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The Coming Standards for Powered Curtain Machines

Updated: Sep 26, 2022

Jesse Adams, Rose Brand ETCP Theatre Rigging Certified Technical Project Manager, discusses the "who, what, where, when and why" of the new BSR W1.71 standard.

The multiple curtains in this production would be difficult to run manually. Automated

curtain machinery simplifies the operation.

POWERED CURTAIN MACHINES have been around for a century or more. They are used in exhibits, movie theatres, professional venues, and cafetoriums / gymnatoriums the world over! They have (mostly) worked fine for decades and require very little maintenance. Press a button and they run to their limits. Why do we need a standard for these workhorses?

As the world changes, technology and the scale of projects and installations expand. Even in the world of curtains, cues move faster, loads get heavier, and new layouts and designs are being implemented. How can we ensure these machines are being properly designed and used?

As liability continues to be a concern, we find a growing need for defining safety and documenting common practices. A written industry standard is one of the best methods for establishing these safe working practices. Standards can also help clarify the intended use of a particular piece of equipment.

BSR E1.71, Powered Curtain Machines, is a project in ESTA’s Technical Standards Program Stage Machinery Working Group to draft a standard to address one of the most common stage machines found in our industry: powered curtain machines. Currently, there are no published entertainment standards to address any machines outside of rigging equipment and orchestra pit lifts. In the realm of entertainment, there is a myriad of other machines that don’t even come close to fitting into these categories. It is important to have applicable standards for curtain machines, so they are not being compared to their second or even third cousins.

This is a draft curtain machine standard, not intended to be a scenery standard. Using a curtain machine to move hard scenery, whether traveling horizontally or flown, is outside the scope of this document. Flown scenery still falls under the requirement of ANSI E1.6-1, Entertainment Technology – Powered Hoist Systems. Horizontally moving scenery falls into the area of a planned future standard.

An Austrian curtain has horizontal and vertical fullness, and gathers toward the top batten as it is lifted.

It is important to understand the difference between the designed purpose and the actual use of the machine in the field.

In many cases, it would be cost-prohibitive and not practical to build a lift curtain machine to the requirements for a general utility hoist. However, there may be cases in which a curtain machine should conform to powered hoist standards. The separation of one from the other can be a fine line, and that is where a curtain machine standard comes into play. This draft standard attempts to define the operational parameters of these machines based on the intended curtain movement.

This document uses a risk assessment and risk reduction (RA/ RR) approach. RA levels are defined based on operational envelope, curtain design, operating speed, and method of control. Users of this standard should be able to gauge the requirements of a machine by its characteristics and then find the requirements that are applicable to its design and use.

Many curtain machines are used in remote or secluded locations such as acoustic chambers or technical spaces in which no personnel are present as the curtains are moving. The risk assessment (RA) level 1 category is written with these machines in mind. When very little risk is present, a world of options is open in machine design.

There is more freedom in both controls and mechanical design when access to the operational envelope is restricted.

RA level 2 is written to cover many common installations. These are the typical curtain machines used in most stage environments.

This category includes most schools, houses of worship, and even many production-based systems. Most travelers, projection screen/ roll drum, and many lift curtain installations are level 2. Control of these systems can be very simple because the risk is low.

Small hoists for the individual lift lines allow the curtain to be drawn up to make one or

more openings with different contours.

The machines in RA level 3 are large or special-purpose production machines. These machines have characteristics that have elevated risk. Curtains in this category may move faster, have heavier bottom pipes, or other elements that increase risk. Control requirements are increased for this category. The most notable requirement is the ability to manually stop the machine if it is activated remotely by an external control system.

RA level 4 is reserved for the most complex of machines. These machines are typically purpose-built machines that pose high risk to personnel or property. Curtain effects used in museums, themed environments, and high-risk production-based machines fall into this category. This is the only level in which safety interlocks or other special provisions may be required.

This powered curtain machines standard is intended to be used by designers, specifiers, manufacturers, and installers of curtain systems. With it, curtain users also can gain understanding and guidance in the safe use and operation of their installed equipment.

It is important to note that certain aspects of curtain systems are not covered by this standard. Common components such as track, carriers, and guide hardware are specifically excluded. These parts may be covered under future standards. While it can be argued that the track becomes a structural component of some curtain systems, they are not considered to be part of the machine.

The current draft standard only covers the machine and components directly attached to its powertrain, operating media, or components in the tension load path. On a traditional horizontal traverse track, this means that the operating media, carrier or load attachment(s) to the line, and any required pulleys would be included.

This ADC curtain machine uses a small gearmotor: powerful enough to move a curtain,

but with limited power to tear things apart.

It is important to understand the difference between the designed purpose and the actual use of the machine in the field. If a lift curtain machine is used to raise and lower a batten with lighting equipment, it is no longer considered a curtain machine and, therefore, must be considered a hoist. Additionally, just because a curtain is hung on a utility hoist does not make that hoist a curtain machine. One must consider many factors when determining the classification of equipment and apply the appropriate standards.

Users of this document will see many familiar requirements for lift curtain machines. In most cases, a powered hoist complying with the requirements of ANSI E1.6-1 would meet the requirements of a lift curtain machine, but a curtain machine is not likely to meet all the requirements of a powered hoist and should not be used as a utility hoist. Elements of ANSI E1.6-1 are used as the basis for vertical travel systems in higher risk assessment categories. These sections of the standard follow much of what is considered standard industry practice in entertainment rigging. Most of the deviations for powered curtain machines from hoist requirements are found in the controls section.

Most vertical travel curtains operate by lifting the bottom of the curtain and stacking it toward the top. Examples of these would be Austrian, Venetian, and Roman curtains. These systems usually have little or no rigidity to the panel and are almost entirely flexible. The loads on these systems are fixed and their movement is largely obvious to persons in or near the operational envelope. In most cases, these systems pose minimal risk to personnel or property. Because of this, control can be simplified.

Other vertical travel curtains operate as a straight lift. The curtain does not gather at all; the top support moves with the curtain. These systems also have fixed loads and obvious movement. Most will incorporate some type of bottom pipe or fixed weights, but the top pipe typically does not travel into direct contact with personnel or property. This reduces risk and allows most controls to be simplified.

The highest level of risk for curtain machines comes when aspects of the system are outside of the average installation. These systems may incorporate high speeds, abnormally heavy curtains, larger rigid components, or the element of surprise. Many times, these will be curtains operating in the vicinity of the unassuming public. Special provisions must be made for machines operating outside of typical conditions.

The current draft does not dive deeply into controls details beyond basic system functions. This allows designers and manufacturers the flexibility to be creative and design systems tailored to specific curtain effects. In the future, this section may even be replaced by a controls standard that is currently in development in the Stage Machinery Working Group.

The draft standard gently reminds designers and specifiers that future access is important to the design of the system. Curtain machines tend to get designed into impossible locations. Not only does this create a problem for most installers, but once the machine is in use, it may be very difficult to inspect and maintain the machine and its attached components. Manufacturers are also required to design machines in a way that allows for maintenance and inspection.

While powered curtain machines may not be the most problematic or dangerous machines in entertainment, they are certainly one of the most common. The design and use of these workhorses is almost as diverse and numerous as there are designers and fabricators to dream up and build them. The one element they have in common is their purpose: moving curtains.

Creating a standard for such an eclectic family of equipment is not an easy task. The similarities and differences between the intricacies of the most common arrangements had to be carefully examined. The task group has done its best to reconcile these varied requirements and reduce the language in the standard to the most basic of requirements. The current draft is an attempt to present the requirements without hindering design, creativity, or future development of new products. There will likely be many changes as the document is refined during the public review process. The task group is looking forward to seeing what comes next!

Jesse Adams is a Technical Projects Manager for Rose Brand. He has more than 20 years of professional experience in rigging and technical production with projects around the globe. Jesse holds an ETCP Theatre – Rigging certification and has spent the last 10 years volunteering with ESTA’s Technical Standards Program.

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