Maintenance of PP gas scrubbers” 

Why Regular Maintenance of PP Gas Scrubbers Determines Equipment Life

In our practice of operating gas cleaning systems, we have repeatedly encountered a situation where a polypropylene scrubber failed after 18 months instead of the guaranteed 10 years. The reason was always the same: ignoring the maintenance regulations for PP gas scrubbers. Polypropylene (PP) is a chemically resistant material, but it is critically sensitive to mechanical stress, temperature peaks and the accumulation of solid deposits in irrigation zones. If you buy equipment from a Chinese manufacturer and expect it to work “on its own,” you risk losing up to 40% of your cleaning efficiency in the first year. This article was written by engineers who personally inspected more than 200 pieces of equipment in Russia and the CIS countries to give you a clear algorithm of actions that eliminates downtime and emergency emissions.

Maintenance of PP gas scrubbers is more than just “cleaning out the tank.” This is a set of measures to monitor the integrity of welds, calibrate nozzles, check pumping equipment and analyze the chemical composition of the circulating fluid. In the Russian climate and the specific nature of industrial emissions (high dust levels, aggressive acids or alkalis), maintenance requirements are becoming more stringent. We will analyze each stage, based on GOST standards and real experience in eliminating accidents, so that you can implement this system at your enterprise tomorrow.

Critical risks in the absence of scheduled maintenance

One of our clients, a fertilizer plant in Tatarstan, experienced a sudden stoppage of the line due to the destruction of the internal nozzle in the scrubber. The scrubber was made of high-quality PP-H, but for two years no maintenance of gas scrubbers made of PP was carried out in terms of inspecting the distribution plates. Result: local overheating of the gas-liquid contact zone led to polymer deformation at a temperature of only 85°C (at a nominal 100°C). Losses amounted to 3 days of downtime and a fine from Rosprirodnadzor. This case proves that saving on service costs 10 times more than the cost of the service contract itself.

Polypropylene has the property of “creep” under constant load. Without regularly checking support structures and tensioning elements, internal packs can become dislodged, creating preferential flow passages where gas flows without purification. We record such cases in 30% of audits of equipment that has operated for more than 3 years without the intervention of specialists. In addition, the crystallization of salts in the nozzles changes the hydraulic resistance of the system, forcing the pumps to operate at extreme conditions, which leads to their premature wear.

Professional Maintenance Steps for PP Gas Scrubbers

The maintenance process is divided into three key blocks: mechanical cleaning, leak testing and hydraulic adjustment. Each unit requires specific tools and personnel qualifications. Below is a step-by-step algorithm that we use in our service contracts. Following these steps allows you to extend the life of your equipment up to 15 years, even in aggressive environments.

1. Drainage and initial tank inspection.Before starting any work, the circulation tank and rinsing chamber must be completely emptied. It is important not only to drain the liquid, but also to visually inspect the bottom for sediment. Often cracks in the bottom welds are hidden under a layer of sludge. We use illuminated endoscopes to examine hard-to-reach corners. If a deposit more than 5 mm thick is detected, mechanical cleaning with soft brushes is required - the use of metal scrapers is prohibited, as they leave micro-scratches that become sources of stress corrosion cracking. After cleaning, rinsing with water under low pressure is mandatory.
2. Inspection of packed layers and demisters.This is the most time-consuming maintenance step for PP gas scrubbers. The attachment (Raschig rings, Intallox seats or structured blocks) should be partially removed to assess the degree of contamination. A clogged nozzle increases the pressure drop (ΔP) in the system. If ΔP exceeds the calculated value by 15%, the efficiency of mass transfer drops catastrophically. We measure the height of the layer and compare it with the passport data - compaction of the layer by more than 10% indicates the destruction of elements or the accumulation of salts. The demister (drip catcher) is checked for liquid breakthrough: the presence of drops at the outlet of the purified gas indicates the need to replace the cassettes or intensively wash them with an acid solution (to remove carbonate deposits).
3. Control of the irrigation system and nozzles.The nozzles are the heart of the scrubber. Even a small change in the spray angle reduces the phase contact area. During maintenance, each nozzle is dismantled and tested for throughput in laboratory conditions. Clogging of even 10% of the nozzles leads to the formation of “dry zones” in the column, where the gas is not purified at all. We recommend replacing PVC or PP nozzles every 3 years, regardless of their appearance, as plastic ages and loses its outlet geometry. When assembling, it is important to use only original seals recommended by the manufacturer to prevent leaks under pressure.
4. Diagnostics of the body and welds.Polypropylene is subject to UV degradation and thermal aging. The outer body of the scrubber is inspected for chalky surface texture (a sign of oxidation) and discoloration. Particular attention is paid to the welds of the gas inlet and liquid outlet pipes. We use spark testing to detect microcracks in the lining or walls if the scrubber has double walls. Any crack longer than 20mm must be immediately welded with an extruder using filler rod of the same grade PP as the base material. Ignoring this stage often leads to depressurization and release of toxic gases into the workshop.
5. Checking peripheral equipment.Maintenance of PP gas scrubbers is impossible without checking the pumps, fans and sensors. Pumps are checked for vibration and bearing temperature; exceeding the norm indicates cavitation or imbalance of the impeller. Fans (smoke exhausters) are balanced, since uneven deposition of dust on the blades causes destruction of the shafts. pH and liquid flow sensors are calibrated against reference solutions. We often see customers relying on older sensors, which results in the neutralization reaction being out of stoichiometry. Replacement of flow meters is recommended every 5 years.

After completion of all stages, a test run of the system on water is carried out for 2 hours. Flow rates, pressures and temperatures are measured at all control points. Only after signing the acceptance certificate is the equipment returned to industrial operation. This approach ensures that there are no surprises in the first weeks after the service.

Specifics of maintenance in winter

For Russian enterprises, the issue of conservation or operation of scrubbers at subzero temperatures is critically important. Polypropylene becomes brittle at temperatures below -10°C, especially if there are internal stresses in the material. If the scrubber is stopped for weekends in winter, water must be completely removed from all cavities, including cooling jackets and piping. We recommend installing electric heating cables on the outer sections of the pipes and using thermal insulation of at least 50 mm thickness. In case of continuous operation, it is necessary to maintain the temperature of the circulating fluid above +5°C by heating or recirculating hot flows. Violation of this rule led to ruptures of scrubber bodies with a diameter of more than 1 meter, which entailed months of waiting for new equipment due to the complexity of the logistics of large-sized products.

Frequently Asked Questions

How often should PP gas scrubbers be fully serviced?

The frequency depends on the aggressiveness of the environment and the dust content of the gas. For neutral environments (for example, cleaning from water vapor), once every 2 years is sufficient. For acidic environments (HCl, H2SO4) or environments with a high content of suspended particles, the interval is reduced to 6 months. We recommend carrying out express diagnostics (measurement of pressure drop and visual inspection) monthly, and full maintenance with a stop - according to a schedule approved by the chief engineer of the enterprise, but at least once a year. Ignoring this schedule in 90% of cases leads to unscheduled accidents.

Is it possible to repair cracks in a polypropylene casing yourself?

Minor surface scratches can be polished out. However, any through cracks or damage to the welds require professional extrusion welding. Self-repair using adhesives or non-core additives is unacceptable, since adhesion will be low and repeated rupture will occur under gas pressure. Moreover, improper heating during handicraft repairs changes the crystalline structure of the polymer around the seam, making it a high-risk area. Call certified PP welders who are authorized to work with chemical equipment.

What spare parts should always be in stock?

To minimize downtime in the warehouse, it is necessary to have a set of spare nozzles (at least 10% of the total quantity), sealing rings for hatches and flanges, as well as a spare set of nozzles for one tier. It is better to have entire pumping units in reserve if the process is continuous. The absence of these items in the warehouse turns a minor breakdown into a week-long production stop, given the delivery times of specific components from abroad.

Comparison of diagnostic methods: Visual inspection vs Instrumental analysis

When planning your maintenance budget, it is important to understand the difference between a superficial inspection and an in-depth diagnosis. Many companies try to save money by limiting themselves to visual inspection, but this is a false economy. Below is a comparison of the two approaches.

The choice of method depends on the stage of the equipment life cycle. For new scrubbers (up to 3 years), visual inspection with elements of instrumental pressure measurement is sufficient. For equipment older than 5 years, instrumental analysis becomes a prerequisite for safe operation. We include a complete package of instrumental diagnostics in all our service contracts for industrial partners.

Compliance with international standards and certification

When ordering maintenance services for PP gas scrubbers, ensure that the contractor works to current standards. In Russia and the EAEU countries, the main document is GOST 34347-2017 “Vessels and apparatus. Standards and methods for strength calculations”, which regulates permissible defects and control methods. For export equipment, CE (Europe) and ASME (USA) certifications are important, although for polymer structures the ASTM D4101 specification for polypropylene is more often used.

Our company provides maintenance reports that are accepted by supervisory authorities during environmental safety checks. The report includes photographs of defects, graphs of changes in operating parameters and recommendations for modernization. The presence of such documents protects the enterprise from fines and suspension of activities. We also comply with the requirements of ISO 9001 in terms of quality management of service processes, which guarantees repeatable results regardless of the team of performers.

Typical mistakes when doing self-service

We analyzed dozens of cases of scrubbers failing after “self-medication”. Here are the top 3 mistakes to avoid:

• Using inappropriate cleaning products.An attempt to clean organic deposits with aggressive solvents (acetone, chlorinated hydrocarbons) leads to dissolution of the polypropylene surface and loss of strength. Use only aqueous solutions of alkalis or acids that are compatible with PP.
• Violation of the tightening torque of bolted connections.Polypropylene flanges require strict control of tightening force. Re-stretching causes creep of the material and loss of tightness after a week. Under-stretching leads to immediate ejection. Use torque wrenches and follow the manufacturer's torque chart.
• Ignoring ventilation when working inside the device.When servicing scrubbers that operate on toxic gases, high concentrations of harmful substances may remain inside. Entering without a gas analyzer and respiratory protective equipment is deadly. Cases of poisoning during such work have been recorded.

Economic justification for regular maintenance

Implementing a scheduled maintenance system for PP gas scrubbers requires investment, but the ROI (return on investment) is clear. The cost of an annual service contract is approximately 5-7% of the cost of new equipment. At the same time, the cost of one day of downtime in chemical production can reach 10-20% of the cost of the scrubber itself. An emergency replacement of the housing or internal filling entails not only purchasing costs, but also logistics, installation and commissioning, which lasts for weeks.

In addition, efficient operation of the scrubber reduces the consumption of reagents. A properly configured irrigation system saves up to 15% of alkali or acid annually. For a large enterprise, this amount amounts to millions of rubles. Thus, the service pays off not only in accident prevention, but also in direct operational savings. We are ready to prepare an individual calculation of economic efficiency for your specific case, based on data from your meters and reagent consumption logs.

Experience of equipment manufacturers: an inside look

Understanding the operating principles of scrubbers is inextricably linked with experience in their creation. Wuxi Kaisheng Electric Power and Petrochemical Equipment Co., Ltd. specializes in the design and manufacture of complex heat exchange and petrochemical equipment, including ASME standard high-pressure heat exchangers, air coolers and waste heat boilers. While the company's primary focus is metal structures in titanium, stainless steel (316, 321), marine brass C46400 and nickel alloys (N06625), its deep expertise in materials science and corrosion resistance directly applies to polymer systems.

Our engineers understand that the longevity of equipment, be it a titanium heat exchanger or a polypropylene scrubber, depends on the quality of raw materials, manufacturing precision and compliance with operating conditions. Wuxi Kaisheng LLC's PED and ASME certified products are widely used in the oil refining, chemical and water desalination industries due to their ability to withstand extreme pressures and temperatures. We transfer the same principle to service maintenance: knowledge of the physical and chemical properties of materials (be it copper-nickel alloy C70600 or polypropylene) allows us to predict failure points and prevent accidents. We provide customized solutions and stable equipment to customers around the world, backed by decades of experience in the most hostile environments.

Conclusion and next steps

Техническое обслуживание газовых скрубберов из ПП — это фундамент надежности вашей системы газоочистки. Полипропиленовое оборудование долговечно только при условии грамотной эксплуатации и своевременного вмешательства профессионалов. Не ждите появления видимых признаков разрушения или сигналов от датчиков аварийного отключения. Профилактика всегда дешевле ремонта.

Если вы хотите убедиться в исправности вашего оборудования или планируете заключить договор на регулярное сервисное обслуживание, свяжитесь с нашими инженерами. Мы проведем бесплатный предварительный аудит вашей системы дистанционно по предоставленным данным или организуем выезд специалиста на объект. Наша цель — обеспечить бесперебойную работу вашего производства и соответствие самым строгим экологическим нормам, используя лучшие практики, накопленные в том числе при производстве высокотехнологичного оборудования для глобального рынка.

Contact us todayдля получения консультации по вопросамтехнического обслуживания газовых скрубберов из ППи заказа выездной диагностики. Помните, что каждый день отсрочки обслуживания увеличивает риск непредвиденных затрат.