Crankcase for FL-24 Piston Compressor (MZB, 1.3 kW, 24 L receiver)

1. Purpose and operating principle

The FL-24 is an oil-lubricated, direct-drive (beltless) piston compressor made by MZB Compressor: 1.3 kW motor, 24 L receiver, 8 bar, 220 V. Oil lubrication of the piston group is the standard design of this line, so crankcase tightness and oil sump cleanliness directly affect pump life. The crankcase is replaced if the housing is cracked, the bearing seats or the flange are damaged, or oil leaks through the housing and sealing repairs no longer help.

2. Technical specifications

Confirmed data for the compressor this part is intended for (per the FL-24 product page on acvatron.md):

3. Design features

Compressor designation breakdown:

The receiver volume only defines the tank size, not the pump design, so a crankcase cannot be selected by the number “24” without checking dimensions.

What the crankcase should include and provide (the presence of each element on the specific part ⚠️ must be checked):

• a sealed oil cavity with a filler opening and an oil level indication (dipstick, sight glass or mark);
• seats for the crankshaft bearings and a flange for mounting the cylinder;
• a flange or fixing points for connection to the motor (direct-drive layout);
• faces for gaskets and covers, a breather or an opening connecting the crankcase cavity to the atmosphere.

4. Installation recommendations

• Drain the oil and inspect the assembly. Before replacing the crankcase, check the crankshaft, connecting rod, bearings and piston group for wear and scoring: a new crankcase with a worn mechanism will not last long.
• Clean the mating surfaces of old sealant, metal chips and oil film; there must be no nicks or deep scratches on the faces.
• Replace gaskets and seals with new ones. Reusing old gaskets is the main cause of leaks after repair.
• Bolt tightening torque — per the pump manufacturer’s data ⚠️ (not confirmed). Tighten in a crisscross pattern, evenly, without overtightening: threads in the housing strip easily.
• Fill with fresh oil to the mark and turn the shaft by hand before starting to make sure it does not seize.
• Break-in. After repair, follow the schedule given for the FL-24: first oil change after 50 h of operation, then every 200–300 h. Do not run the compressor below +5 °C.

5. Alternatives and comparison

There are no verified part numbers for an equivalent crankcase for the FL-24, so no cross-reference list is given — compatibility cannot be invented. Selection is made by dimensions and design:

FL-24 and FL-40 belong to the same MZB line (per the product pages on the site: 1.3 and 1.5 kW motors respectively), but the crankcases of these models should not be considered interchangeable without checking dimensions ⚠️. The best way to select the part is to bring or send a photo of the old crankcase with its dimensions and the compressor nameplate.

6. Common mistakes

1. Selecting by receiver volume. People order a “crankcase for a 24 L compressor” without checking dimensions: compressors of this capacity from different brands have different pumps and different motor power.
2. Fitting a new crankcase on a worn mechanism. Bearing play or scoring on the cylinder quickly destroys the new part too.
3. Old gaskets and uncleaned faces. After assembly oil leaks at the joint, and contamination gets into the sump.
4. Overtightening bolts in the aluminum housing. Threads strip and cracks appear around the mounting points.
5. Skipping the oil change after break-in (50 h). Break-in metal particles stay in the sump and accelerate wear of the bearings and piston group.
6. Starting below +5 °C. Thickened oil reaches the friction pairs poorly during a cold start.

7. Applications

• Repair and maintenance of the oil-lubricated direct-drive piston compressor FL-24 (MZB Compressor).
• Restoring the pump after a cracked housing, oil leaking through the housing, or damaged bearing seats.
• Service workshops, garages and home workshops where the FL-24 is the main source of compressed air.

8. Expert opinion

“On a compressor like this the crankcase is replaced less often than the valves, rings or pressure switch, so first determine what has actually failed. If oil leaks at the joint, new gaskets and clean faces are often enough. A new crankcase is needed for a crack or ruined seats. Select by dimensions and the compressor nameplate, not by receiver volume, and don’t skimp on break-in: the first oil change after 50 hours of operation must not be skipped.”

Vitali Boluchevski, Lead Engineer, Acvatron SRL, 18 years of experience

9. FAQ

1. How do I know the FL-24 crankcase needs replacing? Signs: a cracked housing, a constant oil leak that new gaskets and seals do not cure, ruined bearing seats and knocking from the lower part of the pump. Before replacing it, inspect the crankshaft, connecting rod and bearings.

2. How do I select a crankcase for the FL-24? By dimensions: bearing seat diameters, cylinder position, motor flange, position of the filler opening and drain. Send a manager a photo of the old crankcase, its measurements and the compressor nameplate.

3. Will a crankcase from another 24 L compressor fit? Not without checking dimensions. The same receiver volume does not mean the same pump: compressors from different brands differ in motor, cylinder and flange.

4. Do I need new gaskets when replacing the crankcase? Yes, replace them without fail. Old gaskets are the main cause of oil leaks after repair.

5. When should I change the oil after fitting a new crankcase? For the FL-24: first oil change after 50 hours of break-in, then every 200–300 hours or at least once a year.