Kroll & Ziller (K&Z) Gaskets – The Ultimate Elastomeric Seal for All Plastic Flanges
Sealing options for plastic flanges (including FRP flanges) has been a continuous topic of discussion for many years. Because plastic flanges are torque-limited, the available selection of sealing materials is also limited when compared to steel piping; compressed non-asbestos, spiral-wound and PTFE gaskets, while offering great chemical resistance, are simply too hard to reliably seal on FRP flanges given typical torque limitations.
As a result, the use of elastomeric full-face gaskets tends to be ubiquitous with FRP piping specifications across most industries. Elastomeric gaskets typically seal at the low bolt torques used with FRP, with some exceptions, especially in smaller diameters where maximum bolt torque can be as little as 10 ft-lbs.
Elastomeric full-face gaskets also suffer in practice due to;
a limited ability to address minor flange face misalignment and still provide a seal;
“crimping” of the elastomer during install when trying to place the gasket flush against a flange face, over the bolts;
misalignment of gasket bolt holes to flange bolt holes which can cause tearing of the elastomer during bolt insertion, reducing effective service life or causing a leak immediately;
difficulty installing or replacing gaskets at tight tie points, especially where equipment is left in place during piping repairs or modifications. Because the bolts must pass through full-face gaskets, the gaskets must be in position between the flanges before any bolts are installed.
Taking the above limitations into consideration, we have a “wish list” of gasket properties that are ideal for FRP;
Manufactured from elastomeric rubber for a low-torque seal;
Enhanced ability to seal in the event of minor flange misalignment;
Ring gasket profile to eliminate crimping and misalignment associated with the bolt holes on a full face gasket.
Ring gasket profile to enhance installation at existing tie points.
Kroll & Ziller Rubber-Steel Ring Gaskets
Keeping our “wish list” in mind, and with the goal of providing enhanced sealing options to FRP piping system owners, Fibreglass Solutions, Inc. is proud to be the Canadian distributor for Kroll & Ziller (K&Z) rubber-steel ring gaskets. They provide the best sealing performance of any elastomeric gasket in the world, and are the recommended gasket for virtually every application serviced by our products.
K&Z rubber-steel ring gaskets provide the sealing performance of an o-ring (note the o-ring profile on the gasket ID pictured at the end of this bulletin), without the associated hassle of requiring grooved flanges, or concerns of if the o-ring is pinched or misaligned. There is also a secondary seal on the flat body of the gasket, providing additional assurance that a seal will be made.
We have noted that achieving a seal with a K&Z gasket can typically be made at bolt torques far less than the maximums as set out by FRP flange manufacturers.
K&Z gaskets provide enhanced sealing in cases of slight flange face misalignment, since the primary seal is moved all the way inwards to the flange ID.
The gaskets are rigid, unlike full-face gaskets due to a carbon steel insert which is vulcanized into the elastomer during manufacturing. This added stiffness not only provides superior blowout/extrusion prevention at higher pressures, but also allows rapid and reliable replacement of gaskets at tight tie points. The OD of the gasket, like all ring gaskets, is sized to be self-centering on the bolts which further accelerates installation. The ring gasket profile in an elastomeric gasket is unique to K&Z and is the primary design benefit.
Fibreglass Solutions uses K&Z gaskets in ASME B31.3 qualification test spools, where installers must be qualified to 3x product design. These tests are typically 700 – 900 psig, and we have yet to have a leak with K&Z ANSI Class 150 gaskets. These tests are often difficult to achieve with full-face gaskets.
K&Z gaskets are available in all commercially-available elastomers (neoprene, nitrile, EPDM, fluoroelastomer to name a few), so upgrading from an existing full-face elastomer to K&Z is straightforward.
Fibreglass Solutions inventories 1” through 40” gaskets, so they are only a day away from our Canadian customers when needed.
We would be happy to send out some samples for your consideration, and welcome the opportunity to further explain the technical benefits offered by K&Z gaskets compared to conventional full-face gaskets.
