per UW-51 for full RT.

Magnetic particle testing

Surface and near-surface defect detection in ferromagnetic materials only, per ASME Section V Article 7; detects cracks and lack of fusion in carbon steel welds.

Hydrostatic test pressure

1.3 × MAWP multiplied by ratio of test to design allowable stress per UG-99; held long enough for leakage inspection of all joints and connections.

Phased array UT

Multielement ultrasonic technique providing electronic beam steering and focusing; used for thick-section weld inspection and sizing, often combined with TOFD for near-surface resolution.

Fitness-for-service levels

API 579-1/ASME FFS-1 assessment tiers: Level 1 screening, Level 2 assessment, Level 3 detailed analysis; remaining strength factor RSF = LDC/LUC.

Relief valve accumulation limit

Pressure may exceed MAWP by at most 10% for a single relief device and 16% for multiple devices, per ASME VIII Div 1 UG-125 series.

Rupture disk derating

A rupture disk installed upstream of a relief valve requires valve capacity multiplied by 0.9; standard burst tolerance is ±5% of marked burst pressure.

Conventional valve backpressure

Conventional relief valves limited to 10% of set pressure backpressure; balanced bellows valves tolerate 30-50% backpressure depending on trim and manufacturer data.

HAZOP guide words

IEC 61882 methodology applying no, more, less, reverse, part of, and other than to process nodes to identify deviations; risks ranked by severity × likelihood matrix.

SIL PFD ranges

Safety integrity levels per IEC 61511: SIL 1 PFD 10⁻¹-10⁻², SIL 2 10⁻²-10⁻³, SIL 3 10⁻³-10⁻⁴; each IPL must be independent and auditable.

Remaining life calculation

t_remaining = (t_actual − t_minimum)/corrosion_rate, where t_minimum comes from the ASME VIII design formula including corrosion allowance; inspect at half remaining life.

NBIC R-stamp

National Board Inspection Code NB-23 authorization required to repair or alter code-stamped pressure vessels; repairs must follow original code and be documented.