LB50/LB75 Compressor Valve Plate Gasket (Ø80 mm)

1. Purpose and operating principle

The gasket seals the flat joint between two machined metal surfaces (the valve plate and the cylinder head) under the pressure of the compressed air. It separates the intake and discharge chambers according to the layout of the valve plate ports, preventing air from passing between them, and stops compressed air from leaking out through the fastening holes around the perimeter.

2. Technical specifications

The exact material grade (type of paronite or its asbestos-free equivalent) is usually not stated by the manufacturer in public sources — the part is supplied as a universal gasket of this size class, matching the mounting dimensions of the corresponding valve plate. Before ordering, we recommend comparing the gasket visually with the old one.

3. Design features

• Separation of intake and discharge zones. The gasket follows the pattern of the valve plate ports and physically separates the two zones; during installation it is important to keep the correct orientation so that the web does not block the working ports.
• Fastening holes around the perimeter match the standard cylinder head bolt layout of pumps of this size class (Ø80 mm).
• Thin fibrous material sits tightly against both mating surfaces under the clamping force of the head bolts and compensates for minor machining irregularities, but it is not designed for significant surface defects (scoring, warping).
• Single use. Like most flat fibrous gaskets, the part deforms (compresses) at the first tightening and loses its sealing properties if reinstalled.

4. Installation recommendations

• Never reuse the gasket. After the cylinder head has been removed, the old gasket loses its elasticity and will not seal, even if it looks intact.
• Check the flatness of the mating surfaces. Minor scoring on the valve plate or cylinder head can be removed by light lapping on a flat plate with abrasive; if there is noticeable warping, a new gasket alone is not enough.
• Tighten the head bolts in a criss-cross (diagonal) pattern, not in a circle — this distributes the force evenly across the whole gasket area.
• Do not apply sealant unnecessarily. A fibrous gasket is designed for direct sealing; excess sealant can get into the internal ports of the valve plate.
• Observe the gasket orientation — it must line up exactly with the valve plate ports.
• Re-check the tightness after a short run-in. In the first hours of operation the material may settle slightly; re-tighten the bolts with the compressor cold and no pressure in the system.

5. Equivalents and comparison

The LB50 and LB75 designations are found at different manufacturers of belt-driven piston compressors (including Remeza AirCast and other brands on a similar platform), so this is not an exclusive part of one brand but a gasket of this size class.

Before ordering, we recommend:

• comparing the new gasket visually with the old one — shape, size and position of the fastening holes — rather than relying on the compressor name alone;
• if in doubt, sending the Acvatron manager a photo of the old gasket — on visually similar valve plates from different factories the configuration may differ slightly;
• when replacing the gasket, inspecting the valve reeds right away: if they are worn, it is better to replace them together with the gasket so you do not have to take the head apart a second time.

6. Common ordering and installation mistakes

• Reusing the old gasket “for now” — practically guarantees an air leak at the joint on the very first start.
• Trying to fix a leak by overtightening the bolts — warps the valve plate and cylinder head and worsens the fit at the next replacement.
• Tightening the bolts in a circle instead of criss-cross — leads to uneven clamping and local leaks.
• Ordering by model name only, without visually checking against the old gasket — with the shared LB50/LB75 designation, small differences between manufacturers are possible.
• Installing in the wrong orientation — blocking a working port disrupts the operation of the valve group.

7. Areas of application

The gasket is used in the maintenance and repair of belt-driven piston compressors with LB50/LB75 pumps. For example, the СБ4/C-270 LB50 compressor (AirCast) delivers 550 l/min at 10 bar with a power of 4 kW. Such units are common:

• in car repair shops and service stations;
• in carpentry and metalworking workshops;
• in small production facilities and construction — as stationary and mobile compressed air sources.

8. Expert opinion

Vitaly Boluchevski, Lead Engineer at Acvatron SRL (18 years of experience):

“LB50 and LB75 are the general names of piston pumps found at several manufacturers of belt-driven compressors. That is why, when ordering a valve plate gasket, I always advise comparing the new part with the old one visually — by shape and hole layout — rather than relying only on the name on the nameplate. And most importantly: saving money on the gasket usually ends up costing more. If, after disassembly, you put the old, already compressed gasket back, the compressor will lose output because of the air leak at the joint, and the head will have to come off again within a few days.”

9. Frequently asked questions

How can I tell that the valve plate gasket has failed? The main sign is compressed air hissing around the joint between the valve plate and the cylinder head while the compressor is running, a noticeable drop in output, and a longer time to reach working pressure in the receiver.

Does the gasket fit both LB50 and LB75? The gasket is designed for LB50/LB75 pumps with an 80 mm cylinder bore. To be safe, compare it visually with the old gasket before ordering, or send us a photo.

Can I reuse the gasket after cleaning the valves? No. A fibrous gasket deforms at the first tightening and will not seal when reinstalled — it must be replaced with a new one every time the head is taken off.

Should sealant be used together with the gasket? As a rule, no: the material is designed to seal the joint on its own under the clamping force of the bolts. Excess sealant can get into the internal ports of the valve plate.

10. Contacts

Acvatron SRL Republic of Moldova, Chișinău, 12 Sarmizegetusa St., office 129 Phone: +373 22 503-580, +373 22 69605720 Email: acvatron@gmail.com Opening hours: Mon–Fri 09:00–17:00, Sat 09:00–13:00, Sun — closed

11. Order in Moldova

Is your compressor hissing at the head joint or taking longer to build pressure? Often the cause is a worn valve plate gasket. A new gasket for LB50/LB75 pumps (Ø80 mm) will restore the joint’s seal and the compressor’s output.