ARO Y186-50 Nitrile U-Cup Seal | 3/16 in. x 1-1/4 in. OD

ARO Y186-50 Nitrile U-Cup Seal

The ARO Y186-50 is a replacement Nitrile / Buna-N U-cup seal used in the pneumatic air-motor section of compatible ARO air-operated double-diaphragm pumps.

Official ARO service documentation identifies Y186-50 as Item 139 and specifies the seal size as 3/16 inch x 1-1/4 inch outside diameter.

Nitrile / Buna-N Construction

The Y186-50 is manufactured from Nitrile, also known as Buna-N or NBR. This elastomer is commonly used for pneumatic sealing applications in compatible compressed-air systems.

Verify lubricant, temperature and operating-environment compatibility before installation.

Verified Dimensions

• Component: U-Cup seal
• Material: Nitrile / Buna-N
• Section: 3/16 inch
• Outside diameter: 1-1/4 inch
• ARO parts-list position: Item 139

Air Motor and Major Valve Application

The Y186-50 is installed in the pump air section rather than the fluid section. It helps seal the major air-valve assembly as compressed air is redirected during pump cycling.

This part should not be confused with fluid-section seals that contact the transferred process liquid.

Compatible ARO Pump Families

Published ARO and replacement-parts documentation shows Y186-50 in compatible pump families including selected:

• PD15 Series pumps
• PD20 Series pumps
• PD30 Series pumps
• PM20 Series pumps
• Related EXP and specialty diaphragm-pump configurations

Compatibility depends on the complete pump model and air-motor design. Always verify the full ARO model before ordering.

Service Kit Component

The Y186-50 is documented in applicable:

• Air Section Service Kits
• Major Valve Service Assemblies
• Solenoid Service Kits

If multiple pneumatic seals or major-valve components show wear, compare the appropriate complete service kit with replacing the Y186-50 individually.

Related Air-Motor Seals

In applicable PD20 and PM20 air-motor assemblies, Y186-50 is installed with other sealing components such as:

• 95966 U-Cup - 3/16 inch x 1.792 inch OD
• Y325-32 Nitrile O-ring
• 95650 valve insert
• 95659 valve plate

These components have different sizes and functions and should not be interchanged.

Maintenance Inspection

Inspect the U-cup during air-section service for:

• Cuts or torn sealing lips
• Flattening or deformation
• Hardening
• Excessive wear
• Air leakage or poor sealing

Inspect the mating bore and adjacent valve components before installing the replacement seal.

Ordering ARO Y186-50

Before purchasing, confirm:

• ARO part number Y186-50
• Complete pump model
• Item 139 location where applicable
• Nitrile / Buna-N material requirement
• 3/16 inch x 1-1/4 inch OD dimensions
• Individual seal versus service-kit requirement

Using the exact manufacturer part number helps ensure the correct U-cup size and material are selected for the ARO air-motor assembly.