APF High Temperature Service Inspection Plugs

APF High Temperature Service Inspection Plugs

Temp Range: 33 to 1,000 °F / 33 to 1,200 °F. Most Reliable and Insulation Efficient Inspection Port on the Market

High Temperature Service

These high quality, high temperature plugs come in two versions: HT1, designed for a temperature range of 33 to 1,000 °F (1 – 537 °C), and HT2 with a temperature range of 33 to 1,200 °F (1 – 648 °C). Access Plug Flange inspection ports are designed with the largest sealing area in the industry to provide the most reliable and insulation efficient inspection port on the market today. Installation is quick and safe because they attach to the jacketing surface and not to the cut edge, providing a multitude of benefits. By using an inspection port within the listed operating temperatures, if the insulation material inserted after installation is lost or discarded, the integrity of the system is protected.


HT1 Plug

HT2 Plug


  • Designed for high-temperature applications but can be used at any temperature range above freezing where you want the security of an interlocking cup
  • A hole saw is NOT required for installation, this prevents possible damage to the base metal from the hole saw pilot bit or accidental damage to hidden trace lines
  • The inspector is shielded from the cut edge of the jacketing by the center draw of the flange, this allows you to comply with OSHA safety requirements
  • Silicone applied under the flange is what provides the primary holding and sealing capabilities for the flange to the jacketing surface
  • The elasticity of the large volume of silicone under the flange is what helps maintain the airtight and watertight seal during any thermal expansion or contraction of the jacketing material
  • When installed per manufactures recommendation, a permanent airtight and watertight seal will be achieved
  • 1/2" banding slots are provided in the flange to allow the inspection port to be banded in place when required
  • Based on the application needed, all flat flanges can be field contoured to conform to a smaller radius
  • Outer seal is made using a high-temperature o-ring for a weather-tight seal
  • Only Available in aluminum material and a 2 1/2" diameter
  • Optional Separation Sleeve for material separation is available

HT1 Plug

  • Designed with an inner seal that is a metal to metal radiant barrier that helps prevent against heat loss thru the inspection port
  • The deep draw of the metal cup is designed to provide efficient ambient cooling by dissipating any heat load to protect the outer o-ring seal

HT2 Plug

  • Designed to have a customer supplied insulation coupon attached to the center pin for a permanent solution against insulation loss during inspection
  • The metal cup is designed to provide efficient ambient cooling to dissipate any absorbed heat to protect the inspector

Access Plug Flange Benefits

  • Stainless steel safety line with molded-in washer for strain relief to protect against plug loss
  • One-handed removal of the silicone plug with the aid of the molded seal braking tab
  • Extension tube, for cryogenic services, to protect against air migration under insulation
  • Optional extension sleeve is available to help with insulation separation from testing area
  • Offers a wide range of inspection ports to allow you to match your inspection ports to your process temperature
  • No Hot Work Permit needed, meaning less installation costs, less risk of damage and installation can be performed while the unit is in production
  • Protection against packeting expansion / contracting


Access Plug Flange Application & Industries

Access Plug Flange's product offerings are used in many different industries ranging from petrochemical and refining to food processing and pharmaceutical. Their extensive product offerings and large global installed base in these various industries demonstrate their customers' confidence in choosing Access Plug Flange products. Industries include:

  • Petrochemical
  • Refining
  • Pulp and Paper
  • Food Processing
  • Pharmaceutical
  • Chemical

Standard Installation Instructions



Installation consists of six steps with exceptions to the optional field contour, extension sleeve, and transition gasket. Also, cryogenic inspection port follows a different installation procedure for the flange installation as shown below the standard installation procedures.



Step 1

Using the flange for sizing, locate and mark the ID of the flange on the jacketing surface at the test point location.

Step 2

Using a sharp utility knife or similar device, score the jacketing along the traced outline and pierce the jacketing with a small hole for the snips.

Step 3

Use a pair of snips to remove the jacketing. ** NOTE ** If you wish to use a hole saw to remove the jacketing, please refer to the chart below for sizing.

Step 4

Using the correct tool for your specific insulation material, remove the insulation as required to expose the pipe/vessel surface.

Step 4.1: Perform the following options prior to next step if applicable:

- Field Contour the flange for small diameter piping if needed

- Install the Separation Sleeve at this step if needed

- Install the Transition Gasket if needed

Step 5

Fill the backside of flange with a high grade silicone adhesive and insert the flange into the cut hole to shield the cut edge

Use the silicone injection holes along the face of the flange to fill any voids and to make sure you have an airtight seal between the flange and the jacketing

Step 6

Install two (2) #10 self-tapping stainless steel screws across from each other to hold the flange in place while the silicone cures. Make sure one of the screws is used to attach the safety line to the flange.

**NOTE: Installers may want to use aluminum or stainless steel pop rivets in lieu of self-tapping screws as an alternate fastening method. Insert an insulation core into the inspection hole and secure the stopper in the flange. If you are installing our high temperature, all metal, inspection ports; make sure the cup in fully engaged with the locking tabs to create the seal.

Hole Saw Sizing Chart

APF ID (in) Hole/Drill Dia. (in)
1 3/4" 1 9/16"
2 1/2" 2 9/16"
4" 4 1/8"
5" 5"

Note: There is a $25 small order fee for orders under $100

Description Part # Saved Price Select Option Add to
Access Plug Flange 2 1/2" Heat Check Assembly (HT-1), Aluminum Flat Flange, Deep Draw Aluminum Cup w/Copper Sleeve. Temp Range: 33-1,000 °F CUI-APF-2143001 $12.00
Access Plug Flange 2 1/2" Heat Check Assembly (HT-2), Aluminum Flat Flange, Shallow Draw Aluminum Cup w/Copper Sleeve, Stainless Steel Pin & Washers. Temp Range: 33-1,200 °F CUI-APF-3153002 $14.00
Access Plug Flange 2 1/2" Aerogel Assembly (AG-1), Aluminum Flat Flange, Shallow Draw Aluminum Cup w/Copper Sleeve. Temp Range: 33-1,000 °F CUI-APF-4163003 $12.00