Oct 11, 2004

Designing Outside the Box

Customized valves perform all the necessary functions

In the summer of 2000, the Henry Pratt Co., (HPC) was approached by consultant Black & Veatch (B&V) concerning a unique custom valve application opportunity at the Passaic (N.J.) Valley Water Plant.In the summer of 2000, the Henry Pratt Co., (HPC) was approached by consultant Black & Veatch (B&V) concerning a unique custom valve application opportunity at the Passaic (N.J.) Valley Water Plant.
The valves installed at the time performed the function of filter influent and filter drain shutoff at the potable water plant. Due to leakage of those valves, an unacceptable amount of pre-treated water was passing back through the drain valves during the filtering operation, which over time can have a substantial economic impact on the operation of a filter plant.
The Passaic application required HPC to modify part of it’s standard product lines to suit the replacement of sixteen 24 in. by 36 in. obround shaped valves originally manufactured by another valve company.
The application also required a “melding” of key design aspects from two existing product lines to properly replace 16 existing butterfly valves.

Match game

As in many potable water treatment plants, partially treated water is conveyed to the sand and gravel filters for further processing, via rectangular shaped concrete conduits. Separate rectangular shaped concrete conduits were also used in the water plant to drain the backwash water from the filter cell during the backwash process.
The existing obround-shaped influent and drain shutoff valves in Passaic were attached to the concrete wall of these conduits by cast iron thimbles, which matched the shape of the valves. The thimbles were imbedded into the wall during the original plant construction. Additionally, both valves were submerged in the gullet of the filter cell and the drain valve was mounted underneath the influent valve.
After visiting the site, it was apparent that any replacement valves would be required to match the existing wall thimble. An additional requirement to reuse the valve shaft floor penetrations above the valves was suggested and implemented to further minimize the work required for the installing contractor.
Continued discussions with B&V yielded additional features required of the replacement valves. By incorporating the replaceable seat design of their fabricated rectangular valve into the cast iron body geometry of their AWWA butterfly product, HPC was able to meet the additional requirements. These requirements included equal or better flow capability, zero leakage, fully replaceable rubber seat and a reasonable cost to the end user.
The cast iron obround bodies would require new pattern equipment, which also added to the lead-time. Because HPC was able to spread this over 16 units, pattern cost implications were minimized.
These plant improvements, along with others, were incorporated into a contract that was ultimately awarded to Prismatic Development in late 2001. HPC received an order to provide these replacement valves from the mechanical subcontractor, Esoteric Mechanical shortly thereafter, and subject to the specifications written by the consultant.
The project schedule required an accelerated design, material procurement and production process. Measurements of the existing valves and installation were determined for the design purposes.
After submitting drawings, HPC received approval to proceed in mid-April 2002. HPC’s engineering department first concentrated on the valve body, due to lead-time issues associated with the pattern equipment. By July 2002, the first 10 valves shipped to the jobsite, ahead of the original schedule to the contractor.
By working with the customer and their consultant, HPC was able offer a non-catalog product that performed all the necessary functions required, at a tremendous cost saving over other options which could have required the removal and replacement of the cast in place obround thimbles.

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