Hydrostatic Remote Control Lawn Mowers For Steep Hills

Remote Control Lawn Mowers For Slope Mowing Applications
Today’s popular zero-turn riding mowers are generally rated to safely handle up to a 30 degree incline without risking injury to the operator. A lawn care professional has to equip 5 or 6 of his crew members with profit eating string trimmers when it comes time to mow a client’s slope that is too steep to drive his equipment on. This has always been a problem for the professional lawn care provider as well as state maintenance crews working on the highway DOT (Department of Transportation) crews. With government officials raising the bar on safety regulations regarding slope mowing accidents, hills and banks over 30 degrees are being left unattended along portions of our nation’s highways and other government owned properties. Parks and recreation facilities are among some of the other properties affected by the new safety regulations.

The Summit Lawn Mower Company, based out of New Albany, Mississippi, has a rather new and interesting solution to slope mowing problems with their remote controlled mowers. By placing the operator out of harm’s way, safety concerns are not much of an issue. By not having a person on top of the machine, combined with an industrial grade rubber track drive system, commercial models such as the TRX-34PRO are able to achieve a very low center of gravity giving it slope mowing capabilities that are topping out at around 40-50 degrees while remaining practical. I do not expect to see these 34-60 inch robotic machines replacing the massive tractor mowers that the DOT guys need to maintain hundreds of acres along our highways. While their current line of commercial mowers are being used by lawn care professionals in mountain regions world wide, the company plans to release a hydraulic powered industrial line of mowers to cater to large area slope mowing that the state DOT departments just might be interested in.

Commercial Grade Remote Control Lawn Mowers Affordable For Homeowners
In addition to the track driven remote control lawn mowers only practical for commercial applications, Summit also offers zero-turn wheeled models that are practical for use around the house. Unlike the hydrostatic designs that use the engine for propulsion, these electric powered machines use high torque electric motors for propulsion utilizing an alternator that acts as an on-board generator to keep the battery charged while in use. As with the commercial models, the transmitter has two joysticks. One controls the machine in all directions while the other starts and stops the gas engine. This simple-to-operate design makes the ZTR series mowers popular with the elderly and disabled people who want to rekindle joy and satisfaction sometimes associated with maintaining your own lawn. While the track driven remote control lawn mowers have really impressive slope mowing capabilities, the ZTR series models are limited to being practical on 30 degree slopes due to their front end castor wheel design.

 

Pressure Basics – Air and Hydrostatic

Air compressors are relatively common machines that have practically become a household item owing both to its increasingly affordable price as well as the various functions it’s capable of performing from pumping bicycle tires to air-cleaning to the running of air tools. Loosely speaking, air compressors consist of a compressor unit which compresses the air and an air tank which stores the compressed air.

Various air compressors have different capabilities and run at different capacities, with the high-end ones naturally having superior specifications. Air pressure is built-up, with the upper limit of the given machine more often than not reflecting its price. Depending on the region, it is denoted by either pounds per square inch (psi), kilogram force per square centimeter (kgf/cm²), or megapascal (Mpa).

Standard air pressures generally range from around 0.7 Mpa to 3 Mpa. Many smaller DIY-type pneumatic tools, such as nail and staple guns, will run on 0.4 to 0.7 Mpa, whereas higher end professional-grade tools will require much more pressure. The standard SI measurement for pressure is the pascal, but some countries like the USA use psi. 1 Mpa is equal to roughly 145 psi, or 10.2 kgf/cm². This will help you convert pressure units into whatever you’re most familiar with.

Hydrostatic Pressure

This is the term used to describe the pressure a fluid exerts on its surroundings due to the force of gravity. Modern pipe lines utilize mechanical pumps to maintain a certain pressure within the pipes. This ensures that there is sufficient pressure when consumers turn on their taps. But hydrostatic pressure is fundamentally different in that it’s “natural” pressure as opposed to mechanized pressure.

Let Hydrostatic Pressure Testing Find Out – Can it Take the Pressure?

Hydrostatic Pressure Testing is a nondestructive testing (NDT) method of finding leaks or verifying performance and durability in pressure vessels such as pipe, tubing, and coils. Although this is considered nondestructive testing and failures are rare, they can occur when the test piece does not meet performance or durability specifications and may render the piece unusable.

Hydrostatic Pressure Testing usually entails filling the pipe, tubing, or coil with liquid, bleeding out air, pressurizing the piece, and then examining it for leaks or permanent changes in shape. A nearly incompressible (compressible only by weight, not air pressure) liquid, usually water or oil, is used to fill the test piece because it will only expand by a very small amount if the piece fails, and therefore, minimizes the chance of injury or further damage. Hydrostatic pressure testing also can be performed with pressurized air, but is generally completed with the vessel under water for safety reasons. Although a testing laboratory may be equipped to perform hydrostatic pressure testing with water, oil, or air under water, water is the most commonly used test medium because it is less expensive than oil and easier to set up than air under water.

This nondestructive testing method is used to test tubing, pipe and coils to pressures measured in PSI (e.g. to 10,000 PSI). The amount of pressure used in hydrostatic pressure testing is always considerably more than the operating pressure, or the pressure the vessel will be subjected to in the course of operation, to give the customer a margin for safety. Typically the test is performed at 150 percent of the design or working pressure. For example, if a pipe was rated to a working pressure of 2000 PSI, it would be tested at 3000 PSI.

Hydrostatic Pressure Test Safety Checklist

According to ASME Section VIII Division I, hydrostatic pressure is conducted at the pressure of 1.5 times design pressure. If a vessel is design for holding 1.0 kg/cm2.g pressure, the hydrostatic pressure test has to be done at 1.5 kg/cm2.g.

Hydrostatic test is also applied to existing equipments and pipe lines to check for leakage after being repaired or maintained. Hydrostatic job number increases during plant Turn Around period. Because at that time, most of equipments are opened for checking, inspection, clean-up, repairing, replacing certain parts or performing internal modification.

The use of high pressure is the main source of hazards associated with hydrostatic pressure test. Hydrostatic test stores energy. High pressure could damage the facilities and endanger worker’s safety. You should have included this into your own hazard identification.

Safety Checklist:

In order to prevent accident from hydrostatic test operation, we have to make good preparation prior to do the test, during the pressurization process and depressurizing operation. These jobs should be made in the form standard operating procedure. And here are the safety checklists for each stage.

Hydrostatic test preparation:

Specification sheet of the equipments and or pipe line, which mentions pressure and temperature designs are available and complete.

* Hydrostatic test pressure and temperature standard are already clearly defined in the related document.
* Supported documents such as P&ID and isometric drawing are available and conform to as built facilities at the field.
* Pressure test planning has to be distributed to all relevant sections in the plant site at least two days before the execution date.
* Make good coordination among related sections that involve in the test.
* All test equipments and tools shall be inspected for wear and damage.
* Pressure measurement tools are calibrated and their statuses of calibration are still valid.
* Pressure gauges used in the test have enough capacity. The gauges are recommended to have 150% of the maximum allowable working pressure.
* The pressure gauge is safety type, with blowout back.
* Pressure gauges must be installed at a proper location so that it can be easily read and do not create additional hazards to the hydrostatic test or expose personnels to the vessel being tested.
* All the temporary tools (such as valve, fitting, hoses, flanges, blind plate, etc) have to be rated more than the maximum hydrostatic pressure.
* Isolate other equipments and pipe lines that do not include in the hydrostatic test.
* Vents are available and installed the high points to vent air. Check the vent line before testing and make sure it is not blocked.
* Choose drain valve at the lowest point in order to completely empty the vessel and pipe.
* Safety relief valve is already installed. Safety relief valve setting is 1.5 times maximum allowable working pressure.
* Safety relief valve is calibrated.
* Isolate the test area and surround it with safety line. Put appropriate safety sign at that area.
* Do not allow person who does not have any relation with the hydrostatic test, to enter the test area.
* If possible perform the test from a remote area.
* Make sure that all pipe and vessel supports are in good condition and have been inspected.
* All hoses must be tied down.
* Water temperature must be more than 16oC (60 F).
* The hydrostatic-pressurizing pump is completed with safety relief valve.
* Wear proper personal protective equipments.
* Do not start the test if a problem is identified.
* Issue a work safety permit by authorized personnel.

Pressurization process:

* Remove all air from the vessel and pipe line by water through vent line.
* Pressurization is conducted gradually/slowly.
* Mark all leak points and repair them before preceding the test.
* Do not monitor during pressurization step directly from the front of sight glass or level glass.

De-pressurization process:

* Start de-pressurization by opening gradually the vent valve. Do it slowly.
* Do not open the drain valve if the vent valve if still closed. This is to avoid vacuum condition inside the vessel.
* Open the lowest drain point to completely remove water from the vessel and pipeline.
* Ensure that no remaining pressure trapped inside the pipe line or vessel.

The above hydrostatic pressure test safety checklist will ensure worker’s safety and the facility of the plant. Thus, do not try to ignore them.