What a Pump Element Does
A pump element is the replaceable metering unit that screws into the port face of a centralized grease pump. Inside each element, a piston moves in a close-fitting bore. On the pump pressure stroke, the piston pushes one fixed volume of grease through the outlet toward a single lubrication point. When pump pressure drops, an internal spring returns the piston so the bore refills and the element is ready for the next cycle.
Because each element meters independently, one pump body can feed several points at different doses from a single drive. The element thread, the stroke volume options, and the spring-return working principle are covered on this page; the pumps themselves and the system architecture around them are covered in our guides to how a central lubrication system works and industrial lubrication pumps.
Specifications
The table lists the fixed data for this element. Stroke volume is selected per element when the pump is configured.
| Parameter | Value |
|---|---|
| Mounting thread | M18 x 1.5 male |
| Stroke volume options | 5, 10, 15, or 25 mm3 per stroke |
| Maximum working pressure at the element | 350 bar |
| Operating temperature | -20°C to +50°C |
| Reference tightening torque | 30 Nm |
| Body | Zinc-plated steel |
| Lubricant | Grease up to NLGI 2, including semi-fluid NLGI 000 and 00; oil use, confirm when ordering |
Choosing the Stroke Volume
Sizing starts from the dose each point needs and the number of points the pump serves. Multiply the required dose per point by the number of points in the round, then divide by the stroke volume. The result is the number of pump cycles the pump must run for one lubrication round.
The division rarely lands on a clean figure, so pick the stroke volume that brings the cycle count into the range the pump setup allows. Doubling the stroke volume halves the cycles per round; moving to a smaller volume gives finer control where a point needs a light dose. Elements with different volumes can be mixed on one pump body, so a heavy bearing row and a light guide row do not share one setting.
The SDRB-N heavy-duty electric grease pump is one host platform for this element style; see the SDRB-N product page for pump-side details. If the sizing division leaves no workable combination, contact us for a quote and state the dose per point and the point count.
Per Stroke vs Per Cycle
Two figures are often confused here. Per stroke is the dose one element meters during a single movement of its piston: 5, 10, 15, or 25 mm3, depending on the element fitted. Per cycle is one pressurization of the pump, which drives every element on the port face in the same pass. A cycle therefore meters the combined stroke volumes of all fitted elements, not a single volume alone.
A lubrication round is not the same as one cycle. Several pump cycles may be needed before all points are served, because the sizing division sets the cycle count for the round. When you read output figures on a grease pump page, check whether the figure is per stroke, per cycle, or per round, and convert using the fitted elements before comparing two systems.
Installation and Torque
Thread the element into the pump port by hand until the thread engages cleanly, then tighten to the 30 Nm reference tightening torque. Do not over-tighten; the M18 x 1.5 thread seats firmly at the reference value, and excess torque can distort the seat. Keep the element aligned with the port while starting the thread so it does not cross-thread.
To order a spare, read the stroke volume marking on the element body and confirm that marking against the pump documentation. If the marking has worn away, measure the delivered volume on a bench run before selecting a replacement. For the fitting and connector patterns used downstream of the element, see the grease fitting types guide.
Grease Grades and Cold Pumpability
The element is rated for grease up to NLGI 2, including the semi-fluid NLGI 000 and 00 grades. On the NLGI scale, 000 is the softest grade and each higher number is stiffer, so semi-fluid grades flow through the small metering bore with the least resistance. NLGI 2 stays within the rating but asks more from the pump near the cold end of the -20°C to +50°C range.
For cold service, a semi-fluid grade keeps the stroke volume consistent because the pump works against lower flow resistance near -20°C. For oil service, the published rating does not apply; confirm oil details and confirm seal compatibility with the fluid data sheet before ordering.
Frequently Asked Questions
What is a pump element?
A pump element is the replaceable metering unit that screws into a centralized grease pump. Inside, a piston meters one fixed volume on each pressure stroke, and a spring returns the piston for the next cycle.
Which stroke volume should I choose?
Multiply the required dose per point by the number of points, then divide by the stroke volume to get cycles per round. Choose 5, 10, 15, or 25 mm3 per stroke based on that division.
Is output rated per stroke or per cycle?
Stroke volume is the fixed dose one element meters during a single pressure stroke. One pump cycle drives each element once, and several cycles may be needed to serve all points.
What does the 350 bar figure mean?
350 bar is the maximum working pressure at the element outlet. It does not rate the pump, the lines, or the fittings; those parts follow their own limits.
Which grease grades can it handle?
It accepts grease up to NLGI 2, including semi-fluid NLGI 000 and 00 grades. Semi-fluid grades pump easiest; NLGI 2 needs care near the cold end of the range.
Can this element run oil?
The published rating covers grease up to NLGI 2. For oil service, confirm oil details and seal compatibility with the fluid data sheet before ordering.
What torque should I use to install it?
Use the 30 Nm reference tightening torque for the M18 x 1.5 thread. Do not over-tighten; stop when the element seats firmly.
How do I identify the correct spare element?
Read the stroke volume marking on the element body before removal. Confirm that marking against the pump documentation when ordering the spare.
When does an element need replacement?
Replace an element when one lubrication point consistently under-feeds while the other points feed normally. Swap the suspect element, re-test the point, and contact us for a quote on a matching spare.
Who builds and supports this element?
IsoHiTech Lubrication Systems, founded in 2023, engineering since 2006, builds and supports every unit. Email inquiry@isohitech.com for specifications and a quotation.
