Record of compressor equipment application at oil refinery

Lecture content

Introduction. General information and notions on rotating equipment - as exemplified by the piston compressor plant of Sibur-Neftekhim JSC, Dzerzhinsk.

Experience of operation and failures of injectors at typical hydrogen units of Ryazan Oil Refinery Company JSC:

  • air blower diffusor at the fractioning fluid catalytic cracking unit (FFCC);

  • centrifugal hydrogen compressor 02-TsK-1 at the isomerization unit “Izomalk-2-LIN-800”.

Summary.

Introduction. General information and notions on rotating equipment - as exemplified by the piston compressor plant of Sibur-Neftekhim JSC, Dzerzhinsk.

Rotating equipment (compressors, pumps, air blowers)/injectors

The term compressor (pump) shall mean:

  • a driven (e.g. by electric motor) compressor (pumping) unit,

  • with piping of pipelines, pressure vessels (e.g. surge dampers, interstage gas coolers),

  • valves and fittings, pressure safety valves,

  • lube system, cooling system, pulsation damper

  • and control system, i.e. electrical equipment of automation and control

Modern gas compressor is the main and central part of the integrated system incorporating a motor, cooling elements, pipelines and other components. Engineers develop such systems based on the terms of reference, subject to the requirements of standards, particular industrial safety specifications. So, for example, the requirements of standards API-617, API-618 cover centrifugal and piston compressors of petrochemical industry. In Russia these are the requirements of the Technical Regulations of the Federal Agency on Technical Regulation and Metrology (GOSTs), the standards of associations, the requirements of the Russian Federal Service for Ecological, Technical and Atomic Supervision issued as the Federal norms and rules for industrial safety (FNP PB).

Sample graphic representation of the compressor, sample documentation and photos are provided below.

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OPERATION AND MAINTENANCE MANUAL

VERTICAL PISTON COMPRESSOR

KSVGNL-3, 1050KW GAS MIXTURE COMPRESSOR

CUSTOMER: SIBUR-NEFTEKHIM JSC

PROJECT DESCRIPTION: ETHYLENE OXIDE AND GLYCOL PRODUCTION

TAG No.: C-320

180-12, OKOG-RI, CHILWON-MYON, HAMAN, GYEONGNAM, KOREA

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Pic. - General view of the piston hydrogen compressor plant.


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Pic.- Compressor plant of Sibur-Neftekhim JSC, ethylene oxide and glycols production, Dzerzhinsk, the Nizhny Novgorod region, 2017.

Experience of operation and failures of injectors at typical plants of Ryazan Oil Refinery Company JSC:

  • air blower diffusor at the fractioning fluid catalytic cracking unit (FFCC);

As practice shows, the main reasons of the compressor equipment failure are as follows:

  1. violation of the rules of compressor operation;
  2. incorrectly selected component parts used for installation and repair;
  3. increased vibration;
  4. foundation failure;
  5. late replacement of wear and tear assemblies and parts;
  6. natural depletion of the remaining service life of the unit

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Pic. – General view of the fractioning fluid catalytic cracking unit (FFCC).

During the air blower pre-commissioning at the fractioning fluid catalytic cracking unit (FFCC), cast-iron diffusor collapsed. According to the submitted certificates, die cast parts are made of SCh 15 cast iron and conform to the requirements of GOST 1412-85 in terms of chemical composition and mechanical properties, and were subject to respective stress relief.

Review of the undertaken examination showed that acoustic characteristics of cast iron exceeded the critical values for ultimate strength (below 130 MPa) and average length of graphite plates (over 150 μm):

  • ultimate strength - the obtained data comparison with the requirements of GOST 1412 and, in particular, with the certificate data showed that the obtained ultimate strength value is below the values specified for SCh 15 cast iron;

  • considerable graphitization impairs the metal strength resulting in inadmissible ultimate strength values.

  • centrifugal hydrogen compressor 02-TsK-1 at the isomerization unit “Izomalk-2-LIN-800”.

During pre-commissioning of the centrifugal compressor 02-TsK-1 make 6 RSA 36 HowdenCKDCompressors (hydrogen-based), an increased relative motion was recorded, and the compressor was stopped. Disassembly of the compressor on the rotor (see the photo below) revealed the following:

  • chipping and spalling of metal on the blades of impellers 1,2,3;

  • breaking-out of metal on the blades of impellers 3,4,5,6;

  • fractures and collapse of the blades of impeller 6;

  • breaking of small metal parts on the end surfaces of impellers 5,6;

Description and purpose of the item under examination

Centrifugal compressor 02-TsK-1 is designed for hydrogen compression at the low-temperature isomerization unit “Izomalk-2-LIN-800”. Compressor performance is 28782 kg/h; suction gas pressure is 2.2 MPa, discharge gas pressure is 3.63 MPa; suction gas temperature is 400С, discharge gas temperature is 97.20С. It is designed in compliance with the requirements of API 617 standard.

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Pic.- Rotor of the compressor 02-TsK-1 of “Izomalk-2-LIN-800” unit.

The rotor consists of a steel shaft and six titanium impellers (the disc with integral blades and the welded envelope disc). Impellers are closed-type, welded, with integral blades. Impellers diameter is 360 mm. Impellers material: Ti base; Al 6.0% ;V 4.1% ; Fe 0.14% ; limit strength 950 MPa; hardness 293-296 НВW (China, titanium quality certificate - series No. 12082101 dd. 21.08.2012).

Appearance of the internal surfaces of discs and blades is presented in the photo below. Most defects are on the impeller blades.

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Pic.- Appearance of the internal surfaces of discs and impeller blades.

It is worth mentioning that use of titanium blades always involves a risk of titanium fires, particularly in case of blades failure. Titanium alloys usage for compressor discs may also involve probable chord- and height-oriented deterioration of material properties in disc workpieces, compared to the materials passport data (certificates data). Besides, the drawbacks include non-homogenous properties of discs and blades across the workpiece areas.

Acoustic, in particular ultrasonic, testing is known to be a sensitive method of detecting discontinuities in the materials. It is based on investigation of elastic waves spreading in the inspected part material. In the absence of discontinuities, acoustic waves generated by the source spread in the inspected material linearly, as a divergent beam. In case of discontinuities, waves are reflected, deflected and dispersed. UT is mandatory for inspecting the critical parts, requires a considerable commitment to its implementation and a sufficient qualification of the specially trained staff. UT of the items made of titanium alloys using traditional methods of hot shaping, and, as a result, having a non-homogeneous structure, is characterized by an increased level of acoustic noise. At present, UT of critical items of heat-resistant titanium alloys is performed with a sensitivity providing for detection of flat bottom hole (artificial defect) 0.8 mm dia. therein.

Gas-filled inclusion (GFI) having a high degree of embrittlement is determined to be the most hazardous and hardly detectable defect of the titanium alloy. It is characteristic of titanium alloys only, in particular made of an ingot of double vacuum arc remelting. GFI is a metal region with an increased content of nitrogen (from 3.5 to 14.8 % wt. of nitrogen) and/or oxygen (up to 2.5 % wt.) and with the crystal structure of α-phase. GFI is a hazardous defect with regard to operational properties of the material, as it is brittle and has a hardness by several times exceeding that of the basic material. Under operational loads in the conditions of cyclic loading it becomes the source of fatigue crack growth, the crack starts growing, the part is collapsing.

It is worth adding that when inspecting particularly critical items having a rather complicated geometry and high price, it is impossible to ensure compliance with the stringent quality criteria using manual inspection. Obviously high accuracy values, sophisticated alloys and high quality requirements make manual inspection merely impossible. To provide for smooth organization of automated non-destructive testing, the item is placed into the full immersion inspection tank, and a high-accuracy scanner sounds 100 % of the item according to the 3D model set by an operator (see the picture below).

Pic.- Discs inspection unit UKD-1200 providing for automated UT of discs up to 1200 mm in diameter

From the above references it is clear that the process of discs manufacturing of titanium alloys requires high production standards. The most stringent requirements to the process shall apply with regard to temperature and time parameters during the workpieces manufacturing. Properties monitoring based on generally accepted criteria (based on excess metal samples) do not always reflect the state of the material inside the workpieces. It presses to rigidly regulate the process and introduce non-destructive testing of 100 % scope of the finished part shape within the workpiece, and at the stage of a finished part.

Findings:

  1. Main areas of the impeller fragment damages are located on the envelope disc and the areas of its junction with the blades (through holes and spalling areas). Welded joints made by electron beam welding have a significant number of defects. Usually such defects are related to violations of the processes at one of impellers production stages.

  2. For step-by-step inspection of the manufacturing process of the rotor with titanium impellers and detection of defects, it is recommended to use automated immersion ultrasonic inspection improving the defects detectability.

Conclusion. “We should know ten times as much as we do”

Two examples of rotating equipment failure at two Refinery plants are reviewed, these are hazardous production facilities related to usage of large hydrogen volumes. Findings are conclusive: manufacturing of such devices requires new processes and new approaches. I.e. “We should know ten times as much as we do”, Yu.B. Khariton. The colleagues called this rule the “Khariton’s criterion”. The physicist Khariton (Physical-Technical Institute) was a chief designer for developing the atomic and hydrogen bomb, an “engine” man, a close associate of Kurchatov and Sakharov. “Pray God those who follow us would find the ways, would have firm spirit and decisiveness striving for the better not to do the worse”

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The academician July Borisovich Khariton near the shell of the first Soviet atomic bomb RDS-1, in the Polytechnic museum the shell of the atomic aviation bomb RDS-12 became a monument of science and technology, was recognized as a memorial.

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