• piston-before-reconditioning-10
  • piston-before-reconditioning-20
  • piston-before-reconditioning-22
  • piston-before-reconditioning-50
  • piston-before-reconditioning-40
  • piston-skirt-before-cleaning-1
  • piston-skirt-before-cleaning-2
  • piston-skirt-after-cleaning-1
  • piston-crown-before-assembling-1
  • Kolbenunterteil-auf-der-CNC-Drehbank-1
  • Kolbenunterteil-auf-der-CNC-Drehbank-2
  • Kolbenunterteil-auf-der-CNC-Drehbank-3
  • Kolbenunterteil-mit-wieder-hergestellter-Sitzfläche
  • Kolbenunterteil-auf-dem-Magnetpulver-Rissprüfstand
  • Die-Prüflösung-wird-aufgetragen
  • Die-Magnetisierung-eines-Kolbenunterteils
  • Mit-UV-Licht-wird-jetzt-nach-Rissen-gesucht
  • Mit-UV-Licht-wird-jetzt-nach-Rissen-gesucht-2
  • Keine-Rissanzeigen-am-Kolbenunterteil
  • kolbenunterteil-vor-der-graphitierung
  • kolbenunterteil-während-der-graphitierung
  • kolbenunterteil-im-brennofen
  • kolbenunterteil-wie-neu-1
  • kolbenhemd-wie-neu-2
  • die-neue-kolbenkrone-wird-zur-montage-vorbereitet
  • kolbenkrone-und kolbenhemd-werden-montiert
  • kolbenkrone-und kolbenhemd-im-montierten-zustand
  • kompletter-kolben-bekommt-korrosionsschutz
  • komplette-kolben-sicher-verpackt
  • kolben-reconditionend-vorher-nachher
  • service-and-spare-parts-for-MAN-Diesel-engines-and-Himsen-Diesel-engines
  • Arrival of pistons with 16,180 running hours for reconditioning at our premises...
  • Packaging is .... let´s say expedient. But at least it survived the long way up to us to Quedlinburg.
  • It follows the unpacking and a first visual inspection for possible transport damage.
  • The piston crowns are disassembled. The waste oil will be disposed.
  • Now the piston rings are removed and the grooves are checked. Result: The grooves 1 and 2 are above the wear limit. In this case the piston crowns must be replaced by new once.
  • We proceed with the piston skirts. They are ready now for cleaning.
  • Shown here: The piston skirts prior to the washing process .....
  • ...and so the piston skirt looks like after washing. Now, the old graphite layer will be removed.
  • In preparation of the final assembling later on, the new WearResist piston crowns are taken out of storage.
  • The seat area of the piston skirt has been seriously damaged by fretting. Unfortunately well known to us...but can be reconditioned.
  • ...here it can be seen very well. This is not a proper seat area anymore to assemble a new piston crown.
  • ...and therefore it must be reconditioned in accordance to the recommondations of the engine manufacturer.
  • After the repair of the seat area has been carried out, the next step in reconditioning is the magnetic particle crack detection.
  • By means of an equitable construction unit conception, our test bench ensures a comprehensive examination of the piston skirt.
  • The test solution is applied generously priot to the magnetization.
  • ...as far as the the magnetization is concerned there is nothing to see...but now it takes place indeed!
  • In a darkened room and under ultraviolet light, now the search for cracks takes place...
  • …. not only from the outside, also from the inside. In the area of hub support…
  • In this case, everything is in order. No cracks. The piston skirt can be reused.
  • The graphitization is carried out in our automatic spray system in order to ensure a uniform thin graphite layer ....
  • During the spraying process, the piston rotates. The piston pin bore and the seat area are previously covered for protection.
  • Then, the curing of the new graphite layer is the final step in the piston skirt overhaul.
  • Done. The piston skirt has a proper seat area and a new graphite layer again.
  • The piston skirt with a reconditioned seat area and new guide show.
  • The new piston crown just before the final assembling.
  • The final assembling of the piston is carried out strictly in accordance to the engine manufacturers advise.
  • We find, the result is something astounding...
  • Before the pistons are packed again now, either a light- or even heavy corrosion protection is applied.
  • Neatly packed and well protected, the pistons are available to the customer again.
  • ...and finally the comparison: Before... After...
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Pistons - Reconditioning of spare parts for power plant and marine diesel engines

Pistons - Examination and repair in accordance to the engine manufacturers advise

Material cracks in a piston skirt after appr. 15.000h of operation
Material cracks in a piston skirt after appr. 15.000h of operation
Material cracks in a piston pin after appr. 34.000h of operation

The production, as well as the overhaul of pistons, belongs to the core competence of SECO GmbH.

More than 85% of the pistons, currently in use in 4-stroke power plant and marine diesel engines, are composite pistons. These pistons are manufactured, ready for installation, by assembling a piston skirt and a piston crown. The remaining 15% of the pistons currently in use are called monobloc pistons. Monobloc pistons are made from one piece either of aluminum mould casting or nodular cast iron. Usually, pistons of this type will be replaced only; not overhauled or repaired.

But what really distinguishes the composite piston from a monobloc piston and why are these different types are existing? The reason for this is the progressive development of engine technology. In the 1960s, engines had ignition pressures of about 120 bar, which was nearly the upper limit of what was technically feasible. Today, modern power generation and marine diesel engines are reaching ignition pressures up to 240 bar. The thereby occurring stresses brought the monobloc piston designs quickly to its limits. Other, high-duty materials had to be brought into use.

A combination of steel -for the piston crown- and ductile iron -for the piston skirt- fulfilled the increased requirements at the mechanical properties. Furthermore, for the first time this combination allowed a predictable overhaul of pistons. When speaking of a composite pistons lifespan, it is actually meant only the period which the piston crown needs to reach his wear limits in accordance to the engine manufacturer specification. A binding indication when a piston crown has to be changed is usually and understandably not given by the engine manufacturers. There are too many factors and variations which influence the wear, such as: fuel quality, combustion quality, quality of separation of fuel and luboil, compliance of maintenance cycles etc.

It is true that the piston skirt is subject to a certain wear. But this wear is considerably lower than of the piston crown and therefore negligible. However, to prevent fatigue failures at piston skirts during engine operation, some engine manufacturers specify to replace the skirts within a range between 70.000 to 90.000 running hours.

From this, by correspondingly carried out FEA calculations, traceable advise of some major engine manufacturers, as a rule of thumb it can be formulated: 

On every new piston skirt 2 or 3 new piston crowns can be mounted before also the piston skirt has to be replaced. 

For this reason, we offer our customers the professional inspection and overhaul of his pistons. That means the exchange of piston crowns for MAN, HiMSEN, MaK and Wärtsilä engines. In this connection each piston skirt will be tested to 100% by means of magnetic particle inspection (MPI).

  • After the income inspection, the pistons will be dismantled.
  • The old piston crown and the mounting equipment are scrapped.
  • The piston skirt is cleaned first and the old graphite layer will be removed.
  • If necessary, the piston skirt will be reworked, and then tested on our MPI bench for already existing cracks.
  • If cracks are found, a report is made with photos and presented to the customer for his final decision for further use.
    (Our experience in this: At about 8% of all the piston skirts of Far East origin cracks were found by MPI after a short period of operation).
  • After the MPI has been carried out, the piston skirts get´s a new graphite coating.
  • Finally a new piston crown with new mounting accessories will be mounted together with the piston skirt.
  • Delivery of the piston.

For the piston skirts, carrying out a proper and careful MPI is of importance. As a manufacturer of pistons, we are operating our own MPI bench, which was developed especially for piston crowns as well as for piston skirts. The magnetization of the piston skirt -before the MPl is carried out- covers the complete skirt and is aligned on it´s circiumference. Carried out in this way, the result of the MPI can be rated much higher than the result by of an MPI where a simple magnetization yoke is used as it is common on board or in the workshop of a power plant.

Sounds interesting? We are pleased to submit our offer to meet your requirements, ...just send us your inquiry.


Piston reconditioning suitable for:
  • MAN 16/24
  • MAN 27/38
  • MAN 32/40
  • MAN 32/40CD
  • MAN 48/60A
  • MAN 48/60B

Hyundai Himsen

Piston reconditioning suitable for:
  • Himsen 17/28
  • Himsen 21/32
  • Himsen H5/33

MBH-Maschinenbau Halberstadt

Piston reconditioning suitable for:
  • VDS48/42
  • VDS48/42AL-2
  • VDG42/48


Piston reconditioning suitable for:
  • Sulzer A20H
  • Sulzer AS/AT25/30
  • Sulzer ASL25/30
  • Sulzer S20
  • Sulzer S20U


For more information please visit the website of our sister company MMS

Marine Motor Service GmbH

Piston reconditioning suitable for:
  • MaK M20
  • MaK M25
  • MaK M32
  • MaK M43


For more information please visit the website of our sister company MMS

Marine Motor Service GmbH

Piston reconditioning suitable for:
  • Wärtsilä VASA32
  • Wärtsilä W32
  • Wärtsilä W34SG
  • Wärtsilä W34DF
  • Wärtsilä W38A
  • Wärtsilä W46A
  • Wärtsilä W46B
  • Wärtsilä W46C
  • Wärtsilä W46D
  • Wärtsilä W46GD