Kolbenstangen-Abstreifer

Wiper-scraper seals (alle Maße sind amerikanisch, nicht metrisch) (Oil Seal)

Wiper-scraper seals

Sealing dirt out of hydraulic cylinders and removing solid contaminants from the rod can be done effectively by one sealing device: the wiper-scraper-seal. This unique all-in-one seal works consistently, at a cost comparable to that of standard spring-loaded shaft seals.

Simple and compact in design, this wiper-scraper seal consists of a thin spring brass scraper and a pliable nitrile wiping member assembled in tandem position, securely clamped and enclosed in a steel shell. The seal´s inner diameter is slightly under shaft size. When assembled over the shaft or rod, it fits snugly. Designed for reciprocating shafts only, wiper-scrapers will not withstand pressure. In applications involving pressure, select a block vee packing.

Due to its high effective scraper action, these seals generate considerable drag. Designers shoul conduct functional tests to evaluate their performance in non-hydraulic cylinder applications.

Selection

Correct selection of this wiper-scraper seals depends on shaft diameter, cross-section and width dimensions.

Refer to the table below.

Shaft diameter	Radial cross-selection	Width
.500” (12.7 mm)	.250” (6.35 mm)	.250” (6.35 mm)
.625” - 3.000” (15.9 mm - 76.2b	.250” (6.35 mm)	.281” (7.14 mm)
3.125” - 5.250” (79.3 mm - 133 mm)	.313” (7.9 mm)	.328” (8.3 mm)
5.313” - 6.000€” (135 mm - 152 mm)	.313” (7.9 mm)	.359” (9.12 mm).

Operation

The scraper´s self-aligning feature not only accommodates rod eccentricity during assembly; it also permits the scraper to follow the rod´s side movement up to .020" (.5 mm) misalignment. The brass scraper lip fits snugly, removing dried or frozen mud, tar and other materials stuck to the rod on the inward stroke. The nitrile wiping member then removes any water, dust or abrasive particles which might pass by the scraper.

Recommended operation condition

The wiper-scraper seal should function adquately under the following conditions. Shaft diameter-Tolerance of plus or minus .001" (.03 mm) required to assure efficient scraping action, Shaft eccentricity-Accomodates up to .020" (.5 mm) misalignment.

Shaft finish-10-20 micro-inches Ra. Shaft hardness-Rockwell C30 minimum.

Shaft material-Steel or stainless steel. If chrome-plated, the entire surface should be plated. Shaft speed-Designed for reciprocating applications: not suitable for rotating shafts. No practical limit to speed of reciprocation. Pressure-Not designed to withstand pressure. Temperature- from -20 to 250 F (short peaks only) -29 to 121 C

Wiper-Scraper seal installation

The Wiper-Scraper seal is retained in steel housings by simple press-fit. It does not require special machining for snaps rings. To avoid restriction of the scraper´s floating feature. Our engineers recommend that the seal housing bore depth be machined .031" greater than the seal width and the seal installed flush with the face of the housing. Do not bottom out the seal.

Wiperseal

This double lip Wiperseal is designed for reciprocating rods. As a wiper, it excludes dirt and contaminants protecting the rod seal and internal components.

Applications

A molded elastomer part, this Wiperseal features dual opposed lips for dirt exclusion in an internal groove. Valuable in rod applications, it increases the packing life and protects the rod finish. This improved wiping performance extends internal component life and reduces maintenance.

Double lip rod Wiperseals are not recommended for pressure applications. In those situations, use a block vee packing. Wiperseals are available in nitrile and fluoroelastomer (LongLife) compounds.

Example

For this cylinder, assume a nominal 1.625”€? piston rod, normal service, no pressure. The actual rod diameter (dimension A) is chosen by the designer as:

1.625” +.000/-.005 From the size list, D is .218”

Now determine the maximum housing diameter (E): E max = A min + Y = 1.620” +.015” = 1.635”
The balance of the dimensions can be determined from the table below.

All metal surfaces contacting double lip rod wiperseals should be smooth and free from tool marks. A finish of 10-20 micro-inches Ra (arithmetic average) is recommended for the rod surface.

Installation

Correct dimensioning of the parts enclosing the double lip rod wiperseal are critical to installation and operation. Radial depth of the groove in which the seal is placed should not be less than its nominal crosssection. Keep the maximum diametral clearance (minimum diametral clearance plus tolerances on the two parts) as small as practical.

Quick reference standard stock size list for Nitrile rod wipers