ISSUE DATE: 06/20/2011

PROGRAM INFORMATION BULLETIN NO. P11-46

FROM: KEVIN G. STRICKLIN

Administrator for 

Coal Mine Safety and Health

NEAL H. MERRIFIELD

Administrator for

Metal and Nonmetal Mine Safety and Health

LINDA ZEILER

Acting Director of Technical Support

SUBJECT: Reissue of P07-18 - Maximum Total Exhaust System

Backpressure Specification Increase for Caterpillar Inc.’s

(Caterpillar’s) 3304 PCNA and 3306 PCNA Diesel

Engines

Who needs this information?

This Program Information Bulletin (PIB) is intended for all underground mine operators 

using diesel-powered equipment, manufacturers of diesel-powered underground 

mining equipment (including manufacturers of exhaust after-treatment control devices 

and systems), diesel engine manufacturers, miners’ representatives, and Mine Safety 

and Health Administration (MSHA) personnel.

Why is MSHA issuing this PIB?

This PIB is being issued to inform interested parties of the increase of the maximum 

total exhaust system backpressure specification for Caterpillar’s 3304 PCNA and 3306 

PCNA diesel engines used in underground mining.
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What is the new maximum total exhaust system backpressure limit for the Caterpillar 

engine approvals listed?

The maximum total exhaust system backpressure specifications for Caterpillar’s 3304 

PCNA and 3306 PCNA diesel engines have been updated to allow for a maximum 

total exhaust backpressure limit of 60 inches of water for each engine. Caterpillar’s 

original exhaust backpressure limit for each engine was 34 inches of water. Caterpillar

allows this increase with two stipulations: 1) no warranty claims for valve train 

components will be accepted for any mining company who adopts this increase in 

backpressure, and 2) participating mining companies and their subsidiaries should 

submit a list of serial numbers from affected engines to Caterpillar for warranty 

tracking purposes. MSHA will not be involved in the warranty stipulations specified 

by Caterpillar. Warranty is an issue between the mine operator and Caterpillar.

Does the increase in the maximum total exhaust system backpressure limit affect the 

Checklists for Permissible Diesel Powered Machines?

Permissible machines approved by MSHA must be evaluated using approved 

permissibility checklists (Machine Checklist and Power System Checklist). MSHA has 

an addendum to the existing permissibility checklists which addresses the change to 

Caterpillar’s 3304 PCNA and 3306 PCNA maximum total exhaust system backpressure 

limit engine specification from 34 to 60 inches of water. This checklist addendum 

details the procedure to be used to check the engine’s total exhaust system backpressure 

and the service indicator gauge installation for the diesel particulate matter (dpm) filter 

if the higher maximum total exhaust backpressure limit is used. The addendum 

checklist supersede the total exhaust system backpressure limit and the dpm filter 

service indicator gauge installation checks currently listed in the approved 

permissibility checklists. The addendum is attached to this PIB. 

How does this increase in the backpressure limit affect the performance of wet 

exhaust conditioner systems (scrubbers)?

The increase in maximum total exhaust system backpressure limit to 60 inches of water 

may affect the performance of gravity feed water make-up tank systems on permissible 

equipment. The additional backpressure within the scrubber may prevent the gravity 

feed make-up tank from supplying water to the scrubber, resulting in nuisance engine 

shutdowns. If a mine chooses to increase the backpressure limit to 60 inches on the 

subject engines, it is recommended that the gravity feed make-up tank design be 

changed to a pressure feed make-up tank design.

Where can I find more information?

More information on engine backpressure effects can be obtained by contacting 

MSHA’s Technical Support, Approval and Certification Center (A&CC) at the contact 

information listed below or your engine manufacturer or distributor. MSHA provides a 

list of approved engines that specifies their respective maximum total exhaust system

backpressure limits at the A&CC’s List of Approved Products. This list can be found on 
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the internet at: 

https://lakegovprod2.msha.gov/ReportView.aspx?ReportCategory=EngineAppNumb

ers. 

A list of acceptable dpm filters can be found at:

http://www.msha.gov/01-995/Coal/DPM-FilterEfflist.pdf

What is the background for this PIB?

Diesel engine manufacturers specify a maximum total exhaust system backpressure 

limit in their approval documentation. Mine operators requested an increase in the 

backpressure specifications to allow for increased operating time before changing 

disposable diesel exhaust particulate filters. Caterpillar agreed to increase the 

maximum total exhaust system backpressure specification for the two engine models 

specified in this PIB. MSHA has determined that the increase to 60 inches of water 

exhaust backpressure limit remains in accordance with the manufacturer specifications 

for the filters in MSHA’s listing of acceptable DPM Control Technologies found on 

MSHA’s website and listed above. MSHA has also determined through laboratory 

testing that the increase in backpressure does not adversely affect ventilation rates. 

Who are the contact persons for this PIB?

Coal Mine Safety and Health, Health Division 

Robert Thaxton, (202) 693-9515

E-mail: thaxton.robert@dol.gov

Metal and Nonmetal Mine Safety and Health

Reginald J. Richards, (202) 693-9600

E-mail: richards.reginald@dol.gov

Technical Support, Approval and Certification Center

Gary Clark, (304) 547-2068

E-mail: clark.gary@dol.gov

What is the authority for this PIB?

The Federal Mine Safety ad Health Act of 1977, as amended, 30 U.S.C. § 801 et seq.;

30 C.F.R. part 7 subpart E, 30 C.F.R. part 75 subpart T, and 30 C.F.R. § 57.5066.

Who will receive this PIB?

Program Policy Manual Holders

Miners' Representatives

Underground Coal Mine Operators

Special Interest Groups

Engine Manufacturers