D-Series
Heavy Duty Rod Scrapers
Maximum scraping potential for extreme environments
Designed for use in especially tough applications and in particular, where the adhesive bond between contaminant and rod surface is strong. The wider and deeper cross-section of D-Series wipers allows for the addition of an o-ring to seal the OD plus a heavy-duty stainless steel spring. The groove size and breakout friction constraints placed on the designs of other scraper specifications, are ignored in this aggressive and rugged design resulting in a "no-holds-barred" solution to tough contaminants. D-Series wipers are available in ductile copper alloys and Stainless Steel alloys for sizes from 20mm to 250mm (smaller, larger and in-between sizes available upon request).
Style-I
The large cross-section provides more resistance to the forces generated by contaminants presenting at the interface of the lip on the scraper body, and the surface of the rod. These forces are inclined to "lift" the scraper body away from the rod surface, undermining the action of the scraper. The heavier body provides greater resistance to these lifting forces by permitting the use of a heavier serpentine spring, generating more clamping load to further resist the over-ride of strongly bonded (adhered) contaminants. These forces are surprisingly large in magnitude and a combination of body rigidity, spring loading, interference with the gland, generated through the compressed O-ring, all contribute to overcome such forces.
Style-II
Style II D-Series metal scrapers contain a high load serpentine spring, paired with an O-ring that protrudes approximately 0.02" beyond the OD of the scraper body to seal against the gland and prevent an outer ingression path. The combination of spring loading and o-ring compression (interference) results in the highest performing scraper design.
Style-S
The Style-S D-series scraper contains a slotted heel to provide a path of egress for contaminants that bypass the scraper and accumulate between the scraper and wiper. The slot allows fine contaminant particles to flow over the lip of the wiper to a void between the face of the wiper and back of the scraper. Further consideration should be given by the Designer, to the further accumulation of these particles.
Style-L
This wiper contains a larger cross-section o-ring which is designed to create sufficient interference against a standard lip at the aperture of the retaining groove (counter-bore) so as to permit snap-in installation. The lip is recommended to be 0.031" (0.062" dia) with a minimum of 0.050" height.
DIMENSIONS
Style I shown above - dimensions apply to all styles.
D-Series Rod Scrapers are available for rod sizes up to and beyond 13" (310mm) dia. The following is a partial list of part/groove dimensions. For a more complete list, or for specific parts, please contact us.
Rod Compatibility & Testing for D-Series Scrapers
The following are general guidelines and are not intended to supersede information gathered from application and equipment specific testing.
Gadjets recommends testing of all exclusion seals, in the actual environment, on the actual equipment, prior to placing into service. The performance of a rod scraper or metal wiper depends very much upon present environmental factors, the method of installation and retention including considerations such as the clearances provided, especially to protect against bearing of sideload and shock loads, the presence or absence of a cohesive oil film on the surface of the rod/sleeve, as well as the condition and functioning of any adjacent seals. It depends on the condition of the rod, the nature and type of contaminants and other environmental factors such as temperature, pressure, moisture and atmosphere.
Some general recommendations based on field observation include:
Rod scrapers can be expected to work best on relatively hard rod surfaces, including hard chromed and nitrided rods etc.
For copper alloy scrapers, a hardness of 60+ (Rockwell C scale) is recommended.
For Stainless Steel scrapers, a hardness of 70+ (Rockwell C scale) is recommended. Stainless Steel does have a propensity to gall if paired with materials similar in crystalline structure, (especially other Stainless Steels) or on poorer finishes or softer coatings.
Recommended surface finish range is 0.1 to 0.3 μm Ra (4-12 μin Ra), ideally, honed or burnished rod stock - less than 0.1μm Ra) (4 μin Ra).
For the first few cycles of the scraper assembly on a super-finished rod, linear (axial) witness marks are likely to be observed on the surface of the rod, sometimes appearing as "scratches". Typically witness marks will "polish out" as a result of the scraper acting on the rod during the first few hundred cycles and should not impact the performance of seals.