Sleeves & Washers

Lamons sleeve and washer sets, when combined with our sealing/isolation gaskets, complete a Flange Isolation Kit. For a successful flange isolation kit, it is critical to use the appropriate material for your application. Compressive strength, flexural strength and cut- through resistance are key material physical properties that should not be overlooked.

Washer Design Specifications:
Available for bolt sizes = 0.50" (12.70mm) to 2.75" (69.85mm)

  • Steel and isolation washers are designed with the same O.D. and I.D.
  • Steel and Isolating washers are 0.125" (3.18mm) thick.
  • Steel and Isolating washers are designed to fit over isolating sleeve material.

Steel back-up washers need to be supplied with the same O.D. and I.D. crushedWasher as the isolation washer. This graphic illustrates a steel back-up washer and phenolic isolation washer with different O.D. and I.D. sizing. The compressive load from the steel back-up washer is not equally distributed over the phenolic washer, causing the phenolic washer to crack. If this occurs, the gasket may not receive proper load and electrical isolation will most likely be lost.


Single Washer Set (per bolt/stud)

  • (1) each 1/8" thick steel ZP washer
  • (1) each 1/8" thick isolating washer
  • (1) each isolating sleeve

"FIK 101" Generally, single washer sets are used for buried applications and may be used to allow the Cathodic Protection (CP) current to reach the nuts and bolts/stud. If desired, the nuts on the opposite side of the cathodically protected flange may be included as part of a Cathodic Protection System.


Double Washer Set (per bolt/stud)

  • (2) each 1/8" thich steel ZP washer
  • (2) each 1/8" thick isolating washer
  • (1) each isolating sleeve

"FIK 101" Generally, double washer sets are used for applications, where added protection is needed against the possibility of "shorting out" the nuts and bolts. For complete electrical isolation, double washer sets isolate the nuts and bolts from both flanges.

Lamons Sleeves - Material Physical Property Specifications


Test Method





Dielectric Strength, Volts/Mil. Short Time





Water Absorption (%)





Flexural Strength (psi)





Cut Through Resistance





Temperature - Operating

-75°F (-59³C) to +302°F (+150°C)

Cryogenic to +302°F (+150°C)

+65°F (-54°C) to +450°F (+232°C)

Lamons Washers - Material Physical Property Specifications


Test Method




Steel (HC)



Compressive Strength (psi)







Dielectric Strength, Volts/Mil. Short Time







Water Absorption (%)







Temperature - Operating

Cryogenic to +302°F (+150°C)

-100°F (+73°C) to +392°F (+200°C)

+65°F (-54°C) to +220°F (+104°C)

Cryogenic to +302°F (+150°C)

-100°F (-73°C) to +392°F (+200°C)

Isolating Sleeves (G10, Mylar, Nomex®)

Lamons isolating sleeves are designed/manufactured to fit over standard size flange fasteners (bolts/studs) with standard size bolt holes.

Sleeve Design Specifications:

  • Sleeves are designed to fit over standard bolts and studs for flanges.
  • Wall Thickness = 1/32" (0.79mm).
  • Available for bolt sizes = 1/2" (12.7mm) to 2-3/4" (69.85mm).
  • Sleeve length is designed to pass completely through the isolating washer and half-way through the steel washer for cathodic protection and isolation.

Isolating Washers (G10, G11, Phenolic, G3, Steel HC)

Lamons isolating washers are designed/manufactured to have positive isolation characteristics and provide excellent compressive strength.

Steel Washers/HC Washers

HC - Hardened 1050 steel with proprietary isolation coating has excellent dielectric properties and withstands UV. It is also abrasion resistant and will not break under compressive loads. They combine the technical features of steel into an isolating washer.

Steel Back-Up Washers/ZP Washers

ZP - Zinc Plated 1050 carbon steel washers are used as our standard steel back-up washer when packaged in kits with retainer washers and isolating sleeve material.
Note: 304 stainless steel available for special order.


HC washer with steel back-up washer bolted to washer test block. Megger isolation test unit confirms full 200G Ohm isolation at 1000V.

Lamons Standard Packaged Sleeve/Washer Sets. These sets have been selected from specification data as determined by industry usage over the years for flange isolation and cathodic protection. Single/Double choice is indicated after Packaged Set choice: S = Single, D = Double

E = Economy
Mylar Sleeves, Steel ZP Washers and Phenolic Washers (Double Washer Set Shown, Single Washer Sets Also Available).

S = Standard
G10 Sleeves, Steel ZP Washers and G10 Washers (Double Washer Set Shown, Single Washer Sets Also Available).

T = High Temperature
Nomex Sleeves, Steel ZP Washers and G3 Washers (Double Washer Set Shown, Single Washer Sets Also Available).

V = Value
Mylar Sleeves, Steel ZP Washers and G10 Washers (Double Washer Set Shown, Single Washer Sets Also Available).

Model T11
Nomex Sleeves, Steel ZP Washers and G11 Washers

Model V11
Mylar Sleeves, Steel ZP Washers and G11 Washers.

Model M
G10 Sleeves, Steel HC Washers and Steel HC Washers.

XX = Customer Specified
Customer Specified Sleeve and Washer Materials.

Bulk Sleeve and Washer Material

Lamons will provide washers in bulk quantities of 100. Sleeve material may also be purchased in bulk and is shipped and supplied in the lengths shown in the chart.
NOTE: It is suggested that bulk sleeve material be cut in a controlled environment. If cutting in the field, installers should be well versed in determining appropriate sleeve length and have experience with cutting.

Sleeve Material



4 Feet


6 Feet


6 Feet

Other information

General Installation Tips

  1. Always use proper safety equipment.
  2. Installation should be done with a torque wrench or stud tension measuring device.
  3. User to inspect and determine that components are packaged as specified.
  4. Flanges shall be free of pits, gouges, rust, debris, oil and grease. Surface finish shall be no greater than 250 RMS.
  5. Check bolts and nuts to ensure they are clean.
  6. Flange bolt hole spot facings shall be clean and free of burrs.
  7. Do NOT force or cram sleeved bolt assemblies. If force is needed, re-check flange alignment & ensure sleeve damage has not occurred.

Cut-Through Resistance

Cut Through Resistance and Flexural Strength are critical in selecting sleeve material for your flange isolation kit application. As nominal pipe size increases, as well as ANSI or API class, the fasteners (bolts/studs) increase in size and torque is generally higher. Larger and heavier stud bolts with higher torque loads can more easily cut through material during installation. This is more likely to occur if flanges and bolt holes are not in perfect alignment.
Use or specify G10 sleeve material as a standard for all applications. Or consider G10 sleeves for applications of Nominal Pipe Size 12-inch and larger and ANSI pressure class 600# and higher.
The above graphic shows an example of a Mylar Sleeve being shredded; the bolt threads are cutting through the sleeve while misalignment is cracking the sleeve. Electrical isolation can be lost if your sleeve material does not have excellent cut through resistance. Isolation tests will fail and installation costs will increase significantly.

Full Length Sleeve

A full length sleeve passes entirely through both flanges, both isolation washers, and half way through the steel back-up washers on each side.
Note: When using mis-matched flanges or flanges with different widths take precise measurements and account for the additional length needed to pass through washer set configuration. If you are unsure of proper length please consult the factory engineering support.

Bolt/Stud Diameters

Bolts/Studs with smooth shank portions should not have a bolt diameter greater than the maximum diameter of the threads. If this is the case, the sleeve may not fit over the shank portion. The adjacent graphic shows shank/threads sized differently, which will cause problems during field installation.