Disc Centrifuge Parts Glossary | Dolphin Centrifuge

A bowl disc is a conical-shaped plate inside the rotating bowl assembly of the disc centrifuge. A stack of these discs is the heart of disc-type industrial centrifuges.

The purpose of these discs is to increase the surface area of settling available to the rotating fluids inside the bowl. This added surface area increases the efficiency of the centrifuge multi-fold. In other words, the discs reduce the settling distance of the process liquid. The photo shows a complete disc stack from an Alfa Laval centrifuge bowl.

The inter-disc spacing is maintained using caulks (or ribs), which are thin strips of steel welded to the discs' surface. These caulks are radially oriented and uniformly spaced around each bowl disc surface. The radial orientation of the caulks allows the flow of the process fluid in the same direction.

There are evenly spaced and matching holes on all the discs in a stack. These holes form a channel allowing upward movement of the process fluid through the disc stack. Depending on the centrifuge, these holes are closer to the outer periphery of the inner edge of the discs.

Another variation between discs is the caulk thickness, which varies the inter-disc spacing. For thicker or more viscous fluids, the caulks are thinner. This implies that the discs are closer to each other. The caulks are thicker for less viscous fluids (like water), allowing a wider gap between the discs.

The number of discs in a stack varies by centrifuge model and application. A larger stack means more separation surface area and typically higher throughput capacity. Bowl discs are precision-stamped from stainless steel and must be free of warping, deformation, or scale buildup to maintain proper separation performance. When reassembling a bowl, the discs must be re-stacked in the correct orientation with the caulks aligned to maintain the designed flow path through the stack.

The bowl of a disc centrifuge is the outer, rotating body that houses all the bowl assembly components. Bowl bodies rotate upwards of 5000 RPM up to 15,000 RPM.

Depending on the type of centrifuge, the bowl body may have slots around the periphery in the 'self-cleaning' centrifuges. These slots or ports are openings for the sludge to exit the bowl during the sludge ejection process. These sludge discharge ports can wear out based on the type of solids, especially in the case of abrasive particles.

Manual clean centrifuges have a solids bowl body without any slots or ports.

The bowl body is precision-machined from high-grade stainless steel or duplex steel to withstand the extreme centrifugal stress during operation. The bowl body must be periodically inspected for erosion, cracks, or corrosion, particularly around the sludge port openings. Any compromise in the structural integrity of the bowl body is a serious safety concern at the operating speeds of these machines. The internal water passages within the bowl body are also subject to scale buildup from hard water and should be cleaned during each scheduled overhaul.

The bowl hood is the upper cover on the centrifuge bowl body. Once assembled with the bowl body, this forms the complete outer envelope of the rotating bowl assembly. The bowl body is assembled on the upper end of the bowl spindle.

The large lock ring integrates the bowl hood into the bowl body.

The bowl hood houses several critical components including the gravity disc seat, the nylon seal ring groove, and the upper passages for the separated liquid phases. In a three-phase (liquid-liquid-solid) centrifuge, the bowl hood contains both the light-phase and heavy-phase exit passages. The hood must be inspected during overhaul for wear at the seal ring groove, as an eroded groove will not retain the nylon seal ring correctly, leading to bowl leaks during operation. The threads on the bowl hood that mate with the large lock ring are also a critical area — any damage here can make proper bowl assembly impossible.

The bowl spindle is the vertical transmission shaft of the disc centrifuge. It transmits the rotation from the gear train to the bowl assembly. The centrifuge bowl body is assembled on top of the bowl spindle.

The upper part of the bowl spindle has a precise taper section with a corresponding tapered hole in the bowl body. These tapers have to be precisely ground to match each other. Mating these two conical parts ensures complete surface contact between the bowl spindle and the bowl body. The friction between these components transmits the rotation from the spindle to the bowl assembly.

Therefore the bowl and spindle tapers need to match precisely for the smooth operation of the centrifuge. Any mismatch between the conical surfaces leads to the bowl mass being off-center from the rotating axis. At the operating speed of the bowl, this can cause imbalance and lead to excessive centrifuge vibrations.

Precision machined surfaces in the middle section of the bowl spindle for mounting the bearings.

The lower part of the bowl spindle has a worm gear mounted on it. In some smaller centrifuges, this gear is integral to the bowl spindle.

Bowl spindle runout is an essential checkpoint during disc centrifuge repair. Minor deviations in the spindle's straightness can occur over time, leading to a slight runout at the top of the shaft. The loss of concentricity leads to excessive centrifuge vibrations due to the rotating bowl mass being off-center. During overhaul, the spindle taper surface must be cleaned and inspected for fretting, corrosion, or mechanical damage. The taper surfaces of both the spindle and the bowl body should be lapped together periodically to ensure a precise fit. Any visible step, scoring, or galling on the taper surface is cause for replacement of the spindle or bowl body, as the imprecise contact will transfer to bowl vibration at operating speed.

The control paring disc is part of the operating water system of 'self-cleaning' centrifuges. It is a non-rotating part that functions as a water-conveying device. It transfers water from the stationary frame of the centrifuge to the rotating bowl assembly.

In a fully assembled centrifuge, the control paring disc is stationary and positioned within the underside of the rotating bowl body. It discharges the water in the form of a jet that enters the open cavity inside the rotating distributing ring (explained below). This mechanism allows the transfer of the operating water between the stationary and rotating parts of the bowl.

The precise alignment of the control paring disc jet with the opening of the distributing ring is critical. If the control paring disc is bent, clogged, or misaligned, the water transfer to the rotating bowl will be incomplete or imprecise, causing unreliable bowl opening and closing during the sludge ejection cycle. During every overhaul, the control paring disc should be inspected for blockage in its water passage and verified to be straight and undamaged. Even a minor bend can cause the water jet to miss the distributing ring opening, resulting in operational failures.

The distributing cone is part of the rotating bowl assembly. It is located within the bowl body above the sliding piston (described below).

The distributing cone distributes the incoming fluid smoothly within the underside of the distributor. The distributor is described in detail in the following section.

The geometry of the distributing cone is designed to redirect the incoming process fluid from an axial (downward) flow to a radial outward flow that can enter the disc stack through the holes in the distributor. This smooth redirection is important because turbulent introduction of the process fluid into the disc stack can disrupt the settled layers and degrade separation efficiency. Abrasive particles in the process fluid can erode the surface of the distributing cone over time. When significant erosion is observed, replacement is recommended to maintain proper flow distribution within the bowl.

A distributing cover is another component of the operating water system attached to the centrifuge frame underneath the bowl body. The bowl spindle passes through the distributing cover. The control paring disc (detailed above) mounts on the distributing cover.

This component 'covers' the frame opening below it — that's why the 'cover' is in its name. It is a conduit for the operating water and carries the water to the control paring disc. There are intricate passages within the distributing cover for water to flow through.

The internal passages can get clogged with sludge and mineral deposits from the water over time. Keeping the distributing cover clean from the inside is critical to ensure the centrifuge's trouble-free operation.

This is a critical part of the operating water system of the centrifuge. The functional aspect of this part is explained in our Bowl Troubleshooting article. During maintenance, the distributing cover should be removed and flushed thoroughly. In areas with hard water supply, scale buildup inside the cover passages is a common problem and can restrict the water flow needed for reliable bowl operation. Chemical descaling or mechanical cleaning of the passages is recommended at each scheduled overhaul.

The distributing ring is a rotating component that is a part of the centrifuge's operating water system. As referenced in the control paring disc section above, the distributing ring corresponds to the water transfer mechanism.

This part nestles within the bottom section of the rotating bowl body. It is fastened to the bowl body by bolts from within the bowl.

The jet of water from the control paring disc enters a precisely located opening on the inner diameter of the distributing ring. The centrifugal force radiates this water outwards into the water passage within the bowl body.

This is also a critical part of the operating water system of the centrifuge. The functional aspect of this part is explained in our Bowl Troubleshooting article. The small opening on the inner diameter of the distributing ring that receives the water jet from the control paring disc must remain clean and unobstructed. Mineral scale or sludge deposits can partially or fully block this opening, causing unreliable or absent bowl operation. This opening should be checked and cleared during every bowl service.

As the alternate name 'disc carrier' implies, the centrifuge distributor has mounted all the discs (stack). The distributor is the fixture for the conical plates within the centrifuge bowl. It aligns the cones correctly using an alignment key and corresponding slots on all discs.

The process fluid flows through the center of the distributor towards the distributing cone below it. The distributor has holes that line up with the holes in the discs. The process fluid passes through these holes into the disc stack.

The distributor features radial ribs around its core, which creates a gap between the discs' inner edge and the center of the distributor. The separated liquid flows through this gap upwards towards the bowl top.

The alignment key embedded in the distributor is a critical component. The distributor wears due to the constant flow of fluid with sludge along its surface. This wear can cause the discs to fit loosely around the ribs of the distributor.

Excessive wear can allow the discs to rotate about the distributor. This misalignment causes the holes on the distributor to not line up with those in the discs. The fluids can no longer flow in the designed passages leading to the malfunction of the centrifuge. During each overhaul, the distributor ribs and alignment key areas should be carefully inspected for wear. If the discs show any looseness or side play around the distributor ribs, the distributor must be replaced to restore correct disc alignment and flow distribution.

The gravity disc is a stamped steel part on top of the disc centrifuge bowl hood. The gravity disc has a controlled inside diameter hole, which controls the position of the interface between the two liquid phases in the case of a liquid-liquid separation centrifuge.

This interface is critical for the operation of the centrifuge. If the interface is too far radially outward (large gravity ring hole size), there is not enough heavy phase liquid in the bowl.

The inner oil column's hydrostatic pressure pushes out the water phase and exits the bowl through the heavy phase outlet. This condition is undesirable, as the lighter fluid (usually oil) is now exiting the bowl through the incorrect outlet. This is the 'break-over' condition discussed further down in this article.

A nomogram helps the operator select the correct gravity disc size for the process fluids. It uses the ratio of the specific gravities of the two liquids, the throughput volume, and process fluid temperature to determine the right gravity disc. Each Alfa Laval disc centrifuge model has a corresponding nomogram chart to go with it.

For purifier (three-phase) centrifuges — where the goal is to separate a small amount of water from a large volume of oil — a correctly sized gravity disc is one of the most important operating adjustments available to the operator. If the process fluid specific gravity changes (for example, if the oil type changes), the gravity disc size may need to be recalculated and changed. A set of gravity discs in incrementally different sizes is typically supplied with the centrifuge for this reason. The gravity disc also does not apply to clarifier (two-phase, liquid-solid) centrifuges, which do not have a second liquid phase outlet.

As the name suggests, this is a steel ring that locks the bowl hood to the bowl body. This ring has external threads with matching female threads in the bowl body.

The purpose of this ring is to compress the bowl hood to the bowl body. The compression of the bowl hood also compresses the other parts inside the rotating bowl assembly. This tightening squeezes all the bowl parts together, forming a rigid and integral bowl assembly.

One key aspect of this process is repeatedly impacting the lock ring tightening tool. The OEM recommends a heavy sledgehammer for this locking action. The lock ring and the bowl body have respective marks that need to be aligned to ensure complete tightening of the bowl.

The large lock ring is a safety-critical component. Since the bowl rotates at very high speed, any loosening of the lock ring during operation would be catastrophic. The alignment marks on the lock ring and bowl body must be confirmed at each bowl assembly before the centrifuge is placed back in service. The threads of the large lock ring should be inspected for damage, corrosion, or galling at each overhaul. Thread damage can make it impossible to fully tighten the bowl assembly, resulting in an unsafe and improperly assembled centrifuge. The OEM assembly manual tightening procedure must be followed precisely, including the required number of sledgehammer impacts on the tightening tool.

The sliding piston lip (described below) and the nylon seal ring form the primary seal in the self-cleaning centrifuge bowl. This seal ring fits into a groove in the bowl hood. Its location matches the location of the lip on the sliding piston.

The nylon seal ring is a consumable part. It is essential to periodically replace this part to prevent wear on the bowl's sliding piston (non-replaceable part). For more information, read our disc centrifuge bowl leak troubleshooting article.

During regular use of the centrifuge, the operator should regularly inspect the nylon seal ring to check for excess wear on the sealing surface.

The nylon seal ring is one of the most important consumable parts in a self-cleaning disc centrifuge from a cost-management perspective. The ring itself is inexpensive — typically a few dollars — while the sliding piston it protects can cost hundreds of dollars or more depending on the centrifuge model. When the nylon seal ring wears through, the piston lip begins to contact the bowl hood metal-to-metal. This accelerates wear of the piston lip rapidly. Once the piston lip is worn, the bowl will leak during operation, and the only solution is expensive piston replacement. By simply replacing the nylon seal ring on a regular maintenance schedule — or whenever a bowl leak is first observed — this costly scenario can be avoided entirely. Many experienced centrifuge operators replace the nylon seal ring at every bowl overhaul as a standard practice regardless of its visible condition.

The paring disc is a static impeller device that is internal to the bowl. Though this part is inside the bowl assembly, it does not rotate. It is suspended inside the upper chamber of the bowl, which revolves around it.

The paring disc is a centripetal pump, which converts the fluid's rotational energy inside the bowl into pressure. It performs this pumping action through internal spiral vanes.

This pump is threaded on the feed tube and connects to the upper fluid discharge assemblies.

The bowl cavity housing the paring disc has a tight tolerance. This close gap means that properly assembling these components is critical because the other parts close to the paring disc are rotating.

Any contact between this stationary part and the rotating parts can cause catastrophic damage to the centrifuge.

The back-pressure maintained on the paring disc outlet is a critical operating parameter. Without adequate back-pressure, the paring disc impeller vanes will not be sufficiently immersed in the separated liquid layer, reducing pumping efficiency and potentially allowing air to enter the liquid outlet, which degrades separation. Back-pressure also helps stabilize the liquid-liquid interface within the bowl. When adjusting or troubleshooting a disc centrifuge, the back-pressure setting on each liquid outlet should always be checked and confirmed to be within the OEM-specified range for the application. A separate article on centrifuge back-pressure provides detailed guidance on this topic.

The exposure of the sludge ejection ports in the bowl body to wear is a cause for concern.

Port liners are stamped steel clips that are crimped over the exposed sludge ports. They protect the centrifuge bowl body ports from wear.

The port liner is a sacrificial part that is easily replaced at a minimal cost.

During each sludge ejection cycle, the accumulated solids are discharged through the open sludge ports at extremely high velocity due to the centrifugal force within the bowl. This high-velocity discharge of solids — particularly when the solids are abrasive materials such as sand, scale, or metal fines — rapidly erodes the edges and surfaces of the port openings. Without port liners, the bowl body itself is damaged. Since the bowl body is a precision-machined, high-strength component, repairing or replacing it due to port erosion is expensive. Port liners absorb this wear and can be replaced at a fraction of the cost. Port liners should be inspected at every bowl overhaul and replaced when any significant thinning, cracking, or deformation is observed.

A brief introduction of the sliding piston is in the 'bowl liner' section above. This part is also known as the sliding bowl bottom because it slides downward at the bottom of the fluid chamber. The evacuation of the water below the piston causes the piston's downward movement.

This sliding motion of the piston opens the sludge discharge ports to the bowl's interior. The high centrifugal force exerted within the bowl pushes the accumulated solids instantly through these exposed ports. This action comprises the sludge ejection cycle of the self-cleaning centrifuge.

The sliding piston has another essential feature designed into it. A small circumferential protrusion, known as a lip, is machined onto the sliding piston's upper surface. This lip embeds into a mating part inserted into the bowl hood to form a seal. This seal keeps the bowl contents from exiting the bowl under the high centrifugal forces during regular operation.

It is essential to mention that erosion of the above-mentioned sliding-piston lip can cause the bowl contents to leak during operation. This leak can cause the separated solids to exit the bowl at a high velocity causing more wear on the lip. Therefore it is crucial to replace the nylon seal ring (explained above) to prevent wear of the sliding piston, which can be an expensive replacement.

Detailed information about Bowl Leaking and prevention is on our disc-centrifuge troubleshooting guide. The outer cylindrical surface of the sliding piston also slides within the inner bore of the bowl body. This mating surface must be clean and smooth. Any scoring, corrosion, or scale buildup on either the piston surface or the bowl bore will impede the piston's free movement, causing unreliable bowl operation. The sliding piston sealing surfaces — both the upper lip area and the outer cylinder — should be carefully inspected at each overhaul for any irregularity.

Sludge ports are rectangular slots machined on the disc centrifuge bowl body. As described in the port liner section above, these openings allow the separated solids to exit the bowl during the solids' ejection process.

Again, it is essential to protect these ports from wear by using port liners in abrasive sludge applications.

The number and size of sludge ports varies by centrifuge model and is designed to match the expected solids volume and ejection characteristics of the application. Larger ports allow higher volume sludge discharge, while smaller ports are used in applications with lower solids concentrations. The geometry of the port openings also affects how completely the sludge is discharged in each ejection cycle. Worn or eroded sludge ports may allow a partial discharge, leading to solids buildup within the bowl between cycles, which reduces separation efficiency and may cause imbalance. This is why port liner protection is so important — unprotected port erosion changes the port geometry and degrades performance over time.

The small lock ring is an internally threaded part that screws onto the top of the bowl hood. It secures the gravity disc to the bowl hood and houses a chamber for the heavy phase's paring disc pump.

The small lock ring serves a dual purpose: it retains the gravity disc in place on top of the bowl hood during high-speed rotation, and it creates an enclosed chamber where the heavy-phase paring disc pump operates. The heavy-phase separated liquid accumulates in this chamber before being pumped out under pressure by the paring disc. The thread engagement between the small lock ring and the bowl hood must be complete and correct — a partially engaged or cross-threaded small lock ring can unscrew during operation due to the centrifugal loading. The small lock ring also typically features a hexagonal or notched profile to allow tightening with a spanner wrench during bowl assembly. Its threads should be inspected for damage during each overhaul.