Posts Tagged ‘Collecting’

The History of Thimbles

Monday, December 28th, 2009

 

A thimble is a protective shield worn on the finger or thumb generally worn during sewing.

While collecting thimbles became popular in the mid 1800 as a result of the special thimbles that were made for the Great Exhibition held in the Crystal Palace in Hyde Park, London, the earliest known thimble was Roman and found at Pompeii. Made of bronze, it has been dated to the first century AD. A Roman thimble was also found at Verulamium, in the UK. and can be seen in the museum there.

The first thimble made in England was in 1695 by a Dutch metal worker named Lofting. It was called the ” thumb-bell,” because it was worn on the thumb when in use, and shapped like a bell. The shape eventually changed, but the name, softened into thimble, still remains.

Thimbles are usually made from metal, leather, rubber, wood, glass, or china. Early thimbles were sometimes made from whale bone, horn, or ivory. Advanced thimblemakers enhanced thimbles with semi-precious stones to decorating the apex or along the outer rim. Thimble artists would also utilize enameling.

Originally, thimbles were used solely for pushing a needle through fabric or leather as it was being sewn. However they have since gained many other uses and mythologies. In the 1800s they were used to measure spirits (hence the phrase “just a thimbleful”). Women of the night used them in the practice of thimble-knocking where they would tap on a window to announce their presence. Thimble-knocking also refers to the practice of Victorian schoolmistresses who would tap on the heads of unruly pupils with dames thimbles. Thimbles have also been used as love-tokens and to commemorate important events. A miniature thimble is one of the tokens in the game of Monopoly.

Before the 18th century the small dimples on the outside of a thimble were made by hand punching, but in the middle of that century, a machine was invented to do the job. Another consequence of the mechanisation of thimble production is that the shape and the thickness of the metal changed. Early thimbles tend to be quite thick and to have a pronounced dome on the top. The metal on later ones is thinner and the top is flatter.

In the 19th century many thimbles were made from silver. Because this is a soft metal, it is easily pierced by a steel needle. Charles Horner solved the problem by using a steel core covered inside and out by silver. The result was still as pretty as a traditional silver thimble but more practical and durable. He called his thimble the Dorcas and these are now popular with collectors.

Early American thimbles made of whale bone or tooth featuring miniature scrimshaw designs are considered valuable collectibles. Such rare thimbles are prominently featured in a number of New England Whaling Museums.

During the First World War silver thimbles were collected from “those who had nothing to give” by the British government and melted down to buy hospital equipment. In the 1930s and 40s red-topped thimbles were used for advertising. Leaving a sandalwood thimble in a fabric stores helps to keep moths away.

People who collect thimbles are known as digitabulists.

 

Fabric Type Dust Collection for Air Cleaning

Saturday, November 21st, 2009

Canadian Air Systems Co. is an engineering company that designs industrial dust collection systems. Dust collecting equipment is available in numerous designs utilizing a number of principles and featuring wide variation in effectiveness, initial cost, operating and maintenance expense, space, arrangements and material of construction.

One of the most widely used type of dust collector is Fabric Dust Collector.

Fabric arresters are high efficiency, medium cost collectors. The effectiveness of passing air or gas through a fabric at low velocity has been recofnized and used for many years in air cleaning devices. Fabric is arranged in envelope or tubular (stocking) shapes. While removal appears to take place by a staining action of the media, in reality dust collection is obtained by building up a mat of the material on the dirty side of the media. This mat provides the actual filtering or straining bed. By means of this bed a high degree of removal is obtained even on sub-micron size particles.

The dust collectors are used extensively in industry for a wide range of applications. They require more space than most other types of air cleaning devices, necessiating outdoor installation in most cases.

Some spesific types of Fabric Dust Collectors engineered by Canadian Air Systems Co. are:

INTERMITTENT DUTY FABRIC DUST COLLECTORS

These types may use either envelope or stocking arrangement of the fabric but will generally employ shaking or vibrating as a means of reconditioning. Periodically Uusually at 4 to 6 hour intervals0 the air flow must be stopped to effect reconditioning – thus the classification “intermittent”.

Rate of flow through the media seldom exceeds 4 fpm and often as low as 2 fpm. Ratings are usually selected so pressure drop will be in the 2″ – 5″ WG range between the beginning and the end of a cycle.

As dust accumulates on the media. resistance to flow increases and air flow decreases until the fan is stopped and the media reconditioned. Variation in air flow due to changing pressure losses is sometimes a disadvantage and when coupled with requirement to periodically stop flow may preclude use of intermittent dust collectors.

MULTIPLE-SECTION, CONTINUOUS DUTY, AUTOMATIC FABRIC DUST COLLECTORS

The disadvanteges of stopping the air flow to permit vibration and variations in the airflow can be overcomed by using of sectional arresters allowing continuous operation of the exhaust system as automatic dampers periodically take one section out of service for reconditioning the fabric while the remaining sections take the entire gas volume. The large the number of sections, the nearer the pressure loss will remain constant. The use of reverse air flow to increase effectiveness of removing adhering material is sometimes incorporated in such designs. Reverse-flow collapse type and occasionally reverse-jet type dust collectors utilize the multiple-section principle.

When employing shakers as a means of reconditioning, rate of flow through the media (air to cloth ratio) will range from 2 to 4 fpm as with intermittent type dust collector. Generally this air to cloth ratio is based on net cloth area available when one compartment is out of service for reconditioning.

REVERSE-JET, CONTINUOUS-DUTY, FABRIC COLLECTORS

The reverse-jet type differs from the conventional arrEsters in its use of high pressure air to clean the fabric. One type uses high pressure air (30″ – 40″ WG) from a travelling “blow ring” to dislodge the collected cake from inside the fabric tube. Since dust laden air enters the top of the fabric tube, air flow within the stocking is downward to the hopper allowing the fabric to be cleaned without stopping air flow. Multiple sections or comartmentation is not required for continuous duty. The”blow ring” is normally operated continuously.

Another type uses high pressure compressed air (100 PSI) to break the dust cake from the exterior of the fabric tube or envelope by the intermittent application of reverse-jet compressed air. In some dust collectors of this type multiple sections are utilized. Other dust collectors apply the compressed air on only one or very few tubes or envelopes at a time prventing air flow in adjacent tubes or envelopes and decreasign the possibility of re-entrimane and redeposition.

Cleaning or reconditioning by the reverse-jet method is more complete than that obtained by vibrating or shaking. Higher air flows are possible due to short reconditioning cycle. Air flow rates of 6 to 12 fpm are usual. Pressure loss will be more nearly uniform (generally 4″ to 6″ WG if properly rated) and exhaust air volume will be more nearly constant. Fabric dust collectors of this type might be more expensive and require added maintenance for the cleaning mechanism.

REVERSE-FLOW COLLAPSE, CONTINUOUS DUTY DUST COLLECTORS

Reverse-flow collapse cleaning is generally used with glass media which is fragile and requires a gentle cleaning technique. Reversing the glass flow provides a gentle collapse of the fabric usually in a “four point star” braking the dust cake which falls by gravity into the hopper.

For additional information please refer to http://www.nis-co.com/fumeextractor/Index.html.

Oleg TchetchelIndustrial Process DesignerCanadian Air Systemshttp://www.nis-co.com/contact/Index.htmlhttp://www.nis-co.com/fumecollector/Index.html

Air Cleaning With Fabric Dust Collectors

Friday, November 20th, 2009

Oleg Systems Co. produces various types of industrial dust collection systems. Dust collecting equipment is available in numerous designs utilizing a number of principles and featuring wide variation in effectiveness, initial cost, operating and maintenance expense, space, arrangements and material of construction.

One of the most widely used type of dust collector is Fabric Dust Collector.

Fabric arresters are high efficiency, medium cost collectors. The effectiveness of passing air or gas through a fabric at low velocity has been recofnized and used for many years in air cleaning devices. Fabric is arranged in envelope or tubular (stocking) shapes. While removal appears to take place by a staining action of the media, in reality dust collection is obtained by building up a mat of the material on the dirty side of the media. This mat provides the actual filtering or straining bed. By means of this bed a high degree of removal is obtained even on sub-micron size particles.

The dust collectors are used extensively in industry for a wide range of applications. They require more space than most other types of air cleaning devices, necessiating outdoor installation in most cases.

Some spesific types of Fabric Dust Collectors engineered by Oleg Systems Co. are:

INTERMITTENT DUTY FABRIC DUST COLLECTORS

These types may use either envelope or stocking arrangement of the fabric but will generally employ shaking or vibrating as a means of reconditioning. Periodically Uusually at 4 to 6 hour intervals the air flow must be stopped to effect reconditioning – thus the classification “intermittent”.

Rate of flow through the media seldom exceeds 4 fpm and often as low as 2 fpm. Ratings are usually selected so pressure drop will be in the 2″ – 5″ WG range between the beginning and the end of a cycle.

As dust accumulates on the media. resistance to flow increases and air flow decreases until the fan is stopped and the media reconditioned. Variation in air flow due to changing pressure losses is sometimes a disadvantage and when coupled with requirement to periodically stop flow may preclude use of intermittent dust collectors.

MULTIPLE-SECTION, CONTINUOUS DUTY, AUTOMATIC FABRIC DUST COLLECTORS

The disadvanteges of stopping the air flow to permit vibration and variations in the airflow can be overcomed by using of sectional arresters allowing continuous operation of the exhaust system as automatic dampers periodically take one section out of service for reconditioning the fabric while the remaining sections take the entire gas volume. The large the number of sections, the nearer the pressure loss will remain constant. The use of reverse air flow to increase effectiveness of removing adhering material is sometimes incorporated in such designs. Reverse-flow collapse type and occasionally reverse-jet type dust collectors utilize the multiple-section principle.

When employing shakers as a means of reconditioning, rate of flow through the media (air to cloth ratio) will range from 2 to 4 fpm as with intermittent type dust collector. Generally this air to cloth ratio is based on net cloth area available when one compartment is out of service for reconditioning.

REVERSE-JET, CONTINUOUS-DUTY, FABRIC COLLECTORS

The reverse-jet type differs from the conventional arrEsters in its use of high pressure air to clean the fabric. One type uses high pressure air (30″ – 40″ WG) from a travelling “blow ring” to dislodge the collected cake from inside the fabric tube. Since dust laden air enters the top of the fabric tube, air flow within the stocking is downward to the hopper allowing the fabric to be cleaned without stopping air flow. Multiple sections or comartmentation is not required for continuous duty. The”blow ring” is normally operated continuously.

Another type uses high pressure compressed air (100 PSI) to break the dust cake from the exterior of the fabric tube or envelope by the intermittent application of reverse-jet compressed air. In some dust collectors of this type multiple sections are utilized. Other dust collectors apply the compressed air on only one or very few tubes or envelopes at a time prventing air flow in adjacent tubes or envelopes and decreasign the possibility of re-entrimane and redeposition.

Cleaning or reconditioning by the reverse-jet method is more complete than that obtained by vibrating or shaking. Higher air flows are possible due to short reconditioning cycle. Air flow rates of 6 to 12 fpm are usual. Pressure loss will be more nearly uniform (generally 4″ to 6″ WG if properly rated) and exhaust air volume will be more nearly constant. Fabric dust collectors of this type might be more expensive and require added maintenance for the cleaning mechanism.

REVERSE-FLOW COLLAPSE, CONTINUOUS DUTY DUST COLLECTORS

Reverse-flow collapse cleaning is generally used with glass media which is fragile and requires a gentle cleaning technique. Reversing the glass flow provides a gentle collapse of the fabric usually in a “four point star” braking the dust cake which falls by gravity into the hopper.

For additional information please refer to http://www.olegsystems.com/dustcollector/Index.html.

Oleg ChetchelIndustrial Process DesignerOleg Systems Co.http://www.olegsystems.com/scrubber/Index.htmlhttp://www.olegsystems.com/fan/Index.html

Fabric Type Dust Collectors for Air Cleaning

Saturday, October 31st, 2009

Canadian Air Systems Co. is a well known manufacturer of industrial dust collection systems. Dust collecting equipment is available in numerous designs utilizing a number of principles and featuring wide variation in effectiveness, initial cost, operating and maintenance expense, space, arrangements and material of construction.

One of the most widely used type of dust collector is Fabric Dust Collector.

Fabric arresters are high efficiency, medium cost collectors. The effectiveness of passing air or gas through a fabric at low velocity has been recognized and used for many years in air cleaning devices. Fabric is arranged in envelope or tubular (stocking) shapes. While removal appears to take place by a staining action of the media, in reality dust collection is obtained by building up a mat of the material on the dirty side of the media. This mat provides the actual filtering or straining bed. By means of this bed a high degree of removal is obtained even on sub-micron size particles.

The dust collectors are used extensively in industry for a wide range of applications. They require more space than most other types of air cleaning devices, necessiating outdoor installation in most cases

The usual fabric is a specially wooven cotton, altough wool, paper , glass cloth and synthetic fabrics may be used in certain applications. In recent years glass cloth has come into wide use because of silicone treatment of the glass fibers and employment of reverse flow techniques for cleaning. Silicone treatment provides a lubricant between fibers and increases fabric life.

Fabric collectors are limited to air conditions dry enough to prevent condensation or free moisture deposition on the fabric. With hygroscoping materials, there will be a bonding tendency between particles and fabric under high relative humidity even though no condensation takes place. Maximum recommended temperature for cotton fabric is 180 F, for wool 200 F. Higher temperatures can be handled by using synthetic materials including nylon or orlon fabrics as well as glass cloth and, occasionally, fine metallic mesh. The synthetic fabrics mau be used up to 300 F while glass cloth is acceptable to 550 F.

As dust is collected on the fibric, resistance to air flow increases. Periodically the fabric must be reconditioned by shaking, vibrating, reverse jet or reverse-flow collapse which agitates suffitiently to remove the bulk of adhering material allowing it to drop into the dust hopper. In most collectors air flow must be stopped during reconditioning, otherwise released material will be re-entrained and redeposited on the fabric. Sufficient dust must adhere to the fabric to maintain the dust mat needed for maximum efficiency; therfore, after reconditioning the pressure drop will be considerably higher than loss through new fabric.

Rate of flow through the media varies with dust collector type, application and dust concentration. Ratings are usually selected so pressure drop will not exceed 5″ WG. The smaller the particle, the more rapid the resistance rise for a given loading. For the same air flow rate and dust loading, resistance rise increases directly in proportion to time.

Some spesific types of Fabric Dust Collectors manufactured by Canadian Air Systems Co. are:

- Intermittent-Duty Fabric Collectors

  These types may use either envelope or stocking arrangement of the fabric but will generally employ shaking or vibrating as a means of reconditioning. Periodically Uusually at 4 to 6 hour intervals0 the air flow must be stopped to effect reconditioning – thus the classification “intermittent”.

- Multiple-Section, Continuous-Duty, Automatic Fabric Collectors

  The disadvanteges of stopping the air flow to permit vibration and variations in the airflow can be overcomed by using of sectional arresters allowing continuous operation of the exhaust system as automatic dampers periodically take one section out of service for reconditioning the fabric while the remaining sections take the entire gas volume.

- Reverse-Jet Fabric Collectors

  The reverse-jet type differs from the conventional arrsters in its use of high pressure air to clean the fabric. One type uses high pressure air (30″ – 40″ WG) froma travelling “blow ring” to dislodge the collected cake from inside the fabric tube. Another type uses high pressure compressed air (100 PSI) to break the dust cake from the exterior of the fabric tube or envelope by the intermittent application of reverse-jet compressed air.

- Reverse-Flow Collapse, Continuous-Duty Collectors

  Reverse-flow collapse cleaning is generally used with glass media which is fragile and requires a gentle cleaning technique. Reversing the glass flow provides a gentle collapse of the fabric usually in a “four point star” braking the dust cake which falls by gravity into the hopper.

For additional information please refer to http://nis-co.com/dustcollection/Index.html.

Oleg TchetchelIndustrial Process EngineerCanadian Air Systemshttp://nis-co.comhttp://nis-co.com/fumeextractor/Index.html