Maintenance tips and formulas

Baghouse maintenance tips and formulas for general calculations including fabric selection, air to cloth ratio and others.

baghouse formulas
  • Baghouse maintenance tips
  • Fiber selection chart
  • Ventilation formulas
  • Temperature conversion table
  • Precoat & dye powder calculator
  • Videos

Baghouse maintenance tips

Baghouses and filter bags can be very costly to a company's bottom line - especially when the unexpected occurs. These tips provide some simple proactive ways to minimize emergency baghouse-related problems and expenses.

Use the dye test 
Proactively dye test filter bags before start-up 

dye test

One mistake that many companies have made is that if they are not planning to remove old filters and install new ones they ignore the baghouse altogether during the outage. We stress that anytime an outage occurs there should be a plan to inspect the fabric filter to confirm that the equipment, structure and filter bags are in good condition.

Sending fluorescent dye powder through the baghouse via the induced-draft fan is one way to confirm that existing bags are in good condition and that the tubesheets (or plate into which the filter bags are seated), walls and other metal-to-metal contact points are free of hole or small cracks. Dye powder travels through the system as dust would. If there's a breach, the fluorescent powder goes through it and enters the clean side of the baghouse (above the tubesheet).

Performing the dye test during an outage is obviously much safer than performing it while the equipment is operating. By taking this simple step it will ensure that the start-up of the baghouse will go smoothly once the outage is complete.

 

[Test installed filter bags]
[Determine remaining service life and proper installation]

 

[Proactively plan for outages]
[Minimize baghouse problems and expenses]

Fiber selection chart

FLSmidth AFT offers a wide variety of fabrics and finishes. Chart below lists some of the most commonly used. Many more are available upon request:

Fiber

Continuous

Acid

Alkali

Abrasion

Flex

Temperature

Resistance

Resistance

Resistance

Resistance

Cotton

180˚F  (82˚C)

Poor

Excellent

Average

Very Good

Polypropylene

212˚F  (100˚C)

Excellent

Excellent

Excellent

Very Good

Acrylic

260˚F  (126˚C)

Good

Average

Good

Very Good

Polyester

275˚F  (135˚C)

Fair

Fair

Excellent

Very Good

PPS

374˚F  (190˚C)

Very Good

Very Good

Very Good

Very Good

Aramid

392˚F  (200˚C)

Fair/Poor

Good

Excellent

Excellent

P-84®

473˚F  ( 245˚C)

Good

Fair

Good

Good

PTFE/Teflon®

500˚F  (260˚C)

Excellent

Excellent

Fair/Poor

Good

Fiberglass

500˚F  (260˚C)

Good

Fair

Average

Average

Ventilation formulas

 

Total CFM =      Velocity, FPM, x Duct Area, Sq. Ft.




   
Velocity

4005(Sq. root of VP) at Standard

Conditions  (70° at sea level)





   
Total cloth area sq. feet

[Bag D" x 3.14 x Bag L"] ÷ 144]

x Total Number of Bags





   
Gross Air to Cloth Ratio = ACFM ÷ Total Cloth Area, Sq. Ft         




   
Net Air to Cloth Ratio

ACFM ÷ Total ON LINE Cloth Area,

Sq. Ft





   
1" SPWG

.578oz/ Square inches = .0361 PSI=

.0735" HG (mercury)





   
1 PSI Air Pressure 27.70" SPWG = 2.036" Hg




   
Can Velocity

ACFM ÷[ total tubesheet area, Sq. ft.

- (hole area, ft2 x number of holes)]





   

Grain Loading

Expressed in grains/ft3

LBS of Dust handle per minute

x 700 divided into ACFM





   
Lob of dust/minute (Grains/Cubic Feet x ACFM) ÷ 7000     

Temperature conversion table

 

°C

°F

°C

°F

°C

°F

0

32









5

41

105

221

205

401

10

50

110

230

210

410

15

59

115

239

215

419

20

68

120

248

220

428

25

77

125

257

225

437

30

86

130

266

230

446

35

95

135

275

235

455

40

104

140

284

240

464

45

113

145

293

245

473

50

122

150

302

250

482

55

131

155

311

255

491

60

140

160

320

260

500

65

149

165

329

265

509

70

158

170

338

270

518

75

167

175

347

275

527

80

176

180

356

280

536

85

185

185

365

285

545

90

194

190

374

290

554

95

203

195

383

295

563

100

212

200

392

300

572

   

Centigrade to Fahrenheit= °C = (°F-32) 5/9.

 

Fahrenheit to Centigrade= °F = (9/5°C) +32.

 

 

 

 

 

Precoat & dye powder calculator