Page 171 - Root Cause Failure Analysis

Dust Collectors 159

the fabric is greater than about g6 in. (which corresponds to a fabric dust loading on
the order of 0.1 Ibrdft’), the pressure drop across the fabric, including the dust in the
pores, usually is negligible relative to that across the dust layer alone.

In practice, K, and K2 are measured directly in filtration experiments. These values
can be corrected for temperature by multiplying the ratio of the gas viscosity at the
desired condition to the gas viscosity at the original experimental condition.

Collection Eficiency
Under controlled conditions (e.g., in the laboratory), the inherent collection efficiency
of fabric filters approaches 100 percent. In actual operation, it is determined by sev-
eral variables, in particular the properties of the dust to be removed, choice of filter
fabric, gas velocity, method of cleaning, and cleaning cycle. Inefficiency usually
results from bags that are poorly installed, tom, or stretched from excessive dust load-
ing and excessive pressure drop.

Installation

Most baghouse systems are provided as complete assemblies by the vendor. While the
unit may require some field assembly, the vendor generally provides the structural
supports, which in most cases are adequate. The only controllable installation factors
that may affect performance are the foundation and connections to pneumatic convey-
ors and other supply systems.

Foundation
The foundation must support the weight of the baghouse. In addition, it must absorb
the vibrations generated by the cleaning system. This is especially true when using
the shaker-cleaning method, which can generate vibrations that can adversely affect
the structural supports, foundation, and adjacent plant systems.

Connections
Efficiency and effectiveness depend on leak-free connections throughout the system.
Leaks reduce the system’s ability to convey dust-laden air to the baghouse. One
potential source for leaks is improperly installed filter bags. Because installation var-
ies with the type of bag and baghouse design, consult the vendor’s O&M manual for
specific instructions.

Operating Methods
The guidelines provided in the vendor’s 0&M manual should be the primary refer-
ence for proper baghouse operation. Vendor-provided information should be used
because there are few common operating guidelines among the various configura-
tions. The only general guidelines applicable to most designs are cleaning frequency
and inspection and replacement of filter media.