TGO511 Oil Filter (Kaeser 634641, 634641/A Equivalent) for Kaeser M70 Screw Compressor

1. Purpose and Operating Principle

The filter is installed in the oil circuit of the screw airend and performs three functions:

• removes mechanical contaminants and wear particles from circulating oil;
• protects the screw rotors and bearings from abrasive wear;
• thanks to a built-in bypass valve, ensures oil supply to compressor components even under severe filter element clogging, preventing oil starvation.

2. Technical Specifications

3. Design Features

1. Italian manufacturing by TGfilter. The brand specializes in filter elements for industrial compressor equipment, confirmed by a wide range of similar models (TGO205, TGO255, TGO300, and others).
2. Built-in bypass valve (Y). In the event of critical clogging of the filter media, the valve opens and allows oil to bypass the element, guaranteeing continuous lubrication of the screw rotors even in an abnormal situation — an important safeguard against oil starvation.
3. Absence of anti-drain valve (N). After the compressor stops, oil drains from the filter housing back into the oil sump. This is a normal design feature of this model, not a defect — on the next startup, circuit pressure is restored in the standard manner through the operation of the screw airend and the oil separator.
4. One-piece, non-disassemblable housing. The spin-on design eliminates leaks at joints and simplifies replacement — no separate housing gasket is required.
5. Standardized M24×1.5 thread. Ensures compatibility with the mounting seats of a wide range of screw airends using this connection standard.

4. Installation Recommendations

• Lubricate the rubber gasket with fresh compressor oil before installation — a dry gasket can twist or deform during tightening, leading to leaks.
• Pre-fill the filter with oil before installation, if the mounting orientation allows — this reduces the time needed for the compressor to reach working oil pressure at first startup after replacement.
• Screw the filter on by hand until the gasket contacts the sealing surface, then tighten an additional 3/4–1 turn — do not use a strap or chain wrench for final tightening, as this can deform the housing.
• Do not exceed the recommended tightening torque — excessive force damages the M24×1.5 thread and the sealing surface.
• After starting the compressor, check the filter seat for leaks during the first few minutes of operation under load.
• Note the absence of an anti-drain valve: after a prolonged shutdown, the filter housing may be empty — this is not a malfunction and requires no special action during a standard screw compressor startup.

5. Analogues and Comparison

The TGO511 is a direct equivalent of the original Kaeser 634641 oil filter (part number 634641/A), used on Kaeser M70 series screw compressors. In connection thread (M24×1.5), dimensions (A93/H210), and functionality (built-in bypass valve), the TGO511 is fully interchangeable with the Kaeser original.

Besides the Kaeser original, the TGO511 is comparable in connection thread and size to spin-on oil filters from other manufacturers, including Mann Filter, Donaldson, and SotrasFiltec lines.

When selecting an equivalent, always verify:

• the original Kaeser 634641 / 634641/A part number — this is the primary reference for a fast and accurate replacement;
• the connection thread (M24×1.5) and housing height (210 mm), so the filter does not interfere with neighboring airend components;
• the presence/absence of a bypass valve and its opening pressure;
• the presence/absence of an anti-drain valve — if your compressor’s original filter had an anti-drain valve and you install a TGO511 without one, this is not critical for operation but is worth knowing about.

If you are selecting a replacement for a specific compressor serial number and want to confirm the exact match for your Kaeser M70 configuration, send us the markings from the removed filter — we’ll verify compatibility before shipping.

6. Common Installation Mistakes

• Tightening with a strap wrench “to the max” — deforms the filter’s thin-walled housing and damages the threaded connection.
• Installing without lubricating the gasket — causes it to twist and leads to subsequent oil leaks.
• Reusing the old gasket “just in case” along with the new filter — creates a double seal and leakage.
• Skipping the leak check after first startup — a small leak at startup is easy to fix but goes unnoticed without inspection.
• Expecting a “full” filter at every startup — due to the absence of an anti-drain valve, this is normal and not a reason for re-tightening or removal.

7. Practical Applications

TGO series oil filters are used in the following areas:

• Industrial compressor stations — on Kaeser screw airends and compatible models.
• Food production — compressor installations for packaging lines requiring stable oil filtration.
• Woodworking and metalworking — powering pneumatic systems for machines and tools via screw compressors.
• Compressor equipment service centers — as a consumable for scheduled maintenance.
• Construction and mobile compressor units — with a matching connection size.

8. Expert Opinion

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

“The TGO511 is a quality alternative to original Kaeser filters at a reasonable price. I want to draw customers’ attention to one feature: this model has no anti-drain valve, so after the compressor stops, oil in the filter housing drains back into the sump — this is normal and doesn’t indicate a fault. The main rule when replacing it is not to let the rubber gasket dry out and not to torque the filter down with a wrench: the spin-on housing has thin walls and deforms easily. I recommend replacing the filter along with scheduled oil changes — this is the standard interval for most screw airends in this class.”

9. Frequently Asked Questions

1. Which original Kaeser part number does the TGO511 correspond to? The TGO511 is the equivalent of the original Kaeser 634641 oil filter (part number 634641/A), used on Kaeser M70 series screw compressors.

2. Does the TGO511 fit my specific Kaeser M70 model? If you already have a filter marked 634641 or 634641/A installed, the TGO511 fits directly. If in doubt, send us the markings from the removed filter or the compressor’s serial number — we’ll confirm the exact match before you order.

3. Why is there no oil in the filter after a long compressor shutdown? This is a design feature — the TGO511 has no anti-drain valve, so oil drains back into the sump after shutdown. This is not a malfunction and requires no special action at startup.

4. Should I fill the filter with oil before installation? It’s recommended if the mounting orientation allows — this speeds up reaching working oil pressure, but it’s not a mandatory condition for correct operation.

5. What torque should I use when installing — is a torque wrench required? For spin-on filters, hand-tightening until the gasket makes contact plus an additional 3/4–1 turn is usually sufficient. Using a wrench with excessive force damages the thin-walled housing — a torque wrench isn’t mandatory, but avoiding over-tightening is essential.

6. How often should the TGO511 oil filter be replaced? The replacement interval is tied to your compressor’s oil change schedule — typically every 2,000–4,000 operating hours or at scheduled oil changes, depending on operating conditions and oil quality.

7. What happens if I install a filter without a bypass valve instead of the TGO511? Without a bypass valve, severe clogging of the filter element can restrict oil supply to compressor components, increasing the risk of oil starvation. The TGO511 comes standard with a bypass valve (Y) specifically to prevent this situation.