Manhole/Handhole Replacement Guide

When it comes to boiler maintenance, one of the most commonly replaced parts is the handhole or manhole plate. These essential components ensure that your boiler operates efficiently and safely. If you’re in need of a replacement handhole or manhole, but aren’t sure where to start, Oswald Supply is here to help. With nearly a century of experience, we have the expertise to guide you through the process, no matter how much or how little information you have.

The Basics: Information You’ll Need

To narrow your search for the correct handhole plate, having some key details on hand will simplify the process. Here are the most important factors to consider:

1. Size: Measure the width and length of the handhole plate. It’s best to measure the hole in the boiler’s shell or the inside dimensions of the plate itself, avoiding the gasket.

2. Shape: The most common Handhole and manhole plates are elliptical (egg-shaped) or obround (racetrack-shaped). Less common shapes like round, diamond, or pear may require a sample or drawing for replacement.

3. Flat or Curved: Determine whether the plate is flat or curved to match the boiler shell. Curved plates may be formed on the long axis (Y-type) or short axis (Z-type), depending on the boiler type.

4. Bolt Type: Identify whether the plate uses loose or solid bolts. Loose bolts are ideal for tight spaces, while solid bolts offer stability in other installations.

5. Boiler’s Working Pressure: Boilers are classified as low, medium, or high pressure. Plates for high-pressure boilers must meet specific strength and material standards.

6. Material Make: Handhole plates are typically made of cast iron or forged steel. Cast iron is suitable for low-pressure applications, while forged steel is rated for both high- and low-pressure uses.

7. Boiler Manufacturer and Model: Knowing the boiler’s manufacturer, model number, or horsepower can be invaluable in finding the correct plate.

Measuring for Accuracy

If you’re unsure of your plate’s size, proper measurements are critical. Use a caliper to measure the inside dimensions of the plate itself, focusing on the gasket seat rather than the gasket, which may be deformed or incorrect. This ensures the plate fits perfectly with the boiler shell.

Identifying Handhole Plate Shapes

Understanding the shape of your handhole or manhole plate is essential. Elliptical plates resemble an egg, while obround plates have parallel sides like a racetrack. Oswald Supply offers custom manufacturing for less common shapes such as diamonds or pears, if you provide a sample or technical drawing.

Flat vs. Curved Plates

Curved plates are common in Scotch Marine boilers, vertical shell boilers, and pressure vessels, where the plate must align with the boiler shell's curve. Conversely, flat plates are typically used in firebox or locomotive-style boilers. To determine whether your plate is flat or curved, examine the gasket seat flange. Curved plates often appear flat on the bottom but are curved along the gasket seat.

Bolt Types and Retro-Fit Assemblies

Handhole/manhole plates use either loose or solid bolts. Loose bolts are designed for tight spaces, while solid bolts provide durability and are available with offset studs for easier installation. Oswald Supply also offers Retro-Fit Handhole Plate Assemblies, a universal solution for most applications. These assemblies include a patch ring, flat plate, gasket, and yoke, eliminating the need to carry multiple sizes and types of plates. They are available in both cast iron and forged steel, catering to low- and high-pressure applications.

Material Matters: Cast Iron vs. Forged Steel

Choosing the right material is crucial for safety and longevity. Cast iron plates are suitable for low-pressure applications, while forged steel plates handle pressures up to 1,050 PSI at 650°F, making them ideal for high-pressure boilers.

Expert Assistance Since 1923

If you’re still unsure about your handhole/manhole plate requirements, Oswald Supply’s knowledgeable team is ready to assist. Our extensive reference charts date back to 1923, allowing us to find the right plate even with limited information. Simply provide details like the boiler’s manufacturer, model number, or horsepower, and we’ll do the rest.

Contact Oswald Supply Today

For personalized assistance, contact Oswald Supply today or call us at (212) 722-7000. Our experts will help your boiler get back to optimal working conditions with the perfect handhole/manhole plate replacement.