A Few Safety Guidelines For Electric Chain Hoists

Electric Chain Hoists are essential material-handling equipment that is widely used lift heavy objects easily and quickly. However, improper use of electric chain hoists can lead to damage and even death. This article tries to outline some of the safety issues concerning electric chain hoists. At the outset, these hoists should always be used in accordance with the applicable safety regulations. Under no circumstances should anyone try to hoist loads over or near people. Therefore, the operational area should be kept clear of people to avoid any untoward mishaps. At the same time, care should be taken that no one should be allowed to work under or near hoisted loads.

The manufacturer will always provide a safety and usage manual for the electric chain hoist. Organize a training session for the proper handling of the hoist. Also, ensure that the individual in charge of operating the hoist has understood and has demonstrated the capacity to operate this device safely and competently. Care also should be taken to ensure that the operator is physically fit. Always ensure that the hoist is fitted with a torque-limiting device for hoist overload protection. It is essential that hoists be tested for overloading prior to shipping. Any good manufacturer will include built in safety features such as upper and lower limit switches and low voltage controls. There should be an emergency stop button in case of an undesirable situation.

Also, allow the hoist to be inspected periodically by authorized personnel. The hoist should be run through the daily mandatory checks before it is handed over for operation. Regarding operational concerns, the operator should also follow some basic steps to ensure proper functioning of the electric chain hoist. He or she should always check that the brake is functional prior to operating the hoist. Also, ensure that the gears are properly lubricated with the right type of oil. Moreover, the hoist should normally not be used in a moist or saline environment. If there is no alternative, then it is a good idea to inform the manufacturer and obtain proper guidelines for the operation of the same.

While using an electric chain hoists, never operate beyond the rated capacities. Typical lifting capacities of these hoists are from around 0.5 tons to 5 tons. They are also available in different speed capacities. This is because chain hoists have to endure a variety of handling procedures. Care should be taken that you do not end up buying hoist that does not meet your desired specifications. The thumb rule is that never violate the safety norms, otherwise you could be held liable for death or damage to your staff or property. Therefore, the key to safe operation is adherence to all the safety parameters along with proper training and guidance of your staff and operational personnel.

Making an Educated Decision on Your Next Automated Plasma Shape Cutting Machine

Whether you are a first time buyer or have existing installations of plasma and/or oxy-fuel shape cutting systems, continuous advancements in technology and a growing landscape of low-cost manufacturers and integrators has clouded the automated plasma shape cutting machinery landscape.

Plasma cutting is the result of introducing an electrical arc through a gas that is blown through a nozzle at high pressure, causing the gas to turn into plasma and producing a focused flame that reaches temperatures of 50,000 degrees Fahrenheit. Automated plasma cutting systems are classified as either conventional or precision (high-definition), based on the characteristics of the cutting flame. Precision plasma systems are capable of producing parts to tighter tolerances, achieving faster cut rates, and producing less kerf and bevel than conventional plasma systems. The cost of these units can also be significantly higher than conventional plasma systems. It is therefore extremely important to properly match the shape cutting machine with the appropriate plasma cutting system.

One of the most common and costly pitfalls buyers encounter is when manufacturers or integrators mismatch machines and power sources. This is often the result of manufacturers not taking the time to understand the buyer’s requirements, having a limited or single-product line of machines, limited OEM access to power sources, and/or a lack of industry/application knowledge. These manufacturers will then often sell with a focus on lowest price instead of lowest cost of ownership, highlighting the strong point of the plasma system or the machine without regard to the limitations of the other. The best precision plasma power source available will not provide users with the desired cut quality and accuracy if it is not mated to an appropriate base machine.

There are many types of plasma shape cutting machines available in the market today. The most common machines are bridge or gantry style machines made from either fabricated steel or extruded aluminum. Construction of the machine is extremely important relative to your application. Machines constructed of extruded aluminum are typically considered to be hobbyist or artisan machines and most appropriate when doing a limited amount of cutting or when cutting light gauge materials. The plasma and oxy-fuel cutting processes create large amounts of heat which is retained in the materials being cut and can cause deflection or warping of aluminum machine components traveling over the hot cutting surfaces, greatly effecting accuracy and cut quality. Fabricated steel machines are highly recommended for any type of continuous cutting process, cutting of plate steel, and where auxiliary oxy-fuel torches may be used. Auxiliary heat shields may also be available to further protect the machine and components from extreme heat conditions.

Cutting machines are available with a variety of drive systems including single-side drive, single-motor dual-side drive, and true two-motor dual-side drive systems. A well constructed single-side drive system or single-motor dual-side drive system will perform extremely well in conventional plasma applications. The benefit of the extra precision offered by two-motor dual-side drive systems will not be realized in conventional plasma applications due to the limitations in the precision of the conventional plasma cutting process itself. Two-motor dual-side drive systems will provide the accuracy and performance required to achieve optimal results from a precision plasma process.

Sizing of the motors and gear boxes relative to the mass of the machine is also extremely important. Undersized motors and gearboxes will not be able to effectively change the direction of the mass of the machine at high traverse and cut speeds, resulting in un-uniform cut quality and washed-out corners. This not only affects the cut quality, but will also lead to premature mechanical failures.

The CNC control is the unit that ties together all of the functionality and features of the machine and plasma source. There are basically two classes of controls used on most of these machines today. Most industrial applications use industrial PC-based control systems such as those produced by Burny or Hypertherm. These units have user-friendly touch screen control panels and are housed in enclosures that can stand up to the harsh environments they operate in. Smaller machines of the hobbyist or artisan types often utilize standard PCs with I/O cards to control the drives and plasma systems. Industrial based controls are highly recommended for any application, are designed for industry specific requirements, are less prone to the typical PC problems, but can be cost prohibitive in smaller applications.

Another important, and often overlooked, feature to consider when selecting a machine is the construction of the rail system. Plasma cutting machines produce and reside in a harsh environment. It is therefore important that the components used in the construction of the rail system be robust enough to exist in this environment. All rail surfaces should be constructed of hardened materials and cleaned frequently so that they do not become pitted and gouged by the splatter of molten steel that will inevitably fall on them. Self-cleaning wheels are also a recommended feature to keep the wheels clean between regular preventive maintenance (PM) cycles. Sizing of the rails should also be robust enough to prevent deflection as the machine travels across them.

The combination of all of the above factors results in the precision and accuracy of a system. Unlike other mechanical machining processes, it is difficult to assign a standard tolerance to plasma cutting processes. Many manufacturers will strongly promote the fact that their machines have positional accuracy of +/-0.007 in. and repeatability of +/-0.002 in.. The fact is that just about any machine on the market can hold tolerances that far exceed the tolerance and capability of the plasma cutting process itself. There are many factors that will influence the cut quality you will achieve on your parts including: the characteristics of the part itself, power settings, consumables, gases used, material type, gauge/thickness of material, part layout on plate, etc.. Ask the manufacturer to provide you with cut samples of your parts or parts that closely approximate the parts you will be cutting, made on a machine/plasma combination that is comparable to what you are looking at. This will give you the most realistic representation of what to expect from a specific machine/plasma combination and the plasma cutting process itself.

Before talking to any cutting machine manufacturer, clearly identify your requirements:

  1. Identify the types of materials will you be cutting with your system (ferrous/non-ferrous, mild steel, stainless steel, aluminum, etc.).
  2. Identify the range of material thicknesses you will be cutting.
  3. If you will be cutting a variety of materials and thicknesses, estimate the percentage of each type and identify the primary types and thicknesses.
  4. Determine the size (length, width, and thickness) of plate you will be purchasing in order to properly size the table, effective cutting area, and weight capacity of your new system.
  5. You may also want to look to the future in anticipation of any future types and sizes of materials you may need to process. The upfront cost of anticipating these requirements may be substantially less than upgrading or retrofitting your system in the future.
  6. Identify the tolerances you will need to maintain. This will help determine whether you need a conventional or precision plasma system, as well as the type and construction of the base machine.
  7. Determine how many hours-per-day and days-per-week the machine will be operated. This will determine the type of base machine construction you will need, help estimate the cost of operation, and allow you to compare the cost/benefit of consumables life of various manufacturer’s power supplies.
  8. Determine how you will exhaust your equipment. Water tables do not require exhaust systems, but down-draft tables do. If there is an existing exhaust system in place, identify the capacity of the system in cubic feet per minute (CFM).
  9. Determine if you will need the flexibility to expand the system or add additional plasma and/or oxy-fuel cutting stations in the future. Some machines are capable of only carrying one or two torches, while others can accommodate slave stations for up to a combination of 10 plasma and oxy-fuel torches. Likewise, some machines have fixed cutting areas while others can be extended in length to increase cutting area or accommodate multiple cutting tables.
  10. Define the area in your facility where the machine will be located. Make note of any obstructions, hazards, or access points that will need to be taken into consideration when laying out the new system. Also, identify how your material will be handled in and out of the area (forklift or crane, aisle locations, etc.).
  11. Identify the power you have available, both voltage and amperage.

A reputable manufacturer should ask you for most of this information before making any proposals on a system. If a manufacturer does not have this information, they cannot adequately evaluate your requirements and propose a system that will best work for you and your specific application. Spending the time to identify your requirements up front will not only save you countless hours of frustration resulting from living with the wrong machine, but also save you money by not over- or under-buying a system to meet the requirements of your specific application.

Troubleshoot the SNR and Attenuation of Your DSL Modem to Fix Your Broadband Internet Speed

DSL Internet circuits may experience problems due to a variety of reasons. Most are related to the individual end user’s connection. And most can be detected through a simple check of Sync speed, attenuation and Signal-to-noise ratio (SNR) statistics on the DSL modem. This article will explain why these parameters are important, how to check them and how to improve the values.

It is always advisable to run a packet loss test on any Internet connection before an improvement project starts. The packet loss test should confirm that there is trouble at the end user’s connection and that the Internet Service Provider’s (ISPs) network is not the source of the trouble. In addition, the packet loss test will provide baseline statistics to compare future results against.

Assuming a packet loss test has revealed trouble at the end user’s IP address, it is time to look at the DSL modem and examine it for trouble:

Signal-to-Noise Ratio

According to Wikipedia.org, “signal-to-noise ratio (SNR) is a measure used in science and engineering to quantify how much a signal has been corrupted by noise. It is defined as the ratio of signal power to the noise power corrupting the signal. A ratio higher than 1:1 indicates more signal than noise.”

An everyday example of SNR is listening to music in your car over road noise or other people talking. The louder the radio compared to the other noise in the car, the more clearly you hear the music. The same is true for the DSL modem “hearing” the signal transporting the Internet traffic. When the signal is loud compared to the noise, Internet communication happens at a faster speed with less packet loss. When the signal is not loud enough compared to the noise, speeds slow down causing latency. Packets may be lost or discarded, creating retransmissions of data packets and trouble with real-time applications such as Voice over Internet Protocol (VoIP) used by Vonage, Skype and Hosted PBX providers. In fact, any real-time application will suffer including video streaming from Netflix, Blockbuster and others or any type of online gaming.

DSL Parameter Values

The values to check in a DSL modem are Sync, Attenuation and Signal-to-Noise Ratio.

Sync is described in downstream and upstream and is the connection speed in each direction. Downstream is from the ISP to the modem. Upstream is from the modem to the ISP.

Attenuation is the loss of signal over distance. The db loss is not just dependent on distance. It also depends on cable type and gauge (which can differ over the length of the cable), the number and location of other connection points on the cable. Attenuation is listed with both downstream and upstream values.

20db and below = Outstanding
20db-30db = Excellent
30db-40db = Very Good
40db-50db = Good
50db-60db = Poor and may experience connectivity issues
60db and above = Bad and will experience connectivity issues

Like Sync and Attenuation, SNR has downstream and upstream measurements.

6db or below = Bad and will experience no line synchronization and frequent disconnections 7db-10db = Fair but does not leave much room for variances in conditions.
11db-20db = Good with little or no disconnection problems
20db-28db = Excellent
29db or above = Outstanding

SNR will sometimes be displayed in margin or SNRM. This is the difference between the current SNR value and the SNR that is required to keep a reliable circuit at the connection speed. If the SNRM is minimal, the circuit is more likely to suffer intermittent connection faults and slowdowns. High margins are required to prevent bursts of interference from causing connection losses. The target SNRM is usually 6db but could be as high as 12db.

Determining the Values of a DSL Modem

Many DSL modem configuration pages can be viewed at the internal address of 192.168.1.254. Refer to http://broadband.modemhelp.net/dsl_modem_info/index.shtml and look up the specific make and model of the DSL modem or the manufacturer’s manual. The website or the manufacturer’s manual will give the modem configuration page address. Simply plug the address in a web browser of a PC connected to the modem and the page should load. Remember, these values can fluctuate. If intermittent problems are experienced, the values should be checked when all is well and compared to the values when trouble is experienced.

Improving the DSL Modem’s Values

Cabling and connectors are the most common cause of DSL problems. Internal wiring can easily be eliminated by simply plugging the modem into the Network Interface Device (NID) and unplugging everything else. The NID is usually located outside on a house or in an equipment room for a business. If the values do not improve to acceptable levels then the problem is with the modem or the ISPs infrastructure. Here are some things to try and look for:

1. Replace the modem.
2. Have the ISP verify that there are no load taps or bridge coils in their cabling.
3. Have the ISP verify that there are no T1 circuits grouped in the cable bundle serving the DSL (not likely to apply to residential).
4. If problems seem to be weather related especially during rain, have the ISP inspect and bypass any weather worn cabling or find better cabling pairs.
5. If none of the above is successful, have the ISP change the ports on the DSLAM.

If plugging the modem into the NID improved the values, then the problem is in the internal wiring. Check for the following:

1. Cabling from NID to modem is in good condition without any cable splices.
2. All telephone devices pass through a DSL filter.
3. Telephone jacks are in good condition and connectors behind the wall plates are solidly connected.
4. If the modem is plugged into a DSL filter, replace the filter.
5. If none of above is successful, unplug all telephone devices from the wall except the modem and check its values. If the values are acceptable, start plugging the other telephone devices back into the wall one at a time. Check the values as each device is plugged into the jack. When the modem values change back to an unacceptable range, the culprit has been found.

In most cases, the problem has been corrected by one of the items above. If the ISP has been involved, persistence may be required until a technician is found with the knowledge or customer care to fix the issue. Keep in mind, almost all Internet problems can be solved with determination and perseverance.