Von Duprin 9857 Cylinder Replacement

Introduction

The Von Duprin 9857/9957 is a surface mounted three-point exit device. If you can imagine combining a rim exit device with a surface mount vertical rod exit device that is the Von Duprin 9857/9957. The difference between the 9857 and the 9957, like all 98/99 Series exit devices, is that the 9857 features a smooth case mechanism and 9957 features a grooved case mechanism. Here are additional specifications for the 9857/9957 exit device:

One of the most common servicing tasks for the 9857/9957 is the rekeying or replacement of the exit device’s rim cylinder. While this seems like a straightforward task, there are some finer, important details involved. With this in mind, I will cover those details in this article. Here is the 9857 that will have it’s cylinder changed :

Von Duprin 9857

This 9857 features a 996L-NL lever trim option. The 996L-NL is a “night latch” function; the key retracts the latch bolts with each turn but it does not unlock the exit device permanently.

996L-NL Lever Trim

Process

1. Test the operation of the 9857 device and it’s key prior to servicing. If a problem exists with the device, the key, and/or the cylinder, it’s best to identify it before servicing further. If no problem is found servicing can proceed. but if a problem is found it may need to be fixed prior to further servicing.

2. Start by removing the main case unit cover and the end cap (marked with red arrows). The main case unit cover is secured in place with 4 Phillips-head screws and the end cap is secured by 2 Phillips-head screws. Removal of both items will allow access to the mounting screws.

Von Duprin 9857 Main Case Unit Cover and End Cap

3. Loosen the mounting screws on the end cap bracket. These screws only need to be loosed enough to allow the mechanism case to slide away from it.

Von Duprin 9857 End Cap Bracket

4. Disconnect the top and bottom rods from the main case unit by first removing the two rod guides (top and bottom). Once removed, the vertical rods can slide forward and away from the main case unit.

Von Duprin 9857 Top and Bottom Rods Disconnected

5. Remove the 4 Phillips-head mounting screws on the main case unit. These screws connect the 996L-NL trim to the main case unit. When removing your 4th and final screw keep your hand on both the 996L-NL trim and the main case unit so that neither unexpectedly falls from the door.

6. Slide the mechanism case away from the end cap bracket and remove it from the door.

Von Duprin 9857 Case Mechanism Removed

7. Remove the 996L-NL trim from the door.

8. Remove the 2 mounting screws from the back of the existing rim cylinder within the 996L-NL trim.

Von Duprin 9857 Rim Cylinder Screws

9. Allow the existing rim cylinder to drop out the 996L-NL trim.

10. To prepare the new rim cylinder, adjustments to it’s tailpiece are often required so that the cylinder is suited for the door and the device. We can determine the required adjustments by comparing the new rim cylinder with the existing rim cylinder. Break or cut the new rim cylinder’s tailpiece so that the length of the new rim cylinder (including the tailpiece) matches the existing rim cylinder. To accomplish this place vise grips, channel locks, or similar tools on both sides of a pre-cut portion of the tailpiece and break it off at that point.

Comparing Rim Cylinders

Breaking Off Piece From Tailpiece

Verifying Tailpiece’s Length

11. The new mounting screws will often need to be adjusted as well. In this example, the existing screws and new screws diameters were different and not compatible. Even if they were compatible, it is advisable to replace the screws since they are included with new rim cylinders. Break or cut the new screws so that their length matches the existing screws. To accomplish this place vise grips, channel locks, or similar tools on both sides of a breakaway portion of the screw and breaking it off at that point. Exercise care during this step to avoid damaging the screw’s threads; it doesn’t require much force.

Breaking Off Piece From Cylinder Screw

12. Place the new cylinder inside of the 996L-NL trim and install with new mounting screws.

New Rim Cylinder Installed

13. Place the 996L-NL trim back on the door, making sure that the tailpiece extends through the other side of the door.

996L-NL Trim Placed Back On Door

14. Slide the mechanism case onto the end cap bracket.

15. Carefully mate the main case unit with the 996L-NL trim. Make sure that the tailpiece enters the case unit before proceeding.

16. Reconnect the top and bottom rods on the main case unit.

17. Reinstall 1 of the mounting screws in the main case unit. With 1 screw installed, we can check the function of the new rim cylinder as well as the rest of the device to ensure everything is positioned correctly. If something were not, it’s much easier to remove 1 screw instead of 4 to fix this.

Von Duprin 9857 Case Unit Mounting Screw Installed

18. Once the satisfactory function of the new cylinder and 9857 have been verified, reinstall all remaining mounting screws for the main case unit.

Mounting Screws Reinstalled on Main Case Unit

19. Tighten the mounting screws on the end cap bracket.

20. Replace the main case unit cover and the end cap.

21. Test the operation of the 9857 device one final time.

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