ISSUE DATE: 4/28/2011

PROGRAM INFORMATION BULLETIN NO. P11-32

FROM: KEVIN G. STRICKLIN 

 Administrator for 

 Coal Mine Safety and Health 

 NEAL H. MERRIFIELD 

 Administrator for 

 Metal and Nonmetal Mine Safety and Health 

 LINDA F. ZEILER 

 Acting Director of Technical Support 

SUBJECT: Re-Issue of P09-15 - Potential Safety Hazard Related to

 Explosion of Pumps 

Scope

This Program Information Bulletin (PIB) applies to all Mine Safety and Health 

Administration (MSHA) enforcement personnel, mine operators, independent 

contractors, and equipment manufacturers. 

Purpose

The purpose of this bulletin is to alert enforcement personnel, mine operators, 

independent contractors, and equipment manufacturers to potential safety hazards 

related to catastrophic failure (explosion) of pumps and/or associated components. 

Catastrophic failure of pumping systems can occur due to an overpressure condition 

created within the pump when fluid flow through the pump is lost, resulting in the 

overheating of any trapped fluid within the pump case. Loss of fluid flow can occur 

due to a blockage in the discharge and/or inlet piping. It can also occur due to a 

malfunctioning or inadvertently closed valve. 

Catastrophic failure can also occur due to a sudden surge of fluid ("fluid hammer") 
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through the pump or into downstream components after a delay in acquiring fluid, 

especially when the pump is turning at or near rated speed.

Information

Catastrophic failure of pumping systems can be reduced by detecting one or more lossof-flow conditions. Loss-of-flow conditions can be detected by 1) using direct fluid flow 

measuring equipment, 2) measuring the pump motor current draw (amperage) to detect 

loss of pump load, and/or 3) measuring the pump temperature to detect overheating of 

the fluid. Monitoring pumps for loss of flow will help detect dangerous conditions 

resulting from malfunctioning equipment, loss of fluid pickup or plugged or restricted 

discharge and/or inlet piping. 

Flow sensing devices can be installed which automatically shut down the pump if flow 

stops for any critical period of time. These devices can be simple paddle switches in a 

clean fluid such as well water, or they may be more sophisticated devices that do not 

come in contact with the fluid, such as magnetic flow meters for aggressive fluids such 

as slurries. 

Motor current sensing devices, which alert and automatically shut down the pump 

whenever the motor current draw drops below the expected operating range for any 

critical period of time can be installed in the system. Pump motor current typically 

drops when the feed is reduced and the pump ceases to pump material. 

Thermal sensing devices can be installed to measure the temperature of the liquid in the 

pump volute. A warning temperature and an automatic pump shut down temperature 

can be programmed into certain types of controllers. The American Society of 

Mechanical Engineers (ASME) requires two temperature sensors, one primary and one 

backup, when used as a safety device in this manner. Some types (styles) of these 

devices can be attached to the pump without drilling or tapping. Some programmable 

controllers allow for multiple set points such as alarm and shut down, so that remedial 

action could be performed to alleviate a problem before tripping the device. Mine 

operators should contact their suppliers or, the pump manufacturers for further 

assistance in identifying and implementing appropriate pump safety controls. 

Background

A plant operator received fatal injuries when a clean coal filter drain pump exploded 

due to restricted material flow which caused heat and pressure buildup within the 

pump. The access cover plate from the pump was blown off the pump striking the 

operator. The victim was standing approximately 8 feet away at the on/off switch 

when the pump cover struck him. The pump's discharge line had become clogged, but 

the pump continued to operate. The coal slurry in the pump volute became overheated, 

resulting in heat and pressure building to the point the cover plate was blown off. 
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The second fatality occurred when a fuel handler was fatally injured at a cement 

operation when he attempted to bleed air from a liquid waste-fuel system. An in-line 

grinder ruptured, and the escaping waste fuel ignited, engulfing him in flames. This 

accident could have been prevented if a flow device had sensed that the pumps were 

not producing any flow. Also, the catastrophic failure of the grinder occurred due to an 

overpressure condition. 

A miner was seriously injured when a centrifugal pump that was moving sand slurry 

exploded. Shrapnel from the explosion struck and seriously injured a miner 30 feet 

away. An investigation revealed that a plugged inlet and a restricted discharge was 

responsible for the explosion. The cause of the plugged inlet and restricted recharge is 

unknown. However, it is believed the pump may have been previously overheated and 

developed cracks due to backflow of cool fluid. These conditions could lead to the 

pump being unable to withstand normal operating pressures, or a plug in the discharge 

was dislodged by the explosion. 

In a non-injury accident, which could have resulted in a mine disaster, a pump in an 

underground mine exploded because material flow became restricted which caused the 

pump to overheat. The explosion of the overheated pump destroyed two permanent 

stoppings more than 150 feet from the explosion, and other stoppings that were out of 

the direct line of forces were also destroyed. Miners felt the blast more than 800 feet 

away. Approximately 175 pounds of the pump material were not found. 

Authority

The Federal Mine Safety and Health Act of 1977, Section 107(a). 

Issuing Offices and Contact Persons

Coal Mine Safety and Health, Division of Safety

John Arrington, (202) 693-9549

E-mail: arrington.john@dol.gov

Metal and Nonmetal Mine Safety and Health

Safety and Health Division

Marvin Lichtenfels, (202) 693-9600

E-mail: lichtenfels.marvin@dol.gov

Technical Support, Approval and Certification

Dale P. Ingold, (304) 547-2004

E-mail: ingold.dale@dol.gov

Internet Availability

This PIB may be viewed on the Internet by accessing the MSHA home page at 

(http://www.msha.gov) and choosing "Compliance Info" and "Program Information 
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Bulletins." 

Distribution

Program Policy Manual Holders

Special Interest Groups

Mine Operators

Independent Contractors

Equipment Manufacturers