【Q&A Question 261】2017.09.19
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【Q&A Question 261】September 19, 2017: Briefly explain the definition of the downward displacement of the piston rod in a reciprocating compressor. (Unless otherwise specified, all questions and answers are based on hydrogenation units.) ) The answers to the daily questions change, and today’s answers are shown in subsequent questions. For management purposes, if you need to view content from a few days ago, please go through the summary post below. Summary post of Q&A questions for 2017 (updating now): http://bbs.hcbbs.com/thread-1657793-1-1.html Summary post of daily questions for 2017 (updating now): http://bbs.hcbbs.com/thread-1657794-1-1.html Summary post of Q&A questions for 2016 (already updated): http://bbs.hcbbs.com/thread-1597792-1-1.html (Source: Haichuan Chemical Industry Forum) [Q&A Question No. 253] September 11, 2017: Methods for dealing with liquid accumulation in steam generators. Methods for dealing with liquid accumulation in steam generators: 1. First, disconnect the heat source from the steam generator to allow it to cool down. 2 Open the steam vent valve to release the steam from the pipeline system. After the temperature of the Class 3 steam generator drops, add water to the drum until the normal liquid level is reached, and then restart it following the normal startup procedure. 4. When the liquid level is low, never add water to the steam drum immediately to avoid accidents caused by sudden boiling. 【Q&A Question 254】 September 12, 2017: What is the purpose of strictly controlling the metal content in hydrogenation feed oil? Heavy metals, particularly nickel, vanadium, copper, lead, etc., can easily poison catalysts; even trace amounts of such metals can cause the catalysts to become permanently inactive, thereby reducing the operational lifespan of the facility. 【Q&A Question 255】 September 13, 2017: What are the four key precautions for summer? The four key precautions in summer are: protection against lightning ； Flood control ； Heat prevention and cooling ； Preventing collapse [Q&A Question 256] September 14, 2017: During shutdowns, pipelines carrying light hydrocarbons, naphtha, etc. are prone to expansion, overpressure, and explosion during high-temperature steam purging. How can this be prevented? It is strictly prohibited to use steam for purging such pipelines; instead, they should be washed with water first and then purged with nitrogen. [Q&A Question 257] September 15, 2017: How should a circulator be handled during a power outage? Verify interlocking; divert medium-pressure steam to vent, divert backpressure steam to vent as well; close the inlet and outlet manual valves of the compressor; start the booster pump; perform manual rotation; when the pressure is below 0.7 MPa, switch the main sealing gas to nitrogen. 【Q&A Question 258】 September 16, 2017: Which parts of the hydrogenation unit are equipped with dedicated fire protection steam lines? “The reaction furnace, the steam used for purging the reboiler furnace, the steam protection rings of the heating furnaces, the fire protection steam rings at the inlet and outlet of the reactor, the steam lines at service points, and the fire protection steam lines for the towers.” 【Q&A Question 259】 September 17, 2017: What are the different types of poisoning of hydrogenation catalysts? Catalyst poisoning can be divided into reversible poisoning, irreversible poisoning, and selective poisoning. 【Q&A Question 260】 September 18, 2017: What is the state of the air valve when the compressor is operating at 50% and 100% load? At 50%, the outer air valve activates; at 100%, both the inner and outer air valves activate.
Piston support rings are wear-prone components, and the wear of these rings inevitably leads to a drop in the position of the piston rod. During operation, the piston rod is subjected to long-period alternating loads, which have a significant impact on its lifespan.
Main reasons: wear of the piston rod, wear of the packing support ring, wear of the piston guide sleeve, the crosshead slipping or being worn, loose connection between the piston rod and the crosshead, etc. Positive and negative signs: indicate whether something is closer to or further from the reference point; generally, the midpoint of the gap is taken as the reference point. When vibration occurs, the gap either increases or decreases. By measuring the changes in the electromotive force associated with the gap and converting these values into electrical signals, it is possible to determine the displacement. It should be noted, however, that a positive value does not necessarily mean being closer or further away – its meaning is defined by convention; this can be asked to the instrumentation personnel who were involved in the project
Downward displacement caused by piston rod wear, packing support ring wear, piston guide sleeve wear, crosshead slide or crosshead wear, and loose connection between the piston rod and the crosshead.
Wear of the piston rings or top rings, bending of the piston rod, wear of the crosshead, or issues related to installation that cause upward or downward movement; positive and negative refer to upward or downward movement respectively
The piston rod of a reciprocating compressor will sink when there is looseness at the connection between the piston rod and the crosshead, or when the piston support rings are worn out.
If it is detected by a displacement probe, first check whether the probe is loose; it is quite common for the movement of the reciprocating machine to cause the probe to become loose. If this cause is ruled out, the second possible reason is looseness at the connection between the crosshead and the piston rod; in such cases, slight abnormal noises may be heard from the middle part of the device, so it’s important to pay close attention. The third reason is wear of the guide ring on the piston (also known as a support ring).
Wear of the piston rings or top rings, bending of the piston rod, wear of the crosshead, or issues related to installation that cause upward or downward movement; positive and negative refer to upward or downward movement respectively