Perspectives: Process Puzzler

Get Relief From Valve Popping

Readers suggest ways to address thermal expansion issue.

*THIS MONTH’S PUZZLER* We’re suffering an annoying thermal expansion problem in the ethylene oxide (EO) lines that feed our reactors: pressure relief valves (PRVs) often pop from solar heating, because lines are blocked in, typically for up to ten minutes. (Our design standard assumes horizontal pipe and a maximum ambient temperature of 95°F, which doesn’t occur very often at our Chicago site: solar flux is 38.7 Btu/h-ft2 for the summer solstice.) The PRVs wouldn’t be such a problem but EO can polymerize and cause them to stick open, which is why the covered area under the reactors is Class 1, Division 1, Group B. The EO feed pipe runs at 55 psig at 60°F. The PRVs are set at 145 psig. Barometric pressure is 14.408 psia. The properties of EO at operating conditions are: density, 66.8 lb/ft3; viscosity, 0.302 cP; heat capacity, 0.476 BTU/lb-F; thermal conductivity, 0.0949 BTU/h-ft2-°R; volumetric thermal expansion coefficient, 0.001°F-1; and bulk modulus, 180,000 psi/ft3. Our plant engineer is convinced that two inches of calcium silicate insulation in a stainless steel jacket over our 1½-in. Schedule-80 Type-316 stainless-steel pipe largely will eliminate our PRV reliability problem. What do you think?

Read more

More from this perspective...

Title

Process Puzzler Question: Lengthen media life and reduce operating costs in a pressure filter

Our pressure filter suffers from excessive cake build-up. Although some caking is necessary for efficient filtering, it would be desirable to extend the running time. What do you suggest? Also, do you have any ideas on how we can lengthen media life or reduce operating costs?

06/16/2008

Process Puzzler: Avoid Another Fatal Accident

Readers consider the causes of a deadly fire.

06/19/2009

Process Puzzler: Choose a pump wisely

Readers offer tips about how to choose the best pump for slurry service.

05/25/2005

Process Puzzler: Combat Column Contamination

Readers suggest how to tackle a troublesome tower.

12/15/2009

Process Puzzler: Confront Column Constraints

Upgrading an atmospheric tower may require operational and design changes.

05/20/2014

Process Puzzler: Deal with a Decanter that Can't

Readers recommend ways to save a standing separator.

10/14/2010

Process Puzzler: Deal with dryer drizzle

Readers suggest ways to solve a spray interference problem

06/16/2008

Process Puzzler: Eliminate Evaporator Effect

Readers solve an evaporation pump problem.

05/21/2009

Process Puzzler: Fix a Fluid Flow Flaw

Readers suggest solutions for dryer difficulties.

09/15/2009

Process Puzzler: Fix a Fluidized Bed

Addressing the problems may mandate multiple measures.

04/02/2014

Process Puzzler: Go With Agglomeration

Safely reprocessing flammable polymer dust demands a number of measures.

06/27/2013

Process Puzzler: Guard Against Gas

Readers suggest the source of a safety stumper.

11/10/2009

Process Puzzler: Kayo a Cascade Control Complication

Readers suggest how to properly regulate an exothermic reaction.

04/24/2009

Process Puzzler: Keep Incineration Safe

Readers suggest how to deal with a cyanide-containing fuel.

01/25/2010

Process Puzzler: Keep cables in their place

A Chemical Processing reader was looking for a solution to a cable hanger problem. At his plant, a 200-lb. cable bundle supported by cable hangers fell and injured one man. Read what advice our readers had for him and take a look at next months' question.

02/21/2005

Process Puzzler: Look Beyond The Valve

Other factors can contribute to persistent valve leaks.

01/14/2011

Process Puzzler: Make Solid Progress

Readers suggest ways to improve crystallizer controls.

06/16/2010

Process Puzzler: Master a Musty Mess

Readers suggest how to deal with a contamination source.

08/13/2009

Process Puzzler: Preempt Pump Problems

Readers suggest several options to improve reliability

02/01/2013

Process Puzzler: Put Railcar Loading Back on Track

Readers suggest how to stop serious safety snags.

04/21/2010