Automatic Gate Installation

An operator adds a machine to a gate that already has to carry its own weight. A frame that sags, a hinge worn oval or a footing that has shifted shows up faster once a motor pushes it every day. We square the frame, brace the span, rebuild or upsize the hinges, and weld a mounting plate that puts operator load into the frame instead of the infill.

UL 325 sorts vehicular gate operators into four usage classes, and the class decides what equipment belongs on the gate. Residential sits at one end and guarded restricted access at the other, with commercial or multifamily and industrial in between. The four definitions are in the table below. The class follows the property, so a small gate on a five unit building is Class II.

Entrapment protection is the heart of the UL 325 provisions for gate operators. For most installations UL 325 requires two independent entrapment means in each direction of travel, and for all installations two are required in each direction where a risk of entrapment exists. One is usually inherent to the operator, which senses force and reverses. The second is external, a photo eye or a contact edge. Under UL 325 reversal has to begin within 2 seconds.

An entrapment zone is a gap, measured between moving and fixed steel. Under UL 325, by way of DASMA Technical Data Sheet 350, a gap between a moving slide gate and a fixed opposing edge or surface counts as an entrapment zone when it measures less than 16 inches at any point in travel, up to 6 feet above grade. That figure marks where a gap needs protection, not a clearance the gate must leave. On a swing gate the pivot end has a zone too, easy to overlook behind the leading edge.

External entrapment devices are monitored, all of them, and the operator checks that every device is present at least once per open and close cycle. We weld sleeves through the frame so sensor wiring runs inside the tube instead of strapped to the outside, since a crushed cable is a common reason a monitored device faults.

Speed is capped in one specific case. Slide gate operators for Classes I and II, and vertical lift gate operators, cannot exceed 1 foot per second when the operator is pulling 75 pounds or more. That is UL 325, by way of DASMA Technical Data Sheet 353, and the load condition is part of the rule, so the figure does not convert into a travel time for a given opening width. UL 325 sets no speed limit on swing gates.

How the gate itself is built is covered by ASTM F2200. A gate must not fall more than 45 degrees from vertical if it comes off its supporting hardware, which is why stops, keepers and catch brackets get welded on rather than left to the roller to hold. ASTM F2200 bars protrusions on an automated gate, with a short list of exceptions the standard names itself. A manual latch falls outside those exceptions, so it comes off and a receiver guide is fitted in its place.

Slide gates carry more rules than swing gates, and under ASTM F2200 the screening provisions apply in full on Classes I, II and III. Weight bearing exposed rollers 8 feet or less above grade get guarded. The gate, and the fence it covers when open, has to be screened so a 2.25 inch sphere cannot pass, up to 72 inches above grade or the top of a shorter gate, and the gap to the nearest fixed object stays at 2.25 inches or under. Positive stops go at both ends of travel. Class IV is treated differently, since those sites put security ahead of the safety provisions.

UL 325 requires a minimum of two warning signs displayed in the area of the gate, visible from both sides of the gate opening. A vehicular operator is never used on a pedestrian gate. The standard is not retroactive, so an old manual gate can stay as it is, but motorize it and UL 325 applies from that day.

Hot dip galvanizing under a powder topcoat is a duplex system, and the American Galvanizers Association publishes that it lasts 1.5 to 2.3 times the two coatings added together. Powder over galvanizing needs the prep in ASTM D7803, which adds a thermal step that keeps pinholes out.