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By Sari Kurvinen, Laboratory Manager / Chemist (M.Sc.), KL-Lämpö Oy

The heart of KL-Lämpö

A private water and research laboratory has formed the core of KL-Lämpö’s business ever since the company was founded in 1993. Personally, it has been a privilege to observe first-hand the growth and development of both the company and its laboratory operations since 1997.

By Janne Rantanen, Product group manager / Regional manager

Water purification includes a wide variety of possibilities to achieve the desired result. Filtration is a very popular and simple method of water purification.

The purpose of filtration

Filtration is used to remove e.g. solids from water and other heat transfer liquids. The filtration need is influenced by water quality and the set water standards. Water quality varies depending on the origin of water e.g. surface water, well water or municipal water. The quality of municipal water may be sufficient for household use but not for industrial applications.

Water filters are used in many industrial applications such as cooling, aqua heat recovery and ventilation systems. Without filtration deposits and other impurities circulate in the system causing corrosion and increased energy consumption. They may also block the system and disturb the operation of regulating units.

Criteria for filter selection

Choosing the right kind of a filter for each purpose depends on the following criteria:

• System (type): heating, cooling, heat recovery, district heating, sealing water, cooling tower etc.
• Volume of water (if a closed system)
• Origin of water: municipal water, untreated water, river or lake water, mechanically processed water, chemically purified water, district heating water, water-glycol solution etc.
• Worst contaminator: deposits, iron sediment, dirt, humus, sand, dust, turf etc.
• Flow rate of water/liquid: m3/h or l/s
• Connection: main flow or by-pass
• Diameter of connection
• Maximum water/liquid temperature
• Maximum water pressure
• Desired filtering degree
• Total solids (if known)

By Kalle Jalonen, Project engineer, KL-Lämpö Oy

We detect the problems of the wind turbine cooling systems with laboratory analyzes, before the problems cause high maintenance or repairing costs. By implementing the analysis data we can solve possible problems in advance.

Though the coolant of wind turbine cooling system may already be in bad shape the turbine may still work adequate. If the cooling ability is good enough the general condition of the cooling system and the coolant may be forgotten. When the first heating alarm occurs the system is often already in a state in which it should never be. The time from the starting point of corrosion to a leaking system can be surprisingly short even though the system hadn´t given any signs of the problems. By frequent monitoring the condition of the coolant much of the problems can be avoided.

Configuration vulnerable to corrosion

The materials used in wind turbine cooling systems are commonly aluminium, plastic and rubber. Rubber hoses are inexpensive, light-weight and easy to install, but unfortunately they let oxygen through in time, little by little. This is why these systems often contain small amounts of air. Air is bad for heat transfer abilities, but it also predisposes the system to phenomenon we know as corrosion.

Aluminium is very vulnerable material to corrosion and it is used in crucial parts of the cooling system. In addition stainless and acid-proof steels are used in the system but these materials are strong and durable. Sometimes also black iron is used and it is also vulnerable to corrosion.

Against corrosion with inhibitors

Inhibitors alias corrosion protection chemicals are used in order to prevent corrosion. Inhibitor is added to the glycol solution (coolant) already in the manufacturing stage. As time goes on the amount of inhibitor in coolant can decrease; the inhibitor slowly disintegrates to the system because the coolant in under great mechanical stress. This weakens the corrosion protection ability.

The amount of inhibitor in the coolant should be constantly observed and added if found necessary. If this is not done and the amount of inhibitor decreases too low the result can be corrosion. In worst case scenario the corrosion becomes so bad that the system starts to leak. If there is a leak in the radiator or even worse, inside the converter cabinet, the damage and the repairing operations can become very expensive and laborious. And at the same time the turbine will be off-line and thus unprofitable.

Deposits

When corrosion starts to appear in the cooling system different materials from the system surfaces will start to dissolve into the coolant. These materials and the disintegrated inhibitor can form deposits. Even though the amount of the inhibitor has been kept on a good level the disintegrated amount will not vanish from the system by itself. All of these impurities can form so bad deposits that the system can even clog in certain parts.

The cloggings and the deposits significantly reduce heat transfer abilities of the system: sometimes so badly that cooling is no longer efficient enough. At that point the energy production of the wind turbine can start to suffer from overheating alarms and downtimes.

Different inhibitors have different structures and features: they are often completely different chemicals. Sometimes there have been situations where the type of the coolant used in a cooling system has not been certain, or it has not been clarified. In this uncertain situation, a coolant with different kind of inhibitor has been added to the system. This is a terrible mistake: different inhibitors can form very bad deposits when mixed together. After this kind of mistake, the system usually needs a thorough cleaning operation to get it back to its proper performance level.

However, the deposits and the possible corrosion will age the coolant in every wind turbine cooling system to a point, where the system has to be cleaned and the coolant has to be replaced to restore the original heat transfer ability.

How to inspect the coolant?

Regular laboratory analyzes are easy and informative ways to examine not only the coolant, but also the condition of the cooling system. In this analysis the most common metals which weaken heat transfer abilities are defined as well as the most crucial physical abilities of the coolant.

If there are also deposits to examine the composition can be clarified with separate EDS-analysis. If some impurities appear in the analysis the surfaces of the system are deemed to have deposits as well. On system surfaces even the smallest amounts of impurities will decrease the heat transfer ability. The possible corrosion in the system can also be detected by the analysis. In wind turbines the possible deposits and corrosion are in very important position because the cooling systems are constantly under very high mechanical stress.

On basis of the analysis proper maintenance operation plans can be made to improve the decreased cooling ability.

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By Jonna Lehtinen, Technical assistant, KL-Lämpö Oy

When you ask someone ”What is quality?”, you can get many kinds of answers. Each of the answers encompasses some things that are typical of quality. It is a common knowledge that quality is based on customers’ needs, requirements and expectations towards the products and services of the organization. The quality is considered to be at a good level when the customer is feeling satisfied. The determination of quality depends entirely on the organization and its approach to the matter. In order to build long term customer relationships our company aims at recognizing and anticipating even the hidden needs and expectations of our customers.

By Pekka Ojala, Product Group Manager, KL-Lämpö Oy

Boiler circulation control depends mainly on two factors: pH and oxygen (redox potential).

The control of the conditions gets even more critical while both iron and copper are present in the system. As pH is raised from pH > 8,9 the corrosion decreases for iron, but rapidly increases for copper (Fig. 1). This is especially true for ammonia. The protection of both the metals is however possible by proper selection of the alkalizing amines.

By Pekka Ojala, Product Group Manager, KL-Lämpö Oy

Boiler circulation control depends mainly on two factors: pH and oxygen (redox potential). Chemicals are needed to maintain adequate control parameters. Thus, also conductivity is raised. How to simultaneously reach these two controversial goals?

Increased turbine efficiency has led to tighter steam conductivity requirements. On the other hand, chemicals are needed to maintain high enough system pH. Consequently, also conductivity will raise.

By Kalle Jalonen, Project engineer, KL-Lämpö Oy

The type of coolant used in cooling systems is not the first thing on our mind when building a new wind turbine. Even if the wind turbine has been in operation for a while, there are other maintenance projects that take priority. However, attention should be paid to the type and condition of coolants in order to avoid unnecessary repair costs.