For many, the first thing that comes to mind when considering the petrochemical and chemical industry is aggressive, flammable liquids and mixtures that are pumped from one pipeline to another. These liquids include: acid, ammonia, alkali, and other caustic products. The chemical industry imposes strict requirements on the materials used to transport the any of the products mentioned above, namely, to the arteries of any industry-pipelines.
In most cases, petrochemical production engineers use steel pipelines made of special corrosion-resistant steel that is resistant to a huge range of caustic mixtures. As nothing lasts forever, steel pipelines are subject to significant wear during an operation, which leads to the need for repairs or a planned shut-down of the plant.
One of the latest solutions for the organization of bypass lines and temporary pipelines is flexible lay-flat hoses made of thermoplastic polyurethane.
By Jurij Artiukhov, General Manager, PipeTime, LLC
Thermopolastic polyurethane (TPU) is quite resistant to most known chemical elements, oils, and gas-containing liquids. The material is therefore increasingly used to solve a wide variety of tasks in the chemical industry.
As a rule, polymer additives are used to enhance the strength properties of EPDM and NBR, which ensure the durability of rubber hoses. While each state has its own standards for producing rubber hoses for chemical and petrochemical, such as aggressive liquids-GOST, ISO, API, and so on, all chemical hoses are designed to have maximum resistance to alkalis, acids, oil products, and oils.
The diameters of these hoses range from 10mm to 300mm, and the operating pressures range from 10 to 400 bar.
High-pressure hydraulic hoses (up to 400 bar), are used for the supply of liquids in production and installations in workshops.
To maintain such a high pressures, the power frame of these hoses consist of several layers of steel cord. To ensure maximum tightness, pressed fittings are used. While there is a wide variety of fitting available for this function, the preferred choice for most operators are fittings that hold ISO A or ISO B standards.
Many chemical companies use rubber suction hoses for liquid intake. Liquid intake hose differs from a conventional pressure hose, as they have a steel wire inside the cord, which preserves the shape of the hose when it is working on suction (vacuum).
Due to the thick rubber layer, which gives the hose the desired chemical resistance, as well as the presence of steel wire in the cord of the sleeve, the product is quite bulky and heavy. Many companies have therefore opted to use composite hoses to replace the rubber suction hoses.
Composite hoses have a wide range of diameters spanning from 20mm to 300mm. They also have a working pressure up to 15 bar. The composite sleeve design consists of several layers and provides the system with a longer service life as it aids the pipelines resists damages caused by external mechanical influences; it protects the pipeline from corrosion and abrasion
Further properties of the composite hoses are:
- Inner layer – high-strength polypropylene, polyethylene and polyester films, as well as polypropylene fabrics.
- Reinforcing layer- inner and outer spirals (electroplated steel, aluminum or stainless steel).
- The outer layer is a vinyl-covered polyester fabrics.
- This design significantly reduces the weight of the product, thereby simplifying the process of its operation.
Both rubber and composite hoses can be completed with almost any type of connection: flanged, threaded, quick-release, and so on.
Use of TPU Hoses
The benefit of using flexible sleeve hoses with TUP is seen in cases where the construction of a pipeline is not possible. For example, Surgutneftegaz, a German oil and gas company, used a temporary line from a flexible sleeve at one of its refineries to pump caustic oil sludge from a reservoir to a sump pond.
In this particular case, the distance from the reservoir to the pond was 4200m. Trucks loaded with oil tankers drove up to the reservoir, were loaded with oil sludge, then drove to the pond, where they performed unloading.
Construction of the steel pipeline to replace the trucks was almost impossible for a number of reasons:
- Presence of man-made and natural obstacles,
- High cost of survey design work and further construction,
- Ponds are limited to a certain volume that can be filled in, so the steel pipeline line would lose its relevance over time.
Logistics costs, such as: fuel, drivers ‘ salaries, and truck depreciation, had a significant impact to the company’s budget. Management therefore sought to find a solution that could produce a desired positive economic effect.
In order to eliminate the constant need for the tankers, a flexible pipeline line of flat-rotated DN100 PN16 hoses, in sections of 200m was constructed.
The construction of the 4200m long temporary pipeline took roughly 2 days, with a team of personnel that rarely exceeded 5 individuals.
For assembly, employees used a special winding device that increases the unwinding speed of the sleeve and mechanizes the process. In areas where it was difficult to travel or construction was more complicated, such as under the road crossings, flexible pipeline was installed manually.
The polyurethane hose sections were assembled using special quick-release lock-type connections made of corrosion-resistant steel. These joints also has a polyurethane oil-and gas-resistant cuffs that provide maximum tightness of the joints.
Installation of connecting elements was performed by one person, as only a wrench is required for installation, no special skills are required, just the operating instructions are enough.
The flexible hose itself, as already mentioned, is made of thermoplastic polyurethane (inner and outer walls), the power frame is a polyester fiber, which is intertwined with copper wires to relieve static tension, and this is one of the key points when pumping petrochemical liquids.
The use of such an innovative solution has significantly reduced the costs.
Another interesting example of when a flat-twist hose was used was during the chemical production of EVRAZ. The steel pipeline was subject to wear in a number of places due to the presence of aggressive alkalis and sulfur dioxide in the liquid. Due to wear and tear, there were leaks in the pipeline, and, consequently, the pumping process had to be stopped until the steel pipeline was repaired.
Failure occurred roughly two times in a month to a month and a half long period.
During production tests, a flexible hose DN150 PN10 with flanged connections made of acid-resistant steel was embedded in place of the damaged steel pipeline.
The management of EVRAZ decided to test a 1 meter long piece of flexible hose to see firsthand the resistance of thermoplastic polyurethane. The mounted flexible hose worked for 3 months without complaints and successfully passed the tests.
Now damaged steel sections are replaced exclusively with flexible polyurethane hoses, both as a temporary and permanent pipeline line.
Flat-rolled hoses are also used in chemical and non-chemical industries in many other cases, such as:
- Tank draining/filling,
- Temporary lines for pumping petrochemical products in workshops, hydrocracking plants, etc.,
- Water supply for industrial and other needs.
The chemical and petrochemical industries, so-called “traditional solutions”, namely rubber hoses of various diameters, pressures and purposes, are still however commonly used.
A very important innovation in the development of compounds for the chemical industry was the creation of breakaway couplings and dry connections.
The break-away coupling is a fairly simple and reliable design. It consists of two flanged connections, inside which special valves are installed. When the flanges are closed they leave the flow section completely open, and when the flanged connections are opened, they are instantly sealed.
The essence of the design is that when the maximum load on the axis occurs, the bolts are detached, the internal section is closed, thereby preventing leakage of the fluid being pumped inside.
The main parameters of the break-away coupling are:
- Material of manufacture – both aluminum and acid-resistant, corrosion-resistant stainless steel,
- Operating pressure is up to 40 bar,
- Both threaded (NPT, BSP) and flanged connections.
Dry Quick-Release Connections
Dry quick-release connections are used for connecting the hose to various devices and containers in chemical production. This type of connection completely eliminates the risk of leakage during connection/disconnection.
They have a range of operating temperatures from 163°C to +200°C, working pressure up to 25 bar, and the connection can be made of any type of steel, depending on the requirements of the product being pumped.
Since hoses are made of different types of materials (in particular, steel wire as a reinforcement cord), and can have different weights their use requires special care when performing production tasks.
It is necessary to completely eliminate deflections or creases when hanging or moving, otherwise, the sleeve under its own weight may crack or deform and its further use will become impossible.
The most reliable way to support and move the hose are devices called Hosebun. The device is a special suspension saddle, complete with slings for its attachment. Hosebuns are made of a wear-resistant polymer that has increased resistance to external loads and the influence of many other factors that inevitably accompany the chemical and petrochemical industry. They range in diameters from 25mm to 300mm, and have maximum load capacity up to 6803kg.
The continued development of the chemical industry leads to increased requirements for both hoses and related products in General. As such, the hose and connection market develops and modernizes existing developments every year in order to completely cover the needs of the petrochemical industry, as well as meet all standards and requirements for pumping aggressive, flammable liquids.