HPP diaphragm seal · On-line pulp & paper service · 300-600 PSI MWP
Pulp & Paper Diaphragm Seal
Industry-standard flush pressure isolation for pulp and paper process connections.
The Haygor HPP provides three compact process interfaces for on-line measurement: a 1-inch flush sleeve, a 1.5-inch flush sleeve, and a 1.5-inch M44 x 1.25 threaded design. Published maximum working pressures are 300 PSI for HPP-A and HPP-B and 600 PSI for HPP-C.
- HPP-A, HPP-B, and HPP-C mounting styles
- Flush process-facing diaphragm
- 316L stainless steel or Alloy C-276
Quick answer
What is a pulp and paper diaphragm seal?
A pulp and paper diaphragm seal is a pressure-isolation assembly designed for an on-line process connection used in mill service. The process-facing diaphragm remains flush with the connection so pressure can act on a broad sensing surface, while a sealed fill fluid carries that pressure to a gauge, transmitter, switch, or controller.
The HPP family provides three published mounting geometries for new installations and replacement projects. Haygor specifically notes interchangeability with many other manufacturers' designs, but the connection, dimensions, pressure rating, gasket, materials, and instrument attachment still must be matched to the actual installation.
Hydraulic pressure transfer
How the HPP seal works
The HPP combines a flush process interface with diaphragm isolation and a filled pressure-transfer path.
- 1
The process connection is installed
The selected sleeve or M44 x 1.25 connection mates to the mill's compatible on-line mounting point.
- 2
The gasket seals the interface
Viton is published for Types A and B; Gylon 3510 is published for Type C.
- 3
Process pressure acts on the diaphragm
The flush diaphragm responds while keeping process media out of the instrument and fill passage.
- 4
Fill fluid transfers the pressure signal
The attached gauge, transmitter, switch, or controller receives the hydraulic pressure signal without direct process contact.
Application fit
On-line pressure isolation for pulp and paper process connections
Haygor publishes the HPP as an industry-standard seal for on-line pulp and paper applications. The flush interface and compact replacement geometries support measurement points where a conventional recessed pressure port may be undesirable or incompatible with the installed connection.
Where the HPP can fit
- Compatible flush sleeve process connections
- M44 x 1.25 threaded pulp and paper connections
- Direct-mounted gauges and transmitters
- Remote pressure assemblies using a compatible attachment and fill system
- Replacement projects matching established manufacturer geometries
Selection conditions to verify
- Exact HPP type or existing connection drawing
- Operating pressure, temperature, and pressure transients
- Process media, fiber content, additives, and cleaning method
- Body, diaphragm, weld-spud, and gasket compatibility
- Instrument range, fill fluid, mounting, and ambient exposure
Common mill settings
Pressure measurement throughout pulp and paper operations
- Stock preparation
- Pulp processing
- Paper machines
- Bleaching systems
- Chemical recovery
- Mill utilities
Published configuration envelope
HPP mounting styles, pressure ratings, and core materials
These selections summarize Haygor's published HPP ordering information. Confirm current availability and completed filled-system limits before release.
1-inch flush sleeve
One-bolt connection with 300 PSI published MWP.
1.5-inch flush sleeve
Two-bolt connection with 300 PSI published MWP.
M44 x 1.25 thread
1.5-inch flush threaded connection with 600 PSI published MWP.
316 / 316L stainless
Published body, diaphragm, and weld-spud material family.
Alloy C-276
Published corrosion-resistant body, diaphragm, and weld-spud option.
Six instrument connections
Weld, female NPT, male NPT, and weld-plug selections.
The 300 PSI and 600 PSI values are type-specific published maximum working pressures, not substitutes for application review. Temperature, process chemistry, gasket, mating connection, instrument, fill fluid, capillary, ambient conditions, and required accuracy can further limit the completed system.
Dimensions and ordering selection
Choose the process geometry before the instrument attachment
Start with the exact mill connection or replacement drawing. Then select the instrument connection, wetted materials, optional weld spud, gasket, surface treatment, and documentation.
1.0-inch flush sleeve
One-bolt process connection with an O-ring interface and 300 PSI published maximum working pressure.
1.5-inch flush sleeve
Two-bolt process connection with an O-ring interface and 300 PSI published maximum working pressure.
1.5-inch M44 x 1.25 thread
Flush threaded connection with 600 PSI published maximum working pressure.
The drawing callouts above reproduce the values shown in Haygor's published HPP dimensional page. Use the current controlled drawing to identify each datum, tolerance, insertion requirement, and mating-feature dimension before fabrication or replacement.
| Code | Instrument connection | Code | Instrument connection |
|---|---|---|---|
| W | Weld connection | 2 | 1/4-inch NPT |
| 4 | 1/2-inch NPT | 5 | 1/4-inch NPTM |
| 6 | 1/2-inch NPTM | 7 | 1/2-inch NPTM weld plug |
| Category | Code | Published selection |
|---|---|---|
| Body material | S6 | 316 / 316L stainless steel |
| HC | Alloy C-276 | |
| Diaphragm | S6 | 316L stainless steel |
| HC | Alloy C-276 | |
| Lower weld spud | NN | Without |
| S6 | 316 / 316L stainless steel | |
| HC | Alloy C-276 | |
| Gasket | VI | Viton - Types A and B |
| GL | Gylon 3510 - Type C | |
| Options | /HS | 316L stainless steel welding heat sink provided |
| /NS | PTFE-coated diaphragm - non-stick only, not for corrosion protection | |
| /MC | Material certification with MTRs |
Configuration sequence
Build the HPP model deliberately
- 1. Type
- A, B, or C process geometry
- 2. Instrument connection
- W, 2, 4, 5, 6, or 7
- 3. Body and diaphragm
- 316L family or Alloy C-276
- 4. Lower weld spud
- Without, 316L family, or Alloy C-276
- 5. Gasket
- Type-dependent published selection
- 6. Options
- Heat sink, non-stick coating, and/or MTRs
Information to confirm before release
- Existing seal manufacturer, model, or current mating drawing
- HPP-A, HPP-B, or HPP-C connection geometry
- Operating, maximum, and transient pressure
- Process and ambient temperature plus media composition
- Body, diaphragm, lower weld-spud, and gasket compatibility
- Instrument connection, model, range, and mounting method
- Direct mount or capillary, fill fluid, orientation, and support
- Heat sink, non-stick coating, and material-document requirements
Compare process interfaces
Related Haygor diaphragm seals
Use the HPP where the pulp and paper sleeve or M44 process geometry is required. Compare other flush or in-line designs for different piping and vessel connections.
Frequently asked questions
Pulp & Paper seal FAQ
These answers summarize Haygor's published HPP ordering information and dimensional drawings. Final selection requires review of the exact mill connection, process, filled system, and installation.
Ask Haygor a technical questionWhat is a pulp and paper diaphragm seal?
The Haygor HPP is an industry-standard diaphragm seal for on-line pulp and paper process applications. Its flush process-facing diaphragm isolates a gauge, transmitter, switch, or controller from the process while a sealed fill fluid transfers pressure to the instrument.
Which HPP process connection styles are available?
Haygor publishes three HPP types: HPP-A with a 1-inch flush sleeve and one-bolt connection, HPP-B with a 1.5-inch flush sleeve and two-bolt connection, and HPP-C with a 1.5-inch flush M44 x 1.25 threaded connection.
What are the maximum working pressures?
Haygor publishes 300 PSI maximum working pressure for HPP-A and HPP-B, and 600 PSI maximum working pressure for HPP-C. The allowable pressure of the completed assembly may be lower based on temperature, materials, gasket, mating connection, instrument, fill fluid, and installation.
Can the HPP replace another manufacturer's pulp and paper seal?
Haygor states that the HPP offers interchangeability with many other manufacturers' designs. Replacement selection still requires verification of the exact mounting style, sleeve or thread dimensions, gasket, bolt arrangement, insertion geometry, pressure rating, materials, and instrument connection.
Which instrument connections are listed for the HPP?
Published instrument-connection codes include weld, 1/4-inch NPT, 1/2-inch NPT, 1/4-inch male NPT, 1/2-inch male NPT, and a 1/2-inch male NPT weld-plug configuration. Confirm current compatibility with the selected HPP type and instrument assembly.
Which wetted materials are available?
Haygor lists 316/316L stainless steel and Alloy C-276 for the body, diaphragm, and optional lower weld spud. The diaphragm is listed as 316L stainless steel or Alloy C-276. Material selection must be based on the actual process chemistry, temperature, cleaning method, and expected service life.
Which gasket materials are published?
Haygor lists Viton for HPP-A and HPP-B and Gylon 3510 for HPP-C. Verify gasket compatibility with the process media, temperature, cleaning chemicals, and mating connection before release.
What does the PTFE-coated diaphragm option do?
Haygor identifies the /NS PTFE-coated diaphragm as a non-stick option only and explicitly states that it is not for corrosion protection. Choose the base diaphragm and body alloy for corrosion compatibility.
What information should I provide for an HPP quote?
Provide the existing seal manufacturer and model or the mating drawing, HPP type or connection geometry, process media and concentration, operating and maximum pressure, process and ambient temperature, instrument model and range, mounting method, body and diaphragm material, lower weld-spud requirement, gasket, fill-fluid constraints, and documentation requirements.
Move from mill connection to an HPP configuration
Configure a Pulp & Paper seal or send the complete replacement application to Haygor.
Use the configurator for a guided starting point, or request a quote with the existing model or mating drawing, connection type, pressure, temperature, process media, materials, gasket, instrument, fill system, and documentation requirements.