Thursday, April 30, 2009

Electrical Safety - Grounding continuity

When you think that your lighting batten is inherently grounded, you may want to check that it really is grounded. Modern rigging systems use Nylatron (plastic) pulleys and the counterweight carraige arbor shoes may be Nylon, leaving the only electrical path back to the safety ground as the ground wire in the SO power cable or flexible conduit that feeds your plugstrip or plugbox. If the fixed conduit or flex conduit body is the only ground path you have, then the ground is broked (open circuit) if the conduit becomes separated.

The same is true if your ground lead on a lighting instrument becomes disconnected. This can happen several ways:
  • A two wire connector (an old style two-pin 2P&G stage plug or a two-bladed Edison plug) is installed on a three-wire cable
  • A ground-lift adapter is installed on the end of a normally grounded NEMA 5-15P connector
  • The wire breaks internally
  • The wire gets yanked-out of the connector body
  • The wire gets yanked out of the lighting instrument body

In any case, you are in a situation that would let the fault current of an internal problem in a lighting instrument look for another path back to the source, and that path may be you!

Wednesday, April 29, 2009

Electrical Safety - Equipment Maintenance

Most stage equipment that uses electricity has a power cord with a (male) plug or (female) receptacle on one or both ends of it. Maintaining those connections is vital to both the operation of the device and the safety of those using it. Below is the back-end of a stage lighting instrument that has the cable strain relief missing, which in-turn allowed the inner wiring to become frayed and short-out to the casing. Here is a cable end plug that was hurredly assembled to get it working for a show, but the cable clamp (strain relief) was never tightened-down to take the stress off of the inner conductors.
Here is a 2P&G cable end that was not properly secured to the outher sheathing of the stage lighting instrument cable, and over time it frayed apart.
The same thing can happen to extension cords, twofers, and just about any other cable connection. When you find these types of equipment damage, the best thing to do is red-tag the equipment as non-usable, and submit it to your repair shop for correction

An ounce of prevention
In general, the root cause of these types of connector failures is due to people yanking on the cable instead of grasping the plug body when they remove them from their mating device. Take care of your equipment and it may not seek revenge by failing at five minutes to eight, or worse yet, shocking you to get your attention.

Tuesday, April 28, 2009

"Allright Bugsy, it's curtains for you."

Drapes and other soft goods used on the stage must be treated with a chemical fire retardant or be fabricated from an inherently flame proof material. When the manufacturer creates the product they should tag it so that there is a record of the date of manufacture / treatment, and retreatment, if any. The label shown above is a good example of that type of marking.

So, what's wrong with this picture? The date of manufacture is 9-15-76. This picture was taken in March of 2009, and the curtain was still in use! 33 years later!

The chemical fire retardant treatment applied to theatrical fabrics is typically only good for 2-5 years, depending upon the heat and humidity that the fabrics have endured over their service life. Soooo, this curtain was, shall we say, waaay past it's useful working life.

Check your curtains, see that each one has a serial number or unique ID marker, has a tag showing date of manufacture (not date of installation or first use), and lists the name of the chemical treatment that was applied.

Keep separate records that corrispond to each soft good so that you can schedule and budget for periodic cleaning and service. This is a great use for any computer based appointment or calander system (like MS Outlook). Enter the date of manufacture as an 'appointment', and then set the recurrance for every "X" years (as recommended by the manufacturer). The computer will remind you of your appointment when it rolls around, just like a birthday or a dentist appointment.

Monday, April 27, 2009

Theatre Safety - Where to start with the students?

"In the dark the innocent can't see." - Melissa Etheridge. Theatre Safety for the very young starts with hazard recognition. The younger the student, the less aware they are of potential dangers around them. One of the first dangers a child learns is thermal. Start there with stage lights.

You can expand your Fire & Emergency Training to have fire exit drills in the middle of show rehearsals. Start out easy and get them to understand that getting out of the building is a priority, then later you can 'complicate' their decision making by making them find and take a different route by declaring the 'obvious' or 'regular' route as "not available." People tend to exit buildings the same way they came in. You have to challenge them to find and know alternate routes should their typical or normal one be blocked.

Respect for property and others is also an important safety item. Students that 'tear things up' and harass others can be a danger to themselves and others. They are frequently the ones that don't listen to instructions, distract others so they can't listen, and go climbing or pulling on things that may fall down. These students go on to disrespect property and can damage important safety systems.

Don't just say "NO!" Explaining to the students why and how signs, ladder guards, PPE, and other safety equipment is there to protect them helps them understand why damaging that equipment may injure themselves or others. Actions have consequences. So do inactions.

Curiosity killed the cat. Although most elementary schools don't have counterweight rigging systems, it is still a good idea to familiarize the students with what they are and how they work. They have to know what the equipment is and see the potential danger so if they are visiting another venue that has that type of equipment, they don't reach-over and release a rope lock 'just to see what it does.'

From there you can start working on tool safety. Most kids never get any real instruction on basic tools like hammers, screwdrivers, pliers, and wrenches. If they can use it, they can misuse it. First-up is keeping the work space clear of nails, tacks, screws, splinters, and trip hazards. From there, go through basic tools like hammers (here is a good chance to show them why they should always be wearing safety glasses around anyone stapling or nailing. Show them how far a nail or staple can go when it ricochets - that's always an eye opener (not to be puny). Kids like "gross" - get a cow eye from the biology teacher and poke a nail through it - eewe!

Painting can also be hazardous. Help the students understand the difference between oil-based paints, latex-based paints, and water based stage paint (Green-ness, chemical hazards, clean-up hassles, skin damage, fire retardancy, etc.). Get them to wear gloves to protect their hands, safety glasses to keep the paint splatter out of their eyes, aprons to protect their clothes, knee pads if they are working on the floor (to protect them from jamming-up their knee-caps with a nail or screw someone left behind).

1000 ways to die. For each tool there is a correct way to use it, and a thousand ways to misuse it. Tunnel vision. Show them what can happen when you don't see past your work-surface (what is behind the board, under the flat, around the corner) or surroundings.

As you approach each task of building a set, or moving it, or striking it; challenge them to think about safety. Is there a safer way to do this? More people, better tools, different PPE...

And of course, keep a record of each student's training and skills. If they injure themselves or others later, it can help to know what they were permited to do verses what they took upon themselves to do.

Saturday, April 25, 2009

"We don't have to get it inspected, do we?"

That is a common whine I hear from theatre owners / facility managers all the time. Sometimes it's followed by "We're exempt!" Really? Where does this drivel come from?

The Occupational Safety and Health Administration (OSHA) publishes a standard for the use of industrial winch and hoist machinery. That is Stage Rigging Equipment to you and me.

OSHA “29 CFR 1926.550 Cranes and derricks,” paragraph (a)(6):
“A thorough, annual inspection of the hoisting machinery shall be made by a competent person, or government or private agency recognized by the U.S. Department of Labor. The employer shall maintain a record of the dates and results of inspections for each hoisting machine and piece of equipment.”

You can’t get much clearer than that.

"Hoisting machinery" is anything that hoists. It does not have to be motorized.

I cannot find anywhere in the OSHA Regulations that exempts any school (public or private), church, municipality (State, County, City, School District), or non-profit organization (i.e. community theatre).

It’s up to facility owners to be sure that stage rigging equipment is in top working order. The inspections are intended to protect the staff, students, and guests from using mis-designed, mis-installed, damaged, or worn-out equipment. Inspections can also shield the institution from potential lawsuits should there be an accident, and it can prevent the assessment of fines should there be an OSHA inspection. Yes, you can be fined by OSHA just for not having a record of the inspections, let alone not actually having the inspections.

A "competent person" would typically be either a Theatre Consultant or Stage Rigging Company that has experience in this area. The person doing your inspection should, however, be looking at the big picture when they come into your facility. I frequently find recently installed or recently inspected stage rigging systems that have gross violations of other safey codes immediately adjacent to the rigging equipment, and discover that no one had mentioned or reported those conditions when filing their final reports.

If it involves safety, "NOT MY JOB" can't be used to side-step the issue. You see it. You report it. Period.

Friday, April 24, 2009

Weight, weight, don't tell me...

Why is it that EVERY rigging system I see has loose, missing, or missapplied weight locking collars? These are the easiest thing in the world to use! My advice: Check, check, and re-check. If your fly crew won't use them, dismiss them from the fly rail.

The weight lock collars at the left are 3-4 feet above the top counterweight, and the ones on the right are probably 15-18" up.

That won't keep the counterweights in-place should you have a stage-heavy run-away. The arbor hits the top stop and inertia lets them keep on going . . . until gravity overcomes the flight pattern and it comes crashing down to the floor below; probably bouncing and boinging off of the adjacent metal, rope, and cables all along the way. Talk about an uncontrolled and unpredictable ballistic missile!

Here is what can happen when the weight hits the floor:

The force of the impact broke-off a 2" thick piece of steel! Imagine what would happen if it struck someone on the way down! Even an OSHA required ANSI standard hard-hat wouldn't help you.

Of course, stacking the weights on top of the weight locking rings won't help either . . .

So what else could we do wrong? How about no thumb-screws in the locking collar . . .

Or maybe use a U-Bolt to clamp the weights in place (note the rear clamp has slid down into the back fork of the weight).

Counterweight Locking Collars.

Use 'em!

Thursday, April 23, 2009

Skin Shredders - Things that cut you in the dark.

Junction boxes, like the one shown above, abound in theatres. Unless there is some structural problem with embedding the box flush in the wall, surface mounted boxes should not go into new construction. However, when they are installed, the contractor that provides the cover plate should see that it is fabricated with a cover plate that matches the face dimension of the back-box.

Retrofit Recommendations:
  • If possible, have an electrician remove the plate and take it to a metal shop to have the excess metal sheared-off and the edges ground smooth.
  • Replace the plate with a new on that is properly sized (and some good labelling would be nice, too!) Custom plate fabrication is not very expensive. Draw what you want and dimension it, including the mounting screw holes and engraving, and get a quote. Now is a good time to add connectors, relable circuit numbers, and even change the color of the plate. Black may be good for the upstage wall, but for just about everywhere else that the audience can't see, white is much easier to find and read in the dark, particularly in floor pockets.
  • If the plate can't be modified or replaced, then install hardwood blocking around the box so that the perimeter of the wood framing is slightly larger than the exposed metal cover plate. Routing a recess in the face of the hardwood frame to make the face of the plate flush to the face of the wood perimeter is also recommended. Note: Don't drive screws into the box sides, as they can pierce the insulation on the wiring within the box. With the power disconnected, install the screws into the wood from inside the box.

Another place that frequently has surface-mounted back-boxes are catwalks. These may be single or multi-gang back-boxes that were designed for flush mounting but were installed along an open railing. The standard sized gang cover plates that are then installed for DMX, Microphone, and Intercom receptacles, or light switch cover plates, are over-sized and leave sharp corners exposed to snag and cut.

Wednesday, April 22, 2009

Stair Safety - It's All About Contrast Ratios

As our population ages and gets poorer eyesight, the ability to see subtle changes in surfaces before us, particularly in dim light, is diminished. This is a good example of stairs that have no clear transition point. Recommended solution: Install a contrasting color tape or paint strip along the edge of the steps. There are many 'stair tread' or 'grit tape' products out there that are designed for direct application to floors. Just remember to strip the floor of wax and dirt before you do it, otherwise you'll just be creating another hazard in place of the one you just resolved. There are also grit tape strips and paint that have photoluminescent glow-in-the-dark strips in them, which can help in the event of a power outage.

Where this situation occurs on carpeted steps, there are two possible solutions:
  • Recarpet the stairs with a two-tone carpet scheme so there is a contrasting color strip for about 2" along the step nose, or
  • Add a grit covered metal or fiberglass strip that is screwed-down over the carpet and crushes down the carpet so that the top of the strip is even with the remainder of the carpet so there is not a trip hazard.
A solution I have seen that is NOT recommended is laying down a strip of white gaffer's tape. Although well-intentioned, it can work loose and create a trip hazard.

The strip color should contrast the carpet color in low light. Our vision tends to loose the color component in low light conditions, so an easy way to test this is to view the proposed color combination with a black and white video camera or still camera that is slightly out-of focus. If all you have is a color camera, then take the picture and pull the color saturation out of it with a photo editor. What may appear to be a good color combination to youthful eyes in full light, may indeed not be a good solution when viewed as an elderly color-blind person.

Another issue at this location is that the railing does not meet the 4" sphere rule to prevent children from falling through the railing bars.

From an audience focus perspective, the railings in front of the seating should be a dark matte finish so as to not distract from the focus of the game (this is more important in live theatre and cinemas). The railing at the end of the flight of stairs should contrast the background (in this case, the basketball court), so that it's distance is not misjudged.

Other listing of interest:

Tuesday, April 21, 2009

Theatre Design - Why is this column in the middle of the stage?

And then there is the light spill on the projection screen and the bright surroundings that encompass the screen . . . . someone forgot that the presenter / presentation is supposed to be the focus of the audience.

Monday, April 20, 2009

A Long Way To Fall - Ladders Without Cages

This is a legacy ladder which was installed before OSHA even existed. However, that does not exempt the owner from correcting the situation. Ladders of this height must have an ANSI standard cage around them and a fall protection device installed.

Fall protection can be provide in two ways:

a.) There can be a continuous cable or track that runs the length of the ladder (usually up the centerline) with a special trolly attachment that ties to the front of the worker's fall protection harness.

b.) There can be a retractable fall arrest lanyard secured above the top of the ladder way that attaches to the back of the worker's fall protection harness.

Since the worker has to transfer backwards from the ladder onto the catwalk near the top, the retractable fall restraint would probably be the safer solution. Otherwise, the worker would be required to attach a secondary lanyard to the catwalk fall protection anchorage point before he could disconnect the front trolley and he would have to do that while standing on the ladder.

At the top of the ladder you can see that there is a fire sprinkler pipe crossing the travel path of the worker. This would have to be repositioned to provide proper clearance for the ladder cage. Right above the sprinkler pipe is the end of the Loading Gallery catwalk, which would also have to be moved back to allow a clear passageway. Fortunately, I had on my hard-hat when I climbed this ladder -- when I reached the sprinkler pipe I hit my head hard enough to dislodge the inner suspension. Had I not been wearing the hard-hat it could have knocked me out or made me lose my grip on the ladder.

A secondary problem with this stage design is that a full fly house really should have a Lower Loading Gallery in addition to the Upper Loading Gallery. The Lower Loading Gallery is typically situated about 10-12 feet (~4m) below the Upper Loading Gallery so that weights can be added / removed from the counterweight carriage (arbor) when the batten is about the height of a backdrop and/or scenery flat.

Of course, once the ladder has a cage around it and the end of the catwalk is repositioned, it will need a safety gate at the catwalk to keep someone from inadvertently stepping-off into the open hole. Something like this (from a different facility):

If you look closely you will see several interesting items in this picture:
  • On the left side (on stage), there is a railing that meets the 4" sphere rule (as if there was going to be a baby crawling around up there !? I guess they figured it was OK if the baby crawled under the safety gate . . .). There should be a steel plate or mesh that extends up about the 18-24" level to prevent the unused ( stored) counterweights from spilling over onto the stage floor below. Also note the 'stored' counterweight left along the off-stage side of the catwalk as a trip-hazard.
  • The on-stage side railing is also about 40" tall, enough to keep you from falling over it. A 42-48" railing would be more appropriate here.
  • On the right side (off stage, toward the counterweight arbors) there are railings at 8", 24", and 40". Just enough of them to keep you bonking your head as you try to man-handle the counterweights. There is not any OSHA required fall protection anchorage to allow the worker to wear a fall protection harness and safely lean-over the railing and do their work.
  • The floor of the Loading Gallery is fabricated from open pattern bar grate, which acts like a cheese grater on your knees when you kneel down on it. It is also open weave, so any grit on your shoes gets scrubbed-off and drops onto the crew working below you. A better solution is to have a closed floor decking (sheet metal) that has a dense rubber mat on it. This provides a non-slip surface, is quieter when setting-down counterweights, and keeps the grit from raining down on those below.
  • And the coup de grĂ¢ce is that there is not an Index Strip Light at this level, so you are working in the dark (all that light you see is from the camera flash). There wasn't any emergency lighting packs either, so if you get caught up there in the dark, good luck getting down!
As a side note, it is always good to paint the working surfaces facing the catwalks a light color like white. This is good for floors, railings, uprights -- everything. If the masking drapes are all properly positioned, no one will see the catwalk from the audience seating area. Place glow-in-the-dark marker tape along all gate and floor openings so you can find your way out in the event of a total power failure.

Sunday, April 19, 2009

Theatre Safety Presentation at TETA Summer Workshop

"How NOT to Break a Leg" at 11:15 AM, Friday, July 10, 2009.

TETA K-12 Summer Workshops will be held at Stephen F. Austin University in Nacogdoches, Texas. The Theatre Safety Workshop will be held at the Auditorium at Nacogdoches High School, about a 10 minute walk from the SFA campus.

For more information about TETA Summer K-12 Workshops go to:

Friday, April 17, 2009

What's wrong with this picture? - Electrical

I found this disconnected conduit joint where the insulation on the wiring within had been cut by the edges of the metal and caused some arcing. This is a fire hazard that is intermittent - sometimes the circuit breaker would trip, sometimes it wouldn't.
Recommended resolution: Have a qualified electrician reconnect the conduit and secure it with conduit clamps, then replace the wiring.
Note that there are only two conductors (assumed to be the hot an neutral). This also exemplifies why it is a good practice to require that safety grounding conductors be installed in power conduits and not to rely on the conduit system for a continuous and uninterrupted ground path.