Flammable varnish dip tanks and curing ovens

DATE: June 11, 1979

REPLY TO ATTN OF: Erie Area Office

SUBJECT: [1910.123 - 1910.126], As Applied to Dip Tanks Containing Varnish for Electric Motor Coating

TO: David H. Rhone, Regional Administrator

ATTN: Kenneth Gerecke, ARA for Technical Support

The following information was researched, prepared, and written by Safety Specialist Tony Rizzo. It summarizes a telephone conversation with Ken Gerecke and concerns a Technical Support request. This correspondence is provided for information purposes only, and is not a request for Regional Office response.

It has come to our attention, as a result of an inspection of a motor repair shop, that several varnishes used for electric motor coating are flammable. The usual method of application is via dip tank/curing oven method.

The varnishes appear to be anywhere from 48% to 90% nonvolatile when obtained from suppliers. The remaining 52% to 10% is usually xylol, naptha, mineral spirits, or some combination of these solvents. Supplier recommendations also suggest to users that infinite amounts of xylol, naptha, or mineral spirits can be added to enhance various varnish characteristics. Flash points for the supplied varnishes with these solvents are 85°F Tag Closed Cup and 90°F Seta Closed Cup. Specific gravity at 21°C is 912 - .922 and the viscosity at 25°C is 225 - 375 Brookfield (centipoises).

The sections of [1910.123 - 1910.126] requiring special attention by compliance officers in recognizing potential exposures are as follows:

(a) Paragraph [1910.124(b) and 1910.125(d)(2)] - most motor varnishes are combustible only. They may be made flammable by user adding solvents in quantity sufficient to change original flash point. CSHO should obtain supplier Material Safety Data Sheets for varnishes and solvents used prior to citing.

(b) Paragraph [1910.125(b)(1)] - CSHO should determine if potential exists for the varnish to overflow the tank during application of water during fire fighting and, if so, are employees endangered. In most cases, this will be a diminimus problem with motor varnishes, as water extinguishing methods are not used.

~~(c) Paragraph (c)(3) - the actions listed in STD 1-5.6 should be brought to the attention of employers by the CSHO as an alternate means of abatement.~~

[This document was edited on 06/01/99 to strike information that no longer reflects current OSHA policy.]

(d) Paragraph [1910.125(e)(1)] - CSHO should note location of the curing ovens for these dip tanks as a potential ignition source. In accordance with NFPA 86A, solvent atmosphere ovens must have a prominently displayed oven safety data form which lists the oven manufacturer's and owner's use instructions which are not to be deviated from. If these ovens are natural or fuel gas supplied, the location of the pilot light to the tank as well as the electrical controls for the oven should be considered as potential hazards as the solvents used are generally heavier than air.

(e) Paragraph .132(a) and .133(a)(1) - Due to solvent content of varnishes, manufacturer's recommend protective handwear/aprons and protective eye and face equipment and exposure may exist depending on the dipping method used.

This office would appreciate any other information which may be available concerning this subject.
John H. Stranahan
Acting Area Director