Pros and Cons of Barriers
Which is “greener” is not an open-and-shut case
When specifying the vehicle access control system needed to
stop a truck-bomber, errant driver or vehicle that is not authorized
to enter your facility, you have to decide among
bollards, barriers or barricades. Once you have decided the
type you will use, you then must specify which model. Finally,
you need to select the type of power unit you are going to deploy as going
green is important to many companies and organizations worldwide who are trying
to minimize their carbon footprints.
The two most popular choices are the hydraulic and electro-mechanical power
units. How do you decide which to use? The following should help.
Plusses and Minuses of Hydraulic
The hydraulic controller is the workhorse of the industry. This unit is typically
mounted remotely from the barrier(s) and attached to them by hoses or steel pipes
buried underground. It is powered from a local single or three-phase power source.
Buried lines. A big plus is that while hydraulic lines are buried, the motors are
kept above ground (“above grade” in contractor parlance); therefore, there are
fewer environmental problems than with an electro-mechanical motor, which is
placed below ground. With a hydraulic controller, there are no problems of a motor
sitting in a pool of water or being swallowed by mud.
Stronger forces. The hydraulic power unit is stronger, with forces generated in
the range of 20,000 to 25,000 pounds. An industrial-grade electric motor drives
the hydraulic gear pump to produce the hydraulic power unit system pressure. If a
normal-sized car ends up on top of the barrier while in operation, the barrier will
continue to rise and pick up the vehicle. This is a very effective deterrent at times,
when vehicles decide to run the barrier or tailgate the vehicle in front of them.
Reliability. Hydraulic controllers are reliable and there are few maintenance issues
when installed properly. The biggest complaint about them comes from environmentalists
and organizations with a green initiative. However, petroleum-based
oil does not need to be a concern. Instead, customers can simply substitute biodegradable
oils, usually derived from cooking oils. In fact, more than 50 hydraulic
barrier, barricade, bollard and crash gate designs can be run manually or on FDAapproved
Temperature. Cold can be a problem with hydraulic power units in locales with
frigid weather because oil can become thick; however, this is easily solved at the
time of installation by adding heaters to maintain proper oil viscosity. Depending
on the hydraulic power unit size and rating, such heaters will range from 60 to 500
watts at 120/240 volts for oil reservoirs. Of course, the hydraulic hoses to the barriers
should be run below the frost line, where temperatures are a relatively constant
45 to 55ºF. If desired, the ducts carrying these hoses can be heat traced at the time
of installation, as well.
Barrier installations, in areas where the temperatures are frequently above
100ºF, typically are equipped with oil coolers or have their hydraulic power units
located inside temperature-controlled equipment rooms.
Plusses and Minuses of Electro-mechanical
There are some unique locations where the application may not lend itself to
hydraulic units. As mentioned, for environmental reasons, some locations won’t
allow oil or wish to use a bio-degradable substitution. In other cases, the application
simply demands a simpler, less complex solution. These locations use the
Variable speeds. With an electro-mechanical unit, the customer can produce
variable speeds, having more control over the rapidity of how quickly the ramp
or bollard rises. For instance, many users like to initially raise the ramp or bollard
quickly and slow down near the end, which is easier on the system. The electricalmechanical
unit is also quieter than the hydraulic alternative.
Maintenance. Most security professionals find the electro-mechanical unit minimally
easier to maintain, although that slight difference is rarely given for choosing
one over the other.
Temperature. Electro-mechanical units handle all temperatures without problems.
Below ground. The biggest negative for electro-mechanical units is that they
are buried below ground (“below grade”) because they can become submersed in
water or mud, creating a major maintenance problem. Therefore, when selecting
an electro-mechanical power unit, it is imperative that the contractor create good
drainage at the time of installation. Care should be taken to mount the barrier
in an area that is not subject to flooding. Additionally, the roadway should be
crowned in the area of the barrier to prevent standing water from draining into the
barrier’s foundation frame.
Power usage and draw. Electro-mechanical units require at least 220v/single
phase power and draw approximately 20 amps. This is typically 12-15 more amps
of power than what the hydraulic power units draw, bringing into question whether
they are greener than hydraulic units.
When planning to install a bollard, barrier or barricade, don’t treat the choice
of your power unit lightly. If you don’t understand something,
ask; then ask again, if needed. And, always work with a contractor
who is experienced with this type of equipment, asking your
manufacturer for suggestions.
This article originally appeared in the November 2014 issue of Security Today.