Friday, May 29, 2009

Fire on the line!

Fire sprinkler pipes, heads, and other fittings are not for rigging, attaching flags, banners, or anything else.

Wednesday, May 27, 2009

Ladder, ladder, on the wall . . . how many ways can you make me fall?

This ladder may have been 'legal' when it was installed (probably circa 1951), but it doesn't meet today's ANSI / OSHA standards.

For starters, access is on a platform that is about 8 feet above the stage (not visible, but off to the left of the ladder). There is no railing along the edge of this platform. To correct this situation (other obstacles to come, stay with me), a safety railing would have to be installed to protect the worker on the platform, then a cage would have to be installed to enclose the ladder. Since the ladder is almost adjacent to the railing, additional guards would have to be installed between the top of the railing and the bottom of the ladder cage so that the worker could not fall over the railing as they climb the ladder.

Note that there is also a wire-guided line set intruding into the climbing space of the ladder.

The next thing that is encountered is the opening through the proscenium wall. A platform is required here so that the worker can enter the door without hanging off of the ladder.
  • Side note: The door was found open, thus violating the fire wall integrity. This door is a 'shorty' - its only about 48-50" tall. They built them that way to meet the square footage requirement for penetrations through the fire wall. Curious, as there never was a fire curtain installed to separate the stage and house - why would they worry about the size of the fire door?
  • Second side note: On the other side of the fire door there was a light switch to illuminate the attic catwalk, but if you didn't know this, you would enter in the dark to find a 2 foot wide catwalk that turns immediately left. This catwalk has no guard rail or toe boards, beyond which was about a 20-25' drop down into an interior wall void that goes all the way down to the auditorium floor level. If you fell down in there they wouldn't find you until your body started to stink-up the place. Don't fall in on the last day of school - you'll be there all summer! Did I mention that all of this was fully accessible to the students?
  • Third side note: There was no grab-rail or anything to get a hold upon as you climb off the ladder into this 'shorty' door way - you have to reach in blindly and get a grip on anything that you can feel for - that was scary. Climbing back out of the door to get on the ladder was 'fun', too!
So, assuming you have added the requisite landing at the attic access door level, you now have to get up to the gridiron level. The existing ladder over-hangs the access door opening on the right, and runs into the headblock beam on the left. Time to re-group and think this over.

Plan B: Lets put the ladder to the right of the door, far enough off-stage that you can go past the electrical conduits with the proper clearance. This way we don't need the railing-to-ladder-cage filler panels, and we get out of the way of the wire-guided line set. We would have two platforms: One at the access door level, and one at the gridiron level. Of course, both platforms will require proper railings.

When you connect the platform to the gridiron you find that there is no railing along the headblock beams. (Imagine climbing the existing ladder, working your way around the off-stage headblock beam, over the loft well between the headblock beams, only to find that the gridiron was built with 2x6's set on-end with about 6" gaps between them. So much for having a good footing and a 'non-combustable' structure . . .)

Oh yeah, did you notice that there was NO loading gallery? Need to add one of those, too. Looking at the picture you can see that a loading gallery floor would likely encroach into the platfrom area for the attic access door. Dang! Wuddle we do?

We could use all motorized line-shaft rigging, but that is a fairly expensive solution. The saving grace is that the facility is now a 6th-grade only school that does not have a theatre arts program. The wire-guided rigging system was pretty well shot, and all the drapes need replaced, so the movable rigging will probably all go away and the battens will be dead-hung. The facility still needs a proper ladder access to the attic and gridiron, but at least it won't need a loading gallery, too.

One last note: Did you see that 2x4 fluorescent light fixture bolted to the bottom of the wood 'gridiron' joists? There were about a dozen of those that need to be serviced . . .

Saturday, May 23, 2009

Exit, stage right

The National Fire Protection Association (NFPA) Life Safety Code says, and for good reason, that you can't block or lock theatre exits during periods of occupancy. Doors, if equipped with latches and / or locks must be readily operable by anyone needing to exit the building.

The picture above shows a locking bar that was installed up-side-down (note the "Lift Up" text):

The locking bar is pinned in place by TWO hairpin cotter pins (one visible at each end).

And the right leaf has a dead-bolt that pins into the floor at the bottom (which probably would not be visible should a crowd of people rush the door)

Additionally, the signage applied to the door should be worded:
NOTICE: This door shall remain unlocked during occupancy.

Thursday, May 21, 2009

Skull Scrapers

The meat on top of your head is pretty tender, all jokes about 'thick-headed people aside. This is why wearing an ANSI standard OSHA approved hard hat around a theatre is a really good idea. Catwalks are notorious for low hanging steel and sharp edges.

The following picture shows a steel ladder that was mounted away from a wall, but the steel tab for the wall attachment was left intact. As you can see, someone walking around backstage in the dark could very easily run into this. Padding and marking aren't really an option here -- time to get out the cutting torch or hack saw and completely eliminate this hazard! Remember to grind the remanants smooth if you cut something off of the vertical railing of a ladder, otherwise you are creating a great way to slice someone's hand as they use the ladder.

Here is a home-brew solution to some protruding beams along a loading gallery. Glue some foam pipe insulation over the corners.

Use your noggin for thinking, not bonking.

Monday, May 18, 2009

Doors through fire walls

An all too common sight around theatres is doors propped-open with counterweights from the stage rigging system.
Occasionally they are propped open with other things, in this case: a flag pole base. Sometimes fold-down door props are added to the door: And I've seen doors held open with bailing wire tied-off to a nearby object.

Other common fire door violations are taping over the door strike (latch) so that it won't keep the door closed against the atmospheric pressures generated by a fire.
I've also seen automatic closure devices disabled or removed so that the door won't be pulled closed.
The reason you should not do this is simple: The walls around the stage, and dividing other major portions of the building, are fire-rated partitions, typically rated for about 2 hours. The doors that penetrate the fire walls are also fire-rated. If there is a fire in the building, the doors act as a fire barrier AND as a means to cut-off the flow of air to the fire. If the door is propped open, it cannot protect the occupants or the building.

Below is a common solution to this problem: Notice the two small devices near the top of the doors and along the walls flanking the doors. These are electomagnetically operated door holders. They are deactivated by a switch on the wall so that the doors can be closed, and they are automatically deactivated by the Fire Alarm System in the event of a fire.

Teach your students and staff about Fire Doors and make sure that they don't disable or bypass this valuable feature just for the convenience of reducing door opening and closing tasks.  If the door is mechanically loud and clunky, look at having the mechanism(s) repaired or replaced; and teach your crew how to go through a door stealthly, like a ninja!  Not everything requires brute-force!

Thursday, May 14, 2009

Wire rope cable termination gone wrong - very wrong

(Sigh) What can I say that this picture doesn't? Obviously, the proper way to terminate a wire rope was not in this person's skill set. Good intentions mean little if someone gets injured due to a rigging failure.

  • Know your load.
  • Know your cable strength.
  • Know how to apply a safety (design) factor for live loads vs static loads.
  • Know the efficiency (derating) of the termination method (Crosby's are different than Nicopress).
  • Know how to install a cable thimble.
  • Know how to terminate it for maximum safe load carrying capacity.

If you use cable clips ("Crosby's"):

  • Know how to install them ("Never saddle a dead horse" means don't install the forged cable grip over the unloaded tail of the cable).
  • Know how many you need.
  • Know the spacing required.
  • Know the torque of the bolts/nuts and use a torque wrench to achieve it.

If you use crimp-on sleeves ("Nicopress"):

  • Know how to install them.
  • Know how many you need.
  • Know the spacing required.
  • Know which axis of the compression oval is to be crushed (crimped).
  • Know how to check and adjust the crimping tool so the die properly siezes the compression oval.
  • Use a Go / No-Go gauge to check your finished crimps.

{Photo courtesy of 'Curiousbrandt' on Flicker}

Wednesday, May 13, 2009

Cable Bending Radius

Wire rope, like all flexible cables, has a limit as to how sharply you can bend it before it is permanently deformed. This is called the d:D ratio. It is the ratio of the diameter of a sheave to the diameter of the cable. It depends upon the stranding and lay of the rope, and it is usually in the range of 20:1 to 40:1. This ratio is for maximizing the life of the cable as it flexes repeatedly while it transitions from straight to curved and back to straight as the cable passes over the sheave.

For a 1/8" diameter cable, not typically used for stage rigging, but frequently used for operating smoke vent hatches, this would typically use a 4" diameter sheave (32:1 d:D ratio). The picture below is a 1/8" diameter cable that operates a smoke vent. You can see that it is bent under tension over the sharp edge of a steel I-Beam with no pulley or block to smooth-out it's travel around the corner. You can also see where the cable strands have broken due to repeated operation.

So, why is this important? The smoke vents should be configured to allow both manual opening and closing and for the automatic release in coordination with the Fire Alarm and the Fire Curtain systems. It is very typical (but shouldn't be) that the Smoke Vents are rigged by someone other than the Stage Rigging contractor. When that happens, the manual operation system is either non-existent (so you have to climb up on the roof in a rain storm to close the hatches), or is 'user hostile' (isn't convenient for the staff to use on a day-to-day basis).

Dysfunctional mess (left). Neatly marked and operated with a RED handline (right). Sign reads: NOTICE - Smoke Vent Operation Line Inside". Sign is on both sides of hinged protective screen panel. Panel in front of line set is painted red.

Tuesday, May 12, 2009

Beam me up, Scotty!

I think this one speaks for itself . . . . Don't use homemade beam clamps!

When you do use commercial beam clamps, please install them correctly. These are reversed - the U-Bolt should be nominally parallel to the load, not tilted-in. Also notice the Bent Washer and the open S-Hook.

This is how they are supposed to be oriented:

Monday, May 11, 2009

Report it where?

Part of a Theatre Safety Program is Hazard Recognition and Reporting. There should be a clear and concise manner to report safety issues (unlike this sign, which was carefully placed in an entrance-way door, on both sides, but with none of the required information provided). Anonymous reporting should be available so that there is no fear of retribution.

Friday, May 8, 2009


The nut above may be tight, but it does not fully engage the threads on the bolt. Good practice is to always leave at least 1/2 to 1 full bolt diameter protruding from the nut. Like this:

Washers need attention, too! A washer is a device to distribute the load from the nut evenly across the bolted surface. If the surface is flat and the backing hole is just barely larger than the bolt coming through it, then a non-hardened washer may do, but if it is subject to bending or is suspending a load overhead, then the washer should be graded the same as the bolt and nut (i.e. SAE Grade 5, or 8, or ASTM 305, as determined by the engineer certifying the system).

Wednesday, May 6, 2009

Swab the decks, Matey!

Swab it with white paint, that is! And throw-on a bit of that traction grit for floors, too, while you're at it. Its primarily psychological, but walking across a white gridiron deck just makes you feel safer. Note the OSHA Hazard Warning marker tape along the loft wells, too.

Tuesday, May 5, 2009

Walking the dog

Fortunately, common sense and better engineering criteria have become more prevalent in stage rigging, however, I still find many brand-spankin'-new facilities with equipment suspended on dog chain.

Some of the stuff I see is really scary. This batten at the left is just a smidgen from falling out of the rigging. Fortunately some one put a (pot-metal) screw through the bent wire chain so it would (hopefully) stay-put.

Here we see a dog-chain wrapped around an old loft block rope sheave. It too, secured with a pot-metal bolt.

This is a good example of multiple failure points all in series:
Bolted joint (at least this one was an SAE Grade 5 Bolt).
Open ended hook (if the batten snags on something and the line goes slack, then this can disengage).
Pot-metal Turn-Buckle with closed eye at bottom, but not a one-piece forged eye (it could bend open under load).
Bent wire S-Hook connected to track (no load rating for this either).
"Dog chain" is nothing more than a piece of bent solid wire. It is not load-rated for overhead lifting or suspension of loads over peoples' heads. Only Grade 63 or Grade 8 alloy steel chain is rated for that purpose. The next time you see bent metal parts holding up your rigging, or find open eye hooks, or non-graded bolts, or pot-metal turn-buckles, you might think about getting that fixed ASAP.

Sunday, May 3, 2009

Ladders on skateboards

How many of you have one of these? Raise your hands . . . now, take them to the dumpster. You can't add casters to a ladder. I know, it makes moving that ladder a lot easier to put it on wheels. It also makes it a lot deadlier. Why do you think that ladder manufacturers DON'T sell ladders like this? Because they can't sell an obliously dangerous product.

When you modify a ladder (i.e. cut it, drill holes in it, or otherwise change it) you have absolved the manufacturer of any liability for any accidents that happen after that. It's not just about lawyers, lawsuits, and insurnace -- its about doing the right thing.
Loose the casters.