Replacing the lining should be as easy as possible, in order to minimise downtimes. If your work bowl is worn, contact TROWAL SERVICE. Using an existing replacement bowl, we produce a duplicate of your product, fit a new lining and deliver to you. Your worn bowl is then re-used as a replacement component.

Is the lining of your mass finishing machine worn? With a replacement bowl, you can get a brand-new product while keeping downtimes to a minimum.


The abrasive media used in mass finishing processes abrade not only your workpieces, but also the work bowl. That is why the steel bowls of our mass finishing systems are protected with a polyurethane lining that is particularly resistant to tears. But even this elastic tear protection needs replacing from time to time.


Replacing the lining should be as easy as possible, in order to minimize downtimes. If your work bowl is worn, contact TROWAL SERVICE. Using an existing replacement bowl, we produce a duplicate of your product, fit a new lining and deliver to you. Your worn bowl is then re-used as a replacement component.



  • Worn component made as good as new, with manufacturer guarantee
  • Tested and expertly repaired steel construction with no nasty surprises
  • Low downtimes
  • Lining made from high-quality polyurethane, poured and correctly tempered under manufacturing conditions
  • New separation device (separator flap with control) if on original



The following photos provide details of a work bowl returned to us with worn protective lining and damage to the steel structure.

Our Quality Control team assesses the condition of the work bowl to determine if it can be re-used in the replacement bowl program or must be scrapped.

If the steel structure is cracked or shows other major damage, the work bowl is scrapped. In such a case this particular work bowl is replaced by a brand-new unit – of course, without any additional costs to the customer who returned the old work bowl.

The photos demonstrate that the lining is typically worn in many places. This can only be fixed with a completely new protective lining. In very few instances small faults in the protective lining can be patched up with special polyurethane (PU) repair kits. But this is only a temporary fix that is mainly used to keep your machine running without any additional damage to the steel structure, until the replacement work bowl has arrived.


Depending on the finishing application, the polyurethane lining of a mass finishing work bowl will wear more or less quickly. Once the lining is worn down to the steel surface of the work bowl, the bowl must be relined! To match the quality of our new equipment linings we are doing the relines not at the customer’s premises but in our well-equipped TROWAL manufacturing facility. To minimize the down times for our customers, we are utilizing a so-called replacement bowl program. Key feature of this program is that you can utilize your old work bowl until the replacement bowl has arrived at your site.

This is how the replacement bowl program works:

  • Whenever the protective lining in your work bowl has worn, you order a replacement bowl at the CUSTOMER SERVICE.
  • With the help of the internal order, commission or equipment serial number we identify your machine and select an identical product from our pool of used work bowls.
  • In our production line a duplicate of your work bowl is produced.
  • In case of your work bowl we install a new separation unit consisting mainly of the separation flap and its actuation mechanism (manual or pneumatic).
  • The completed replacement work bowl is dispatched to you. And as soon as it arrives at your site, you return the old bowl with the worn lining to us.
  • The old work bowl is now inspected, repaired (if required) and placed in our replacement work bowl pool for the next customer. 


When all attachments have been removed from the work bowl, it undergoes the following steps:

  • Thermal stripping of the lining
  • Shot blasting
  • Placement of a primer on the outer bowl surface
  • Placement of an adhesion coating with a pre-defined thickness on the inner bowl surface

At this stage, smaller faults in the steel structure which were previously covered by the protective lining become visible. All these faults are carefully repaired.

Please read in the following sections which additional repairs may become necessary.



Once Quality Control has approved the old work bowl for re-use in the replacement bowl program, the unit is transferred to our repair shop for disassembly. Frequently, during the removal of the bowl attachments, further damage to the work bowl structure is detected.

For example, the bearing seat and bearing of the separation flap might be totally worn or, in some instances, the lining has peeled from the steel wall forming a cavity in which work pieces have been trapped. In many cases the media/work piece separation section of the work bowl has suffered serious damage.



After the lining has been stripped from the work bowl, the bowl is returned to the repair shop where the group leader – jointly with Quality Control – determines which repairs must be made.

The defective separation flap bearing seat and bearing are replaced, and any damage on the steel structure is professionally welded. Of course, after these welding repairs a new adhesion coating is applied in the affected areas. The work bowl is now ready to receive a new protective lining.


All welding seams on our work bowls are carefully prepared, and the welding work is professionally executed. This helps to prevent any premature failures due to sloppy welding. Over time the constant vibratory force to which our work bowls are exposed can cause micro cracks in the critical welding areas. Our rule of thumb: Even with one third of the welding seams having suffered some kind of damage, the overall operational characteristics of our machines should not be affected!

The professional repair of all these hidden faults ensures that our replacement work bowls are in a condition, as if they were brand new. If the repair of a returned work bowl is deemed unfeasible, it is scrapped, and a new work bowl is added to the replacement bowl pool without the customer ever becoming aware of this. From the customer’s viewpoint his TROWAL machine has practically an infinite life expectation.



After the welding repairs are completed, the work bowl is transferred to our PU department for the following operations:

  • Placement of a specially designed steel mold into the work bowl. A steel mold usually consists of multiple segments.
  • Heating of the bowl and the mold in a dedicated tempering oven.
  • Filling of the cavity between inner work bowl surface and steel mold with a highly wear resistant liquid more-component polyurethane mixture.
  • Tempering of the lining in the oven at a pre-defined temperature range to ensure the optimum chemical reaction, i.e. bonding, between the polyurethane components.
  • Cooling of the work bowl to room temperature and subsequent removal of the steel mold.
  • Dressing of the finished lining by mechanical removal of all polyurethane flashes.

Now the lined work bowl is ready for assembly, i.e. remounting of all work bowl attachments.


After the work bowl has received a new protective lining, it is returned to the repair shop for mounting of the media/work piece separation unit and fitting of any other attachments. All adjustments and minor repairs are made prior to painting.

First, the separation flap with shaft and bearing is installed. Of course, for this operation only new parts are utilized. Subsequently, the separation flap, also made from polyurethane, is ground to ensure a precise fit into the work bowl processing channel. This is absolutely essential to prevent undersize media, small media or small work pieces from lodging in the gap between separation flap and processing channel. Such lodgings can cause major damage to the flap and lining, whenever the separation flap is operated. This is an important detail that significantly affects the overall life of the protective lining. Finally, the refurbished screening section and the new separation flap mechanism (the picture shows a pneumatic flap mechanism) are carefully mounted and precisely calibrated.


Prior to painting all the work bowl attachments must be removed again. The actual painting takes place in our in-house paint shop. For paint preparation the work bowl surface is completely sanded and coated with a primer. Then it receives the final paint, of course, in the color of your choice.



After painting the work bowl is transferred to our repair shop for one last time. The work bowl attachments removed for painting are re-installed. Now the work bowl is ready for mounting of the vibratory motor or imbalance unit. If you want to do this operation at your end, we will provide detailed mounting instructions. However, to prevent problems with the restart of your TROWAL machine due to improper mounting of the vibratory motor or imbalance unit, we recommend having this critical work done by a trained TROWAL service engineer. 

Please note: With some machine types the work bowl must be turned upside down to mount the vibratory motor or imbalance unit. If you do not have adequate lifting equipment at your premises, we prefer mounting of the vibratory motor/imbalance unit to the work bowl at our facility. We can do this work for you within 24 hours.



Another extremely important work operation for each replacement work bowl is the preparation of the mounting flange for the vibratory motor/imbalance unit.

The mounting flange on the work bowl must be absolutely level. For this reason, it is carefully cleaned, ground and, upon technical review, must even undergo a precision machining (turning) operation.

Only an absolutely level mounting flange – in combination with a special sealant – guarantees a safe and consistent transfer of the vibratory energy to the work bowl. Omission of this important work operation will cause shearing of the mounting bolts or even ripping off of the mounting flange after just a few hours of operation. This can have disastrous consequences in the form of a cracked work bowl and a destroyed vibratory motor/imbalance unit usually resulting in a total loss of the machine.



A replacement bowl from WALTHER TROWAL offers you the following benefits:

  • You receive a professionally repaired unit that has undergone strict quality inspections and is like new.
  • Your replacement bowl contains a brand new, highly wear resistant polyurethane lining that has been placed with state-of-the art processing equipment.
  • Depending on the specifications of your machine, it will be equipped with a new separation unit consisting of separation flap and flap actuation mechanism that has been carefully installed and calibrated.

To bring it to the point: Your replacement bowl offers the quality of a brand-new unit. And to prove that we mean what we say, the steel fabrication and lining are covered with our 12-month new machine TROWAL warranty.



Using the perfect combination of machine, abrasive media and compounds, we can attune the mass finishing process to ensure that your workpieces have the surface you require.

Blast Finishing


Using the perfect combination of machine, abrasive media and compounds, we can attune the mass finishing process to ensure that your workpieces have the surface you require.

Small Part Coating


Using the perfect combination of machine, abrasive media and compounds, we can attune the mass finishing process to ensure that your workpieces have the surface you require.

Test Lab Service Requests


Are you looking for the perfect way to process or coat your workpieces? We will be happy to support you here with our expert knowledge. Based on your workpieces and a special question sheet, we can develop the right processing system in our test labs.