Do you know how to prevent premature steam valve failures?

Periodically, PRIMUS experiences repetitive field failures of steam-to-jacket valves and steam-to-chamber valves immediately following the start-up of a new steam sterilizer using in-house steam.

Acute Failure Mode in New Installations with House Steam

The valves have almost universally failed in the following manner:

The original valve fails within a day or two of the sterilizer start-up.

The replacement valve fails a few days or a few weeks following installation. 

The third valve does not fail but instead operates as designed.

Supplier Corrective Action Report Findings

When these failed valves are returned to the OEM for analysis under the PRIMUS Supplier Corrective Action Report (SCAR) system, the failures are largely determined to result from corrosion build-up on the internal valve spring and other critical valve parts.

Corrosion Particles from Carbon Steel Piping

The corrosion particles found in the valve internals are composed of carbon steel which originates in the new carbon steel piping ASTM A106 used to construct the new portion of the house steam system.

PRIMUS Steam Valves Forced to Act as a Filter

The valves have acted as a filter when the new carbon steel pipe is being conditioned by boiler corrosion control chemicals (developing a protective inner piping surface film that helps mitigate further corrosion). During this period, iron oxides are formed that slough off in the steam flow as it makes its way through the steam piping.

Failure to Flush New Steam Piping Exacerbates the Problem

The situation is also exacerbated when a facility does not take the time and manpower to thoroughly flush newly installed steam, water, and condensate piping. Metal filings, welding slag, and other carbon steel waste materials are readily flushed downstream into the steam sterilizer and other equipment. Most valve failures that occur immediately upon start-up or shortly after are due to residual waste and corrosion particles left in the piping after construction.

Use of a Steam Filter and Steam Trap

Based on the information above, PRIMUS strongly recommends the installation of a steam filter and associated steam trap in those facilities with new carbon steel steam piping systems supplying one or more steam sterilizers.

While modestly expensive, a steam filter can eliminate unnecessary costs and downtown associated with premature steam valve replacements.

As Option P35, when initially purchased or as an aftermarket kit assembly/spare parts, PRIMUS offers stainless steel filter housings and porous metal filter elements.

3/4" Stainless Steel Steam Filter Housing P/N 401165

1" Stainless Steel Steam Filter Housing P/N 401160

10" Length, 1.3 Micron Porous Metal Filter Element P/N 401162

3/4" Steam Filter Kit Assembly P/N 224110

1" Steam Filter Kit Assembly P/N 224100

The Steam Filter Kit Assembly contains the following parts:

Steam Filter Housing

1.3 Micron Porous Metal Filter Element

Steam Trap

Trap Fitting to connect the trap to the filter housing

Part 2 – Chronic Valve Failures (Over a Long Period)

Erosion and Corrosion – Chronic System Effects – General Information Water, entrained in steam flow and as non-discharged condensate traveling at high speeds in piping, is the source of most piping erosion. By repeatedly impacting piping at bends, the water can cause the gradual thinning of the pipe wall due to its mass and high impact velocity, similar to what occurs in industrial water jet cutting—this type of erosion - caused by water droplets.

Corrosion occurs due to dissolved carbon dioxide and oxygen in the condensate. When CO2 dissolves in water, it forms carbonic acid, which attacks the surface of carbon steel.

In many cases, but particularly with carbon steel piping, erosion can remove the protective inner piping surface treatment, thereby speeding corrosion. Both erosion and corrosion typically work together to cause the thinning of the steam pipe's inner wall.

Corrosion and erosion particles can build up in sterilizer steam valves over time. Complete valves or internal kit parts are normally replaced as part of a proper PM program before an unexpected valve failure occurs.

Preventing Piping System Erosion and Corrosion

Depending upon individual circumstances, facilities can apply several options to prevent/rectify erosion and corrosion. 

The following items are included:

Implementing water chemistry measures

Proper piping design/layout to improve flow geometries Installing more corrosion-resistant materials (e.g., stainless steel)

Water chemistry control measures are highly attractive to most facilities because they offer a readily available and comparatively inexpensive means of prolonging the life of existing piping.

Summary

PRIMUS strongly encourages end users operating new carbon steel steam piping systems to consider investing in a steam filter assembly to eliminate costly downtime and material costs due to premature sterilizer steam valve failures.

Have questions?

Contact our in-house PRIMUS sterilizer expert, Dave Schall at 877.679.7800 x1212 or by email at dschall@spire-is.com.

Visit our website at www.spire-is.com